1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2015 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2015 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2015 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
545 @chapter A Sample @value{GDBN} Session
547 You can use this manual at your leisure to read all about @value{GDBN}.
548 However, a handful of commands are enough to get started using the
549 debugger. This chapter illustrates those commands.
552 In this sample session, we emphasize user input like this: @b{input},
553 to make it easier to pick out from the surrounding output.
556 @c FIXME: this example may not be appropriate for some configs, where
557 @c FIXME...primary interest is in remote use.
559 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
560 processor) exhibits the following bug: sometimes, when we change its
561 quote strings from the default, the commands used to capture one macro
562 definition within another stop working. In the following short @code{m4}
563 session, we define a macro @code{foo} which expands to @code{0000}; we
564 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
565 same thing. However, when we change the open quote string to
566 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
567 procedure fails to define a new synonym @code{baz}:
576 @b{define(bar,defn(`foo'))}
580 @b{changequote(<QUOTE>,<UNQUOTE>)}
582 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
585 m4: End of input: 0: fatal error: EOF in string
589 Let us use @value{GDBN} to try to see what is going on.
592 $ @b{@value{GDBP} m4}
593 @c FIXME: this falsifies the exact text played out, to permit smallbook
594 @c FIXME... format to come out better.
595 @value{GDBN} is free software and you are welcome to distribute copies
596 of it under certain conditions; type "show copying" to see
598 There is absolutely no warranty for @value{GDBN}; type "show warranty"
601 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
606 @value{GDBN} reads only enough symbol data to know where to find the
607 rest when needed; as a result, the first prompt comes up very quickly.
608 We now tell @value{GDBN} to use a narrower display width than usual, so
609 that examples fit in this manual.
612 (@value{GDBP}) @b{set width 70}
616 We need to see how the @code{m4} built-in @code{changequote} works.
617 Having looked at the source, we know the relevant subroutine is
618 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
619 @code{break} command.
622 (@value{GDBP}) @b{break m4_changequote}
623 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
627 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
628 control; as long as control does not reach the @code{m4_changequote}
629 subroutine, the program runs as usual:
632 (@value{GDBP}) @b{run}
633 Starting program: /work/Editorial/gdb/gnu/m4/m4
641 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
642 suspends execution of @code{m4}, displaying information about the
643 context where it stops.
646 @b{changequote(<QUOTE>,<UNQUOTE>)}
648 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
650 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
654 Now we use the command @code{n} (@code{next}) to advance execution to
655 the next line of the current function.
659 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
664 @code{set_quotes} looks like a promising subroutine. We can go into it
665 by using the command @code{s} (@code{step}) instead of @code{next}.
666 @code{step} goes to the next line to be executed in @emph{any}
667 subroutine, so it steps into @code{set_quotes}.
671 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
673 530 if (lquote != def_lquote)
677 The display that shows the subroutine where @code{m4} is now
678 suspended (and its arguments) is called a stack frame display. It
679 shows a summary of the stack. We can use the @code{backtrace}
680 command (which can also be spelled @code{bt}), to see where we are
681 in the stack as a whole: the @code{backtrace} command displays a
682 stack frame for each active subroutine.
685 (@value{GDBP}) @b{bt}
686 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
688 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
690 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
691 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
693 #4 0x79dc in expand_input () at macro.c:40
694 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
698 We step through a few more lines to see what happens. The first two
699 times, we can use @samp{s}; the next two times we use @code{n} to avoid
700 falling into the @code{xstrdup} subroutine.
704 0x3b5c 532 if (rquote != def_rquote)
706 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
707 def_lquote : xstrdup(lq);
709 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
712 538 len_lquote = strlen(rquote);
716 The last line displayed looks a little odd; we can examine the variables
717 @code{lquote} and @code{rquote} to see if they are in fact the new left
718 and right quotes we specified. We use the command @code{p}
719 (@code{print}) to see their values.
722 (@value{GDBP}) @b{p lquote}
723 $1 = 0x35d40 "<QUOTE>"
724 (@value{GDBP}) @b{p rquote}
725 $2 = 0x35d50 "<UNQUOTE>"
729 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
730 To look at some context, we can display ten lines of source
731 surrounding the current line with the @code{l} (@code{list}) command.
737 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
739 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
742 538 len_lquote = strlen(rquote);
743 539 len_rquote = strlen(lquote);
750 Let us step past the two lines that set @code{len_lquote} and
751 @code{len_rquote}, and then examine the values of those variables.
755 539 len_rquote = strlen(lquote);
758 (@value{GDBP}) @b{p len_lquote}
760 (@value{GDBP}) @b{p len_rquote}
765 That certainly looks wrong, assuming @code{len_lquote} and
766 @code{len_rquote} are meant to be the lengths of @code{lquote} and
767 @code{rquote} respectively. We can set them to better values using
768 the @code{p} command, since it can print the value of
769 any expression---and that expression can include subroutine calls and
773 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
775 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
780 Is that enough to fix the problem of using the new quotes with the
781 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
782 executing with the @code{c} (@code{continue}) command, and then try the
783 example that caused trouble initially:
789 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
796 Success! The new quotes now work just as well as the default ones. The
797 problem seems to have been just the two typos defining the wrong
798 lengths. We allow @code{m4} exit by giving it an EOF as input:
802 Program exited normally.
806 The message @samp{Program exited normally.} is from @value{GDBN}; it
807 indicates @code{m4} has finished executing. We can end our @value{GDBN}
808 session with the @value{GDBN} @code{quit} command.
811 (@value{GDBP}) @b{quit}
815 @chapter Getting In and Out of @value{GDBN}
817 This chapter discusses how to start @value{GDBN}, and how to get out of it.
821 type @samp{@value{GDBP}} to start @value{GDBN}.
823 type @kbd{quit} or @kbd{Ctrl-d} to exit.
827 * Invoking GDB:: How to start @value{GDBN}
828 * Quitting GDB:: How to quit @value{GDBN}
829 * Shell Commands:: How to use shell commands inside @value{GDBN}
830 * Logging Output:: How to log @value{GDBN}'s output to a file
834 @section Invoking @value{GDBN}
836 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
837 @value{GDBN} reads commands from the terminal until you tell it to exit.
839 You can also run @code{@value{GDBP}} with a variety of arguments and options,
840 to specify more of your debugging environment at the outset.
842 The command-line options described here are designed
843 to cover a variety of situations; in some environments, some of these
844 options may effectively be unavailable.
846 The most usual way to start @value{GDBN} is with one argument,
847 specifying an executable program:
850 @value{GDBP} @var{program}
854 You can also start with both an executable program and a core file
858 @value{GDBP} @var{program} @var{core}
861 You can, instead, specify a process ID as a second argument, if you want
862 to debug a running process:
865 @value{GDBP} @var{program} 1234
869 would attach @value{GDBN} to process @code{1234} (unless you also have a file
870 named @file{1234}; @value{GDBN} does check for a core file first).
872 Taking advantage of the second command-line argument requires a fairly
873 complete operating system; when you use @value{GDBN} as a remote
874 debugger attached to a bare board, there may not be any notion of
875 ``process'', and there is often no way to get a core dump. @value{GDBN}
876 will warn you if it is unable to attach or to read core dumps.
878 You can optionally have @code{@value{GDBP}} pass any arguments after the
879 executable file to the inferior using @code{--args}. This option stops
882 @value{GDBP} --args gcc -O2 -c foo.c
884 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
885 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
887 You can run @code{@value{GDBP}} without printing the front material, which describes
888 @value{GDBN}'s non-warranty, by specifying @code{--silent}
889 (or @code{-q}/@code{--quiet}):
892 @value{GDBP} --silent
896 You can further control how @value{GDBN} starts up by using command-line
897 options. @value{GDBN} itself can remind you of the options available.
907 to display all available options and briefly describe their use
908 (@samp{@value{GDBP} -h} is a shorter equivalent).
910 All options and command line arguments you give are processed
911 in sequential order. The order makes a difference when the
912 @samp{-x} option is used.
916 * File Options:: Choosing files
917 * Mode Options:: Choosing modes
918 * Startup:: What @value{GDBN} does during startup
922 @subsection Choosing Files
924 When @value{GDBN} starts, it reads any arguments other than options as
925 specifying an executable file and core file (or process ID). This is
926 the same as if the arguments were specified by the @samp{-se} and
927 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
928 first argument that does not have an associated option flag as
929 equivalent to the @samp{-se} option followed by that argument; and the
930 second argument that does not have an associated option flag, if any, as
931 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
932 If the second argument begins with a decimal digit, @value{GDBN} will
933 first attempt to attach to it as a process, and if that fails, attempt
934 to open it as a corefile. If you have a corefile whose name begins with
935 a digit, you can prevent @value{GDBN} from treating it as a pid by
936 prefixing it with @file{./}, e.g.@: @file{./12345}.
938 If @value{GDBN} has not been configured to included core file support,
939 such as for most embedded targets, then it will complain about a second
940 argument and ignore it.
942 Many options have both long and short forms; both are shown in the
943 following list. @value{GDBN} also recognizes the long forms if you truncate
944 them, so long as enough of the option is present to be unambiguous.
945 (If you prefer, you can flag option arguments with @samp{--} rather
946 than @samp{-}, though we illustrate the more usual convention.)
948 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
949 @c way, both those who look for -foo and --foo in the index, will find
953 @item -symbols @var{file}
955 @cindex @code{--symbols}
957 Read symbol table from file @var{file}.
959 @item -exec @var{file}
961 @cindex @code{--exec}
963 Use file @var{file} as the executable file to execute when appropriate,
964 and for examining pure data in conjunction with a core dump.
968 Read symbol table from file @var{file} and use it as the executable
971 @item -core @var{file}
973 @cindex @code{--core}
975 Use file @var{file} as a core dump to examine.
977 @item -pid @var{number}
978 @itemx -p @var{number}
981 Connect to process ID @var{number}, as with the @code{attach} command.
983 @item -command @var{file}
985 @cindex @code{--command}
987 Execute commands from file @var{file}. The contents of this file is
988 evaluated exactly as the @code{source} command would.
989 @xref{Command Files,, Command files}.
991 @item -eval-command @var{command}
992 @itemx -ex @var{command}
993 @cindex @code{--eval-command}
995 Execute a single @value{GDBN} command.
997 This option may be used multiple times to call multiple commands. It may
998 also be interleaved with @samp{-command} as required.
1001 @value{GDBP} -ex 'target sim' -ex 'load' \
1002 -x setbreakpoints -ex 'run' a.out
1005 @item -init-command @var{file}
1006 @itemx -ix @var{file}
1007 @cindex @code{--init-command}
1009 Execute commands from file @var{file} before loading the inferior (but
1010 after loading gdbinit files).
1013 @item -init-eval-command @var{command}
1014 @itemx -iex @var{command}
1015 @cindex @code{--init-eval-command}
1017 Execute a single @value{GDBN} command before loading the inferior (but
1018 after loading gdbinit files).
1021 @item -directory @var{directory}
1022 @itemx -d @var{directory}
1023 @cindex @code{--directory}
1025 Add @var{directory} to the path to search for source and script files.
1029 @cindex @code{--readnow}
1031 Read each symbol file's entire symbol table immediately, rather than
1032 the default, which is to read it incrementally as it is needed.
1033 This makes startup slower, but makes future operations faster.
1038 @subsection Choosing Modes
1040 You can run @value{GDBN} in various alternative modes---for example, in
1041 batch mode or quiet mode.
1049 Do not execute commands found in any initialization file.
1050 There are three init files, loaded in the following order:
1053 @item @file{system.gdbinit}
1054 This is the system-wide init file.
1055 Its location is specified with the @code{--with-system-gdbinit}
1056 configure option (@pxref{System-wide configuration}).
1057 It is loaded first when @value{GDBN} starts, before command line options
1058 have been processed.
1059 @item @file{~/.gdbinit}
1060 This is the init file in your home directory.
1061 It is loaded next, after @file{system.gdbinit}, and before
1062 command options have been processed.
1063 @item @file{./.gdbinit}
1064 This is the init file in the current directory.
1065 It is loaded last, after command line options other than @code{-x} and
1066 @code{-ex} have been processed. Command line options @code{-x} and
1067 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1070 For further documentation on startup processing, @xref{Startup}.
1071 For documentation on how to write command files,
1072 @xref{Command Files,,Command Files}.
1077 Do not execute commands found in @file{~/.gdbinit}, the init file
1078 in your home directory.
1084 @cindex @code{--quiet}
1085 @cindex @code{--silent}
1087 ``Quiet''. Do not print the introductory and copyright messages. These
1088 messages are also suppressed in batch mode.
1091 @cindex @code{--batch}
1092 Run in batch mode. Exit with status @code{0} after processing all the
1093 command files specified with @samp{-x} (and all commands from
1094 initialization files, if not inhibited with @samp{-n}). Exit with
1095 nonzero status if an error occurs in executing the @value{GDBN} commands
1096 in the command files. Batch mode also disables pagination, sets unlimited
1097 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1098 off} were in effect (@pxref{Messages/Warnings}).
1100 Batch mode may be useful for running @value{GDBN} as a filter, for
1101 example to download and run a program on another computer; in order to
1102 make this more useful, the message
1105 Program exited normally.
1109 (which is ordinarily issued whenever a program running under
1110 @value{GDBN} control terminates) is not issued when running in batch
1114 @cindex @code{--batch-silent}
1115 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1116 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1117 unaffected). This is much quieter than @samp{-silent} and would be useless
1118 for an interactive session.
1120 This is particularly useful when using targets that give @samp{Loading section}
1121 messages, for example.
1123 Note that targets that give their output via @value{GDBN}, as opposed to
1124 writing directly to @code{stdout}, will also be made silent.
1126 @item -return-child-result
1127 @cindex @code{--return-child-result}
1128 The return code from @value{GDBN} will be the return code from the child
1129 process (the process being debugged), with the following exceptions:
1133 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1134 internal error. In this case the exit code is the same as it would have been
1135 without @samp{-return-child-result}.
1137 The user quits with an explicit value. E.g., @samp{quit 1}.
1139 The child process never runs, or is not allowed to terminate, in which case
1140 the exit code will be -1.
1143 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1144 when @value{GDBN} is being used as a remote program loader or simulator
1149 @cindex @code{--nowindows}
1151 ``No windows''. If @value{GDBN} comes with a graphical user interface
1152 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1153 interface. If no GUI is available, this option has no effect.
1157 @cindex @code{--windows}
1159 If @value{GDBN} includes a GUI, then this option requires it to be
1162 @item -cd @var{directory}
1164 Run @value{GDBN} using @var{directory} as its working directory,
1165 instead of the current directory.
1167 @item -data-directory @var{directory}
1168 @itemx -D @var{directory}
1169 @cindex @code{--data-directory}
1171 Run @value{GDBN} using @var{directory} as its data directory.
1172 The data directory is where @value{GDBN} searches for its
1173 auxiliary files. @xref{Data Files}.
1177 @cindex @code{--fullname}
1179 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1180 subprocess. It tells @value{GDBN} to output the full file name and line
1181 number in a standard, recognizable fashion each time a stack frame is
1182 displayed (which includes each time your program stops). This
1183 recognizable format looks like two @samp{\032} characters, followed by
1184 the file name, line number and character position separated by colons,
1185 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1186 @samp{\032} characters as a signal to display the source code for the
1189 @item -annotate @var{level}
1190 @cindex @code{--annotate}
1191 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1192 effect is identical to using @samp{set annotate @var{level}}
1193 (@pxref{Annotations}). The annotation @var{level} controls how much
1194 information @value{GDBN} prints together with its prompt, values of
1195 expressions, source lines, and other types of output. Level 0 is the
1196 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1197 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1198 that control @value{GDBN}, and level 2 has been deprecated.
1200 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1204 @cindex @code{--args}
1205 Change interpretation of command line so that arguments following the
1206 executable file are passed as command line arguments to the inferior.
1207 This option stops option processing.
1209 @item -baud @var{bps}
1211 @cindex @code{--baud}
1213 Set the line speed (baud rate or bits per second) of any serial
1214 interface used by @value{GDBN} for remote debugging.
1216 @item -l @var{timeout}
1218 Set the timeout (in seconds) of any communication used by @value{GDBN}
1219 for remote debugging.
1221 @item -tty @var{device}
1222 @itemx -t @var{device}
1223 @cindex @code{--tty}
1225 Run using @var{device} for your program's standard input and output.
1226 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1228 @c resolve the situation of these eventually
1230 @cindex @code{--tui}
1231 Activate the @dfn{Text User Interface} when starting. The Text User
1232 Interface manages several text windows on the terminal, showing
1233 source, assembly, registers and @value{GDBN} command outputs
1234 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1235 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1236 Using @value{GDBN} under @sc{gnu} Emacs}).
1238 @item -interpreter @var{interp}
1239 @cindex @code{--interpreter}
1240 Use the interpreter @var{interp} for interface with the controlling
1241 program or device. This option is meant to be set by programs which
1242 communicate with @value{GDBN} using it as a back end.
1243 @xref{Interpreters, , Command Interpreters}.
1245 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1246 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1247 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1248 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1249 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1250 @sc{gdb/mi} interfaces are no longer supported.
1253 @cindex @code{--write}
1254 Open the executable and core files for both reading and writing. This
1255 is equivalent to the @samp{set write on} command inside @value{GDBN}
1259 @cindex @code{--statistics}
1260 This option causes @value{GDBN} to print statistics about time and
1261 memory usage after it completes each command and returns to the prompt.
1264 @cindex @code{--version}
1265 This option causes @value{GDBN} to print its version number and
1266 no-warranty blurb, and exit.
1268 @item -configuration
1269 @cindex @code{--configuration}
1270 This option causes @value{GDBN} to print details about its build-time
1271 configuration parameters, and then exit. These details can be
1272 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1277 @subsection What @value{GDBN} Does During Startup
1278 @cindex @value{GDBN} startup
1280 Here's the description of what @value{GDBN} does during session startup:
1284 Sets up the command interpreter as specified by the command line
1285 (@pxref{Mode Options, interpreter}).
1289 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1290 used when building @value{GDBN}; @pxref{System-wide configuration,
1291 ,System-wide configuration and settings}) and executes all the commands in
1294 @anchor{Home Directory Init File}
1296 Reads the init file (if any) in your home directory@footnote{On
1297 DOS/Windows systems, the home directory is the one pointed to by the
1298 @code{HOME} environment variable.} and executes all the commands in
1301 @anchor{Option -init-eval-command}
1303 Executes commands and command files specified by the @samp{-iex} and
1304 @samp{-ix} options in their specified order. Usually you should use the
1305 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1306 settings before @value{GDBN} init files get executed and before inferior
1310 Processes command line options and operands.
1312 @anchor{Init File in the Current Directory during Startup}
1314 Reads and executes the commands from init file (if any) in the current
1315 working directory as long as @samp{set auto-load local-gdbinit} is set to
1316 @samp{on} (@pxref{Init File in the Current Directory}).
1317 This is only done if the current directory is
1318 different from your home directory. Thus, you can have more than one
1319 init file, one generic in your home directory, and another, specific
1320 to the program you are debugging, in the directory where you invoke
1324 If the command line specified a program to debug, or a process to
1325 attach to, or a core file, @value{GDBN} loads any auto-loaded
1326 scripts provided for the program or for its loaded shared libraries.
1327 @xref{Auto-loading}.
1329 If you wish to disable the auto-loading during startup,
1330 you must do something like the following:
1333 $ gdb -iex "set auto-load python-scripts off" myprogram
1336 Option @samp{-ex} does not work because the auto-loading is then turned
1340 Executes commands and command files specified by the @samp{-ex} and
1341 @samp{-x} options in their specified order. @xref{Command Files}, for
1342 more details about @value{GDBN} command files.
1345 Reads the command history recorded in the @dfn{history file}.
1346 @xref{Command History}, for more details about the command history and the
1347 files where @value{GDBN} records it.
1350 Init files use the same syntax as @dfn{command files} (@pxref{Command
1351 Files}) and are processed by @value{GDBN} in the same way. The init
1352 file in your home directory can set options (such as @samp{set
1353 complaints}) that affect subsequent processing of command line options
1354 and operands. Init files are not executed if you use the @samp{-nx}
1355 option (@pxref{Mode Options, ,Choosing Modes}).
1357 To display the list of init files loaded by gdb at startup, you
1358 can use @kbd{gdb --help}.
1360 @cindex init file name
1361 @cindex @file{.gdbinit}
1362 @cindex @file{gdb.ini}
1363 The @value{GDBN} init files are normally called @file{.gdbinit}.
1364 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1365 the limitations of file names imposed by DOS filesystems. The Windows
1366 port of @value{GDBN} uses the standard name, but if it finds a
1367 @file{gdb.ini} file in your home directory, it warns you about that
1368 and suggests to rename the file to the standard name.
1372 @section Quitting @value{GDBN}
1373 @cindex exiting @value{GDBN}
1374 @cindex leaving @value{GDBN}
1377 @kindex quit @r{[}@var{expression}@r{]}
1378 @kindex q @r{(@code{quit})}
1379 @item quit @r{[}@var{expression}@r{]}
1381 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1382 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1383 do not supply @var{expression}, @value{GDBN} will terminate normally;
1384 otherwise it will terminate using the result of @var{expression} as the
1389 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1390 terminates the action of any @value{GDBN} command that is in progress and
1391 returns to @value{GDBN} command level. It is safe to type the interrupt
1392 character at any time because @value{GDBN} does not allow it to take effect
1393 until a time when it is safe.
1395 If you have been using @value{GDBN} to control an attached process or
1396 device, you can release it with the @code{detach} command
1397 (@pxref{Attach, ,Debugging an Already-running Process}).
1399 @node Shell Commands
1400 @section Shell Commands
1402 If you need to execute occasional shell commands during your
1403 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1404 just use the @code{shell} command.
1409 @cindex shell escape
1410 @item shell @var{command-string}
1411 @itemx !@var{command-string}
1412 Invoke a standard shell to execute @var{command-string}.
1413 Note that no space is needed between @code{!} and @var{command-string}.
1414 If it exists, the environment variable @code{SHELL} determines which
1415 shell to run. Otherwise @value{GDBN} uses the default shell
1416 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1419 The utility @code{make} is often needed in development environments.
1420 You do not have to use the @code{shell} command for this purpose in
1425 @cindex calling make
1426 @item make @var{make-args}
1427 Execute the @code{make} program with the specified
1428 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1431 @node Logging Output
1432 @section Logging Output
1433 @cindex logging @value{GDBN} output
1434 @cindex save @value{GDBN} output to a file
1436 You may want to save the output of @value{GDBN} commands to a file.
1437 There are several commands to control @value{GDBN}'s logging.
1441 @item set logging on
1443 @item set logging off
1445 @cindex logging file name
1446 @item set logging file @var{file}
1447 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1448 @item set logging overwrite [on|off]
1449 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1450 you want @code{set logging on} to overwrite the logfile instead.
1451 @item set logging redirect [on|off]
1452 By default, @value{GDBN} output will go to both the terminal and the logfile.
1453 Set @code{redirect} if you want output to go only to the log file.
1454 @kindex show logging
1456 Show the current values of the logging settings.
1460 @chapter @value{GDBN} Commands
1462 You can abbreviate a @value{GDBN} command to the first few letters of the command
1463 name, if that abbreviation is unambiguous; and you can repeat certain
1464 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1465 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1466 show you the alternatives available, if there is more than one possibility).
1469 * Command Syntax:: How to give commands to @value{GDBN}
1470 * Completion:: Command completion
1471 * Help:: How to ask @value{GDBN} for help
1474 @node Command Syntax
1475 @section Command Syntax
1477 A @value{GDBN} command is a single line of input. There is no limit on
1478 how long it can be. It starts with a command name, which is followed by
1479 arguments whose meaning depends on the command name. For example, the
1480 command @code{step} accepts an argument which is the number of times to
1481 step, as in @samp{step 5}. You can also use the @code{step} command
1482 with no arguments. Some commands do not allow any arguments.
1484 @cindex abbreviation
1485 @value{GDBN} command names may always be truncated if that abbreviation is
1486 unambiguous. Other possible command abbreviations are listed in the
1487 documentation for individual commands. In some cases, even ambiguous
1488 abbreviations are allowed; for example, @code{s} is specially defined as
1489 equivalent to @code{step} even though there are other commands whose
1490 names start with @code{s}. You can test abbreviations by using them as
1491 arguments to the @code{help} command.
1493 @cindex repeating commands
1494 @kindex RET @r{(repeat last command)}
1495 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1496 repeat the previous command. Certain commands (for example, @code{run})
1497 will not repeat this way; these are commands whose unintentional
1498 repetition might cause trouble and which you are unlikely to want to
1499 repeat. User-defined commands can disable this feature; see
1500 @ref{Define, dont-repeat}.
1502 The @code{list} and @code{x} commands, when you repeat them with
1503 @key{RET}, construct new arguments rather than repeating
1504 exactly as typed. This permits easy scanning of source or memory.
1506 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1507 output, in a way similar to the common utility @code{more}
1508 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1509 @key{RET} too many in this situation, @value{GDBN} disables command
1510 repetition after any command that generates this sort of display.
1512 @kindex # @r{(a comment)}
1514 Any text from a @kbd{#} to the end of the line is a comment; it does
1515 nothing. This is useful mainly in command files (@pxref{Command
1516 Files,,Command Files}).
1518 @cindex repeating command sequences
1519 @kindex Ctrl-o @r{(operate-and-get-next)}
1520 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1521 commands. This command accepts the current line, like @key{RET}, and
1522 then fetches the next line relative to the current line from the history
1526 @section Command Completion
1529 @cindex word completion
1530 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1531 only one possibility; it can also show you what the valid possibilities
1532 are for the next word in a command, at any time. This works for @value{GDBN}
1533 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1535 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1536 of a word. If there is only one possibility, @value{GDBN} fills in the
1537 word, and waits for you to finish the command (or press @key{RET} to
1538 enter it). For example, if you type
1540 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1541 @c complete accuracy in these examples; space introduced for clarity.
1542 @c If texinfo enhancements make it unnecessary, it would be nice to
1543 @c replace " @key" by "@key" in the following...
1545 (@value{GDBP}) info bre @key{TAB}
1549 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1550 the only @code{info} subcommand beginning with @samp{bre}:
1553 (@value{GDBP}) info breakpoints
1557 You can either press @key{RET} at this point, to run the @code{info
1558 breakpoints} command, or backspace and enter something else, if
1559 @samp{breakpoints} does not look like the command you expected. (If you
1560 were sure you wanted @code{info breakpoints} in the first place, you
1561 might as well just type @key{RET} immediately after @samp{info bre},
1562 to exploit command abbreviations rather than command completion).
1564 If there is more than one possibility for the next word when you press
1565 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1566 characters and try again, or just press @key{TAB} a second time;
1567 @value{GDBN} displays all the possible completions for that word. For
1568 example, you might want to set a breakpoint on a subroutine whose name
1569 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1570 just sounds the bell. Typing @key{TAB} again displays all the
1571 function names in your program that begin with those characters, for
1575 (@value{GDBP}) b make_ @key{TAB}
1576 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1577 make_a_section_from_file make_environ
1578 make_abs_section make_function_type
1579 make_blockvector make_pointer_type
1580 make_cleanup make_reference_type
1581 make_command make_symbol_completion_list
1582 (@value{GDBP}) b make_
1586 After displaying the available possibilities, @value{GDBN} copies your
1587 partial input (@samp{b make_} in the example) so you can finish the
1590 If you just want to see the list of alternatives in the first place, you
1591 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1592 means @kbd{@key{META} ?}. You can type this either by holding down a
1593 key designated as the @key{META} shift on your keyboard (if there is
1594 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1596 If the number of possible completions is large, @value{GDBN} will
1597 print as much of the list as it has collected, as well as a message
1598 indicating that the list may be truncated.
1601 (@value{GDBP}) b m@key{TAB}@key{TAB}
1603 <... the rest of the possible completions ...>
1604 *** List may be truncated, max-completions reached. ***
1609 This behavior can be controlled with the following commands:
1612 @kindex set max-completions
1613 @item set max-completions @var{limit}
1614 @itemx set max-completions unlimited
1615 Set the maximum number of completion candidates. @value{GDBN} will
1616 stop looking for more completions once it collects this many candidates.
1617 This is useful when completing on things like function names as collecting
1618 all the possible candidates can be time consuming.
1619 The default value is 200. A value of zero disables tab-completion.
1620 Note that setting either no limit or a very large limit can make
1622 @kindex show max-completions
1623 @item show max-completions
1624 Show the maximum number of candidates that @value{GDBN} will collect and show
1628 @cindex quotes in commands
1629 @cindex completion of quoted strings
1630 Sometimes the string you need, while logically a ``word'', may contain
1631 parentheses or other characters that @value{GDBN} normally excludes from
1632 its notion of a word. To permit word completion to work in this
1633 situation, you may enclose words in @code{'} (single quote marks) in
1634 @value{GDBN} commands.
1636 The most likely situation where you might need this is in typing the
1637 name of a C@t{++} function. This is because C@t{++} allows function
1638 overloading (multiple definitions of the same function, distinguished
1639 by argument type). For example, when you want to set a breakpoint you
1640 may need to distinguish whether you mean the version of @code{name}
1641 that takes an @code{int} parameter, @code{name(int)}, or the version
1642 that takes a @code{float} parameter, @code{name(float)}. To use the
1643 word-completion facilities in this situation, type a single quote
1644 @code{'} at the beginning of the function name. This alerts
1645 @value{GDBN} that it may need to consider more information than usual
1646 when you press @key{TAB} or @kbd{M-?} to request word completion:
1649 (@value{GDBP}) b 'bubble( @kbd{M-?}
1650 bubble(double,double) bubble(int,int)
1651 (@value{GDBP}) b 'bubble(
1654 In some cases, @value{GDBN} can tell that completing a name requires using
1655 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1656 completing as much as it can) if you do not type the quote in the first
1660 (@value{GDBP}) b bub @key{TAB}
1661 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1662 (@value{GDBP}) b 'bubble(
1666 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1667 you have not yet started typing the argument list when you ask for
1668 completion on an overloaded symbol.
1670 For more information about overloaded functions, see @ref{C Plus Plus
1671 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1672 overload-resolution off} to disable overload resolution;
1673 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1675 @cindex completion of structure field names
1676 @cindex structure field name completion
1677 @cindex completion of union field names
1678 @cindex union field name completion
1679 When completing in an expression which looks up a field in a
1680 structure, @value{GDBN} also tries@footnote{The completer can be
1681 confused by certain kinds of invalid expressions. Also, it only
1682 examines the static type of the expression, not the dynamic type.} to
1683 limit completions to the field names available in the type of the
1687 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1688 magic to_fputs to_rewind
1689 to_data to_isatty to_write
1690 to_delete to_put to_write_async_safe
1695 This is because the @code{gdb_stdout} is a variable of the type
1696 @code{struct ui_file} that is defined in @value{GDBN} sources as
1703 ui_file_flush_ftype *to_flush;
1704 ui_file_write_ftype *to_write;
1705 ui_file_write_async_safe_ftype *to_write_async_safe;
1706 ui_file_fputs_ftype *to_fputs;
1707 ui_file_read_ftype *to_read;
1708 ui_file_delete_ftype *to_delete;
1709 ui_file_isatty_ftype *to_isatty;
1710 ui_file_rewind_ftype *to_rewind;
1711 ui_file_put_ftype *to_put;
1718 @section Getting Help
1719 @cindex online documentation
1722 You can always ask @value{GDBN} itself for information on its commands,
1723 using the command @code{help}.
1726 @kindex h @r{(@code{help})}
1729 You can use @code{help} (abbreviated @code{h}) with no arguments to
1730 display a short list of named classes of commands:
1734 List of classes of commands:
1736 aliases -- Aliases of other commands
1737 breakpoints -- Making program stop at certain points
1738 data -- Examining data
1739 files -- Specifying and examining files
1740 internals -- Maintenance commands
1741 obscure -- Obscure features
1742 running -- Running the program
1743 stack -- Examining the stack
1744 status -- Status inquiries
1745 support -- Support facilities
1746 tracepoints -- Tracing of program execution without
1747 stopping the program
1748 user-defined -- User-defined commands
1750 Type "help" followed by a class name for a list of
1751 commands in that class.
1752 Type "help" followed by command name for full
1754 Command name abbreviations are allowed if unambiguous.
1757 @c the above line break eliminates huge line overfull...
1759 @item help @var{class}
1760 Using one of the general help classes as an argument, you can get a
1761 list of the individual commands in that class. For example, here is the
1762 help display for the class @code{status}:
1765 (@value{GDBP}) help status
1770 @c Line break in "show" line falsifies real output, but needed
1771 @c to fit in smallbook page size.
1772 info -- Generic command for showing things
1773 about the program being debugged
1774 show -- Generic command for showing things
1777 Type "help" followed by command name for full
1779 Command name abbreviations are allowed if unambiguous.
1783 @item help @var{command}
1784 With a command name as @code{help} argument, @value{GDBN} displays a
1785 short paragraph on how to use that command.
1788 @item apropos @var{args}
1789 The @code{apropos} command searches through all of the @value{GDBN}
1790 commands, and their documentation, for the regular expression specified in
1791 @var{args}. It prints out all matches found. For example:
1802 alias -- Define a new command that is an alias of an existing command
1803 aliases -- Aliases of other commands
1804 d -- Delete some breakpoints or auto-display expressions
1805 del -- Delete some breakpoints or auto-display expressions
1806 delete -- Delete some breakpoints or auto-display expressions
1811 @item complete @var{args}
1812 The @code{complete @var{args}} command lists all the possible completions
1813 for the beginning of a command. Use @var{args} to specify the beginning of the
1814 command you want completed. For example:
1820 @noindent results in:
1831 @noindent This is intended for use by @sc{gnu} Emacs.
1834 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1835 and @code{show} to inquire about the state of your program, or the state
1836 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1837 manual introduces each of them in the appropriate context. The listings
1838 under @code{info} and under @code{show} in the Command, Variable, and
1839 Function Index point to all the sub-commands. @xref{Command and Variable
1845 @kindex i @r{(@code{info})}
1847 This command (abbreviated @code{i}) is for describing the state of your
1848 program. For example, you can show the arguments passed to a function
1849 with @code{info args}, list the registers currently in use with @code{info
1850 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1851 You can get a complete list of the @code{info} sub-commands with
1852 @w{@code{help info}}.
1856 You can assign the result of an expression to an environment variable with
1857 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1858 @code{set prompt $}.
1862 In contrast to @code{info}, @code{show} is for describing the state of
1863 @value{GDBN} itself.
1864 You can change most of the things you can @code{show}, by using the
1865 related command @code{set}; for example, you can control what number
1866 system is used for displays with @code{set radix}, or simply inquire
1867 which is currently in use with @code{show radix}.
1870 To display all the settable parameters and their current
1871 values, you can use @code{show} with no arguments; you may also use
1872 @code{info set}. Both commands produce the same display.
1873 @c FIXME: "info set" violates the rule that "info" is for state of
1874 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1875 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1879 Here are several miscellaneous @code{show} subcommands, all of which are
1880 exceptional in lacking corresponding @code{set} commands:
1883 @kindex show version
1884 @cindex @value{GDBN} version number
1886 Show what version of @value{GDBN} is running. You should include this
1887 information in @value{GDBN} bug-reports. If multiple versions of
1888 @value{GDBN} are in use at your site, you may need to determine which
1889 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1890 commands are introduced, and old ones may wither away. Also, many
1891 system vendors ship variant versions of @value{GDBN}, and there are
1892 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1893 The version number is the same as the one announced when you start
1896 @kindex show copying
1897 @kindex info copying
1898 @cindex display @value{GDBN} copyright
1901 Display information about permission for copying @value{GDBN}.
1903 @kindex show warranty
1904 @kindex info warranty
1906 @itemx info warranty
1907 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1908 if your version of @value{GDBN} comes with one.
1910 @kindex show configuration
1911 @item show configuration
1912 Display detailed information about the way @value{GDBN} was configured
1913 when it was built. This displays the optional arguments passed to the
1914 @file{configure} script and also configuration parameters detected
1915 automatically by @command{configure}. When reporting a @value{GDBN}
1916 bug (@pxref{GDB Bugs}), it is important to include this information in
1922 @chapter Running Programs Under @value{GDBN}
1924 When you run a program under @value{GDBN}, you must first generate
1925 debugging information when you compile it.
1927 You may start @value{GDBN} with its arguments, if any, in an environment
1928 of your choice. If you are doing native debugging, you may redirect
1929 your program's input and output, debug an already running process, or
1930 kill a child process.
1933 * Compilation:: Compiling for debugging
1934 * Starting:: Starting your program
1935 * Arguments:: Your program's arguments
1936 * Environment:: Your program's environment
1938 * Working Directory:: Your program's working directory
1939 * Input/Output:: Your program's input and output
1940 * Attach:: Debugging an already-running process
1941 * Kill Process:: Killing the child process
1943 * Inferiors and Programs:: Debugging multiple inferiors and programs
1944 * Threads:: Debugging programs with multiple threads
1945 * Forks:: Debugging forks
1946 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1950 @section Compiling for Debugging
1952 In order to debug a program effectively, you need to generate
1953 debugging information when you compile it. This debugging information
1954 is stored in the object file; it describes the data type of each
1955 variable or function and the correspondence between source line numbers
1956 and addresses in the executable code.
1958 To request debugging information, specify the @samp{-g} option when you run
1961 Programs that are to be shipped to your customers are compiled with
1962 optimizations, using the @samp{-O} compiler option. However, some
1963 compilers are unable to handle the @samp{-g} and @samp{-O} options
1964 together. Using those compilers, you cannot generate optimized
1965 executables containing debugging information.
1967 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1968 without @samp{-O}, making it possible to debug optimized code. We
1969 recommend that you @emph{always} use @samp{-g} whenever you compile a
1970 program. You may think your program is correct, but there is no sense
1971 in pushing your luck. For more information, see @ref{Optimized Code}.
1973 Older versions of the @sc{gnu} C compiler permitted a variant option
1974 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1975 format; if your @sc{gnu} C compiler has this option, do not use it.
1977 @value{GDBN} knows about preprocessor macros and can show you their
1978 expansion (@pxref{Macros}). Most compilers do not include information
1979 about preprocessor macros in the debugging information if you specify
1980 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1981 the @sc{gnu} C compiler, provides macro information if you are using
1982 the DWARF debugging format, and specify the option @option{-g3}.
1984 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1985 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1986 information on @value{NGCC} options affecting debug information.
1988 You will have the best debugging experience if you use the latest
1989 version of the DWARF debugging format that your compiler supports.
1990 DWARF is currently the most expressive and best supported debugging
1991 format in @value{GDBN}.
1995 @section Starting your Program
2001 @kindex r @r{(@code{run})}
2004 Use the @code{run} command to start your program under @value{GDBN}.
2005 You must first specify the program name with an argument to
2006 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2007 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2008 command (@pxref{Files, ,Commands to Specify Files}).
2012 If you are running your program in an execution environment that
2013 supports processes, @code{run} creates an inferior process and makes
2014 that process run your program. In some environments without processes,
2015 @code{run} jumps to the start of your program. Other targets,
2016 like @samp{remote}, are always running. If you get an error
2017 message like this one:
2020 The "remote" target does not support "run".
2021 Try "help target" or "continue".
2025 then use @code{continue} to run your program. You may need @code{load}
2026 first (@pxref{load}).
2028 The execution of a program is affected by certain information it
2029 receives from its superior. @value{GDBN} provides ways to specify this
2030 information, which you must do @emph{before} starting your program. (You
2031 can change it after starting your program, but such changes only affect
2032 your program the next time you start it.) This information may be
2033 divided into four categories:
2036 @item The @emph{arguments.}
2037 Specify the arguments to give your program as the arguments of the
2038 @code{run} command. If a shell is available on your target, the shell
2039 is used to pass the arguments, so that you may use normal conventions
2040 (such as wildcard expansion or variable substitution) in describing
2042 In Unix systems, you can control which shell is used with the
2043 @code{SHELL} environment variable. If you do not define @code{SHELL},
2044 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2045 use of any shell with the @code{set startup-with-shell} command (see
2048 @item The @emph{environment.}
2049 Your program normally inherits its environment from @value{GDBN}, but you can
2050 use the @value{GDBN} commands @code{set environment} and @code{unset
2051 environment} to change parts of the environment that affect
2052 your program. @xref{Environment, ,Your Program's Environment}.
2054 @item The @emph{working directory.}
2055 Your program inherits its working directory from @value{GDBN}. You can set
2056 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2057 @xref{Working Directory, ,Your Program's Working Directory}.
2059 @item The @emph{standard input and output.}
2060 Your program normally uses the same device for standard input and
2061 standard output as @value{GDBN} is using. You can redirect input and output
2062 in the @code{run} command line, or you can use the @code{tty} command to
2063 set a different device for your program.
2064 @xref{Input/Output, ,Your Program's Input and Output}.
2067 @emph{Warning:} While input and output redirection work, you cannot use
2068 pipes to pass the output of the program you are debugging to another
2069 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2073 When you issue the @code{run} command, your program begins to execute
2074 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2075 of how to arrange for your program to stop. Once your program has
2076 stopped, you may call functions in your program, using the @code{print}
2077 or @code{call} commands. @xref{Data, ,Examining Data}.
2079 If the modification time of your symbol file has changed since the last
2080 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2081 table, and reads it again. When it does this, @value{GDBN} tries to retain
2082 your current breakpoints.
2087 @cindex run to main procedure
2088 The name of the main procedure can vary from language to language.
2089 With C or C@t{++}, the main procedure name is always @code{main}, but
2090 other languages such as Ada do not require a specific name for their
2091 main procedure. The debugger provides a convenient way to start the
2092 execution of the program and to stop at the beginning of the main
2093 procedure, depending on the language used.
2095 The @samp{start} command does the equivalent of setting a temporary
2096 breakpoint at the beginning of the main procedure and then invoking
2097 the @samp{run} command.
2099 @cindex elaboration phase
2100 Some programs contain an @dfn{elaboration} phase where some startup code is
2101 executed before the main procedure is called. This depends on the
2102 languages used to write your program. In C@t{++}, for instance,
2103 constructors for static and global objects are executed before
2104 @code{main} is called. It is therefore possible that the debugger stops
2105 before reaching the main procedure. However, the temporary breakpoint
2106 will remain to halt execution.
2108 Specify the arguments to give to your program as arguments to the
2109 @samp{start} command. These arguments will be given verbatim to the
2110 underlying @samp{run} command. Note that the same arguments will be
2111 reused if no argument is provided during subsequent calls to
2112 @samp{start} or @samp{run}.
2114 It is sometimes necessary to debug the program during elaboration. In
2115 these cases, using the @code{start} command would stop the execution of
2116 your program too late, as the program would have already completed the
2117 elaboration phase. Under these circumstances, insert breakpoints in your
2118 elaboration code before running your program.
2120 @anchor{set exec-wrapper}
2121 @kindex set exec-wrapper
2122 @item set exec-wrapper @var{wrapper}
2123 @itemx show exec-wrapper
2124 @itemx unset exec-wrapper
2125 When @samp{exec-wrapper} is set, the specified wrapper is used to
2126 launch programs for debugging. @value{GDBN} starts your program
2127 with a shell command of the form @kbd{exec @var{wrapper}
2128 @var{program}}. Quoting is added to @var{program} and its
2129 arguments, but not to @var{wrapper}, so you should add quotes if
2130 appropriate for your shell. The wrapper runs until it executes
2131 your program, and then @value{GDBN} takes control.
2133 You can use any program that eventually calls @code{execve} with
2134 its arguments as a wrapper. Several standard Unix utilities do
2135 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2136 with @code{exec "$@@"} will also work.
2138 For example, you can use @code{env} to pass an environment variable to
2139 the debugged program, without setting the variable in your shell's
2143 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2147 This command is available when debugging locally on most targets, excluding
2148 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2150 @kindex set startup-with-shell
2151 @item set startup-with-shell
2152 @itemx set startup-with-shell on
2153 @itemx set startup-with-shell off
2154 @itemx show set startup-with-shell
2155 On Unix systems, by default, if a shell is available on your target,
2156 @value{GDBN}) uses it to start your program. Arguments of the
2157 @code{run} command are passed to the shell, which does variable
2158 substitution, expands wildcard characters and performs redirection of
2159 I/O. In some circumstances, it may be useful to disable such use of a
2160 shell, for example, when debugging the shell itself or diagnosing
2161 startup failures such as:
2165 Starting program: ./a.out
2166 During startup program terminated with signal SIGSEGV, Segmentation fault.
2170 which indicates the shell or the wrapper specified with
2171 @samp{exec-wrapper} crashed, not your program. Most often, this is
2172 caused by something odd in your shell's non-interactive mode
2173 initialization file---such as @file{.cshrc} for C-shell,
2174 $@file{.zshenv} for the Z shell, or the file specified in the
2175 @samp{BASH_ENV} environment variable for BASH.
2177 @anchor{set auto-connect-native-target}
2178 @kindex set auto-connect-native-target
2179 @item set auto-connect-native-target
2180 @itemx set auto-connect-native-target on
2181 @itemx set auto-connect-native-target off
2182 @itemx show auto-connect-native-target
2184 By default, if not connected to any target yet (e.g., with
2185 @code{target remote}), the @code{run} command starts your program as a
2186 native process under @value{GDBN}, on your local machine. If you're
2187 sure you don't want to debug programs on your local machine, you can
2188 tell @value{GDBN} to not connect to the native target automatically
2189 with the @code{set auto-connect-native-target off} command.
2191 If @code{on}, which is the default, and if @value{GDBN} is not
2192 connected to a target already, the @code{run} command automaticaly
2193 connects to the native target, if one is available.
2195 If @code{off}, and if @value{GDBN} is not connected to a target
2196 already, the @code{run} command fails with an error:
2200 Don't know how to run. Try "help target".
2203 If @value{GDBN} is already connected to a target, @value{GDBN} always
2204 uses it with the @code{run} command.
2206 In any case, you can explicitly connect to the native target with the
2207 @code{target native} command. For example,
2210 (@value{GDBP}) set auto-connect-native-target off
2212 Don't know how to run. Try "help target".
2213 (@value{GDBP}) target native
2215 Starting program: ./a.out
2216 [Inferior 1 (process 10421) exited normally]
2219 In case you connected explicitly to the @code{native} target,
2220 @value{GDBN} remains connected even if all inferiors exit, ready for
2221 the next @code{run} command. Use the @code{disconnect} command to
2224 Examples of other commands that likewise respect the
2225 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2226 proc}, @code{info os}.
2228 @kindex set disable-randomization
2229 @item set disable-randomization
2230 @itemx set disable-randomization on
2231 This option (enabled by default in @value{GDBN}) will turn off the native
2232 randomization of the virtual address space of the started program. This option
2233 is useful for multiple debugging sessions to make the execution better
2234 reproducible and memory addresses reusable across debugging sessions.
2236 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2237 On @sc{gnu}/Linux you can get the same behavior using
2240 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2243 @item set disable-randomization off
2244 Leave the behavior of the started executable unchanged. Some bugs rear their
2245 ugly heads only when the program is loaded at certain addresses. If your bug
2246 disappears when you run the program under @value{GDBN}, that might be because
2247 @value{GDBN} by default disables the address randomization on platforms, such
2248 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2249 disable-randomization off} to try to reproduce such elusive bugs.
2251 On targets where it is available, virtual address space randomization
2252 protects the programs against certain kinds of security attacks. In these
2253 cases the attacker needs to know the exact location of a concrete executable
2254 code. Randomizing its location makes it impossible to inject jumps misusing
2255 a code at its expected addresses.
2257 Prelinking shared libraries provides a startup performance advantage but it
2258 makes addresses in these libraries predictable for privileged processes by
2259 having just unprivileged access at the target system. Reading the shared
2260 library binary gives enough information for assembling the malicious code
2261 misusing it. Still even a prelinked shared library can get loaded at a new
2262 random address just requiring the regular relocation process during the
2263 startup. Shared libraries not already prelinked are always loaded at
2264 a randomly chosen address.
2266 Position independent executables (PIE) contain position independent code
2267 similar to the shared libraries and therefore such executables get loaded at
2268 a randomly chosen address upon startup. PIE executables always load even
2269 already prelinked shared libraries at a random address. You can build such
2270 executable using @command{gcc -fPIE -pie}.
2272 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2273 (as long as the randomization is enabled).
2275 @item show disable-randomization
2276 Show the current setting of the explicit disable of the native randomization of
2277 the virtual address space of the started program.
2282 @section Your Program's Arguments
2284 @cindex arguments (to your program)
2285 The arguments to your program can be specified by the arguments of the
2287 They are passed to a shell, which expands wildcard characters and
2288 performs redirection of I/O, and thence to your program. Your
2289 @code{SHELL} environment variable (if it exists) specifies what shell
2290 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2291 the default shell (@file{/bin/sh} on Unix).
2293 On non-Unix systems, the program is usually invoked directly by
2294 @value{GDBN}, which emulates I/O redirection via the appropriate system
2295 calls, and the wildcard characters are expanded by the startup code of
2296 the program, not by the shell.
2298 @code{run} with no arguments uses the same arguments used by the previous
2299 @code{run}, or those set by the @code{set args} command.
2304 Specify the arguments to be used the next time your program is run. If
2305 @code{set args} has no arguments, @code{run} executes your program
2306 with no arguments. Once you have run your program with arguments,
2307 using @code{set args} before the next @code{run} is the only way to run
2308 it again without arguments.
2312 Show the arguments to give your program when it is started.
2316 @section Your Program's Environment
2318 @cindex environment (of your program)
2319 The @dfn{environment} consists of a set of environment variables and
2320 their values. Environment variables conventionally record such things as
2321 your user name, your home directory, your terminal type, and your search
2322 path for programs to run. Usually you set up environment variables with
2323 the shell and they are inherited by all the other programs you run. When
2324 debugging, it can be useful to try running your program with a modified
2325 environment without having to start @value{GDBN} over again.
2329 @item path @var{directory}
2330 Add @var{directory} to the front of the @code{PATH} environment variable
2331 (the search path for executables) that will be passed to your program.
2332 The value of @code{PATH} used by @value{GDBN} does not change.
2333 You may specify several directory names, separated by whitespace or by a
2334 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2335 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2336 is moved to the front, so it is searched sooner.
2338 You can use the string @samp{$cwd} to refer to whatever is the current
2339 working directory at the time @value{GDBN} searches the path. If you
2340 use @samp{.} instead, it refers to the directory where you executed the
2341 @code{path} command. @value{GDBN} replaces @samp{.} in the
2342 @var{directory} argument (with the current path) before adding
2343 @var{directory} to the search path.
2344 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2345 @c document that, since repeating it would be a no-op.
2349 Display the list of search paths for executables (the @code{PATH}
2350 environment variable).
2352 @kindex show environment
2353 @item show environment @r{[}@var{varname}@r{]}
2354 Print the value of environment variable @var{varname} to be given to
2355 your program when it starts. If you do not supply @var{varname},
2356 print the names and values of all environment variables to be given to
2357 your program. You can abbreviate @code{environment} as @code{env}.
2359 @kindex set environment
2360 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2361 Set environment variable @var{varname} to @var{value}. The value
2362 changes for your program (and the shell @value{GDBN} uses to launch
2363 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2364 values of environment variables are just strings, and any
2365 interpretation is supplied by your program itself. The @var{value}
2366 parameter is optional; if it is eliminated, the variable is set to a
2368 @c "any string" here does not include leading, trailing
2369 @c blanks. Gnu asks: does anyone care?
2371 For example, this command:
2378 tells the debugged program, when subsequently run, that its user is named
2379 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2380 are not actually required.)
2382 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2383 which also inherits the environment set with @code{set environment}.
2384 If necessary, you can avoid that by using the @samp{env} program as a
2385 wrapper instead of using @code{set environment}. @xref{set
2386 exec-wrapper}, for an example doing just that.
2388 @kindex unset environment
2389 @item unset environment @var{varname}
2390 Remove variable @var{varname} from the environment to be passed to your
2391 program. This is different from @samp{set env @var{varname} =};
2392 @code{unset environment} removes the variable from the environment,
2393 rather than assigning it an empty value.
2396 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2397 the shell indicated by your @code{SHELL} environment variable if it
2398 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2399 names a shell that runs an initialization file when started
2400 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2401 for the Z shell, or the file specified in the @samp{BASH_ENV}
2402 environment variable for BASH---any variables you set in that file
2403 affect your program. You may wish to move setting of environment
2404 variables to files that are only run when you sign on, such as
2405 @file{.login} or @file{.profile}.
2407 @node Working Directory
2408 @section Your Program's Working Directory
2410 @cindex working directory (of your program)
2411 Each time you start your program with @code{run}, it inherits its
2412 working directory from the current working directory of @value{GDBN}.
2413 The @value{GDBN} working directory is initially whatever it inherited
2414 from its parent process (typically the shell), but you can specify a new
2415 working directory in @value{GDBN} with the @code{cd} command.
2417 The @value{GDBN} working directory also serves as a default for the commands
2418 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2423 @cindex change working directory
2424 @item cd @r{[}@var{directory}@r{]}
2425 Set the @value{GDBN} working directory to @var{directory}. If not
2426 given, @var{directory} uses @file{'~'}.
2430 Print the @value{GDBN} working directory.
2433 It is generally impossible to find the current working directory of
2434 the process being debugged (since a program can change its directory
2435 during its run). If you work on a system where @value{GDBN} is
2436 configured with the @file{/proc} support, you can use the @code{info
2437 proc} command (@pxref{SVR4 Process Information}) to find out the
2438 current working directory of the debuggee.
2441 @section Your Program's Input and Output
2446 By default, the program you run under @value{GDBN} does input and output to
2447 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2448 to its own terminal modes to interact with you, but it records the terminal
2449 modes your program was using and switches back to them when you continue
2450 running your program.
2453 @kindex info terminal
2455 Displays information recorded by @value{GDBN} about the terminal modes your
2459 You can redirect your program's input and/or output using shell
2460 redirection with the @code{run} command. For example,
2467 starts your program, diverting its output to the file @file{outfile}.
2470 @cindex controlling terminal
2471 Another way to specify where your program should do input and output is
2472 with the @code{tty} command. This command accepts a file name as
2473 argument, and causes this file to be the default for future @code{run}
2474 commands. It also resets the controlling terminal for the child
2475 process, for future @code{run} commands. For example,
2482 directs that processes started with subsequent @code{run} commands
2483 default to do input and output on the terminal @file{/dev/ttyb} and have
2484 that as their controlling terminal.
2486 An explicit redirection in @code{run} overrides the @code{tty} command's
2487 effect on the input/output device, but not its effect on the controlling
2490 When you use the @code{tty} command or redirect input in the @code{run}
2491 command, only the input @emph{for your program} is affected. The input
2492 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2493 for @code{set inferior-tty}.
2495 @cindex inferior tty
2496 @cindex set inferior controlling terminal
2497 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2498 display the name of the terminal that will be used for future runs of your
2502 @item set inferior-tty /dev/ttyb
2503 @kindex set inferior-tty
2504 Set the tty for the program being debugged to /dev/ttyb.
2506 @item show inferior-tty
2507 @kindex show inferior-tty
2508 Show the current tty for the program being debugged.
2512 @section Debugging an Already-running Process
2517 @item attach @var{process-id}
2518 This command attaches to a running process---one that was started
2519 outside @value{GDBN}. (@code{info files} shows your active
2520 targets.) The command takes as argument a process ID. The usual way to
2521 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2522 or with the @samp{jobs -l} shell command.
2524 @code{attach} does not repeat if you press @key{RET} a second time after
2525 executing the command.
2528 To use @code{attach}, your program must be running in an environment
2529 which supports processes; for example, @code{attach} does not work for
2530 programs on bare-board targets that lack an operating system. You must
2531 also have permission to send the process a signal.
2533 When you use @code{attach}, the debugger finds the program running in
2534 the process first by looking in the current working directory, then (if
2535 the program is not found) by using the source file search path
2536 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2537 the @code{file} command to load the program. @xref{Files, ,Commands to
2540 The first thing @value{GDBN} does after arranging to debug the specified
2541 process is to stop it. You can examine and modify an attached process
2542 with all the @value{GDBN} commands that are ordinarily available when
2543 you start processes with @code{run}. You can insert breakpoints; you
2544 can step and continue; you can modify storage. If you would rather the
2545 process continue running, you may use the @code{continue} command after
2546 attaching @value{GDBN} to the process.
2551 When you have finished debugging the attached process, you can use the
2552 @code{detach} command to release it from @value{GDBN} control. Detaching
2553 the process continues its execution. After the @code{detach} command,
2554 that process and @value{GDBN} become completely independent once more, and you
2555 are ready to @code{attach} another process or start one with @code{run}.
2556 @code{detach} does not repeat if you press @key{RET} again after
2557 executing the command.
2560 If you exit @value{GDBN} while you have an attached process, you detach
2561 that process. If you use the @code{run} command, you kill that process.
2562 By default, @value{GDBN} asks for confirmation if you try to do either of these
2563 things; you can control whether or not you need to confirm by using the
2564 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2568 @section Killing the Child Process
2573 Kill the child process in which your program is running under @value{GDBN}.
2576 This command is useful if you wish to debug a core dump instead of a
2577 running process. @value{GDBN} ignores any core dump file while your program
2580 On some operating systems, a program cannot be executed outside @value{GDBN}
2581 while you have breakpoints set on it inside @value{GDBN}. You can use the
2582 @code{kill} command in this situation to permit running your program
2583 outside the debugger.
2585 The @code{kill} command is also useful if you wish to recompile and
2586 relink your program, since on many systems it is impossible to modify an
2587 executable file while it is running in a process. In this case, when you
2588 next type @code{run}, @value{GDBN} notices that the file has changed, and
2589 reads the symbol table again (while trying to preserve your current
2590 breakpoint settings).
2592 @node Inferiors and Programs
2593 @section Debugging Multiple Inferiors and Programs
2595 @value{GDBN} lets you run and debug multiple programs in a single
2596 session. In addition, @value{GDBN} on some systems may let you run
2597 several programs simultaneously (otherwise you have to exit from one
2598 before starting another). In the most general case, you can have
2599 multiple threads of execution in each of multiple processes, launched
2600 from multiple executables.
2603 @value{GDBN} represents the state of each program execution with an
2604 object called an @dfn{inferior}. An inferior typically corresponds to
2605 a process, but is more general and applies also to targets that do not
2606 have processes. Inferiors may be created before a process runs, and
2607 may be retained after a process exits. Inferiors have unique
2608 identifiers that are different from process ids. Usually each
2609 inferior will also have its own distinct address space, although some
2610 embedded targets may have several inferiors running in different parts
2611 of a single address space. Each inferior may in turn have multiple
2612 threads running in it.
2614 To find out what inferiors exist at any moment, use @w{@code{info
2618 @kindex info inferiors
2619 @item info inferiors
2620 Print a list of all inferiors currently being managed by @value{GDBN}.
2622 @value{GDBN} displays for each inferior (in this order):
2626 the inferior number assigned by @value{GDBN}
2629 the target system's inferior identifier
2632 the name of the executable the inferior is running.
2637 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2638 indicates the current inferior.
2642 @c end table here to get a little more width for example
2645 (@value{GDBP}) info inferiors
2646 Num Description Executable
2647 2 process 2307 hello
2648 * 1 process 3401 goodbye
2651 To switch focus between inferiors, use the @code{inferior} command:
2654 @kindex inferior @var{infno}
2655 @item inferior @var{infno}
2656 Make inferior number @var{infno} the current inferior. The argument
2657 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2658 in the first field of the @samp{info inferiors} display.
2662 You can get multiple executables into a debugging session via the
2663 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2664 systems @value{GDBN} can add inferiors to the debug session
2665 automatically by following calls to @code{fork} and @code{exec}. To
2666 remove inferiors from the debugging session use the
2667 @w{@code{remove-inferiors}} command.
2670 @kindex add-inferior
2671 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2672 Adds @var{n} inferiors to be run using @var{executable} as the
2673 executable; @var{n} defaults to 1. If no executable is specified,
2674 the inferiors begins empty, with no program. You can still assign or
2675 change the program assigned to the inferior at any time by using the
2676 @code{file} command with the executable name as its argument.
2678 @kindex clone-inferior
2679 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2680 Adds @var{n} inferiors ready to execute the same program as inferior
2681 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2682 number of the current inferior. This is a convenient command when you
2683 want to run another instance of the inferior you are debugging.
2686 (@value{GDBP}) info inferiors
2687 Num Description Executable
2688 * 1 process 29964 helloworld
2689 (@value{GDBP}) clone-inferior
2692 (@value{GDBP}) info inferiors
2693 Num Description Executable
2695 * 1 process 29964 helloworld
2698 You can now simply switch focus to inferior 2 and run it.
2700 @kindex remove-inferiors
2701 @item remove-inferiors @var{infno}@dots{}
2702 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2703 possible to remove an inferior that is running with this command. For
2704 those, use the @code{kill} or @code{detach} command first.
2708 To quit debugging one of the running inferiors that is not the current
2709 inferior, you can either detach from it by using the @w{@code{detach
2710 inferior}} command (allowing it to run independently), or kill it
2711 using the @w{@code{kill inferiors}} command:
2714 @kindex detach inferiors @var{infno}@dots{}
2715 @item detach inferior @var{infno}@dots{}
2716 Detach from the inferior or inferiors identified by @value{GDBN}
2717 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2718 still stays on the list of inferiors shown by @code{info inferiors},
2719 but its Description will show @samp{<null>}.
2721 @kindex kill inferiors @var{infno}@dots{}
2722 @item kill inferiors @var{infno}@dots{}
2723 Kill the inferior or inferiors identified by @value{GDBN} inferior
2724 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2725 stays on the list of inferiors shown by @code{info inferiors}, but its
2726 Description will show @samp{<null>}.
2729 After the successful completion of a command such as @code{detach},
2730 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2731 a normal process exit, the inferior is still valid and listed with
2732 @code{info inferiors}, ready to be restarted.
2735 To be notified when inferiors are started or exit under @value{GDBN}'s
2736 control use @w{@code{set print inferior-events}}:
2739 @kindex set print inferior-events
2740 @cindex print messages on inferior start and exit
2741 @item set print inferior-events
2742 @itemx set print inferior-events on
2743 @itemx set print inferior-events off
2744 The @code{set print inferior-events} command allows you to enable or
2745 disable printing of messages when @value{GDBN} notices that new
2746 inferiors have started or that inferiors have exited or have been
2747 detached. By default, these messages will not be printed.
2749 @kindex show print inferior-events
2750 @item show print inferior-events
2751 Show whether messages will be printed when @value{GDBN} detects that
2752 inferiors have started, exited or have been detached.
2755 Many commands will work the same with multiple programs as with a
2756 single program: e.g., @code{print myglobal} will simply display the
2757 value of @code{myglobal} in the current inferior.
2760 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2761 get more info about the relationship of inferiors, programs, address
2762 spaces in a debug session. You can do that with the @w{@code{maint
2763 info program-spaces}} command.
2766 @kindex maint info program-spaces
2767 @item maint info program-spaces
2768 Print a list of all program spaces currently being managed by
2771 @value{GDBN} displays for each program space (in this order):
2775 the program space number assigned by @value{GDBN}
2778 the name of the executable loaded into the program space, with e.g.,
2779 the @code{file} command.
2784 An asterisk @samp{*} preceding the @value{GDBN} program space number
2785 indicates the current program space.
2787 In addition, below each program space line, @value{GDBN} prints extra
2788 information that isn't suitable to display in tabular form. For
2789 example, the list of inferiors bound to the program space.
2792 (@value{GDBP}) maint info program-spaces
2795 Bound inferiors: ID 1 (process 21561)
2799 Here we can see that no inferior is running the program @code{hello},
2800 while @code{process 21561} is running the program @code{goodbye}. On
2801 some targets, it is possible that multiple inferiors are bound to the
2802 same program space. The most common example is that of debugging both
2803 the parent and child processes of a @code{vfork} call. For example,
2806 (@value{GDBP}) maint info program-spaces
2809 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2812 Here, both inferior 2 and inferior 1 are running in the same program
2813 space as a result of inferior 1 having executed a @code{vfork} call.
2817 @section Debugging Programs with Multiple Threads
2819 @cindex threads of execution
2820 @cindex multiple threads
2821 @cindex switching threads
2822 In some operating systems, such as HP-UX and Solaris, a single program
2823 may have more than one @dfn{thread} of execution. The precise semantics
2824 of threads differ from one operating system to another, but in general
2825 the threads of a single program are akin to multiple processes---except
2826 that they share one address space (that is, they can all examine and
2827 modify the same variables). On the other hand, each thread has its own
2828 registers and execution stack, and perhaps private memory.
2830 @value{GDBN} provides these facilities for debugging multi-thread
2834 @item automatic notification of new threads
2835 @item @samp{thread @var{threadno}}, a command to switch among threads
2836 @item @samp{info threads}, a command to inquire about existing threads
2837 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2838 a command to apply a command to a list of threads
2839 @item thread-specific breakpoints
2840 @item @samp{set print thread-events}, which controls printing of
2841 messages on thread start and exit.
2842 @item @samp{set libthread-db-search-path @var{path}}, which lets
2843 the user specify which @code{libthread_db} to use if the default choice
2844 isn't compatible with the program.
2848 @emph{Warning:} These facilities are not yet available on every
2849 @value{GDBN} configuration where the operating system supports threads.
2850 If your @value{GDBN} does not support threads, these commands have no
2851 effect. For example, a system without thread support shows no output
2852 from @samp{info threads}, and always rejects the @code{thread} command,
2856 (@value{GDBP}) info threads
2857 (@value{GDBP}) thread 1
2858 Thread ID 1 not known. Use the "info threads" command to
2859 see the IDs of currently known threads.
2861 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2862 @c doesn't support threads"?
2865 @cindex focus of debugging
2866 @cindex current thread
2867 The @value{GDBN} thread debugging facility allows you to observe all
2868 threads while your program runs---but whenever @value{GDBN} takes
2869 control, one thread in particular is always the focus of debugging.
2870 This thread is called the @dfn{current thread}. Debugging commands show
2871 program information from the perspective of the current thread.
2873 @cindex @code{New} @var{systag} message
2874 @cindex thread identifier (system)
2875 @c FIXME-implementors!! It would be more helpful if the [New...] message
2876 @c included GDB's numeric thread handle, so you could just go to that
2877 @c thread without first checking `info threads'.
2878 Whenever @value{GDBN} detects a new thread in your program, it displays
2879 the target system's identification for the thread with a message in the
2880 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2881 whose form varies depending on the particular system. For example, on
2882 @sc{gnu}/Linux, you might see
2885 [New Thread 0x41e02940 (LWP 25582)]
2889 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2890 the @var{systag} is simply something like @samp{process 368}, with no
2893 @c FIXME!! (1) Does the [New...] message appear even for the very first
2894 @c thread of a program, or does it only appear for the
2895 @c second---i.e.@: when it becomes obvious we have a multithread
2897 @c (2) *Is* there necessarily a first thread always? Or do some
2898 @c multithread systems permit starting a program with multiple
2899 @c threads ab initio?
2901 @cindex thread number
2902 @cindex thread identifier (GDB)
2903 For debugging purposes, @value{GDBN} associates its own thread
2904 number---always a single integer---with each thread in your program.
2907 @kindex info threads
2908 @item info threads @r{[}@var{id}@dots{}@r{]}
2909 Display a summary of all threads currently in your program. Optional
2910 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2911 means to print information only about the specified thread or threads.
2912 @value{GDBN} displays for each thread (in this order):
2916 the thread number assigned by @value{GDBN}
2919 the target system's thread identifier (@var{systag})
2922 the thread's name, if one is known. A thread can either be named by
2923 the user (see @code{thread name}, below), or, in some cases, by the
2927 the current stack frame summary for that thread
2931 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2932 indicates the current thread.
2936 @c end table here to get a little more width for example
2939 (@value{GDBP}) info threads
2941 3 process 35 thread 27 0x34e5 in sigpause ()
2942 2 process 35 thread 23 0x34e5 in sigpause ()
2943 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2947 On Solaris, you can display more information about user threads with a
2948 Solaris-specific command:
2951 @item maint info sol-threads
2952 @kindex maint info sol-threads
2953 @cindex thread info (Solaris)
2954 Display info on Solaris user threads.
2958 @kindex thread @var{threadno}
2959 @item thread @var{threadno}
2960 Make thread number @var{threadno} the current thread. The command
2961 argument @var{threadno} is the internal @value{GDBN} thread number, as
2962 shown in the first field of the @samp{info threads} display.
2963 @value{GDBN} responds by displaying the system identifier of the thread
2964 you selected, and its current stack frame summary:
2967 (@value{GDBP}) thread 2
2968 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2969 #0 some_function (ignore=0x0) at example.c:8
2970 8 printf ("hello\n");
2974 As with the @samp{[New @dots{}]} message, the form of the text after
2975 @samp{Switching to} depends on your system's conventions for identifying
2978 @vindex $_thread@r{, convenience variable}
2979 The debugger convenience variable @samp{$_thread} contains the number
2980 of the current thread. You may find this useful in writing breakpoint
2981 conditional expressions, command scripts, and so forth. See
2982 @xref{Convenience Vars,, Convenience Variables}, for general
2983 information on convenience variables.
2985 @kindex thread apply
2986 @cindex apply command to several threads
2987 @item thread apply [@var{threadno} | all [-ascending]] @var{command}
2988 The @code{thread apply} command allows you to apply the named
2989 @var{command} to one or more threads. Specify the numbers of the
2990 threads that you want affected with the command argument
2991 @var{threadno}. It can be a single thread number, one of the numbers
2992 shown in the first field of the @samp{info threads} display; or it
2993 could be a range of thread numbers, as in @code{2-4}. To apply
2994 a command to all threads in descending order, type @kbd{thread apply all
2995 @var{command}}. To apply a command to all threads in ascending order,
2996 type @kbd{thread apply all -ascending @var{command}}.
3000 @cindex name a thread
3001 @item thread name [@var{name}]
3002 This command assigns a name to the current thread. If no argument is
3003 given, any existing user-specified name is removed. The thread name
3004 appears in the @samp{info threads} display.
3006 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3007 determine the name of the thread as given by the OS. On these
3008 systems, a name specified with @samp{thread name} will override the
3009 system-give name, and removing the user-specified name will cause
3010 @value{GDBN} to once again display the system-specified name.
3013 @cindex search for a thread
3014 @item thread find [@var{regexp}]
3015 Search for and display thread ids whose name or @var{systag}
3016 matches the supplied regular expression.
3018 As well as being the complement to the @samp{thread name} command,
3019 this command also allows you to identify a thread by its target
3020 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3024 (@value{GDBN}) thread find 26688
3025 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3026 (@value{GDBN}) info thread 4
3028 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3031 @kindex set print thread-events
3032 @cindex print messages on thread start and exit
3033 @item set print thread-events
3034 @itemx set print thread-events on
3035 @itemx set print thread-events off
3036 The @code{set print thread-events} command allows you to enable or
3037 disable printing of messages when @value{GDBN} notices that new threads have
3038 started or that threads have exited. By default, these messages will
3039 be printed if detection of these events is supported by the target.
3040 Note that these messages cannot be disabled on all targets.
3042 @kindex show print thread-events
3043 @item show print thread-events
3044 Show whether messages will be printed when @value{GDBN} detects that threads
3045 have started and exited.
3048 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3049 more information about how @value{GDBN} behaves when you stop and start
3050 programs with multiple threads.
3052 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3053 watchpoints in programs with multiple threads.
3055 @anchor{set libthread-db-search-path}
3057 @kindex set libthread-db-search-path
3058 @cindex search path for @code{libthread_db}
3059 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3060 If this variable is set, @var{path} is a colon-separated list of
3061 directories @value{GDBN} will use to search for @code{libthread_db}.
3062 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3063 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3064 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3067 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3068 @code{libthread_db} library to obtain information about threads in the
3069 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3070 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3071 specific thread debugging library loading is enabled
3072 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3074 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3075 refers to the default system directories that are
3076 normally searched for loading shared libraries. The @samp{$sdir} entry
3077 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3078 (@pxref{libthread_db.so.1 file}).
3080 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3081 refers to the directory from which @code{libpthread}
3082 was loaded in the inferior process.
3084 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3085 @value{GDBN} attempts to initialize it with the current inferior process.
3086 If this initialization fails (which could happen because of a version
3087 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3088 will unload @code{libthread_db}, and continue with the next directory.
3089 If none of @code{libthread_db} libraries initialize successfully,
3090 @value{GDBN} will issue a warning and thread debugging will be disabled.
3092 Setting @code{libthread-db-search-path} is currently implemented
3093 only on some platforms.
3095 @kindex show libthread-db-search-path
3096 @item show libthread-db-search-path
3097 Display current libthread_db search path.
3099 @kindex set debug libthread-db
3100 @kindex show debug libthread-db
3101 @cindex debugging @code{libthread_db}
3102 @item set debug libthread-db
3103 @itemx show debug libthread-db
3104 Turns on or off display of @code{libthread_db}-related events.
3105 Use @code{1} to enable, @code{0} to disable.
3109 @section Debugging Forks
3111 @cindex fork, debugging programs which call
3112 @cindex multiple processes
3113 @cindex processes, multiple
3114 On most systems, @value{GDBN} has no special support for debugging
3115 programs which create additional processes using the @code{fork}
3116 function. When a program forks, @value{GDBN} will continue to debug the
3117 parent process and the child process will run unimpeded. If you have
3118 set a breakpoint in any code which the child then executes, the child
3119 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3120 will cause it to terminate.
3122 However, if you want to debug the child process there is a workaround
3123 which isn't too painful. Put a call to @code{sleep} in the code which
3124 the child process executes after the fork. It may be useful to sleep
3125 only if a certain environment variable is set, or a certain file exists,
3126 so that the delay need not occur when you don't want to run @value{GDBN}
3127 on the child. While the child is sleeping, use the @code{ps} program to
3128 get its process ID. Then tell @value{GDBN} (a new invocation of
3129 @value{GDBN} if you are also debugging the parent process) to attach to
3130 the child process (@pxref{Attach}). From that point on you can debug
3131 the child process just like any other process which you attached to.
3133 On some systems, @value{GDBN} provides support for debugging programs that
3134 create additional processes using the @code{fork} or @code{vfork} functions.
3135 Currently, the only platforms with this feature are HP-UX (11.x and later
3136 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3138 The fork debugging commands are supported in both native mode and when
3139 connected to @code{gdbserver} using @kbd{target extended-remote}.
3141 By default, when a program forks, @value{GDBN} will continue to debug
3142 the parent process and the child process will run unimpeded.
3144 If you want to follow the child process instead of the parent process,
3145 use the command @w{@code{set follow-fork-mode}}.
3148 @kindex set follow-fork-mode
3149 @item set follow-fork-mode @var{mode}
3150 Set the debugger response to a program call of @code{fork} or
3151 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3152 process. The @var{mode} argument can be:
3156 The original process is debugged after a fork. The child process runs
3157 unimpeded. This is the default.
3160 The new process is debugged after a fork. The parent process runs
3165 @kindex show follow-fork-mode
3166 @item show follow-fork-mode
3167 Display the current debugger response to a @code{fork} or @code{vfork} call.
3170 @cindex debugging multiple processes
3171 On Linux, if you want to debug both the parent and child processes, use the
3172 command @w{@code{set detach-on-fork}}.
3175 @kindex set detach-on-fork
3176 @item set detach-on-fork @var{mode}
3177 Tells gdb whether to detach one of the processes after a fork, or
3178 retain debugger control over them both.
3182 The child process (or parent process, depending on the value of
3183 @code{follow-fork-mode}) will be detached and allowed to run
3184 independently. This is the default.
3187 Both processes will be held under the control of @value{GDBN}.
3188 One process (child or parent, depending on the value of
3189 @code{follow-fork-mode}) is debugged as usual, while the other
3194 @kindex show detach-on-fork
3195 @item show detach-on-fork
3196 Show whether detach-on-fork mode is on/off.
3199 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3200 will retain control of all forked processes (including nested forks).
3201 You can list the forked processes under the control of @value{GDBN} by
3202 using the @w{@code{info inferiors}} command, and switch from one fork
3203 to another by using the @code{inferior} command (@pxref{Inferiors and
3204 Programs, ,Debugging Multiple Inferiors and Programs}).
3206 To quit debugging one of the forked processes, you can either detach
3207 from it by using the @w{@code{detach inferiors}} command (allowing it
3208 to run independently), or kill it using the @w{@code{kill inferiors}}
3209 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3212 If you ask to debug a child process and a @code{vfork} is followed by an
3213 @code{exec}, @value{GDBN} executes the new target up to the first
3214 breakpoint in the new target. If you have a breakpoint set on
3215 @code{main} in your original program, the breakpoint will also be set on
3216 the child process's @code{main}.
3218 On some systems, when a child process is spawned by @code{vfork}, you
3219 cannot debug the child or parent until an @code{exec} call completes.
3221 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3222 call executes, the new target restarts. To restart the parent
3223 process, use the @code{file} command with the parent executable name
3224 as its argument. By default, after an @code{exec} call executes,
3225 @value{GDBN} discards the symbols of the previous executable image.
3226 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3230 @kindex set follow-exec-mode
3231 @item set follow-exec-mode @var{mode}
3233 Set debugger response to a program call of @code{exec}. An
3234 @code{exec} call replaces the program image of a process.
3236 @code{follow-exec-mode} can be:
3240 @value{GDBN} creates a new inferior and rebinds the process to this
3241 new inferior. The program the process was running before the
3242 @code{exec} call can be restarted afterwards by restarting the
3248 (@value{GDBP}) info inferiors
3250 Id Description Executable
3253 process 12020 is executing new program: prog2
3254 Program exited normally.
3255 (@value{GDBP}) info inferiors
3256 Id Description Executable
3262 @value{GDBN} keeps the process bound to the same inferior. The new
3263 executable image replaces the previous executable loaded in the
3264 inferior. Restarting the inferior after the @code{exec} call, with
3265 e.g., the @code{run} command, restarts the executable the process was
3266 running after the @code{exec} call. This is the default mode.
3271 (@value{GDBP}) info inferiors
3272 Id Description Executable
3275 process 12020 is executing new program: prog2
3276 Program exited normally.
3277 (@value{GDBP}) info inferiors
3278 Id Description Executable
3285 You can use the @code{catch} command to make @value{GDBN} stop whenever
3286 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3287 Catchpoints, ,Setting Catchpoints}.
3289 @node Checkpoint/Restart
3290 @section Setting a @emph{Bookmark} to Return to Later
3295 @cindex snapshot of a process
3296 @cindex rewind program state
3298 On certain operating systems@footnote{Currently, only
3299 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3300 program's state, called a @dfn{checkpoint}, and come back to it
3303 Returning to a checkpoint effectively undoes everything that has
3304 happened in the program since the @code{checkpoint} was saved. This
3305 includes changes in memory, registers, and even (within some limits)
3306 system state. Effectively, it is like going back in time to the
3307 moment when the checkpoint was saved.
3309 Thus, if you're stepping thru a program and you think you're
3310 getting close to the point where things go wrong, you can save
3311 a checkpoint. Then, if you accidentally go too far and miss
3312 the critical statement, instead of having to restart your program
3313 from the beginning, you can just go back to the checkpoint and
3314 start again from there.
3316 This can be especially useful if it takes a lot of time or
3317 steps to reach the point where you think the bug occurs.
3319 To use the @code{checkpoint}/@code{restart} method of debugging:
3324 Save a snapshot of the debugged program's current execution state.
3325 The @code{checkpoint} command takes no arguments, but each checkpoint
3326 is assigned a small integer id, similar to a breakpoint id.
3328 @kindex info checkpoints
3329 @item info checkpoints
3330 List the checkpoints that have been saved in the current debugging
3331 session. For each checkpoint, the following information will be
3338 @item Source line, or label
3341 @kindex restart @var{checkpoint-id}
3342 @item restart @var{checkpoint-id}
3343 Restore the program state that was saved as checkpoint number
3344 @var{checkpoint-id}. All program variables, registers, stack frames
3345 etc.@: will be returned to the values that they had when the checkpoint
3346 was saved. In essence, gdb will ``wind back the clock'' to the point
3347 in time when the checkpoint was saved.
3349 Note that breakpoints, @value{GDBN} variables, command history etc.
3350 are not affected by restoring a checkpoint. In general, a checkpoint
3351 only restores things that reside in the program being debugged, not in
3354 @kindex delete checkpoint @var{checkpoint-id}
3355 @item delete checkpoint @var{checkpoint-id}
3356 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3360 Returning to a previously saved checkpoint will restore the user state
3361 of the program being debugged, plus a significant subset of the system
3362 (OS) state, including file pointers. It won't ``un-write'' data from
3363 a file, but it will rewind the file pointer to the previous location,
3364 so that the previously written data can be overwritten. For files
3365 opened in read mode, the pointer will also be restored so that the
3366 previously read data can be read again.
3368 Of course, characters that have been sent to a printer (or other
3369 external device) cannot be ``snatched back'', and characters received
3370 from eg.@: a serial device can be removed from internal program buffers,
3371 but they cannot be ``pushed back'' into the serial pipeline, ready to
3372 be received again. Similarly, the actual contents of files that have
3373 been changed cannot be restored (at this time).
3375 However, within those constraints, you actually can ``rewind'' your
3376 program to a previously saved point in time, and begin debugging it
3377 again --- and you can change the course of events so as to debug a
3378 different execution path this time.
3380 @cindex checkpoints and process id
3381 Finally, there is one bit of internal program state that will be
3382 different when you return to a checkpoint --- the program's process
3383 id. Each checkpoint will have a unique process id (or @var{pid}),
3384 and each will be different from the program's original @var{pid}.
3385 If your program has saved a local copy of its process id, this could
3386 potentially pose a problem.
3388 @subsection A Non-obvious Benefit of Using Checkpoints
3390 On some systems such as @sc{gnu}/Linux, address space randomization
3391 is performed on new processes for security reasons. This makes it
3392 difficult or impossible to set a breakpoint, or watchpoint, on an
3393 absolute address if you have to restart the program, since the
3394 absolute location of a symbol will change from one execution to the
3397 A checkpoint, however, is an @emph{identical} copy of a process.
3398 Therefore if you create a checkpoint at (eg.@:) the start of main,
3399 and simply return to that checkpoint instead of restarting the
3400 process, you can avoid the effects of address randomization and
3401 your symbols will all stay in the same place.
3404 @chapter Stopping and Continuing
3406 The principal purposes of using a debugger are so that you can stop your
3407 program before it terminates; or so that, if your program runs into
3408 trouble, you can investigate and find out why.
3410 Inside @value{GDBN}, your program may stop for any of several reasons,
3411 such as a signal, a breakpoint, or reaching a new line after a
3412 @value{GDBN} command such as @code{step}. You may then examine and
3413 change variables, set new breakpoints or remove old ones, and then
3414 continue execution. Usually, the messages shown by @value{GDBN} provide
3415 ample explanation of the status of your program---but you can also
3416 explicitly request this information at any time.
3419 @kindex info program
3421 Display information about the status of your program: whether it is
3422 running or not, what process it is, and why it stopped.
3426 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3427 * Continuing and Stepping:: Resuming execution
3428 * Skipping Over Functions and Files::
3429 Skipping over functions and files
3431 * Thread Stops:: Stopping and starting multi-thread programs
3435 @section Breakpoints, Watchpoints, and Catchpoints
3438 A @dfn{breakpoint} makes your program stop whenever a certain point in
3439 the program is reached. For each breakpoint, you can add conditions to
3440 control in finer detail whether your program stops. You can set
3441 breakpoints with the @code{break} command and its variants (@pxref{Set
3442 Breaks, ,Setting Breakpoints}), to specify the place where your program
3443 should stop by line number, function name or exact address in the
3446 On some systems, you can set breakpoints in shared libraries before
3447 the executable is run. There is a minor limitation on HP-UX systems:
3448 you must wait until the executable is run in order to set breakpoints
3449 in shared library routines that are not called directly by the program
3450 (for example, routines that are arguments in a @code{pthread_create}
3454 @cindex data breakpoints
3455 @cindex memory tracing
3456 @cindex breakpoint on memory address
3457 @cindex breakpoint on variable modification
3458 A @dfn{watchpoint} is a special breakpoint that stops your program
3459 when the value of an expression changes. The expression may be a value
3460 of a variable, or it could involve values of one or more variables
3461 combined by operators, such as @samp{a + b}. This is sometimes called
3462 @dfn{data breakpoints}. You must use a different command to set
3463 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3464 from that, you can manage a watchpoint like any other breakpoint: you
3465 enable, disable, and delete both breakpoints and watchpoints using the
3468 You can arrange to have values from your program displayed automatically
3469 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3473 @cindex breakpoint on events
3474 A @dfn{catchpoint} is another special breakpoint that stops your program
3475 when a certain kind of event occurs, such as the throwing of a C@t{++}
3476 exception or the loading of a library. As with watchpoints, you use a
3477 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3478 Catchpoints}), but aside from that, you can manage a catchpoint like any
3479 other breakpoint. (To stop when your program receives a signal, use the
3480 @code{handle} command; see @ref{Signals, ,Signals}.)
3482 @cindex breakpoint numbers
3483 @cindex numbers for breakpoints
3484 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3485 catchpoint when you create it; these numbers are successive integers
3486 starting with one. In many of the commands for controlling various
3487 features of breakpoints you use the breakpoint number to say which
3488 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3489 @dfn{disabled}; if disabled, it has no effect on your program until you
3492 @cindex breakpoint ranges
3493 @cindex ranges of breakpoints
3494 Some @value{GDBN} commands accept a range of breakpoints on which to
3495 operate. A breakpoint range is either a single breakpoint number, like
3496 @samp{5}, or two such numbers, in increasing order, separated by a
3497 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3498 all breakpoints in that range are operated on.
3501 * Set Breaks:: Setting breakpoints
3502 * Set Watchpoints:: Setting watchpoints
3503 * Set Catchpoints:: Setting catchpoints
3504 * Delete Breaks:: Deleting breakpoints
3505 * Disabling:: Disabling breakpoints
3506 * Conditions:: Break conditions
3507 * Break Commands:: Breakpoint command lists
3508 * Dynamic Printf:: Dynamic printf
3509 * Save Breakpoints:: How to save breakpoints in a file
3510 * Static Probe Points:: Listing static probe points
3511 * Error in Breakpoints:: ``Cannot insert breakpoints''
3512 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3516 @subsection Setting Breakpoints
3518 @c FIXME LMB what does GDB do if no code on line of breakpt?
3519 @c consider in particular declaration with/without initialization.
3521 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3524 @kindex b @r{(@code{break})}
3525 @vindex $bpnum@r{, convenience variable}
3526 @cindex latest breakpoint
3527 Breakpoints are set with the @code{break} command (abbreviated
3528 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3529 number of the breakpoint you've set most recently; see @ref{Convenience
3530 Vars,, Convenience Variables}, for a discussion of what you can do with
3531 convenience variables.
3534 @item break @var{location}
3535 Set a breakpoint at the given @var{location}, which can specify a
3536 function name, a line number, or an address of an instruction.
3537 (@xref{Specify Location}, for a list of all the possible ways to
3538 specify a @var{location}.) The breakpoint will stop your program just
3539 before it executes any of the code in the specified @var{location}.
3541 When using source languages that permit overloading of symbols, such as
3542 C@t{++}, a function name may refer to more than one possible place to break.
3543 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3546 It is also possible to insert a breakpoint that will stop the program
3547 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3548 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3551 When called without any arguments, @code{break} sets a breakpoint at
3552 the next instruction to be executed in the selected stack frame
3553 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3554 innermost, this makes your program stop as soon as control
3555 returns to that frame. This is similar to the effect of a
3556 @code{finish} command in the frame inside the selected frame---except
3557 that @code{finish} does not leave an active breakpoint. If you use
3558 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3559 the next time it reaches the current location; this may be useful
3562 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3563 least one instruction has been executed. If it did not do this, you
3564 would be unable to proceed past a breakpoint without first disabling the
3565 breakpoint. This rule applies whether or not the breakpoint already
3566 existed when your program stopped.
3568 @item break @dots{} if @var{cond}
3569 Set a breakpoint with condition @var{cond}; evaluate the expression
3570 @var{cond} each time the breakpoint is reached, and stop only if the
3571 value is nonzero---that is, if @var{cond} evaluates as true.
3572 @samp{@dots{}} stands for one of the possible arguments described
3573 above (or no argument) specifying where to break. @xref{Conditions,
3574 ,Break Conditions}, for more information on breakpoint conditions.
3577 @item tbreak @var{args}
3578 Set a breakpoint enabled only for one stop. The @var{args} are the
3579 same as for the @code{break} command, and the breakpoint is set in the same
3580 way, but the breakpoint is automatically deleted after the first time your
3581 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3584 @cindex hardware breakpoints
3585 @item hbreak @var{args}
3586 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3587 @code{break} command and the breakpoint is set in the same way, but the
3588 breakpoint requires hardware support and some target hardware may not
3589 have this support. The main purpose of this is EPROM/ROM code
3590 debugging, so you can set a breakpoint at an instruction without
3591 changing the instruction. This can be used with the new trap-generation
3592 provided by SPARClite DSU and most x86-based targets. These targets
3593 will generate traps when a program accesses some data or instruction
3594 address that is assigned to the debug registers. However the hardware
3595 breakpoint registers can take a limited number of breakpoints. For
3596 example, on the DSU, only two data breakpoints can be set at a time, and
3597 @value{GDBN} will reject this command if more than two are used. Delete
3598 or disable unused hardware breakpoints before setting new ones
3599 (@pxref{Disabling, ,Disabling Breakpoints}).
3600 @xref{Conditions, ,Break Conditions}.
3601 For remote targets, you can restrict the number of hardware
3602 breakpoints @value{GDBN} will use, see @ref{set remote
3603 hardware-breakpoint-limit}.
3606 @item thbreak @var{args}
3607 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3608 are the same as for the @code{hbreak} command and the breakpoint is set in
3609 the same way. However, like the @code{tbreak} command,
3610 the breakpoint is automatically deleted after the
3611 first time your program stops there. Also, like the @code{hbreak}
3612 command, the breakpoint requires hardware support and some target hardware
3613 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3614 See also @ref{Conditions, ,Break Conditions}.
3617 @cindex regular expression
3618 @cindex breakpoints at functions matching a regexp
3619 @cindex set breakpoints in many functions
3620 @item rbreak @var{regex}
3621 Set breakpoints on all functions matching the regular expression
3622 @var{regex}. This command sets an unconditional breakpoint on all
3623 matches, printing a list of all breakpoints it set. Once these
3624 breakpoints are set, they are treated just like the breakpoints set with
3625 the @code{break} command. You can delete them, disable them, or make
3626 them conditional the same way as any other breakpoint.
3628 The syntax of the regular expression is the standard one used with tools
3629 like @file{grep}. Note that this is different from the syntax used by
3630 shells, so for instance @code{foo*} matches all functions that include
3631 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3632 @code{.*} leading and trailing the regular expression you supply, so to
3633 match only functions that begin with @code{foo}, use @code{^foo}.
3635 @cindex non-member C@t{++} functions, set breakpoint in
3636 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3637 breakpoints on overloaded functions that are not members of any special
3640 @cindex set breakpoints on all functions
3641 The @code{rbreak} command can be used to set breakpoints in
3642 @strong{all} the functions in a program, like this:
3645 (@value{GDBP}) rbreak .
3648 @item rbreak @var{file}:@var{regex}
3649 If @code{rbreak} is called with a filename qualification, it limits
3650 the search for functions matching the given regular expression to the
3651 specified @var{file}. This can be used, for example, to set breakpoints on
3652 every function in a given file:
3655 (@value{GDBP}) rbreak file.c:.
3658 The colon separating the filename qualifier from the regex may
3659 optionally be surrounded by spaces.
3661 @kindex info breakpoints
3662 @cindex @code{$_} and @code{info breakpoints}
3663 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3664 @itemx info break @r{[}@var{n}@dots{}@r{]}
3665 Print a table of all breakpoints, watchpoints, and catchpoints set and
3666 not deleted. Optional argument @var{n} means print information only
3667 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3668 For each breakpoint, following columns are printed:
3671 @item Breakpoint Numbers
3673 Breakpoint, watchpoint, or catchpoint.
3675 Whether the breakpoint is marked to be disabled or deleted when hit.
3676 @item Enabled or Disabled
3677 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3678 that are not enabled.
3680 Where the breakpoint is in your program, as a memory address. For a
3681 pending breakpoint whose address is not yet known, this field will
3682 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3683 library that has the symbol or line referred by breakpoint is loaded.
3684 See below for details. A breakpoint with several locations will
3685 have @samp{<MULTIPLE>} in this field---see below for details.
3687 Where the breakpoint is in the source for your program, as a file and
3688 line number. For a pending breakpoint, the original string passed to
3689 the breakpoint command will be listed as it cannot be resolved until
3690 the appropriate shared library is loaded in the future.
3694 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3695 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3696 @value{GDBN} on the host's side. If it is ``target'', then the condition
3697 is evaluated by the target. The @code{info break} command shows
3698 the condition on the line following the affected breakpoint, together with
3699 its condition evaluation mode in between parentheses.
3701 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3702 allowed to have a condition specified for it. The condition is not parsed for
3703 validity until a shared library is loaded that allows the pending
3704 breakpoint to resolve to a valid location.
3707 @code{info break} with a breakpoint
3708 number @var{n} as argument lists only that breakpoint. The
3709 convenience variable @code{$_} and the default examining-address for
3710 the @code{x} command are set to the address of the last breakpoint
3711 listed (@pxref{Memory, ,Examining Memory}).
3714 @code{info break} displays a count of the number of times the breakpoint
3715 has been hit. This is especially useful in conjunction with the
3716 @code{ignore} command. You can ignore a large number of breakpoint
3717 hits, look at the breakpoint info to see how many times the breakpoint
3718 was hit, and then run again, ignoring one less than that number. This
3719 will get you quickly to the last hit of that breakpoint.
3722 For a breakpoints with an enable count (xref) greater than 1,
3723 @code{info break} also displays that count.
3727 @value{GDBN} allows you to set any number of breakpoints at the same place in
3728 your program. There is nothing silly or meaningless about this. When
3729 the breakpoints are conditional, this is even useful
3730 (@pxref{Conditions, ,Break Conditions}).
3732 @cindex multiple locations, breakpoints
3733 @cindex breakpoints, multiple locations
3734 It is possible that a breakpoint corresponds to several locations
3735 in your program. Examples of this situation are:
3739 Multiple functions in the program may have the same name.
3742 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3743 instances of the function body, used in different cases.
3746 For a C@t{++} template function, a given line in the function can
3747 correspond to any number of instantiations.
3750 For an inlined function, a given source line can correspond to
3751 several places where that function is inlined.
3754 In all those cases, @value{GDBN} will insert a breakpoint at all
3755 the relevant locations.
3757 A breakpoint with multiple locations is displayed in the breakpoint
3758 table using several rows---one header row, followed by one row for
3759 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3760 address column. The rows for individual locations contain the actual
3761 addresses for locations, and show the functions to which those
3762 locations belong. The number column for a location is of the form
3763 @var{breakpoint-number}.@var{location-number}.
3768 Num Type Disp Enb Address What
3769 1 breakpoint keep y <MULTIPLE>
3771 breakpoint already hit 1 time
3772 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3773 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3776 Each location can be individually enabled or disabled by passing
3777 @var{breakpoint-number}.@var{location-number} as argument to the
3778 @code{enable} and @code{disable} commands. Note that you cannot
3779 delete the individual locations from the list, you can only delete the
3780 entire list of locations that belong to their parent breakpoint (with
3781 the @kbd{delete @var{num}} command, where @var{num} is the number of
3782 the parent breakpoint, 1 in the above example). Disabling or enabling
3783 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3784 that belong to that breakpoint.
3786 @cindex pending breakpoints
3787 It's quite common to have a breakpoint inside a shared library.
3788 Shared libraries can be loaded and unloaded explicitly,
3789 and possibly repeatedly, as the program is executed. To support
3790 this use case, @value{GDBN} updates breakpoint locations whenever
3791 any shared library is loaded or unloaded. Typically, you would
3792 set a breakpoint in a shared library at the beginning of your
3793 debugging session, when the library is not loaded, and when the
3794 symbols from the library are not available. When you try to set
3795 breakpoint, @value{GDBN} will ask you if you want to set
3796 a so called @dfn{pending breakpoint}---breakpoint whose address
3797 is not yet resolved.
3799 After the program is run, whenever a new shared library is loaded,
3800 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3801 shared library contains the symbol or line referred to by some
3802 pending breakpoint, that breakpoint is resolved and becomes an
3803 ordinary breakpoint. When a library is unloaded, all breakpoints
3804 that refer to its symbols or source lines become pending again.
3806 This logic works for breakpoints with multiple locations, too. For
3807 example, if you have a breakpoint in a C@t{++} template function, and
3808 a newly loaded shared library has an instantiation of that template,
3809 a new location is added to the list of locations for the breakpoint.
3811 Except for having unresolved address, pending breakpoints do not
3812 differ from regular breakpoints. You can set conditions or commands,
3813 enable and disable them and perform other breakpoint operations.
3815 @value{GDBN} provides some additional commands for controlling what
3816 happens when the @samp{break} command cannot resolve breakpoint
3817 address specification to an address:
3819 @kindex set breakpoint pending
3820 @kindex show breakpoint pending
3822 @item set breakpoint pending auto
3823 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3824 location, it queries you whether a pending breakpoint should be created.
3826 @item set breakpoint pending on
3827 This indicates that an unrecognized breakpoint location should automatically
3828 result in a pending breakpoint being created.
3830 @item set breakpoint pending off
3831 This indicates that pending breakpoints are not to be created. Any
3832 unrecognized breakpoint location results in an error. This setting does
3833 not affect any pending breakpoints previously created.
3835 @item show breakpoint pending
3836 Show the current behavior setting for creating pending breakpoints.
3839 The settings above only affect the @code{break} command and its
3840 variants. Once breakpoint is set, it will be automatically updated
3841 as shared libraries are loaded and unloaded.
3843 @cindex automatic hardware breakpoints
3844 For some targets, @value{GDBN} can automatically decide if hardware or
3845 software breakpoints should be used, depending on whether the
3846 breakpoint address is read-only or read-write. This applies to
3847 breakpoints set with the @code{break} command as well as to internal
3848 breakpoints set by commands like @code{next} and @code{finish}. For
3849 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3852 You can control this automatic behaviour with the following commands::
3854 @kindex set breakpoint auto-hw
3855 @kindex show breakpoint auto-hw
3857 @item set breakpoint auto-hw on
3858 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3859 will try to use the target memory map to decide if software or hardware
3860 breakpoint must be used.
3862 @item set breakpoint auto-hw off
3863 This indicates @value{GDBN} should not automatically select breakpoint
3864 type. If the target provides a memory map, @value{GDBN} will warn when
3865 trying to set software breakpoint at a read-only address.
3868 @value{GDBN} normally implements breakpoints by replacing the program code
3869 at the breakpoint address with a special instruction, which, when
3870 executed, given control to the debugger. By default, the program
3871 code is so modified only when the program is resumed. As soon as
3872 the program stops, @value{GDBN} restores the original instructions. This
3873 behaviour guards against leaving breakpoints inserted in the
3874 target should gdb abrubptly disconnect. However, with slow remote
3875 targets, inserting and removing breakpoint can reduce the performance.
3876 This behavior can be controlled with the following commands::
3878 @kindex set breakpoint always-inserted
3879 @kindex show breakpoint always-inserted
3881 @item set breakpoint always-inserted off
3882 All breakpoints, including newly added by the user, are inserted in
3883 the target only when the target is resumed. All breakpoints are
3884 removed from the target when it stops. This is the default mode.
3886 @item set breakpoint always-inserted on
3887 Causes all breakpoints to be inserted in the target at all times. If
3888 the user adds a new breakpoint, or changes an existing breakpoint, the
3889 breakpoints in the target are updated immediately. A breakpoint is
3890 removed from the target only when breakpoint itself is deleted.
3893 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3894 when a breakpoint breaks. If the condition is true, then the process being
3895 debugged stops, otherwise the process is resumed.
3897 If the target supports evaluating conditions on its end, @value{GDBN} may
3898 download the breakpoint, together with its conditions, to it.
3900 This feature can be controlled via the following commands:
3902 @kindex set breakpoint condition-evaluation
3903 @kindex show breakpoint condition-evaluation
3905 @item set breakpoint condition-evaluation host
3906 This option commands @value{GDBN} to evaluate the breakpoint
3907 conditions on the host's side. Unconditional breakpoints are sent to
3908 the target which in turn receives the triggers and reports them back to GDB
3909 for condition evaluation. This is the standard evaluation mode.
3911 @item set breakpoint condition-evaluation target
3912 This option commands @value{GDBN} to download breakpoint conditions
3913 to the target at the moment of their insertion. The target
3914 is responsible for evaluating the conditional expression and reporting
3915 breakpoint stop events back to @value{GDBN} whenever the condition
3916 is true. Due to limitations of target-side evaluation, some conditions
3917 cannot be evaluated there, e.g., conditions that depend on local data
3918 that is only known to the host. Examples include
3919 conditional expressions involving convenience variables, complex types
3920 that cannot be handled by the agent expression parser and expressions
3921 that are too long to be sent over to the target, specially when the
3922 target is a remote system. In these cases, the conditions will be
3923 evaluated by @value{GDBN}.
3925 @item set breakpoint condition-evaluation auto
3926 This is the default mode. If the target supports evaluating breakpoint
3927 conditions on its end, @value{GDBN} will download breakpoint conditions to
3928 the target (limitations mentioned previously apply). If the target does
3929 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3930 to evaluating all these conditions on the host's side.
3934 @cindex negative breakpoint numbers
3935 @cindex internal @value{GDBN} breakpoints
3936 @value{GDBN} itself sometimes sets breakpoints in your program for
3937 special purposes, such as proper handling of @code{longjmp} (in C
3938 programs). These internal breakpoints are assigned negative numbers,
3939 starting with @code{-1}; @samp{info breakpoints} does not display them.
3940 You can see these breakpoints with the @value{GDBN} maintenance command
3941 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3944 @node Set Watchpoints
3945 @subsection Setting Watchpoints
3947 @cindex setting watchpoints
3948 You can use a watchpoint to stop execution whenever the value of an
3949 expression changes, without having to predict a particular place where
3950 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3951 The expression may be as simple as the value of a single variable, or
3952 as complex as many variables combined by operators. Examples include:
3956 A reference to the value of a single variable.
3959 An address cast to an appropriate data type. For example,
3960 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3961 address (assuming an @code{int} occupies 4 bytes).
3964 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3965 expression can use any operators valid in the program's native
3966 language (@pxref{Languages}).
3969 You can set a watchpoint on an expression even if the expression can
3970 not be evaluated yet. For instance, you can set a watchpoint on
3971 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3972 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3973 the expression produces a valid value. If the expression becomes
3974 valid in some other way than changing a variable (e.g.@: if the memory
3975 pointed to by @samp{*global_ptr} becomes readable as the result of a
3976 @code{malloc} call), @value{GDBN} may not stop until the next time
3977 the expression changes.
3979 @cindex software watchpoints
3980 @cindex hardware watchpoints
3981 Depending on your system, watchpoints may be implemented in software or
3982 hardware. @value{GDBN} does software watchpointing by single-stepping your
3983 program and testing the variable's value each time, which is hundreds of
3984 times slower than normal execution. (But this may still be worth it, to
3985 catch errors where you have no clue what part of your program is the
3988 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3989 x86-based targets, @value{GDBN} includes support for hardware
3990 watchpoints, which do not slow down the running of your program.
3994 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3995 Set a watchpoint for an expression. @value{GDBN} will break when the
3996 expression @var{expr} is written into by the program and its value
3997 changes. The simplest (and the most popular) use of this command is
3998 to watch the value of a single variable:
4001 (@value{GDBP}) watch foo
4004 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
4005 argument, @value{GDBN} breaks only when the thread identified by
4006 @var{threadnum} changes the value of @var{expr}. If any other threads
4007 change the value of @var{expr}, @value{GDBN} will not break. Note
4008 that watchpoints restricted to a single thread in this way only work
4009 with Hardware Watchpoints.
4011 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4012 (see below). The @code{-location} argument tells @value{GDBN} to
4013 instead watch the memory referred to by @var{expr}. In this case,
4014 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4015 and watch the memory at that address. The type of the result is used
4016 to determine the size of the watched memory. If the expression's
4017 result does not have an address, then @value{GDBN} will print an
4020 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4021 of masked watchpoints, if the current architecture supports this
4022 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4023 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4024 to an address to watch. The mask specifies that some bits of an address
4025 (the bits which are reset in the mask) should be ignored when matching
4026 the address accessed by the inferior against the watchpoint address.
4027 Thus, a masked watchpoint watches many addresses simultaneously---those
4028 addresses whose unmasked bits are identical to the unmasked bits in the
4029 watchpoint address. The @code{mask} argument implies @code{-location}.
4033 (@value{GDBP}) watch foo mask 0xffff00ff
4034 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4038 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4039 Set a watchpoint that will break when the value of @var{expr} is read
4043 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4044 Set a watchpoint that will break when @var{expr} is either read from
4045 or written into by the program.
4047 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4048 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4049 This command prints a list of watchpoints, using the same format as
4050 @code{info break} (@pxref{Set Breaks}).
4053 If you watch for a change in a numerically entered address you need to
4054 dereference it, as the address itself is just a constant number which will
4055 never change. @value{GDBN} refuses to create a watchpoint that watches
4056 a never-changing value:
4059 (@value{GDBP}) watch 0x600850
4060 Cannot watch constant value 0x600850.
4061 (@value{GDBP}) watch *(int *) 0x600850
4062 Watchpoint 1: *(int *) 6293584
4065 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4066 watchpoints execute very quickly, and the debugger reports a change in
4067 value at the exact instruction where the change occurs. If @value{GDBN}
4068 cannot set a hardware watchpoint, it sets a software watchpoint, which
4069 executes more slowly and reports the change in value at the next
4070 @emph{statement}, not the instruction, after the change occurs.
4072 @cindex use only software watchpoints
4073 You can force @value{GDBN} to use only software watchpoints with the
4074 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4075 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4076 the underlying system supports them. (Note that hardware-assisted
4077 watchpoints that were set @emph{before} setting
4078 @code{can-use-hw-watchpoints} to zero will still use the hardware
4079 mechanism of watching expression values.)
4082 @item set can-use-hw-watchpoints
4083 @kindex set can-use-hw-watchpoints
4084 Set whether or not to use hardware watchpoints.
4086 @item show can-use-hw-watchpoints
4087 @kindex show can-use-hw-watchpoints
4088 Show the current mode of using hardware watchpoints.
4091 For remote targets, you can restrict the number of hardware
4092 watchpoints @value{GDBN} will use, see @ref{set remote
4093 hardware-breakpoint-limit}.
4095 When you issue the @code{watch} command, @value{GDBN} reports
4098 Hardware watchpoint @var{num}: @var{expr}
4102 if it was able to set a hardware watchpoint.
4104 Currently, the @code{awatch} and @code{rwatch} commands can only set
4105 hardware watchpoints, because accesses to data that don't change the
4106 value of the watched expression cannot be detected without examining
4107 every instruction as it is being executed, and @value{GDBN} does not do
4108 that currently. If @value{GDBN} finds that it is unable to set a
4109 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4110 will print a message like this:
4113 Expression cannot be implemented with read/access watchpoint.
4116 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4117 data type of the watched expression is wider than what a hardware
4118 watchpoint on the target machine can handle. For example, some systems
4119 can only watch regions that are up to 4 bytes wide; on such systems you
4120 cannot set hardware watchpoints for an expression that yields a
4121 double-precision floating-point number (which is typically 8 bytes
4122 wide). As a work-around, it might be possible to break the large region
4123 into a series of smaller ones and watch them with separate watchpoints.
4125 If you set too many hardware watchpoints, @value{GDBN} might be unable
4126 to insert all of them when you resume the execution of your program.
4127 Since the precise number of active watchpoints is unknown until such
4128 time as the program is about to be resumed, @value{GDBN} might not be
4129 able to warn you about this when you set the watchpoints, and the
4130 warning will be printed only when the program is resumed:
4133 Hardware watchpoint @var{num}: Could not insert watchpoint
4137 If this happens, delete or disable some of the watchpoints.
4139 Watching complex expressions that reference many variables can also
4140 exhaust the resources available for hardware-assisted watchpoints.
4141 That's because @value{GDBN} needs to watch every variable in the
4142 expression with separately allocated resources.
4144 If you call a function interactively using @code{print} or @code{call},
4145 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4146 kind of breakpoint or the call completes.
4148 @value{GDBN} automatically deletes watchpoints that watch local
4149 (automatic) variables, or expressions that involve such variables, when
4150 they go out of scope, that is, when the execution leaves the block in
4151 which these variables were defined. In particular, when the program
4152 being debugged terminates, @emph{all} local variables go out of scope,
4153 and so only watchpoints that watch global variables remain set. If you
4154 rerun the program, you will need to set all such watchpoints again. One
4155 way of doing that would be to set a code breakpoint at the entry to the
4156 @code{main} function and when it breaks, set all the watchpoints.
4158 @cindex watchpoints and threads
4159 @cindex threads and watchpoints
4160 In multi-threaded programs, watchpoints will detect changes to the
4161 watched expression from every thread.
4164 @emph{Warning:} In multi-threaded programs, software watchpoints
4165 have only limited usefulness. If @value{GDBN} creates a software
4166 watchpoint, it can only watch the value of an expression @emph{in a
4167 single thread}. If you are confident that the expression can only
4168 change due to the current thread's activity (and if you are also
4169 confident that no other thread can become current), then you can use
4170 software watchpoints as usual. However, @value{GDBN} may not notice
4171 when a non-current thread's activity changes the expression. (Hardware
4172 watchpoints, in contrast, watch an expression in all threads.)
4175 @xref{set remote hardware-watchpoint-limit}.
4177 @node Set Catchpoints
4178 @subsection Setting Catchpoints
4179 @cindex catchpoints, setting
4180 @cindex exception handlers
4181 @cindex event handling
4183 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4184 kinds of program events, such as C@t{++} exceptions or the loading of a
4185 shared library. Use the @code{catch} command to set a catchpoint.
4189 @item catch @var{event}
4190 Stop when @var{event} occurs. The @var{event} can be any of the following:
4193 @item throw @r{[}@var{regexp}@r{]}
4194 @itemx rethrow @r{[}@var{regexp}@r{]}
4195 @itemx catch @r{[}@var{regexp}@r{]}
4197 @kindex catch rethrow
4199 @cindex stop on C@t{++} exceptions
4200 The throwing, re-throwing, or catching of a C@t{++} exception.
4202 If @var{regexp} is given, then only exceptions whose type matches the
4203 regular expression will be caught.
4205 @vindex $_exception@r{, convenience variable}
4206 The convenience variable @code{$_exception} is available at an
4207 exception-related catchpoint, on some systems. This holds the
4208 exception being thrown.
4210 There are currently some limitations to C@t{++} exception handling in
4215 The support for these commands is system-dependent. Currently, only
4216 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4220 The regular expression feature and the @code{$_exception} convenience
4221 variable rely on the presence of some SDT probes in @code{libstdc++}.
4222 If these probes are not present, then these features cannot be used.
4223 These probes were first available in the GCC 4.8 release, but whether
4224 or not they are available in your GCC also depends on how it was
4228 The @code{$_exception} convenience variable is only valid at the
4229 instruction at which an exception-related catchpoint is set.
4232 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4233 location in the system library which implements runtime exception
4234 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4235 (@pxref{Selection}) to get to your code.
4238 If you call a function interactively, @value{GDBN} normally returns
4239 control to you when the function has finished executing. If the call
4240 raises an exception, however, the call may bypass the mechanism that
4241 returns control to you and cause your program either to abort or to
4242 simply continue running until it hits a breakpoint, catches a signal
4243 that @value{GDBN} is listening for, or exits. This is the case even if
4244 you set a catchpoint for the exception; catchpoints on exceptions are
4245 disabled within interactive calls. @xref{Calling}, for information on
4246 controlling this with @code{set unwind-on-terminating-exception}.
4249 You cannot raise an exception interactively.
4252 You cannot install an exception handler interactively.
4256 @kindex catch exception
4257 @cindex Ada exception catching
4258 @cindex catch Ada exceptions
4259 An Ada exception being raised. If an exception name is specified
4260 at the end of the command (eg @code{catch exception Program_Error}),
4261 the debugger will stop only when this specific exception is raised.
4262 Otherwise, the debugger stops execution when any Ada exception is raised.
4264 When inserting an exception catchpoint on a user-defined exception whose
4265 name is identical to one of the exceptions defined by the language, the
4266 fully qualified name must be used as the exception name. Otherwise,
4267 @value{GDBN} will assume that it should stop on the pre-defined exception
4268 rather than the user-defined one. For instance, assuming an exception
4269 called @code{Constraint_Error} is defined in package @code{Pck}, then
4270 the command to use to catch such exceptions is @kbd{catch exception
4271 Pck.Constraint_Error}.
4273 @item exception unhandled
4274 @kindex catch exception unhandled
4275 An exception that was raised but is not handled by the program.
4278 @kindex catch assert
4279 A failed Ada assertion.
4283 @cindex break on fork/exec
4284 A call to @code{exec}. This is currently only available for HP-UX
4288 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4289 @kindex catch syscall
4290 @cindex break on a system call.
4291 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4292 syscall is a mechanism for application programs to request a service
4293 from the operating system (OS) or one of the OS system services.
4294 @value{GDBN} can catch some or all of the syscalls issued by the
4295 debuggee, and show the related information for each syscall. If no
4296 argument is specified, calls to and returns from all system calls
4299 @var{name} can be any system call name that is valid for the
4300 underlying OS. Just what syscalls are valid depends on the OS. On
4301 GNU and Unix systems, you can find the full list of valid syscall
4302 names on @file{/usr/include/asm/unistd.h}.
4304 @c For MS-Windows, the syscall names and the corresponding numbers
4305 @c can be found, e.g., on this URL:
4306 @c http://www.metasploit.com/users/opcode/syscalls.html
4307 @c but we don't support Windows syscalls yet.
4309 Normally, @value{GDBN} knows in advance which syscalls are valid for
4310 each OS, so you can use the @value{GDBN} command-line completion
4311 facilities (@pxref{Completion,, command completion}) to list the
4314 You may also specify the system call numerically. A syscall's
4315 number is the value passed to the OS's syscall dispatcher to
4316 identify the requested service. When you specify the syscall by its
4317 name, @value{GDBN} uses its database of syscalls to convert the name
4318 into the corresponding numeric code, but using the number directly
4319 may be useful if @value{GDBN}'s database does not have the complete
4320 list of syscalls on your system (e.g., because @value{GDBN} lags
4321 behind the OS upgrades).
4323 The example below illustrates how this command works if you don't provide
4327 (@value{GDBP}) catch syscall
4328 Catchpoint 1 (syscall)
4330 Starting program: /tmp/catch-syscall
4332 Catchpoint 1 (call to syscall 'close'), \
4333 0xffffe424 in __kernel_vsyscall ()
4337 Catchpoint 1 (returned from syscall 'close'), \
4338 0xffffe424 in __kernel_vsyscall ()
4342 Here is an example of catching a system call by name:
4345 (@value{GDBP}) catch syscall chroot
4346 Catchpoint 1 (syscall 'chroot' [61])
4348 Starting program: /tmp/catch-syscall
4350 Catchpoint 1 (call to syscall 'chroot'), \
4351 0xffffe424 in __kernel_vsyscall ()
4355 Catchpoint 1 (returned from syscall 'chroot'), \
4356 0xffffe424 in __kernel_vsyscall ()
4360 An example of specifying a system call numerically. In the case
4361 below, the syscall number has a corresponding entry in the XML
4362 file, so @value{GDBN} finds its name and prints it:
4365 (@value{GDBP}) catch syscall 252
4366 Catchpoint 1 (syscall(s) 'exit_group')
4368 Starting program: /tmp/catch-syscall
4370 Catchpoint 1 (call to syscall 'exit_group'), \
4371 0xffffe424 in __kernel_vsyscall ()
4375 Program exited normally.
4379 However, there can be situations when there is no corresponding name
4380 in XML file for that syscall number. In this case, @value{GDBN} prints
4381 a warning message saying that it was not able to find the syscall name,
4382 but the catchpoint will be set anyway. See the example below:
4385 (@value{GDBP}) catch syscall 764
4386 warning: The number '764' does not represent a known syscall.
4387 Catchpoint 2 (syscall 764)
4391 If you configure @value{GDBN} using the @samp{--without-expat} option,
4392 it will not be able to display syscall names. Also, if your
4393 architecture does not have an XML file describing its system calls,
4394 you will not be able to see the syscall names. It is important to
4395 notice that these two features are used for accessing the syscall
4396 name database. In either case, you will see a warning like this:
4399 (@value{GDBP}) catch syscall
4400 warning: Could not open "syscalls/i386-linux.xml"
4401 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4402 GDB will not be able to display syscall names.
4403 Catchpoint 1 (syscall)
4407 Of course, the file name will change depending on your architecture and system.
4409 Still using the example above, you can also try to catch a syscall by its
4410 number. In this case, you would see something like:
4413 (@value{GDBP}) catch syscall 252
4414 Catchpoint 1 (syscall(s) 252)
4417 Again, in this case @value{GDBN} would not be able to display syscall's names.
4421 A call to @code{fork}. This is currently only available for HP-UX
4426 A call to @code{vfork}. This is currently only available for HP-UX
4429 @item load @r{[}regexp@r{]}
4430 @itemx unload @r{[}regexp@r{]}
4432 @kindex catch unload
4433 The loading or unloading of a shared library. If @var{regexp} is
4434 given, then the catchpoint will stop only if the regular expression
4435 matches one of the affected libraries.
4437 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4438 @kindex catch signal
4439 The delivery of a signal.
4441 With no arguments, this catchpoint will catch any signal that is not
4442 used internally by @value{GDBN}, specifically, all signals except
4443 @samp{SIGTRAP} and @samp{SIGINT}.
4445 With the argument @samp{all}, all signals, including those used by
4446 @value{GDBN}, will be caught. This argument cannot be used with other
4449 Otherwise, the arguments are a list of signal names as given to
4450 @code{handle} (@pxref{Signals}). Only signals specified in this list
4453 One reason that @code{catch signal} can be more useful than
4454 @code{handle} is that you can attach commands and conditions to the
4457 When a signal is caught by a catchpoint, the signal's @code{stop} and
4458 @code{print} settings, as specified by @code{handle}, are ignored.
4459 However, whether the signal is still delivered to the inferior depends
4460 on the @code{pass} setting; this can be changed in the catchpoint's
4465 @item tcatch @var{event}
4467 Set a catchpoint that is enabled only for one stop. The catchpoint is
4468 automatically deleted after the first time the event is caught.
4472 Use the @code{info break} command to list the current catchpoints.
4476 @subsection Deleting Breakpoints
4478 @cindex clearing breakpoints, watchpoints, catchpoints
4479 @cindex deleting breakpoints, watchpoints, catchpoints
4480 It is often necessary to eliminate a breakpoint, watchpoint, or
4481 catchpoint once it has done its job and you no longer want your program
4482 to stop there. This is called @dfn{deleting} the breakpoint. A
4483 breakpoint that has been deleted no longer exists; it is forgotten.
4485 With the @code{clear} command you can delete breakpoints according to
4486 where they are in your program. With the @code{delete} command you can
4487 delete individual breakpoints, watchpoints, or catchpoints by specifying
4488 their breakpoint numbers.
4490 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4491 automatically ignores breakpoints on the first instruction to be executed
4492 when you continue execution without changing the execution address.
4497 Delete any breakpoints at the next instruction to be executed in the
4498 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4499 the innermost frame is selected, this is a good way to delete a
4500 breakpoint where your program just stopped.
4502 @item clear @var{location}
4503 Delete any breakpoints set at the specified @var{location}.
4504 @xref{Specify Location}, for the various forms of @var{location}; the
4505 most useful ones are listed below:
4508 @item clear @var{function}
4509 @itemx clear @var{filename}:@var{function}
4510 Delete any breakpoints set at entry to the named @var{function}.
4512 @item clear @var{linenum}
4513 @itemx clear @var{filename}:@var{linenum}
4514 Delete any breakpoints set at or within the code of the specified
4515 @var{linenum} of the specified @var{filename}.
4518 @cindex delete breakpoints
4520 @kindex d @r{(@code{delete})}
4521 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4522 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4523 ranges specified as arguments. If no argument is specified, delete all
4524 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4525 confirm off}). You can abbreviate this command as @code{d}.
4529 @subsection Disabling Breakpoints
4531 @cindex enable/disable a breakpoint
4532 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4533 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4534 it had been deleted, but remembers the information on the breakpoint so
4535 that you can @dfn{enable} it again later.
4537 You disable and enable breakpoints, watchpoints, and catchpoints with
4538 the @code{enable} and @code{disable} commands, optionally specifying
4539 one or more breakpoint numbers as arguments. Use @code{info break} to
4540 print a list of all breakpoints, watchpoints, and catchpoints if you
4541 do not know which numbers to use.
4543 Disabling and enabling a breakpoint that has multiple locations
4544 affects all of its locations.
4546 A breakpoint, watchpoint, or catchpoint can have any of several
4547 different states of enablement:
4551 Enabled. The breakpoint stops your program. A breakpoint set
4552 with the @code{break} command starts out in this state.
4554 Disabled. The breakpoint has no effect on your program.
4556 Enabled once. The breakpoint stops your program, but then becomes
4559 Enabled for a count. The breakpoint stops your program for the next
4560 N times, then becomes disabled.
4562 Enabled for deletion. The breakpoint stops your program, but
4563 immediately after it does so it is deleted permanently. A breakpoint
4564 set with the @code{tbreak} command starts out in this state.
4567 You can use the following commands to enable or disable breakpoints,
4568 watchpoints, and catchpoints:
4572 @kindex dis @r{(@code{disable})}
4573 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4574 Disable the specified breakpoints---or all breakpoints, if none are
4575 listed. A disabled breakpoint has no effect but is not forgotten. All
4576 options such as ignore-counts, conditions and commands are remembered in
4577 case the breakpoint is enabled again later. You may abbreviate
4578 @code{disable} as @code{dis}.
4581 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4582 Enable the specified breakpoints (or all defined breakpoints). They
4583 become effective once again in stopping your program.
4585 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4586 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4587 of these breakpoints immediately after stopping your program.
4589 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4590 Enable the specified breakpoints temporarily. @value{GDBN} records
4591 @var{count} with each of the specified breakpoints, and decrements a
4592 breakpoint's count when it is hit. When any count reaches 0,
4593 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4594 count (@pxref{Conditions, ,Break Conditions}), that will be
4595 decremented to 0 before @var{count} is affected.
4597 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4598 Enable the specified breakpoints to work once, then die. @value{GDBN}
4599 deletes any of these breakpoints as soon as your program stops there.
4600 Breakpoints set by the @code{tbreak} command start out in this state.
4603 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4604 @c confusing: tbreak is also initially enabled.
4605 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4606 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4607 subsequently, they become disabled or enabled only when you use one of
4608 the commands above. (The command @code{until} can set and delete a
4609 breakpoint of its own, but it does not change the state of your other
4610 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4614 @subsection Break Conditions
4615 @cindex conditional breakpoints
4616 @cindex breakpoint conditions
4618 @c FIXME what is scope of break condition expr? Context where wanted?
4619 @c in particular for a watchpoint?
4620 The simplest sort of breakpoint breaks every time your program reaches a
4621 specified place. You can also specify a @dfn{condition} for a
4622 breakpoint. A condition is just a Boolean expression in your
4623 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4624 a condition evaluates the expression each time your program reaches it,
4625 and your program stops only if the condition is @emph{true}.
4627 This is the converse of using assertions for program validation; in that
4628 situation, you want to stop when the assertion is violated---that is,
4629 when the condition is false. In C, if you want to test an assertion expressed
4630 by the condition @var{assert}, you should set the condition
4631 @samp{! @var{assert}} on the appropriate breakpoint.
4633 Conditions are also accepted for watchpoints; you may not need them,
4634 since a watchpoint is inspecting the value of an expression anyhow---but
4635 it might be simpler, say, to just set a watchpoint on a variable name,
4636 and specify a condition that tests whether the new value is an interesting
4639 Break conditions can have side effects, and may even call functions in
4640 your program. This can be useful, for example, to activate functions
4641 that log program progress, or to use your own print functions to
4642 format special data structures. The effects are completely predictable
4643 unless there is another enabled breakpoint at the same address. (In
4644 that case, @value{GDBN} might see the other breakpoint first and stop your
4645 program without checking the condition of this one.) Note that
4646 breakpoint commands are usually more convenient and flexible than break
4648 purpose of performing side effects when a breakpoint is reached
4649 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4651 Breakpoint conditions can also be evaluated on the target's side if
4652 the target supports it. Instead of evaluating the conditions locally,
4653 @value{GDBN} encodes the expression into an agent expression
4654 (@pxref{Agent Expressions}) suitable for execution on the target,
4655 independently of @value{GDBN}. Global variables become raw memory
4656 locations, locals become stack accesses, and so forth.
4658 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4659 when its condition evaluates to true. This mechanism may provide faster
4660 response times depending on the performance characteristics of the target
4661 since it does not need to keep @value{GDBN} informed about
4662 every breakpoint trigger, even those with false conditions.
4664 Break conditions can be specified when a breakpoint is set, by using
4665 @samp{if} in the arguments to the @code{break} command. @xref{Set
4666 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4667 with the @code{condition} command.
4669 You can also use the @code{if} keyword with the @code{watch} command.
4670 The @code{catch} command does not recognize the @code{if} keyword;
4671 @code{condition} is the only way to impose a further condition on a
4676 @item condition @var{bnum} @var{expression}
4677 Specify @var{expression} as the break condition for breakpoint,
4678 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4679 breakpoint @var{bnum} stops your program only if the value of
4680 @var{expression} is true (nonzero, in C). When you use
4681 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4682 syntactic correctness, and to determine whether symbols in it have
4683 referents in the context of your breakpoint. If @var{expression} uses
4684 symbols not referenced in the context of the breakpoint, @value{GDBN}
4685 prints an error message:
4688 No symbol "foo" in current context.
4693 not actually evaluate @var{expression} at the time the @code{condition}
4694 command (or a command that sets a breakpoint with a condition, like
4695 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4697 @item condition @var{bnum}
4698 Remove the condition from breakpoint number @var{bnum}. It becomes
4699 an ordinary unconditional breakpoint.
4702 @cindex ignore count (of breakpoint)
4703 A special case of a breakpoint condition is to stop only when the
4704 breakpoint has been reached a certain number of times. This is so
4705 useful that there is a special way to do it, using the @dfn{ignore
4706 count} of the breakpoint. Every breakpoint has an ignore count, which
4707 is an integer. Most of the time, the ignore count is zero, and
4708 therefore has no effect. But if your program reaches a breakpoint whose
4709 ignore count is positive, then instead of stopping, it just decrements
4710 the ignore count by one and continues. As a result, if the ignore count
4711 value is @var{n}, the breakpoint does not stop the next @var{n} times
4712 your program reaches it.
4716 @item ignore @var{bnum} @var{count}
4717 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4718 The next @var{count} times the breakpoint is reached, your program's
4719 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4722 To make the breakpoint stop the next time it is reached, specify
4725 When you use @code{continue} to resume execution of your program from a
4726 breakpoint, you can specify an ignore count directly as an argument to
4727 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4728 Stepping,,Continuing and Stepping}.
4730 If a breakpoint has a positive ignore count and a condition, the
4731 condition is not checked. Once the ignore count reaches zero,
4732 @value{GDBN} resumes checking the condition.
4734 You could achieve the effect of the ignore count with a condition such
4735 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4736 is decremented each time. @xref{Convenience Vars, ,Convenience
4740 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4743 @node Break Commands
4744 @subsection Breakpoint Command Lists
4746 @cindex breakpoint commands
4747 You can give any breakpoint (or watchpoint or catchpoint) a series of
4748 commands to execute when your program stops due to that breakpoint. For
4749 example, you might want to print the values of certain expressions, or
4750 enable other breakpoints.
4754 @kindex end@r{ (breakpoint commands)}
4755 @item commands @r{[}@var{range}@dots{}@r{]}
4756 @itemx @dots{} @var{command-list} @dots{}
4758 Specify a list of commands for the given breakpoints. The commands
4759 themselves appear on the following lines. Type a line containing just
4760 @code{end} to terminate the commands.
4762 To remove all commands from a breakpoint, type @code{commands} and
4763 follow it immediately with @code{end}; that is, give no commands.
4765 With no argument, @code{commands} refers to the last breakpoint,
4766 watchpoint, or catchpoint set (not to the breakpoint most recently
4767 encountered). If the most recent breakpoints were set with a single
4768 command, then the @code{commands} will apply to all the breakpoints
4769 set by that command. This applies to breakpoints set by
4770 @code{rbreak}, and also applies when a single @code{break} command
4771 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4775 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4776 disabled within a @var{command-list}.
4778 You can use breakpoint commands to start your program up again. Simply
4779 use the @code{continue} command, or @code{step}, or any other command
4780 that resumes execution.
4782 Any other commands in the command list, after a command that resumes
4783 execution, are ignored. This is because any time you resume execution
4784 (even with a simple @code{next} or @code{step}), you may encounter
4785 another breakpoint---which could have its own command list, leading to
4786 ambiguities about which list to execute.
4789 If the first command you specify in a command list is @code{silent}, the
4790 usual message about stopping at a breakpoint is not printed. This may
4791 be desirable for breakpoints that are to print a specific message and
4792 then continue. If none of the remaining commands print anything, you
4793 see no sign that the breakpoint was reached. @code{silent} is
4794 meaningful only at the beginning of a breakpoint command list.
4796 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4797 print precisely controlled output, and are often useful in silent
4798 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4800 For example, here is how you could use breakpoint commands to print the
4801 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4807 printf "x is %d\n",x
4812 One application for breakpoint commands is to compensate for one bug so
4813 you can test for another. Put a breakpoint just after the erroneous line
4814 of code, give it a condition to detect the case in which something
4815 erroneous has been done, and give it commands to assign correct values
4816 to any variables that need them. End with the @code{continue} command
4817 so that your program does not stop, and start with the @code{silent}
4818 command so that no output is produced. Here is an example:
4829 @node Dynamic Printf
4830 @subsection Dynamic Printf
4832 @cindex dynamic printf
4834 The dynamic printf command @code{dprintf} combines a breakpoint with
4835 formatted printing of your program's data to give you the effect of
4836 inserting @code{printf} calls into your program on-the-fly, without
4837 having to recompile it.
4839 In its most basic form, the output goes to the GDB console. However,
4840 you can set the variable @code{dprintf-style} for alternate handling.
4841 For instance, you can ask to format the output by calling your
4842 program's @code{printf} function. This has the advantage that the
4843 characters go to the program's output device, so they can recorded in
4844 redirects to files and so forth.
4846 If you are doing remote debugging with a stub or agent, you can also
4847 ask to have the printf handled by the remote agent. In addition to
4848 ensuring that the output goes to the remote program's device along
4849 with any other output the program might produce, you can also ask that
4850 the dprintf remain active even after disconnecting from the remote
4851 target. Using the stub/agent is also more efficient, as it can do
4852 everything without needing to communicate with @value{GDBN}.
4856 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4857 Whenever execution reaches @var{location}, print the values of one or
4858 more @var{expressions} under the control of the string @var{template}.
4859 To print several values, separate them with commas.
4861 @item set dprintf-style @var{style}
4862 Set the dprintf output to be handled in one of several different
4863 styles enumerated below. A change of style affects all existing
4864 dynamic printfs immediately. (If you need individual control over the
4865 print commands, simply define normal breakpoints with
4866 explicitly-supplied command lists.)
4869 @kindex dprintf-style gdb
4870 Handle the output using the @value{GDBN} @code{printf} command.
4873 @kindex dprintf-style call
4874 Handle the output by calling a function in your program (normally
4878 @kindex dprintf-style agent
4879 Have the remote debugging agent (such as @code{gdbserver}) handle
4880 the output itself. This style is only available for agents that
4881 support running commands on the target.
4883 @item set dprintf-function @var{function}
4884 Set the function to call if the dprintf style is @code{call}. By
4885 default its value is @code{printf}. You may set it to any expression.
4886 that @value{GDBN} can evaluate to a function, as per the @code{call}
4889 @item set dprintf-channel @var{channel}
4890 Set a ``channel'' for dprintf. If set to a non-empty value,
4891 @value{GDBN} will evaluate it as an expression and pass the result as
4892 a first argument to the @code{dprintf-function}, in the manner of
4893 @code{fprintf} and similar functions. Otherwise, the dprintf format
4894 string will be the first argument, in the manner of @code{printf}.
4896 As an example, if you wanted @code{dprintf} output to go to a logfile
4897 that is a standard I/O stream assigned to the variable @code{mylog},
4898 you could do the following:
4901 (gdb) set dprintf-style call
4902 (gdb) set dprintf-function fprintf
4903 (gdb) set dprintf-channel mylog
4904 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4905 Dprintf 1 at 0x123456: file main.c, line 25.
4907 1 dprintf keep y 0x00123456 in main at main.c:25
4908 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4913 Note that the @code{info break} displays the dynamic printf commands
4914 as normal breakpoint commands; you can thus easily see the effect of
4915 the variable settings.
4917 @item set disconnected-dprintf on
4918 @itemx set disconnected-dprintf off
4919 @kindex set disconnected-dprintf
4920 Choose whether @code{dprintf} commands should continue to run if
4921 @value{GDBN} has disconnected from the target. This only applies
4922 if the @code{dprintf-style} is @code{agent}.
4924 @item show disconnected-dprintf off
4925 @kindex show disconnected-dprintf
4926 Show the current choice for disconnected @code{dprintf}.
4930 @value{GDBN} does not check the validity of function and channel,
4931 relying on you to supply values that are meaningful for the contexts
4932 in which they are being used. For instance, the function and channel
4933 may be the values of local variables, but if that is the case, then
4934 all enabled dynamic prints must be at locations within the scope of
4935 those locals. If evaluation fails, @value{GDBN} will report an error.
4937 @node Save Breakpoints
4938 @subsection How to save breakpoints to a file
4940 To save breakpoint definitions to a file use the @w{@code{save
4941 breakpoints}} command.
4944 @kindex save breakpoints
4945 @cindex save breakpoints to a file for future sessions
4946 @item save breakpoints [@var{filename}]
4947 This command saves all current breakpoint definitions together with
4948 their commands and ignore counts, into a file @file{@var{filename}}
4949 suitable for use in a later debugging session. This includes all
4950 types of breakpoints (breakpoints, watchpoints, catchpoints,
4951 tracepoints). To read the saved breakpoint definitions, use the
4952 @code{source} command (@pxref{Command Files}). Note that watchpoints
4953 with expressions involving local variables may fail to be recreated
4954 because it may not be possible to access the context where the
4955 watchpoint is valid anymore. Because the saved breakpoint definitions
4956 are simply a sequence of @value{GDBN} commands that recreate the
4957 breakpoints, you can edit the file in your favorite editing program,
4958 and remove the breakpoint definitions you're not interested in, or
4959 that can no longer be recreated.
4962 @node Static Probe Points
4963 @subsection Static Probe Points
4965 @cindex static probe point, SystemTap
4966 @cindex static probe point, DTrace
4967 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4968 for Statically Defined Tracing, and the probes are designed to have a tiny
4969 runtime code and data footprint, and no dynamic relocations.
4971 Currently, the following types of probes are supported on
4972 ELF-compatible systems:
4976 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4977 @acronym{SDT} probes@footnote{See
4978 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4979 for more information on how to add @code{SystemTap} @acronym{SDT}
4980 probes in your applications.}. @code{SystemTap} probes are usable
4981 from assembly, C and C@t{++} languages@footnote{See
4982 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4983 for a good reference on how the @acronym{SDT} probes are implemented.}.
4985 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
4986 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
4990 @cindex semaphores on static probe points
4991 Some @code{SystemTap} probes have an associated semaphore variable;
4992 for instance, this happens automatically if you defined your probe
4993 using a DTrace-style @file{.d} file. If your probe has a semaphore,
4994 @value{GDBN} will automatically enable it when you specify a
4995 breakpoint using the @samp{-probe-stap} notation. But, if you put a
4996 breakpoint at a probe's location by some other method (e.g.,
4997 @code{break file:line}), then @value{GDBN} will not automatically set
4998 the semaphore. @code{DTrace} probes do not support semaphores.
5000 You can examine the available static static probes using @code{info
5001 probes}, with optional arguments:
5005 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5006 If given, @var{type} is either @code{stap} for listing
5007 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5008 probes. If omitted all probes are listed regardless of their types.
5010 If given, @var{provider} is a regular expression used to match against provider
5011 names when selecting which probes to list. If omitted, probes by all
5012 probes from all providers are listed.
5014 If given, @var{name} is a regular expression to match against probe names
5015 when selecting which probes to list. If omitted, probe names are not
5016 considered when deciding whether to display them.
5018 If given, @var{objfile} is a regular expression used to select which
5019 object files (executable or shared libraries) to examine. If not
5020 given, all object files are considered.
5022 @item info probes all
5023 List the available static probes, from all types.
5026 @cindex enabling and disabling probes
5027 Some probe points can be enabled and/or disabled. The effect of
5028 enabling or disabling a probe depends on the type of probe being
5029 handled. Some @code{DTrace} probes can be enabled or
5030 disabled, but @code{SystemTap} probes cannot be disabled.
5032 You can enable (or disable) one or more probes using the following
5033 commands, with optional arguments:
5036 @kindex enable probes
5037 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5038 If given, @var{provider} is a regular expression used to match against
5039 provider names when selecting which probes to enable. If omitted,
5040 all probes from all providers are enabled.
5042 If given, @var{name} is a regular expression to match against probe
5043 names when selecting which probes to enable. If omitted, probe names
5044 are not considered when deciding whether to enable them.
5046 If given, @var{objfile} is a regular expression used to select which
5047 object files (executable or shared libraries) to examine. If not
5048 given, all object files are considered.
5050 @kindex disable probes
5051 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5052 See the @code{enable probes} command above for a description of the
5053 optional arguments accepted by this command.
5056 @vindex $_probe_arg@r{, convenience variable}
5057 A probe may specify up to twelve arguments. These are available at the
5058 point at which the probe is defined---that is, when the current PC is
5059 at the probe's location. The arguments are available using the
5060 convenience variables (@pxref{Convenience Vars})
5061 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5062 probes each probe argument is an integer of the appropriate size;
5063 types are not preserved. In @code{DTrace} probes types are preserved
5064 provided that they are recognized as such by @value{GDBN}; otherwise
5065 the value of the probe argument will be a long integer. The
5066 convenience variable @code{$_probe_argc} holds the number of arguments
5067 at the current probe point.
5069 These variables are always available, but attempts to access them at
5070 any location other than a probe point will cause @value{GDBN} to give
5074 @c @ifclear BARETARGET
5075 @node Error in Breakpoints
5076 @subsection ``Cannot insert breakpoints''
5078 If you request too many active hardware-assisted breakpoints and
5079 watchpoints, you will see this error message:
5081 @c FIXME: the precise wording of this message may change; the relevant
5082 @c source change is not committed yet (Sep 3, 1999).
5084 Stopped; cannot insert breakpoints.
5085 You may have requested too many hardware breakpoints and watchpoints.
5089 This message is printed when you attempt to resume the program, since
5090 only then @value{GDBN} knows exactly how many hardware breakpoints and
5091 watchpoints it needs to insert.
5093 When this message is printed, you need to disable or remove some of the
5094 hardware-assisted breakpoints and watchpoints, and then continue.
5096 @node Breakpoint-related Warnings
5097 @subsection ``Breakpoint address adjusted...''
5098 @cindex breakpoint address adjusted
5100 Some processor architectures place constraints on the addresses at
5101 which breakpoints may be placed. For architectures thus constrained,
5102 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5103 with the constraints dictated by the architecture.
5105 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5106 a VLIW architecture in which a number of RISC-like instructions may be
5107 bundled together for parallel execution. The FR-V architecture
5108 constrains the location of a breakpoint instruction within such a
5109 bundle to the instruction with the lowest address. @value{GDBN}
5110 honors this constraint by adjusting a breakpoint's address to the
5111 first in the bundle.
5113 It is not uncommon for optimized code to have bundles which contain
5114 instructions from different source statements, thus it may happen that
5115 a breakpoint's address will be adjusted from one source statement to
5116 another. Since this adjustment may significantly alter @value{GDBN}'s
5117 breakpoint related behavior from what the user expects, a warning is
5118 printed when the breakpoint is first set and also when the breakpoint
5121 A warning like the one below is printed when setting a breakpoint
5122 that's been subject to address adjustment:
5125 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5128 Such warnings are printed both for user settable and @value{GDBN}'s
5129 internal breakpoints. If you see one of these warnings, you should
5130 verify that a breakpoint set at the adjusted address will have the
5131 desired affect. If not, the breakpoint in question may be removed and
5132 other breakpoints may be set which will have the desired behavior.
5133 E.g., it may be sufficient to place the breakpoint at a later
5134 instruction. A conditional breakpoint may also be useful in some
5135 cases to prevent the breakpoint from triggering too often.
5137 @value{GDBN} will also issue a warning when stopping at one of these
5138 adjusted breakpoints:
5141 warning: Breakpoint 1 address previously adjusted from 0x00010414
5145 When this warning is encountered, it may be too late to take remedial
5146 action except in cases where the breakpoint is hit earlier or more
5147 frequently than expected.
5149 @node Continuing and Stepping
5150 @section Continuing and Stepping
5154 @cindex resuming execution
5155 @dfn{Continuing} means resuming program execution until your program
5156 completes normally. In contrast, @dfn{stepping} means executing just
5157 one more ``step'' of your program, where ``step'' may mean either one
5158 line of source code, or one machine instruction (depending on what
5159 particular command you use). Either when continuing or when stepping,
5160 your program may stop even sooner, due to a breakpoint or a signal. (If
5161 it stops due to a signal, you may want to use @code{handle}, or use
5162 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5163 or you may step into the signal's handler (@pxref{stepping and signal
5168 @kindex c @r{(@code{continue})}
5169 @kindex fg @r{(resume foreground execution)}
5170 @item continue @r{[}@var{ignore-count}@r{]}
5171 @itemx c @r{[}@var{ignore-count}@r{]}
5172 @itemx fg @r{[}@var{ignore-count}@r{]}
5173 Resume program execution, at the address where your program last stopped;
5174 any breakpoints set at that address are bypassed. The optional argument
5175 @var{ignore-count} allows you to specify a further number of times to
5176 ignore a breakpoint at this location; its effect is like that of
5177 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5179 The argument @var{ignore-count} is meaningful only when your program
5180 stopped due to a breakpoint. At other times, the argument to
5181 @code{continue} is ignored.
5183 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5184 debugged program is deemed to be the foreground program) are provided
5185 purely for convenience, and have exactly the same behavior as
5189 To resume execution at a different place, you can use @code{return}
5190 (@pxref{Returning, ,Returning from a Function}) to go back to the
5191 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5192 Different Address}) to go to an arbitrary location in your program.
5194 A typical technique for using stepping is to set a breakpoint
5195 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5196 beginning of the function or the section of your program where a problem
5197 is believed to lie, run your program until it stops at that breakpoint,
5198 and then step through the suspect area, examining the variables that are
5199 interesting, until you see the problem happen.
5203 @kindex s @r{(@code{step})}
5205 Continue running your program until control reaches a different source
5206 line, then stop it and return control to @value{GDBN}. This command is
5207 abbreviated @code{s}.
5210 @c "without debugging information" is imprecise; actually "without line
5211 @c numbers in the debugging information". (gcc -g1 has debugging info but
5212 @c not line numbers). But it seems complex to try to make that
5213 @c distinction here.
5214 @emph{Warning:} If you use the @code{step} command while control is
5215 within a function that was compiled without debugging information,
5216 execution proceeds until control reaches a function that does have
5217 debugging information. Likewise, it will not step into a function which
5218 is compiled without debugging information. To step through functions
5219 without debugging information, use the @code{stepi} command, described
5223 The @code{step} command only stops at the first instruction of a source
5224 line. This prevents the multiple stops that could otherwise occur in
5225 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5226 to stop if a function that has debugging information is called within
5227 the line. In other words, @code{step} @emph{steps inside} any functions
5228 called within the line.
5230 Also, the @code{step} command only enters a function if there is line
5231 number information for the function. Otherwise it acts like the
5232 @code{next} command. This avoids problems when using @code{cc -gl}
5233 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5234 was any debugging information about the routine.
5236 @item step @var{count}
5237 Continue running as in @code{step}, but do so @var{count} times. If a
5238 breakpoint is reached, or a signal not related to stepping occurs before
5239 @var{count} steps, stepping stops right away.
5242 @kindex n @r{(@code{next})}
5243 @item next @r{[}@var{count}@r{]}
5244 Continue to the next source line in the current (innermost) stack frame.
5245 This is similar to @code{step}, but function calls that appear within
5246 the line of code are executed without stopping. Execution stops when
5247 control reaches a different line of code at the original stack level
5248 that was executing when you gave the @code{next} command. This command
5249 is abbreviated @code{n}.
5251 An argument @var{count} is a repeat count, as for @code{step}.
5254 @c FIX ME!! Do we delete this, or is there a way it fits in with
5255 @c the following paragraph? --- Vctoria
5257 @c @code{next} within a function that lacks debugging information acts like
5258 @c @code{step}, but any function calls appearing within the code of the
5259 @c function are executed without stopping.
5261 The @code{next} command only stops at the first instruction of a
5262 source line. This prevents multiple stops that could otherwise occur in
5263 @code{switch} statements, @code{for} loops, etc.
5265 @kindex set step-mode
5267 @cindex functions without line info, and stepping
5268 @cindex stepping into functions with no line info
5269 @itemx set step-mode on
5270 The @code{set step-mode on} command causes the @code{step} command to
5271 stop at the first instruction of a function which contains no debug line
5272 information rather than stepping over it.
5274 This is useful in cases where you may be interested in inspecting the
5275 machine instructions of a function which has no symbolic info and do not
5276 want @value{GDBN} to automatically skip over this function.
5278 @item set step-mode off
5279 Causes the @code{step} command to step over any functions which contains no
5280 debug information. This is the default.
5282 @item show step-mode
5283 Show whether @value{GDBN} will stop in or step over functions without
5284 source line debug information.
5287 @kindex fin @r{(@code{finish})}
5289 Continue running until just after function in the selected stack frame
5290 returns. Print the returned value (if any). This command can be
5291 abbreviated as @code{fin}.
5293 Contrast this with the @code{return} command (@pxref{Returning,
5294 ,Returning from a Function}).
5297 @kindex u @r{(@code{until})}
5298 @cindex run until specified location
5301 Continue running until a source line past the current line, in the
5302 current stack frame, is reached. This command is used to avoid single
5303 stepping through a loop more than once. It is like the @code{next}
5304 command, except that when @code{until} encounters a jump, it
5305 automatically continues execution until the program counter is greater
5306 than the address of the jump.
5308 This means that when you reach the end of a loop after single stepping
5309 though it, @code{until} makes your program continue execution until it
5310 exits the loop. In contrast, a @code{next} command at the end of a loop
5311 simply steps back to the beginning of the loop, which forces you to step
5312 through the next iteration.
5314 @code{until} always stops your program if it attempts to exit the current
5317 @code{until} may produce somewhat counterintuitive results if the order
5318 of machine code does not match the order of the source lines. For
5319 example, in the following excerpt from a debugging session, the @code{f}
5320 (@code{frame}) command shows that execution is stopped at line
5321 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5325 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5327 (@value{GDBP}) until
5328 195 for ( ; argc > 0; NEXTARG) @{
5331 This happened because, for execution efficiency, the compiler had
5332 generated code for the loop closure test at the end, rather than the
5333 start, of the loop---even though the test in a C @code{for}-loop is
5334 written before the body of the loop. The @code{until} command appeared
5335 to step back to the beginning of the loop when it advanced to this
5336 expression; however, it has not really gone to an earlier
5337 statement---not in terms of the actual machine code.
5339 @code{until} with no argument works by means of single
5340 instruction stepping, and hence is slower than @code{until} with an
5343 @item until @var{location}
5344 @itemx u @var{location}
5345 Continue running your program until either the specified @var{location} is
5346 reached, or the current stack frame returns. The location is any of
5347 the forms described in @ref{Specify Location}.
5348 This form of the command uses temporary breakpoints, and
5349 hence is quicker than @code{until} without an argument. The specified
5350 location is actually reached only if it is in the current frame. This
5351 implies that @code{until} can be used to skip over recursive function
5352 invocations. For instance in the code below, if the current location is
5353 line @code{96}, issuing @code{until 99} will execute the program up to
5354 line @code{99} in the same invocation of factorial, i.e., after the inner
5355 invocations have returned.
5358 94 int factorial (int value)
5360 96 if (value > 1) @{
5361 97 value *= factorial (value - 1);
5368 @kindex advance @var{location}
5369 @item advance @var{location}
5370 Continue running the program up to the given @var{location}. An argument is
5371 required, which should be of one of the forms described in
5372 @ref{Specify Location}.
5373 Execution will also stop upon exit from the current stack
5374 frame. This command is similar to @code{until}, but @code{advance} will
5375 not skip over recursive function calls, and the target location doesn't
5376 have to be in the same frame as the current one.
5380 @kindex si @r{(@code{stepi})}
5382 @itemx stepi @var{arg}
5384 Execute one machine instruction, then stop and return to the debugger.
5386 It is often useful to do @samp{display/i $pc} when stepping by machine
5387 instructions. This makes @value{GDBN} automatically display the next
5388 instruction to be executed, each time your program stops. @xref{Auto
5389 Display,, Automatic Display}.
5391 An argument is a repeat count, as in @code{step}.
5395 @kindex ni @r{(@code{nexti})}
5397 @itemx nexti @var{arg}
5399 Execute one machine instruction, but if it is a function call,
5400 proceed until the function returns.
5402 An argument is a repeat count, as in @code{next}.
5406 @anchor{range stepping}
5407 @cindex range stepping
5408 @cindex target-assisted range stepping
5409 By default, and if available, @value{GDBN} makes use of
5410 target-assisted @dfn{range stepping}. In other words, whenever you
5411 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5412 tells the target to step the corresponding range of instruction
5413 addresses instead of issuing multiple single-steps. This speeds up
5414 line stepping, particularly for remote targets. Ideally, there should
5415 be no reason you would want to turn range stepping off. However, it's
5416 possible that a bug in the debug info, a bug in the remote stub (for
5417 remote targets), or even a bug in @value{GDBN} could make line
5418 stepping behave incorrectly when target-assisted range stepping is
5419 enabled. You can use the following command to turn off range stepping
5423 @kindex set range-stepping
5424 @kindex show range-stepping
5425 @item set range-stepping
5426 @itemx show range-stepping
5427 Control whether range stepping is enabled.
5429 If @code{on}, and the target supports it, @value{GDBN} tells the
5430 target to step a range of addresses itself, instead of issuing
5431 multiple single-steps. If @code{off}, @value{GDBN} always issues
5432 single-steps, even if range stepping is supported by the target. The
5433 default is @code{on}.
5437 @node Skipping Over Functions and Files
5438 @section Skipping Over Functions and Files
5439 @cindex skipping over functions and files
5441 The program you are debugging may contain some functions which are
5442 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5443 skip a function or all functions in a file when stepping.
5445 For example, consider the following C function:
5456 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5457 are not interested in stepping through @code{boring}. If you run @code{step}
5458 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5459 step over both @code{foo} and @code{boring}!
5461 One solution is to @code{step} into @code{boring} and use the @code{finish}
5462 command to immediately exit it. But this can become tedious if @code{boring}
5463 is called from many places.
5465 A more flexible solution is to execute @kbd{skip boring}. This instructs
5466 @value{GDBN} never to step into @code{boring}. Now when you execute
5467 @code{step} at line 103, you'll step over @code{boring} and directly into
5470 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5471 example, @code{skip file boring.c}.
5474 @kindex skip function
5475 @item skip @r{[}@var{linespec}@r{]}
5476 @itemx skip function @r{[}@var{linespec}@r{]}
5477 After running this command, the function named by @var{linespec} or the
5478 function containing the line named by @var{linespec} will be skipped over when
5479 stepping. @xref{Specify Location}.
5481 If you do not specify @var{linespec}, the function you're currently debugging
5484 (If you have a function called @code{file} that you want to skip, use
5485 @kbd{skip function file}.)
5488 @item skip file @r{[}@var{filename}@r{]}
5489 After running this command, any function whose source lives in @var{filename}
5490 will be skipped over when stepping.
5492 If you do not specify @var{filename}, functions whose source lives in the file
5493 you're currently debugging will be skipped.
5496 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5497 These are the commands for managing your list of skips:
5501 @item info skip @r{[}@var{range}@r{]}
5502 Print details about the specified skip(s). If @var{range} is not specified,
5503 print a table with details about all functions and files marked for skipping.
5504 @code{info skip} prints the following information about each skip:
5508 A number identifying this skip.
5510 The type of this skip, either @samp{function} or @samp{file}.
5511 @item Enabled or Disabled
5512 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5514 For function skips, this column indicates the address in memory of the function
5515 being skipped. If you've set a function skip on a function which has not yet
5516 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5517 which has the function is loaded, @code{info skip} will show the function's
5520 For file skips, this field contains the filename being skipped. For functions
5521 skips, this field contains the function name and its line number in the file
5522 where it is defined.
5526 @item skip delete @r{[}@var{range}@r{]}
5527 Delete the specified skip(s). If @var{range} is not specified, delete all
5531 @item skip enable @r{[}@var{range}@r{]}
5532 Enable the specified skip(s). If @var{range} is not specified, enable all
5535 @kindex skip disable
5536 @item skip disable @r{[}@var{range}@r{]}
5537 Disable the specified skip(s). If @var{range} is not specified, disable all
5546 A signal is an asynchronous event that can happen in a program. The
5547 operating system defines the possible kinds of signals, and gives each
5548 kind a name and a number. For example, in Unix @code{SIGINT} is the
5549 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5550 @code{SIGSEGV} is the signal a program gets from referencing a place in
5551 memory far away from all the areas in use; @code{SIGALRM} occurs when
5552 the alarm clock timer goes off (which happens only if your program has
5553 requested an alarm).
5555 @cindex fatal signals
5556 Some signals, including @code{SIGALRM}, are a normal part of the
5557 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5558 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5559 program has not specified in advance some other way to handle the signal.
5560 @code{SIGINT} does not indicate an error in your program, but it is normally
5561 fatal so it can carry out the purpose of the interrupt: to kill the program.
5563 @value{GDBN} has the ability to detect any occurrence of a signal in your
5564 program. You can tell @value{GDBN} in advance what to do for each kind of
5567 @cindex handling signals
5568 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5569 @code{SIGALRM} be silently passed to your program
5570 (so as not to interfere with their role in the program's functioning)
5571 but to stop your program immediately whenever an error signal happens.
5572 You can change these settings with the @code{handle} command.
5575 @kindex info signals
5579 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5580 handle each one. You can use this to see the signal numbers of all
5581 the defined types of signals.
5583 @item info signals @var{sig}
5584 Similar, but print information only about the specified signal number.
5586 @code{info handle} is an alias for @code{info signals}.
5588 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5589 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5590 for details about this command.
5593 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5594 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5595 can be the number of a signal or its name (with or without the
5596 @samp{SIG} at the beginning); a list of signal numbers of the form
5597 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5598 known signals. Optional arguments @var{keywords}, described below,
5599 say what change to make.
5603 The keywords allowed by the @code{handle} command can be abbreviated.
5604 Their full names are:
5608 @value{GDBN} should not stop your program when this signal happens. It may
5609 still print a message telling you that the signal has come in.
5612 @value{GDBN} should stop your program when this signal happens. This implies
5613 the @code{print} keyword as well.
5616 @value{GDBN} should print a message when this signal happens.
5619 @value{GDBN} should not mention the occurrence of the signal at all. This
5620 implies the @code{nostop} keyword as well.
5624 @value{GDBN} should allow your program to see this signal; your program
5625 can handle the signal, or else it may terminate if the signal is fatal
5626 and not handled. @code{pass} and @code{noignore} are synonyms.
5630 @value{GDBN} should not allow your program to see this signal.
5631 @code{nopass} and @code{ignore} are synonyms.
5635 When a signal stops your program, the signal is not visible to the
5637 continue. Your program sees the signal then, if @code{pass} is in
5638 effect for the signal in question @emph{at that time}. In other words,
5639 after @value{GDBN} reports a signal, you can use the @code{handle}
5640 command with @code{pass} or @code{nopass} to control whether your
5641 program sees that signal when you continue.
5643 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5644 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5645 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5648 You can also use the @code{signal} command to prevent your program from
5649 seeing a signal, or cause it to see a signal it normally would not see,
5650 or to give it any signal at any time. For example, if your program stopped
5651 due to some sort of memory reference error, you might store correct
5652 values into the erroneous variables and continue, hoping to see more
5653 execution; but your program would probably terminate immediately as
5654 a result of the fatal signal once it saw the signal. To prevent this,
5655 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5658 @cindex stepping and signal handlers
5659 @anchor{stepping and signal handlers}
5661 @value{GDBN} optimizes for stepping the mainline code. If a signal
5662 that has @code{handle nostop} and @code{handle pass} set arrives while
5663 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5664 in progress, @value{GDBN} lets the signal handler run and then resumes
5665 stepping the mainline code once the signal handler returns. In other
5666 words, @value{GDBN} steps over the signal handler. This prevents
5667 signals that you've specified as not interesting (with @code{handle
5668 nostop}) from changing the focus of debugging unexpectedly. Note that
5669 the signal handler itself may still hit a breakpoint, stop for another
5670 signal that has @code{handle stop} in effect, or for any other event
5671 that normally results in stopping the stepping command sooner. Also
5672 note that @value{GDBN} still informs you that the program received a
5673 signal if @code{handle print} is set.
5675 @anchor{stepping into signal handlers}
5677 If you set @code{handle pass} for a signal, and your program sets up a
5678 handler for it, then issuing a stepping command, such as @code{step}
5679 or @code{stepi}, when your program is stopped due to the signal will
5680 step @emph{into} the signal handler (if the target supports that).
5682 Likewise, if you use the @code{queue-signal} command to queue a signal
5683 to be delivered to the current thread when execution of the thread
5684 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5685 stepping command will step into the signal handler.
5687 Here's an example, using @code{stepi} to step to the first instruction
5688 of @code{SIGUSR1}'s handler:
5691 (@value{GDBP}) handle SIGUSR1
5692 Signal Stop Print Pass to program Description
5693 SIGUSR1 Yes Yes Yes User defined signal 1
5697 Program received signal SIGUSR1, User defined signal 1.
5698 main () sigusr1.c:28
5701 sigusr1_handler () at sigusr1.c:9
5705 The same, but using @code{queue-signal} instead of waiting for the
5706 program to receive the signal first:
5711 (@value{GDBP}) queue-signal SIGUSR1
5713 sigusr1_handler () at sigusr1.c:9
5718 @cindex extra signal information
5719 @anchor{extra signal information}
5721 On some targets, @value{GDBN} can inspect extra signal information
5722 associated with the intercepted signal, before it is actually
5723 delivered to the program being debugged. This information is exported
5724 by the convenience variable @code{$_siginfo}, and consists of data
5725 that is passed by the kernel to the signal handler at the time of the
5726 receipt of a signal. The data type of the information itself is
5727 target dependent. You can see the data type using the @code{ptype
5728 $_siginfo} command. On Unix systems, it typically corresponds to the
5729 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5732 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5733 referenced address that raised a segmentation fault.
5737 (@value{GDBP}) continue
5738 Program received signal SIGSEGV, Segmentation fault.
5739 0x0000000000400766 in main ()
5741 (@value{GDBP}) ptype $_siginfo
5748 struct @{...@} _kill;
5749 struct @{...@} _timer;
5751 struct @{...@} _sigchld;
5752 struct @{...@} _sigfault;
5753 struct @{...@} _sigpoll;
5756 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5760 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5761 $1 = (void *) 0x7ffff7ff7000
5765 Depending on target support, @code{$_siginfo} may also be writable.
5768 @section Stopping and Starting Multi-thread Programs
5770 @cindex stopped threads
5771 @cindex threads, stopped
5773 @cindex continuing threads
5774 @cindex threads, continuing
5776 @value{GDBN} supports debugging programs with multiple threads
5777 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5778 are two modes of controlling execution of your program within the
5779 debugger. In the default mode, referred to as @dfn{all-stop mode},
5780 when any thread in your program stops (for example, at a breakpoint
5781 or while being stepped), all other threads in the program are also stopped by
5782 @value{GDBN}. On some targets, @value{GDBN} also supports
5783 @dfn{non-stop mode}, in which other threads can continue to run freely while
5784 you examine the stopped thread in the debugger.
5787 * All-Stop Mode:: All threads stop when GDB takes control
5788 * Non-Stop Mode:: Other threads continue to execute
5789 * Background Execution:: Running your program asynchronously
5790 * Thread-Specific Breakpoints:: Controlling breakpoints
5791 * Interrupted System Calls:: GDB may interfere with system calls
5792 * Observer Mode:: GDB does not alter program behavior
5796 @subsection All-Stop Mode
5798 @cindex all-stop mode
5800 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5801 @emph{all} threads of execution stop, not just the current thread. This
5802 allows you to examine the overall state of the program, including
5803 switching between threads, without worrying that things may change
5806 Conversely, whenever you restart the program, @emph{all} threads start
5807 executing. @emph{This is true even when single-stepping} with commands
5808 like @code{step} or @code{next}.
5810 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5811 Since thread scheduling is up to your debugging target's operating
5812 system (not controlled by @value{GDBN}), other threads may
5813 execute more than one statement while the current thread completes a
5814 single step. Moreover, in general other threads stop in the middle of a
5815 statement, rather than at a clean statement boundary, when the program
5818 You might even find your program stopped in another thread after
5819 continuing or even single-stepping. This happens whenever some other
5820 thread runs into a breakpoint, a signal, or an exception before the
5821 first thread completes whatever you requested.
5823 @cindex automatic thread selection
5824 @cindex switching threads automatically
5825 @cindex threads, automatic switching
5826 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5827 signal, it automatically selects the thread where that breakpoint or
5828 signal happened. @value{GDBN} alerts you to the context switch with a
5829 message such as @samp{[Switching to Thread @var{n}]} to identify the
5832 On some OSes, you can modify @value{GDBN}'s default behavior by
5833 locking the OS scheduler to allow only a single thread to run.
5836 @item set scheduler-locking @var{mode}
5837 @cindex scheduler locking mode
5838 @cindex lock scheduler
5839 Set the scheduler locking mode. If it is @code{off}, then there is no
5840 locking and any thread may run at any time. If @code{on}, then only the
5841 current thread may run when the inferior is resumed. The @code{step}
5842 mode optimizes for single-stepping; it prevents other threads
5843 from preempting the current thread while you are stepping, so that
5844 the focus of debugging does not change unexpectedly.
5845 Other threads never get a chance to run when you step, and they are
5846 completely free to run when you use commands
5847 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5848 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5849 the current thread away from the thread that you are debugging.
5851 @item show scheduler-locking
5852 Display the current scheduler locking mode.
5855 @cindex resume threads of multiple processes simultaneously
5856 By default, when you issue one of the execution commands such as
5857 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5858 threads of the current inferior to run. For example, if @value{GDBN}
5859 is attached to two inferiors, each with two threads, the
5860 @code{continue} command resumes only the two threads of the current
5861 inferior. This is useful, for example, when you debug a program that
5862 forks and you want to hold the parent stopped (so that, for instance,
5863 it doesn't run to exit), while you debug the child. In other
5864 situations, you may not be interested in inspecting the current state
5865 of any of the processes @value{GDBN} is attached to, and you may want
5866 to resume them all until some breakpoint is hit. In the latter case,
5867 you can instruct @value{GDBN} to allow all threads of all the
5868 inferiors to run with the @w{@code{set schedule-multiple}} command.
5871 @kindex set schedule-multiple
5872 @item set schedule-multiple
5873 Set the mode for allowing threads of multiple processes to be resumed
5874 when an execution command is issued. When @code{on}, all threads of
5875 all processes are allowed to run. When @code{off}, only the threads
5876 of the current process are resumed. The default is @code{off}. The
5877 @code{scheduler-locking} mode takes precedence when set to @code{on},
5878 or while you are stepping and set to @code{step}.
5880 @item show schedule-multiple
5881 Display the current mode for resuming the execution of threads of
5886 @subsection Non-Stop Mode
5888 @cindex non-stop mode
5890 @c This section is really only a place-holder, and needs to be expanded
5891 @c with more details.
5893 For some multi-threaded targets, @value{GDBN} supports an optional
5894 mode of operation in which you can examine stopped program threads in
5895 the debugger while other threads continue to execute freely. This
5896 minimizes intrusion when debugging live systems, such as programs
5897 where some threads have real-time constraints or must continue to
5898 respond to external events. This is referred to as @dfn{non-stop} mode.
5900 In non-stop mode, when a thread stops to report a debugging event,
5901 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5902 threads as well, in contrast to the all-stop mode behavior. Additionally,
5903 execution commands such as @code{continue} and @code{step} apply by default
5904 only to the current thread in non-stop mode, rather than all threads as
5905 in all-stop mode. This allows you to control threads explicitly in
5906 ways that are not possible in all-stop mode --- for example, stepping
5907 one thread while allowing others to run freely, stepping
5908 one thread while holding all others stopped, or stepping several threads
5909 independently and simultaneously.
5911 To enter non-stop mode, use this sequence of commands before you run
5912 or attach to your program:
5915 # If using the CLI, pagination breaks non-stop.
5918 # Finally, turn it on!
5922 You can use these commands to manipulate the non-stop mode setting:
5925 @kindex set non-stop
5926 @item set non-stop on
5927 Enable selection of non-stop mode.
5928 @item set non-stop off
5929 Disable selection of non-stop mode.
5930 @kindex show non-stop
5932 Show the current non-stop enablement setting.
5935 Note these commands only reflect whether non-stop mode is enabled,
5936 not whether the currently-executing program is being run in non-stop mode.
5937 In particular, the @code{set non-stop} preference is only consulted when
5938 @value{GDBN} starts or connects to the target program, and it is generally
5939 not possible to switch modes once debugging has started. Furthermore,
5940 since not all targets support non-stop mode, even when you have enabled
5941 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5944 In non-stop mode, all execution commands apply only to the current thread
5945 by default. That is, @code{continue} only continues one thread.
5946 To continue all threads, issue @code{continue -a} or @code{c -a}.
5948 You can use @value{GDBN}'s background execution commands
5949 (@pxref{Background Execution}) to run some threads in the background
5950 while you continue to examine or step others from @value{GDBN}.
5951 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5952 always executed asynchronously in non-stop mode.
5954 Suspending execution is done with the @code{interrupt} command when
5955 running in the background, or @kbd{Ctrl-c} during foreground execution.
5956 In all-stop mode, this stops the whole process;
5957 but in non-stop mode the interrupt applies only to the current thread.
5958 To stop the whole program, use @code{interrupt -a}.
5960 Other execution commands do not currently support the @code{-a} option.
5962 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5963 that thread current, as it does in all-stop mode. This is because the
5964 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5965 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5966 changed to a different thread just as you entered a command to operate on the
5967 previously current thread.
5969 @node Background Execution
5970 @subsection Background Execution
5972 @cindex foreground execution
5973 @cindex background execution
5974 @cindex asynchronous execution
5975 @cindex execution, foreground, background and asynchronous
5977 @value{GDBN}'s execution commands have two variants: the normal
5978 foreground (synchronous) behavior, and a background
5979 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5980 the program to report that some thread has stopped before prompting for
5981 another command. In background execution, @value{GDBN} immediately gives
5982 a command prompt so that you can issue other commands while your program runs.
5984 If the target doesn't support async mode, @value{GDBN} issues an error
5985 message if you attempt to use the background execution commands.
5987 To specify background execution, add a @code{&} to the command. For example,
5988 the background form of the @code{continue} command is @code{continue&}, or
5989 just @code{c&}. The execution commands that accept background execution
5995 @xref{Starting, , Starting your Program}.
5999 @xref{Attach, , Debugging an Already-running Process}.
6003 @xref{Continuing and Stepping, step}.
6007 @xref{Continuing and Stepping, stepi}.
6011 @xref{Continuing and Stepping, next}.
6015 @xref{Continuing and Stepping, nexti}.
6019 @xref{Continuing and Stepping, continue}.
6023 @xref{Continuing and Stepping, finish}.
6027 @xref{Continuing and Stepping, until}.
6031 Background execution is especially useful in conjunction with non-stop
6032 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6033 However, you can also use these commands in the normal all-stop mode with
6034 the restriction that you cannot issue another execution command until the
6035 previous one finishes. Examples of commands that are valid in all-stop
6036 mode while the program is running include @code{help} and @code{info break}.
6038 You can interrupt your program while it is running in the background by
6039 using the @code{interrupt} command.
6046 Suspend execution of the running program. In all-stop mode,
6047 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6048 only the current thread. To stop the whole program in non-stop mode,
6049 use @code{interrupt -a}.
6052 @node Thread-Specific Breakpoints
6053 @subsection Thread-Specific Breakpoints
6055 When your program has multiple threads (@pxref{Threads,, Debugging
6056 Programs with Multiple Threads}), you can choose whether to set
6057 breakpoints on all threads, or on a particular thread.
6060 @cindex breakpoints and threads
6061 @cindex thread breakpoints
6062 @kindex break @dots{} thread @var{threadno}
6063 @item break @var{location} thread @var{threadno}
6064 @itemx break @var{location} thread @var{threadno} if @dots{}
6065 @var{location} specifies source lines; there are several ways of
6066 writing them (@pxref{Specify Location}), but the effect is always to
6067 specify some source line.
6069 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
6070 to specify that you only want @value{GDBN} to stop the program when a
6071 particular thread reaches this breakpoint. The @var{threadno} specifier
6072 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
6073 in the first column of the @samp{info threads} display.
6075 If you do not specify @samp{thread @var{threadno}} when you set a
6076 breakpoint, the breakpoint applies to @emph{all} threads of your
6079 You can use the @code{thread} qualifier on conditional breakpoints as
6080 well; in this case, place @samp{thread @var{threadno}} before or
6081 after the breakpoint condition, like this:
6084 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6089 Thread-specific breakpoints are automatically deleted when
6090 @value{GDBN} detects the corresponding thread is no longer in the
6091 thread list. For example:
6095 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6098 There are several ways for a thread to disappear, such as a regular
6099 thread exit, but also when you detach from the process with the
6100 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6101 Process}), or if @value{GDBN} loses the remote connection
6102 (@pxref{Remote Debugging}), etc. Note that with some targets,
6103 @value{GDBN} is only able to detect a thread has exited when the user
6104 explictly asks for the thread list with the @code{info threads}
6107 @node Interrupted System Calls
6108 @subsection Interrupted System Calls
6110 @cindex thread breakpoints and system calls
6111 @cindex system calls and thread breakpoints
6112 @cindex premature return from system calls
6113 There is an unfortunate side effect when using @value{GDBN} to debug
6114 multi-threaded programs. If one thread stops for a
6115 breakpoint, or for some other reason, and another thread is blocked in a
6116 system call, then the system call may return prematurely. This is a
6117 consequence of the interaction between multiple threads and the signals
6118 that @value{GDBN} uses to implement breakpoints and other events that
6121 To handle this problem, your program should check the return value of
6122 each system call and react appropriately. This is good programming
6125 For example, do not write code like this:
6131 The call to @code{sleep} will return early if a different thread stops
6132 at a breakpoint or for some other reason.
6134 Instead, write this:
6139 unslept = sleep (unslept);
6142 A system call is allowed to return early, so the system is still
6143 conforming to its specification. But @value{GDBN} does cause your
6144 multi-threaded program to behave differently than it would without
6147 Also, @value{GDBN} uses internal breakpoints in the thread library to
6148 monitor certain events such as thread creation and thread destruction.
6149 When such an event happens, a system call in another thread may return
6150 prematurely, even though your program does not appear to stop.
6153 @subsection Observer Mode
6155 If you want to build on non-stop mode and observe program behavior
6156 without any chance of disruption by @value{GDBN}, you can set
6157 variables to disable all of the debugger's attempts to modify state,
6158 whether by writing memory, inserting breakpoints, etc. These operate
6159 at a low level, intercepting operations from all commands.
6161 When all of these are set to @code{off}, then @value{GDBN} is said to
6162 be @dfn{observer mode}. As a convenience, the variable
6163 @code{observer} can be set to disable these, plus enable non-stop
6166 Note that @value{GDBN} will not prevent you from making nonsensical
6167 combinations of these settings. For instance, if you have enabled
6168 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6169 then breakpoints that work by writing trap instructions into the code
6170 stream will still not be able to be placed.
6175 @item set observer on
6176 @itemx set observer off
6177 When set to @code{on}, this disables all the permission variables
6178 below (except for @code{insert-fast-tracepoints}), plus enables
6179 non-stop debugging. Setting this to @code{off} switches back to
6180 normal debugging, though remaining in non-stop mode.
6183 Show whether observer mode is on or off.
6185 @kindex may-write-registers
6186 @item set may-write-registers on
6187 @itemx set may-write-registers off
6188 This controls whether @value{GDBN} will attempt to alter the values of
6189 registers, such as with assignment expressions in @code{print}, or the
6190 @code{jump} command. It defaults to @code{on}.
6192 @item show may-write-registers
6193 Show the current permission to write registers.
6195 @kindex may-write-memory
6196 @item set may-write-memory on
6197 @itemx set may-write-memory off
6198 This controls whether @value{GDBN} will attempt to alter the contents
6199 of memory, such as with assignment expressions in @code{print}. It
6200 defaults to @code{on}.
6202 @item show may-write-memory
6203 Show the current permission to write memory.
6205 @kindex may-insert-breakpoints
6206 @item set may-insert-breakpoints on
6207 @itemx set may-insert-breakpoints off
6208 This controls whether @value{GDBN} will attempt to insert breakpoints.
6209 This affects all breakpoints, including internal breakpoints defined
6210 by @value{GDBN}. It defaults to @code{on}.
6212 @item show may-insert-breakpoints
6213 Show the current permission to insert breakpoints.
6215 @kindex may-insert-tracepoints
6216 @item set may-insert-tracepoints on
6217 @itemx set may-insert-tracepoints off
6218 This controls whether @value{GDBN} will attempt to insert (regular)
6219 tracepoints at the beginning of a tracing experiment. It affects only
6220 non-fast tracepoints, fast tracepoints being under the control of
6221 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6223 @item show may-insert-tracepoints
6224 Show the current permission to insert tracepoints.
6226 @kindex may-insert-fast-tracepoints
6227 @item set may-insert-fast-tracepoints on
6228 @itemx set may-insert-fast-tracepoints off
6229 This controls whether @value{GDBN} will attempt to insert fast
6230 tracepoints at the beginning of a tracing experiment. It affects only
6231 fast tracepoints, regular (non-fast) tracepoints being under the
6232 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6234 @item show may-insert-fast-tracepoints
6235 Show the current permission to insert fast tracepoints.
6237 @kindex may-interrupt
6238 @item set may-interrupt on
6239 @itemx set may-interrupt off
6240 This controls whether @value{GDBN} will attempt to interrupt or stop
6241 program execution. When this variable is @code{off}, the
6242 @code{interrupt} command will have no effect, nor will
6243 @kbd{Ctrl-c}. It defaults to @code{on}.
6245 @item show may-interrupt
6246 Show the current permission to interrupt or stop the program.
6250 @node Reverse Execution
6251 @chapter Running programs backward
6252 @cindex reverse execution
6253 @cindex running programs backward
6255 When you are debugging a program, it is not unusual to realize that
6256 you have gone too far, and some event of interest has already happened.
6257 If the target environment supports it, @value{GDBN} can allow you to
6258 ``rewind'' the program by running it backward.
6260 A target environment that supports reverse execution should be able
6261 to ``undo'' the changes in machine state that have taken place as the
6262 program was executing normally. Variables, registers etc.@: should
6263 revert to their previous values. Obviously this requires a great
6264 deal of sophistication on the part of the target environment; not
6265 all target environments can support reverse execution.
6267 When a program is executed in reverse, the instructions that
6268 have most recently been executed are ``un-executed'', in reverse
6269 order. The program counter runs backward, following the previous
6270 thread of execution in reverse. As each instruction is ``un-executed'',
6271 the values of memory and/or registers that were changed by that
6272 instruction are reverted to their previous states. After executing
6273 a piece of source code in reverse, all side effects of that code
6274 should be ``undone'', and all variables should be returned to their
6275 prior values@footnote{
6276 Note that some side effects are easier to undo than others. For instance,
6277 memory and registers are relatively easy, but device I/O is hard. Some
6278 targets may be able undo things like device I/O, and some may not.
6280 The contract between @value{GDBN} and the reverse executing target
6281 requires only that the target do something reasonable when
6282 @value{GDBN} tells it to execute backwards, and then report the
6283 results back to @value{GDBN}. Whatever the target reports back to
6284 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6285 assumes that the memory and registers that the target reports are in a
6286 consistant state, but @value{GDBN} accepts whatever it is given.
6289 If you are debugging in a target environment that supports
6290 reverse execution, @value{GDBN} provides the following commands.
6293 @kindex reverse-continue
6294 @kindex rc @r{(@code{reverse-continue})}
6295 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6296 @itemx rc @r{[}@var{ignore-count}@r{]}
6297 Beginning at the point where your program last stopped, start executing
6298 in reverse. Reverse execution will stop for breakpoints and synchronous
6299 exceptions (signals), just like normal execution. Behavior of
6300 asynchronous signals depends on the target environment.
6302 @kindex reverse-step
6303 @kindex rs @r{(@code{step})}
6304 @item reverse-step @r{[}@var{count}@r{]}
6305 Run the program backward until control reaches the start of a
6306 different source line; then stop it, and return control to @value{GDBN}.
6308 Like the @code{step} command, @code{reverse-step} will only stop
6309 at the beginning of a source line. It ``un-executes'' the previously
6310 executed source line. If the previous source line included calls to
6311 debuggable functions, @code{reverse-step} will step (backward) into
6312 the called function, stopping at the beginning of the @emph{last}
6313 statement in the called function (typically a return statement).
6315 Also, as with the @code{step} command, if non-debuggable functions are
6316 called, @code{reverse-step} will run thru them backward without stopping.
6318 @kindex reverse-stepi
6319 @kindex rsi @r{(@code{reverse-stepi})}
6320 @item reverse-stepi @r{[}@var{count}@r{]}
6321 Reverse-execute one machine instruction. Note that the instruction
6322 to be reverse-executed is @emph{not} the one pointed to by the program
6323 counter, but the instruction executed prior to that one. For instance,
6324 if the last instruction was a jump, @code{reverse-stepi} will take you
6325 back from the destination of the jump to the jump instruction itself.
6327 @kindex reverse-next
6328 @kindex rn @r{(@code{reverse-next})}
6329 @item reverse-next @r{[}@var{count}@r{]}
6330 Run backward to the beginning of the previous line executed in
6331 the current (innermost) stack frame. If the line contains function
6332 calls, they will be ``un-executed'' without stopping. Starting from
6333 the first line of a function, @code{reverse-next} will take you back
6334 to the caller of that function, @emph{before} the function was called,
6335 just as the normal @code{next} command would take you from the last
6336 line of a function back to its return to its caller
6337 @footnote{Unless the code is too heavily optimized.}.
6339 @kindex reverse-nexti
6340 @kindex rni @r{(@code{reverse-nexti})}
6341 @item reverse-nexti @r{[}@var{count}@r{]}
6342 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6343 in reverse, except that called functions are ``un-executed'' atomically.
6344 That is, if the previously executed instruction was a return from
6345 another function, @code{reverse-nexti} will continue to execute
6346 in reverse until the call to that function (from the current stack
6349 @kindex reverse-finish
6350 @item reverse-finish
6351 Just as the @code{finish} command takes you to the point where the
6352 current function returns, @code{reverse-finish} takes you to the point
6353 where it was called. Instead of ending up at the end of the current
6354 function invocation, you end up at the beginning.
6356 @kindex set exec-direction
6357 @item set exec-direction
6358 Set the direction of target execution.
6359 @item set exec-direction reverse
6360 @cindex execute forward or backward in time
6361 @value{GDBN} will perform all execution commands in reverse, until the
6362 exec-direction mode is changed to ``forward''. Affected commands include
6363 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6364 command cannot be used in reverse mode.
6365 @item set exec-direction forward
6366 @value{GDBN} will perform all execution commands in the normal fashion.
6367 This is the default.
6371 @node Process Record and Replay
6372 @chapter Recording Inferior's Execution and Replaying It
6373 @cindex process record and replay
6374 @cindex recording inferior's execution and replaying it
6376 On some platforms, @value{GDBN} provides a special @dfn{process record
6377 and replay} target that can record a log of the process execution, and
6378 replay it later with both forward and reverse execution commands.
6381 When this target is in use, if the execution log includes the record
6382 for the next instruction, @value{GDBN} will debug in @dfn{replay
6383 mode}. In the replay mode, the inferior does not really execute code
6384 instructions. Instead, all the events that normally happen during
6385 code execution are taken from the execution log. While code is not
6386 really executed in replay mode, the values of registers (including the
6387 program counter register) and the memory of the inferior are still
6388 changed as they normally would. Their contents are taken from the
6392 If the record for the next instruction is not in the execution log,
6393 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6394 inferior executes normally, and @value{GDBN} records the execution log
6397 The process record and replay target supports reverse execution
6398 (@pxref{Reverse Execution}), even if the platform on which the
6399 inferior runs does not. However, the reverse execution is limited in
6400 this case by the range of the instructions recorded in the execution
6401 log. In other words, reverse execution on platforms that don't
6402 support it directly can only be done in the replay mode.
6404 When debugging in the reverse direction, @value{GDBN} will work in
6405 replay mode as long as the execution log includes the record for the
6406 previous instruction; otherwise, it will work in record mode, if the
6407 platform supports reverse execution, or stop if not.
6409 For architecture environments that support process record and replay,
6410 @value{GDBN} provides the following commands:
6413 @kindex target record
6414 @kindex target record-full
6415 @kindex target record-btrace
6418 @kindex record btrace
6419 @kindex record btrace bts
6420 @kindex record btrace pt
6426 @kindex rec btrace bts
6427 @kindex rec btrace pt
6430 @item record @var{method}
6431 This command starts the process record and replay target. The
6432 recording method can be specified as parameter. Without a parameter
6433 the command uses the @code{full} recording method. The following
6434 recording methods are available:
6438 Full record/replay recording using @value{GDBN}'s software record and
6439 replay implementation. This method allows replaying and reverse
6442 @item btrace @var{format}
6443 Hardware-supported instruction recording. This method does not record
6444 data. Further, the data is collected in a ring buffer so old data will
6445 be overwritten when the buffer is full. It allows limited reverse
6446 execution. Variables and registers are not available during reverse
6449 The recording format can be specified as parameter. Without a parameter
6450 the command chooses the recording format. The following recording
6451 formats are available:
6455 @cindex branch trace store
6456 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6457 this format, the processor stores a from/to record for each executed
6458 branch in the btrace ring buffer.
6461 @cindex Intel(R) Processor Trace
6462 Use the @dfn{Intel(R) Processor Trace} recording format. In this
6463 format, the processor stores the execution trace in a compressed form
6464 that is afterwards decoded by @value{GDBN}.
6466 The trace can be recorded with very low overhead. The compressed
6467 trace format also allows small trace buffers to already contain a big
6468 number of instructions compared to @acronym{BTS}.
6470 Decoding the recorded execution trace, on the other hand, is more
6471 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6472 increased number of instructions to process. You should increase the
6473 buffer-size with care.
6476 Not all recording formats may be available on all processors.
6479 The process record and replay target can only debug a process that is
6480 already running. Therefore, you need first to start the process with
6481 the @kbd{run} or @kbd{start} commands, and then start the recording
6482 with the @kbd{record @var{method}} command.
6484 @cindex displaced stepping, and process record and replay
6485 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6486 will be automatically disabled when process record and replay target
6487 is started. That's because the process record and replay target
6488 doesn't support displaced stepping.
6490 @cindex non-stop mode, and process record and replay
6491 @cindex asynchronous execution, and process record and replay
6492 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6493 the asynchronous execution mode (@pxref{Background Execution}), not
6494 all recording methods are available. The @code{full} recording method
6495 does not support these two modes.
6500 Stop the process record and replay target. When process record and
6501 replay target stops, the entire execution log will be deleted and the
6502 inferior will either be terminated, or will remain in its final state.
6504 When you stop the process record and replay target in record mode (at
6505 the end of the execution log), the inferior will be stopped at the
6506 next instruction that would have been recorded. In other words, if
6507 you record for a while and then stop recording, the inferior process
6508 will be left in the same state as if the recording never happened.
6510 On the other hand, if the process record and replay target is stopped
6511 while in replay mode (that is, not at the end of the execution log,
6512 but at some earlier point), the inferior process will become ``live''
6513 at that earlier state, and it will then be possible to continue the
6514 usual ``live'' debugging of the process from that state.
6516 When the inferior process exits, or @value{GDBN} detaches from it,
6517 process record and replay target will automatically stop itself.
6521 Go to a specific location in the execution log. There are several
6522 ways to specify the location to go to:
6525 @item record goto begin
6526 @itemx record goto start
6527 Go to the beginning of the execution log.
6529 @item record goto end
6530 Go to the end of the execution log.
6532 @item record goto @var{n}
6533 Go to instruction number @var{n} in the execution log.
6537 @item record save @var{filename}
6538 Save the execution log to a file @file{@var{filename}}.
6539 Default filename is @file{gdb_record.@var{process_id}}, where
6540 @var{process_id} is the process ID of the inferior.
6542 This command may not be available for all recording methods.
6544 @kindex record restore
6545 @item record restore @var{filename}
6546 Restore the execution log from a file @file{@var{filename}}.
6547 File must have been created with @code{record save}.
6549 @kindex set record full
6550 @item set record full insn-number-max @var{limit}
6551 @itemx set record full insn-number-max unlimited
6552 Set the limit of instructions to be recorded for the @code{full}
6553 recording method. Default value is 200000.
6555 If @var{limit} is a positive number, then @value{GDBN} will start
6556 deleting instructions from the log once the number of the record
6557 instructions becomes greater than @var{limit}. For every new recorded
6558 instruction, @value{GDBN} will delete the earliest recorded
6559 instruction to keep the number of recorded instructions at the limit.
6560 (Since deleting recorded instructions loses information, @value{GDBN}
6561 lets you control what happens when the limit is reached, by means of
6562 the @code{stop-at-limit} option, described below.)
6564 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6565 delete recorded instructions from the execution log. The number of
6566 recorded instructions is limited only by the available memory.
6568 @kindex show record full
6569 @item show record full insn-number-max
6570 Show the limit of instructions to be recorded with the @code{full}
6573 @item set record full stop-at-limit
6574 Control the behavior of the @code{full} recording method when the
6575 number of recorded instructions reaches the limit. If ON (the
6576 default), @value{GDBN} will stop when the limit is reached for the
6577 first time and ask you whether you want to stop the inferior or
6578 continue running it and recording the execution log. If you decide
6579 to continue recording, each new recorded instruction will cause the
6580 oldest one to be deleted.
6582 If this option is OFF, @value{GDBN} will automatically delete the
6583 oldest record to make room for each new one, without asking.
6585 @item show record full stop-at-limit
6586 Show the current setting of @code{stop-at-limit}.
6588 @item set record full memory-query
6589 Control the behavior when @value{GDBN} is unable to record memory
6590 changes caused by an instruction for the @code{full} recording method.
6591 If ON, @value{GDBN} will query whether to stop the inferior in that
6594 If this option is OFF (the default), @value{GDBN} will automatically
6595 ignore the effect of such instructions on memory. Later, when
6596 @value{GDBN} replays this execution log, it will mark the log of this
6597 instruction as not accessible, and it will not affect the replay
6600 @item show record full memory-query
6601 Show the current setting of @code{memory-query}.
6603 @kindex set record btrace
6604 The @code{btrace} record target does not trace data. As a
6605 convenience, when replaying, @value{GDBN} reads read-only memory off
6606 the live program directly, assuming that the addresses of the
6607 read-only areas don't change. This for example makes it possible to
6608 disassemble code while replaying, but not to print variables.
6609 In some cases, being able to inspect variables might be useful.
6610 You can use the following command for that:
6612 @item set record btrace replay-memory-access
6613 Control the behavior of the @code{btrace} recording method when
6614 accessing memory during replay. If @code{read-only} (the default),
6615 @value{GDBN} will only allow accesses to read-only memory.
6616 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6617 and to read-write memory. Beware that the accessed memory corresponds
6618 to the live target and not necessarily to the current replay
6621 @kindex show record btrace
6622 @item show record btrace replay-memory-access
6623 Show the current setting of @code{replay-memory-access}.
6625 @kindex set record btrace bts
6626 @item set record btrace bts buffer-size @var{size}
6627 @itemx set record btrace bts buffer-size unlimited
6628 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6629 format. Default is 64KB.
6631 If @var{size} is a positive number, then @value{GDBN} will try to
6632 allocate a buffer of at least @var{size} bytes for each new thread
6633 that uses the btrace recording method and the @acronym{BTS} format.
6634 The actually obtained buffer size may differ from the requested
6635 @var{size}. Use the @code{info record} command to see the actual
6636 buffer size for each thread that uses the btrace recording method and
6637 the @acronym{BTS} format.
6639 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6640 allocate a buffer of 4MB.
6642 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6643 also need longer to process the branch trace data before it can be used.
6645 @item show record btrace bts buffer-size @var{size}
6646 Show the current setting of the requested ring buffer size for branch
6647 tracing in @acronym{BTS} format.
6649 @kindex set record btrace pt
6650 @item set record btrace pt buffer-size @var{size}
6651 @itemx set record btrace pt buffer-size unlimited
6652 Set the requested ring buffer size for branch tracing in Intel(R)
6653 Processor Trace format. Default is 16KB.
6655 If @var{size} is a positive number, then @value{GDBN} will try to
6656 allocate a buffer of at least @var{size} bytes for each new thread
6657 that uses the btrace recording method and the Intel(R) Processor Trace
6658 format. The actually obtained buffer size may differ from the
6659 requested @var{size}. Use the @code{info record} command to see the
6660 actual buffer size for each thread.
6662 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6663 allocate a buffer of 4MB.
6665 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6666 also need longer to process the branch trace data before it can be used.
6668 @item show record btrace pt buffer-size @var{size}
6669 Show the current setting of the requested ring buffer size for branch
6670 tracing in Intel(R) Processor Trace format.
6674 Show various statistics about the recording depending on the recording
6679 For the @code{full} recording method, it shows the state of process
6680 record and its in-memory execution log buffer, including:
6684 Whether in record mode or replay mode.
6686 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6688 Highest recorded instruction number.
6690 Current instruction about to be replayed (if in replay mode).
6692 Number of instructions contained in the execution log.
6694 Maximum number of instructions that may be contained in the execution log.
6698 For the @code{btrace} recording method, it shows:
6704 Number of instructions that have been recorded.
6706 Number of blocks of sequential control-flow formed by the recorded
6709 Whether in record mode or replay mode.
6712 For the @code{bts} recording format, it also shows:
6715 Size of the perf ring buffer.
6718 For the @code{pt} recording format, it also shows:
6721 Size of the perf ring buffer.
6725 @kindex record delete
6728 When record target runs in replay mode (``in the past''), delete the
6729 subsequent execution log and begin to record a new execution log starting
6730 from the current address. This means you will abandon the previously
6731 recorded ``future'' and begin recording a new ``future''.
6733 @kindex record instruction-history
6734 @kindex rec instruction-history
6735 @item record instruction-history
6736 Disassembles instructions from the recorded execution log. By
6737 default, ten instructions are disassembled. This can be changed using
6738 the @code{set record instruction-history-size} command. Instructions
6739 are printed in execution order.
6741 Speculatively executed instructions are prefixed with @samp{?}. This
6742 feature is not available for all recording formats.
6744 There are several ways to specify what part of the execution log to
6748 @item record instruction-history @var{insn}
6749 Disassembles ten instructions starting from instruction number
6752 @item record instruction-history @var{insn}, +/-@var{n}
6753 Disassembles @var{n} instructions around instruction number
6754 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6755 @var{n} instructions after instruction number @var{insn}. If
6756 @var{n} is preceded with @code{-}, disassembles @var{n}
6757 instructions before instruction number @var{insn}.
6759 @item record instruction-history
6760 Disassembles ten more instructions after the last disassembly.
6762 @item record instruction-history -
6763 Disassembles ten more instructions before the last disassembly.
6765 @item record instruction-history @var{begin} @var{end}
6766 Disassembles instructions beginning with instruction number
6767 @var{begin} until instruction number @var{end}. The instruction
6768 number @var{end} is included.
6771 This command may not be available for all recording methods.
6774 @item set record instruction-history-size @var{size}
6775 @itemx set record instruction-history-size unlimited
6776 Define how many instructions to disassemble in the @code{record
6777 instruction-history} command. The default value is 10.
6778 A @var{size} of @code{unlimited} means unlimited instructions.
6781 @item show record instruction-history-size
6782 Show how many instructions to disassemble in the @code{record
6783 instruction-history} command.
6785 @kindex record function-call-history
6786 @kindex rec function-call-history
6787 @item record function-call-history
6788 Prints the execution history at function granularity. It prints one
6789 line for each sequence of instructions that belong to the same
6790 function giving the name of that function, the source lines
6791 for this instruction sequence (if the @code{/l} modifier is
6792 specified), and the instructions numbers that form the sequence (if
6793 the @code{/i} modifier is specified). The function names are indented
6794 to reflect the call stack depth if the @code{/c} modifier is
6795 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6799 (@value{GDBP}) @b{list 1, 10}
6810 (@value{GDBP}) @b{record function-call-history /ilc}
6811 1 bar inst 1,4 at foo.c:6,8
6812 2 foo inst 5,10 at foo.c:2,3
6813 3 bar inst 11,13 at foo.c:9,10
6816 By default, ten lines are printed. This can be changed using the
6817 @code{set record function-call-history-size} command. Functions are
6818 printed in execution order. There are several ways to specify what
6822 @item record function-call-history @var{func}
6823 Prints ten functions starting from function number @var{func}.
6825 @item record function-call-history @var{func}, +/-@var{n}
6826 Prints @var{n} functions around function number @var{func}. If
6827 @var{n} is preceded with @code{+}, prints @var{n} functions after
6828 function number @var{func}. If @var{n} is preceded with @code{-},
6829 prints @var{n} functions before function number @var{func}.
6831 @item record function-call-history
6832 Prints ten more functions after the last ten-line print.
6834 @item record function-call-history -
6835 Prints ten more functions before the last ten-line print.
6837 @item record function-call-history @var{begin} @var{end}
6838 Prints functions beginning with function number @var{begin} until
6839 function number @var{end}. The function number @var{end} is included.
6842 This command may not be available for all recording methods.
6844 @item set record function-call-history-size @var{size}
6845 @itemx set record function-call-history-size unlimited
6846 Define how many lines to print in the
6847 @code{record function-call-history} command. The default value is 10.
6848 A size of @code{unlimited} means unlimited lines.
6850 @item show record function-call-history-size
6851 Show how many lines to print in the
6852 @code{record function-call-history} command.
6857 @chapter Examining the Stack
6859 When your program has stopped, the first thing you need to know is where it
6860 stopped and how it got there.
6863 Each time your program performs a function call, information about the call
6865 That information includes the location of the call in your program,
6866 the arguments of the call,
6867 and the local variables of the function being called.
6868 The information is saved in a block of data called a @dfn{stack frame}.
6869 The stack frames are allocated in a region of memory called the @dfn{call
6872 When your program stops, the @value{GDBN} commands for examining the
6873 stack allow you to see all of this information.
6875 @cindex selected frame
6876 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6877 @value{GDBN} commands refer implicitly to the selected frame. In
6878 particular, whenever you ask @value{GDBN} for the value of a variable in
6879 your program, the value is found in the selected frame. There are
6880 special @value{GDBN} commands to select whichever frame you are
6881 interested in. @xref{Selection, ,Selecting a Frame}.
6883 When your program stops, @value{GDBN} automatically selects the
6884 currently executing frame and describes it briefly, similar to the
6885 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6888 * Frames:: Stack frames
6889 * Backtrace:: Backtraces
6890 * Frame Filter Management:: Managing frame filters
6891 * Selection:: Selecting a frame
6892 * Frame Info:: Information on a frame
6897 @section Stack Frames
6899 @cindex frame, definition
6901 The call stack is divided up into contiguous pieces called @dfn{stack
6902 frames}, or @dfn{frames} for short; each frame is the data associated
6903 with one call to one function. The frame contains the arguments given
6904 to the function, the function's local variables, and the address at
6905 which the function is executing.
6907 @cindex initial frame
6908 @cindex outermost frame
6909 @cindex innermost frame
6910 When your program is started, the stack has only one frame, that of the
6911 function @code{main}. This is called the @dfn{initial} frame or the
6912 @dfn{outermost} frame. Each time a function is called, a new frame is
6913 made. Each time a function returns, the frame for that function invocation
6914 is eliminated. If a function is recursive, there can be many frames for
6915 the same function. The frame for the function in which execution is
6916 actually occurring is called the @dfn{innermost} frame. This is the most
6917 recently created of all the stack frames that still exist.
6919 @cindex frame pointer
6920 Inside your program, stack frames are identified by their addresses. A
6921 stack frame consists of many bytes, each of which has its own address; each
6922 kind of computer has a convention for choosing one byte whose
6923 address serves as the address of the frame. Usually this address is kept
6924 in a register called the @dfn{frame pointer register}
6925 (@pxref{Registers, $fp}) while execution is going on in that frame.
6927 @cindex frame number
6928 @value{GDBN} assigns numbers to all existing stack frames, starting with
6929 zero for the innermost frame, one for the frame that called it,
6930 and so on upward. These numbers do not really exist in your program;
6931 they are assigned by @value{GDBN} to give you a way of designating stack
6932 frames in @value{GDBN} commands.
6934 @c The -fomit-frame-pointer below perennially causes hbox overflow
6935 @c underflow problems.
6936 @cindex frameless execution
6937 Some compilers provide a way to compile functions so that they operate
6938 without stack frames. (For example, the @value{NGCC} option
6940 @samp{-fomit-frame-pointer}
6942 generates functions without a frame.)
6943 This is occasionally done with heavily used library functions to save
6944 the frame setup time. @value{GDBN} has limited facilities for dealing
6945 with these function invocations. If the innermost function invocation
6946 has no stack frame, @value{GDBN} nevertheless regards it as though
6947 it had a separate frame, which is numbered zero as usual, allowing
6948 correct tracing of the function call chain. However, @value{GDBN} has
6949 no provision for frameless functions elsewhere in the stack.
6952 @kindex frame@r{, command}
6953 @cindex current stack frame
6954 @item frame @r{[}@var{framespec}@r{]}
6955 The @code{frame} command allows you to move from one stack frame to another,
6956 and to print the stack frame you select. The @var{framespec} may be either the
6957 address of the frame or the stack frame number. Without an argument,
6958 @code{frame} prints the current stack frame.
6960 @kindex select-frame
6961 @cindex selecting frame silently
6963 The @code{select-frame} command allows you to move from one stack frame
6964 to another without printing the frame. This is the silent version of
6972 @cindex call stack traces
6973 A backtrace is a summary of how your program got where it is. It shows one
6974 line per frame, for many frames, starting with the currently executing
6975 frame (frame zero), followed by its caller (frame one), and on up the
6978 @anchor{backtrace-command}
6981 @kindex bt @r{(@code{backtrace})}
6984 Print a backtrace of the entire stack: one line per frame for all
6985 frames in the stack.
6987 You can stop the backtrace at any time by typing the system interrupt
6988 character, normally @kbd{Ctrl-c}.
6990 @item backtrace @var{n}
6992 Similar, but print only the innermost @var{n} frames.
6994 @item backtrace -@var{n}
6996 Similar, but print only the outermost @var{n} frames.
6998 @item backtrace full
7000 @itemx bt full @var{n}
7001 @itemx bt full -@var{n}
7002 Print the values of the local variables also. As described above,
7003 @var{n} specifies the number of frames to print.
7005 @item backtrace no-filters
7006 @itemx bt no-filters
7007 @itemx bt no-filters @var{n}
7008 @itemx bt no-filters -@var{n}
7009 @itemx bt no-filters full
7010 @itemx bt no-filters full @var{n}
7011 @itemx bt no-filters full -@var{n}
7012 Do not run Python frame filters on this backtrace. @xref{Frame
7013 Filter API}, for more information. Additionally use @ref{disable
7014 frame-filter all} to turn off all frame filters. This is only
7015 relevant when @value{GDBN} has been configured with @code{Python}
7021 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7022 are additional aliases for @code{backtrace}.
7024 @cindex multiple threads, backtrace
7025 In a multi-threaded program, @value{GDBN} by default shows the
7026 backtrace only for the current thread. To display the backtrace for
7027 several or all of the threads, use the command @code{thread apply}
7028 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7029 apply all backtrace}, @value{GDBN} will display the backtrace for all
7030 the threads; this is handy when you debug a core dump of a
7031 multi-threaded program.
7033 Each line in the backtrace shows the frame number and the function name.
7034 The program counter value is also shown---unless you use @code{set
7035 print address off}. The backtrace also shows the source file name and
7036 line number, as well as the arguments to the function. The program
7037 counter value is omitted if it is at the beginning of the code for that
7040 Here is an example of a backtrace. It was made with the command
7041 @samp{bt 3}, so it shows the innermost three frames.
7045 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7047 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7048 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7050 (More stack frames follow...)
7055 The display for frame zero does not begin with a program counter
7056 value, indicating that your program has stopped at the beginning of the
7057 code for line @code{993} of @code{builtin.c}.
7060 The value of parameter @code{data} in frame 1 has been replaced by
7061 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7062 only if it is a scalar (integer, pointer, enumeration, etc). See command
7063 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7064 on how to configure the way function parameter values are printed.
7066 @cindex optimized out, in backtrace
7067 @cindex function call arguments, optimized out
7068 If your program was compiled with optimizations, some compilers will
7069 optimize away arguments passed to functions if those arguments are
7070 never used after the call. Such optimizations generate code that
7071 passes arguments through registers, but doesn't store those arguments
7072 in the stack frame. @value{GDBN} has no way of displaying such
7073 arguments in stack frames other than the innermost one. Here's what
7074 such a backtrace might look like:
7078 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7080 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7081 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7083 (More stack frames follow...)
7088 The values of arguments that were not saved in their stack frames are
7089 shown as @samp{<optimized out>}.
7091 If you need to display the values of such optimized-out arguments,
7092 either deduce that from other variables whose values depend on the one
7093 you are interested in, or recompile without optimizations.
7095 @cindex backtrace beyond @code{main} function
7096 @cindex program entry point
7097 @cindex startup code, and backtrace
7098 Most programs have a standard user entry point---a place where system
7099 libraries and startup code transition into user code. For C this is
7100 @code{main}@footnote{
7101 Note that embedded programs (the so-called ``free-standing''
7102 environment) are not required to have a @code{main} function as the
7103 entry point. They could even have multiple entry points.}.
7104 When @value{GDBN} finds the entry function in a backtrace
7105 it will terminate the backtrace, to avoid tracing into highly
7106 system-specific (and generally uninteresting) code.
7108 If you need to examine the startup code, or limit the number of levels
7109 in a backtrace, you can change this behavior:
7112 @item set backtrace past-main
7113 @itemx set backtrace past-main on
7114 @kindex set backtrace
7115 Backtraces will continue past the user entry point.
7117 @item set backtrace past-main off
7118 Backtraces will stop when they encounter the user entry point. This is the
7121 @item show backtrace past-main
7122 @kindex show backtrace
7123 Display the current user entry point backtrace policy.
7125 @item set backtrace past-entry
7126 @itemx set backtrace past-entry on
7127 Backtraces will continue past the internal entry point of an application.
7128 This entry point is encoded by the linker when the application is built,
7129 and is likely before the user entry point @code{main} (or equivalent) is called.
7131 @item set backtrace past-entry off
7132 Backtraces will stop when they encounter the internal entry point of an
7133 application. This is the default.
7135 @item show backtrace past-entry
7136 Display the current internal entry point backtrace policy.
7138 @item set backtrace limit @var{n}
7139 @itemx set backtrace limit 0
7140 @itemx set backtrace limit unlimited
7141 @cindex backtrace limit
7142 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7143 or zero means unlimited levels.
7145 @item show backtrace limit
7146 Display the current limit on backtrace levels.
7149 You can control how file names are displayed.
7152 @item set filename-display
7153 @itemx set filename-display relative
7154 @cindex filename-display
7155 Display file names relative to the compilation directory. This is the default.
7157 @item set filename-display basename
7158 Display only basename of a filename.
7160 @item set filename-display absolute
7161 Display an absolute filename.
7163 @item show filename-display
7164 Show the current way to display filenames.
7167 @node Frame Filter Management
7168 @section Management of Frame Filters.
7169 @cindex managing frame filters
7171 Frame filters are Python based utilities to manage and decorate the
7172 output of frames. @xref{Frame Filter API}, for further information.
7174 Managing frame filters is performed by several commands available
7175 within @value{GDBN}, detailed here.
7178 @kindex info frame-filter
7179 @item info frame-filter
7180 Print a list of installed frame filters from all dictionaries, showing
7181 their name, priority and enabled status.
7183 @kindex disable frame-filter
7184 @anchor{disable frame-filter all}
7185 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7186 Disable a frame filter in the dictionary matching
7187 @var{filter-dictionary} and @var{filter-name}. The
7188 @var{filter-dictionary} may be @code{all}, @code{global},
7189 @code{progspace}, or the name of the object file where the frame filter
7190 dictionary resides. When @code{all} is specified, all frame filters
7191 across all dictionaries are disabled. The @var{filter-name} is the name
7192 of the frame filter and is used when @code{all} is not the option for
7193 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7194 may be enabled again later.
7196 @kindex enable frame-filter
7197 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7198 Enable a frame filter in the dictionary matching
7199 @var{filter-dictionary} and @var{filter-name}. The
7200 @var{filter-dictionary} may be @code{all}, @code{global},
7201 @code{progspace} or the name of the object file where the frame filter
7202 dictionary resides. When @code{all} is specified, all frame filters across
7203 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7204 filter and is used when @code{all} is not the option for
7205 @var{filter-dictionary}.
7210 (gdb) info frame-filter
7212 global frame-filters:
7213 Priority Enabled Name
7214 1000 No PrimaryFunctionFilter
7217 progspace /build/test frame-filters:
7218 Priority Enabled Name
7219 100 Yes ProgspaceFilter
7221 objfile /build/test frame-filters:
7222 Priority Enabled Name
7223 999 Yes BuildProgra Filter
7225 (gdb) disable frame-filter /build/test BuildProgramFilter
7226 (gdb) info frame-filter
7228 global frame-filters:
7229 Priority Enabled Name
7230 1000 No PrimaryFunctionFilter
7233 progspace /build/test frame-filters:
7234 Priority Enabled Name
7235 100 Yes ProgspaceFilter
7237 objfile /build/test frame-filters:
7238 Priority Enabled Name
7239 999 No BuildProgramFilter
7241 (gdb) enable frame-filter global PrimaryFunctionFilter
7242 (gdb) info frame-filter
7244 global frame-filters:
7245 Priority Enabled Name
7246 1000 Yes PrimaryFunctionFilter
7249 progspace /build/test frame-filters:
7250 Priority Enabled Name
7251 100 Yes ProgspaceFilter
7253 objfile /build/test frame-filters:
7254 Priority Enabled Name
7255 999 No BuildProgramFilter
7258 @kindex set frame-filter priority
7259 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7260 Set the @var{priority} of a frame filter in the dictionary matching
7261 @var{filter-dictionary}, and the frame filter name matching
7262 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7263 @code{progspace} or the name of the object file where the frame filter
7264 dictionary resides. The @var{priority} is an integer.
7266 @kindex show frame-filter priority
7267 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7268 Show the @var{priority} of a frame filter in the dictionary matching
7269 @var{filter-dictionary}, and the frame filter name matching
7270 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7271 @code{progspace} or the name of the object file where the frame filter
7277 (gdb) info frame-filter
7279 global frame-filters:
7280 Priority Enabled Name
7281 1000 Yes PrimaryFunctionFilter
7284 progspace /build/test frame-filters:
7285 Priority Enabled Name
7286 100 Yes ProgspaceFilter
7288 objfile /build/test frame-filters:
7289 Priority Enabled Name
7290 999 No BuildProgramFilter
7292 (gdb) set frame-filter priority global Reverse 50
7293 (gdb) info frame-filter
7295 global frame-filters:
7296 Priority Enabled Name
7297 1000 Yes PrimaryFunctionFilter
7300 progspace /build/test frame-filters:
7301 Priority Enabled Name
7302 100 Yes ProgspaceFilter
7304 objfile /build/test frame-filters:
7305 Priority Enabled Name
7306 999 No BuildProgramFilter
7311 @section Selecting a Frame
7313 Most commands for examining the stack and other data in your program work on
7314 whichever stack frame is selected at the moment. Here are the commands for
7315 selecting a stack frame; all of them finish by printing a brief description
7316 of the stack frame just selected.
7319 @kindex frame@r{, selecting}
7320 @kindex f @r{(@code{frame})}
7323 Select frame number @var{n}. Recall that frame zero is the innermost
7324 (currently executing) frame, frame one is the frame that called the
7325 innermost one, and so on. The highest-numbered frame is the one for
7328 @item frame @var{stack-addr} [ @var{pc-addr} ]
7329 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7330 Select the frame at address @var{stack-addr}. This is useful mainly if the
7331 chaining of stack frames has been damaged by a bug, making it
7332 impossible for @value{GDBN} to assign numbers properly to all frames. In
7333 addition, this can be useful when your program has multiple stacks and
7334 switches between them. The optional @var{pc-addr} can also be given to
7335 specify the value of PC for the stack frame.
7339 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7340 numbers @var{n}, this advances toward the outermost frame, to higher
7341 frame numbers, to frames that have existed longer.
7344 @kindex do @r{(@code{down})}
7346 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7347 positive numbers @var{n}, this advances toward the innermost frame, to
7348 lower frame numbers, to frames that were created more recently.
7349 You may abbreviate @code{down} as @code{do}.
7352 All of these commands end by printing two lines of output describing the
7353 frame. The first line shows the frame number, the function name, the
7354 arguments, and the source file and line number of execution in that
7355 frame. The second line shows the text of that source line.
7363 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7365 10 read_input_file (argv[i]);
7369 After such a printout, the @code{list} command with no arguments
7370 prints ten lines centered on the point of execution in the frame.
7371 You can also edit the program at the point of execution with your favorite
7372 editing program by typing @code{edit}.
7373 @xref{List, ,Printing Source Lines},
7377 @kindex down-silently
7379 @item up-silently @var{n}
7380 @itemx down-silently @var{n}
7381 These two commands are variants of @code{up} and @code{down},
7382 respectively; they differ in that they do their work silently, without
7383 causing display of the new frame. They are intended primarily for use
7384 in @value{GDBN} command scripts, where the output might be unnecessary and
7389 @section Information About a Frame
7391 There are several other commands to print information about the selected
7397 When used without any argument, this command does not change which
7398 frame is selected, but prints a brief description of the currently
7399 selected stack frame. It can be abbreviated @code{f}. With an
7400 argument, this command is used to select a stack frame.
7401 @xref{Selection, ,Selecting a Frame}.
7404 @kindex info f @r{(@code{info frame})}
7407 This command prints a verbose description of the selected stack frame,
7412 the address of the frame
7414 the address of the next frame down (called by this frame)
7416 the address of the next frame up (caller of this frame)
7418 the language in which the source code corresponding to this frame is written
7420 the address of the frame's arguments
7422 the address of the frame's local variables
7424 the program counter saved in it (the address of execution in the caller frame)
7426 which registers were saved in the frame
7429 @noindent The verbose description is useful when
7430 something has gone wrong that has made the stack format fail to fit
7431 the usual conventions.
7433 @item info frame @var{addr}
7434 @itemx info f @var{addr}
7435 Print a verbose description of the frame at address @var{addr}, without
7436 selecting that frame. The selected frame remains unchanged by this
7437 command. This requires the same kind of address (more than one for some
7438 architectures) that you specify in the @code{frame} command.
7439 @xref{Selection, ,Selecting a Frame}.
7443 Print the arguments of the selected frame, each on a separate line.
7447 Print the local variables of the selected frame, each on a separate
7448 line. These are all variables (declared either static or automatic)
7449 accessible at the point of execution of the selected frame.
7455 @chapter Examining Source Files
7457 @value{GDBN} can print parts of your program's source, since the debugging
7458 information recorded in the program tells @value{GDBN} what source files were
7459 used to build it. When your program stops, @value{GDBN} spontaneously prints
7460 the line where it stopped. Likewise, when you select a stack frame
7461 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7462 execution in that frame has stopped. You can print other portions of
7463 source files by explicit command.
7465 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7466 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7467 @value{GDBN} under @sc{gnu} Emacs}.
7470 * List:: Printing source lines
7471 * Specify Location:: How to specify code locations
7472 * Edit:: Editing source files
7473 * Search:: Searching source files
7474 * Source Path:: Specifying source directories
7475 * Machine Code:: Source and machine code
7479 @section Printing Source Lines
7482 @kindex l @r{(@code{list})}
7483 To print lines from a source file, use the @code{list} command
7484 (abbreviated @code{l}). By default, ten lines are printed.
7485 There are several ways to specify what part of the file you want to
7486 print; see @ref{Specify Location}, for the full list.
7488 Here are the forms of the @code{list} command most commonly used:
7491 @item list @var{linenum}
7492 Print lines centered around line number @var{linenum} in the
7493 current source file.
7495 @item list @var{function}
7496 Print lines centered around the beginning of function
7500 Print more lines. If the last lines printed were printed with a
7501 @code{list} command, this prints lines following the last lines
7502 printed; however, if the last line printed was a solitary line printed
7503 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7504 Stack}), this prints lines centered around that line.
7507 Print lines just before the lines last printed.
7510 @cindex @code{list}, how many lines to display
7511 By default, @value{GDBN} prints ten source lines with any of these forms of
7512 the @code{list} command. You can change this using @code{set listsize}:
7515 @kindex set listsize
7516 @item set listsize @var{count}
7517 @itemx set listsize unlimited
7518 Make the @code{list} command display @var{count} source lines (unless
7519 the @code{list} argument explicitly specifies some other number).
7520 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7522 @kindex show listsize
7524 Display the number of lines that @code{list} prints.
7527 Repeating a @code{list} command with @key{RET} discards the argument,
7528 so it is equivalent to typing just @code{list}. This is more useful
7529 than listing the same lines again. An exception is made for an
7530 argument of @samp{-}; that argument is preserved in repetition so that
7531 each repetition moves up in the source file.
7533 In general, the @code{list} command expects you to supply zero, one or two
7534 @dfn{locations}. Locations specify source lines; there are several ways
7535 of writing them (@pxref{Specify Location}), but the effect is always
7536 to specify some source line.
7538 Here is a complete description of the possible arguments for @code{list}:
7541 @item list @var{location}
7542 Print lines centered around the line specified by @var{location}.
7544 @item list @var{first},@var{last}
7545 Print lines from @var{first} to @var{last}. Both arguments are
7546 locations. When a @code{list} command has two locations, and the
7547 source file of the second location is omitted, this refers to
7548 the same source file as the first location.
7550 @item list ,@var{last}
7551 Print lines ending with @var{last}.
7553 @item list @var{first},
7554 Print lines starting with @var{first}.
7557 Print lines just after the lines last printed.
7560 Print lines just before the lines last printed.
7563 As described in the preceding table.
7566 @node Specify Location
7567 @section Specifying a Location
7568 @cindex specifying location
7570 @cindex source location
7573 * Linespec Locations:: Linespec locations
7574 * Explicit Locations:: Explicit locations
7575 * Address Locations:: Address locations
7578 Several @value{GDBN} commands accept arguments that specify a location
7579 of your program's code. Since @value{GDBN} is a source-level
7580 debugger, a location usually specifies some line in the source code.
7581 Locations may be specified using three different formats:
7582 linespec locations, explicit locations, or address locations.
7584 @node Linespec Locations
7585 @subsection Linespec Locations
7586 @cindex linespec locations
7588 A @dfn{linespec} is a colon-separated list of source location parameters such
7589 as file name, function name, etc. Here are all the different ways of
7590 specifying a linespec:
7594 Specifies the line number @var{linenum} of the current source file.
7597 @itemx +@var{offset}
7598 Specifies the line @var{offset} lines before or after the @dfn{current
7599 line}. For the @code{list} command, the current line is the last one
7600 printed; for the breakpoint commands, this is the line at which
7601 execution stopped in the currently selected @dfn{stack frame}
7602 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7603 used as the second of the two linespecs in a @code{list} command,
7604 this specifies the line @var{offset} lines up or down from the first
7607 @item @var{filename}:@var{linenum}
7608 Specifies the line @var{linenum} in the source file @var{filename}.
7609 If @var{filename} is a relative file name, then it will match any
7610 source file name with the same trailing components. For example, if
7611 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7612 name of @file{/build/trunk/gcc/expr.c}, but not
7613 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7615 @item @var{function}
7616 Specifies the line that begins the body of the function @var{function}.
7617 For example, in C, this is the line with the open brace.
7619 @item @var{function}:@var{label}
7620 Specifies the line where @var{label} appears in @var{function}.
7622 @item @var{filename}:@var{function}
7623 Specifies the line that begins the body of the function @var{function}
7624 in the file @var{filename}. You only need the file name with a
7625 function name to avoid ambiguity when there are identically named
7626 functions in different source files.
7629 Specifies the line at which the label named @var{label} appears
7630 in the function corresponding to the currently selected stack frame.
7631 If there is no current selected stack frame (for instance, if the inferior
7632 is not running), then @value{GDBN} will not search for a label.
7634 @cindex breakpoint at static probe point
7635 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7636 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7637 applications to embed static probes. @xref{Static Probe Points}, for more
7638 information on finding and using static probes. This form of linespec
7639 specifies the location of such a static probe.
7641 If @var{objfile} is given, only probes coming from that shared library
7642 or executable matching @var{objfile} as a regular expression are considered.
7643 If @var{provider} is given, then only probes from that provider are considered.
7644 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7645 each one of those probes.
7648 @node Explicit Locations
7649 @subsection Explicit Locations
7650 @cindex explicit locations
7652 @dfn{Explicit locations} allow the user to directly specify the source
7653 location's parameters using option-value pairs.
7655 Explicit locations are useful when several functions, labels, or
7656 file names have the same name (base name for files) in the program's
7657 sources. In these cases, explicit locations point to the source
7658 line you meant more accurately and unambiguously. Also, using
7659 explicit locations might be faster in large programs.
7661 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7662 defined in the file named @file{foo} or the label @code{bar} in a function
7663 named @code{foo}. @value{GDBN} must search either the file system or
7664 the symbol table to know.
7666 The list of valid explicit location options is summarized in the
7670 @item -source @var{filename}
7671 The value specifies the source file name. To differentiate between
7672 files with the same base name, prepend as many directories as is necessary
7673 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7674 @value{GDBN} will use the first file it finds with the given base
7675 name. This option requires the use of either @code{-function} or @code{-line}.
7677 @item -function @var{function}
7678 The value specifies the name of a function. Operations
7679 on function locations unmodified by other options (such as @code{-label}
7680 or @code{-line}) refer to the line that begins the body of the function.
7681 In C, for example, this is the line with the open brace.
7683 @item -label @var{label}
7684 The value specifies the name of a label. When the function
7685 name is not specified, the label is searched in the function of the currently
7686 selected stack frame.
7688 @item -line @var{number}
7689 The value specifies a line offset for the location. The offset may either
7690 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7691 the command. When specified without any other options, the line offset is
7692 relative to the current line.
7695 Explicit location options may be abbreviated by omitting any non-unique
7696 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7698 @node Address Locations
7699 @subsection Address Locations
7700 @cindex address locations
7702 @dfn{Address locations} indicate a specific program address. They have
7703 the generalized form *@var{address}.
7705 For line-oriented commands, such as @code{list} and @code{edit}, this
7706 specifies a source line that contains @var{address}. For @code{break} and
7707 other breakpoint-oriented commands, this can be used to set breakpoints in
7708 parts of your program which do not have debugging information or
7711 Here @var{address} may be any expression valid in the current working
7712 language (@pxref{Languages, working language}) that specifies a code
7713 address. In addition, as a convenience, @value{GDBN} extends the
7714 semantics of expressions used in locations to cover several situations
7715 that frequently occur during debugging. Here are the various forms
7719 @item @var{expression}
7720 Any expression valid in the current working language.
7722 @item @var{funcaddr}
7723 An address of a function or procedure derived from its name. In C,
7724 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7725 simply the function's name @var{function} (and actually a special case
7726 of a valid expression). In Pascal and Modula-2, this is
7727 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7728 (although the Pascal form also works).
7730 This form specifies the address of the function's first instruction,
7731 before the stack frame and arguments have been set up.
7733 @item '@var{filename}':@var{funcaddr}
7734 Like @var{funcaddr} above, but also specifies the name of the source
7735 file explicitly. This is useful if the name of the function does not
7736 specify the function unambiguously, e.g., if there are several
7737 functions with identical names in different source files.
7741 @section Editing Source Files
7742 @cindex editing source files
7745 @kindex e @r{(@code{edit})}
7746 To edit the lines in a source file, use the @code{edit} command.
7747 The editing program of your choice
7748 is invoked with the current line set to
7749 the active line in the program.
7750 Alternatively, there are several ways to specify what part of the file you
7751 want to print if you want to see other parts of the program:
7754 @item edit @var{location}
7755 Edit the source file specified by @code{location}. Editing starts at
7756 that @var{location}, e.g., at the specified source line of the
7757 specified file. @xref{Specify Location}, for all the possible forms
7758 of the @var{location} argument; here are the forms of the @code{edit}
7759 command most commonly used:
7762 @item edit @var{number}
7763 Edit the current source file with @var{number} as the active line number.
7765 @item edit @var{function}
7766 Edit the file containing @var{function} at the beginning of its definition.
7771 @subsection Choosing your Editor
7772 You can customize @value{GDBN} to use any editor you want
7774 The only restriction is that your editor (say @code{ex}), recognizes the
7775 following command-line syntax:
7777 ex +@var{number} file
7779 The optional numeric value +@var{number} specifies the number of the line in
7780 the file where to start editing.}.
7781 By default, it is @file{@value{EDITOR}}, but you can change this
7782 by setting the environment variable @code{EDITOR} before using
7783 @value{GDBN}. For example, to configure @value{GDBN} to use the
7784 @code{vi} editor, you could use these commands with the @code{sh} shell:
7790 or in the @code{csh} shell,
7792 setenv EDITOR /usr/bin/vi
7797 @section Searching Source Files
7798 @cindex searching source files
7800 There are two commands for searching through the current source file for a
7805 @kindex forward-search
7806 @kindex fo @r{(@code{forward-search})}
7807 @item forward-search @var{regexp}
7808 @itemx search @var{regexp}
7809 The command @samp{forward-search @var{regexp}} checks each line,
7810 starting with the one following the last line listed, for a match for
7811 @var{regexp}. It lists the line that is found. You can use the
7812 synonym @samp{search @var{regexp}} or abbreviate the command name as
7815 @kindex reverse-search
7816 @item reverse-search @var{regexp}
7817 The command @samp{reverse-search @var{regexp}} checks each line, starting
7818 with the one before the last line listed and going backward, for a match
7819 for @var{regexp}. It lists the line that is found. You can abbreviate
7820 this command as @code{rev}.
7824 @section Specifying Source Directories
7827 @cindex directories for source files
7828 Executable programs sometimes do not record the directories of the source
7829 files from which they were compiled, just the names. Even when they do,
7830 the directories could be moved between the compilation and your debugging
7831 session. @value{GDBN} has a list of directories to search for source files;
7832 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7833 it tries all the directories in the list, in the order they are present
7834 in the list, until it finds a file with the desired name.
7836 For example, suppose an executable references the file
7837 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7838 @file{/mnt/cross}. The file is first looked up literally; if this
7839 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7840 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7841 message is printed. @value{GDBN} does not look up the parts of the
7842 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7843 Likewise, the subdirectories of the source path are not searched: if
7844 the source path is @file{/mnt/cross}, and the binary refers to
7845 @file{foo.c}, @value{GDBN} would not find it under
7846 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7848 Plain file names, relative file names with leading directories, file
7849 names containing dots, etc.@: are all treated as described above; for
7850 instance, if the source path is @file{/mnt/cross}, and the source file
7851 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7852 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7853 that---@file{/mnt/cross/foo.c}.
7855 Note that the executable search path is @emph{not} used to locate the
7858 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7859 any information it has cached about where source files are found and where
7860 each line is in the file.
7864 When you start @value{GDBN}, its source path includes only @samp{cdir}
7865 and @samp{cwd}, in that order.
7866 To add other directories, use the @code{directory} command.
7868 The search path is used to find both program source files and @value{GDBN}
7869 script files (read using the @samp{-command} option and @samp{source} command).
7871 In addition to the source path, @value{GDBN} provides a set of commands
7872 that manage a list of source path substitution rules. A @dfn{substitution
7873 rule} specifies how to rewrite source directories stored in the program's
7874 debug information in case the sources were moved to a different
7875 directory between compilation and debugging. A rule is made of
7876 two strings, the first specifying what needs to be rewritten in
7877 the path, and the second specifying how it should be rewritten.
7878 In @ref{set substitute-path}, we name these two parts @var{from} and
7879 @var{to} respectively. @value{GDBN} does a simple string replacement
7880 of @var{from} with @var{to} at the start of the directory part of the
7881 source file name, and uses that result instead of the original file
7882 name to look up the sources.
7884 Using the previous example, suppose the @file{foo-1.0} tree has been
7885 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7886 @value{GDBN} to replace @file{/usr/src} in all source path names with
7887 @file{/mnt/cross}. The first lookup will then be
7888 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7889 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7890 substitution rule, use the @code{set substitute-path} command
7891 (@pxref{set substitute-path}).
7893 To avoid unexpected substitution results, a rule is applied only if the
7894 @var{from} part of the directory name ends at a directory separator.
7895 For instance, a rule substituting @file{/usr/source} into
7896 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7897 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7898 is applied only at the beginning of the directory name, this rule will
7899 not be applied to @file{/root/usr/source/baz.c} either.
7901 In many cases, you can achieve the same result using the @code{directory}
7902 command. However, @code{set substitute-path} can be more efficient in
7903 the case where the sources are organized in a complex tree with multiple
7904 subdirectories. With the @code{directory} command, you need to add each
7905 subdirectory of your project. If you moved the entire tree while
7906 preserving its internal organization, then @code{set substitute-path}
7907 allows you to direct the debugger to all the sources with one single
7910 @code{set substitute-path} is also more than just a shortcut command.
7911 The source path is only used if the file at the original location no
7912 longer exists. On the other hand, @code{set substitute-path} modifies
7913 the debugger behavior to look at the rewritten location instead. So, if
7914 for any reason a source file that is not relevant to your executable is
7915 located at the original location, a substitution rule is the only
7916 method available to point @value{GDBN} at the new location.
7918 @cindex @samp{--with-relocated-sources}
7919 @cindex default source path substitution
7920 You can configure a default source path substitution rule by
7921 configuring @value{GDBN} with the
7922 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7923 should be the name of a directory under @value{GDBN}'s configured
7924 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7925 directory names in debug information under @var{dir} will be adjusted
7926 automatically if the installed @value{GDBN} is moved to a new
7927 location. This is useful if @value{GDBN}, libraries or executables
7928 with debug information and corresponding source code are being moved
7932 @item directory @var{dirname} @dots{}
7933 @item dir @var{dirname} @dots{}
7934 Add directory @var{dirname} to the front of the source path. Several
7935 directory names may be given to this command, separated by @samp{:}
7936 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7937 part of absolute file names) or
7938 whitespace. You may specify a directory that is already in the source
7939 path; this moves it forward, so @value{GDBN} searches it sooner.
7943 @vindex $cdir@r{, convenience variable}
7944 @vindex $cwd@r{, convenience variable}
7945 @cindex compilation directory
7946 @cindex current directory
7947 @cindex working directory
7948 @cindex directory, current
7949 @cindex directory, compilation
7950 You can use the string @samp{$cdir} to refer to the compilation
7951 directory (if one is recorded), and @samp{$cwd} to refer to the current
7952 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7953 tracks the current working directory as it changes during your @value{GDBN}
7954 session, while the latter is immediately expanded to the current
7955 directory at the time you add an entry to the source path.
7958 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7960 @c RET-repeat for @code{directory} is explicitly disabled, but since
7961 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7963 @item set directories @var{path-list}
7964 @kindex set directories
7965 Set the source path to @var{path-list}.
7966 @samp{$cdir:$cwd} are added if missing.
7968 @item show directories
7969 @kindex show directories
7970 Print the source path: show which directories it contains.
7972 @anchor{set substitute-path}
7973 @item set substitute-path @var{from} @var{to}
7974 @kindex set substitute-path
7975 Define a source path substitution rule, and add it at the end of the
7976 current list of existing substitution rules. If a rule with the same
7977 @var{from} was already defined, then the old rule is also deleted.
7979 For example, if the file @file{/foo/bar/baz.c} was moved to
7980 @file{/mnt/cross/baz.c}, then the command
7983 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7987 will tell @value{GDBN} to replace @samp{/usr/src} with
7988 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7989 @file{baz.c} even though it was moved.
7991 In the case when more than one substitution rule have been defined,
7992 the rules are evaluated one by one in the order where they have been
7993 defined. The first one matching, if any, is selected to perform
7996 For instance, if we had entered the following commands:
7999 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8000 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8004 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8005 @file{/mnt/include/defs.h} by using the first rule. However, it would
8006 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8007 @file{/mnt/src/lib/foo.c}.
8010 @item unset substitute-path [path]
8011 @kindex unset substitute-path
8012 If a path is specified, search the current list of substitution rules
8013 for a rule that would rewrite that path. Delete that rule if found.
8014 A warning is emitted by the debugger if no rule could be found.
8016 If no path is specified, then all substitution rules are deleted.
8018 @item show substitute-path [path]
8019 @kindex show substitute-path
8020 If a path is specified, then print the source path substitution rule
8021 which would rewrite that path, if any.
8023 If no path is specified, then print all existing source path substitution
8028 If your source path is cluttered with directories that are no longer of
8029 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8030 versions of source. You can correct the situation as follows:
8034 Use @code{directory} with no argument to reset the source path to its default value.
8037 Use @code{directory} with suitable arguments to reinstall the
8038 directories you want in the source path. You can add all the
8039 directories in one command.
8043 @section Source and Machine Code
8044 @cindex source line and its code address
8046 You can use the command @code{info line} to map source lines to program
8047 addresses (and vice versa), and the command @code{disassemble} to display
8048 a range of addresses as machine instructions. You can use the command
8049 @code{set disassemble-next-line} to set whether to disassemble next
8050 source line when execution stops. When run under @sc{gnu} Emacs
8051 mode, the @code{info line} command causes the arrow to point to the
8052 line specified. Also, @code{info line} prints addresses in symbolic form as
8057 @item info line @var{location}
8058 Print the starting and ending addresses of the compiled code for
8059 source line @var{location}. You can specify source lines in any of
8060 the ways documented in @ref{Specify Location}.
8063 For example, we can use @code{info line} to discover the location of
8064 the object code for the first line of function
8065 @code{m4_changequote}:
8067 @c FIXME: I think this example should also show the addresses in
8068 @c symbolic form, as they usually would be displayed.
8070 (@value{GDBP}) info line m4_changequote
8071 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8075 @cindex code address and its source line
8076 We can also inquire (using @code{*@var{addr}} as the form for
8077 @var{location}) what source line covers a particular address:
8079 (@value{GDBP}) info line *0x63ff
8080 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8083 @cindex @code{$_} and @code{info line}
8084 @cindex @code{x} command, default address
8085 @kindex x@r{(examine), and} info line
8086 After @code{info line}, the default address for the @code{x} command
8087 is changed to the starting address of the line, so that @samp{x/i} is
8088 sufficient to begin examining the machine code (@pxref{Memory,
8089 ,Examining Memory}). Also, this address is saved as the value of the
8090 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8095 @cindex assembly instructions
8096 @cindex instructions, assembly
8097 @cindex machine instructions
8098 @cindex listing machine instructions
8100 @itemx disassemble /m
8101 @itemx disassemble /s
8102 @itemx disassemble /r
8103 This specialized command dumps a range of memory as machine
8104 instructions. It can also print mixed source+disassembly by specifying
8105 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8106 as well as in symbolic form by specifying the @code{/r} modifier.
8107 The default memory range is the function surrounding the
8108 program counter of the selected frame. A single argument to this
8109 command is a program counter value; @value{GDBN} dumps the function
8110 surrounding this value. When two arguments are given, they should
8111 be separated by a comma, possibly surrounded by whitespace. The
8112 arguments specify a range of addresses to dump, in one of two forms:
8115 @item @var{start},@var{end}
8116 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8117 @item @var{start},+@var{length}
8118 the addresses from @var{start} (inclusive) to
8119 @code{@var{start}+@var{length}} (exclusive).
8123 When 2 arguments are specified, the name of the function is also
8124 printed (since there could be several functions in the given range).
8126 The argument(s) can be any expression yielding a numeric value, such as
8127 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8129 If the range of memory being disassembled contains current program counter,
8130 the instruction at that location is shown with a @code{=>} marker.
8133 The following example shows the disassembly of a range of addresses of
8134 HP PA-RISC 2.0 code:
8137 (@value{GDBP}) disas 0x32c4, 0x32e4
8138 Dump of assembler code from 0x32c4 to 0x32e4:
8139 0x32c4 <main+204>: addil 0,dp
8140 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8141 0x32cc <main+212>: ldil 0x3000,r31
8142 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8143 0x32d4 <main+220>: ldo 0(r31),rp
8144 0x32d8 <main+224>: addil -0x800,dp
8145 0x32dc <main+228>: ldo 0x588(r1),r26
8146 0x32e0 <main+232>: ldil 0x3000,r31
8147 End of assembler dump.
8150 Here is an example showing mixed source+assembly for Intel x86
8151 with @code{/m} or @code{/s}, when the program is stopped just after
8152 function prologue in a non-optimized function with no inline code.
8155 (@value{GDBP}) disas /m main
8156 Dump of assembler code for function main:
8158 0x08048330 <+0>: push %ebp
8159 0x08048331 <+1>: mov %esp,%ebp
8160 0x08048333 <+3>: sub $0x8,%esp
8161 0x08048336 <+6>: and $0xfffffff0,%esp
8162 0x08048339 <+9>: sub $0x10,%esp
8164 6 printf ("Hello.\n");
8165 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8166 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8170 0x08048348 <+24>: mov $0x0,%eax
8171 0x0804834d <+29>: leave
8172 0x0804834e <+30>: ret
8174 End of assembler dump.
8177 The @code{/m} option is deprecated as its output is not useful when
8178 there is either inlined code or re-ordered code.
8179 The @code{/s} option is the preferred choice.
8180 Here is an example for AMD x86-64 showing the difference between
8181 @code{/m} output and @code{/s} output.
8182 This example has one inline function defined in a header file,
8183 and the code is compiled with @samp{-O2} optimization.
8184 Note how the @code{/m} output is missing the disassembly of
8185 several instructions that are present in the @code{/s} output.
8215 (@value{GDBP}) disas /m main
8216 Dump of assembler code for function main:
8220 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8221 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8225 0x000000000040041d <+29>: xor %eax,%eax
8226 0x000000000040041f <+31>: retq
8227 0x0000000000400420 <+32>: add %eax,%eax
8228 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8230 End of assembler dump.
8231 (@value{GDBP}) disas /s main
8232 Dump of assembler code for function main:
8236 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8240 0x0000000000400406 <+6>: test %eax,%eax
8241 0x0000000000400408 <+8>: js 0x400420 <main+32>
8246 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8247 0x000000000040040d <+13>: test %eax,%eax
8248 0x000000000040040f <+15>: mov $0x1,%eax
8249 0x0000000000400414 <+20>: cmovne %edx,%eax
8253 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8257 0x000000000040041d <+29>: xor %eax,%eax
8258 0x000000000040041f <+31>: retq
8262 0x0000000000400420 <+32>: add %eax,%eax
8263 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8264 End of assembler dump.
8267 Here is another example showing raw instructions in hex for AMD x86-64,
8270 (gdb) disas /r 0x400281,+10
8271 Dump of assembler code from 0x400281 to 0x40028b:
8272 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8273 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8274 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8275 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8276 End of assembler dump.
8279 Addresses cannot be specified as a location (@pxref{Specify Location}).
8280 So, for example, if you want to disassemble function @code{bar}
8281 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8282 and not @samp{disassemble foo.c:bar}.
8284 Some architectures have more than one commonly-used set of instruction
8285 mnemonics or other syntax.
8287 For programs that were dynamically linked and use shared libraries,
8288 instructions that call functions or branch to locations in the shared
8289 libraries might show a seemingly bogus location---it's actually a
8290 location of the relocation table. On some architectures, @value{GDBN}
8291 might be able to resolve these to actual function names.
8294 @kindex set disassembly-flavor
8295 @cindex Intel disassembly flavor
8296 @cindex AT&T disassembly flavor
8297 @item set disassembly-flavor @var{instruction-set}
8298 Select the instruction set to use when disassembling the
8299 program via the @code{disassemble} or @code{x/i} commands.
8301 Currently this command is only defined for the Intel x86 family. You
8302 can set @var{instruction-set} to either @code{intel} or @code{att}.
8303 The default is @code{att}, the AT&T flavor used by default by Unix
8304 assemblers for x86-based targets.
8306 @kindex show disassembly-flavor
8307 @item show disassembly-flavor
8308 Show the current setting of the disassembly flavor.
8312 @kindex set disassemble-next-line
8313 @kindex show disassemble-next-line
8314 @item set disassemble-next-line
8315 @itemx show disassemble-next-line
8316 Control whether or not @value{GDBN} will disassemble the next source
8317 line or instruction when execution stops. If ON, @value{GDBN} will
8318 display disassembly of the next source line when execution of the
8319 program being debugged stops. This is @emph{in addition} to
8320 displaying the source line itself, which @value{GDBN} always does if
8321 possible. If the next source line cannot be displayed for some reason
8322 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8323 info in the debug info), @value{GDBN} will display disassembly of the
8324 next @emph{instruction} instead of showing the next source line. If
8325 AUTO, @value{GDBN} will display disassembly of next instruction only
8326 if the source line cannot be displayed. This setting causes
8327 @value{GDBN} to display some feedback when you step through a function
8328 with no line info or whose source file is unavailable. The default is
8329 OFF, which means never display the disassembly of the next line or
8335 @chapter Examining Data
8337 @cindex printing data
8338 @cindex examining data
8341 The usual way to examine data in your program is with the @code{print}
8342 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8343 evaluates and prints the value of an expression of the language your
8344 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8345 Different Languages}). It may also print the expression using a
8346 Python-based pretty-printer (@pxref{Pretty Printing}).
8349 @item print @var{expr}
8350 @itemx print /@var{f} @var{expr}
8351 @var{expr} is an expression (in the source language). By default the
8352 value of @var{expr} is printed in a format appropriate to its data type;
8353 you can choose a different format by specifying @samp{/@var{f}}, where
8354 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8358 @itemx print /@var{f}
8359 @cindex reprint the last value
8360 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8361 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8362 conveniently inspect the same value in an alternative format.
8365 A more low-level way of examining data is with the @code{x} command.
8366 It examines data in memory at a specified address and prints it in a
8367 specified format. @xref{Memory, ,Examining Memory}.
8369 If you are interested in information about types, or about how the
8370 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8371 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8374 @cindex exploring hierarchical data structures
8376 Another way of examining values of expressions and type information is
8377 through the Python extension command @code{explore} (available only if
8378 the @value{GDBN} build is configured with @code{--with-python}). It
8379 offers an interactive way to start at the highest level (or, the most
8380 abstract level) of the data type of an expression (or, the data type
8381 itself) and explore all the way down to leaf scalar values/fields
8382 embedded in the higher level data types.
8385 @item explore @var{arg}
8386 @var{arg} is either an expression (in the source language), or a type
8387 visible in the current context of the program being debugged.
8390 The working of the @code{explore} command can be illustrated with an
8391 example. If a data type @code{struct ComplexStruct} is defined in your
8401 struct ComplexStruct
8403 struct SimpleStruct *ss_p;
8409 followed by variable declarations as
8412 struct SimpleStruct ss = @{ 10, 1.11 @};
8413 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8417 then, the value of the variable @code{cs} can be explored using the
8418 @code{explore} command as follows.
8422 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8423 the following fields:
8425 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8426 arr = <Enter 1 to explore this field of type `int [10]'>
8428 Enter the field number of choice:
8432 Since the fields of @code{cs} are not scalar values, you are being
8433 prompted to chose the field you want to explore. Let's say you choose
8434 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8435 pointer, you will be asked if it is pointing to a single value. From
8436 the declaration of @code{cs} above, it is indeed pointing to a single
8437 value, hence you enter @code{y}. If you enter @code{n}, then you will
8438 be asked if it were pointing to an array of values, in which case this
8439 field will be explored as if it were an array.
8442 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8443 Continue exploring it as a pointer to a single value [y/n]: y
8444 The value of `*(cs.ss_p)' is a struct/class of type `struct
8445 SimpleStruct' with the following fields:
8447 i = 10 .. (Value of type `int')
8448 d = 1.1100000000000001 .. (Value of type `double')
8450 Press enter to return to parent value:
8454 If the field @code{arr} of @code{cs} was chosen for exploration by
8455 entering @code{1} earlier, then since it is as array, you will be
8456 prompted to enter the index of the element in the array that you want
8460 `cs.arr' is an array of `int'.
8461 Enter the index of the element you want to explore in `cs.arr': 5
8463 `(cs.arr)[5]' is a scalar value of type `int'.
8467 Press enter to return to parent value:
8470 In general, at any stage of exploration, you can go deeper towards the
8471 leaf values by responding to the prompts appropriately, or hit the
8472 return key to return to the enclosing data structure (the @i{higher}
8473 level data structure).
8475 Similar to exploring values, you can use the @code{explore} command to
8476 explore types. Instead of specifying a value (which is typically a
8477 variable name or an expression valid in the current context of the
8478 program being debugged), you specify a type name. If you consider the
8479 same example as above, your can explore the type
8480 @code{struct ComplexStruct} by passing the argument
8481 @code{struct ComplexStruct} to the @code{explore} command.
8484 (gdb) explore struct ComplexStruct
8488 By responding to the prompts appropriately in the subsequent interactive
8489 session, you can explore the type @code{struct ComplexStruct} in a
8490 manner similar to how the value @code{cs} was explored in the above
8493 The @code{explore} command also has two sub-commands,
8494 @code{explore value} and @code{explore type}. The former sub-command is
8495 a way to explicitly specify that value exploration of the argument is
8496 being invoked, while the latter is a way to explicitly specify that type
8497 exploration of the argument is being invoked.
8500 @item explore value @var{expr}
8501 @cindex explore value
8502 This sub-command of @code{explore} explores the value of the
8503 expression @var{expr} (if @var{expr} is an expression valid in the
8504 current context of the program being debugged). The behavior of this
8505 command is identical to that of the behavior of the @code{explore}
8506 command being passed the argument @var{expr}.
8508 @item explore type @var{arg}
8509 @cindex explore type
8510 This sub-command of @code{explore} explores the type of @var{arg} (if
8511 @var{arg} is a type visible in the current context of program being
8512 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8513 is an expression valid in the current context of the program being
8514 debugged). If @var{arg} is a type, then the behavior of this command is
8515 identical to that of the @code{explore} command being passed the
8516 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8517 this command will be identical to that of the @code{explore} command
8518 being passed the type of @var{arg} as the argument.
8522 * Expressions:: Expressions
8523 * Ambiguous Expressions:: Ambiguous Expressions
8524 * Variables:: Program variables
8525 * Arrays:: Artificial arrays
8526 * Output Formats:: Output formats
8527 * Memory:: Examining memory
8528 * Auto Display:: Automatic display
8529 * Print Settings:: Print settings
8530 * Pretty Printing:: Python pretty printing
8531 * Value History:: Value history
8532 * Convenience Vars:: Convenience variables
8533 * Convenience Funs:: Convenience functions
8534 * Registers:: Registers
8535 * Floating Point Hardware:: Floating point hardware
8536 * Vector Unit:: Vector Unit
8537 * OS Information:: Auxiliary data provided by operating system
8538 * Memory Region Attributes:: Memory region attributes
8539 * Dump/Restore Files:: Copy between memory and a file
8540 * Core File Generation:: Cause a program dump its core
8541 * Character Sets:: Debugging programs that use a different
8542 character set than GDB does
8543 * Caching Target Data:: Data caching for targets
8544 * Searching Memory:: Searching memory for a sequence of bytes
8548 @section Expressions
8551 @code{print} and many other @value{GDBN} commands accept an expression and
8552 compute its value. Any kind of constant, variable or operator defined
8553 by the programming language you are using is valid in an expression in
8554 @value{GDBN}. This includes conditional expressions, function calls,
8555 casts, and string constants. It also includes preprocessor macros, if
8556 you compiled your program to include this information; see
8559 @cindex arrays in expressions
8560 @value{GDBN} supports array constants in expressions input by
8561 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8562 you can use the command @code{print @{1, 2, 3@}} to create an array
8563 of three integers. If you pass an array to a function or assign it
8564 to a program variable, @value{GDBN} copies the array to memory that
8565 is @code{malloc}ed in the target program.
8567 Because C is so widespread, most of the expressions shown in examples in
8568 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8569 Languages}, for information on how to use expressions in other
8572 In this section, we discuss operators that you can use in @value{GDBN}
8573 expressions regardless of your programming language.
8575 @cindex casts, in expressions
8576 Casts are supported in all languages, not just in C, because it is so
8577 useful to cast a number into a pointer in order to examine a structure
8578 at that address in memory.
8579 @c FIXME: casts supported---Mod2 true?
8581 @value{GDBN} supports these operators, in addition to those common
8582 to programming languages:
8586 @samp{@@} is a binary operator for treating parts of memory as arrays.
8587 @xref{Arrays, ,Artificial Arrays}, for more information.
8590 @samp{::} allows you to specify a variable in terms of the file or
8591 function where it is defined. @xref{Variables, ,Program Variables}.
8593 @cindex @{@var{type}@}
8594 @cindex type casting memory
8595 @cindex memory, viewing as typed object
8596 @cindex casts, to view memory
8597 @item @{@var{type}@} @var{addr}
8598 Refers to an object of type @var{type} stored at address @var{addr} in
8599 memory. The address @var{addr} may be any expression whose value is
8600 an integer or pointer (but parentheses are required around binary
8601 operators, just as in a cast). This construct is allowed regardless
8602 of what kind of data is normally supposed to reside at @var{addr}.
8605 @node Ambiguous Expressions
8606 @section Ambiguous Expressions
8607 @cindex ambiguous expressions
8609 Expressions can sometimes contain some ambiguous elements. For instance,
8610 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8611 a single function name to be defined several times, for application in
8612 different contexts. This is called @dfn{overloading}. Another example
8613 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8614 templates and is typically instantiated several times, resulting in
8615 the same function name being defined in different contexts.
8617 In some cases and depending on the language, it is possible to adjust
8618 the expression to remove the ambiguity. For instance in C@t{++}, you
8619 can specify the signature of the function you want to break on, as in
8620 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8621 qualified name of your function often makes the expression unambiguous
8624 When an ambiguity that needs to be resolved is detected, the debugger
8625 has the capability to display a menu of numbered choices for each
8626 possibility, and then waits for the selection with the prompt @samp{>}.
8627 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8628 aborts the current command. If the command in which the expression was
8629 used allows more than one choice to be selected, the next option in the
8630 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8633 For example, the following session excerpt shows an attempt to set a
8634 breakpoint at the overloaded symbol @code{String::after}.
8635 We choose three particular definitions of that function name:
8637 @c FIXME! This is likely to change to show arg type lists, at least
8640 (@value{GDBP}) b String::after
8643 [2] file:String.cc; line number:867
8644 [3] file:String.cc; line number:860
8645 [4] file:String.cc; line number:875
8646 [5] file:String.cc; line number:853
8647 [6] file:String.cc; line number:846
8648 [7] file:String.cc; line number:735
8650 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8651 Breakpoint 2 at 0xb344: file String.cc, line 875.
8652 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8653 Multiple breakpoints were set.
8654 Use the "delete" command to delete unwanted
8661 @kindex set multiple-symbols
8662 @item set multiple-symbols @var{mode}
8663 @cindex multiple-symbols menu
8665 This option allows you to adjust the debugger behavior when an expression
8668 By default, @var{mode} is set to @code{all}. If the command with which
8669 the expression is used allows more than one choice, then @value{GDBN}
8670 automatically selects all possible choices. For instance, inserting
8671 a breakpoint on a function using an ambiguous name results in a breakpoint
8672 inserted on each possible match. However, if a unique choice must be made,
8673 then @value{GDBN} uses the menu to help you disambiguate the expression.
8674 For instance, printing the address of an overloaded function will result
8675 in the use of the menu.
8677 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8678 when an ambiguity is detected.
8680 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8681 an error due to the ambiguity and the command is aborted.
8683 @kindex show multiple-symbols
8684 @item show multiple-symbols
8685 Show the current value of the @code{multiple-symbols} setting.
8689 @section Program Variables
8691 The most common kind of expression to use is the name of a variable
8694 Variables in expressions are understood in the selected stack frame
8695 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8699 global (or file-static)
8706 visible according to the scope rules of the
8707 programming language from the point of execution in that frame
8710 @noindent This means that in the function
8725 you can examine and use the variable @code{a} whenever your program is
8726 executing within the function @code{foo}, but you can only use or
8727 examine the variable @code{b} while your program is executing inside
8728 the block where @code{b} is declared.
8730 @cindex variable name conflict
8731 There is an exception: you can refer to a variable or function whose
8732 scope is a single source file even if the current execution point is not
8733 in this file. But it is possible to have more than one such variable or
8734 function with the same name (in different source files). If that
8735 happens, referring to that name has unpredictable effects. If you wish,
8736 you can specify a static variable in a particular function or file by
8737 using the colon-colon (@code{::}) notation:
8739 @cindex colon-colon, context for variables/functions
8741 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8742 @cindex @code{::}, context for variables/functions
8745 @var{file}::@var{variable}
8746 @var{function}::@var{variable}
8750 Here @var{file} or @var{function} is the name of the context for the
8751 static @var{variable}. In the case of file names, you can use quotes to
8752 make sure @value{GDBN} parses the file name as a single word---for example,
8753 to print a global value of @code{x} defined in @file{f2.c}:
8756 (@value{GDBP}) p 'f2.c'::x
8759 The @code{::} notation is normally used for referring to
8760 static variables, since you typically disambiguate uses of local variables
8761 in functions by selecting the appropriate frame and using the
8762 simple name of the variable. However, you may also use this notation
8763 to refer to local variables in frames enclosing the selected frame:
8772 process (a); /* Stop here */
8783 For example, if there is a breakpoint at the commented line,
8784 here is what you might see
8785 when the program stops after executing the call @code{bar(0)}:
8790 (@value{GDBP}) p bar::a
8793 #2 0x080483d0 in foo (a=5) at foobar.c:12
8796 (@value{GDBP}) p bar::a
8800 @cindex C@t{++} scope resolution
8801 These uses of @samp{::} are very rarely in conflict with the very
8802 similar use of the same notation in C@t{++}. When they are in
8803 conflict, the C@t{++} meaning takes precedence; however, this can be
8804 overridden by quoting the file or function name with single quotes.
8806 For example, suppose the program is stopped in a method of a class
8807 that has a field named @code{includefile}, and there is also an
8808 include file named @file{includefile} that defines a variable,
8812 (@value{GDBP}) p includefile
8814 (@value{GDBP}) p includefile::some_global
8815 A syntax error in expression, near `'.
8816 (@value{GDBP}) p 'includefile'::some_global
8820 @cindex wrong values
8821 @cindex variable values, wrong
8822 @cindex function entry/exit, wrong values of variables
8823 @cindex optimized code, wrong values of variables
8825 @emph{Warning:} Occasionally, a local variable may appear to have the
8826 wrong value at certain points in a function---just after entry to a new
8827 scope, and just before exit.
8829 You may see this problem when you are stepping by machine instructions.
8830 This is because, on most machines, it takes more than one instruction to
8831 set up a stack frame (including local variable definitions); if you are
8832 stepping by machine instructions, variables may appear to have the wrong
8833 values until the stack frame is completely built. On exit, it usually
8834 also takes more than one machine instruction to destroy a stack frame;
8835 after you begin stepping through that group of instructions, local
8836 variable definitions may be gone.
8838 This may also happen when the compiler does significant optimizations.
8839 To be sure of always seeing accurate values, turn off all optimization
8842 @cindex ``No symbol "foo" in current context''
8843 Another possible effect of compiler optimizations is to optimize
8844 unused variables out of existence, or assign variables to registers (as
8845 opposed to memory addresses). Depending on the support for such cases
8846 offered by the debug info format used by the compiler, @value{GDBN}
8847 might not be able to display values for such local variables. If that
8848 happens, @value{GDBN} will print a message like this:
8851 No symbol "foo" in current context.
8854 To solve such problems, either recompile without optimizations, or use a
8855 different debug info format, if the compiler supports several such
8856 formats. @xref{Compilation}, for more information on choosing compiler
8857 options. @xref{C, ,C and C@t{++}}, for more information about debug
8858 info formats that are best suited to C@t{++} programs.
8860 If you ask to print an object whose contents are unknown to
8861 @value{GDBN}, e.g., because its data type is not completely specified
8862 by the debug information, @value{GDBN} will say @samp{<incomplete
8863 type>}. @xref{Symbols, incomplete type}, for more about this.
8865 If you append @kbd{@@entry} string to a function parameter name you get its
8866 value at the time the function got called. If the value is not available an
8867 error message is printed. Entry values are available only with some compilers.
8868 Entry values are normally also printed at the function parameter list according
8869 to @ref{set print entry-values}.
8872 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8878 (gdb) print i@@entry
8882 Strings are identified as arrays of @code{char} values without specified
8883 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8884 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8885 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8886 defines literal string type @code{"char"} as @code{char} without a sign.
8891 signed char var1[] = "A";
8894 You get during debugging
8899 $2 = @{65 'A', 0 '\0'@}
8903 @section Artificial Arrays
8905 @cindex artificial array
8907 @kindex @@@r{, referencing memory as an array}
8908 It is often useful to print out several successive objects of the
8909 same type in memory; a section of an array, or an array of
8910 dynamically determined size for which only a pointer exists in the
8913 You can do this by referring to a contiguous span of memory as an
8914 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8915 operand of @samp{@@} should be the first element of the desired array
8916 and be an individual object. The right operand should be the desired length
8917 of the array. The result is an array value whose elements are all of
8918 the type of the left argument. The first element is actually the left
8919 argument; the second element comes from bytes of memory immediately
8920 following those that hold the first element, and so on. Here is an
8921 example. If a program says
8924 int *array = (int *) malloc (len * sizeof (int));
8928 you can print the contents of @code{array} with
8934 The left operand of @samp{@@} must reside in memory. Array values made
8935 with @samp{@@} in this way behave just like other arrays in terms of
8936 subscripting, and are coerced to pointers when used in expressions.
8937 Artificial arrays most often appear in expressions via the value history
8938 (@pxref{Value History, ,Value History}), after printing one out.
8940 Another way to create an artificial array is to use a cast.
8941 This re-interprets a value as if it were an array.
8942 The value need not be in memory:
8944 (@value{GDBP}) p/x (short[2])0x12345678
8945 $1 = @{0x1234, 0x5678@}
8948 As a convenience, if you leave the array length out (as in
8949 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8950 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8952 (@value{GDBP}) p/x (short[])0x12345678
8953 $2 = @{0x1234, 0x5678@}
8956 Sometimes the artificial array mechanism is not quite enough; in
8957 moderately complex data structures, the elements of interest may not
8958 actually be adjacent---for example, if you are interested in the values
8959 of pointers in an array. One useful work-around in this situation is
8960 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8961 Variables}) as a counter in an expression that prints the first
8962 interesting value, and then repeat that expression via @key{RET}. For
8963 instance, suppose you have an array @code{dtab} of pointers to
8964 structures, and you are interested in the values of a field @code{fv}
8965 in each structure. Here is an example of what you might type:
8975 @node Output Formats
8976 @section Output Formats
8978 @cindex formatted output
8979 @cindex output formats
8980 By default, @value{GDBN} prints a value according to its data type. Sometimes
8981 this is not what you want. For example, you might want to print a number
8982 in hex, or a pointer in decimal. Or you might want to view data in memory
8983 at a certain address as a character string or as an instruction. To do
8984 these things, specify an @dfn{output format} when you print a value.
8986 The simplest use of output formats is to say how to print a value
8987 already computed. This is done by starting the arguments of the
8988 @code{print} command with a slash and a format letter. The format
8989 letters supported are:
8993 Regard the bits of the value as an integer, and print the integer in
8997 Print as integer in signed decimal.
9000 Print as integer in unsigned decimal.
9003 Print as integer in octal.
9006 Print as integer in binary. The letter @samp{t} stands for ``two''.
9007 @footnote{@samp{b} cannot be used because these format letters are also
9008 used with the @code{x} command, where @samp{b} stands for ``byte'';
9009 see @ref{Memory,,Examining Memory}.}
9012 @cindex unknown address, locating
9013 @cindex locate address
9014 Print as an address, both absolute in hexadecimal and as an offset from
9015 the nearest preceding symbol. You can use this format used to discover
9016 where (in what function) an unknown address is located:
9019 (@value{GDBP}) p/a 0x54320
9020 $3 = 0x54320 <_initialize_vx+396>
9024 The command @code{info symbol 0x54320} yields similar results.
9025 @xref{Symbols, info symbol}.
9028 Regard as an integer and print it as a character constant. This
9029 prints both the numerical value and its character representation. The
9030 character representation is replaced with the octal escape @samp{\nnn}
9031 for characters outside the 7-bit @sc{ascii} range.
9033 Without this format, @value{GDBN} displays @code{char},
9034 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9035 constants. Single-byte members of vectors are displayed as integer
9039 Regard the bits of the value as a floating point number and print
9040 using typical floating point syntax.
9043 @cindex printing strings
9044 @cindex printing byte arrays
9045 Regard as a string, if possible. With this format, pointers to single-byte
9046 data are displayed as null-terminated strings and arrays of single-byte data
9047 are displayed as fixed-length strings. Other values are displayed in their
9050 Without this format, @value{GDBN} displays pointers to and arrays of
9051 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9052 strings. Single-byte members of a vector are displayed as an integer
9056 Like @samp{x} formatting, the value is treated as an integer and
9057 printed as hexadecimal, but leading zeros are printed to pad the value
9058 to the size of the integer type.
9061 @cindex raw printing
9062 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9063 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9064 Printing}). This typically results in a higher-level display of the
9065 value's contents. The @samp{r} format bypasses any Python
9066 pretty-printer which might exist.
9069 For example, to print the program counter in hex (@pxref{Registers}), type
9076 Note that no space is required before the slash; this is because command
9077 names in @value{GDBN} cannot contain a slash.
9079 To reprint the last value in the value history with a different format,
9080 you can use the @code{print} command with just a format and no
9081 expression. For example, @samp{p/x} reprints the last value in hex.
9084 @section Examining Memory
9086 You can use the command @code{x} (for ``examine'') to examine memory in
9087 any of several formats, independently of your program's data types.
9089 @cindex examining memory
9091 @kindex x @r{(examine memory)}
9092 @item x/@var{nfu} @var{addr}
9095 Use the @code{x} command to examine memory.
9098 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9099 much memory to display and how to format it; @var{addr} is an
9100 expression giving the address where you want to start displaying memory.
9101 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9102 Several commands set convenient defaults for @var{addr}.
9105 @item @var{n}, the repeat count
9106 The repeat count is a decimal integer; the default is 1. It specifies
9107 how much memory (counting by units @var{u}) to display.
9108 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9111 @item @var{f}, the display format
9112 The display format is one of the formats used by @code{print}
9113 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9114 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9115 The default is @samp{x} (hexadecimal) initially. The default changes
9116 each time you use either @code{x} or @code{print}.
9118 @item @var{u}, the unit size
9119 The unit size is any of
9125 Halfwords (two bytes).
9127 Words (four bytes). This is the initial default.
9129 Giant words (eight bytes).
9132 Each time you specify a unit size with @code{x}, that size becomes the
9133 default unit the next time you use @code{x}. For the @samp{i} format,
9134 the unit size is ignored and is normally not written. For the @samp{s} format,
9135 the unit size defaults to @samp{b}, unless it is explicitly given.
9136 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9137 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9138 Note that the results depend on the programming language of the
9139 current compilation unit. If the language is C, the @samp{s}
9140 modifier will use the UTF-16 encoding while @samp{w} will use
9141 UTF-32. The encoding is set by the programming language and cannot
9144 @item @var{addr}, starting display address
9145 @var{addr} is the address where you want @value{GDBN} to begin displaying
9146 memory. The expression need not have a pointer value (though it may);
9147 it is always interpreted as an integer address of a byte of memory.
9148 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9149 @var{addr} is usually just after the last address examined---but several
9150 other commands also set the default address: @code{info breakpoints} (to
9151 the address of the last breakpoint listed), @code{info line} (to the
9152 starting address of a line), and @code{print} (if you use it to display
9153 a value from memory).
9156 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9157 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9158 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9159 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9160 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9162 Since the letters indicating unit sizes are all distinct from the
9163 letters specifying output formats, you do not have to remember whether
9164 unit size or format comes first; either order works. The output
9165 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9166 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9168 Even though the unit size @var{u} is ignored for the formats @samp{s}
9169 and @samp{i}, you might still want to use a count @var{n}; for example,
9170 @samp{3i} specifies that you want to see three machine instructions,
9171 including any operands. For convenience, especially when used with
9172 the @code{display} command, the @samp{i} format also prints branch delay
9173 slot instructions, if any, beyond the count specified, which immediately
9174 follow the last instruction that is within the count. The command
9175 @code{disassemble} gives an alternative way of inspecting machine
9176 instructions; see @ref{Machine Code,,Source and Machine Code}.
9178 All the defaults for the arguments to @code{x} are designed to make it
9179 easy to continue scanning memory with minimal specifications each time
9180 you use @code{x}. For example, after you have inspected three machine
9181 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9182 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9183 the repeat count @var{n} is used again; the other arguments default as
9184 for successive uses of @code{x}.
9186 When examining machine instructions, the instruction at current program
9187 counter is shown with a @code{=>} marker. For example:
9190 (@value{GDBP}) x/5i $pc-6
9191 0x804837f <main+11>: mov %esp,%ebp
9192 0x8048381 <main+13>: push %ecx
9193 0x8048382 <main+14>: sub $0x4,%esp
9194 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9195 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9198 @cindex @code{$_}, @code{$__}, and value history
9199 The addresses and contents printed by the @code{x} command are not saved
9200 in the value history because there is often too much of them and they
9201 would get in the way. Instead, @value{GDBN} makes these values available for
9202 subsequent use in expressions as values of the convenience variables
9203 @code{$_} and @code{$__}. After an @code{x} command, the last address
9204 examined is available for use in expressions in the convenience variable
9205 @code{$_}. The contents of that address, as examined, are available in
9206 the convenience variable @code{$__}.
9208 If the @code{x} command has a repeat count, the address and contents saved
9209 are from the last memory unit printed; this is not the same as the last
9210 address printed if several units were printed on the last line of output.
9212 @anchor{addressable memory unit}
9213 @cindex addressable memory unit
9214 Most targets have an addressable memory unit size of 8 bits. This means
9215 that to each memory address are associated 8 bits of data. Some
9216 targets, however, have other addressable memory unit sizes.
9217 Within @value{GDBN} and this document, the term
9218 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9219 when explicitly referring to a chunk of data of that size. The word
9220 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9221 the addressable memory unit size of the target. For most systems,
9222 addressable memory unit is a synonym of byte.
9224 @cindex remote memory comparison
9225 @cindex target memory comparison
9226 @cindex verify remote memory image
9227 @cindex verify target memory image
9228 When you are debugging a program running on a remote target machine
9229 (@pxref{Remote Debugging}), you may wish to verify the program's image
9230 in the remote machine's memory against the executable file you
9231 downloaded to the target. Or, on any target, you may want to check
9232 whether the program has corrupted its own read-only sections. The
9233 @code{compare-sections} command is provided for such situations.
9236 @kindex compare-sections
9237 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9238 Compare the data of a loadable section @var{section-name} in the
9239 executable file of the program being debugged with the same section in
9240 the target machine's memory, and report any mismatches. With no
9241 arguments, compares all loadable sections. With an argument of
9242 @code{-r}, compares all loadable read-only sections.
9244 Note: for remote targets, this command can be accelerated if the
9245 target supports computing the CRC checksum of a block of memory
9246 (@pxref{qCRC packet}).
9250 @section Automatic Display
9251 @cindex automatic display
9252 @cindex display of expressions
9254 If you find that you want to print the value of an expression frequently
9255 (to see how it changes), you might want to add it to the @dfn{automatic
9256 display list} so that @value{GDBN} prints its value each time your program stops.
9257 Each expression added to the list is given a number to identify it;
9258 to remove an expression from the list, you specify that number.
9259 The automatic display looks like this:
9263 3: bar[5] = (struct hack *) 0x3804
9267 This display shows item numbers, expressions and their current values. As with
9268 displays you request manually using @code{x} or @code{print}, you can
9269 specify the output format you prefer; in fact, @code{display} decides
9270 whether to use @code{print} or @code{x} depending your format
9271 specification---it uses @code{x} if you specify either the @samp{i}
9272 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9276 @item display @var{expr}
9277 Add the expression @var{expr} to the list of expressions to display
9278 each time your program stops. @xref{Expressions, ,Expressions}.
9280 @code{display} does not repeat if you press @key{RET} again after using it.
9282 @item display/@var{fmt} @var{expr}
9283 For @var{fmt} specifying only a display format and not a size or
9284 count, add the expression @var{expr} to the auto-display list but
9285 arrange to display it each time in the specified format @var{fmt}.
9286 @xref{Output Formats,,Output Formats}.
9288 @item display/@var{fmt} @var{addr}
9289 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9290 number of units, add the expression @var{addr} as a memory address to
9291 be examined each time your program stops. Examining means in effect
9292 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9295 For example, @samp{display/i $pc} can be helpful, to see the machine
9296 instruction about to be executed each time execution stops (@samp{$pc}
9297 is a common name for the program counter; @pxref{Registers, ,Registers}).
9300 @kindex delete display
9302 @item undisplay @var{dnums}@dots{}
9303 @itemx delete display @var{dnums}@dots{}
9304 Remove items from the list of expressions to display. Specify the
9305 numbers of the displays that you want affected with the command
9306 argument @var{dnums}. It can be a single display number, one of the
9307 numbers shown in the first field of the @samp{info display} display;
9308 or it could be a range of display numbers, as in @code{2-4}.
9310 @code{undisplay} does not repeat if you press @key{RET} after using it.
9311 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9313 @kindex disable display
9314 @item disable display @var{dnums}@dots{}
9315 Disable the display of item numbers @var{dnums}. A disabled display
9316 item is not printed automatically, but is not forgotten. It may be
9317 enabled again later. Specify the numbers of the displays that you
9318 want affected with the command argument @var{dnums}. It can be a
9319 single display number, one of the numbers shown in the first field of
9320 the @samp{info display} display; or it could be a range of display
9321 numbers, as in @code{2-4}.
9323 @kindex enable display
9324 @item enable display @var{dnums}@dots{}
9325 Enable display of item numbers @var{dnums}. It becomes effective once
9326 again in auto display of its expression, until you specify otherwise.
9327 Specify the numbers of the displays that you want affected with the
9328 command argument @var{dnums}. It can be a single display number, one
9329 of the numbers shown in the first field of the @samp{info display}
9330 display; or it could be a range of display numbers, as in @code{2-4}.
9333 Display the current values of the expressions on the list, just as is
9334 done when your program stops.
9336 @kindex info display
9338 Print the list of expressions previously set up to display
9339 automatically, each one with its item number, but without showing the
9340 values. This includes disabled expressions, which are marked as such.
9341 It also includes expressions which would not be displayed right now
9342 because they refer to automatic variables not currently available.
9345 @cindex display disabled out of scope
9346 If a display expression refers to local variables, then it does not make
9347 sense outside the lexical context for which it was set up. Such an
9348 expression is disabled when execution enters a context where one of its
9349 variables is not defined. For example, if you give the command
9350 @code{display last_char} while inside a function with an argument
9351 @code{last_char}, @value{GDBN} displays this argument while your program
9352 continues to stop inside that function. When it stops elsewhere---where
9353 there is no variable @code{last_char}---the display is disabled
9354 automatically. The next time your program stops where @code{last_char}
9355 is meaningful, you can enable the display expression once again.
9357 @node Print Settings
9358 @section Print Settings
9360 @cindex format options
9361 @cindex print settings
9362 @value{GDBN} provides the following ways to control how arrays, structures,
9363 and symbols are printed.
9366 These settings are useful for debugging programs in any language:
9370 @item set print address
9371 @itemx set print address on
9372 @cindex print/don't print memory addresses
9373 @value{GDBN} prints memory addresses showing the location of stack
9374 traces, structure values, pointer values, breakpoints, and so forth,
9375 even when it also displays the contents of those addresses. The default
9376 is @code{on}. For example, this is what a stack frame display looks like with
9377 @code{set print address on}:
9382 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9384 530 if (lquote != def_lquote)
9388 @item set print address off
9389 Do not print addresses when displaying their contents. For example,
9390 this is the same stack frame displayed with @code{set print address off}:
9394 (@value{GDBP}) set print addr off
9396 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9397 530 if (lquote != def_lquote)
9401 You can use @samp{set print address off} to eliminate all machine
9402 dependent displays from the @value{GDBN} interface. For example, with
9403 @code{print address off}, you should get the same text for backtraces on
9404 all machines---whether or not they involve pointer arguments.
9407 @item show print address
9408 Show whether or not addresses are to be printed.
9411 When @value{GDBN} prints a symbolic address, it normally prints the
9412 closest earlier symbol plus an offset. If that symbol does not uniquely
9413 identify the address (for example, it is a name whose scope is a single
9414 source file), you may need to clarify. One way to do this is with
9415 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9416 you can set @value{GDBN} to print the source file and line number when
9417 it prints a symbolic address:
9420 @item set print symbol-filename on
9421 @cindex source file and line of a symbol
9422 @cindex symbol, source file and line
9423 Tell @value{GDBN} to print the source file name and line number of a
9424 symbol in the symbolic form of an address.
9426 @item set print symbol-filename off
9427 Do not print source file name and line number of a symbol. This is the
9430 @item show print symbol-filename
9431 Show whether or not @value{GDBN} will print the source file name and
9432 line number of a symbol in the symbolic form of an address.
9435 Another situation where it is helpful to show symbol filenames and line
9436 numbers is when disassembling code; @value{GDBN} shows you the line
9437 number and source file that corresponds to each instruction.
9439 Also, you may wish to see the symbolic form only if the address being
9440 printed is reasonably close to the closest earlier symbol:
9443 @item set print max-symbolic-offset @var{max-offset}
9444 @itemx set print max-symbolic-offset unlimited
9445 @cindex maximum value for offset of closest symbol
9446 Tell @value{GDBN} to only display the symbolic form of an address if the
9447 offset between the closest earlier symbol and the address is less than
9448 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9449 to always print the symbolic form of an address if any symbol precedes
9450 it. Zero is equivalent to @code{unlimited}.
9452 @item show print max-symbolic-offset
9453 Ask how large the maximum offset is that @value{GDBN} prints in a
9457 @cindex wild pointer, interpreting
9458 @cindex pointer, finding referent
9459 If you have a pointer and you are not sure where it points, try
9460 @samp{set print symbol-filename on}. Then you can determine the name
9461 and source file location of the variable where it points, using
9462 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9463 For example, here @value{GDBN} shows that a variable @code{ptt} points
9464 at another variable @code{t}, defined in @file{hi2.c}:
9467 (@value{GDBP}) set print symbol-filename on
9468 (@value{GDBP}) p/a ptt
9469 $4 = 0xe008 <t in hi2.c>
9473 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9474 does not show the symbol name and filename of the referent, even with
9475 the appropriate @code{set print} options turned on.
9478 You can also enable @samp{/a}-like formatting all the time using
9479 @samp{set print symbol on}:
9482 @item set print symbol on
9483 Tell @value{GDBN} to print the symbol corresponding to an address, if
9486 @item set print symbol off
9487 Tell @value{GDBN} not to print the symbol corresponding to an
9488 address. In this mode, @value{GDBN} will still print the symbol
9489 corresponding to pointers to functions. This is the default.
9491 @item show print symbol
9492 Show whether @value{GDBN} will display the symbol corresponding to an
9496 Other settings control how different kinds of objects are printed:
9499 @item set print array
9500 @itemx set print array on
9501 @cindex pretty print arrays
9502 Pretty print arrays. This format is more convenient to read,
9503 but uses more space. The default is off.
9505 @item set print array off
9506 Return to compressed format for arrays.
9508 @item show print array
9509 Show whether compressed or pretty format is selected for displaying
9512 @cindex print array indexes
9513 @item set print array-indexes
9514 @itemx set print array-indexes on
9515 Print the index of each element when displaying arrays. May be more
9516 convenient to locate a given element in the array or quickly find the
9517 index of a given element in that printed array. The default is off.
9519 @item set print array-indexes off
9520 Stop printing element indexes when displaying arrays.
9522 @item show print array-indexes
9523 Show whether the index of each element is printed when displaying
9526 @item set print elements @var{number-of-elements}
9527 @itemx set print elements unlimited
9528 @cindex number of array elements to print
9529 @cindex limit on number of printed array elements
9530 Set a limit on how many elements of an array @value{GDBN} will print.
9531 If @value{GDBN} is printing a large array, it stops printing after it has
9532 printed the number of elements set by the @code{set print elements} command.
9533 This limit also applies to the display of strings.
9534 When @value{GDBN} starts, this limit is set to 200.
9535 Setting @var{number-of-elements} to @code{unlimited} or zero means
9536 that the number of elements to print is unlimited.
9538 @item show print elements
9539 Display the number of elements of a large array that @value{GDBN} will print.
9540 If the number is 0, then the printing is unlimited.
9542 @item set print frame-arguments @var{value}
9543 @kindex set print frame-arguments
9544 @cindex printing frame argument values
9545 @cindex print all frame argument values
9546 @cindex print frame argument values for scalars only
9547 @cindex do not print frame argument values
9548 This command allows to control how the values of arguments are printed
9549 when the debugger prints a frame (@pxref{Frames}). The possible
9554 The values of all arguments are printed.
9557 Print the value of an argument only if it is a scalar. The value of more
9558 complex arguments such as arrays, structures, unions, etc, is replaced
9559 by @code{@dots{}}. This is the default. Here is an example where
9560 only scalar arguments are shown:
9563 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9568 None of the argument values are printed. Instead, the value of each argument
9569 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9572 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9577 By default, only scalar arguments are printed. This command can be used
9578 to configure the debugger to print the value of all arguments, regardless
9579 of their type. However, it is often advantageous to not print the value
9580 of more complex parameters. For instance, it reduces the amount of
9581 information printed in each frame, making the backtrace more readable.
9582 Also, it improves performance when displaying Ada frames, because
9583 the computation of large arguments can sometimes be CPU-intensive,
9584 especially in large applications. Setting @code{print frame-arguments}
9585 to @code{scalars} (the default) or @code{none} avoids this computation,
9586 thus speeding up the display of each Ada frame.
9588 @item show print frame-arguments
9589 Show how the value of arguments should be displayed when printing a frame.
9591 @item set print raw frame-arguments on
9592 Print frame arguments in raw, non pretty-printed, form.
9594 @item set print raw frame-arguments off
9595 Print frame arguments in pretty-printed form, if there is a pretty-printer
9596 for the value (@pxref{Pretty Printing}),
9597 otherwise print the value in raw form.
9598 This is the default.
9600 @item show print raw frame-arguments
9601 Show whether to print frame arguments in raw form.
9603 @anchor{set print entry-values}
9604 @item set print entry-values @var{value}
9605 @kindex set print entry-values
9606 Set printing of frame argument values at function entry. In some cases
9607 @value{GDBN} can determine the value of function argument which was passed by
9608 the function caller, even if the value was modified inside the called function
9609 and therefore is different. With optimized code, the current value could be
9610 unavailable, but the entry value may still be known.
9612 The default value is @code{default} (see below for its description). Older
9613 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9614 this feature will behave in the @code{default} setting the same way as with the
9617 This functionality is currently supported only by DWARF 2 debugging format and
9618 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9619 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9622 The @var{value} parameter can be one of the following:
9626 Print only actual parameter values, never print values from function entry
9630 #0 different (val=6)
9631 #0 lost (val=<optimized out>)
9633 #0 invalid (val=<optimized out>)
9637 Print only parameter values from function entry point. The actual parameter
9638 values are never printed.
9640 #0 equal (val@@entry=5)
9641 #0 different (val@@entry=5)
9642 #0 lost (val@@entry=5)
9643 #0 born (val@@entry=<optimized out>)
9644 #0 invalid (val@@entry=<optimized out>)
9648 Print only parameter values from function entry point. If value from function
9649 entry point is not known while the actual value is known, print the actual
9650 value for such parameter.
9652 #0 equal (val@@entry=5)
9653 #0 different (val@@entry=5)
9654 #0 lost (val@@entry=5)
9656 #0 invalid (val@@entry=<optimized out>)
9660 Print actual parameter values. If actual parameter value is not known while
9661 value from function entry point is known, print the entry point value for such
9665 #0 different (val=6)
9666 #0 lost (val@@entry=5)
9668 #0 invalid (val=<optimized out>)
9672 Always print both the actual parameter value and its value from function entry
9673 point, even if values of one or both are not available due to compiler
9676 #0 equal (val=5, val@@entry=5)
9677 #0 different (val=6, val@@entry=5)
9678 #0 lost (val=<optimized out>, val@@entry=5)
9679 #0 born (val=10, val@@entry=<optimized out>)
9680 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9684 Print the actual parameter value if it is known and also its value from
9685 function entry point if it is known. If neither is known, print for the actual
9686 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9687 values are known and identical, print the shortened
9688 @code{param=param@@entry=VALUE} notation.
9690 #0 equal (val=val@@entry=5)
9691 #0 different (val=6, val@@entry=5)
9692 #0 lost (val@@entry=5)
9694 #0 invalid (val=<optimized out>)
9698 Always print the actual parameter value. Print also its value from function
9699 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9700 if both values are known and identical, print the shortened
9701 @code{param=param@@entry=VALUE} notation.
9703 #0 equal (val=val@@entry=5)
9704 #0 different (val=6, val@@entry=5)
9705 #0 lost (val=<optimized out>, val@@entry=5)
9707 #0 invalid (val=<optimized out>)
9711 For analysis messages on possible failures of frame argument values at function
9712 entry resolution see @ref{set debug entry-values}.
9714 @item show print entry-values
9715 Show the method being used for printing of frame argument values at function
9718 @item set print repeats @var{number-of-repeats}
9719 @itemx set print repeats unlimited
9720 @cindex repeated array elements
9721 Set the threshold for suppressing display of repeated array
9722 elements. When the number of consecutive identical elements of an
9723 array exceeds the threshold, @value{GDBN} prints the string
9724 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9725 identical repetitions, instead of displaying the identical elements
9726 themselves. Setting the threshold to @code{unlimited} or zero will
9727 cause all elements to be individually printed. The default threshold
9730 @item show print repeats
9731 Display the current threshold for printing repeated identical
9734 @item set print null-stop
9735 @cindex @sc{null} elements in arrays
9736 Cause @value{GDBN} to stop printing the characters of an array when the first
9737 @sc{null} is encountered. This is useful when large arrays actually
9738 contain only short strings.
9741 @item show print null-stop
9742 Show whether @value{GDBN} stops printing an array on the first
9743 @sc{null} character.
9745 @item set print pretty on
9746 @cindex print structures in indented form
9747 @cindex indentation in structure display
9748 Cause @value{GDBN} to print structures in an indented format with one member
9749 per line, like this:
9764 @item set print pretty off
9765 Cause @value{GDBN} to print structures in a compact format, like this:
9769 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9770 meat = 0x54 "Pork"@}
9775 This is the default format.
9777 @item show print pretty
9778 Show which format @value{GDBN} is using to print structures.
9780 @item set print sevenbit-strings on
9781 @cindex eight-bit characters in strings
9782 @cindex octal escapes in strings
9783 Print using only seven-bit characters; if this option is set,
9784 @value{GDBN} displays any eight-bit characters (in strings or
9785 character values) using the notation @code{\}@var{nnn}. This setting is
9786 best if you are working in English (@sc{ascii}) and you use the
9787 high-order bit of characters as a marker or ``meta'' bit.
9789 @item set print sevenbit-strings off
9790 Print full eight-bit characters. This allows the use of more
9791 international character sets, and is the default.
9793 @item show print sevenbit-strings
9794 Show whether or not @value{GDBN} is printing only seven-bit characters.
9796 @item set print union on
9797 @cindex unions in structures, printing
9798 Tell @value{GDBN} to print unions which are contained in structures
9799 and other unions. This is the default setting.
9801 @item set print union off
9802 Tell @value{GDBN} not to print unions which are contained in
9803 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9806 @item show print union
9807 Ask @value{GDBN} whether or not it will print unions which are contained in
9808 structures and other unions.
9810 For example, given the declarations
9813 typedef enum @{Tree, Bug@} Species;
9814 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9815 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9826 struct thing foo = @{Tree, @{Acorn@}@};
9830 with @code{set print union on} in effect @samp{p foo} would print
9833 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9837 and with @code{set print union off} in effect it would print
9840 $1 = @{it = Tree, form = @{...@}@}
9844 @code{set print union} affects programs written in C-like languages
9850 These settings are of interest when debugging C@t{++} programs:
9853 @cindex demangling C@t{++} names
9854 @item set print demangle
9855 @itemx set print demangle on
9856 Print C@t{++} names in their source form rather than in the encoded
9857 (``mangled'') form passed to the assembler and linker for type-safe
9858 linkage. The default is on.
9860 @item show print demangle
9861 Show whether C@t{++} names are printed in mangled or demangled form.
9863 @item set print asm-demangle
9864 @itemx set print asm-demangle on
9865 Print C@t{++} names in their source form rather than their mangled form, even
9866 in assembler code printouts such as instruction disassemblies.
9869 @item show print asm-demangle
9870 Show whether C@t{++} names in assembly listings are printed in mangled
9873 @cindex C@t{++} symbol decoding style
9874 @cindex symbol decoding style, C@t{++}
9875 @kindex set demangle-style
9876 @item set demangle-style @var{style}
9877 Choose among several encoding schemes used by different compilers to
9878 represent C@t{++} names. The choices for @var{style} are currently:
9882 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9883 This is the default.
9886 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9889 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9892 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9895 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9896 @strong{Warning:} this setting alone is not sufficient to allow
9897 debugging @code{cfront}-generated executables. @value{GDBN} would
9898 require further enhancement to permit that.
9901 If you omit @var{style}, you will see a list of possible formats.
9903 @item show demangle-style
9904 Display the encoding style currently in use for decoding C@t{++} symbols.
9906 @item set print object
9907 @itemx set print object on
9908 @cindex derived type of an object, printing
9909 @cindex display derived types
9910 When displaying a pointer to an object, identify the @emph{actual}
9911 (derived) type of the object rather than the @emph{declared} type, using
9912 the virtual function table. Note that the virtual function table is
9913 required---this feature can only work for objects that have run-time
9914 type identification; a single virtual method in the object's declared
9915 type is sufficient. Note that this setting is also taken into account when
9916 working with variable objects via MI (@pxref{GDB/MI}).
9918 @item set print object off
9919 Display only the declared type of objects, without reference to the
9920 virtual function table. This is the default setting.
9922 @item show print object
9923 Show whether actual, or declared, object types are displayed.
9925 @item set print static-members
9926 @itemx set print static-members on
9927 @cindex static members of C@t{++} objects
9928 Print static members when displaying a C@t{++} object. The default is on.
9930 @item set print static-members off
9931 Do not print static members when displaying a C@t{++} object.
9933 @item show print static-members
9934 Show whether C@t{++} static members are printed or not.
9936 @item set print pascal_static-members
9937 @itemx set print pascal_static-members on
9938 @cindex static members of Pascal objects
9939 @cindex Pascal objects, static members display
9940 Print static members when displaying a Pascal object. The default is on.
9942 @item set print pascal_static-members off
9943 Do not print static members when displaying a Pascal object.
9945 @item show print pascal_static-members
9946 Show whether Pascal static members are printed or not.
9948 @c These don't work with HP ANSI C++ yet.
9949 @item set print vtbl
9950 @itemx set print vtbl on
9951 @cindex pretty print C@t{++} virtual function tables
9952 @cindex virtual functions (C@t{++}) display
9953 @cindex VTBL display
9954 Pretty print C@t{++} virtual function tables. The default is off.
9955 (The @code{vtbl} commands do not work on programs compiled with the HP
9956 ANSI C@t{++} compiler (@code{aCC}).)
9958 @item set print vtbl off
9959 Do not pretty print C@t{++} virtual function tables.
9961 @item show print vtbl
9962 Show whether C@t{++} virtual function tables are pretty printed, or not.
9965 @node Pretty Printing
9966 @section Pretty Printing
9968 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9969 Python code. It greatly simplifies the display of complex objects. This
9970 mechanism works for both MI and the CLI.
9973 * Pretty-Printer Introduction:: Introduction to pretty-printers
9974 * Pretty-Printer Example:: An example pretty-printer
9975 * Pretty-Printer Commands:: Pretty-printer commands
9978 @node Pretty-Printer Introduction
9979 @subsection Pretty-Printer Introduction
9981 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9982 registered for the value. If there is then @value{GDBN} invokes the
9983 pretty-printer to print the value. Otherwise the value is printed normally.
9985 Pretty-printers are normally named. This makes them easy to manage.
9986 The @samp{info pretty-printer} command will list all the installed
9987 pretty-printers with their names.
9988 If a pretty-printer can handle multiple data types, then its
9989 @dfn{subprinters} are the printers for the individual data types.
9990 Each such subprinter has its own name.
9991 The format of the name is @var{printer-name};@var{subprinter-name}.
9993 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9994 Typically they are automatically loaded and registered when the corresponding
9995 debug information is loaded, thus making them available without having to
9996 do anything special.
9998 There are three places where a pretty-printer can be registered.
10002 Pretty-printers registered globally are available when debugging
10006 Pretty-printers registered with a program space are available only
10007 when debugging that program.
10008 @xref{Progspaces In Python}, for more details on program spaces in Python.
10011 Pretty-printers registered with an objfile are loaded and unloaded
10012 with the corresponding objfile (e.g., shared library).
10013 @xref{Objfiles In Python}, for more details on objfiles in Python.
10016 @xref{Selecting Pretty-Printers}, for further information on how
10017 pretty-printers are selected,
10019 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10022 @node Pretty-Printer Example
10023 @subsection Pretty-Printer Example
10025 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10028 (@value{GDBP}) print s
10030 static npos = 4294967295,
10032 <std::allocator<char>> = @{
10033 <__gnu_cxx::new_allocator<char>> = @{
10034 <No data fields>@}, <No data fields>
10036 members of std::basic_string<char, std::char_traits<char>,
10037 std::allocator<char> >::_Alloc_hider:
10038 _M_p = 0x804a014 "abcd"
10043 With a pretty-printer for @code{std::string} only the contents are printed:
10046 (@value{GDBP}) print s
10050 @node Pretty-Printer Commands
10051 @subsection Pretty-Printer Commands
10052 @cindex pretty-printer commands
10055 @kindex info pretty-printer
10056 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10057 Print the list of installed pretty-printers.
10058 This includes disabled pretty-printers, which are marked as such.
10060 @var{object-regexp} is a regular expression matching the objects
10061 whose pretty-printers to list.
10062 Objects can be @code{global}, the program space's file
10063 (@pxref{Progspaces In Python}),
10064 and the object files within that program space (@pxref{Objfiles In Python}).
10065 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10066 looks up a printer from these three objects.
10068 @var{name-regexp} is a regular expression matching the name of the printers
10071 @kindex disable pretty-printer
10072 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10073 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10074 A disabled pretty-printer is not forgotten, it may be enabled again later.
10076 @kindex enable pretty-printer
10077 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10078 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10083 Suppose we have three pretty-printers installed: one from library1.so
10084 named @code{foo} that prints objects of type @code{foo}, and
10085 another from library2.so named @code{bar} that prints two types of objects,
10086 @code{bar1} and @code{bar2}.
10089 (gdb) info pretty-printer
10096 (gdb) info pretty-printer library2
10101 (gdb) disable pretty-printer library1
10103 2 of 3 printers enabled
10104 (gdb) info pretty-printer
10111 (gdb) disable pretty-printer library2 bar:bar1
10113 1 of 3 printers enabled
10114 (gdb) info pretty-printer library2
10121 (gdb) disable pretty-printer library2 bar
10123 0 of 3 printers enabled
10124 (gdb) info pretty-printer library2
10133 Note that for @code{bar} the entire printer can be disabled,
10134 as can each individual subprinter.
10136 @node Value History
10137 @section Value History
10139 @cindex value history
10140 @cindex history of values printed by @value{GDBN}
10141 Values printed by the @code{print} command are saved in the @value{GDBN}
10142 @dfn{value history}. This allows you to refer to them in other expressions.
10143 Values are kept until the symbol table is re-read or discarded
10144 (for example with the @code{file} or @code{symbol-file} commands).
10145 When the symbol table changes, the value history is discarded,
10146 since the values may contain pointers back to the types defined in the
10151 @cindex history number
10152 The values printed are given @dfn{history numbers} by which you can
10153 refer to them. These are successive integers starting with one.
10154 @code{print} shows you the history number assigned to a value by
10155 printing @samp{$@var{num} = } before the value; here @var{num} is the
10158 To refer to any previous value, use @samp{$} followed by the value's
10159 history number. The way @code{print} labels its output is designed to
10160 remind you of this. Just @code{$} refers to the most recent value in
10161 the history, and @code{$$} refers to the value before that.
10162 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10163 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10164 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10166 For example, suppose you have just printed a pointer to a structure and
10167 want to see the contents of the structure. It suffices to type
10173 If you have a chain of structures where the component @code{next} points
10174 to the next one, you can print the contents of the next one with this:
10181 You can print successive links in the chain by repeating this
10182 command---which you can do by just typing @key{RET}.
10184 Note that the history records values, not expressions. If the value of
10185 @code{x} is 4 and you type these commands:
10193 then the value recorded in the value history by the @code{print} command
10194 remains 4 even though the value of @code{x} has changed.
10197 @kindex show values
10199 Print the last ten values in the value history, with their item numbers.
10200 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10201 values} does not change the history.
10203 @item show values @var{n}
10204 Print ten history values centered on history item number @var{n}.
10206 @item show values +
10207 Print ten history values just after the values last printed. If no more
10208 values are available, @code{show values +} produces no display.
10211 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10212 same effect as @samp{show values +}.
10214 @node Convenience Vars
10215 @section Convenience Variables
10217 @cindex convenience variables
10218 @cindex user-defined variables
10219 @value{GDBN} provides @dfn{convenience variables} that you can use within
10220 @value{GDBN} to hold on to a value and refer to it later. These variables
10221 exist entirely within @value{GDBN}; they are not part of your program, and
10222 setting a convenience variable has no direct effect on further execution
10223 of your program. That is why you can use them freely.
10225 Convenience variables are prefixed with @samp{$}. Any name preceded by
10226 @samp{$} can be used for a convenience variable, unless it is one of
10227 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10228 (Value history references, in contrast, are @emph{numbers} preceded
10229 by @samp{$}. @xref{Value History, ,Value History}.)
10231 You can save a value in a convenience variable with an assignment
10232 expression, just as you would set a variable in your program.
10236 set $foo = *object_ptr
10240 would save in @code{$foo} the value contained in the object pointed to by
10243 Using a convenience variable for the first time creates it, but its
10244 value is @code{void} until you assign a new value. You can alter the
10245 value with another assignment at any time.
10247 Convenience variables have no fixed types. You can assign a convenience
10248 variable any type of value, including structures and arrays, even if
10249 that variable already has a value of a different type. The convenience
10250 variable, when used as an expression, has the type of its current value.
10253 @kindex show convenience
10254 @cindex show all user variables and functions
10255 @item show convenience
10256 Print a list of convenience variables used so far, and their values,
10257 as well as a list of the convenience functions.
10258 Abbreviated @code{show conv}.
10260 @kindex init-if-undefined
10261 @cindex convenience variables, initializing
10262 @item init-if-undefined $@var{variable} = @var{expression}
10263 Set a convenience variable if it has not already been set. This is useful
10264 for user-defined commands that keep some state. It is similar, in concept,
10265 to using local static variables with initializers in C (except that
10266 convenience variables are global). It can also be used to allow users to
10267 override default values used in a command script.
10269 If the variable is already defined then the expression is not evaluated so
10270 any side-effects do not occur.
10273 One of the ways to use a convenience variable is as a counter to be
10274 incremented or a pointer to be advanced. For example, to print
10275 a field from successive elements of an array of structures:
10279 print bar[$i++]->contents
10283 Repeat that command by typing @key{RET}.
10285 Some convenience variables are created automatically by @value{GDBN} and given
10286 values likely to be useful.
10289 @vindex $_@r{, convenience variable}
10291 The variable @code{$_} is automatically set by the @code{x} command to
10292 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10293 commands which provide a default address for @code{x} to examine also
10294 set @code{$_} to that address; these commands include @code{info line}
10295 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10296 except when set by the @code{x} command, in which case it is a pointer
10297 to the type of @code{$__}.
10299 @vindex $__@r{, convenience variable}
10301 The variable @code{$__} is automatically set by the @code{x} command
10302 to the value found in the last address examined. Its type is chosen
10303 to match the format in which the data was printed.
10306 @vindex $_exitcode@r{, convenience variable}
10307 When the program being debugged terminates normally, @value{GDBN}
10308 automatically sets this variable to the exit code of the program, and
10309 resets @code{$_exitsignal} to @code{void}.
10312 @vindex $_exitsignal@r{, convenience variable}
10313 When the program being debugged dies due to an uncaught signal,
10314 @value{GDBN} automatically sets this variable to that signal's number,
10315 and resets @code{$_exitcode} to @code{void}.
10317 To distinguish between whether the program being debugged has exited
10318 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10319 @code{$_exitsignal} is not @code{void}), the convenience function
10320 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10321 Functions}). For example, considering the following source code:
10324 #include <signal.h>
10327 main (int argc, char *argv[])
10334 A valid way of telling whether the program being debugged has exited
10335 or signalled would be:
10338 (@value{GDBP}) define has_exited_or_signalled
10339 Type commands for definition of ``has_exited_or_signalled''.
10340 End with a line saying just ``end''.
10341 >if $_isvoid ($_exitsignal)
10342 >echo The program has exited\n
10344 >echo The program has signalled\n
10350 Program terminated with signal SIGALRM, Alarm clock.
10351 The program no longer exists.
10352 (@value{GDBP}) has_exited_or_signalled
10353 The program has signalled
10356 As can be seen, @value{GDBN} correctly informs that the program being
10357 debugged has signalled, since it calls @code{raise} and raises a
10358 @code{SIGALRM} signal. If the program being debugged had not called
10359 @code{raise}, then @value{GDBN} would report a normal exit:
10362 (@value{GDBP}) has_exited_or_signalled
10363 The program has exited
10367 The variable @code{$_exception} is set to the exception object being
10368 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10371 @itemx $_probe_arg0@dots{}$_probe_arg11
10372 Arguments to a static probe. @xref{Static Probe Points}.
10375 @vindex $_sdata@r{, inspect, convenience variable}
10376 The variable @code{$_sdata} contains extra collected static tracepoint
10377 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10378 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10379 if extra static tracepoint data has not been collected.
10382 @vindex $_siginfo@r{, convenience variable}
10383 The variable @code{$_siginfo} contains extra signal information
10384 (@pxref{extra signal information}). Note that @code{$_siginfo}
10385 could be empty, if the application has not yet received any signals.
10386 For example, it will be empty before you execute the @code{run} command.
10389 @vindex $_tlb@r{, convenience variable}
10390 The variable @code{$_tlb} is automatically set when debugging
10391 applications running on MS-Windows in native mode or connected to
10392 gdbserver that supports the @code{qGetTIBAddr} request.
10393 @xref{General Query Packets}.
10394 This variable contains the address of the thread information block.
10398 On HP-UX systems, if you refer to a function or variable name that
10399 begins with a dollar sign, @value{GDBN} searches for a user or system
10400 name first, before it searches for a convenience variable.
10402 @node Convenience Funs
10403 @section Convenience Functions
10405 @cindex convenience functions
10406 @value{GDBN} also supplies some @dfn{convenience functions}. These
10407 have a syntax similar to convenience variables. A convenience
10408 function can be used in an expression just like an ordinary function;
10409 however, a convenience function is implemented internally to
10412 These functions do not require @value{GDBN} to be configured with
10413 @code{Python} support, which means that they are always available.
10417 @item $_isvoid (@var{expr})
10418 @findex $_isvoid@r{, convenience function}
10419 Return one if the expression @var{expr} is @code{void}. Otherwise it
10422 A @code{void} expression is an expression where the type of the result
10423 is @code{void}. For example, you can examine a convenience variable
10424 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10428 (@value{GDBP}) print $_exitcode
10430 (@value{GDBP}) print $_isvoid ($_exitcode)
10433 Starting program: ./a.out
10434 [Inferior 1 (process 29572) exited normally]
10435 (@value{GDBP}) print $_exitcode
10437 (@value{GDBP}) print $_isvoid ($_exitcode)
10441 In the example above, we used @code{$_isvoid} to check whether
10442 @code{$_exitcode} is @code{void} before and after the execution of the
10443 program being debugged. Before the execution there is no exit code to
10444 be examined, therefore @code{$_exitcode} is @code{void}. After the
10445 execution the program being debugged returned zero, therefore
10446 @code{$_exitcode} is zero, which means that it is not @code{void}
10449 The @code{void} expression can also be a call of a function from the
10450 program being debugged. For example, given the following function:
10459 The result of calling it inside @value{GDBN} is @code{void}:
10462 (@value{GDBP}) print foo ()
10464 (@value{GDBP}) print $_isvoid (foo ())
10466 (@value{GDBP}) set $v = foo ()
10467 (@value{GDBP}) print $v
10469 (@value{GDBP}) print $_isvoid ($v)
10475 These functions require @value{GDBN} to be configured with
10476 @code{Python} support.
10480 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10481 @findex $_memeq@r{, convenience function}
10482 Returns one if the @var{length} bytes at the addresses given by
10483 @var{buf1} and @var{buf2} are equal.
10484 Otherwise it returns zero.
10486 @item $_regex(@var{str}, @var{regex})
10487 @findex $_regex@r{, convenience function}
10488 Returns one if the string @var{str} matches the regular expression
10489 @var{regex}. Otherwise it returns zero.
10490 The syntax of the regular expression is that specified by @code{Python}'s
10491 regular expression support.
10493 @item $_streq(@var{str1}, @var{str2})
10494 @findex $_streq@r{, convenience function}
10495 Returns one if the strings @var{str1} and @var{str2} are equal.
10496 Otherwise it returns zero.
10498 @item $_strlen(@var{str})
10499 @findex $_strlen@r{, convenience function}
10500 Returns the length of string @var{str}.
10502 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10503 @findex $_caller_is@r{, convenience function}
10504 Returns one if the calling function's name is equal to @var{name}.
10505 Otherwise it returns zero.
10507 If the optional argument @var{number_of_frames} is provided,
10508 it is the number of frames up in the stack to look.
10516 at testsuite/gdb.python/py-caller-is.c:21
10517 #1 0x00000000004005a0 in middle_func ()
10518 at testsuite/gdb.python/py-caller-is.c:27
10519 #2 0x00000000004005ab in top_func ()
10520 at testsuite/gdb.python/py-caller-is.c:33
10521 #3 0x00000000004005b6 in main ()
10522 at testsuite/gdb.python/py-caller-is.c:39
10523 (gdb) print $_caller_is ("middle_func")
10525 (gdb) print $_caller_is ("top_func", 2)
10529 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10530 @findex $_caller_matches@r{, convenience function}
10531 Returns one if the calling function's name matches the regular expression
10532 @var{regexp}. Otherwise it returns zero.
10534 If the optional argument @var{number_of_frames} is provided,
10535 it is the number of frames up in the stack to look.
10538 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10539 @findex $_any_caller_is@r{, convenience function}
10540 Returns one if any calling function's name is equal to @var{name}.
10541 Otherwise it returns zero.
10543 If the optional argument @var{number_of_frames} is provided,
10544 it is the number of frames up in the stack to look.
10547 This function differs from @code{$_caller_is} in that this function
10548 checks all stack frames from the immediate caller to the frame specified
10549 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10550 frame specified by @var{number_of_frames}.
10552 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10553 @findex $_any_caller_matches@r{, convenience function}
10554 Returns one if any calling function's name matches the regular expression
10555 @var{regexp}. Otherwise it returns zero.
10557 If the optional argument @var{number_of_frames} is provided,
10558 it is the number of frames up in the stack to look.
10561 This function differs from @code{$_caller_matches} in that this function
10562 checks all stack frames from the immediate caller to the frame specified
10563 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10564 frame specified by @var{number_of_frames}.
10568 @value{GDBN} provides the ability to list and get help on
10569 convenience functions.
10572 @item help function
10573 @kindex help function
10574 @cindex show all convenience functions
10575 Print a list of all convenience functions.
10582 You can refer to machine register contents, in expressions, as variables
10583 with names starting with @samp{$}. The names of registers are different
10584 for each machine; use @code{info registers} to see the names used on
10588 @kindex info registers
10589 @item info registers
10590 Print the names and values of all registers except floating-point
10591 and vector registers (in the selected stack frame).
10593 @kindex info all-registers
10594 @cindex floating point registers
10595 @item info all-registers
10596 Print the names and values of all registers, including floating-point
10597 and vector registers (in the selected stack frame).
10599 @item info registers @var{regname} @dots{}
10600 Print the @dfn{relativized} value of each specified register @var{regname}.
10601 As discussed in detail below, register values are normally relative to
10602 the selected stack frame. The @var{regname} may be any register name valid on
10603 the machine you are using, with or without the initial @samp{$}.
10606 @anchor{standard registers}
10607 @cindex stack pointer register
10608 @cindex program counter register
10609 @cindex process status register
10610 @cindex frame pointer register
10611 @cindex standard registers
10612 @value{GDBN} has four ``standard'' register names that are available (in
10613 expressions) on most machines---whenever they do not conflict with an
10614 architecture's canonical mnemonics for registers. The register names
10615 @code{$pc} and @code{$sp} are used for the program counter register and
10616 the stack pointer. @code{$fp} is used for a register that contains a
10617 pointer to the current stack frame, and @code{$ps} is used for a
10618 register that contains the processor status. For example,
10619 you could print the program counter in hex with
10626 or print the instruction to be executed next with
10633 or add four to the stack pointer@footnote{This is a way of removing
10634 one word from the stack, on machines where stacks grow downward in
10635 memory (most machines, nowadays). This assumes that the innermost
10636 stack frame is selected; setting @code{$sp} is not allowed when other
10637 stack frames are selected. To pop entire frames off the stack,
10638 regardless of machine architecture, use @code{return};
10639 see @ref{Returning, ,Returning from a Function}.} with
10645 Whenever possible, these four standard register names are available on
10646 your machine even though the machine has different canonical mnemonics,
10647 so long as there is no conflict. The @code{info registers} command
10648 shows the canonical names. For example, on the SPARC, @code{info
10649 registers} displays the processor status register as @code{$psr} but you
10650 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10651 is an alias for the @sc{eflags} register.
10653 @value{GDBN} always considers the contents of an ordinary register as an
10654 integer when the register is examined in this way. Some machines have
10655 special registers which can hold nothing but floating point; these
10656 registers are considered to have floating point values. There is no way
10657 to refer to the contents of an ordinary register as floating point value
10658 (although you can @emph{print} it as a floating point value with
10659 @samp{print/f $@var{regname}}).
10661 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10662 means that the data format in which the register contents are saved by
10663 the operating system is not the same one that your program normally
10664 sees. For example, the registers of the 68881 floating point
10665 coprocessor are always saved in ``extended'' (raw) format, but all C
10666 programs expect to work with ``double'' (virtual) format. In such
10667 cases, @value{GDBN} normally works with the virtual format only (the format
10668 that makes sense for your program), but the @code{info registers} command
10669 prints the data in both formats.
10671 @cindex SSE registers (x86)
10672 @cindex MMX registers (x86)
10673 Some machines have special registers whose contents can be interpreted
10674 in several different ways. For example, modern x86-based machines
10675 have SSE and MMX registers that can hold several values packed
10676 together in several different formats. @value{GDBN} refers to such
10677 registers in @code{struct} notation:
10680 (@value{GDBP}) print $xmm1
10682 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10683 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10684 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10685 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10686 v4_int32 = @{0, 20657912, 11, 13@},
10687 v2_int64 = @{88725056443645952, 55834574859@},
10688 uint128 = 0x0000000d0000000b013b36f800000000
10693 To set values of such registers, you need to tell @value{GDBN} which
10694 view of the register you wish to change, as if you were assigning
10695 value to a @code{struct} member:
10698 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10701 Normally, register values are relative to the selected stack frame
10702 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10703 value that the register would contain if all stack frames farther in
10704 were exited and their saved registers restored. In order to see the
10705 true contents of hardware registers, you must select the innermost
10706 frame (with @samp{frame 0}).
10708 @cindex caller-saved registers
10709 @cindex call-clobbered registers
10710 @cindex volatile registers
10711 @cindex <not saved> values
10712 Usually ABIs reserve some registers as not needed to be saved by the
10713 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10714 registers). It may therefore not be possible for @value{GDBN} to know
10715 the value a register had before the call (in other words, in the outer
10716 frame), if the register value has since been changed by the callee.
10717 @value{GDBN} tries to deduce where the inner frame saved
10718 (``callee-saved'') registers, from the debug info, unwind info, or the
10719 machine code generated by your compiler. If some register is not
10720 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10721 its own knowledge of the ABI, or because the debug/unwind info
10722 explicitly says the register's value is undefined), @value{GDBN}
10723 displays @w{@samp{<not saved>}} as the register's value. With targets
10724 that @value{GDBN} has no knowledge of the register saving convention,
10725 if a register was not saved by the callee, then its value and location
10726 in the outer frame are assumed to be the same of the inner frame.
10727 This is usually harmless, because if the register is call-clobbered,
10728 the caller either does not care what is in the register after the
10729 call, or has code to restore the value that it does care about. Note,
10730 however, that if you change such a register in the outer frame, you
10731 may also be affecting the inner frame. Also, the more ``outer'' the
10732 frame is you're looking at, the more likely a call-clobbered
10733 register's value is to be wrong, in the sense that it doesn't actually
10734 represent the value the register had just before the call.
10736 @node Floating Point Hardware
10737 @section Floating Point Hardware
10738 @cindex floating point
10740 Depending on the configuration, @value{GDBN} may be able to give
10741 you more information about the status of the floating point hardware.
10746 Display hardware-dependent information about the floating
10747 point unit. The exact contents and layout vary depending on the
10748 floating point chip. Currently, @samp{info float} is supported on
10749 the ARM and x86 machines.
10753 @section Vector Unit
10754 @cindex vector unit
10756 Depending on the configuration, @value{GDBN} may be able to give you
10757 more information about the status of the vector unit.
10760 @kindex info vector
10762 Display information about the vector unit. The exact contents and
10763 layout vary depending on the hardware.
10766 @node OS Information
10767 @section Operating System Auxiliary Information
10768 @cindex OS information
10770 @value{GDBN} provides interfaces to useful OS facilities that can help
10771 you debug your program.
10773 @cindex auxiliary vector
10774 @cindex vector, auxiliary
10775 Some operating systems supply an @dfn{auxiliary vector} to programs at
10776 startup. This is akin to the arguments and environment that you
10777 specify for a program, but contains a system-dependent variety of
10778 binary values that tell system libraries important details about the
10779 hardware, operating system, and process. Each value's purpose is
10780 identified by an integer tag; the meanings are well-known but system-specific.
10781 Depending on the configuration and operating system facilities,
10782 @value{GDBN} may be able to show you this information. For remote
10783 targets, this functionality may further depend on the remote stub's
10784 support of the @samp{qXfer:auxv:read} packet, see
10785 @ref{qXfer auxiliary vector read}.
10790 Display the auxiliary vector of the inferior, which can be either a
10791 live process or a core dump file. @value{GDBN} prints each tag value
10792 numerically, and also shows names and text descriptions for recognized
10793 tags. Some values in the vector are numbers, some bit masks, and some
10794 pointers to strings or other data. @value{GDBN} displays each value in the
10795 most appropriate form for a recognized tag, and in hexadecimal for
10796 an unrecognized tag.
10799 On some targets, @value{GDBN} can access operating system-specific
10800 information and show it to you. The types of information available
10801 will differ depending on the type of operating system running on the
10802 target. The mechanism used to fetch the data is described in
10803 @ref{Operating System Information}. For remote targets, this
10804 functionality depends on the remote stub's support of the
10805 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10809 @item info os @var{infotype}
10811 Display OS information of the requested type.
10813 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10815 @anchor{linux info os infotypes}
10817 @kindex info os cpus
10819 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
10820 the available fields from /proc/cpuinfo. For each supported architecture
10821 different fields are available. Two common entries are processor which gives
10822 CPU number and bogomips; a system constant that is calculated during
10823 kernel initialization.
10825 @kindex info os files
10827 Display the list of open file descriptors on the target. For each
10828 file descriptor, @value{GDBN} prints the identifier of the process
10829 owning the descriptor, the command of the owning process, the value
10830 of the descriptor, and the target of the descriptor.
10832 @kindex info os modules
10834 Display the list of all loaded kernel modules on the target. For each
10835 module, @value{GDBN} prints the module name, the size of the module in
10836 bytes, the number of times the module is used, the dependencies of the
10837 module, the status of the module, and the address of the loaded module
10840 @kindex info os msg
10842 Display the list of all System V message queues on the target. For each
10843 message queue, @value{GDBN} prints the message queue key, the message
10844 queue identifier, the access permissions, the current number of bytes
10845 on the queue, the current number of messages on the queue, the processes
10846 that last sent and received a message on the queue, the user and group
10847 of the owner and creator of the message queue, the times at which a
10848 message was last sent and received on the queue, and the time at which
10849 the message queue was last changed.
10851 @kindex info os processes
10853 Display the list of processes on the target. For each process,
10854 @value{GDBN} prints the process identifier, the name of the user, the
10855 command corresponding to the process, and the list of processor cores
10856 that the process is currently running on. (To understand what these
10857 properties mean, for this and the following info types, please consult
10858 the general @sc{gnu}/Linux documentation.)
10860 @kindex info os procgroups
10862 Display the list of process groups on the target. For each process,
10863 @value{GDBN} prints the identifier of the process group that it belongs
10864 to, the command corresponding to the process group leader, the process
10865 identifier, and the command line of the process. The list is sorted
10866 first by the process group identifier, then by the process identifier,
10867 so that processes belonging to the same process group are grouped together
10868 and the process group leader is listed first.
10870 @kindex info os semaphores
10872 Display the list of all System V semaphore sets on the target. For each
10873 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10874 set identifier, the access permissions, the number of semaphores in the
10875 set, the user and group of the owner and creator of the semaphore set,
10876 and the times at which the semaphore set was operated upon and changed.
10878 @kindex info os shm
10880 Display the list of all System V shared-memory regions on the target.
10881 For each shared-memory region, @value{GDBN} prints the region key,
10882 the shared-memory identifier, the access permissions, the size of the
10883 region, the process that created the region, the process that last
10884 attached to or detached from the region, the current number of live
10885 attaches to the region, and the times at which the region was last
10886 attached to, detach from, and changed.
10888 @kindex info os sockets
10890 Display the list of Internet-domain sockets on the target. For each
10891 socket, @value{GDBN} prints the address and port of the local and
10892 remote endpoints, the current state of the connection, the creator of
10893 the socket, the IP address family of the socket, and the type of the
10896 @kindex info os threads
10898 Display the list of threads running on the target. For each thread,
10899 @value{GDBN} prints the identifier of the process that the thread
10900 belongs to, the command of the process, the thread identifier, and the
10901 processor core that it is currently running on. The main thread of a
10902 process is not listed.
10906 If @var{infotype} is omitted, then list the possible values for
10907 @var{infotype} and the kind of OS information available for each
10908 @var{infotype}. If the target does not return a list of possible
10909 types, this command will report an error.
10912 @node Memory Region Attributes
10913 @section Memory Region Attributes
10914 @cindex memory region attributes
10916 @dfn{Memory region attributes} allow you to describe special handling
10917 required by regions of your target's memory. @value{GDBN} uses
10918 attributes to determine whether to allow certain types of memory
10919 accesses; whether to use specific width accesses; and whether to cache
10920 target memory. By default the description of memory regions is
10921 fetched from the target (if the current target supports this), but the
10922 user can override the fetched regions.
10924 Defined memory regions can be individually enabled and disabled. When a
10925 memory region is disabled, @value{GDBN} uses the default attributes when
10926 accessing memory in that region. Similarly, if no memory regions have
10927 been defined, @value{GDBN} uses the default attributes when accessing
10930 When a memory region is defined, it is given a number to identify it;
10931 to enable, disable, or remove a memory region, you specify that number.
10935 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10936 Define a memory region bounded by @var{lower} and @var{upper} with
10937 attributes @var{attributes}@dots{}, and add it to the list of regions
10938 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10939 case: it is treated as the target's maximum memory address.
10940 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10943 Discard any user changes to the memory regions and use target-supplied
10944 regions, if available, or no regions if the target does not support.
10947 @item delete mem @var{nums}@dots{}
10948 Remove memory regions @var{nums}@dots{} from the list of regions
10949 monitored by @value{GDBN}.
10951 @kindex disable mem
10952 @item disable mem @var{nums}@dots{}
10953 Disable monitoring of memory regions @var{nums}@dots{}.
10954 A disabled memory region is not forgotten.
10955 It may be enabled again later.
10958 @item enable mem @var{nums}@dots{}
10959 Enable monitoring of memory regions @var{nums}@dots{}.
10963 Print a table of all defined memory regions, with the following columns
10967 @item Memory Region Number
10968 @item Enabled or Disabled.
10969 Enabled memory regions are marked with @samp{y}.
10970 Disabled memory regions are marked with @samp{n}.
10973 The address defining the inclusive lower bound of the memory region.
10976 The address defining the exclusive upper bound of the memory region.
10979 The list of attributes set for this memory region.
10984 @subsection Attributes
10986 @subsubsection Memory Access Mode
10987 The access mode attributes set whether @value{GDBN} may make read or
10988 write accesses to a memory region.
10990 While these attributes prevent @value{GDBN} from performing invalid
10991 memory accesses, they do nothing to prevent the target system, I/O DMA,
10992 etc.@: from accessing memory.
10996 Memory is read only.
10998 Memory is write only.
11000 Memory is read/write. This is the default.
11003 @subsubsection Memory Access Size
11004 The access size attribute tells @value{GDBN} to use specific sized
11005 accesses in the memory region. Often memory mapped device registers
11006 require specific sized accesses. If no access size attribute is
11007 specified, @value{GDBN} may use accesses of any size.
11011 Use 8 bit memory accesses.
11013 Use 16 bit memory accesses.
11015 Use 32 bit memory accesses.
11017 Use 64 bit memory accesses.
11020 @c @subsubsection Hardware/Software Breakpoints
11021 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11022 @c will use hardware or software breakpoints for the internal breakpoints
11023 @c used by the step, next, finish, until, etc. commands.
11027 @c Always use hardware breakpoints
11028 @c @item swbreak (default)
11031 @subsubsection Data Cache
11032 The data cache attributes set whether @value{GDBN} will cache target
11033 memory. While this generally improves performance by reducing debug
11034 protocol overhead, it can lead to incorrect results because @value{GDBN}
11035 does not know about volatile variables or memory mapped device
11040 Enable @value{GDBN} to cache target memory.
11042 Disable @value{GDBN} from caching target memory. This is the default.
11045 @subsection Memory Access Checking
11046 @value{GDBN} can be instructed to refuse accesses to memory that is
11047 not explicitly described. This can be useful if accessing such
11048 regions has undesired effects for a specific target, or to provide
11049 better error checking. The following commands control this behaviour.
11052 @kindex set mem inaccessible-by-default
11053 @item set mem inaccessible-by-default [on|off]
11054 If @code{on} is specified, make @value{GDBN} treat memory not
11055 explicitly described by the memory ranges as non-existent and refuse accesses
11056 to such memory. The checks are only performed if there's at least one
11057 memory range defined. If @code{off} is specified, make @value{GDBN}
11058 treat the memory not explicitly described by the memory ranges as RAM.
11059 The default value is @code{on}.
11060 @kindex show mem inaccessible-by-default
11061 @item show mem inaccessible-by-default
11062 Show the current handling of accesses to unknown memory.
11066 @c @subsubsection Memory Write Verification
11067 @c The memory write verification attributes set whether @value{GDBN}
11068 @c will re-reads data after each write to verify the write was successful.
11072 @c @item noverify (default)
11075 @node Dump/Restore Files
11076 @section Copy Between Memory and a File
11077 @cindex dump/restore files
11078 @cindex append data to a file
11079 @cindex dump data to a file
11080 @cindex restore data from a file
11082 You can use the commands @code{dump}, @code{append}, and
11083 @code{restore} to copy data between target memory and a file. The
11084 @code{dump} and @code{append} commands write data to a file, and the
11085 @code{restore} command reads data from a file back into the inferior's
11086 memory. Files may be in binary, Motorola S-record, Intel hex,
11087 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11088 append to binary files, and cannot read from Verilog Hex files.
11093 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11094 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11095 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11096 or the value of @var{expr}, to @var{filename} in the given format.
11098 The @var{format} parameter may be any one of:
11105 Motorola S-record format.
11107 Tektronix Hex format.
11109 Verilog Hex format.
11112 @value{GDBN} uses the same definitions of these formats as the
11113 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11114 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11118 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11119 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11120 Append the contents of memory from @var{start_addr} to @var{end_addr},
11121 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11122 (@value{GDBN} can only append data to files in raw binary form.)
11125 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11126 Restore the contents of file @var{filename} into memory. The
11127 @code{restore} command can automatically recognize any known @sc{bfd}
11128 file format, except for raw binary. To restore a raw binary file you
11129 must specify the optional keyword @code{binary} after the filename.
11131 If @var{bias} is non-zero, its value will be added to the addresses
11132 contained in the file. Binary files always start at address zero, so
11133 they will be restored at address @var{bias}. Other bfd files have
11134 a built-in location; they will be restored at offset @var{bias}
11135 from that location.
11137 If @var{start} and/or @var{end} are non-zero, then only data between
11138 file offset @var{start} and file offset @var{end} will be restored.
11139 These offsets are relative to the addresses in the file, before
11140 the @var{bias} argument is applied.
11144 @node Core File Generation
11145 @section How to Produce a Core File from Your Program
11146 @cindex dump core from inferior
11148 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11149 image of a running process and its process status (register values
11150 etc.). Its primary use is post-mortem debugging of a program that
11151 crashed while it ran outside a debugger. A program that crashes
11152 automatically produces a core file, unless this feature is disabled by
11153 the user. @xref{Files}, for information on invoking @value{GDBN} in
11154 the post-mortem debugging mode.
11156 Occasionally, you may wish to produce a core file of the program you
11157 are debugging in order to preserve a snapshot of its state.
11158 @value{GDBN} has a special command for that.
11162 @kindex generate-core-file
11163 @item generate-core-file [@var{file}]
11164 @itemx gcore [@var{file}]
11165 Produce a core dump of the inferior process. The optional argument
11166 @var{file} specifies the file name where to put the core dump. If not
11167 specified, the file name defaults to @file{core.@var{pid}}, where
11168 @var{pid} is the inferior process ID.
11170 Note that this command is implemented only for some systems (as of
11171 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11173 On @sc{gnu}/Linux, this command can take into account the value of the
11174 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11175 dump (@pxref{set use-coredump-filter}).
11177 @kindex set use-coredump-filter
11178 @anchor{set use-coredump-filter}
11179 @item set use-coredump-filter on
11180 @itemx set use-coredump-filter off
11181 Enable or disable the use of the file
11182 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11183 files. This file is used by the Linux kernel to decide what types of
11184 memory mappings will be dumped or ignored when generating a core dump
11185 file. @var{pid} is the process ID of a currently running process.
11187 To make use of this feature, you have to write in the
11188 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11189 which is a bit mask representing the memory mapping types. If a bit
11190 is set in the bit mask, then the memory mappings of the corresponding
11191 types will be dumped; otherwise, they will be ignored. This
11192 configuration is inherited by child processes. For more information
11193 about the bits that can be set in the
11194 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11195 manpage of @code{core(5)}.
11197 By default, this option is @code{on}. If this option is turned
11198 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11199 and instead uses the same default value as the Linux kernel in order
11200 to decide which pages will be dumped in the core dump file. This
11201 value is currently @code{0x33}, which means that bits @code{0}
11202 (anonymous private mappings), @code{1} (anonymous shared mappings),
11203 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11204 This will cause these memory mappings to be dumped automatically.
11207 @node Character Sets
11208 @section Character Sets
11209 @cindex character sets
11211 @cindex translating between character sets
11212 @cindex host character set
11213 @cindex target character set
11215 If the program you are debugging uses a different character set to
11216 represent characters and strings than the one @value{GDBN} uses itself,
11217 @value{GDBN} can automatically translate between the character sets for
11218 you. The character set @value{GDBN} uses we call the @dfn{host
11219 character set}; the one the inferior program uses we call the
11220 @dfn{target character set}.
11222 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11223 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11224 remote protocol (@pxref{Remote Debugging}) to debug a program
11225 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11226 then the host character set is Latin-1, and the target character set is
11227 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11228 target-charset EBCDIC-US}, then @value{GDBN} translates between
11229 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11230 character and string literals in expressions.
11232 @value{GDBN} has no way to automatically recognize which character set
11233 the inferior program uses; you must tell it, using the @code{set
11234 target-charset} command, described below.
11236 Here are the commands for controlling @value{GDBN}'s character set
11240 @item set target-charset @var{charset}
11241 @kindex set target-charset
11242 Set the current target character set to @var{charset}. To display the
11243 list of supported target character sets, type
11244 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11246 @item set host-charset @var{charset}
11247 @kindex set host-charset
11248 Set the current host character set to @var{charset}.
11250 By default, @value{GDBN} uses a host character set appropriate to the
11251 system it is running on; you can override that default using the
11252 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11253 automatically determine the appropriate host character set. In this
11254 case, @value{GDBN} uses @samp{UTF-8}.
11256 @value{GDBN} can only use certain character sets as its host character
11257 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11258 @value{GDBN} will list the host character sets it supports.
11260 @item set charset @var{charset}
11261 @kindex set charset
11262 Set the current host and target character sets to @var{charset}. As
11263 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11264 @value{GDBN} will list the names of the character sets that can be used
11265 for both host and target.
11268 @kindex show charset
11269 Show the names of the current host and target character sets.
11271 @item show host-charset
11272 @kindex show host-charset
11273 Show the name of the current host character set.
11275 @item show target-charset
11276 @kindex show target-charset
11277 Show the name of the current target character set.
11279 @item set target-wide-charset @var{charset}
11280 @kindex set target-wide-charset
11281 Set the current target's wide character set to @var{charset}. This is
11282 the character set used by the target's @code{wchar_t} type. To
11283 display the list of supported wide character sets, type
11284 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11286 @item show target-wide-charset
11287 @kindex show target-wide-charset
11288 Show the name of the current target's wide character set.
11291 Here is an example of @value{GDBN}'s character set support in action.
11292 Assume that the following source code has been placed in the file
11293 @file{charset-test.c}:
11299 = @{72, 101, 108, 108, 111, 44, 32, 119,
11300 111, 114, 108, 100, 33, 10, 0@};
11301 char ibm1047_hello[]
11302 = @{200, 133, 147, 147, 150, 107, 64, 166,
11303 150, 153, 147, 132, 90, 37, 0@};
11307 printf ("Hello, world!\n");
11311 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11312 containing the string @samp{Hello, world!} followed by a newline,
11313 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11315 We compile the program, and invoke the debugger on it:
11318 $ gcc -g charset-test.c -o charset-test
11319 $ gdb -nw charset-test
11320 GNU gdb 2001-12-19-cvs
11321 Copyright 2001 Free Software Foundation, Inc.
11326 We can use the @code{show charset} command to see what character sets
11327 @value{GDBN} is currently using to interpret and display characters and
11331 (@value{GDBP}) show charset
11332 The current host and target character set is `ISO-8859-1'.
11336 For the sake of printing this manual, let's use @sc{ascii} as our
11337 initial character set:
11339 (@value{GDBP}) set charset ASCII
11340 (@value{GDBP}) show charset
11341 The current host and target character set is `ASCII'.
11345 Let's assume that @sc{ascii} is indeed the correct character set for our
11346 host system --- in other words, let's assume that if @value{GDBN} prints
11347 characters using the @sc{ascii} character set, our terminal will display
11348 them properly. Since our current target character set is also
11349 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11352 (@value{GDBP}) print ascii_hello
11353 $1 = 0x401698 "Hello, world!\n"
11354 (@value{GDBP}) print ascii_hello[0]
11359 @value{GDBN} uses the target character set for character and string
11360 literals you use in expressions:
11363 (@value{GDBP}) print '+'
11368 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11371 @value{GDBN} relies on the user to tell it which character set the
11372 target program uses. If we print @code{ibm1047_hello} while our target
11373 character set is still @sc{ascii}, we get jibberish:
11376 (@value{GDBP}) print ibm1047_hello
11377 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11378 (@value{GDBP}) print ibm1047_hello[0]
11383 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11384 @value{GDBN} tells us the character sets it supports:
11387 (@value{GDBP}) set target-charset
11388 ASCII EBCDIC-US IBM1047 ISO-8859-1
11389 (@value{GDBP}) set target-charset
11392 We can select @sc{ibm1047} as our target character set, and examine the
11393 program's strings again. Now the @sc{ascii} string is wrong, but
11394 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11395 target character set, @sc{ibm1047}, to the host character set,
11396 @sc{ascii}, and they display correctly:
11399 (@value{GDBP}) set target-charset IBM1047
11400 (@value{GDBP}) show charset
11401 The current host character set is `ASCII'.
11402 The current target character set is `IBM1047'.
11403 (@value{GDBP}) print ascii_hello
11404 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11405 (@value{GDBP}) print ascii_hello[0]
11407 (@value{GDBP}) print ibm1047_hello
11408 $8 = 0x4016a8 "Hello, world!\n"
11409 (@value{GDBP}) print ibm1047_hello[0]
11414 As above, @value{GDBN} uses the target character set for character and
11415 string literals you use in expressions:
11418 (@value{GDBP}) print '+'
11423 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11426 @node Caching Target Data
11427 @section Caching Data of Targets
11428 @cindex caching data of targets
11430 @value{GDBN} caches data exchanged between the debugger and a target.
11431 Each cache is associated with the address space of the inferior.
11432 @xref{Inferiors and Programs}, about inferior and address space.
11433 Such caching generally improves performance in remote debugging
11434 (@pxref{Remote Debugging}), because it reduces the overhead of the
11435 remote protocol by bundling memory reads and writes into large chunks.
11436 Unfortunately, simply caching everything would lead to incorrect results,
11437 since @value{GDBN} does not necessarily know anything about volatile
11438 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11439 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11441 Therefore, by default, @value{GDBN} only caches data
11442 known to be on the stack@footnote{In non-stop mode, it is moderately
11443 rare for a running thread to modify the stack of a stopped thread
11444 in a way that would interfere with a backtrace, and caching of
11445 stack reads provides a significant speed up of remote backtraces.} or
11446 in the code segment.
11447 Other regions of memory can be explicitly marked as
11448 cacheable; @pxref{Memory Region Attributes}.
11451 @kindex set remotecache
11452 @item set remotecache on
11453 @itemx set remotecache off
11454 This option no longer does anything; it exists for compatibility
11457 @kindex show remotecache
11458 @item show remotecache
11459 Show the current state of the obsolete remotecache flag.
11461 @kindex set stack-cache
11462 @item set stack-cache on
11463 @itemx set stack-cache off
11464 Enable or disable caching of stack accesses. When @code{on}, use
11465 caching. By default, this option is @code{on}.
11467 @kindex show stack-cache
11468 @item show stack-cache
11469 Show the current state of data caching for memory accesses.
11471 @kindex set code-cache
11472 @item set code-cache on
11473 @itemx set code-cache off
11474 Enable or disable caching of code segment accesses. When @code{on},
11475 use caching. By default, this option is @code{on}. This improves
11476 performance of disassembly in remote debugging.
11478 @kindex show code-cache
11479 @item show code-cache
11480 Show the current state of target memory cache for code segment
11483 @kindex info dcache
11484 @item info dcache @r{[}line@r{]}
11485 Print the information about the performance of data cache of the
11486 current inferior's address space. The information displayed
11487 includes the dcache width and depth, and for each cache line, its
11488 number, address, and how many times it was referenced. This
11489 command is useful for debugging the data cache operation.
11491 If a line number is specified, the contents of that line will be
11494 @item set dcache size @var{size}
11495 @cindex dcache size
11496 @kindex set dcache size
11497 Set maximum number of entries in dcache (dcache depth above).
11499 @item set dcache line-size @var{line-size}
11500 @cindex dcache line-size
11501 @kindex set dcache line-size
11502 Set number of bytes each dcache entry caches (dcache width above).
11503 Must be a power of 2.
11505 @item show dcache size
11506 @kindex show dcache size
11507 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11509 @item show dcache line-size
11510 @kindex show dcache line-size
11511 Show default size of dcache lines.
11515 @node Searching Memory
11516 @section Search Memory
11517 @cindex searching memory
11519 Memory can be searched for a particular sequence of bytes with the
11520 @code{find} command.
11524 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11525 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11526 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11527 etc. The search begins at address @var{start_addr} and continues for either
11528 @var{len} bytes or through to @var{end_addr} inclusive.
11531 @var{s} and @var{n} are optional parameters.
11532 They may be specified in either order, apart or together.
11535 @item @var{s}, search query size
11536 The size of each search query value.
11542 halfwords (two bytes)
11546 giant words (eight bytes)
11549 All values are interpreted in the current language.
11550 This means, for example, that if the current source language is C/C@t{++}
11551 then searching for the string ``hello'' includes the trailing '\0'.
11553 If the value size is not specified, it is taken from the
11554 value's type in the current language.
11555 This is useful when one wants to specify the search
11556 pattern as a mixture of types.
11557 Note that this means, for example, that in the case of C-like languages
11558 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11559 which is typically four bytes.
11561 @item @var{n}, maximum number of finds
11562 The maximum number of matches to print. The default is to print all finds.
11565 You can use strings as search values. Quote them with double-quotes
11567 The string value is copied into the search pattern byte by byte,
11568 regardless of the endianness of the target and the size specification.
11570 The address of each match found is printed as well as a count of the
11571 number of matches found.
11573 The address of the last value found is stored in convenience variable
11575 A count of the number of matches is stored in @samp{$numfound}.
11577 For example, if stopped at the @code{printf} in this function:
11583 static char hello[] = "hello-hello";
11584 static struct @{ char c; short s; int i; @}
11585 __attribute__ ((packed)) mixed
11586 = @{ 'c', 0x1234, 0x87654321 @};
11587 printf ("%s\n", hello);
11592 you get during debugging:
11595 (gdb) find &hello[0], +sizeof(hello), "hello"
11596 0x804956d <hello.1620+6>
11598 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11599 0x8049567 <hello.1620>
11600 0x804956d <hello.1620+6>
11602 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11603 0x8049567 <hello.1620>
11605 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11606 0x8049560 <mixed.1625>
11608 (gdb) print $numfound
11611 $2 = (void *) 0x8049560
11614 @node Optimized Code
11615 @chapter Debugging Optimized Code
11616 @cindex optimized code, debugging
11617 @cindex debugging optimized code
11619 Almost all compilers support optimization. With optimization
11620 disabled, the compiler generates assembly code that corresponds
11621 directly to your source code, in a simplistic way. As the compiler
11622 applies more powerful optimizations, the generated assembly code
11623 diverges from your original source code. With help from debugging
11624 information generated by the compiler, @value{GDBN} can map from
11625 the running program back to constructs from your original source.
11627 @value{GDBN} is more accurate with optimization disabled. If you
11628 can recompile without optimization, it is easier to follow the
11629 progress of your program during debugging. But, there are many cases
11630 where you may need to debug an optimized version.
11632 When you debug a program compiled with @samp{-g -O}, remember that the
11633 optimizer has rearranged your code; the debugger shows you what is
11634 really there. Do not be too surprised when the execution path does not
11635 exactly match your source file! An extreme example: if you define a
11636 variable, but never use it, @value{GDBN} never sees that
11637 variable---because the compiler optimizes it out of existence.
11639 Some things do not work as well with @samp{-g -O} as with just
11640 @samp{-g}, particularly on machines with instruction scheduling. If in
11641 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11642 please report it to us as a bug (including a test case!).
11643 @xref{Variables}, for more information about debugging optimized code.
11646 * Inline Functions:: How @value{GDBN} presents inlining
11647 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11650 @node Inline Functions
11651 @section Inline Functions
11652 @cindex inline functions, debugging
11654 @dfn{Inlining} is an optimization that inserts a copy of the function
11655 body directly at each call site, instead of jumping to a shared
11656 routine. @value{GDBN} displays inlined functions just like
11657 non-inlined functions. They appear in backtraces. You can view their
11658 arguments and local variables, step into them with @code{step}, skip
11659 them with @code{next}, and escape from them with @code{finish}.
11660 You can check whether a function was inlined by using the
11661 @code{info frame} command.
11663 For @value{GDBN} to support inlined functions, the compiler must
11664 record information about inlining in the debug information ---
11665 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11666 other compilers do also. @value{GDBN} only supports inlined functions
11667 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11668 do not emit two required attributes (@samp{DW_AT_call_file} and
11669 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11670 function calls with earlier versions of @value{NGCC}. It instead
11671 displays the arguments and local variables of inlined functions as
11672 local variables in the caller.
11674 The body of an inlined function is directly included at its call site;
11675 unlike a non-inlined function, there are no instructions devoted to
11676 the call. @value{GDBN} still pretends that the call site and the
11677 start of the inlined function are different instructions. Stepping to
11678 the call site shows the call site, and then stepping again shows
11679 the first line of the inlined function, even though no additional
11680 instructions are executed.
11682 This makes source-level debugging much clearer; you can see both the
11683 context of the call and then the effect of the call. Only stepping by
11684 a single instruction using @code{stepi} or @code{nexti} does not do
11685 this; single instruction steps always show the inlined body.
11687 There are some ways that @value{GDBN} does not pretend that inlined
11688 function calls are the same as normal calls:
11692 Setting breakpoints at the call site of an inlined function may not
11693 work, because the call site does not contain any code. @value{GDBN}
11694 may incorrectly move the breakpoint to the next line of the enclosing
11695 function, after the call. This limitation will be removed in a future
11696 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11697 or inside the inlined function instead.
11700 @value{GDBN} cannot locate the return value of inlined calls after
11701 using the @code{finish} command. This is a limitation of compiler-generated
11702 debugging information; after @code{finish}, you can step to the next line
11703 and print a variable where your program stored the return value.
11707 @node Tail Call Frames
11708 @section Tail Call Frames
11709 @cindex tail call frames, debugging
11711 Function @code{B} can call function @code{C} in its very last statement. In
11712 unoptimized compilation the call of @code{C} is immediately followed by return
11713 instruction at the end of @code{B} code. Optimizing compiler may replace the
11714 call and return in function @code{B} into one jump to function @code{C}
11715 instead. Such use of a jump instruction is called @dfn{tail call}.
11717 During execution of function @code{C}, there will be no indication in the
11718 function call stack frames that it was tail-called from @code{B}. If function
11719 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11720 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11721 some cases @value{GDBN} can determine that @code{C} was tail-called from
11722 @code{B}, and it will then create fictitious call frame for that, with the
11723 return address set up as if @code{B} called @code{C} normally.
11725 This functionality is currently supported only by DWARF 2 debugging format and
11726 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11727 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11730 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11731 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11735 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11737 Stack level 1, frame at 0x7fffffffda30:
11738 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11739 tail call frame, caller of frame at 0x7fffffffda30
11740 source language c++.
11741 Arglist at unknown address.
11742 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11745 The detection of all the possible code path executions can find them ambiguous.
11746 There is no execution history stored (possible @ref{Reverse Execution} is never
11747 used for this purpose) and the last known caller could have reached the known
11748 callee by multiple different jump sequences. In such case @value{GDBN} still
11749 tries to show at least all the unambiguous top tail callers and all the
11750 unambiguous bottom tail calees, if any.
11753 @anchor{set debug entry-values}
11754 @item set debug entry-values
11755 @kindex set debug entry-values
11756 When set to on, enables printing of analysis messages for both frame argument
11757 values at function entry and tail calls. It will show all the possible valid
11758 tail calls code paths it has considered. It will also print the intersection
11759 of them with the final unambiguous (possibly partial or even empty) code path
11762 @item show debug entry-values
11763 @kindex show debug entry-values
11764 Show the current state of analysis messages printing for both frame argument
11765 values at function entry and tail calls.
11768 The analysis messages for tail calls can for example show why the virtual tail
11769 call frame for function @code{c} has not been recognized (due to the indirect
11770 reference by variable @code{x}):
11773 static void __attribute__((noinline, noclone)) c (void);
11774 void (*x) (void) = c;
11775 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11776 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11777 int main (void) @{ x (); return 0; @}
11779 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11780 DW_TAG_GNU_call_site 0x40039a in main
11782 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11785 #1 0x000000000040039a in main () at t.c:5
11788 Another possibility is an ambiguous virtual tail call frames resolution:
11792 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11793 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11794 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11795 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11796 static void __attribute__((noinline, noclone)) b (void)
11797 @{ if (i) c (); else e (); @}
11798 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11799 int main (void) @{ a (); return 0; @}
11801 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11802 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11803 tailcall: reduced: 0x4004d2(a) |
11806 #1 0x00000000004004d2 in a () at t.c:8
11807 #2 0x0000000000400395 in main () at t.c:9
11810 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11811 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11813 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11814 @ifset HAVE_MAKEINFO_CLICK
11815 @set ARROW @click{}
11816 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11817 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11819 @ifclear HAVE_MAKEINFO_CLICK
11821 @set CALLSEQ1B @value{CALLSEQ1A}
11822 @set CALLSEQ2B @value{CALLSEQ2A}
11825 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11826 The code can have possible execution paths @value{CALLSEQ1B} or
11827 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11829 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11830 has found. It then finds another possible calling sequcen - that one is
11831 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11832 printed as the @code{reduced:} calling sequence. That one could have many
11833 futher @code{compare:} and @code{reduced:} statements as long as there remain
11834 any non-ambiguous sequence entries.
11836 For the frame of function @code{b} in both cases there are different possible
11837 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11838 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11839 therefore this one is displayed to the user while the ambiguous frames are
11842 There can be also reasons why printing of frame argument values at function
11847 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11848 static void __attribute__((noinline, noclone)) a (int i);
11849 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11850 static void __attribute__((noinline, noclone)) a (int i)
11851 @{ if (i) b (i - 1); else c (0); @}
11852 int main (void) @{ a (5); return 0; @}
11855 #0 c (i=i@@entry=0) at t.c:2
11856 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11857 function "a" at 0x400420 can call itself via tail calls
11858 i=<optimized out>) at t.c:6
11859 #2 0x000000000040036e in main () at t.c:7
11862 @value{GDBN} cannot find out from the inferior state if and how many times did
11863 function @code{a} call itself (via function @code{b}) as these calls would be
11864 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11865 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11866 prints @code{<optimized out>} instead.
11869 @chapter C Preprocessor Macros
11871 Some languages, such as C and C@t{++}, provide a way to define and invoke
11872 ``preprocessor macros'' which expand into strings of tokens.
11873 @value{GDBN} can evaluate expressions containing macro invocations, show
11874 the result of macro expansion, and show a macro's definition, including
11875 where it was defined.
11877 You may need to compile your program specially to provide @value{GDBN}
11878 with information about preprocessor macros. Most compilers do not
11879 include macros in their debugging information, even when you compile
11880 with the @option{-g} flag. @xref{Compilation}.
11882 A program may define a macro at one point, remove that definition later,
11883 and then provide a different definition after that. Thus, at different
11884 points in the program, a macro may have different definitions, or have
11885 no definition at all. If there is a current stack frame, @value{GDBN}
11886 uses the macros in scope at that frame's source code line. Otherwise,
11887 @value{GDBN} uses the macros in scope at the current listing location;
11890 Whenever @value{GDBN} evaluates an expression, it always expands any
11891 macro invocations present in the expression. @value{GDBN} also provides
11892 the following commands for working with macros explicitly.
11896 @kindex macro expand
11897 @cindex macro expansion, showing the results of preprocessor
11898 @cindex preprocessor macro expansion, showing the results of
11899 @cindex expanding preprocessor macros
11900 @item macro expand @var{expression}
11901 @itemx macro exp @var{expression}
11902 Show the results of expanding all preprocessor macro invocations in
11903 @var{expression}. Since @value{GDBN} simply expands macros, but does
11904 not parse the result, @var{expression} need not be a valid expression;
11905 it can be any string of tokens.
11908 @item macro expand-once @var{expression}
11909 @itemx macro exp1 @var{expression}
11910 @cindex expand macro once
11911 @i{(This command is not yet implemented.)} Show the results of
11912 expanding those preprocessor macro invocations that appear explicitly in
11913 @var{expression}. Macro invocations appearing in that expansion are
11914 left unchanged. This command allows you to see the effect of a
11915 particular macro more clearly, without being confused by further
11916 expansions. Since @value{GDBN} simply expands macros, but does not
11917 parse the result, @var{expression} need not be a valid expression; it
11918 can be any string of tokens.
11921 @cindex macro definition, showing
11922 @cindex definition of a macro, showing
11923 @cindex macros, from debug info
11924 @item info macro [-a|-all] [--] @var{macro}
11925 Show the current definition or all definitions of the named @var{macro},
11926 and describe the source location or compiler command-line where that
11927 definition was established. The optional double dash is to signify the end of
11928 argument processing and the beginning of @var{macro} for non C-like macros where
11929 the macro may begin with a hyphen.
11931 @kindex info macros
11932 @item info macros @var{location}
11933 Show all macro definitions that are in effect at the location specified
11934 by @var{location}, and describe the source location or compiler
11935 command-line where those definitions were established.
11937 @kindex macro define
11938 @cindex user-defined macros
11939 @cindex defining macros interactively
11940 @cindex macros, user-defined
11941 @item macro define @var{macro} @var{replacement-list}
11942 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11943 Introduce a definition for a preprocessor macro named @var{macro},
11944 invocations of which are replaced by the tokens given in
11945 @var{replacement-list}. The first form of this command defines an
11946 ``object-like'' macro, which takes no arguments; the second form
11947 defines a ``function-like'' macro, which takes the arguments given in
11950 A definition introduced by this command is in scope in every
11951 expression evaluated in @value{GDBN}, until it is removed with the
11952 @code{macro undef} command, described below. The definition overrides
11953 all definitions for @var{macro} present in the program being debugged,
11954 as well as any previous user-supplied definition.
11956 @kindex macro undef
11957 @item macro undef @var{macro}
11958 Remove any user-supplied definition for the macro named @var{macro}.
11959 This command only affects definitions provided with the @code{macro
11960 define} command, described above; it cannot remove definitions present
11961 in the program being debugged.
11965 List all the macros defined using the @code{macro define} command.
11968 @cindex macros, example of debugging with
11969 Here is a transcript showing the above commands in action. First, we
11970 show our source files:
11975 #include "sample.h"
11978 #define ADD(x) (M + x)
11983 printf ("Hello, world!\n");
11985 printf ("We're so creative.\n");
11987 printf ("Goodbye, world!\n");
11994 Now, we compile the program using the @sc{gnu} C compiler,
11995 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11996 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11997 and @option{-gdwarf-4}; we recommend always choosing the most recent
11998 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11999 includes information about preprocessor macros in the debugging
12003 $ gcc -gdwarf-2 -g3 sample.c -o sample
12007 Now, we start @value{GDBN} on our sample program:
12011 GNU gdb 2002-05-06-cvs
12012 Copyright 2002 Free Software Foundation, Inc.
12013 GDB is free software, @dots{}
12017 We can expand macros and examine their definitions, even when the
12018 program is not running. @value{GDBN} uses the current listing position
12019 to decide which macro definitions are in scope:
12022 (@value{GDBP}) list main
12025 5 #define ADD(x) (M + x)
12030 10 printf ("Hello, world!\n");
12032 12 printf ("We're so creative.\n");
12033 (@value{GDBP}) info macro ADD
12034 Defined at /home/jimb/gdb/macros/play/sample.c:5
12035 #define ADD(x) (M + x)
12036 (@value{GDBP}) info macro Q
12037 Defined at /home/jimb/gdb/macros/play/sample.h:1
12038 included at /home/jimb/gdb/macros/play/sample.c:2
12040 (@value{GDBP}) macro expand ADD(1)
12041 expands to: (42 + 1)
12042 (@value{GDBP}) macro expand-once ADD(1)
12043 expands to: once (M + 1)
12047 In the example above, note that @code{macro expand-once} expands only
12048 the macro invocation explicit in the original text --- the invocation of
12049 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12050 which was introduced by @code{ADD}.
12052 Once the program is running, @value{GDBN} uses the macro definitions in
12053 force at the source line of the current stack frame:
12056 (@value{GDBP}) break main
12057 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12059 Starting program: /home/jimb/gdb/macros/play/sample
12061 Breakpoint 1, main () at sample.c:10
12062 10 printf ("Hello, world!\n");
12066 At line 10, the definition of the macro @code{N} at line 9 is in force:
12069 (@value{GDBP}) info macro N
12070 Defined at /home/jimb/gdb/macros/play/sample.c:9
12072 (@value{GDBP}) macro expand N Q M
12073 expands to: 28 < 42
12074 (@value{GDBP}) print N Q M
12079 As we step over directives that remove @code{N}'s definition, and then
12080 give it a new definition, @value{GDBN} finds the definition (or lack
12081 thereof) in force at each point:
12084 (@value{GDBP}) next
12086 12 printf ("We're so creative.\n");
12087 (@value{GDBP}) info macro N
12088 The symbol `N' has no definition as a C/C++ preprocessor macro
12089 at /home/jimb/gdb/macros/play/sample.c:12
12090 (@value{GDBP}) next
12092 14 printf ("Goodbye, world!\n");
12093 (@value{GDBP}) info macro N
12094 Defined at /home/jimb/gdb/macros/play/sample.c:13
12096 (@value{GDBP}) macro expand N Q M
12097 expands to: 1729 < 42
12098 (@value{GDBP}) print N Q M
12103 In addition to source files, macros can be defined on the compilation command
12104 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12105 such a way, @value{GDBN} displays the location of their definition as line zero
12106 of the source file submitted to the compiler.
12109 (@value{GDBP}) info macro __STDC__
12110 Defined at /home/jimb/gdb/macros/play/sample.c:0
12117 @chapter Tracepoints
12118 @c This chapter is based on the documentation written by Michael
12119 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12121 @cindex tracepoints
12122 In some applications, it is not feasible for the debugger to interrupt
12123 the program's execution long enough for the developer to learn
12124 anything helpful about its behavior. If the program's correctness
12125 depends on its real-time behavior, delays introduced by a debugger
12126 might cause the program to change its behavior drastically, or perhaps
12127 fail, even when the code itself is correct. It is useful to be able
12128 to observe the program's behavior without interrupting it.
12130 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12131 specify locations in the program, called @dfn{tracepoints}, and
12132 arbitrary expressions to evaluate when those tracepoints are reached.
12133 Later, using the @code{tfind} command, you can examine the values
12134 those expressions had when the program hit the tracepoints. The
12135 expressions may also denote objects in memory---structures or arrays,
12136 for example---whose values @value{GDBN} should record; while visiting
12137 a particular tracepoint, you may inspect those objects as if they were
12138 in memory at that moment. However, because @value{GDBN} records these
12139 values without interacting with you, it can do so quickly and
12140 unobtrusively, hopefully not disturbing the program's behavior.
12142 The tracepoint facility is currently available only for remote
12143 targets. @xref{Targets}. In addition, your remote target must know
12144 how to collect trace data. This functionality is implemented in the
12145 remote stub; however, none of the stubs distributed with @value{GDBN}
12146 support tracepoints as of this writing. The format of the remote
12147 packets used to implement tracepoints are described in @ref{Tracepoint
12150 It is also possible to get trace data from a file, in a manner reminiscent
12151 of corefiles; you specify the filename, and use @code{tfind} to search
12152 through the file. @xref{Trace Files}, for more details.
12154 This chapter describes the tracepoint commands and features.
12157 * Set Tracepoints::
12158 * Analyze Collected Data::
12159 * Tracepoint Variables::
12163 @node Set Tracepoints
12164 @section Commands to Set Tracepoints
12166 Before running such a @dfn{trace experiment}, an arbitrary number of
12167 tracepoints can be set. A tracepoint is actually a special type of
12168 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12169 standard breakpoint commands. For instance, as with breakpoints,
12170 tracepoint numbers are successive integers starting from one, and many
12171 of the commands associated with tracepoints take the tracepoint number
12172 as their argument, to identify which tracepoint to work on.
12174 For each tracepoint, you can specify, in advance, some arbitrary set
12175 of data that you want the target to collect in the trace buffer when
12176 it hits that tracepoint. The collected data can include registers,
12177 local variables, or global data. Later, you can use @value{GDBN}
12178 commands to examine the values these data had at the time the
12179 tracepoint was hit.
12181 Tracepoints do not support every breakpoint feature. Ignore counts on
12182 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12183 commands when they are hit. Tracepoints may not be thread-specific
12186 @cindex fast tracepoints
12187 Some targets may support @dfn{fast tracepoints}, which are inserted in
12188 a different way (such as with a jump instead of a trap), that is
12189 faster but possibly restricted in where they may be installed.
12191 @cindex static tracepoints
12192 @cindex markers, static tracepoints
12193 @cindex probing markers, static tracepoints
12194 Regular and fast tracepoints are dynamic tracing facilities, meaning
12195 that they can be used to insert tracepoints at (almost) any location
12196 in the target. Some targets may also support controlling @dfn{static
12197 tracepoints} from @value{GDBN}. With static tracing, a set of
12198 instrumentation points, also known as @dfn{markers}, are embedded in
12199 the target program, and can be activated or deactivated by name or
12200 address. These are usually placed at locations which facilitate
12201 investigating what the target is actually doing. @value{GDBN}'s
12202 support for static tracing includes being able to list instrumentation
12203 points, and attach them with @value{GDBN} defined high level
12204 tracepoints that expose the whole range of convenience of
12205 @value{GDBN}'s tracepoints support. Namely, support for collecting
12206 registers values and values of global or local (to the instrumentation
12207 point) variables; tracepoint conditions and trace state variables.
12208 The act of installing a @value{GDBN} static tracepoint on an
12209 instrumentation point, or marker, is referred to as @dfn{probing} a
12210 static tracepoint marker.
12212 @code{gdbserver} supports tracepoints on some target systems.
12213 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12215 This section describes commands to set tracepoints and associated
12216 conditions and actions.
12219 * Create and Delete Tracepoints::
12220 * Enable and Disable Tracepoints::
12221 * Tracepoint Passcounts::
12222 * Tracepoint Conditions::
12223 * Trace State Variables::
12224 * Tracepoint Actions::
12225 * Listing Tracepoints::
12226 * Listing Static Tracepoint Markers::
12227 * Starting and Stopping Trace Experiments::
12228 * Tracepoint Restrictions::
12231 @node Create and Delete Tracepoints
12232 @subsection Create and Delete Tracepoints
12235 @cindex set tracepoint
12237 @item trace @var{location}
12238 The @code{trace} command is very similar to the @code{break} command.
12239 Its argument @var{location} can be any valid location.
12240 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12241 which is a point in the target program where the debugger will briefly stop,
12242 collect some data, and then allow the program to continue. Setting a tracepoint
12243 or changing its actions takes effect immediately if the remote stub
12244 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12246 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12247 these changes don't take effect until the next @code{tstart}
12248 command, and once a trace experiment is running, further changes will
12249 not have any effect until the next trace experiment starts. In addition,
12250 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12251 address is not yet resolved. (This is similar to pending breakpoints.)
12252 Pending tracepoints are not downloaded to the target and not installed
12253 until they are resolved. The resolution of pending tracepoints requires
12254 @value{GDBN} support---when debugging with the remote target, and
12255 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12256 tracing}), pending tracepoints can not be resolved (and downloaded to
12257 the remote stub) while @value{GDBN} is disconnected.
12259 Here are some examples of using the @code{trace} command:
12262 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12264 (@value{GDBP}) @b{trace +2} // 2 lines forward
12266 (@value{GDBP}) @b{trace my_function} // first source line of function
12268 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12270 (@value{GDBP}) @b{trace *0x2117c4} // an address
12274 You can abbreviate @code{trace} as @code{tr}.
12276 @item trace @var{location} if @var{cond}
12277 Set a tracepoint with condition @var{cond}; evaluate the expression
12278 @var{cond} each time the tracepoint is reached, and collect data only
12279 if the value is nonzero---that is, if @var{cond} evaluates as true.
12280 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12281 information on tracepoint conditions.
12283 @item ftrace @var{location} [ if @var{cond} ]
12284 @cindex set fast tracepoint
12285 @cindex fast tracepoints, setting
12287 The @code{ftrace} command sets a fast tracepoint. For targets that
12288 support them, fast tracepoints will use a more efficient but possibly
12289 less general technique to trigger data collection, such as a jump
12290 instruction instead of a trap, or some sort of hardware support. It
12291 may not be possible to create a fast tracepoint at the desired
12292 location, in which case the command will exit with an explanatory
12295 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12298 On 32-bit x86-architecture systems, fast tracepoints normally need to
12299 be placed at an instruction that is 5 bytes or longer, but can be
12300 placed at 4-byte instructions if the low 64K of memory of the target
12301 program is available to install trampolines. Some Unix-type systems,
12302 such as @sc{gnu}/Linux, exclude low addresses from the program's
12303 address space; but for instance with the Linux kernel it is possible
12304 to let @value{GDBN} use this area by doing a @command{sysctl} command
12305 to set the @code{mmap_min_addr} kernel parameter, as in
12308 sudo sysctl -w vm.mmap_min_addr=32768
12312 which sets the low address to 32K, which leaves plenty of room for
12313 trampolines. The minimum address should be set to a page boundary.
12315 @item strace @var{location} [ if @var{cond} ]
12316 @cindex set static tracepoint
12317 @cindex static tracepoints, setting
12318 @cindex probe static tracepoint marker
12320 The @code{strace} command sets a static tracepoint. For targets that
12321 support it, setting a static tracepoint probes a static
12322 instrumentation point, or marker, found at @var{location}. It may not
12323 be possible to set a static tracepoint at the desired location, in
12324 which case the command will exit with an explanatory message.
12326 @value{GDBN} handles arguments to @code{strace} exactly as for
12327 @code{trace}, with the addition that the user can also specify
12328 @code{-m @var{marker}} as @var{location}. This probes the marker
12329 identified by the @var{marker} string identifier. This identifier
12330 depends on the static tracepoint backend library your program is
12331 using. You can find all the marker identifiers in the @samp{ID} field
12332 of the @code{info static-tracepoint-markers} command output.
12333 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12334 Markers}. For example, in the following small program using the UST
12340 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12345 the marker id is composed of joining the first two arguments to the
12346 @code{trace_mark} call with a slash, which translates to:
12349 (@value{GDBP}) info static-tracepoint-markers
12350 Cnt Enb ID Address What
12351 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12357 so you may probe the marker above with:
12360 (@value{GDBP}) strace -m ust/bar33
12363 Static tracepoints accept an extra collect action --- @code{collect
12364 $_sdata}. This collects arbitrary user data passed in the probe point
12365 call to the tracing library. In the UST example above, you'll see
12366 that the third argument to @code{trace_mark} is a printf-like format
12367 string. The user data is then the result of running that formating
12368 string against the following arguments. Note that @code{info
12369 static-tracepoint-markers} command output lists that format string in
12370 the @samp{Data:} field.
12372 You can inspect this data when analyzing the trace buffer, by printing
12373 the $_sdata variable like any other variable available to
12374 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12377 @cindex last tracepoint number
12378 @cindex recent tracepoint number
12379 @cindex tracepoint number
12380 The convenience variable @code{$tpnum} records the tracepoint number
12381 of the most recently set tracepoint.
12383 @kindex delete tracepoint
12384 @cindex tracepoint deletion
12385 @item delete tracepoint @r{[}@var{num}@r{]}
12386 Permanently delete one or more tracepoints. With no argument, the
12387 default is to delete all tracepoints. Note that the regular
12388 @code{delete} command can remove tracepoints also.
12393 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12395 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12399 You can abbreviate this command as @code{del tr}.
12402 @node Enable and Disable Tracepoints
12403 @subsection Enable and Disable Tracepoints
12405 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12408 @kindex disable tracepoint
12409 @item disable tracepoint @r{[}@var{num}@r{]}
12410 Disable tracepoint @var{num}, or all tracepoints if no argument
12411 @var{num} is given. A disabled tracepoint will have no effect during
12412 a trace experiment, but it is not forgotten. You can re-enable
12413 a disabled tracepoint using the @code{enable tracepoint} command.
12414 If the command is issued during a trace experiment and the debug target
12415 has support for disabling tracepoints during a trace experiment, then the
12416 change will be effective immediately. Otherwise, it will be applied to the
12417 next trace experiment.
12419 @kindex enable tracepoint
12420 @item enable tracepoint @r{[}@var{num}@r{]}
12421 Enable tracepoint @var{num}, or all tracepoints. If this command is
12422 issued during a trace experiment and the debug target supports enabling
12423 tracepoints during a trace experiment, then the enabled tracepoints will
12424 become effective immediately. Otherwise, they will become effective the
12425 next time a trace experiment is run.
12428 @node Tracepoint Passcounts
12429 @subsection Tracepoint Passcounts
12433 @cindex tracepoint pass count
12434 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12435 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12436 automatically stop a trace experiment. If a tracepoint's passcount is
12437 @var{n}, then the trace experiment will be automatically stopped on
12438 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12439 @var{num} is not specified, the @code{passcount} command sets the
12440 passcount of the most recently defined tracepoint. If no passcount is
12441 given, the trace experiment will run until stopped explicitly by the
12447 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12448 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12450 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12451 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12452 (@value{GDBP}) @b{trace foo}
12453 (@value{GDBP}) @b{pass 3}
12454 (@value{GDBP}) @b{trace bar}
12455 (@value{GDBP}) @b{pass 2}
12456 (@value{GDBP}) @b{trace baz}
12457 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12458 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12459 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12460 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12464 @node Tracepoint Conditions
12465 @subsection Tracepoint Conditions
12466 @cindex conditional tracepoints
12467 @cindex tracepoint conditions
12469 The simplest sort of tracepoint collects data every time your program
12470 reaches a specified place. You can also specify a @dfn{condition} for
12471 a tracepoint. A condition is just a Boolean expression in your
12472 programming language (@pxref{Expressions, ,Expressions}). A
12473 tracepoint with a condition evaluates the expression each time your
12474 program reaches it, and data collection happens only if the condition
12477 Tracepoint conditions can be specified when a tracepoint is set, by
12478 using @samp{if} in the arguments to the @code{trace} command.
12479 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12480 also be set or changed at any time with the @code{condition} command,
12481 just as with breakpoints.
12483 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12484 the conditional expression itself. Instead, @value{GDBN} encodes the
12485 expression into an agent expression (@pxref{Agent Expressions})
12486 suitable for execution on the target, independently of @value{GDBN}.
12487 Global variables become raw memory locations, locals become stack
12488 accesses, and so forth.
12490 For instance, suppose you have a function that is usually called
12491 frequently, but should not be called after an error has occurred. You
12492 could use the following tracepoint command to collect data about calls
12493 of that function that happen while the error code is propagating
12494 through the program; an unconditional tracepoint could end up
12495 collecting thousands of useless trace frames that you would have to
12499 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12502 @node Trace State Variables
12503 @subsection Trace State Variables
12504 @cindex trace state variables
12506 A @dfn{trace state variable} is a special type of variable that is
12507 created and managed by target-side code. The syntax is the same as
12508 that for GDB's convenience variables (a string prefixed with ``$''),
12509 but they are stored on the target. They must be created explicitly,
12510 using a @code{tvariable} command. They are always 64-bit signed
12513 Trace state variables are remembered by @value{GDBN}, and downloaded
12514 to the target along with tracepoint information when the trace
12515 experiment starts. There are no intrinsic limits on the number of
12516 trace state variables, beyond memory limitations of the target.
12518 @cindex convenience variables, and trace state variables
12519 Although trace state variables are managed by the target, you can use
12520 them in print commands and expressions as if they were convenience
12521 variables; @value{GDBN} will get the current value from the target
12522 while the trace experiment is running. Trace state variables share
12523 the same namespace as other ``$'' variables, which means that you
12524 cannot have trace state variables with names like @code{$23} or
12525 @code{$pc}, nor can you have a trace state variable and a convenience
12526 variable with the same name.
12530 @item tvariable $@var{name} [ = @var{expression} ]
12532 The @code{tvariable} command creates a new trace state variable named
12533 @code{$@var{name}}, and optionally gives it an initial value of
12534 @var{expression}. The @var{expression} is evaluated when this command is
12535 entered; the result will be converted to an integer if possible,
12536 otherwise @value{GDBN} will report an error. A subsequent
12537 @code{tvariable} command specifying the same name does not create a
12538 variable, but instead assigns the supplied initial value to the
12539 existing variable of that name, overwriting any previous initial
12540 value. The default initial value is 0.
12542 @item info tvariables
12543 @kindex info tvariables
12544 List all the trace state variables along with their initial values.
12545 Their current values may also be displayed, if the trace experiment is
12548 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12549 @kindex delete tvariable
12550 Delete the given trace state variables, or all of them if no arguments
12555 @node Tracepoint Actions
12556 @subsection Tracepoint Action Lists
12560 @cindex tracepoint actions
12561 @item actions @r{[}@var{num}@r{]}
12562 This command will prompt for a list of actions to be taken when the
12563 tracepoint is hit. If the tracepoint number @var{num} is not
12564 specified, this command sets the actions for the one that was most
12565 recently defined (so that you can define a tracepoint and then say
12566 @code{actions} without bothering about its number). You specify the
12567 actions themselves on the following lines, one action at a time, and
12568 terminate the actions list with a line containing just @code{end}. So
12569 far, the only defined actions are @code{collect}, @code{teval}, and
12570 @code{while-stepping}.
12572 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12573 Commands, ,Breakpoint Command Lists}), except that only the defined
12574 actions are allowed; any other @value{GDBN} command is rejected.
12576 @cindex remove actions from a tracepoint
12577 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12578 and follow it immediately with @samp{end}.
12581 (@value{GDBP}) @b{collect @var{data}} // collect some data
12583 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12585 (@value{GDBP}) @b{end} // signals the end of actions.
12588 In the following example, the action list begins with @code{collect}
12589 commands indicating the things to be collected when the tracepoint is
12590 hit. Then, in order to single-step and collect additional data
12591 following the tracepoint, a @code{while-stepping} command is used,
12592 followed by the list of things to be collected after each step in a
12593 sequence of single steps. The @code{while-stepping} command is
12594 terminated by its own separate @code{end} command. Lastly, the action
12595 list is terminated by an @code{end} command.
12598 (@value{GDBP}) @b{trace foo}
12599 (@value{GDBP}) @b{actions}
12600 Enter actions for tracepoint 1, one per line:
12603 > while-stepping 12
12604 > collect $pc, arr[i]
12609 @kindex collect @r{(tracepoints)}
12610 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12611 Collect values of the given expressions when the tracepoint is hit.
12612 This command accepts a comma-separated list of any valid expressions.
12613 In addition to global, static, or local variables, the following
12614 special arguments are supported:
12618 Collect all registers.
12621 Collect all function arguments.
12624 Collect all local variables.
12627 Collect the return address. This is helpful if you want to see more
12631 Collects the number of arguments from the static probe at which the
12632 tracepoint is located.
12633 @xref{Static Probe Points}.
12635 @item $_probe_arg@var{n}
12636 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12637 from the static probe at which the tracepoint is located.
12638 @xref{Static Probe Points}.
12641 @vindex $_sdata@r{, collect}
12642 Collect static tracepoint marker specific data. Only available for
12643 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12644 Lists}. On the UST static tracepoints library backend, an
12645 instrumentation point resembles a @code{printf} function call. The
12646 tracing library is able to collect user specified data formatted to a
12647 character string using the format provided by the programmer that
12648 instrumented the program. Other backends have similar mechanisms.
12649 Here's an example of a UST marker call:
12652 const char master_name[] = "$your_name";
12653 trace_mark(channel1, marker1, "hello %s", master_name)
12656 In this case, collecting @code{$_sdata} collects the string
12657 @samp{hello $yourname}. When analyzing the trace buffer, you can
12658 inspect @samp{$_sdata} like any other variable available to
12662 You can give several consecutive @code{collect} commands, each one
12663 with a single argument, or one @code{collect} command with several
12664 arguments separated by commas; the effect is the same.
12666 The optional @var{mods} changes the usual handling of the arguments.
12667 @code{s} requests that pointers to chars be handled as strings, in
12668 particular collecting the contents of the memory being pointed at, up
12669 to the first zero. The upper bound is by default the value of the
12670 @code{print elements} variable; if @code{s} is followed by a decimal
12671 number, that is the upper bound instead. So for instance
12672 @samp{collect/s25 mystr} collects as many as 25 characters at
12675 The command @code{info scope} (@pxref{Symbols, info scope}) is
12676 particularly useful for figuring out what data to collect.
12678 @kindex teval @r{(tracepoints)}
12679 @item teval @var{expr1}, @var{expr2}, @dots{}
12680 Evaluate the given expressions when the tracepoint is hit. This
12681 command accepts a comma-separated list of expressions. The results
12682 are discarded, so this is mainly useful for assigning values to trace
12683 state variables (@pxref{Trace State Variables}) without adding those
12684 values to the trace buffer, as would be the case if the @code{collect}
12687 @kindex while-stepping @r{(tracepoints)}
12688 @item while-stepping @var{n}
12689 Perform @var{n} single-step instruction traces after the tracepoint,
12690 collecting new data after each step. The @code{while-stepping}
12691 command is followed by the list of what to collect while stepping
12692 (followed by its own @code{end} command):
12695 > while-stepping 12
12696 > collect $regs, myglobal
12702 Note that @code{$pc} is not automatically collected by
12703 @code{while-stepping}; you need to explicitly collect that register if
12704 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12707 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12708 @kindex set default-collect
12709 @cindex default collection action
12710 This variable is a list of expressions to collect at each tracepoint
12711 hit. It is effectively an additional @code{collect} action prepended
12712 to every tracepoint action list. The expressions are parsed
12713 individually for each tracepoint, so for instance a variable named
12714 @code{xyz} may be interpreted as a global for one tracepoint, and a
12715 local for another, as appropriate to the tracepoint's location.
12717 @item show default-collect
12718 @kindex show default-collect
12719 Show the list of expressions that are collected by default at each
12724 @node Listing Tracepoints
12725 @subsection Listing Tracepoints
12728 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12729 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12730 @cindex information about tracepoints
12731 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12732 Display information about the tracepoint @var{num}. If you don't
12733 specify a tracepoint number, displays information about all the
12734 tracepoints defined so far. The format is similar to that used for
12735 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12736 command, simply restricting itself to tracepoints.
12738 A tracepoint's listing may include additional information specific to
12743 its passcount as given by the @code{passcount @var{n}} command
12746 the state about installed on target of each location
12750 (@value{GDBP}) @b{info trace}
12751 Num Type Disp Enb Address What
12752 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12754 collect globfoo, $regs
12759 2 tracepoint keep y <MULTIPLE>
12761 2.1 y 0x0804859c in func4 at change-loc.h:35
12762 installed on target
12763 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12764 installed on target
12765 2.3 y <PENDING> set_tracepoint
12766 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12767 not installed on target
12772 This command can be abbreviated @code{info tp}.
12775 @node Listing Static Tracepoint Markers
12776 @subsection Listing Static Tracepoint Markers
12779 @kindex info static-tracepoint-markers
12780 @cindex information about static tracepoint markers
12781 @item info static-tracepoint-markers
12782 Display information about all static tracepoint markers defined in the
12785 For each marker, the following columns are printed:
12789 An incrementing counter, output to help readability. This is not a
12792 The marker ID, as reported by the target.
12793 @item Enabled or Disabled
12794 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12795 that are not enabled.
12797 Where the marker is in your program, as a memory address.
12799 Where the marker is in the source for your program, as a file and line
12800 number. If the debug information included in the program does not
12801 allow @value{GDBN} to locate the source of the marker, this column
12802 will be left blank.
12806 In addition, the following information may be printed for each marker:
12810 User data passed to the tracing library by the marker call. In the
12811 UST backend, this is the format string passed as argument to the
12813 @item Static tracepoints probing the marker
12814 The list of static tracepoints attached to the marker.
12818 (@value{GDBP}) info static-tracepoint-markers
12819 Cnt ID Enb Address What
12820 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12821 Data: number1 %d number2 %d
12822 Probed by static tracepoints: #2
12823 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12829 @node Starting and Stopping Trace Experiments
12830 @subsection Starting and Stopping Trace Experiments
12833 @kindex tstart [ @var{notes} ]
12834 @cindex start a new trace experiment
12835 @cindex collected data discarded
12837 This command starts the trace experiment, and begins collecting data.
12838 It has the side effect of discarding all the data collected in the
12839 trace buffer during the previous trace experiment. If any arguments
12840 are supplied, they are taken as a note and stored with the trace
12841 experiment's state. The notes may be arbitrary text, and are
12842 especially useful with disconnected tracing in a multi-user context;
12843 the notes can explain what the trace is doing, supply user contact
12844 information, and so forth.
12846 @kindex tstop [ @var{notes} ]
12847 @cindex stop a running trace experiment
12849 This command stops the trace experiment. If any arguments are
12850 supplied, they are recorded with the experiment as a note. This is
12851 useful if you are stopping a trace started by someone else, for
12852 instance if the trace is interfering with the system's behavior and
12853 needs to be stopped quickly.
12855 @strong{Note}: a trace experiment and data collection may stop
12856 automatically if any tracepoint's passcount is reached
12857 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12860 @cindex status of trace data collection
12861 @cindex trace experiment, status of
12863 This command displays the status of the current trace data
12867 Here is an example of the commands we described so far:
12870 (@value{GDBP}) @b{trace gdb_c_test}
12871 (@value{GDBP}) @b{actions}
12872 Enter actions for tracepoint #1, one per line.
12873 > collect $regs,$locals,$args
12874 > while-stepping 11
12878 (@value{GDBP}) @b{tstart}
12879 [time passes @dots{}]
12880 (@value{GDBP}) @b{tstop}
12883 @anchor{disconnected tracing}
12884 @cindex disconnected tracing
12885 You can choose to continue running the trace experiment even if
12886 @value{GDBN} disconnects from the target, voluntarily or
12887 involuntarily. For commands such as @code{detach}, the debugger will
12888 ask what you want to do with the trace. But for unexpected
12889 terminations (@value{GDBN} crash, network outage), it would be
12890 unfortunate to lose hard-won trace data, so the variable
12891 @code{disconnected-tracing} lets you decide whether the trace should
12892 continue running without @value{GDBN}.
12895 @item set disconnected-tracing on
12896 @itemx set disconnected-tracing off
12897 @kindex set disconnected-tracing
12898 Choose whether a tracing run should continue to run if @value{GDBN}
12899 has disconnected from the target. Note that @code{detach} or
12900 @code{quit} will ask you directly what to do about a running trace no
12901 matter what this variable's setting, so the variable is mainly useful
12902 for handling unexpected situations, such as loss of the network.
12904 @item show disconnected-tracing
12905 @kindex show disconnected-tracing
12906 Show the current choice for disconnected tracing.
12910 When you reconnect to the target, the trace experiment may or may not
12911 still be running; it might have filled the trace buffer in the
12912 meantime, or stopped for one of the other reasons. If it is running,
12913 it will continue after reconnection.
12915 Upon reconnection, the target will upload information about the
12916 tracepoints in effect. @value{GDBN} will then compare that
12917 information to the set of tracepoints currently defined, and attempt
12918 to match them up, allowing for the possibility that the numbers may
12919 have changed due to creation and deletion in the meantime. If one of
12920 the target's tracepoints does not match any in @value{GDBN}, the
12921 debugger will create a new tracepoint, so that you have a number with
12922 which to specify that tracepoint. This matching-up process is
12923 necessarily heuristic, and it may result in useless tracepoints being
12924 created; you may simply delete them if they are of no use.
12926 @cindex circular trace buffer
12927 If your target agent supports a @dfn{circular trace buffer}, then you
12928 can run a trace experiment indefinitely without filling the trace
12929 buffer; when space runs out, the agent deletes already-collected trace
12930 frames, oldest first, until there is enough room to continue
12931 collecting. This is especially useful if your tracepoints are being
12932 hit too often, and your trace gets terminated prematurely because the
12933 buffer is full. To ask for a circular trace buffer, simply set
12934 @samp{circular-trace-buffer} to on. You can set this at any time,
12935 including during tracing; if the agent can do it, it will change
12936 buffer handling on the fly, otherwise it will not take effect until
12940 @item set circular-trace-buffer on
12941 @itemx set circular-trace-buffer off
12942 @kindex set circular-trace-buffer
12943 Choose whether a tracing run should use a linear or circular buffer
12944 for trace data. A linear buffer will not lose any trace data, but may
12945 fill up prematurely, while a circular buffer will discard old trace
12946 data, but it will have always room for the latest tracepoint hits.
12948 @item show circular-trace-buffer
12949 @kindex show circular-trace-buffer
12950 Show the current choice for the trace buffer. Note that this may not
12951 match the agent's current buffer handling, nor is it guaranteed to
12952 match the setting that might have been in effect during a past run,
12953 for instance if you are looking at frames from a trace file.
12958 @item set trace-buffer-size @var{n}
12959 @itemx set trace-buffer-size unlimited
12960 @kindex set trace-buffer-size
12961 Request that the target use a trace buffer of @var{n} bytes. Not all
12962 targets will honor the request; they may have a compiled-in size for
12963 the trace buffer, or some other limitation. Set to a value of
12964 @code{unlimited} or @code{-1} to let the target use whatever size it
12965 likes. This is also the default.
12967 @item show trace-buffer-size
12968 @kindex show trace-buffer-size
12969 Show the current requested size for the trace buffer. Note that this
12970 will only match the actual size if the target supports size-setting,
12971 and was able to handle the requested size. For instance, if the
12972 target can only change buffer size between runs, this variable will
12973 not reflect the change until the next run starts. Use @code{tstatus}
12974 to get a report of the actual buffer size.
12978 @item set trace-user @var{text}
12979 @kindex set trace-user
12981 @item show trace-user
12982 @kindex show trace-user
12984 @item set trace-notes @var{text}
12985 @kindex set trace-notes
12986 Set the trace run's notes.
12988 @item show trace-notes
12989 @kindex show trace-notes
12990 Show the trace run's notes.
12992 @item set trace-stop-notes @var{text}
12993 @kindex set trace-stop-notes
12994 Set the trace run's stop notes. The handling of the note is as for
12995 @code{tstop} arguments; the set command is convenient way to fix a
12996 stop note that is mistaken or incomplete.
12998 @item show trace-stop-notes
12999 @kindex show trace-stop-notes
13000 Show the trace run's stop notes.
13004 @node Tracepoint Restrictions
13005 @subsection Tracepoint Restrictions
13007 @cindex tracepoint restrictions
13008 There are a number of restrictions on the use of tracepoints. As
13009 described above, tracepoint data gathering occurs on the target
13010 without interaction from @value{GDBN}. Thus the full capabilities of
13011 the debugger are not available during data gathering, and then at data
13012 examination time, you will be limited by only having what was
13013 collected. The following items describe some common problems, but it
13014 is not exhaustive, and you may run into additional difficulties not
13020 Tracepoint expressions are intended to gather objects (lvalues). Thus
13021 the full flexibility of GDB's expression evaluator is not available.
13022 You cannot call functions, cast objects to aggregate types, access
13023 convenience variables or modify values (except by assignment to trace
13024 state variables). Some language features may implicitly call
13025 functions (for instance Objective-C fields with accessors), and therefore
13026 cannot be collected either.
13029 Collection of local variables, either individually or in bulk with
13030 @code{$locals} or @code{$args}, during @code{while-stepping} may
13031 behave erratically. The stepping action may enter a new scope (for
13032 instance by stepping into a function), or the location of the variable
13033 may change (for instance it is loaded into a register). The
13034 tracepoint data recorded uses the location information for the
13035 variables that is correct for the tracepoint location. When the
13036 tracepoint is created, it is not possible, in general, to determine
13037 where the steps of a @code{while-stepping} sequence will advance the
13038 program---particularly if a conditional branch is stepped.
13041 Collection of an incompletely-initialized or partially-destroyed object
13042 may result in something that @value{GDBN} cannot display, or displays
13043 in a misleading way.
13046 When @value{GDBN} displays a pointer to character it automatically
13047 dereferences the pointer to also display characters of the string
13048 being pointed to. However, collecting the pointer during tracing does
13049 not automatically collect the string. You need to explicitly
13050 dereference the pointer and provide size information if you want to
13051 collect not only the pointer, but the memory pointed to. For example,
13052 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13056 It is not possible to collect a complete stack backtrace at a
13057 tracepoint. Instead, you may collect the registers and a few hundred
13058 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13059 (adjust to use the name of the actual stack pointer register on your
13060 target architecture, and the amount of stack you wish to capture).
13061 Then the @code{backtrace} command will show a partial backtrace when
13062 using a trace frame. The number of stack frames that can be examined
13063 depends on the sizes of the frames in the collected stack. Note that
13064 if you ask for a block so large that it goes past the bottom of the
13065 stack, the target agent may report an error trying to read from an
13069 If you do not collect registers at a tracepoint, @value{GDBN} can
13070 infer that the value of @code{$pc} must be the same as the address of
13071 the tracepoint and use that when you are looking at a trace frame
13072 for that tracepoint. However, this cannot work if the tracepoint has
13073 multiple locations (for instance if it was set in a function that was
13074 inlined), or if it has a @code{while-stepping} loop. In those cases
13075 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13080 @node Analyze Collected Data
13081 @section Using the Collected Data
13083 After the tracepoint experiment ends, you use @value{GDBN} commands
13084 for examining the trace data. The basic idea is that each tracepoint
13085 collects a trace @dfn{snapshot} every time it is hit and another
13086 snapshot every time it single-steps. All these snapshots are
13087 consecutively numbered from zero and go into a buffer, and you can
13088 examine them later. The way you examine them is to @dfn{focus} on a
13089 specific trace snapshot. When the remote stub is focused on a trace
13090 snapshot, it will respond to all @value{GDBN} requests for memory and
13091 registers by reading from the buffer which belongs to that snapshot,
13092 rather than from @emph{real} memory or registers of the program being
13093 debugged. This means that @strong{all} @value{GDBN} commands
13094 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13095 behave as if we were currently debugging the program state as it was
13096 when the tracepoint occurred. Any requests for data that are not in
13097 the buffer will fail.
13100 * tfind:: How to select a trace snapshot
13101 * tdump:: How to display all data for a snapshot
13102 * save tracepoints:: How to save tracepoints for a future run
13106 @subsection @code{tfind @var{n}}
13109 @cindex select trace snapshot
13110 @cindex find trace snapshot
13111 The basic command for selecting a trace snapshot from the buffer is
13112 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13113 counting from zero. If no argument @var{n} is given, the next
13114 snapshot is selected.
13116 Here are the various forms of using the @code{tfind} command.
13120 Find the first snapshot in the buffer. This is a synonym for
13121 @code{tfind 0} (since 0 is the number of the first snapshot).
13124 Stop debugging trace snapshots, resume @emph{live} debugging.
13127 Same as @samp{tfind none}.
13130 No argument means find the next trace snapshot.
13133 Find the previous trace snapshot before the current one. This permits
13134 retracing earlier steps.
13136 @item tfind tracepoint @var{num}
13137 Find the next snapshot associated with tracepoint @var{num}. Search
13138 proceeds forward from the last examined trace snapshot. If no
13139 argument @var{num} is given, it means find the next snapshot collected
13140 for the same tracepoint as the current snapshot.
13142 @item tfind pc @var{addr}
13143 Find the next snapshot associated with the value @var{addr} of the
13144 program counter. Search proceeds forward from the last examined trace
13145 snapshot. If no argument @var{addr} is given, it means find the next
13146 snapshot with the same value of PC as the current snapshot.
13148 @item tfind outside @var{addr1}, @var{addr2}
13149 Find the next snapshot whose PC is outside the given range of
13150 addresses (exclusive).
13152 @item tfind range @var{addr1}, @var{addr2}
13153 Find the next snapshot whose PC is between @var{addr1} and
13154 @var{addr2} (inclusive).
13156 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13157 Find the next snapshot associated with the source line @var{n}. If
13158 the optional argument @var{file} is given, refer to line @var{n} in
13159 that source file. Search proceeds forward from the last examined
13160 trace snapshot. If no argument @var{n} is given, it means find the
13161 next line other than the one currently being examined; thus saying
13162 @code{tfind line} repeatedly can appear to have the same effect as
13163 stepping from line to line in a @emph{live} debugging session.
13166 The default arguments for the @code{tfind} commands are specifically
13167 designed to make it easy to scan through the trace buffer. For
13168 instance, @code{tfind} with no argument selects the next trace
13169 snapshot, and @code{tfind -} with no argument selects the previous
13170 trace snapshot. So, by giving one @code{tfind} command, and then
13171 simply hitting @key{RET} repeatedly you can examine all the trace
13172 snapshots in order. Or, by saying @code{tfind -} and then hitting
13173 @key{RET} repeatedly you can examine the snapshots in reverse order.
13174 The @code{tfind line} command with no argument selects the snapshot
13175 for the next source line executed. The @code{tfind pc} command with
13176 no argument selects the next snapshot with the same program counter
13177 (PC) as the current frame. The @code{tfind tracepoint} command with
13178 no argument selects the next trace snapshot collected by the same
13179 tracepoint as the current one.
13181 In addition to letting you scan through the trace buffer manually,
13182 these commands make it easy to construct @value{GDBN} scripts that
13183 scan through the trace buffer and print out whatever collected data
13184 you are interested in. Thus, if we want to examine the PC, FP, and SP
13185 registers from each trace frame in the buffer, we can say this:
13188 (@value{GDBP}) @b{tfind start}
13189 (@value{GDBP}) @b{while ($trace_frame != -1)}
13190 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13191 $trace_frame, $pc, $sp, $fp
13195 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13196 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13197 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13198 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13199 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13200 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13201 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13202 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13203 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13204 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13205 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13208 Or, if we want to examine the variable @code{X} at each source line in
13212 (@value{GDBP}) @b{tfind start}
13213 (@value{GDBP}) @b{while ($trace_frame != -1)}
13214 > printf "Frame %d, X == %d\n", $trace_frame, X
13224 @subsection @code{tdump}
13226 @cindex dump all data collected at tracepoint
13227 @cindex tracepoint data, display
13229 This command takes no arguments. It prints all the data collected at
13230 the current trace snapshot.
13233 (@value{GDBP}) @b{trace 444}
13234 (@value{GDBP}) @b{actions}
13235 Enter actions for tracepoint #2, one per line:
13236 > collect $regs, $locals, $args, gdb_long_test
13239 (@value{GDBP}) @b{tstart}
13241 (@value{GDBP}) @b{tfind line 444}
13242 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13244 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13246 (@value{GDBP}) @b{tdump}
13247 Data collected at tracepoint 2, trace frame 1:
13248 d0 0xc4aa0085 -995491707
13252 d4 0x71aea3d 119204413
13255 d7 0x380035 3670069
13256 a0 0x19e24a 1696330
13257 a1 0x3000668 50333288
13259 a3 0x322000 3284992
13260 a4 0x3000698 50333336
13261 a5 0x1ad3cc 1758156
13262 fp 0x30bf3c 0x30bf3c
13263 sp 0x30bf34 0x30bf34
13265 pc 0x20b2c8 0x20b2c8
13269 p = 0x20e5b4 "gdb-test"
13276 gdb_long_test = 17 '\021'
13281 @code{tdump} works by scanning the tracepoint's current collection
13282 actions and printing the value of each expression listed. So
13283 @code{tdump} can fail, if after a run, you change the tracepoint's
13284 actions to mention variables that were not collected during the run.
13286 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13287 uses the collected value of @code{$pc} to distinguish between trace
13288 frames that were collected at the tracepoint hit, and frames that were
13289 collected while stepping. This allows it to correctly choose whether
13290 to display the basic list of collections, or the collections from the
13291 body of the while-stepping loop. However, if @code{$pc} was not collected,
13292 then @code{tdump} will always attempt to dump using the basic collection
13293 list, and may fail if a while-stepping frame does not include all the
13294 same data that is collected at the tracepoint hit.
13295 @c This is getting pretty arcane, example would be good.
13297 @node save tracepoints
13298 @subsection @code{save tracepoints @var{filename}}
13299 @kindex save tracepoints
13300 @kindex save-tracepoints
13301 @cindex save tracepoints for future sessions
13303 This command saves all current tracepoint definitions together with
13304 their actions and passcounts, into a file @file{@var{filename}}
13305 suitable for use in a later debugging session. To read the saved
13306 tracepoint definitions, use the @code{source} command (@pxref{Command
13307 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13308 alias for @w{@code{save tracepoints}}
13310 @node Tracepoint Variables
13311 @section Convenience Variables for Tracepoints
13312 @cindex tracepoint variables
13313 @cindex convenience variables for tracepoints
13316 @vindex $trace_frame
13317 @item (int) $trace_frame
13318 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13319 snapshot is selected.
13321 @vindex $tracepoint
13322 @item (int) $tracepoint
13323 The tracepoint for the current trace snapshot.
13325 @vindex $trace_line
13326 @item (int) $trace_line
13327 The line number for the current trace snapshot.
13329 @vindex $trace_file
13330 @item (char []) $trace_file
13331 The source file for the current trace snapshot.
13333 @vindex $trace_func
13334 @item (char []) $trace_func
13335 The name of the function containing @code{$tracepoint}.
13338 Note: @code{$trace_file} is not suitable for use in @code{printf},
13339 use @code{output} instead.
13341 Here's a simple example of using these convenience variables for
13342 stepping through all the trace snapshots and printing some of their
13343 data. Note that these are not the same as trace state variables,
13344 which are managed by the target.
13347 (@value{GDBP}) @b{tfind start}
13349 (@value{GDBP}) @b{while $trace_frame != -1}
13350 > output $trace_file
13351 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13357 @section Using Trace Files
13358 @cindex trace files
13360 In some situations, the target running a trace experiment may no
13361 longer be available; perhaps it crashed, or the hardware was needed
13362 for a different activity. To handle these cases, you can arrange to
13363 dump the trace data into a file, and later use that file as a source
13364 of trace data, via the @code{target tfile} command.
13369 @item tsave [ -r ] @var{filename}
13370 @itemx tsave [-ctf] @var{dirname}
13371 Save the trace data to @var{filename}. By default, this command
13372 assumes that @var{filename} refers to the host filesystem, so if
13373 necessary @value{GDBN} will copy raw trace data up from the target and
13374 then save it. If the target supports it, you can also supply the
13375 optional argument @code{-r} (``remote'') to direct the target to save
13376 the data directly into @var{filename} in its own filesystem, which may be
13377 more efficient if the trace buffer is very large. (Note, however, that
13378 @code{target tfile} can only read from files accessible to the host.)
13379 By default, this command will save trace frame in tfile format.
13380 You can supply the optional argument @code{-ctf} to save date in CTF
13381 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13382 that can be shared by multiple debugging and tracing tools. Please go to
13383 @indicateurl{http://www.efficios.com/ctf} to get more information.
13385 @kindex target tfile
13389 @item target tfile @var{filename}
13390 @itemx target ctf @var{dirname}
13391 Use the file named @var{filename} or directory named @var{dirname} as
13392 a source of trace data. Commands that examine data work as they do with
13393 a live target, but it is not possible to run any new trace experiments.
13394 @code{tstatus} will report the state of the trace run at the moment
13395 the data was saved, as well as the current trace frame you are examining.
13396 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13400 (@value{GDBP}) target ctf ctf.ctf
13401 (@value{GDBP}) tfind
13402 Found trace frame 0, tracepoint 2
13403 39 ++a; /* set tracepoint 1 here */
13404 (@value{GDBP}) tdump
13405 Data collected at tracepoint 2, trace frame 0:
13409 c = @{"123", "456", "789", "123", "456", "789"@}
13410 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13418 @chapter Debugging Programs That Use Overlays
13421 If your program is too large to fit completely in your target system's
13422 memory, you can sometimes use @dfn{overlays} to work around this
13423 problem. @value{GDBN} provides some support for debugging programs that
13427 * How Overlays Work:: A general explanation of overlays.
13428 * Overlay Commands:: Managing overlays in @value{GDBN}.
13429 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13430 mapped by asking the inferior.
13431 * Overlay Sample Program:: A sample program using overlays.
13434 @node How Overlays Work
13435 @section How Overlays Work
13436 @cindex mapped overlays
13437 @cindex unmapped overlays
13438 @cindex load address, overlay's
13439 @cindex mapped address
13440 @cindex overlay area
13442 Suppose you have a computer whose instruction address space is only 64
13443 kilobytes long, but which has much more memory which can be accessed by
13444 other means: special instructions, segment registers, or memory
13445 management hardware, for example. Suppose further that you want to
13446 adapt a program which is larger than 64 kilobytes to run on this system.
13448 One solution is to identify modules of your program which are relatively
13449 independent, and need not call each other directly; call these modules
13450 @dfn{overlays}. Separate the overlays from the main program, and place
13451 their machine code in the larger memory. Place your main program in
13452 instruction memory, but leave at least enough space there to hold the
13453 largest overlay as well.
13455 Now, to call a function located in an overlay, you must first copy that
13456 overlay's machine code from the large memory into the space set aside
13457 for it in the instruction memory, and then jump to its entry point
13460 @c NB: In the below the mapped area's size is greater or equal to the
13461 @c size of all overlays. This is intentional to remind the developer
13462 @c that overlays don't necessarily need to be the same size.
13466 Data Instruction Larger
13467 Address Space Address Space Address Space
13468 +-----------+ +-----------+ +-----------+
13470 +-----------+ +-----------+ +-----------+<-- overlay 1
13471 | program | | main | .----| overlay 1 | load address
13472 | variables | | program | | +-----------+
13473 | and heap | | | | | |
13474 +-----------+ | | | +-----------+<-- overlay 2
13475 | | +-----------+ | | | load address
13476 +-----------+ | | | .-| overlay 2 |
13478 mapped --->+-----------+ | | +-----------+
13479 address | | | | | |
13480 | overlay | <-' | | |
13481 | area | <---' +-----------+<-- overlay 3
13482 | | <---. | | load address
13483 +-----------+ `--| overlay 3 |
13490 @anchor{A code overlay}A code overlay
13494 The diagram (@pxref{A code overlay}) shows a system with separate data
13495 and instruction address spaces. To map an overlay, the program copies
13496 its code from the larger address space to the instruction address space.
13497 Since the overlays shown here all use the same mapped address, only one
13498 may be mapped at a time. For a system with a single address space for
13499 data and instructions, the diagram would be similar, except that the
13500 program variables and heap would share an address space with the main
13501 program and the overlay area.
13503 An overlay loaded into instruction memory and ready for use is called a
13504 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13505 instruction memory. An overlay not present (or only partially present)
13506 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13507 is its address in the larger memory. The mapped address is also called
13508 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13509 called the @dfn{load memory address}, or @dfn{LMA}.
13511 Unfortunately, overlays are not a completely transparent way to adapt a
13512 program to limited instruction memory. They introduce a new set of
13513 global constraints you must keep in mind as you design your program:
13518 Before calling or returning to a function in an overlay, your program
13519 must make sure that overlay is actually mapped. Otherwise, the call or
13520 return will transfer control to the right address, but in the wrong
13521 overlay, and your program will probably crash.
13524 If the process of mapping an overlay is expensive on your system, you
13525 will need to choose your overlays carefully to minimize their effect on
13526 your program's performance.
13529 The executable file you load onto your system must contain each
13530 overlay's instructions, appearing at the overlay's load address, not its
13531 mapped address. However, each overlay's instructions must be relocated
13532 and its symbols defined as if the overlay were at its mapped address.
13533 You can use GNU linker scripts to specify different load and relocation
13534 addresses for pieces of your program; see @ref{Overlay Description,,,
13535 ld.info, Using ld: the GNU linker}.
13538 The procedure for loading executable files onto your system must be able
13539 to load their contents into the larger address space as well as the
13540 instruction and data spaces.
13544 The overlay system described above is rather simple, and could be
13545 improved in many ways:
13550 If your system has suitable bank switch registers or memory management
13551 hardware, you could use those facilities to make an overlay's load area
13552 contents simply appear at their mapped address in instruction space.
13553 This would probably be faster than copying the overlay to its mapped
13554 area in the usual way.
13557 If your overlays are small enough, you could set aside more than one
13558 overlay area, and have more than one overlay mapped at a time.
13561 You can use overlays to manage data, as well as instructions. In
13562 general, data overlays are even less transparent to your design than
13563 code overlays: whereas code overlays only require care when you call or
13564 return to functions, data overlays require care every time you access
13565 the data. Also, if you change the contents of a data overlay, you
13566 must copy its contents back out to its load address before you can copy a
13567 different data overlay into the same mapped area.
13572 @node Overlay Commands
13573 @section Overlay Commands
13575 To use @value{GDBN}'s overlay support, each overlay in your program must
13576 correspond to a separate section of the executable file. The section's
13577 virtual memory address and load memory address must be the overlay's
13578 mapped and load addresses. Identifying overlays with sections allows
13579 @value{GDBN} to determine the appropriate address of a function or
13580 variable, depending on whether the overlay is mapped or not.
13582 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13583 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13588 Disable @value{GDBN}'s overlay support. When overlay support is
13589 disabled, @value{GDBN} assumes that all functions and variables are
13590 always present at their mapped addresses. By default, @value{GDBN}'s
13591 overlay support is disabled.
13593 @item overlay manual
13594 @cindex manual overlay debugging
13595 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13596 relies on you to tell it which overlays are mapped, and which are not,
13597 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13598 commands described below.
13600 @item overlay map-overlay @var{overlay}
13601 @itemx overlay map @var{overlay}
13602 @cindex map an overlay
13603 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13604 be the name of the object file section containing the overlay. When an
13605 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13606 functions and variables at their mapped addresses. @value{GDBN} assumes
13607 that any other overlays whose mapped ranges overlap that of
13608 @var{overlay} are now unmapped.
13610 @item overlay unmap-overlay @var{overlay}
13611 @itemx overlay unmap @var{overlay}
13612 @cindex unmap an overlay
13613 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13614 must be the name of the object file section containing the overlay.
13615 When an overlay is unmapped, @value{GDBN} assumes it can find the
13616 overlay's functions and variables at their load addresses.
13619 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13620 consults a data structure the overlay manager maintains in the inferior
13621 to see which overlays are mapped. For details, see @ref{Automatic
13622 Overlay Debugging}.
13624 @item overlay load-target
13625 @itemx overlay load
13626 @cindex reloading the overlay table
13627 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13628 re-reads the table @value{GDBN} automatically each time the inferior
13629 stops, so this command should only be necessary if you have changed the
13630 overlay mapping yourself using @value{GDBN}. This command is only
13631 useful when using automatic overlay debugging.
13633 @item overlay list-overlays
13634 @itemx overlay list
13635 @cindex listing mapped overlays
13636 Display a list of the overlays currently mapped, along with their mapped
13637 addresses, load addresses, and sizes.
13641 Normally, when @value{GDBN} prints a code address, it includes the name
13642 of the function the address falls in:
13645 (@value{GDBP}) print main
13646 $3 = @{int ()@} 0x11a0 <main>
13649 When overlay debugging is enabled, @value{GDBN} recognizes code in
13650 unmapped overlays, and prints the names of unmapped functions with
13651 asterisks around them. For example, if @code{foo} is a function in an
13652 unmapped overlay, @value{GDBN} prints it this way:
13655 (@value{GDBP}) overlay list
13656 No sections are mapped.
13657 (@value{GDBP}) print foo
13658 $5 = @{int (int)@} 0x100000 <*foo*>
13661 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13665 (@value{GDBP}) overlay list
13666 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13667 mapped at 0x1016 - 0x104a
13668 (@value{GDBP}) print foo
13669 $6 = @{int (int)@} 0x1016 <foo>
13672 When overlay debugging is enabled, @value{GDBN} can find the correct
13673 address for functions and variables in an overlay, whether or not the
13674 overlay is mapped. This allows most @value{GDBN} commands, like
13675 @code{break} and @code{disassemble}, to work normally, even on unmapped
13676 code. However, @value{GDBN}'s breakpoint support has some limitations:
13680 @cindex breakpoints in overlays
13681 @cindex overlays, setting breakpoints in
13682 You can set breakpoints in functions in unmapped overlays, as long as
13683 @value{GDBN} can write to the overlay at its load address.
13685 @value{GDBN} can not set hardware or simulator-based breakpoints in
13686 unmapped overlays. However, if you set a breakpoint at the end of your
13687 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13688 you are using manual overlay management), @value{GDBN} will re-set its
13689 breakpoints properly.
13693 @node Automatic Overlay Debugging
13694 @section Automatic Overlay Debugging
13695 @cindex automatic overlay debugging
13697 @value{GDBN} can automatically track which overlays are mapped and which
13698 are not, given some simple co-operation from the overlay manager in the
13699 inferior. If you enable automatic overlay debugging with the
13700 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13701 looks in the inferior's memory for certain variables describing the
13702 current state of the overlays.
13704 Here are the variables your overlay manager must define to support
13705 @value{GDBN}'s automatic overlay debugging:
13709 @item @code{_ovly_table}:
13710 This variable must be an array of the following structures:
13715 /* The overlay's mapped address. */
13718 /* The size of the overlay, in bytes. */
13719 unsigned long size;
13721 /* The overlay's load address. */
13724 /* Non-zero if the overlay is currently mapped;
13726 unsigned long mapped;
13730 @item @code{_novlys}:
13731 This variable must be a four-byte signed integer, holding the total
13732 number of elements in @code{_ovly_table}.
13736 To decide whether a particular overlay is mapped or not, @value{GDBN}
13737 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13738 @code{lma} members equal the VMA and LMA of the overlay's section in the
13739 executable file. When @value{GDBN} finds a matching entry, it consults
13740 the entry's @code{mapped} member to determine whether the overlay is
13743 In addition, your overlay manager may define a function called
13744 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13745 will silently set a breakpoint there. If the overlay manager then
13746 calls this function whenever it has changed the overlay table, this
13747 will enable @value{GDBN} to accurately keep track of which overlays
13748 are in program memory, and update any breakpoints that may be set
13749 in overlays. This will allow breakpoints to work even if the
13750 overlays are kept in ROM or other non-writable memory while they
13751 are not being executed.
13753 @node Overlay Sample Program
13754 @section Overlay Sample Program
13755 @cindex overlay example program
13757 When linking a program which uses overlays, you must place the overlays
13758 at their load addresses, while relocating them to run at their mapped
13759 addresses. To do this, you must write a linker script (@pxref{Overlay
13760 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13761 since linker scripts are specific to a particular host system, target
13762 architecture, and target memory layout, this manual cannot provide
13763 portable sample code demonstrating @value{GDBN}'s overlay support.
13765 However, the @value{GDBN} source distribution does contain an overlaid
13766 program, with linker scripts for a few systems, as part of its test
13767 suite. The program consists of the following files from
13768 @file{gdb/testsuite/gdb.base}:
13772 The main program file.
13774 A simple overlay manager, used by @file{overlays.c}.
13779 Overlay modules, loaded and used by @file{overlays.c}.
13782 Linker scripts for linking the test program on the @code{d10v-elf}
13783 and @code{m32r-elf} targets.
13786 You can build the test program using the @code{d10v-elf} GCC
13787 cross-compiler like this:
13790 $ d10v-elf-gcc -g -c overlays.c
13791 $ d10v-elf-gcc -g -c ovlymgr.c
13792 $ d10v-elf-gcc -g -c foo.c
13793 $ d10v-elf-gcc -g -c bar.c
13794 $ d10v-elf-gcc -g -c baz.c
13795 $ d10v-elf-gcc -g -c grbx.c
13796 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13797 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13800 The build process is identical for any other architecture, except that
13801 you must substitute the appropriate compiler and linker script for the
13802 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13806 @chapter Using @value{GDBN} with Different Languages
13809 Although programming languages generally have common aspects, they are
13810 rarely expressed in the same manner. For instance, in ANSI C,
13811 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13812 Modula-2, it is accomplished by @code{p^}. Values can also be
13813 represented (and displayed) differently. Hex numbers in C appear as
13814 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13816 @cindex working language
13817 Language-specific information is built into @value{GDBN} for some languages,
13818 allowing you to express operations like the above in your program's
13819 native language, and allowing @value{GDBN} to output values in a manner
13820 consistent with the syntax of your program's native language. The
13821 language you use to build expressions is called the @dfn{working
13825 * Setting:: Switching between source languages
13826 * Show:: Displaying the language
13827 * Checks:: Type and range checks
13828 * Supported Languages:: Supported languages
13829 * Unsupported Languages:: Unsupported languages
13833 @section Switching Between Source Languages
13835 There are two ways to control the working language---either have @value{GDBN}
13836 set it automatically, or select it manually yourself. You can use the
13837 @code{set language} command for either purpose. On startup, @value{GDBN}
13838 defaults to setting the language automatically. The working language is
13839 used to determine how expressions you type are interpreted, how values
13842 In addition to the working language, every source file that
13843 @value{GDBN} knows about has its own working language. For some object
13844 file formats, the compiler might indicate which language a particular
13845 source file is in. However, most of the time @value{GDBN} infers the
13846 language from the name of the file. The language of a source file
13847 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13848 show each frame appropriately for its own language. There is no way to
13849 set the language of a source file from within @value{GDBN}, but you can
13850 set the language associated with a filename extension. @xref{Show, ,
13851 Displaying the Language}.
13853 This is most commonly a problem when you use a program, such
13854 as @code{cfront} or @code{f2c}, that generates C but is written in
13855 another language. In that case, make the
13856 program use @code{#line} directives in its C output; that way
13857 @value{GDBN} will know the correct language of the source code of the original
13858 program, and will display that source code, not the generated C code.
13861 * Filenames:: Filename extensions and languages.
13862 * Manually:: Setting the working language manually
13863 * Automatically:: Having @value{GDBN} infer the source language
13867 @subsection List of Filename Extensions and Languages
13869 If a source file name ends in one of the following extensions, then
13870 @value{GDBN} infers that its language is the one indicated.
13888 C@t{++} source file
13894 Objective-C source file
13898 Fortran source file
13901 Modula-2 source file
13905 Assembler source file. This actually behaves almost like C, but
13906 @value{GDBN} does not skip over function prologues when stepping.
13909 In addition, you may set the language associated with a filename
13910 extension. @xref{Show, , Displaying the Language}.
13913 @subsection Setting the Working Language
13915 If you allow @value{GDBN} to set the language automatically,
13916 expressions are interpreted the same way in your debugging session and
13919 @kindex set language
13920 If you wish, you may set the language manually. To do this, issue the
13921 command @samp{set language @var{lang}}, where @var{lang} is the name of
13922 a language, such as
13923 @code{c} or @code{modula-2}.
13924 For a list of the supported languages, type @samp{set language}.
13926 Setting the language manually prevents @value{GDBN} from updating the working
13927 language automatically. This can lead to confusion if you try
13928 to debug a program when the working language is not the same as the
13929 source language, when an expression is acceptable to both
13930 languages---but means different things. For instance, if the current
13931 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13939 might not have the effect you intended. In C, this means to add
13940 @code{b} and @code{c} and place the result in @code{a}. The result
13941 printed would be the value of @code{a}. In Modula-2, this means to compare
13942 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13944 @node Automatically
13945 @subsection Having @value{GDBN} Infer the Source Language
13947 To have @value{GDBN} set the working language automatically, use
13948 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13949 then infers the working language. That is, when your program stops in a
13950 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13951 working language to the language recorded for the function in that
13952 frame. If the language for a frame is unknown (that is, if the function
13953 or block corresponding to the frame was defined in a source file that
13954 does not have a recognized extension), the current working language is
13955 not changed, and @value{GDBN} issues a warning.
13957 This may not seem necessary for most programs, which are written
13958 entirely in one source language. However, program modules and libraries
13959 written in one source language can be used by a main program written in
13960 a different source language. Using @samp{set language auto} in this
13961 case frees you from having to set the working language manually.
13964 @section Displaying the Language
13966 The following commands help you find out which language is the
13967 working language, and also what language source files were written in.
13970 @item show language
13971 @anchor{show language}
13972 @kindex show language
13973 Display the current working language. This is the
13974 language you can use with commands such as @code{print} to
13975 build and compute expressions that may involve variables in your program.
13978 @kindex info frame@r{, show the source language}
13979 Display the source language for this frame. This language becomes the
13980 working language if you use an identifier from this frame.
13981 @xref{Frame Info, ,Information about a Frame}, to identify the other
13982 information listed here.
13985 @kindex info source@r{, show the source language}
13986 Display the source language of this source file.
13987 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13988 information listed here.
13991 In unusual circumstances, you may have source files with extensions
13992 not in the standard list. You can then set the extension associated
13993 with a language explicitly:
13996 @item set extension-language @var{ext} @var{language}
13997 @kindex set extension-language
13998 Tell @value{GDBN} that source files with extension @var{ext} are to be
13999 assumed as written in the source language @var{language}.
14001 @item info extensions
14002 @kindex info extensions
14003 List all the filename extensions and the associated languages.
14007 @section Type and Range Checking
14009 Some languages are designed to guard you against making seemingly common
14010 errors through a series of compile- and run-time checks. These include
14011 checking the type of arguments to functions and operators and making
14012 sure mathematical overflows are caught at run time. Checks such as
14013 these help to ensure a program's correctness once it has been compiled
14014 by eliminating type mismatches and providing active checks for range
14015 errors when your program is running.
14017 By default @value{GDBN} checks for these errors according to the
14018 rules of the current source language. Although @value{GDBN} does not check
14019 the statements in your program, it can check expressions entered directly
14020 into @value{GDBN} for evaluation via the @code{print} command, for example.
14023 * Type Checking:: An overview of type checking
14024 * Range Checking:: An overview of range checking
14027 @cindex type checking
14028 @cindex checks, type
14029 @node Type Checking
14030 @subsection An Overview of Type Checking
14032 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14033 arguments to operators and functions have to be of the correct type,
14034 otherwise an error occurs. These checks prevent type mismatch
14035 errors from ever causing any run-time problems. For example,
14038 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14040 (@value{GDBP}) print obj.my_method (0)
14043 (@value{GDBP}) print obj.my_method (0x1234)
14044 Cannot resolve method klass::my_method to any overloaded instance
14047 The second example fails because in C@t{++} the integer constant
14048 @samp{0x1234} is not type-compatible with the pointer parameter type.
14050 For the expressions you use in @value{GDBN} commands, you can tell
14051 @value{GDBN} to not enforce strict type checking or
14052 to treat any mismatches as errors and abandon the expression;
14053 When type checking is disabled, @value{GDBN} successfully evaluates
14054 expressions like the second example above.
14056 Even if type checking is off, there may be other reasons
14057 related to type that prevent @value{GDBN} from evaluating an expression.
14058 For instance, @value{GDBN} does not know how to add an @code{int} and
14059 a @code{struct foo}. These particular type errors have nothing to do
14060 with the language in use and usually arise from expressions which make
14061 little sense to evaluate anyway.
14063 @value{GDBN} provides some additional commands for controlling type checking:
14065 @kindex set check type
14066 @kindex show check type
14068 @item set check type on
14069 @itemx set check type off
14070 Set strict type checking on or off. If any type mismatches occur in
14071 evaluating an expression while type checking is on, @value{GDBN} prints a
14072 message and aborts evaluation of the expression.
14074 @item show check type
14075 Show the current setting of type checking and whether @value{GDBN}
14076 is enforcing strict type checking rules.
14079 @cindex range checking
14080 @cindex checks, range
14081 @node Range Checking
14082 @subsection An Overview of Range Checking
14084 In some languages (such as Modula-2), it is an error to exceed the
14085 bounds of a type; this is enforced with run-time checks. Such range
14086 checking is meant to ensure program correctness by making sure
14087 computations do not overflow, or indices on an array element access do
14088 not exceed the bounds of the array.
14090 For expressions you use in @value{GDBN} commands, you can tell
14091 @value{GDBN} to treat range errors in one of three ways: ignore them,
14092 always treat them as errors and abandon the expression, or issue
14093 warnings but evaluate the expression anyway.
14095 A range error can result from numerical overflow, from exceeding an
14096 array index bound, or when you type a constant that is not a member
14097 of any type. Some languages, however, do not treat overflows as an
14098 error. In many implementations of C, mathematical overflow causes the
14099 result to ``wrap around'' to lower values---for example, if @var{m} is
14100 the largest integer value, and @var{s} is the smallest, then
14103 @var{m} + 1 @result{} @var{s}
14106 This, too, is specific to individual languages, and in some cases
14107 specific to individual compilers or machines. @xref{Supported Languages, ,
14108 Supported Languages}, for further details on specific languages.
14110 @value{GDBN} provides some additional commands for controlling the range checker:
14112 @kindex set check range
14113 @kindex show check range
14115 @item set check range auto
14116 Set range checking on or off based on the current working language.
14117 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14120 @item set check range on
14121 @itemx set check range off
14122 Set range checking on or off, overriding the default setting for the
14123 current working language. A warning is issued if the setting does not
14124 match the language default. If a range error occurs and range checking is on,
14125 then a message is printed and evaluation of the expression is aborted.
14127 @item set check range warn
14128 Output messages when the @value{GDBN} range checker detects a range error,
14129 but attempt to evaluate the expression anyway. Evaluating the
14130 expression may still be impossible for other reasons, such as accessing
14131 memory that the process does not own (a typical example from many Unix
14135 Show the current setting of the range checker, and whether or not it is
14136 being set automatically by @value{GDBN}.
14139 @node Supported Languages
14140 @section Supported Languages
14142 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
14143 OpenCL C, Pascal, assembly, Modula-2, and Ada.
14144 @c This is false ...
14145 Some @value{GDBN} features may be used in expressions regardless of the
14146 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14147 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14148 ,Expressions}) can be used with the constructs of any supported
14151 The following sections detail to what degree each source language is
14152 supported by @value{GDBN}. These sections are not meant to be language
14153 tutorials or references, but serve only as a reference guide to what the
14154 @value{GDBN} expression parser accepts, and what input and output
14155 formats should look like for different languages. There are many good
14156 books written on each of these languages; please look to these for a
14157 language reference or tutorial.
14160 * C:: C and C@t{++}
14163 * Objective-C:: Objective-C
14164 * OpenCL C:: OpenCL C
14165 * Fortran:: Fortran
14167 * Modula-2:: Modula-2
14172 @subsection C and C@t{++}
14174 @cindex C and C@t{++}
14175 @cindex expressions in C or C@t{++}
14177 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14178 to both languages. Whenever this is the case, we discuss those languages
14182 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14183 @cindex @sc{gnu} C@t{++}
14184 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14185 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14186 effectively, you must compile your C@t{++} programs with a supported
14187 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14188 compiler (@code{aCC}).
14191 * C Operators:: C and C@t{++} operators
14192 * C Constants:: C and C@t{++} constants
14193 * C Plus Plus Expressions:: C@t{++} expressions
14194 * C Defaults:: Default settings for C and C@t{++}
14195 * C Checks:: C and C@t{++} type and range checks
14196 * Debugging C:: @value{GDBN} and C
14197 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14198 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14202 @subsubsection C and C@t{++} Operators
14204 @cindex C and C@t{++} operators
14206 Operators must be defined on values of specific types. For instance,
14207 @code{+} is defined on numbers, but not on structures. Operators are
14208 often defined on groups of types.
14210 For the purposes of C and C@t{++}, the following definitions hold:
14215 @emph{Integral types} include @code{int} with any of its storage-class
14216 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14219 @emph{Floating-point types} include @code{float}, @code{double}, and
14220 @code{long double} (if supported by the target platform).
14223 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14226 @emph{Scalar types} include all of the above.
14231 The following operators are supported. They are listed here
14232 in order of increasing precedence:
14236 The comma or sequencing operator. Expressions in a comma-separated list
14237 are evaluated from left to right, with the result of the entire
14238 expression being the last expression evaluated.
14241 Assignment. The value of an assignment expression is the value
14242 assigned. Defined on scalar types.
14245 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14246 and translated to @w{@code{@var{a} = @var{a op b}}}.
14247 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14248 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14249 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14252 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14253 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14254 should be of an integral type.
14257 Logical @sc{or}. Defined on integral types.
14260 Logical @sc{and}. Defined on integral types.
14263 Bitwise @sc{or}. Defined on integral types.
14266 Bitwise exclusive-@sc{or}. Defined on integral types.
14269 Bitwise @sc{and}. Defined on integral types.
14272 Equality and inequality. Defined on scalar types. The value of these
14273 expressions is 0 for false and non-zero for true.
14275 @item <@r{, }>@r{, }<=@r{, }>=
14276 Less than, greater than, less than or equal, greater than or equal.
14277 Defined on scalar types. The value of these expressions is 0 for false
14278 and non-zero for true.
14281 left shift, and right shift. Defined on integral types.
14284 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14287 Addition and subtraction. Defined on integral types, floating-point types and
14290 @item *@r{, }/@r{, }%
14291 Multiplication, division, and modulus. Multiplication and division are
14292 defined on integral and floating-point types. Modulus is defined on
14296 Increment and decrement. When appearing before a variable, the
14297 operation is performed before the variable is used in an expression;
14298 when appearing after it, the variable's value is used before the
14299 operation takes place.
14302 Pointer dereferencing. Defined on pointer types. Same precedence as
14306 Address operator. Defined on variables. Same precedence as @code{++}.
14308 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14309 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14310 to examine the address
14311 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14315 Negative. Defined on integral and floating-point types. Same
14316 precedence as @code{++}.
14319 Logical negation. Defined on integral types. Same precedence as
14323 Bitwise complement operator. Defined on integral types. Same precedence as
14328 Structure member, and pointer-to-structure member. For convenience,
14329 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14330 pointer based on the stored type information.
14331 Defined on @code{struct} and @code{union} data.
14334 Dereferences of pointers to members.
14337 Array indexing. @code{@var{a}[@var{i}]} is defined as
14338 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14341 Function parameter list. Same precedence as @code{->}.
14344 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14345 and @code{class} types.
14348 Doubled colons also represent the @value{GDBN} scope operator
14349 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14353 If an operator is redefined in the user code, @value{GDBN} usually
14354 attempts to invoke the redefined version instead of using the operator's
14355 predefined meaning.
14358 @subsubsection C and C@t{++} Constants
14360 @cindex C and C@t{++} constants
14362 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14367 Integer constants are a sequence of digits. Octal constants are
14368 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14369 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14370 @samp{l}, specifying that the constant should be treated as a
14374 Floating point constants are a sequence of digits, followed by a decimal
14375 point, followed by a sequence of digits, and optionally followed by an
14376 exponent. An exponent is of the form:
14377 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14378 sequence of digits. The @samp{+} is optional for positive exponents.
14379 A floating-point constant may also end with a letter @samp{f} or
14380 @samp{F}, specifying that the constant should be treated as being of
14381 the @code{float} (as opposed to the default @code{double}) type; or with
14382 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14386 Enumerated constants consist of enumerated identifiers, or their
14387 integral equivalents.
14390 Character constants are a single character surrounded by single quotes
14391 (@code{'}), or a number---the ordinal value of the corresponding character
14392 (usually its @sc{ascii} value). Within quotes, the single character may
14393 be represented by a letter or by @dfn{escape sequences}, which are of
14394 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14395 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14396 @samp{@var{x}} is a predefined special character---for example,
14397 @samp{\n} for newline.
14399 Wide character constants can be written by prefixing a character
14400 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14401 form of @samp{x}. The target wide character set is used when
14402 computing the value of this constant (@pxref{Character Sets}).
14405 String constants are a sequence of character constants surrounded by
14406 double quotes (@code{"}). Any valid character constant (as described
14407 above) may appear. Double quotes within the string must be preceded by
14408 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14411 Wide string constants can be written by prefixing a string constant
14412 with @samp{L}, as in C. The target wide character set is used when
14413 computing the value of this constant (@pxref{Character Sets}).
14416 Pointer constants are an integral value. You can also write pointers
14417 to constants using the C operator @samp{&}.
14420 Array constants are comma-separated lists surrounded by braces @samp{@{}
14421 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14422 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14423 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14426 @node C Plus Plus Expressions
14427 @subsubsection C@t{++} Expressions
14429 @cindex expressions in C@t{++}
14430 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14432 @cindex debugging C@t{++} programs
14433 @cindex C@t{++} compilers
14434 @cindex debug formats and C@t{++}
14435 @cindex @value{NGCC} and C@t{++}
14437 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14438 the proper compiler and the proper debug format. Currently,
14439 @value{GDBN} works best when debugging C@t{++} code that is compiled
14440 with the most recent version of @value{NGCC} possible. The DWARF
14441 debugging format is preferred; @value{NGCC} defaults to this on most
14442 popular platforms. Other compilers and/or debug formats are likely to
14443 work badly or not at all when using @value{GDBN} to debug C@t{++}
14444 code. @xref{Compilation}.
14449 @cindex member functions
14451 Member function calls are allowed; you can use expressions like
14454 count = aml->GetOriginal(x, y)
14457 @vindex this@r{, inside C@t{++} member functions}
14458 @cindex namespace in C@t{++}
14460 While a member function is active (in the selected stack frame), your
14461 expressions have the same namespace available as the member function;
14462 that is, @value{GDBN} allows implicit references to the class instance
14463 pointer @code{this} following the same rules as C@t{++}. @code{using}
14464 declarations in the current scope are also respected by @value{GDBN}.
14466 @cindex call overloaded functions
14467 @cindex overloaded functions, calling
14468 @cindex type conversions in C@t{++}
14470 You can call overloaded functions; @value{GDBN} resolves the function
14471 call to the right definition, with some restrictions. @value{GDBN} does not
14472 perform overload resolution involving user-defined type conversions,
14473 calls to constructors, or instantiations of templates that do not exist
14474 in the program. It also cannot handle ellipsis argument lists or
14477 It does perform integral conversions and promotions, floating-point
14478 promotions, arithmetic conversions, pointer conversions, conversions of
14479 class objects to base classes, and standard conversions such as those of
14480 functions or arrays to pointers; it requires an exact match on the
14481 number of function arguments.
14483 Overload resolution is always performed, unless you have specified
14484 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14485 ,@value{GDBN} Features for C@t{++}}.
14487 You must specify @code{set overload-resolution off} in order to use an
14488 explicit function signature to call an overloaded function, as in
14490 p 'foo(char,int)'('x', 13)
14493 The @value{GDBN} command-completion facility can simplify this;
14494 see @ref{Completion, ,Command Completion}.
14496 @cindex reference declarations
14498 @value{GDBN} understands variables declared as C@t{++} references; you can use
14499 them in expressions just as you do in C@t{++} source---they are automatically
14502 In the parameter list shown when @value{GDBN} displays a frame, the values of
14503 reference variables are not displayed (unlike other variables); this
14504 avoids clutter, since references are often used for large structures.
14505 The @emph{address} of a reference variable is always shown, unless
14506 you have specified @samp{set print address off}.
14509 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14510 expressions can use it just as expressions in your program do. Since
14511 one scope may be defined in another, you can use @code{::} repeatedly if
14512 necessary, for example in an expression like
14513 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14514 resolving name scope by reference to source files, in both C and C@t{++}
14515 debugging (@pxref{Variables, ,Program Variables}).
14518 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14523 @subsubsection C and C@t{++} Defaults
14525 @cindex C and C@t{++} defaults
14527 If you allow @value{GDBN} to set range checking automatically, it
14528 defaults to @code{off} whenever the working language changes to
14529 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14530 selects the working language.
14532 If you allow @value{GDBN} to set the language automatically, it
14533 recognizes source files whose names end with @file{.c}, @file{.C}, or
14534 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14535 these files, it sets the working language to C or C@t{++}.
14536 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14537 for further details.
14540 @subsubsection C and C@t{++} Type and Range Checks
14542 @cindex C and C@t{++} checks
14544 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14545 checking is used. However, if you turn type checking off, @value{GDBN}
14546 will allow certain non-standard conversions, such as promoting integer
14547 constants to pointers.
14549 Range checking, if turned on, is done on mathematical operations. Array
14550 indices are not checked, since they are often used to index a pointer
14551 that is not itself an array.
14554 @subsubsection @value{GDBN} and C
14556 The @code{set print union} and @code{show print union} commands apply to
14557 the @code{union} type. When set to @samp{on}, any @code{union} that is
14558 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14559 appears as @samp{@{...@}}.
14561 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14562 with pointers and a memory allocation function. @xref{Expressions,
14565 @node Debugging C Plus Plus
14566 @subsubsection @value{GDBN} Features for C@t{++}
14568 @cindex commands for C@t{++}
14570 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14571 designed specifically for use with C@t{++}. Here is a summary:
14574 @cindex break in overloaded functions
14575 @item @r{breakpoint menus}
14576 When you want a breakpoint in a function whose name is overloaded,
14577 @value{GDBN} has the capability to display a menu of possible breakpoint
14578 locations to help you specify which function definition you want.
14579 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14581 @cindex overloading in C@t{++}
14582 @item rbreak @var{regex}
14583 Setting breakpoints using regular expressions is helpful for setting
14584 breakpoints on overloaded functions that are not members of any special
14586 @xref{Set Breaks, ,Setting Breakpoints}.
14588 @cindex C@t{++} exception handling
14590 @itemx catch rethrow
14592 Debug C@t{++} exception handling using these commands. @xref{Set
14593 Catchpoints, , Setting Catchpoints}.
14595 @cindex inheritance
14596 @item ptype @var{typename}
14597 Print inheritance relationships as well as other information for type
14599 @xref{Symbols, ,Examining the Symbol Table}.
14601 @item info vtbl @var{expression}.
14602 The @code{info vtbl} command can be used to display the virtual
14603 method tables of the object computed by @var{expression}. This shows
14604 one entry per virtual table; there may be multiple virtual tables when
14605 multiple inheritance is in use.
14607 @cindex C@t{++} demangling
14608 @item demangle @var{name}
14609 Demangle @var{name}.
14610 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14612 @cindex C@t{++} symbol display
14613 @item set print demangle
14614 @itemx show print demangle
14615 @itemx set print asm-demangle
14616 @itemx show print asm-demangle
14617 Control whether C@t{++} symbols display in their source form, both when
14618 displaying code as C@t{++} source and when displaying disassemblies.
14619 @xref{Print Settings, ,Print Settings}.
14621 @item set print object
14622 @itemx show print object
14623 Choose whether to print derived (actual) or declared types of objects.
14624 @xref{Print Settings, ,Print Settings}.
14626 @item set print vtbl
14627 @itemx show print vtbl
14628 Control the format for printing virtual function tables.
14629 @xref{Print Settings, ,Print Settings}.
14630 (The @code{vtbl} commands do not work on programs compiled with the HP
14631 ANSI C@t{++} compiler (@code{aCC}).)
14633 @kindex set overload-resolution
14634 @cindex overloaded functions, overload resolution
14635 @item set overload-resolution on
14636 Enable overload resolution for C@t{++} expression evaluation. The default
14637 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14638 and searches for a function whose signature matches the argument types,
14639 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14640 Expressions, ,C@t{++} Expressions}, for details).
14641 If it cannot find a match, it emits a message.
14643 @item set overload-resolution off
14644 Disable overload resolution for C@t{++} expression evaluation. For
14645 overloaded functions that are not class member functions, @value{GDBN}
14646 chooses the first function of the specified name that it finds in the
14647 symbol table, whether or not its arguments are of the correct type. For
14648 overloaded functions that are class member functions, @value{GDBN}
14649 searches for a function whose signature @emph{exactly} matches the
14652 @kindex show overload-resolution
14653 @item show overload-resolution
14654 Show the current setting of overload resolution.
14656 @item @r{Overloaded symbol names}
14657 You can specify a particular definition of an overloaded symbol, using
14658 the same notation that is used to declare such symbols in C@t{++}: type
14659 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14660 also use the @value{GDBN} command-line word completion facilities to list the
14661 available choices, or to finish the type list for you.
14662 @xref{Completion,, Command Completion}, for details on how to do this.
14665 @node Decimal Floating Point
14666 @subsubsection Decimal Floating Point format
14667 @cindex decimal floating point format
14669 @value{GDBN} can examine, set and perform computations with numbers in
14670 decimal floating point format, which in the C language correspond to the
14671 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14672 specified by the extension to support decimal floating-point arithmetic.
14674 There are two encodings in use, depending on the architecture: BID (Binary
14675 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14676 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14679 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14680 to manipulate decimal floating point numbers, it is not possible to convert
14681 (using a cast, for example) integers wider than 32-bit to decimal float.
14683 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14684 point computations, error checking in decimal float operations ignores
14685 underflow, overflow and divide by zero exceptions.
14687 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14688 to inspect @code{_Decimal128} values stored in floating point registers.
14689 See @ref{PowerPC,,PowerPC} for more details.
14695 @value{GDBN} can be used to debug programs written in D and compiled with
14696 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14697 specific feature --- dynamic arrays.
14702 @cindex Go (programming language)
14703 @value{GDBN} can be used to debug programs written in Go and compiled with
14704 @file{gccgo} or @file{6g} compilers.
14706 Here is a summary of the Go-specific features and restrictions:
14709 @cindex current Go package
14710 @item The current Go package
14711 The name of the current package does not need to be specified when
14712 specifying global variables and functions.
14714 For example, given the program:
14718 var myglob = "Shall we?"
14724 When stopped inside @code{main} either of these work:
14728 (gdb) p main.myglob
14731 @cindex builtin Go types
14732 @item Builtin Go types
14733 The @code{string} type is recognized by @value{GDBN} and is printed
14736 @cindex builtin Go functions
14737 @item Builtin Go functions
14738 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14739 function and handles it internally.
14741 @cindex restrictions on Go expressions
14742 @item Restrictions on Go expressions
14743 All Go operators are supported except @code{&^}.
14744 The Go @code{_} ``blank identifier'' is not supported.
14745 Automatic dereferencing of pointers is not supported.
14749 @subsection Objective-C
14751 @cindex Objective-C
14752 This section provides information about some commands and command
14753 options that are useful for debugging Objective-C code. See also
14754 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14755 few more commands specific to Objective-C support.
14758 * Method Names in Commands::
14759 * The Print Command with Objective-C::
14762 @node Method Names in Commands
14763 @subsubsection Method Names in Commands
14765 The following commands have been extended to accept Objective-C method
14766 names as line specifications:
14768 @kindex clear@r{, and Objective-C}
14769 @kindex break@r{, and Objective-C}
14770 @kindex info line@r{, and Objective-C}
14771 @kindex jump@r{, and Objective-C}
14772 @kindex list@r{, and Objective-C}
14776 @item @code{info line}
14781 A fully qualified Objective-C method name is specified as
14784 -[@var{Class} @var{methodName}]
14787 where the minus sign is used to indicate an instance method and a
14788 plus sign (not shown) is used to indicate a class method. The class
14789 name @var{Class} and method name @var{methodName} are enclosed in
14790 brackets, similar to the way messages are specified in Objective-C
14791 source code. For example, to set a breakpoint at the @code{create}
14792 instance method of class @code{Fruit} in the program currently being
14796 break -[Fruit create]
14799 To list ten program lines around the @code{initialize} class method,
14803 list +[NSText initialize]
14806 In the current version of @value{GDBN}, the plus or minus sign is
14807 required. In future versions of @value{GDBN}, the plus or minus
14808 sign will be optional, but you can use it to narrow the search. It
14809 is also possible to specify just a method name:
14815 You must specify the complete method name, including any colons. If
14816 your program's source files contain more than one @code{create} method,
14817 you'll be presented with a numbered list of classes that implement that
14818 method. Indicate your choice by number, or type @samp{0} to exit if
14821 As another example, to clear a breakpoint established at the
14822 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14825 clear -[NSWindow makeKeyAndOrderFront:]
14828 @node The Print Command with Objective-C
14829 @subsubsection The Print Command With Objective-C
14830 @cindex Objective-C, print objects
14831 @kindex print-object
14832 @kindex po @r{(@code{print-object})}
14834 The print command has also been extended to accept methods. For example:
14837 print -[@var{object} hash]
14840 @cindex print an Objective-C object description
14841 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14843 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14844 and print the result. Also, an additional command has been added,
14845 @code{print-object} or @code{po} for short, which is meant to print
14846 the description of an object. However, this command may only work
14847 with certain Objective-C libraries that have a particular hook
14848 function, @code{_NSPrintForDebugger}, defined.
14851 @subsection OpenCL C
14854 This section provides information about @value{GDBN}s OpenCL C support.
14857 * OpenCL C Datatypes::
14858 * OpenCL C Expressions::
14859 * OpenCL C Operators::
14862 @node OpenCL C Datatypes
14863 @subsubsection OpenCL C Datatypes
14865 @cindex OpenCL C Datatypes
14866 @value{GDBN} supports the builtin scalar and vector datatypes specified
14867 by OpenCL 1.1. In addition the half- and double-precision floating point
14868 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14869 extensions are also known to @value{GDBN}.
14871 @node OpenCL C Expressions
14872 @subsubsection OpenCL C Expressions
14874 @cindex OpenCL C Expressions
14875 @value{GDBN} supports accesses to vector components including the access as
14876 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14877 supported by @value{GDBN} can be used as well.
14879 @node OpenCL C Operators
14880 @subsubsection OpenCL C Operators
14882 @cindex OpenCL C Operators
14883 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14887 @subsection Fortran
14888 @cindex Fortran-specific support in @value{GDBN}
14890 @value{GDBN} can be used to debug programs written in Fortran, but it
14891 currently supports only the features of Fortran 77 language.
14893 @cindex trailing underscore, in Fortran symbols
14894 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14895 among them) append an underscore to the names of variables and
14896 functions. When you debug programs compiled by those compilers, you
14897 will need to refer to variables and functions with a trailing
14901 * Fortran Operators:: Fortran operators and expressions
14902 * Fortran Defaults:: Default settings for Fortran
14903 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14906 @node Fortran Operators
14907 @subsubsection Fortran Operators and Expressions
14909 @cindex Fortran operators and expressions
14911 Operators must be defined on values of specific types. For instance,
14912 @code{+} is defined on numbers, but not on characters or other non-
14913 arithmetic types. Operators are often defined on groups of types.
14917 The exponentiation operator. It raises the first operand to the power
14921 The range operator. Normally used in the form of array(low:high) to
14922 represent a section of array.
14925 The access component operator. Normally used to access elements in derived
14926 types. Also suitable for unions. As unions aren't part of regular Fortran,
14927 this can only happen when accessing a register that uses a gdbarch-defined
14931 @node Fortran Defaults
14932 @subsubsection Fortran Defaults
14934 @cindex Fortran Defaults
14936 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14937 default uses case-insensitive matches for Fortran symbols. You can
14938 change that with the @samp{set case-insensitive} command, see
14939 @ref{Symbols}, for the details.
14941 @node Special Fortran Commands
14942 @subsubsection Special Fortran Commands
14944 @cindex Special Fortran commands
14946 @value{GDBN} has some commands to support Fortran-specific features,
14947 such as displaying common blocks.
14950 @cindex @code{COMMON} blocks, Fortran
14951 @kindex info common
14952 @item info common @r{[}@var{common-name}@r{]}
14953 This command prints the values contained in the Fortran @code{COMMON}
14954 block whose name is @var{common-name}. With no argument, the names of
14955 all @code{COMMON} blocks visible at the current program location are
14962 @cindex Pascal support in @value{GDBN}, limitations
14963 Debugging Pascal programs which use sets, subranges, file variables, or
14964 nested functions does not currently work. @value{GDBN} does not support
14965 entering expressions, printing values, or similar features using Pascal
14968 The Pascal-specific command @code{set print pascal_static-members}
14969 controls whether static members of Pascal objects are displayed.
14970 @xref{Print Settings, pascal_static-members}.
14973 @subsection Modula-2
14975 @cindex Modula-2, @value{GDBN} support
14977 The extensions made to @value{GDBN} to support Modula-2 only support
14978 output from the @sc{gnu} Modula-2 compiler (which is currently being
14979 developed). Other Modula-2 compilers are not currently supported, and
14980 attempting to debug executables produced by them is most likely
14981 to give an error as @value{GDBN} reads in the executable's symbol
14984 @cindex expressions in Modula-2
14986 * M2 Operators:: Built-in operators
14987 * Built-In Func/Proc:: Built-in functions and procedures
14988 * M2 Constants:: Modula-2 constants
14989 * M2 Types:: Modula-2 types
14990 * M2 Defaults:: Default settings for Modula-2
14991 * Deviations:: Deviations from standard Modula-2
14992 * M2 Checks:: Modula-2 type and range checks
14993 * M2 Scope:: The scope operators @code{::} and @code{.}
14994 * GDB/M2:: @value{GDBN} and Modula-2
14998 @subsubsection Operators
14999 @cindex Modula-2 operators
15001 Operators must be defined on values of specific types. For instance,
15002 @code{+} is defined on numbers, but not on structures. Operators are
15003 often defined on groups of types. For the purposes of Modula-2, the
15004 following definitions hold:
15009 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15013 @emph{Character types} consist of @code{CHAR} and its subranges.
15016 @emph{Floating-point types} consist of @code{REAL}.
15019 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15023 @emph{Scalar types} consist of all of the above.
15026 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15029 @emph{Boolean types} consist of @code{BOOLEAN}.
15033 The following operators are supported, and appear in order of
15034 increasing precedence:
15038 Function argument or array index separator.
15041 Assignment. The value of @var{var} @code{:=} @var{value} is
15045 Less than, greater than on integral, floating-point, or enumerated
15049 Less than or equal to, greater than or equal to
15050 on integral, floating-point and enumerated types, or set inclusion on
15051 set types. Same precedence as @code{<}.
15053 @item =@r{, }<>@r{, }#
15054 Equality and two ways of expressing inequality, valid on scalar types.
15055 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15056 available for inequality, since @code{#} conflicts with the script
15060 Set membership. Defined on set types and the types of their members.
15061 Same precedence as @code{<}.
15064 Boolean disjunction. Defined on boolean types.
15067 Boolean conjunction. Defined on boolean types.
15070 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15073 Addition and subtraction on integral and floating-point types, or union
15074 and difference on set types.
15077 Multiplication on integral and floating-point types, or set intersection
15081 Division on floating-point types, or symmetric set difference on set
15082 types. Same precedence as @code{*}.
15085 Integer division and remainder. Defined on integral types. Same
15086 precedence as @code{*}.
15089 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15092 Pointer dereferencing. Defined on pointer types.
15095 Boolean negation. Defined on boolean types. Same precedence as
15099 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15100 precedence as @code{^}.
15103 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15106 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15110 @value{GDBN} and Modula-2 scope operators.
15114 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15115 treats the use of the operator @code{IN}, or the use of operators
15116 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15117 @code{<=}, and @code{>=} on sets as an error.
15121 @node Built-In Func/Proc
15122 @subsubsection Built-in Functions and Procedures
15123 @cindex Modula-2 built-ins
15125 Modula-2 also makes available several built-in procedures and functions.
15126 In describing these, the following metavariables are used:
15131 represents an @code{ARRAY} variable.
15134 represents a @code{CHAR} constant or variable.
15137 represents a variable or constant of integral type.
15140 represents an identifier that belongs to a set. Generally used in the
15141 same function with the metavariable @var{s}. The type of @var{s} should
15142 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15145 represents a variable or constant of integral or floating-point type.
15148 represents a variable or constant of floating-point type.
15154 represents a variable.
15157 represents a variable or constant of one of many types. See the
15158 explanation of the function for details.
15161 All Modula-2 built-in procedures also return a result, described below.
15165 Returns the absolute value of @var{n}.
15168 If @var{c} is a lower case letter, it returns its upper case
15169 equivalent, otherwise it returns its argument.
15172 Returns the character whose ordinal value is @var{i}.
15175 Decrements the value in the variable @var{v} by one. Returns the new value.
15177 @item DEC(@var{v},@var{i})
15178 Decrements the value in the variable @var{v} by @var{i}. Returns the
15181 @item EXCL(@var{m},@var{s})
15182 Removes the element @var{m} from the set @var{s}. Returns the new
15185 @item FLOAT(@var{i})
15186 Returns the floating point equivalent of the integer @var{i}.
15188 @item HIGH(@var{a})
15189 Returns the index of the last member of @var{a}.
15192 Increments the value in the variable @var{v} by one. Returns the new value.
15194 @item INC(@var{v},@var{i})
15195 Increments the value in the variable @var{v} by @var{i}. Returns the
15198 @item INCL(@var{m},@var{s})
15199 Adds the element @var{m} to the set @var{s} if it is not already
15200 there. Returns the new set.
15203 Returns the maximum value of the type @var{t}.
15206 Returns the minimum value of the type @var{t}.
15209 Returns boolean TRUE if @var{i} is an odd number.
15212 Returns the ordinal value of its argument. For example, the ordinal
15213 value of a character is its @sc{ascii} value (on machines supporting
15214 the @sc{ascii} character set). The argument @var{x} must be of an
15215 ordered type, which include integral, character and enumerated types.
15217 @item SIZE(@var{x})
15218 Returns the size of its argument. The argument @var{x} can be a
15219 variable or a type.
15221 @item TRUNC(@var{r})
15222 Returns the integral part of @var{r}.
15224 @item TSIZE(@var{x})
15225 Returns the size of its argument. The argument @var{x} can be a
15226 variable or a type.
15228 @item VAL(@var{t},@var{i})
15229 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15233 @emph{Warning:} Sets and their operations are not yet supported, so
15234 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15238 @cindex Modula-2 constants
15240 @subsubsection Constants
15242 @value{GDBN} allows you to express the constants of Modula-2 in the following
15248 Integer constants are simply a sequence of digits. When used in an
15249 expression, a constant is interpreted to be type-compatible with the
15250 rest of the expression. Hexadecimal integers are specified by a
15251 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15254 Floating point constants appear as a sequence of digits, followed by a
15255 decimal point and another sequence of digits. An optional exponent can
15256 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15257 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15258 digits of the floating point constant must be valid decimal (base 10)
15262 Character constants consist of a single character enclosed by a pair of
15263 like quotes, either single (@code{'}) or double (@code{"}). They may
15264 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15265 followed by a @samp{C}.
15268 String constants consist of a sequence of characters enclosed by a
15269 pair of like quotes, either single (@code{'}) or double (@code{"}).
15270 Escape sequences in the style of C are also allowed. @xref{C
15271 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15275 Enumerated constants consist of an enumerated identifier.
15278 Boolean constants consist of the identifiers @code{TRUE} and
15282 Pointer constants consist of integral values only.
15285 Set constants are not yet supported.
15289 @subsubsection Modula-2 Types
15290 @cindex Modula-2 types
15292 Currently @value{GDBN} can print the following data types in Modula-2
15293 syntax: array types, record types, set types, pointer types, procedure
15294 types, enumerated types, subrange types and base types. You can also
15295 print the contents of variables declared using these type.
15296 This section gives a number of simple source code examples together with
15297 sample @value{GDBN} sessions.
15299 The first example contains the following section of code:
15308 and you can request @value{GDBN} to interrogate the type and value of
15309 @code{r} and @code{s}.
15312 (@value{GDBP}) print s
15314 (@value{GDBP}) ptype s
15316 (@value{GDBP}) print r
15318 (@value{GDBP}) ptype r
15323 Likewise if your source code declares @code{s} as:
15327 s: SET ['A'..'Z'] ;
15331 then you may query the type of @code{s} by:
15334 (@value{GDBP}) ptype s
15335 type = SET ['A'..'Z']
15339 Note that at present you cannot interactively manipulate set
15340 expressions using the debugger.
15342 The following example shows how you might declare an array in Modula-2
15343 and how you can interact with @value{GDBN} to print its type and contents:
15347 s: ARRAY [-10..10] OF CHAR ;
15351 (@value{GDBP}) ptype s
15352 ARRAY [-10..10] OF CHAR
15355 Note that the array handling is not yet complete and although the type
15356 is printed correctly, expression handling still assumes that all
15357 arrays have a lower bound of zero and not @code{-10} as in the example
15360 Here are some more type related Modula-2 examples:
15364 colour = (blue, red, yellow, green) ;
15365 t = [blue..yellow] ;
15373 The @value{GDBN} interaction shows how you can query the data type
15374 and value of a variable.
15377 (@value{GDBP}) print s
15379 (@value{GDBP}) ptype t
15380 type = [blue..yellow]
15384 In this example a Modula-2 array is declared and its contents
15385 displayed. Observe that the contents are written in the same way as
15386 their @code{C} counterparts.
15390 s: ARRAY [1..5] OF CARDINAL ;
15396 (@value{GDBP}) print s
15397 $1 = @{1, 0, 0, 0, 0@}
15398 (@value{GDBP}) ptype s
15399 type = ARRAY [1..5] OF CARDINAL
15402 The Modula-2 language interface to @value{GDBN} also understands
15403 pointer types as shown in this example:
15407 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15414 and you can request that @value{GDBN} describes the type of @code{s}.
15417 (@value{GDBP}) ptype s
15418 type = POINTER TO ARRAY [1..5] OF CARDINAL
15421 @value{GDBN} handles compound types as we can see in this example.
15422 Here we combine array types, record types, pointer types and subrange
15433 myarray = ARRAY myrange OF CARDINAL ;
15434 myrange = [-2..2] ;
15436 s: POINTER TO ARRAY myrange OF foo ;
15440 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15444 (@value{GDBP}) ptype s
15445 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15448 f3 : ARRAY [-2..2] OF CARDINAL;
15453 @subsubsection Modula-2 Defaults
15454 @cindex Modula-2 defaults
15456 If type and range checking are set automatically by @value{GDBN}, they
15457 both default to @code{on} whenever the working language changes to
15458 Modula-2. This happens regardless of whether you or @value{GDBN}
15459 selected the working language.
15461 If you allow @value{GDBN} to set the language automatically, then entering
15462 code compiled from a file whose name ends with @file{.mod} sets the
15463 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15464 Infer the Source Language}, for further details.
15467 @subsubsection Deviations from Standard Modula-2
15468 @cindex Modula-2, deviations from
15470 A few changes have been made to make Modula-2 programs easier to debug.
15471 This is done primarily via loosening its type strictness:
15475 Unlike in standard Modula-2, pointer constants can be formed by
15476 integers. This allows you to modify pointer variables during
15477 debugging. (In standard Modula-2, the actual address contained in a
15478 pointer variable is hidden from you; it can only be modified
15479 through direct assignment to another pointer variable or expression that
15480 returned a pointer.)
15483 C escape sequences can be used in strings and characters to represent
15484 non-printable characters. @value{GDBN} prints out strings with these
15485 escape sequences embedded. Single non-printable characters are
15486 printed using the @samp{CHR(@var{nnn})} format.
15489 The assignment operator (@code{:=}) returns the value of its right-hand
15493 All built-in procedures both modify @emph{and} return their argument.
15497 @subsubsection Modula-2 Type and Range Checks
15498 @cindex Modula-2 checks
15501 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15504 @c FIXME remove warning when type/range checks added
15506 @value{GDBN} considers two Modula-2 variables type equivalent if:
15510 They are of types that have been declared equivalent via a @code{TYPE
15511 @var{t1} = @var{t2}} statement
15514 They have been declared on the same line. (Note: This is true of the
15515 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15518 As long as type checking is enabled, any attempt to combine variables
15519 whose types are not equivalent is an error.
15521 Range checking is done on all mathematical operations, assignment, array
15522 index bounds, and all built-in functions and procedures.
15525 @subsubsection The Scope Operators @code{::} and @code{.}
15527 @cindex @code{.}, Modula-2 scope operator
15528 @cindex colon, doubled as scope operator
15530 @vindex colon-colon@r{, in Modula-2}
15531 @c Info cannot handle :: but TeX can.
15534 @vindex ::@r{, in Modula-2}
15537 There are a few subtle differences between the Modula-2 scope operator
15538 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15543 @var{module} . @var{id}
15544 @var{scope} :: @var{id}
15548 where @var{scope} is the name of a module or a procedure,
15549 @var{module} the name of a module, and @var{id} is any declared
15550 identifier within your program, except another module.
15552 Using the @code{::} operator makes @value{GDBN} search the scope
15553 specified by @var{scope} for the identifier @var{id}. If it is not
15554 found in the specified scope, then @value{GDBN} searches all scopes
15555 enclosing the one specified by @var{scope}.
15557 Using the @code{.} operator makes @value{GDBN} search the current scope for
15558 the identifier specified by @var{id} that was imported from the
15559 definition module specified by @var{module}. With this operator, it is
15560 an error if the identifier @var{id} was not imported from definition
15561 module @var{module}, or if @var{id} is not an identifier in
15565 @subsubsection @value{GDBN} and Modula-2
15567 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15568 Five subcommands of @code{set print} and @code{show print} apply
15569 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15570 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15571 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15572 analogue in Modula-2.
15574 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15575 with any language, is not useful with Modula-2. Its
15576 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15577 created in Modula-2 as they can in C or C@t{++}. However, because an
15578 address can be specified by an integral constant, the construct
15579 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15581 @cindex @code{#} in Modula-2
15582 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15583 interpreted as the beginning of a comment. Use @code{<>} instead.
15589 The extensions made to @value{GDBN} for Ada only support
15590 output from the @sc{gnu} Ada (GNAT) compiler.
15591 Other Ada compilers are not currently supported, and
15592 attempting to debug executables produced by them is most likely
15596 @cindex expressions in Ada
15598 * Ada Mode Intro:: General remarks on the Ada syntax
15599 and semantics supported by Ada mode
15601 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15602 * Additions to Ada:: Extensions of the Ada expression syntax.
15603 * Stopping Before Main Program:: Debugging the program during elaboration.
15604 * Ada Exceptions:: Ada Exceptions
15605 * Ada Tasks:: Listing and setting breakpoints in tasks.
15606 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15607 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15609 * Ada Glitches:: Known peculiarities of Ada mode.
15612 @node Ada Mode Intro
15613 @subsubsection Introduction
15614 @cindex Ada mode, general
15616 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15617 syntax, with some extensions.
15618 The philosophy behind the design of this subset is
15622 That @value{GDBN} should provide basic literals and access to operations for
15623 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15624 leaving more sophisticated computations to subprograms written into the
15625 program (which therefore may be called from @value{GDBN}).
15628 That type safety and strict adherence to Ada language restrictions
15629 are not particularly important to the @value{GDBN} user.
15632 That brevity is important to the @value{GDBN} user.
15635 Thus, for brevity, the debugger acts as if all names declared in
15636 user-written packages are directly visible, even if they are not visible
15637 according to Ada rules, thus making it unnecessary to fully qualify most
15638 names with their packages, regardless of context. Where this causes
15639 ambiguity, @value{GDBN} asks the user's intent.
15641 The debugger will start in Ada mode if it detects an Ada main program.
15642 As for other languages, it will enter Ada mode when stopped in a program that
15643 was translated from an Ada source file.
15645 While in Ada mode, you may use `@t{--}' for comments. This is useful
15646 mostly for documenting command files. The standard @value{GDBN} comment
15647 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15648 middle (to allow based literals).
15650 The debugger supports limited overloading. Given a subprogram call in which
15651 the function symbol has multiple definitions, it will use the number of
15652 actual parameters and some information about their types to attempt to narrow
15653 the set of definitions. It also makes very limited use of context, preferring
15654 procedures to functions in the context of the @code{call} command, and
15655 functions to procedures elsewhere.
15657 @node Omissions from Ada
15658 @subsubsection Omissions from Ada
15659 @cindex Ada, omissions from
15661 Here are the notable omissions from the subset:
15665 Only a subset of the attributes are supported:
15669 @t{'First}, @t{'Last}, and @t{'Length}
15670 on array objects (not on types and subtypes).
15673 @t{'Min} and @t{'Max}.
15676 @t{'Pos} and @t{'Val}.
15682 @t{'Range} on array objects (not subtypes), but only as the right
15683 operand of the membership (@code{in}) operator.
15686 @t{'Access}, @t{'Unchecked_Access}, and
15687 @t{'Unrestricted_Access} (a GNAT extension).
15695 @code{Characters.Latin_1} are not available and
15696 concatenation is not implemented. Thus, escape characters in strings are
15697 not currently available.
15700 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15701 equality of representations. They will generally work correctly
15702 for strings and arrays whose elements have integer or enumeration types.
15703 They may not work correctly for arrays whose element
15704 types have user-defined equality, for arrays of real values
15705 (in particular, IEEE-conformant floating point, because of negative
15706 zeroes and NaNs), and for arrays whose elements contain unused bits with
15707 indeterminate values.
15710 The other component-by-component array operations (@code{and}, @code{or},
15711 @code{xor}, @code{not}, and relational tests other than equality)
15712 are not implemented.
15715 @cindex array aggregates (Ada)
15716 @cindex record aggregates (Ada)
15717 @cindex aggregates (Ada)
15718 There is limited support for array and record aggregates. They are
15719 permitted only on the right sides of assignments, as in these examples:
15722 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15723 (@value{GDBP}) set An_Array := (1, others => 0)
15724 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15725 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15726 (@value{GDBP}) set A_Record := (1, "Peter", True);
15727 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15731 discriminant's value by assigning an aggregate has an
15732 undefined effect if that discriminant is used within the record.
15733 However, you can first modify discriminants by directly assigning to
15734 them (which normally would not be allowed in Ada), and then performing an
15735 aggregate assignment. For example, given a variable @code{A_Rec}
15736 declared to have a type such as:
15739 type Rec (Len : Small_Integer := 0) is record
15741 Vals : IntArray (1 .. Len);
15745 you can assign a value with a different size of @code{Vals} with two
15749 (@value{GDBP}) set A_Rec.Len := 4
15750 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15753 As this example also illustrates, @value{GDBN} is very loose about the usual
15754 rules concerning aggregates. You may leave out some of the
15755 components of an array or record aggregate (such as the @code{Len}
15756 component in the assignment to @code{A_Rec} above); they will retain their
15757 original values upon assignment. You may freely use dynamic values as
15758 indices in component associations. You may even use overlapping or
15759 redundant component associations, although which component values are
15760 assigned in such cases is not defined.
15763 Calls to dispatching subprograms are not implemented.
15766 The overloading algorithm is much more limited (i.e., less selective)
15767 than that of real Ada. It makes only limited use of the context in
15768 which a subexpression appears to resolve its meaning, and it is much
15769 looser in its rules for allowing type matches. As a result, some
15770 function calls will be ambiguous, and the user will be asked to choose
15771 the proper resolution.
15774 The @code{new} operator is not implemented.
15777 Entry calls are not implemented.
15780 Aside from printing, arithmetic operations on the native VAX floating-point
15781 formats are not supported.
15784 It is not possible to slice a packed array.
15787 The names @code{True} and @code{False}, when not part of a qualified name,
15788 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15790 Should your program
15791 redefine these names in a package or procedure (at best a dubious practice),
15792 you will have to use fully qualified names to access their new definitions.
15795 @node Additions to Ada
15796 @subsubsection Additions to Ada
15797 @cindex Ada, deviations from
15799 As it does for other languages, @value{GDBN} makes certain generic
15800 extensions to Ada (@pxref{Expressions}):
15804 If the expression @var{E} is a variable residing in memory (typically
15805 a local variable or array element) and @var{N} is a positive integer,
15806 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15807 @var{N}-1 adjacent variables following it in memory as an array. In
15808 Ada, this operator is generally not necessary, since its prime use is
15809 in displaying parts of an array, and slicing will usually do this in
15810 Ada. However, there are occasional uses when debugging programs in
15811 which certain debugging information has been optimized away.
15814 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15815 appears in function or file @var{B}.'' When @var{B} is a file name,
15816 you must typically surround it in single quotes.
15819 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15820 @var{type} that appears at address @var{addr}.''
15823 A name starting with @samp{$} is a convenience variable
15824 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15827 In addition, @value{GDBN} provides a few other shortcuts and outright
15828 additions specific to Ada:
15832 The assignment statement is allowed as an expression, returning
15833 its right-hand operand as its value. Thus, you may enter
15836 (@value{GDBP}) set x := y + 3
15837 (@value{GDBP}) print A(tmp := y + 1)
15841 The semicolon is allowed as an ``operator,'' returning as its value
15842 the value of its right-hand operand.
15843 This allows, for example,
15844 complex conditional breaks:
15847 (@value{GDBP}) break f
15848 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15852 Rather than use catenation and symbolic character names to introduce special
15853 characters into strings, one may instead use a special bracket notation,
15854 which is also used to print strings. A sequence of characters of the form
15855 @samp{["@var{XX}"]} within a string or character literal denotes the
15856 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15857 sequence of characters @samp{["""]} also denotes a single quotation mark
15858 in strings. For example,
15860 "One line.["0a"]Next line.["0a"]"
15863 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15867 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15868 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15872 (@value{GDBP}) print 'max(x, y)
15876 When printing arrays, @value{GDBN} uses positional notation when the
15877 array has a lower bound of 1, and uses a modified named notation otherwise.
15878 For example, a one-dimensional array of three integers with a lower bound
15879 of 3 might print as
15886 That is, in contrast to valid Ada, only the first component has a @code{=>}
15890 You may abbreviate attributes in expressions with any unique,
15891 multi-character subsequence of
15892 their names (an exact match gets preference).
15893 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15894 in place of @t{a'length}.
15897 @cindex quoting Ada internal identifiers
15898 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15899 to lower case. The GNAT compiler uses upper-case characters for
15900 some of its internal identifiers, which are normally of no interest to users.
15901 For the rare occasions when you actually have to look at them,
15902 enclose them in angle brackets to avoid the lower-case mapping.
15905 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15909 Printing an object of class-wide type or dereferencing an
15910 access-to-class-wide value will display all the components of the object's
15911 specific type (as indicated by its run-time tag). Likewise, component
15912 selection on such a value will operate on the specific type of the
15917 @node Stopping Before Main Program
15918 @subsubsection Stopping at the Very Beginning
15920 @cindex breakpointing Ada elaboration code
15921 It is sometimes necessary to debug the program during elaboration, and
15922 before reaching the main procedure.
15923 As defined in the Ada Reference
15924 Manual, the elaboration code is invoked from a procedure called
15925 @code{adainit}. To run your program up to the beginning of
15926 elaboration, simply use the following two commands:
15927 @code{tbreak adainit} and @code{run}.
15929 @node Ada Exceptions
15930 @subsubsection Ada Exceptions
15932 A command is provided to list all Ada exceptions:
15935 @kindex info exceptions
15936 @item info exceptions
15937 @itemx info exceptions @var{regexp}
15938 The @code{info exceptions} command allows you to list all Ada exceptions
15939 defined within the program being debugged, as well as their addresses.
15940 With a regular expression, @var{regexp}, as argument, only those exceptions
15941 whose names match @var{regexp} are listed.
15944 Below is a small example, showing how the command can be used, first
15945 without argument, and next with a regular expression passed as an
15949 (@value{GDBP}) info exceptions
15950 All defined Ada exceptions:
15951 constraint_error: 0x613da0
15952 program_error: 0x613d20
15953 storage_error: 0x613ce0
15954 tasking_error: 0x613ca0
15955 const.aint_global_e: 0x613b00
15956 (@value{GDBP}) info exceptions const.aint
15957 All Ada exceptions matching regular expression "const.aint":
15958 constraint_error: 0x613da0
15959 const.aint_global_e: 0x613b00
15962 It is also possible to ask @value{GDBN} to stop your program's execution
15963 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15966 @subsubsection Extensions for Ada Tasks
15967 @cindex Ada, tasking
15969 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15970 @value{GDBN} provides the following task-related commands:
15975 This command shows a list of current Ada tasks, as in the following example:
15982 (@value{GDBP}) info tasks
15983 ID TID P-ID Pri State Name
15984 1 8088000 0 15 Child Activation Wait main_task
15985 2 80a4000 1 15 Accept Statement b
15986 3 809a800 1 15 Child Activation Wait a
15987 * 4 80ae800 3 15 Runnable c
15992 In this listing, the asterisk before the last task indicates it to be the
15993 task currently being inspected.
15997 Represents @value{GDBN}'s internal task number.
16003 The parent's task ID (@value{GDBN}'s internal task number).
16006 The base priority of the task.
16009 Current state of the task.
16013 The task has been created but has not been activated. It cannot be
16017 The task is not blocked for any reason known to Ada. (It may be waiting
16018 for a mutex, though.) It is conceptually "executing" in normal mode.
16021 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16022 that were waiting on terminate alternatives have been awakened and have
16023 terminated themselves.
16025 @item Child Activation Wait
16026 The task is waiting for created tasks to complete activation.
16028 @item Accept Statement
16029 The task is waiting on an accept or selective wait statement.
16031 @item Waiting on entry call
16032 The task is waiting on an entry call.
16034 @item Async Select Wait
16035 The task is waiting to start the abortable part of an asynchronous
16039 The task is waiting on a select statement with only a delay
16042 @item Child Termination Wait
16043 The task is sleeping having completed a master within itself, and is
16044 waiting for the tasks dependent on that master to become terminated or
16045 waiting on a terminate Phase.
16047 @item Wait Child in Term Alt
16048 The task is sleeping waiting for tasks on terminate alternatives to
16049 finish terminating.
16051 @item Accepting RV with @var{taskno}
16052 The task is accepting a rendez-vous with the task @var{taskno}.
16056 Name of the task in the program.
16060 @kindex info task @var{taskno}
16061 @item info task @var{taskno}
16062 This command shows detailled informations on the specified task, as in
16063 the following example:
16068 (@value{GDBP}) info tasks
16069 ID TID P-ID Pri State Name
16070 1 8077880 0 15 Child Activation Wait main_task
16071 * 2 807c468 1 15 Runnable task_1
16072 (@value{GDBP}) info task 2
16073 Ada Task: 0x807c468
16076 Parent: 1 (main_task)
16082 @kindex task@r{ (Ada)}
16083 @cindex current Ada task ID
16084 This command prints the ID of the current task.
16090 (@value{GDBP}) info tasks
16091 ID TID P-ID Pri State Name
16092 1 8077870 0 15 Child Activation Wait main_task
16093 * 2 807c458 1 15 Runnable t
16094 (@value{GDBP}) task
16095 [Current task is 2]
16098 @item task @var{taskno}
16099 @cindex Ada task switching
16100 This command is like the @code{thread @var{threadno}}
16101 command (@pxref{Threads}). It switches the context of debugging
16102 from the current task to the given task.
16108 (@value{GDBP}) info tasks
16109 ID TID P-ID Pri State Name
16110 1 8077870 0 15 Child Activation Wait main_task
16111 * 2 807c458 1 15 Runnable t
16112 (@value{GDBP}) task 1
16113 [Switching to task 1]
16114 #0 0x8067726 in pthread_cond_wait ()
16116 #0 0x8067726 in pthread_cond_wait ()
16117 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16118 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16119 #3 0x806153e in system.tasking.stages.activate_tasks ()
16120 #4 0x804aacc in un () at un.adb:5
16123 @item break @var{location} task @var{taskno}
16124 @itemx break @var{location} task @var{taskno} if @dots{}
16125 @cindex breakpoints and tasks, in Ada
16126 @cindex task breakpoints, in Ada
16127 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16128 These commands are like the @code{break @dots{} thread @dots{}}
16129 command (@pxref{Thread Stops}). The
16130 @var{location} argument specifies source lines, as described
16131 in @ref{Specify Location}.
16133 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16134 to specify that you only want @value{GDBN} to stop the program when a
16135 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16136 numeric task identifiers assigned by @value{GDBN}, shown in the first
16137 column of the @samp{info tasks} display.
16139 If you do not specify @samp{task @var{taskno}} when you set a
16140 breakpoint, the breakpoint applies to @emph{all} tasks of your
16143 You can use the @code{task} qualifier on conditional breakpoints as
16144 well; in this case, place @samp{task @var{taskno}} before the
16145 breakpoint condition (before the @code{if}).
16153 (@value{GDBP}) info tasks
16154 ID TID P-ID Pri State Name
16155 1 140022020 0 15 Child Activation Wait main_task
16156 2 140045060 1 15 Accept/Select Wait t2
16157 3 140044840 1 15 Runnable t1
16158 * 4 140056040 1 15 Runnable t3
16159 (@value{GDBP}) b 15 task 2
16160 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16161 (@value{GDBP}) cont
16166 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16168 (@value{GDBP}) info tasks
16169 ID TID P-ID Pri State Name
16170 1 140022020 0 15 Child Activation Wait main_task
16171 * 2 140045060 1 15 Runnable t2
16172 3 140044840 1 15 Runnable t1
16173 4 140056040 1 15 Delay Sleep t3
16177 @node Ada Tasks and Core Files
16178 @subsubsection Tasking Support when Debugging Core Files
16179 @cindex Ada tasking and core file debugging
16181 When inspecting a core file, as opposed to debugging a live program,
16182 tasking support may be limited or even unavailable, depending on
16183 the platform being used.
16184 For instance, on x86-linux, the list of tasks is available, but task
16185 switching is not supported.
16187 On certain platforms, the debugger needs to perform some
16188 memory writes in order to provide Ada tasking support. When inspecting
16189 a core file, this means that the core file must be opened with read-write
16190 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16191 Under these circumstances, you should make a backup copy of the core
16192 file before inspecting it with @value{GDBN}.
16194 @node Ravenscar Profile
16195 @subsubsection Tasking Support when using the Ravenscar Profile
16196 @cindex Ravenscar Profile
16198 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16199 specifically designed for systems with safety-critical real-time
16203 @kindex set ravenscar task-switching on
16204 @cindex task switching with program using Ravenscar Profile
16205 @item set ravenscar task-switching on
16206 Allows task switching when debugging a program that uses the Ravenscar
16207 Profile. This is the default.
16209 @kindex set ravenscar task-switching off
16210 @item set ravenscar task-switching off
16211 Turn off task switching when debugging a program that uses the Ravenscar
16212 Profile. This is mostly intended to disable the code that adds support
16213 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16214 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16215 To be effective, this command should be run before the program is started.
16217 @kindex show ravenscar task-switching
16218 @item show ravenscar task-switching
16219 Show whether it is possible to switch from task to task in a program
16220 using the Ravenscar Profile.
16225 @subsubsection Known Peculiarities of Ada Mode
16226 @cindex Ada, problems
16228 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16229 we know of several problems with and limitations of Ada mode in
16231 some of which will be fixed with planned future releases of the debugger
16232 and the GNU Ada compiler.
16236 Static constants that the compiler chooses not to materialize as objects in
16237 storage are invisible to the debugger.
16240 Named parameter associations in function argument lists are ignored (the
16241 argument lists are treated as positional).
16244 Many useful library packages are currently invisible to the debugger.
16247 Fixed-point arithmetic, conversions, input, and output is carried out using
16248 floating-point arithmetic, and may give results that only approximate those on
16252 The GNAT compiler never generates the prefix @code{Standard} for any of
16253 the standard symbols defined by the Ada language. @value{GDBN} knows about
16254 this: it will strip the prefix from names when you use it, and will never
16255 look for a name you have so qualified among local symbols, nor match against
16256 symbols in other packages or subprograms. If you have
16257 defined entities anywhere in your program other than parameters and
16258 local variables whose simple names match names in @code{Standard},
16259 GNAT's lack of qualification here can cause confusion. When this happens,
16260 you can usually resolve the confusion
16261 by qualifying the problematic names with package
16262 @code{Standard} explicitly.
16265 Older versions of the compiler sometimes generate erroneous debugging
16266 information, resulting in the debugger incorrectly printing the value
16267 of affected entities. In some cases, the debugger is able to work
16268 around an issue automatically. In other cases, the debugger is able
16269 to work around the issue, but the work-around has to be specifically
16272 @kindex set ada trust-PAD-over-XVS
16273 @kindex show ada trust-PAD-over-XVS
16276 @item set ada trust-PAD-over-XVS on
16277 Configure GDB to strictly follow the GNAT encoding when computing the
16278 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16279 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16280 a complete description of the encoding used by the GNAT compiler).
16281 This is the default.
16283 @item set ada trust-PAD-over-XVS off
16284 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16285 sometimes prints the wrong value for certain entities, changing @code{ada
16286 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16287 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16288 @code{off}, but this incurs a slight performance penalty, so it is
16289 recommended to leave this setting to @code{on} unless necessary.
16293 @cindex GNAT descriptive types
16294 @cindex GNAT encoding
16295 Internally, the debugger also relies on the compiler following a number
16296 of conventions known as the @samp{GNAT Encoding}, all documented in
16297 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16298 how the debugging information should be generated for certain types.
16299 In particular, this convention makes use of @dfn{descriptive types},
16300 which are artificial types generated purely to help the debugger.
16302 These encodings were defined at a time when the debugging information
16303 format used was not powerful enough to describe some of the more complex
16304 types available in Ada. Since DWARF allows us to express nearly all
16305 Ada features, the long-term goal is to slowly replace these descriptive
16306 types by their pure DWARF equivalent. To facilitate that transition,
16307 a new maintenance option is available to force the debugger to ignore
16308 those descriptive types. It allows the user to quickly evaluate how
16309 well @value{GDBN} works without them.
16313 @kindex maint ada set ignore-descriptive-types
16314 @item maintenance ada set ignore-descriptive-types [on|off]
16315 Control whether the debugger should ignore descriptive types.
16316 The default is not to ignore descriptives types (@code{off}).
16318 @kindex maint ada show ignore-descriptive-types
16319 @item maintenance ada show ignore-descriptive-types
16320 Show if descriptive types are ignored by @value{GDBN}.
16324 @node Unsupported Languages
16325 @section Unsupported Languages
16327 @cindex unsupported languages
16328 @cindex minimal language
16329 In addition to the other fully-supported programming languages,
16330 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16331 It does not represent a real programming language, but provides a set
16332 of capabilities close to what the C or assembly languages provide.
16333 This should allow most simple operations to be performed while debugging
16334 an application that uses a language currently not supported by @value{GDBN}.
16336 If the language is set to @code{auto}, @value{GDBN} will automatically
16337 select this language if the current frame corresponds to an unsupported
16341 @chapter Examining the Symbol Table
16343 The commands described in this chapter allow you to inquire about the
16344 symbols (names of variables, functions and types) defined in your
16345 program. This information is inherent in the text of your program and
16346 does not change as your program executes. @value{GDBN} finds it in your
16347 program's symbol table, in the file indicated when you started @value{GDBN}
16348 (@pxref{File Options, ,Choosing Files}), or by one of the
16349 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16351 @cindex symbol names
16352 @cindex names of symbols
16353 @cindex quoting names
16354 Occasionally, you may need to refer to symbols that contain unusual
16355 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16356 most frequent case is in referring to static variables in other
16357 source files (@pxref{Variables,,Program Variables}). File names
16358 are recorded in object files as debugging symbols, but @value{GDBN} would
16359 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16360 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16361 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16368 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16371 @cindex case-insensitive symbol names
16372 @cindex case sensitivity in symbol names
16373 @kindex set case-sensitive
16374 @item set case-sensitive on
16375 @itemx set case-sensitive off
16376 @itemx set case-sensitive auto
16377 Normally, when @value{GDBN} looks up symbols, it matches their names
16378 with case sensitivity determined by the current source language.
16379 Occasionally, you may wish to control that. The command @code{set
16380 case-sensitive} lets you do that by specifying @code{on} for
16381 case-sensitive matches or @code{off} for case-insensitive ones. If
16382 you specify @code{auto}, case sensitivity is reset to the default
16383 suitable for the source language. The default is case-sensitive
16384 matches for all languages except for Fortran, for which the default is
16385 case-insensitive matches.
16387 @kindex show case-sensitive
16388 @item show case-sensitive
16389 This command shows the current setting of case sensitivity for symbols
16392 @kindex set print type methods
16393 @item set print type methods
16394 @itemx set print type methods on
16395 @itemx set print type methods off
16396 Normally, when @value{GDBN} prints a class, it displays any methods
16397 declared in that class. You can control this behavior either by
16398 passing the appropriate flag to @code{ptype}, or using @command{set
16399 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16400 display the methods; this is the default. Specifying @code{off} will
16401 cause @value{GDBN} to omit the methods.
16403 @kindex show print type methods
16404 @item show print type methods
16405 This command shows the current setting of method display when printing
16408 @kindex set print type typedefs
16409 @item set print type typedefs
16410 @itemx set print type typedefs on
16411 @itemx set print type typedefs off
16413 Normally, when @value{GDBN} prints a class, it displays any typedefs
16414 defined in that class. You can control this behavior either by
16415 passing the appropriate flag to @code{ptype}, or using @command{set
16416 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16417 display the typedef definitions; this is the default. Specifying
16418 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16419 Note that this controls whether the typedef definition itself is
16420 printed, not whether typedef names are substituted when printing other
16423 @kindex show print type typedefs
16424 @item show print type typedefs
16425 This command shows the current setting of typedef display when
16428 @kindex info address
16429 @cindex address of a symbol
16430 @item info address @var{symbol}
16431 Describe where the data for @var{symbol} is stored. For a register
16432 variable, this says which register it is kept in. For a non-register
16433 local variable, this prints the stack-frame offset at which the variable
16436 Note the contrast with @samp{print &@var{symbol}}, which does not work
16437 at all for a register variable, and for a stack local variable prints
16438 the exact address of the current instantiation of the variable.
16440 @kindex info symbol
16441 @cindex symbol from address
16442 @cindex closest symbol and offset for an address
16443 @item info symbol @var{addr}
16444 Print the name of a symbol which is stored at the address @var{addr}.
16445 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16446 nearest symbol and an offset from it:
16449 (@value{GDBP}) info symbol 0x54320
16450 _initialize_vx + 396 in section .text
16454 This is the opposite of the @code{info address} command. You can use
16455 it to find out the name of a variable or a function given its address.
16457 For dynamically linked executables, the name of executable or shared
16458 library containing the symbol is also printed:
16461 (@value{GDBP}) info symbol 0x400225
16462 _start + 5 in section .text of /tmp/a.out
16463 (@value{GDBP}) info symbol 0x2aaaac2811cf
16464 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16469 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16470 Demangle @var{name}.
16471 If @var{language} is provided it is the name of the language to demangle
16472 @var{name} in. Otherwise @var{name} is demangled in the current language.
16474 The @samp{--} option specifies the end of options,
16475 and is useful when @var{name} begins with a dash.
16477 The parameter @code{demangle-style} specifies how to interpret the kind
16478 of mangling used. @xref{Print Settings}.
16481 @item whatis[/@var{flags}] [@var{arg}]
16482 Print the data type of @var{arg}, which can be either an expression
16483 or a name of a data type. With no argument, print the data type of
16484 @code{$}, the last value in the value history.
16486 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16487 is not actually evaluated, and any side-effecting operations (such as
16488 assignments or function calls) inside it do not take place.
16490 If @var{arg} is a variable or an expression, @code{whatis} prints its
16491 literal type as it is used in the source code. If the type was
16492 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16493 the data type underlying the @code{typedef}. If the type of the
16494 variable or the expression is a compound data type, such as
16495 @code{struct} or @code{class}, @code{whatis} never prints their
16496 fields or methods. It just prints the @code{struct}/@code{class}
16497 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16498 such a compound data type, use @code{ptype}.
16500 If @var{arg} is a type name that was defined using @code{typedef},
16501 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16502 Unrolling means that @code{whatis} will show the underlying type used
16503 in the @code{typedef} declaration of @var{arg}. However, if that
16504 underlying type is also a @code{typedef}, @code{whatis} will not
16507 For C code, the type names may also have the form @samp{class
16508 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16509 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16511 @var{flags} can be used to modify how the type is displayed.
16512 Available flags are:
16516 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16517 parameters and typedefs defined in a class when printing the class'
16518 members. The @code{/r} flag disables this.
16521 Do not print methods defined in the class.
16524 Print methods defined in the class. This is the default, but the flag
16525 exists in case you change the default with @command{set print type methods}.
16528 Do not print typedefs defined in the class. Note that this controls
16529 whether the typedef definition itself is printed, not whether typedef
16530 names are substituted when printing other types.
16533 Print typedefs defined in the class. This is the default, but the flag
16534 exists in case you change the default with @command{set print type typedefs}.
16538 @item ptype[/@var{flags}] [@var{arg}]
16539 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16540 detailed description of the type, instead of just the name of the type.
16541 @xref{Expressions, ,Expressions}.
16543 Contrary to @code{whatis}, @code{ptype} always unrolls any
16544 @code{typedef}s in its argument declaration, whether the argument is
16545 a variable, expression, or a data type. This means that @code{ptype}
16546 of a variable or an expression will not print literally its type as
16547 present in the source code---use @code{whatis} for that. @code{typedef}s at
16548 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16549 fields, methods and inner @code{class typedef}s of @code{struct}s,
16550 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16552 For example, for this variable declaration:
16555 typedef double real_t;
16556 struct complex @{ real_t real; double imag; @};
16557 typedef struct complex complex_t;
16559 real_t *real_pointer_var;
16563 the two commands give this output:
16567 (@value{GDBP}) whatis var
16569 (@value{GDBP}) ptype var
16570 type = struct complex @{
16574 (@value{GDBP}) whatis complex_t
16575 type = struct complex
16576 (@value{GDBP}) whatis struct complex
16577 type = struct complex
16578 (@value{GDBP}) ptype struct complex
16579 type = struct complex @{
16583 (@value{GDBP}) whatis real_pointer_var
16585 (@value{GDBP}) ptype real_pointer_var
16591 As with @code{whatis}, using @code{ptype} without an argument refers to
16592 the type of @code{$}, the last value in the value history.
16594 @cindex incomplete type
16595 Sometimes, programs use opaque data types or incomplete specifications
16596 of complex data structure. If the debug information included in the
16597 program does not allow @value{GDBN} to display a full declaration of
16598 the data type, it will say @samp{<incomplete type>}. For example,
16599 given these declarations:
16603 struct foo *fooptr;
16607 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16610 (@value{GDBP}) ptype foo
16611 $1 = <incomplete type>
16615 ``Incomplete type'' is C terminology for data types that are not
16616 completely specified.
16619 @item info types @var{regexp}
16621 Print a brief description of all types whose names match the regular
16622 expression @var{regexp} (or all types in your program, if you supply
16623 no argument). Each complete typename is matched as though it were a
16624 complete line; thus, @samp{i type value} gives information on all
16625 types in your program whose names include the string @code{value}, but
16626 @samp{i type ^value$} gives information only on types whose complete
16627 name is @code{value}.
16629 This command differs from @code{ptype} in two ways: first, like
16630 @code{whatis}, it does not print a detailed description; second, it
16631 lists all source files where a type is defined.
16633 @kindex info type-printers
16634 @item info type-printers
16635 Versions of @value{GDBN} that ship with Python scripting enabled may
16636 have ``type printers'' available. When using @command{ptype} or
16637 @command{whatis}, these printers are consulted when the name of a type
16638 is needed. @xref{Type Printing API}, for more information on writing
16641 @code{info type-printers} displays all the available type printers.
16643 @kindex enable type-printer
16644 @kindex disable type-printer
16645 @item enable type-printer @var{name}@dots{}
16646 @item disable type-printer @var{name}@dots{}
16647 These commands can be used to enable or disable type printers.
16650 @cindex local variables
16651 @item info scope @var{location}
16652 List all the variables local to a particular scope. This command
16653 accepts a @var{location} argument---a function name, a source line, or
16654 an address preceded by a @samp{*}, and prints all the variables local
16655 to the scope defined by that location. (@xref{Specify Location}, for
16656 details about supported forms of @var{location}.) For example:
16659 (@value{GDBP}) @b{info scope command_line_handler}
16660 Scope for command_line_handler:
16661 Symbol rl is an argument at stack/frame offset 8, length 4.
16662 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16663 Symbol linelength is in static storage at address 0x150a1c, length 4.
16664 Symbol p is a local variable in register $esi, length 4.
16665 Symbol p1 is a local variable in register $ebx, length 4.
16666 Symbol nline is a local variable in register $edx, length 4.
16667 Symbol repeat is a local variable at frame offset -8, length 4.
16671 This command is especially useful for determining what data to collect
16672 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16675 @kindex info source
16677 Show information about the current source file---that is, the source file for
16678 the function containing the current point of execution:
16681 the name of the source file, and the directory containing it,
16683 the directory it was compiled in,
16685 its length, in lines,
16687 which programming language it is written in,
16689 if the debug information provides it, the program that compiled the file
16690 (which may include, e.g., the compiler version and command line arguments),
16692 whether the executable includes debugging information for that file, and
16693 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16695 whether the debugging information includes information about
16696 preprocessor macros.
16700 @kindex info sources
16702 Print the names of all source files in your program for which there is
16703 debugging information, organized into two lists: files whose symbols
16704 have already been read, and files whose symbols will be read when needed.
16706 @kindex info functions
16707 @item info functions
16708 Print the names and data types of all defined functions.
16710 @item info functions @var{regexp}
16711 Print the names and data types of all defined functions
16712 whose names contain a match for regular expression @var{regexp}.
16713 Thus, @samp{info fun step} finds all functions whose names
16714 include @code{step}; @samp{info fun ^step} finds those whose names
16715 start with @code{step}. If a function name contains characters
16716 that conflict with the regular expression language (e.g.@:
16717 @samp{operator*()}), they may be quoted with a backslash.
16719 @kindex info variables
16720 @item info variables
16721 Print the names and data types of all variables that are defined
16722 outside of functions (i.e.@: excluding local variables).
16724 @item info variables @var{regexp}
16725 Print the names and data types of all variables (except for local
16726 variables) whose names contain a match for regular expression
16729 @kindex info classes
16730 @cindex Objective-C, classes and selectors
16732 @itemx info classes @var{regexp}
16733 Display all Objective-C classes in your program, or
16734 (with the @var{regexp} argument) all those matching a particular regular
16737 @kindex info selectors
16738 @item info selectors
16739 @itemx info selectors @var{regexp}
16740 Display all Objective-C selectors in your program, or
16741 (with the @var{regexp} argument) all those matching a particular regular
16745 This was never implemented.
16746 @kindex info methods
16748 @itemx info methods @var{regexp}
16749 The @code{info methods} command permits the user to examine all defined
16750 methods within C@t{++} program, or (with the @var{regexp} argument) a
16751 specific set of methods found in the various C@t{++} classes. Many
16752 C@t{++} classes provide a large number of methods. Thus, the output
16753 from the @code{ptype} command can be overwhelming and hard to use. The
16754 @code{info-methods} command filters the methods, printing only those
16755 which match the regular-expression @var{regexp}.
16758 @cindex opaque data types
16759 @kindex set opaque-type-resolution
16760 @item set opaque-type-resolution on
16761 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16762 declared as a pointer to a @code{struct}, @code{class}, or
16763 @code{union}---for example, @code{struct MyType *}---that is used in one
16764 source file although the full declaration of @code{struct MyType} is in
16765 another source file. The default is on.
16767 A change in the setting of this subcommand will not take effect until
16768 the next time symbols for a file are loaded.
16770 @item set opaque-type-resolution off
16771 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16772 is printed as follows:
16774 @{<no data fields>@}
16777 @kindex show opaque-type-resolution
16778 @item show opaque-type-resolution
16779 Show whether opaque types are resolved or not.
16781 @kindex set print symbol-loading
16782 @cindex print messages when symbols are loaded
16783 @item set print symbol-loading
16784 @itemx set print symbol-loading full
16785 @itemx set print symbol-loading brief
16786 @itemx set print symbol-loading off
16787 The @code{set print symbol-loading} command allows you to control the
16788 printing of messages when @value{GDBN} loads symbol information.
16789 By default a message is printed for the executable and one for each
16790 shared library, and normally this is what you want. However, when
16791 debugging apps with large numbers of shared libraries these messages
16793 When set to @code{brief} a message is printed for each executable,
16794 and when @value{GDBN} loads a collection of shared libraries at once
16795 it will only print one message regardless of the number of shared
16796 libraries. When set to @code{off} no messages are printed.
16798 @kindex show print symbol-loading
16799 @item show print symbol-loading
16800 Show whether messages will be printed when a @value{GDBN} command
16801 entered from the keyboard causes symbol information to be loaded.
16803 @kindex maint print symbols
16804 @cindex symbol dump
16805 @kindex maint print psymbols
16806 @cindex partial symbol dump
16807 @kindex maint print msymbols
16808 @cindex minimal symbol dump
16809 @item maint print symbols @var{filename}
16810 @itemx maint print psymbols @var{filename}
16811 @itemx maint print msymbols @var{filename}
16812 Write a dump of debugging symbol data into the file @var{filename}.
16813 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16814 symbols with debugging data are included. If you use @samp{maint print
16815 symbols}, @value{GDBN} includes all the symbols for which it has already
16816 collected full details: that is, @var{filename} reflects symbols for
16817 only those files whose symbols @value{GDBN} has read. You can use the
16818 command @code{info sources} to find out which files these are. If you
16819 use @samp{maint print psymbols} instead, the dump shows information about
16820 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16821 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16822 @samp{maint print msymbols} dumps just the minimal symbol information
16823 required for each object file from which @value{GDBN} has read some symbols.
16824 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16825 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16827 @kindex maint info symtabs
16828 @kindex maint info psymtabs
16829 @cindex listing @value{GDBN}'s internal symbol tables
16830 @cindex symbol tables, listing @value{GDBN}'s internal
16831 @cindex full symbol tables, listing @value{GDBN}'s internal
16832 @cindex partial symbol tables, listing @value{GDBN}'s internal
16833 @item maint info symtabs @r{[} @var{regexp} @r{]}
16834 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16836 List the @code{struct symtab} or @code{struct partial_symtab}
16837 structures whose names match @var{regexp}. If @var{regexp} is not
16838 given, list them all. The output includes expressions which you can
16839 copy into a @value{GDBN} debugging this one to examine a particular
16840 structure in more detail. For example:
16843 (@value{GDBP}) maint info psymtabs dwarf2read
16844 @{ objfile /home/gnu/build/gdb/gdb
16845 ((struct objfile *) 0x82e69d0)
16846 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16847 ((struct partial_symtab *) 0x8474b10)
16850 text addresses 0x814d3c8 -- 0x8158074
16851 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16852 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16853 dependencies (none)
16856 (@value{GDBP}) maint info symtabs
16860 We see that there is one partial symbol table whose filename contains
16861 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16862 and we see that @value{GDBN} has not read in any symtabs yet at all.
16863 If we set a breakpoint on a function, that will cause @value{GDBN} to
16864 read the symtab for the compilation unit containing that function:
16867 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16868 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16870 (@value{GDBP}) maint info symtabs
16871 @{ objfile /home/gnu/build/gdb/gdb
16872 ((struct objfile *) 0x82e69d0)
16873 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16874 ((struct symtab *) 0x86c1f38)
16877 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16878 linetable ((struct linetable *) 0x8370fa0)
16879 debugformat DWARF 2
16885 @kindex maint set symbol-cache-size
16886 @cindex symbol cache size
16887 @item maint set symbol-cache-size @var{size}
16888 Set the size of the symbol cache to @var{size}.
16889 The default size is intended to be good enough for debugging
16890 most applications. This option exists to allow for experimenting
16891 with different sizes.
16893 @kindex maint show symbol-cache-size
16894 @item maint show symbol-cache-size
16895 Show the size of the symbol cache.
16897 @kindex maint print symbol-cache
16898 @cindex symbol cache, printing its contents
16899 @item maint print symbol-cache
16900 Print the contents of the symbol cache.
16901 This is useful when debugging symbol cache issues.
16903 @kindex maint print symbol-cache-statistics
16904 @cindex symbol cache, printing usage statistics
16905 @item maint print symbol-cache-statistics
16906 Print symbol cache usage statistics.
16907 This helps determine how well the cache is being utilized.
16909 @kindex maint flush-symbol-cache
16910 @cindex symbol cache, flushing
16911 @item maint flush-symbol-cache
16912 Flush the contents of the symbol cache, all entries are removed.
16913 This command is useful when debugging the symbol cache.
16914 It is also useful when collecting performance data.
16919 @chapter Altering Execution
16921 Once you think you have found an error in your program, you might want to
16922 find out for certain whether correcting the apparent error would lead to
16923 correct results in the rest of the run. You can find the answer by
16924 experiment, using the @value{GDBN} features for altering execution of the
16927 For example, you can store new values into variables or memory
16928 locations, give your program a signal, restart it at a different
16929 address, or even return prematurely from a function.
16932 * Assignment:: Assignment to variables
16933 * Jumping:: Continuing at a different address
16934 * Signaling:: Giving your program a signal
16935 * Returning:: Returning from a function
16936 * Calling:: Calling your program's functions
16937 * Patching:: Patching your program
16938 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
16942 @section Assignment to Variables
16945 @cindex setting variables
16946 To alter the value of a variable, evaluate an assignment expression.
16947 @xref{Expressions, ,Expressions}. For example,
16954 stores the value 4 into the variable @code{x}, and then prints the
16955 value of the assignment expression (which is 4).
16956 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16957 information on operators in supported languages.
16959 @kindex set variable
16960 @cindex variables, setting
16961 If you are not interested in seeing the value of the assignment, use the
16962 @code{set} command instead of the @code{print} command. @code{set} is
16963 really the same as @code{print} except that the expression's value is
16964 not printed and is not put in the value history (@pxref{Value History,
16965 ,Value History}). The expression is evaluated only for its effects.
16967 If the beginning of the argument string of the @code{set} command
16968 appears identical to a @code{set} subcommand, use the @code{set
16969 variable} command instead of just @code{set}. This command is identical
16970 to @code{set} except for its lack of subcommands. For example, if your
16971 program has a variable @code{width}, you get an error if you try to set
16972 a new value with just @samp{set width=13}, because @value{GDBN} has the
16973 command @code{set width}:
16976 (@value{GDBP}) whatis width
16978 (@value{GDBP}) p width
16980 (@value{GDBP}) set width=47
16981 Invalid syntax in expression.
16985 The invalid expression, of course, is @samp{=47}. In
16986 order to actually set the program's variable @code{width}, use
16989 (@value{GDBP}) set var width=47
16992 Because the @code{set} command has many subcommands that can conflict
16993 with the names of program variables, it is a good idea to use the
16994 @code{set variable} command instead of just @code{set}. For example, if
16995 your program has a variable @code{g}, you run into problems if you try
16996 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16997 the command @code{set gnutarget}, abbreviated @code{set g}:
17001 (@value{GDBP}) whatis g
17005 (@value{GDBP}) set g=4
17009 The program being debugged has been started already.
17010 Start it from the beginning? (y or n) y
17011 Starting program: /home/smith/cc_progs/a.out
17012 "/home/smith/cc_progs/a.out": can't open to read symbols:
17013 Invalid bfd target.
17014 (@value{GDBP}) show g
17015 The current BFD target is "=4".
17020 The program variable @code{g} did not change, and you silently set the
17021 @code{gnutarget} to an invalid value. In order to set the variable
17025 (@value{GDBP}) set var g=4
17028 @value{GDBN} allows more implicit conversions in assignments than C; you can
17029 freely store an integer value into a pointer variable or vice versa,
17030 and you can convert any structure to any other structure that is the
17031 same length or shorter.
17032 @comment FIXME: how do structs align/pad in these conversions?
17033 @comment /doc@cygnus.com 18dec1990
17035 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17036 construct to generate a value of specified type at a specified address
17037 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17038 to memory location @code{0x83040} as an integer (which implies a certain size
17039 and representation in memory), and
17042 set @{int@}0x83040 = 4
17046 stores the value 4 into that memory location.
17049 @section Continuing at a Different Address
17051 Ordinarily, when you continue your program, you do so at the place where
17052 it stopped, with the @code{continue} command. You can instead continue at
17053 an address of your own choosing, with the following commands:
17057 @kindex j @r{(@code{jump})}
17058 @item jump @var{location}
17059 @itemx j @var{location}
17060 Resume execution at @var{location}. Execution stops again immediately
17061 if there is a breakpoint there. @xref{Specify Location}, for a description
17062 of the different forms of @var{location}. It is common
17063 practice to use the @code{tbreak} command in conjunction with
17064 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17066 The @code{jump} command does not change the current stack frame, or
17067 the stack pointer, or the contents of any memory location or any
17068 register other than the program counter. If @var{location} is in
17069 a different function from the one currently executing, the results may
17070 be bizarre if the two functions expect different patterns of arguments or
17071 of local variables. For this reason, the @code{jump} command requests
17072 confirmation if the specified line is not in the function currently
17073 executing. However, even bizarre results are predictable if you are
17074 well acquainted with the machine-language code of your program.
17077 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
17078 On many systems, you can get much the same effect as the @code{jump}
17079 command by storing a new value into the register @code{$pc}. The
17080 difference is that this does not start your program running; it only
17081 changes the address of where it @emph{will} run when you continue. For
17089 makes the next @code{continue} command or stepping command execute at
17090 address @code{0x485}, rather than at the address where your program stopped.
17091 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17093 The most common occasion to use the @code{jump} command is to back
17094 up---perhaps with more breakpoints set---over a portion of a program
17095 that has already executed, in order to examine its execution in more
17100 @section Giving your Program a Signal
17101 @cindex deliver a signal to a program
17105 @item signal @var{signal}
17106 Resume execution where your program is stopped, but immediately give it the
17107 signal @var{signal}. The @var{signal} can be the name or the number of a
17108 signal. For example, on many systems @code{signal 2} and @code{signal
17109 SIGINT} are both ways of sending an interrupt signal.
17111 Alternatively, if @var{signal} is zero, continue execution without
17112 giving a signal. This is useful when your program stopped on account of
17113 a signal and would ordinarily see the signal when resumed with the
17114 @code{continue} command; @samp{signal 0} causes it to resume without a
17117 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17118 delivered to the currently selected thread, not the thread that last
17119 reported a stop. This includes the situation where a thread was
17120 stopped due to a signal. So if you want to continue execution
17121 suppressing the signal that stopped a thread, you should select that
17122 same thread before issuing the @samp{signal 0} command. If you issue
17123 the @samp{signal 0} command with another thread as the selected one,
17124 @value{GDBN} detects that and asks for confirmation.
17126 Invoking the @code{signal} command is not the same as invoking the
17127 @code{kill} utility from the shell. Sending a signal with @code{kill}
17128 causes @value{GDBN} to decide what to do with the signal depending on
17129 the signal handling tables (@pxref{Signals}). The @code{signal} command
17130 passes the signal directly to your program.
17132 @code{signal} does not repeat when you press @key{RET} a second time
17133 after executing the command.
17135 @kindex queue-signal
17136 @item queue-signal @var{signal}
17137 Queue @var{signal} to be delivered immediately to the current thread
17138 when execution of the thread resumes. The @var{signal} can be the name or
17139 the number of a signal. For example, on many systems @code{signal 2} and
17140 @code{signal SIGINT} are both ways of sending an interrupt signal.
17141 The handling of the signal must be set to pass the signal to the program,
17142 otherwise @value{GDBN} will report an error.
17143 You can control the handling of signals from @value{GDBN} with the
17144 @code{handle} command (@pxref{Signals}).
17146 Alternatively, if @var{signal} is zero, any currently queued signal
17147 for the current thread is discarded and when execution resumes no signal
17148 will be delivered. This is useful when your program stopped on account
17149 of a signal and would ordinarily see the signal when resumed with the
17150 @code{continue} command.
17152 This command differs from the @code{signal} command in that the signal
17153 is just queued, execution is not resumed. And @code{queue-signal} cannot
17154 be used to pass a signal whose handling state has been set to @code{nopass}
17159 @xref{stepping into signal handlers}, for information on how stepping
17160 commands behave when the thread has a signal queued.
17163 @section Returning from a Function
17166 @cindex returning from a function
17169 @itemx return @var{expression}
17170 You can cancel execution of a function call with the @code{return}
17171 command. If you give an
17172 @var{expression} argument, its value is used as the function's return
17176 When you use @code{return}, @value{GDBN} discards the selected stack frame
17177 (and all frames within it). You can think of this as making the
17178 discarded frame return prematurely. If you wish to specify a value to
17179 be returned, give that value as the argument to @code{return}.
17181 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17182 Frame}), and any other frames inside of it, leaving its caller as the
17183 innermost remaining frame. That frame becomes selected. The
17184 specified value is stored in the registers used for returning values
17187 The @code{return} command does not resume execution; it leaves the
17188 program stopped in the state that would exist if the function had just
17189 returned. In contrast, the @code{finish} command (@pxref{Continuing
17190 and Stepping, ,Continuing and Stepping}) resumes execution until the
17191 selected stack frame returns naturally.
17193 @value{GDBN} needs to know how the @var{expression} argument should be set for
17194 the inferior. The concrete registers assignment depends on the OS ABI and the
17195 type being returned by the selected stack frame. For example it is common for
17196 OS ABI to return floating point values in FPU registers while integer values in
17197 CPU registers. Still some ABIs return even floating point values in CPU
17198 registers. Larger integer widths (such as @code{long long int}) also have
17199 specific placement rules. @value{GDBN} already knows the OS ABI from its
17200 current target so it needs to find out also the type being returned to make the
17201 assignment into the right register(s).
17203 Normally, the selected stack frame has debug info. @value{GDBN} will always
17204 use the debug info instead of the implicit type of @var{expression} when the
17205 debug info is available. For example, if you type @kbd{return -1}, and the
17206 function in the current stack frame is declared to return a @code{long long
17207 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17208 into a @code{long long int}:
17211 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17213 (@value{GDBP}) return -1
17214 Make func return now? (y or n) y
17215 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17216 43 printf ("result=%lld\n", func ());
17220 However, if the selected stack frame does not have a debug info, e.g., if the
17221 function was compiled without debug info, @value{GDBN} has to find out the type
17222 to return from user. Specifying a different type by mistake may set the value
17223 in different inferior registers than the caller code expects. For example,
17224 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17225 of a @code{long long int} result for a debug info less function (on 32-bit
17226 architectures). Therefore the user is required to specify the return type by
17227 an appropriate cast explicitly:
17230 Breakpoint 2, 0x0040050b in func ()
17231 (@value{GDBP}) return -1
17232 Return value type not available for selected stack frame.
17233 Please use an explicit cast of the value to return.
17234 (@value{GDBP}) return (long long int) -1
17235 Make selected stack frame return now? (y or n) y
17236 #0 0x00400526 in main ()
17241 @section Calling Program Functions
17244 @cindex calling functions
17245 @cindex inferior functions, calling
17246 @item print @var{expr}
17247 Evaluate the expression @var{expr} and display the resulting value.
17248 The expression may include calls to functions in the program being
17252 @item call @var{expr}
17253 Evaluate the expression @var{expr} without displaying @code{void}
17256 You can use this variant of the @code{print} command if you want to
17257 execute a function from your program that does not return anything
17258 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17259 with @code{void} returned values that @value{GDBN} will otherwise
17260 print. If the result is not void, it is printed and saved in the
17264 It is possible for the function you call via the @code{print} or
17265 @code{call} command to generate a signal (e.g., if there's a bug in
17266 the function, or if you passed it incorrect arguments). What happens
17267 in that case is controlled by the @code{set unwindonsignal} command.
17269 Similarly, with a C@t{++} program it is possible for the function you
17270 call via the @code{print} or @code{call} command to generate an
17271 exception that is not handled due to the constraints of the dummy
17272 frame. In this case, any exception that is raised in the frame, but has
17273 an out-of-frame exception handler will not be found. GDB builds a
17274 dummy-frame for the inferior function call, and the unwinder cannot
17275 seek for exception handlers outside of this dummy-frame. What happens
17276 in that case is controlled by the
17277 @code{set unwind-on-terminating-exception} command.
17280 @item set unwindonsignal
17281 @kindex set unwindonsignal
17282 @cindex unwind stack in called functions
17283 @cindex call dummy stack unwinding
17284 Set unwinding of the stack if a signal is received while in a function
17285 that @value{GDBN} called in the program being debugged. If set to on,
17286 @value{GDBN} unwinds the stack it created for the call and restores
17287 the context to what it was before the call. If set to off (the
17288 default), @value{GDBN} stops in the frame where the signal was
17291 @item show unwindonsignal
17292 @kindex show unwindonsignal
17293 Show the current setting of stack unwinding in the functions called by
17296 @item set unwind-on-terminating-exception
17297 @kindex set unwind-on-terminating-exception
17298 @cindex unwind stack in called functions with unhandled exceptions
17299 @cindex call dummy stack unwinding on unhandled exception.
17300 Set unwinding of the stack if a C@t{++} exception is raised, but left
17301 unhandled while in a function that @value{GDBN} called in the program being
17302 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17303 it created for the call and restores the context to what it was before
17304 the call. If set to off, @value{GDBN} the exception is delivered to
17305 the default C@t{++} exception handler and the inferior terminated.
17307 @item show unwind-on-terminating-exception
17308 @kindex show unwind-on-terminating-exception
17309 Show the current setting of stack unwinding in the functions called by
17314 @cindex weak alias functions
17315 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17316 for another function. In such case, @value{GDBN} might not pick up
17317 the type information, including the types of the function arguments,
17318 which causes @value{GDBN} to call the inferior function incorrectly.
17319 As a result, the called function will function erroneously and may
17320 even crash. A solution to that is to use the name of the aliased
17324 @section Patching Programs
17326 @cindex patching binaries
17327 @cindex writing into executables
17328 @cindex writing into corefiles
17330 By default, @value{GDBN} opens the file containing your program's
17331 executable code (or the corefile) read-only. This prevents accidental
17332 alterations to machine code; but it also prevents you from intentionally
17333 patching your program's binary.
17335 If you'd like to be able to patch the binary, you can specify that
17336 explicitly with the @code{set write} command. For example, you might
17337 want to turn on internal debugging flags, or even to make emergency
17343 @itemx set write off
17344 If you specify @samp{set write on}, @value{GDBN} opens executable and
17345 core files for both reading and writing; if you specify @kbd{set write
17346 off} (the default), @value{GDBN} opens them read-only.
17348 If you have already loaded a file, you must load it again (using the
17349 @code{exec-file} or @code{core-file} command) after changing @code{set
17350 write}, for your new setting to take effect.
17354 Display whether executable files and core files are opened for writing
17355 as well as reading.
17358 @node Compiling and Injecting Code
17359 @section Compiling and injecting code in @value{GDBN}
17360 @cindex injecting code
17361 @cindex writing into executables
17362 @cindex compiling code
17364 @value{GDBN} supports on-demand compilation and code injection into
17365 programs running under @value{GDBN}. GCC 5.0 or higher built with
17366 @file{libcc1.so} must be installed for this functionality to be enabled.
17367 This functionality is implemented with the following commands.
17370 @kindex compile code
17371 @item compile code @var{source-code}
17372 @itemx compile code -raw @var{--} @var{source-code}
17373 Compile @var{source-code} with the compiler language found as the current
17374 language in @value{GDBN} (@pxref{Languages}). If compilation and
17375 injection is not supported with the current language specified in
17376 @value{GDBN}, or the compiler does not support this feature, an error
17377 message will be printed. If @var{source-code} compiles and links
17378 successfully, @value{GDBN} will load the object-code emitted,
17379 and execute it within the context of the currently selected inferior.
17380 It is important to note that the compiled code is executed immediately.
17381 After execution, the compiled code is removed from @value{GDBN} and any
17382 new types or variables you have defined will be deleted.
17384 The command allows you to specify @var{source-code} in two ways.
17385 The simplest method is to provide a single line of code to the command.
17389 compile code printf ("hello world\n");
17392 If you specify options on the command line as well as source code, they
17393 may conflict. The @samp{--} delimiter can be used to separate options
17394 from actual source code. E.g.:
17397 compile code -r -- printf ("hello world\n");
17400 Alternatively you can enter source code as multiple lines of text. To
17401 enter this mode, invoke the @samp{compile code} command without any text
17402 following the command. This will start the multiple-line editor and
17403 allow you to type as many lines of source code as required. When you
17404 have completed typing, enter @samp{end} on its own line to exit the
17409 >printf ("hello\n");
17410 >printf ("world\n");
17414 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17415 provided @var{source-code} in a callable scope. In this case, you must
17416 specify the entry point of the code by defining a function named
17417 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17418 inferior. Using @samp{-raw} option may be needed for example when
17419 @var{source-code} requires @samp{#include} lines which may conflict with
17420 inferior symbols otherwise.
17422 @kindex compile file
17423 @item compile file @var{filename}
17424 @itemx compile file -raw @var{filename}
17425 Like @code{compile code}, but take the source code from @var{filename}.
17428 compile file /home/user/example.c
17433 @item compile print @var{expr}
17434 @itemx compile print /@var{f} @var{expr}
17435 Compile and execute @var{expr} with the compiler language found as the
17436 current language in @value{GDBN} (@pxref{Languages}). By default the
17437 value of @var{expr} is printed in a format appropriate to its data type;
17438 you can choose a different format by specifying @samp{/@var{f}}, where
17439 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17442 @item compile print
17443 @itemx compile print /@var{f}
17444 @cindex reprint the last value
17445 Alternatively you can enter the expression (source code producing it) as
17446 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17447 command without any text following the command. This will start the
17448 multiple-line editor.
17452 The process of compiling and injecting the code can be inspected using:
17455 @anchor{set debug compile}
17456 @item set debug compile
17457 @cindex compile command debugging info
17458 Turns on or off display of @value{GDBN} process of compiling and
17459 injecting the code. The default is off.
17461 @item show debug compile
17462 Displays the current state of displaying @value{GDBN} process of
17463 compiling and injecting the code.
17466 @subsection Compilation options for the @code{compile} command
17468 @value{GDBN} needs to specify the right compilation options for the code
17469 to be injected, in part to make its ABI compatible with the inferior
17470 and in part to make the injected code compatible with @value{GDBN}'s
17474 The options used, in increasing precedence:
17477 @item target architecture and OS options (@code{gdbarch})
17478 These options depend on target processor type and target operating
17479 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17480 (@code{-m64}) compilation option.
17482 @item compilation options recorded in the target
17483 @value{NGCC} (since version 4.7) stores the options used for compilation
17484 into @code{DW_AT_producer} part of DWARF debugging information according
17485 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17486 explicitly specify @code{-g} during inferior compilation otherwise
17487 @value{NGCC} produces no DWARF. This feature is only relevant for
17488 platforms where @code{-g} produces DWARF by default, otherwise one may
17489 try to enforce DWARF by using @code{-gdwarf-4}.
17491 @item compilation options set by @code{set compile-args}
17495 You can override compilation options using the following command:
17498 @item set compile-args
17499 @cindex compile command options override
17500 Set compilation options used for compiling and injecting code with the
17501 @code{compile} commands. These options override any conflicting ones
17502 from the target architecture and/or options stored during inferior
17505 @item show compile-args
17506 Displays the current state of compilation options override.
17507 This does not show all the options actually used during compilation,
17508 use @ref{set debug compile} for that.
17511 @subsection Caveats when using the @code{compile} command
17513 There are a few caveats to keep in mind when using the @code{compile}
17514 command. As the caveats are different per language, the table below
17515 highlights specific issues on a per language basis.
17518 @item C code examples and caveats
17519 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17520 attempt to compile the source code with a @samp{C} compiler. The source
17521 code provided to the @code{compile} command will have much the same
17522 access to variables and types as it normally would if it were part of
17523 the program currently being debugged in @value{GDBN}.
17525 Below is a sample program that forms the basis of the examples that
17526 follow. This program has been compiled and loaded into @value{GDBN},
17527 much like any other normal debugging session.
17530 void function1 (void)
17533 printf ("function 1\n");
17536 void function2 (void)
17551 For the purposes of the examples in this section, the program above has
17552 been compiled, loaded into @value{GDBN}, stopped at the function
17553 @code{main}, and @value{GDBN} is awaiting input from the user.
17555 To access variables and types for any program in @value{GDBN}, the
17556 program must be compiled and packaged with debug information. The
17557 @code{compile} command is not an exception to this rule. Without debug
17558 information, you can still use the @code{compile} command, but you will
17559 be very limited in what variables and types you can access.
17561 So with that in mind, the example above has been compiled with debug
17562 information enabled. The @code{compile} command will have access to
17563 all variables and types (except those that may have been optimized
17564 out). Currently, as @value{GDBN} has stopped the program in the
17565 @code{main} function, the @code{compile} command would have access to
17566 the variable @code{k}. You could invoke the @code{compile} command
17567 and type some source code to set the value of @code{k}. You can also
17568 read it, or do anything with that variable you would normally do in
17569 @code{C}. Be aware that changes to inferior variables in the
17570 @code{compile} command are persistent. In the following example:
17573 compile code k = 3;
17577 the variable @code{k} is now 3. It will retain that value until
17578 something else in the example program changes it, or another
17579 @code{compile} command changes it.
17581 Normal scope and access rules apply to source code compiled and
17582 injected by the @code{compile} command. In the example, the variables
17583 @code{j} and @code{k} are not accessible yet, because the program is
17584 currently stopped in the @code{main} function, where these variables
17585 are not in scope. Therefore, the following command
17588 compile code j = 3;
17592 will result in a compilation error message.
17594 Once the program is continued, execution will bring these variables in
17595 scope, and they will become accessible; then the code you specify via
17596 the @code{compile} command will be able to access them.
17598 You can create variables and types with the @code{compile} command as
17599 part of your source code. Variables and types that are created as part
17600 of the @code{compile} command are not visible to the rest of the program for
17601 the duration of its run. This example is valid:
17604 compile code int ff = 5; printf ("ff is %d\n", ff);
17607 However, if you were to type the following into @value{GDBN} after that
17608 command has completed:
17611 compile code printf ("ff is %d\n'', ff);
17615 a compiler error would be raised as the variable @code{ff} no longer
17616 exists. Object code generated and injected by the @code{compile}
17617 command is removed when its execution ends. Caution is advised
17618 when assigning to program variables values of variables created by the
17619 code submitted to the @code{compile} command. This example is valid:
17622 compile code int ff = 5; k = ff;
17625 The value of the variable @code{ff} is assigned to @code{k}. The variable
17626 @code{k} does not require the existence of @code{ff} to maintain the value
17627 it has been assigned. However, pointers require particular care in
17628 assignment. If the source code compiled with the @code{compile} command
17629 changed the address of a pointer in the example program, perhaps to a
17630 variable created in the @code{compile} command, that pointer would point
17631 to an invalid location when the command exits. The following example
17632 would likely cause issues with your debugged program:
17635 compile code int ff = 5; p = &ff;
17638 In this example, @code{p} would point to @code{ff} when the
17639 @code{compile} command is executing the source code provided to it.
17640 However, as variables in the (example) program persist with their
17641 assigned values, the variable @code{p} would point to an invalid
17642 location when the command exists. A general rule should be followed
17643 in that you should either assign @code{NULL} to any assigned pointers,
17644 or restore a valid location to the pointer before the command exits.
17646 Similar caution must be exercised with any structs, unions, and typedefs
17647 defined in @code{compile} command. Types defined in the @code{compile}
17648 command will no longer be available in the next @code{compile} command.
17649 Therefore, if you cast a variable to a type defined in the
17650 @code{compile} command, care must be taken to ensure that any future
17651 need to resolve the type can be achieved.
17654 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17655 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17656 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17657 Compilation failed.
17658 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17662 Variables that have been optimized away by the compiler are not
17663 accessible to the code submitted to the @code{compile} command.
17664 Access to those variables will generate a compiler error which @value{GDBN}
17665 will print to the console.
17668 @subsection Compiler search for the @code{compile} command
17670 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
17671 may not be obvious for remote targets of different architecture than where
17672 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
17673 shell that executed @value{GDBN}, not the one set by @value{GDBN}
17674 command @code{set environment}). @xref{Environment}. @code{PATH} on
17675 @value{GDBN} host is searched for @value{NGCC} binary matching the
17676 target architecture and operating system.
17678 Specifically @code{PATH} is searched for binaries matching regular expression
17679 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
17680 debugged. @var{arch} is processor name --- multiarch is supported, so for
17681 example both @code{i386} and @code{x86_64} targets look for pattern
17682 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
17683 for pattern @code{s390x?}. @var{os} is currently supported only for
17684 pattern @code{linux(-gnu)?}.
17687 @chapter @value{GDBN} Files
17689 @value{GDBN} needs to know the file name of the program to be debugged,
17690 both in order to read its symbol table and in order to start your
17691 program. To debug a core dump of a previous run, you must also tell
17692 @value{GDBN} the name of the core dump file.
17695 * Files:: Commands to specify files
17696 * File Caching:: Information about @value{GDBN}'s file caching
17697 * Separate Debug Files:: Debugging information in separate files
17698 * MiniDebugInfo:: Debugging information in a special section
17699 * Index Files:: Index files speed up GDB
17700 * Symbol Errors:: Errors reading symbol files
17701 * Data Files:: GDB data files
17705 @section Commands to Specify Files
17707 @cindex symbol table
17708 @cindex core dump file
17710 You may want to specify executable and core dump file names. The usual
17711 way to do this is at start-up time, using the arguments to
17712 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17713 Out of @value{GDBN}}).
17715 Occasionally it is necessary to change to a different file during a
17716 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17717 specify a file you want to use. Or you are debugging a remote target
17718 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17719 Program}). In these situations the @value{GDBN} commands to specify
17720 new files are useful.
17723 @cindex executable file
17725 @item file @var{filename}
17726 Use @var{filename} as the program to be debugged. It is read for its
17727 symbols and for the contents of pure memory. It is also the program
17728 executed when you use the @code{run} command. If you do not specify a
17729 directory and the file is not found in the @value{GDBN} working directory,
17730 @value{GDBN} uses the environment variable @code{PATH} as a list of
17731 directories to search, just as the shell does when looking for a program
17732 to run. You can change the value of this variable, for both @value{GDBN}
17733 and your program, using the @code{path} command.
17735 @cindex unlinked object files
17736 @cindex patching object files
17737 You can load unlinked object @file{.o} files into @value{GDBN} using
17738 the @code{file} command. You will not be able to ``run'' an object
17739 file, but you can disassemble functions and inspect variables. Also,
17740 if the underlying BFD functionality supports it, you could use
17741 @kbd{gdb -write} to patch object files using this technique. Note
17742 that @value{GDBN} can neither interpret nor modify relocations in this
17743 case, so branches and some initialized variables will appear to go to
17744 the wrong place. But this feature is still handy from time to time.
17747 @code{file} with no argument makes @value{GDBN} discard any information it
17748 has on both executable file and the symbol table.
17751 @item exec-file @r{[} @var{filename} @r{]}
17752 Specify that the program to be run (but not the symbol table) is found
17753 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17754 if necessary to locate your program. Omitting @var{filename} means to
17755 discard information on the executable file.
17757 @kindex symbol-file
17758 @item symbol-file @r{[} @var{filename} @r{]}
17759 Read symbol table information from file @var{filename}. @code{PATH} is
17760 searched when necessary. Use the @code{file} command to get both symbol
17761 table and program to run from the same file.
17763 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17764 program's symbol table.
17766 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17767 some breakpoints and auto-display expressions. This is because they may
17768 contain pointers to the internal data recording symbols and data types,
17769 which are part of the old symbol table data being discarded inside
17772 @code{symbol-file} does not repeat if you press @key{RET} again after
17775 When @value{GDBN} is configured for a particular environment, it
17776 understands debugging information in whatever format is the standard
17777 generated for that environment; you may use either a @sc{gnu} compiler, or
17778 other compilers that adhere to the local conventions.
17779 Best results are usually obtained from @sc{gnu} compilers; for example,
17780 using @code{@value{NGCC}} you can generate debugging information for
17783 For most kinds of object files, with the exception of old SVR3 systems
17784 using COFF, the @code{symbol-file} command does not normally read the
17785 symbol table in full right away. Instead, it scans the symbol table
17786 quickly to find which source files and which symbols are present. The
17787 details are read later, one source file at a time, as they are needed.
17789 The purpose of this two-stage reading strategy is to make @value{GDBN}
17790 start up faster. For the most part, it is invisible except for
17791 occasional pauses while the symbol table details for a particular source
17792 file are being read. (The @code{set verbose} command can turn these
17793 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17794 Warnings and Messages}.)
17796 We have not implemented the two-stage strategy for COFF yet. When the
17797 symbol table is stored in COFF format, @code{symbol-file} reads the
17798 symbol table data in full right away. Note that ``stabs-in-COFF''
17799 still does the two-stage strategy, since the debug info is actually
17803 @cindex reading symbols immediately
17804 @cindex symbols, reading immediately
17805 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17806 @itemx file @r{[} -readnow @r{]} @var{filename}
17807 You can override the @value{GDBN} two-stage strategy for reading symbol
17808 tables by using the @samp{-readnow} option with any of the commands that
17809 load symbol table information, if you want to be sure @value{GDBN} has the
17810 entire symbol table available.
17812 @c FIXME: for now no mention of directories, since this seems to be in
17813 @c flux. 13mar1992 status is that in theory GDB would look either in
17814 @c current dir or in same dir as myprog; but issues like competing
17815 @c GDB's, or clutter in system dirs, mean that in practice right now
17816 @c only current dir is used. FFish says maybe a special GDB hierarchy
17817 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17821 @item core-file @r{[}@var{filename}@r{]}
17823 Specify the whereabouts of a core dump file to be used as the ``contents
17824 of memory''. Traditionally, core files contain only some parts of the
17825 address space of the process that generated them; @value{GDBN} can access the
17826 executable file itself for other parts.
17828 @code{core-file} with no argument specifies that no core file is
17831 Note that the core file is ignored when your program is actually running
17832 under @value{GDBN}. So, if you have been running your program and you
17833 wish to debug a core file instead, you must kill the subprocess in which
17834 the program is running. To do this, use the @code{kill} command
17835 (@pxref{Kill Process, ,Killing the Child Process}).
17837 @kindex add-symbol-file
17838 @cindex dynamic linking
17839 @item add-symbol-file @var{filename} @var{address}
17840 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17841 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17842 The @code{add-symbol-file} command reads additional symbol table
17843 information from the file @var{filename}. You would use this command
17844 when @var{filename} has been dynamically loaded (by some other means)
17845 into the program that is running. The @var{address} should give the memory
17846 address at which the file has been loaded; @value{GDBN} cannot figure
17847 this out for itself. You can additionally specify an arbitrary number
17848 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17849 section name and base address for that section. You can specify any
17850 @var{address} as an expression.
17852 The symbol table of the file @var{filename} is added to the symbol table
17853 originally read with the @code{symbol-file} command. You can use the
17854 @code{add-symbol-file} command any number of times; the new symbol data
17855 thus read is kept in addition to the old.
17857 Changes can be reverted using the command @code{remove-symbol-file}.
17859 @cindex relocatable object files, reading symbols from
17860 @cindex object files, relocatable, reading symbols from
17861 @cindex reading symbols from relocatable object files
17862 @cindex symbols, reading from relocatable object files
17863 @cindex @file{.o} files, reading symbols from
17864 Although @var{filename} is typically a shared library file, an
17865 executable file, or some other object file which has been fully
17866 relocated for loading into a process, you can also load symbolic
17867 information from relocatable @file{.o} files, as long as:
17871 the file's symbolic information refers only to linker symbols defined in
17872 that file, not to symbols defined by other object files,
17874 every section the file's symbolic information refers to has actually
17875 been loaded into the inferior, as it appears in the file, and
17877 you can determine the address at which every section was loaded, and
17878 provide these to the @code{add-symbol-file} command.
17882 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17883 relocatable files into an already running program; such systems
17884 typically make the requirements above easy to meet. However, it's
17885 important to recognize that many native systems use complex link
17886 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17887 assembly, for example) that make the requirements difficult to meet. In
17888 general, one cannot assume that using @code{add-symbol-file} to read a
17889 relocatable object file's symbolic information will have the same effect
17890 as linking the relocatable object file into the program in the normal
17893 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17895 @kindex remove-symbol-file
17896 @item remove-symbol-file @var{filename}
17897 @item remove-symbol-file -a @var{address}
17898 Remove a symbol file added via the @code{add-symbol-file} command. The
17899 file to remove can be identified by its @var{filename} or by an @var{address}
17900 that lies within the boundaries of this symbol file in memory. Example:
17903 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17904 add symbol table from file "/home/user/gdb/mylib.so" at
17905 .text_addr = 0x7ffff7ff9480
17907 Reading symbols from /home/user/gdb/mylib.so...done.
17908 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17909 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17914 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17916 @kindex add-symbol-file-from-memory
17917 @cindex @code{syscall DSO}
17918 @cindex load symbols from memory
17919 @item add-symbol-file-from-memory @var{address}
17920 Load symbols from the given @var{address} in a dynamically loaded
17921 object file whose image is mapped directly into the inferior's memory.
17922 For example, the Linux kernel maps a @code{syscall DSO} into each
17923 process's address space; this DSO provides kernel-specific code for
17924 some system calls. The argument can be any expression whose
17925 evaluation yields the address of the file's shared object file header.
17926 For this command to work, you must have used @code{symbol-file} or
17927 @code{exec-file} commands in advance.
17930 @item section @var{section} @var{addr}
17931 The @code{section} command changes the base address of the named
17932 @var{section} of the exec file to @var{addr}. This can be used if the
17933 exec file does not contain section addresses, (such as in the
17934 @code{a.out} format), or when the addresses specified in the file
17935 itself are wrong. Each section must be changed separately. The
17936 @code{info files} command, described below, lists all the sections and
17940 @kindex info target
17943 @code{info files} and @code{info target} are synonymous; both print the
17944 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17945 including the names of the executable and core dump files currently in
17946 use by @value{GDBN}, and the files from which symbols were loaded. The
17947 command @code{help target} lists all possible targets rather than
17950 @kindex maint info sections
17951 @item maint info sections
17952 Another command that can give you extra information about program sections
17953 is @code{maint info sections}. In addition to the section information
17954 displayed by @code{info files}, this command displays the flags and file
17955 offset of each section in the executable and core dump files. In addition,
17956 @code{maint info sections} provides the following command options (which
17957 may be arbitrarily combined):
17961 Display sections for all loaded object files, including shared libraries.
17962 @item @var{sections}
17963 Display info only for named @var{sections}.
17964 @item @var{section-flags}
17965 Display info only for sections for which @var{section-flags} are true.
17966 The section flags that @value{GDBN} currently knows about are:
17969 Section will have space allocated in the process when loaded.
17970 Set for all sections except those containing debug information.
17972 Section will be loaded from the file into the child process memory.
17973 Set for pre-initialized code and data, clear for @code{.bss} sections.
17975 Section needs to be relocated before loading.
17977 Section cannot be modified by the child process.
17979 Section contains executable code only.
17981 Section contains data only (no executable code).
17983 Section will reside in ROM.
17985 Section contains data for constructor/destructor lists.
17987 Section is not empty.
17989 An instruction to the linker to not output the section.
17990 @item COFF_SHARED_LIBRARY
17991 A notification to the linker that the section contains
17992 COFF shared library information.
17994 Section contains common symbols.
17997 @kindex set trust-readonly-sections
17998 @cindex read-only sections
17999 @item set trust-readonly-sections on
18000 Tell @value{GDBN} that readonly sections in your object file
18001 really are read-only (i.e.@: that their contents will not change).
18002 In that case, @value{GDBN} can fetch values from these sections
18003 out of the object file, rather than from the target program.
18004 For some targets (notably embedded ones), this can be a significant
18005 enhancement to debugging performance.
18007 The default is off.
18009 @item set trust-readonly-sections off
18010 Tell @value{GDBN} not to trust readonly sections. This means that
18011 the contents of the section might change while the program is running,
18012 and must therefore be fetched from the target when needed.
18014 @item show trust-readonly-sections
18015 Show the current setting of trusting readonly sections.
18018 All file-specifying commands allow both absolute and relative file names
18019 as arguments. @value{GDBN} always converts the file name to an absolute file
18020 name and remembers it that way.
18022 @cindex shared libraries
18023 @anchor{Shared Libraries}
18024 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
18025 and IBM RS/6000 AIX shared libraries.
18027 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18028 shared libraries. @xref{Expat}.
18030 @value{GDBN} automatically loads symbol definitions from shared libraries
18031 when you use the @code{run} command, or when you examine a core file.
18032 (Before you issue the @code{run} command, @value{GDBN} does not understand
18033 references to a function in a shared library, however---unless you are
18034 debugging a core file).
18036 On HP-UX, if the program loads a library explicitly, @value{GDBN}
18037 automatically loads the symbols at the time of the @code{shl_load} call.
18039 @c FIXME: some @value{GDBN} release may permit some refs to undef
18040 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18041 @c FIXME...lib; check this from time to time when updating manual
18043 There are times, however, when you may wish to not automatically load
18044 symbol definitions from shared libraries, such as when they are
18045 particularly large or there are many of them.
18047 To control the automatic loading of shared library symbols, use the
18051 @kindex set auto-solib-add
18052 @item set auto-solib-add @var{mode}
18053 If @var{mode} is @code{on}, symbols from all shared object libraries
18054 will be loaded automatically when the inferior begins execution, you
18055 attach to an independently started inferior, or when the dynamic linker
18056 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18057 is @code{off}, symbols must be loaded manually, using the
18058 @code{sharedlibrary} command. The default value is @code{on}.
18060 @cindex memory used for symbol tables
18061 If your program uses lots of shared libraries with debug info that
18062 takes large amounts of memory, you can decrease the @value{GDBN}
18063 memory footprint by preventing it from automatically loading the
18064 symbols from shared libraries. To that end, type @kbd{set
18065 auto-solib-add off} before running the inferior, then load each
18066 library whose debug symbols you do need with @kbd{sharedlibrary
18067 @var{regexp}}, where @var{regexp} is a regular expression that matches
18068 the libraries whose symbols you want to be loaded.
18070 @kindex show auto-solib-add
18071 @item show auto-solib-add
18072 Display the current autoloading mode.
18075 @cindex load shared library
18076 To explicitly load shared library symbols, use the @code{sharedlibrary}
18080 @kindex info sharedlibrary
18082 @item info share @var{regex}
18083 @itemx info sharedlibrary @var{regex}
18084 Print the names of the shared libraries which are currently loaded
18085 that match @var{regex}. If @var{regex} is omitted then print
18086 all shared libraries that are loaded.
18089 @item info dll @var{regex}
18090 This is an alias of @code{info sharedlibrary}.
18092 @kindex sharedlibrary
18094 @item sharedlibrary @var{regex}
18095 @itemx share @var{regex}
18096 Load shared object library symbols for files matching a
18097 Unix regular expression.
18098 As with files loaded automatically, it only loads shared libraries
18099 required by your program for a core file or after typing @code{run}. If
18100 @var{regex} is omitted all shared libraries required by your program are
18103 @item nosharedlibrary
18104 @kindex nosharedlibrary
18105 @cindex unload symbols from shared libraries
18106 Unload all shared object library symbols. This discards all symbols
18107 that have been loaded from all shared libraries. Symbols from shared
18108 libraries that were loaded by explicit user requests are not
18112 Sometimes you may wish that @value{GDBN} stops and gives you control
18113 when any of shared library events happen. The best way to do this is
18114 to use @code{catch load} and @code{catch unload} (@pxref{Set
18117 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18118 command for this. This command exists for historical reasons. It is
18119 less useful than setting a catchpoint, because it does not allow for
18120 conditions or commands as a catchpoint does.
18123 @item set stop-on-solib-events
18124 @kindex set stop-on-solib-events
18125 This command controls whether @value{GDBN} should give you control
18126 when the dynamic linker notifies it about some shared library event.
18127 The most common event of interest is loading or unloading of a new
18130 @item show stop-on-solib-events
18131 @kindex show stop-on-solib-events
18132 Show whether @value{GDBN} stops and gives you control when shared
18133 library events happen.
18136 Shared libraries are also supported in many cross or remote debugging
18137 configurations. @value{GDBN} needs to have access to the target's libraries;
18138 this can be accomplished either by providing copies of the libraries
18139 on the host system, or by asking @value{GDBN} to automatically retrieve the
18140 libraries from the target. If copies of the target libraries are
18141 provided, they need to be the same as the target libraries, although the
18142 copies on the target can be stripped as long as the copies on the host are
18145 @cindex where to look for shared libraries
18146 For remote debugging, you need to tell @value{GDBN} where the target
18147 libraries are, so that it can load the correct copies---otherwise, it
18148 may try to load the host's libraries. @value{GDBN} has two variables
18149 to specify the search directories for target libraries.
18152 @cindex prefix for executable and shared library file names
18153 @cindex system root, alternate
18154 @kindex set solib-absolute-prefix
18155 @kindex set sysroot
18156 @item set sysroot @var{path}
18157 Use @var{path} as the system root for the program being debugged. Any
18158 absolute shared library paths will be prefixed with @var{path}; many
18159 runtime loaders store the absolute paths to the shared library in the
18160 target program's memory. When starting processes remotely, and when
18161 attaching to already-running processes (local or remote), their
18162 executable filenames will be prefixed with @var{path} if reported to
18163 @value{GDBN} as absolute by the operating system. If you use
18164 @code{set sysroot} to find executables and shared libraries, they need
18165 to be laid out in the same way that they are on the target, with
18166 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18169 If @var{path} starts with the sequence @file{target:} and the target
18170 system is remote then @value{GDBN} will retrieve the target binaries
18171 from the remote system. This is only supported when using a remote
18172 target that supports the @code{remote get} command (@pxref{File
18173 Transfer,,Sending files to a remote system}). The part of @var{path}
18174 following the initial @file{target:} (if present) is used as system
18175 root prefix on the remote file system. If @var{path} starts with the
18176 sequence @file{remote:} this is converted to the sequence
18177 @file{target:} by @code{set sysroot}@footnote{Historically the
18178 functionality to retrieve binaries from the remote system was
18179 provided by prefixing @var{path} with @file{remote:}}. If you want
18180 to specify a local system root using a directory that happens to be
18181 named @file{target:} or @file{remote:}, you need to use some
18182 equivalent variant of the name like @file{./target:}.
18184 For targets with an MS-DOS based filesystem, such as MS-Windows and
18185 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18186 absolute file name with @var{path}. But first, on Unix hosts,
18187 @value{GDBN} converts all backslash directory separators into forward
18188 slashes, because the backslash is not a directory separator on Unix:
18191 c:\foo\bar.dll @result{} c:/foo/bar.dll
18194 Then, @value{GDBN} attempts prefixing the target file name with
18195 @var{path}, and looks for the resulting file name in the host file
18199 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18202 If that does not find the binary, @value{GDBN} tries removing
18203 the @samp{:} character from the drive spec, both for convenience, and,
18204 for the case of the host file system not supporting file names with
18208 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18211 This makes it possible to have a system root that mirrors a target
18212 with more than one drive. E.g., you may want to setup your local
18213 copies of the target system shared libraries like so (note @samp{c} vs
18217 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18218 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18219 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18223 and point the system root at @file{/path/to/sysroot}, so that
18224 @value{GDBN} can find the correct copies of both
18225 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18227 If that still does not find the binary, @value{GDBN} tries
18228 removing the whole drive spec from the target file name:
18231 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18234 This last lookup makes it possible to not care about the drive name,
18235 if you don't want or need to.
18237 The @code{set solib-absolute-prefix} command is an alias for @code{set
18240 @cindex default system root
18241 @cindex @samp{--with-sysroot}
18242 You can set the default system root by using the configure-time
18243 @samp{--with-sysroot} option. If the system root is inside
18244 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18245 @samp{--exec-prefix}), then the default system root will be updated
18246 automatically if the installed @value{GDBN} is moved to a new
18249 @kindex show sysroot
18251 Display the current executable and shared library prefix.
18253 @kindex set solib-search-path
18254 @item set solib-search-path @var{path}
18255 If this variable is set, @var{path} is a colon-separated list of
18256 directories to search for shared libraries. @samp{solib-search-path}
18257 is used after @samp{sysroot} fails to locate the library, or if the
18258 path to the library is relative instead of absolute. If you want to
18259 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18260 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18261 finding your host's libraries. @samp{sysroot} is preferred; setting
18262 it to a nonexistent directory may interfere with automatic loading
18263 of shared library symbols.
18265 @kindex show solib-search-path
18266 @item show solib-search-path
18267 Display the current shared library search path.
18269 @cindex DOS file-name semantics of file names.
18270 @kindex set target-file-system-kind (unix|dos-based|auto)
18271 @kindex show target-file-system-kind
18272 @item set target-file-system-kind @var{kind}
18273 Set assumed file system kind for target reported file names.
18275 Shared library file names as reported by the target system may not
18276 make sense as is on the system @value{GDBN} is running on. For
18277 example, when remote debugging a target that has MS-DOS based file
18278 system semantics, from a Unix host, the target may be reporting to
18279 @value{GDBN} a list of loaded shared libraries with file names such as
18280 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18281 drive letters, so the @samp{c:\} prefix is not normally understood as
18282 indicating an absolute file name, and neither is the backslash
18283 normally considered a directory separator character. In that case,
18284 the native file system would interpret this whole absolute file name
18285 as a relative file name with no directory components. This would make
18286 it impossible to point @value{GDBN} at a copy of the remote target's
18287 shared libraries on the host using @code{set sysroot}, and impractical
18288 with @code{set solib-search-path}. Setting
18289 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18290 to interpret such file names similarly to how the target would, and to
18291 map them to file names valid on @value{GDBN}'s native file system
18292 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18293 to one of the supported file system kinds. In that case, @value{GDBN}
18294 tries to determine the appropriate file system variant based on the
18295 current target's operating system (@pxref{ABI, ,Configuring the
18296 Current ABI}). The supported file system settings are:
18300 Instruct @value{GDBN} to assume the target file system is of Unix
18301 kind. Only file names starting the forward slash (@samp{/}) character
18302 are considered absolute, and the directory separator character is also
18306 Instruct @value{GDBN} to assume the target file system is DOS based.
18307 File names starting with either a forward slash, or a drive letter
18308 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18309 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18310 considered directory separators.
18313 Instruct @value{GDBN} to use the file system kind associated with the
18314 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18315 This is the default.
18319 @cindex file name canonicalization
18320 @cindex base name differences
18321 When processing file names provided by the user, @value{GDBN}
18322 frequently needs to compare them to the file names recorded in the
18323 program's debug info. Normally, @value{GDBN} compares just the
18324 @dfn{base names} of the files as strings, which is reasonably fast
18325 even for very large programs. (The base name of a file is the last
18326 portion of its name, after stripping all the leading directories.)
18327 This shortcut in comparison is based upon the assumption that files
18328 cannot have more than one base name. This is usually true, but
18329 references to files that use symlinks or similar filesystem
18330 facilities violate that assumption. If your program records files
18331 using such facilities, or if you provide file names to @value{GDBN}
18332 using symlinks etc., you can set @code{basenames-may-differ} to
18333 @code{true} to instruct @value{GDBN} to completely canonicalize each
18334 pair of file names it needs to compare. This will make file-name
18335 comparisons accurate, but at a price of a significant slowdown.
18338 @item set basenames-may-differ
18339 @kindex set basenames-may-differ
18340 Set whether a source file may have multiple base names.
18342 @item show basenames-may-differ
18343 @kindex show basenames-may-differ
18344 Show whether a source file may have multiple base names.
18348 @section File Caching
18349 @cindex caching of opened files
18350 @cindex caching of bfd objects
18352 To speed up file loading, and reduce memory usage, @value{GDBN} will
18353 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18354 BFD, bfd, The Binary File Descriptor Library}. The following commands
18355 allow visibility and control of the caching behavior.
18358 @kindex maint info bfds
18359 @item maint info bfds
18360 This prints information about each @code{bfd} object that is known to
18363 @kindex maint set bfd-sharing
18364 @kindex maint show bfd-sharing
18365 @kindex bfd caching
18366 @item maint set bfd-sharing
18367 @item maint show bfd-sharing
18368 Control whether @code{bfd} objects can be shared. When sharing is
18369 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18370 than reopening the same file. Turning sharing off does not cause
18371 already shared @code{bfd} objects to be unshared, but all future files
18372 that are opened will create a new @code{bfd} object. Similarly,
18373 re-enabling sharing does not cause multiple existing @code{bfd}
18374 objects to be collapsed into a single shared @code{bfd} object.
18376 @kindex set debug bfd-cache @var{level}
18377 @kindex bfd caching
18378 @item set debug bfd-cache @var{level}
18379 Turns on debugging of the bfd cache, setting the level to @var{level}.
18381 @kindex show debug bfd-cache
18382 @kindex bfd caching
18383 @item show debug bfd-cache
18384 Show the current debugging level of the bfd cache.
18387 @node Separate Debug Files
18388 @section Debugging Information in Separate Files
18389 @cindex separate debugging information files
18390 @cindex debugging information in separate files
18391 @cindex @file{.debug} subdirectories
18392 @cindex debugging information directory, global
18393 @cindex global debugging information directories
18394 @cindex build ID, and separate debugging files
18395 @cindex @file{.build-id} directory
18397 @value{GDBN} allows you to put a program's debugging information in a
18398 file separate from the executable itself, in a way that allows
18399 @value{GDBN} to find and load the debugging information automatically.
18400 Since debugging information can be very large---sometimes larger
18401 than the executable code itself---some systems distribute debugging
18402 information for their executables in separate files, which users can
18403 install only when they need to debug a problem.
18405 @value{GDBN} supports two ways of specifying the separate debug info
18410 The executable contains a @dfn{debug link} that specifies the name of
18411 the separate debug info file. The separate debug file's name is
18412 usually @file{@var{executable}.debug}, where @var{executable} is the
18413 name of the corresponding executable file without leading directories
18414 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18415 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18416 checksum for the debug file, which @value{GDBN} uses to validate that
18417 the executable and the debug file came from the same build.
18420 The executable contains a @dfn{build ID}, a unique bit string that is
18421 also present in the corresponding debug info file. (This is supported
18422 only on some operating systems, when using the ELF or PE file formats
18423 for binary files and the @sc{gnu} Binutils.) For more details about
18424 this feature, see the description of the @option{--build-id}
18425 command-line option in @ref{Options, , Command Line Options, ld.info,
18426 The GNU Linker}. The debug info file's name is not specified
18427 explicitly by the build ID, but can be computed from the build ID, see
18431 Depending on the way the debug info file is specified, @value{GDBN}
18432 uses two different methods of looking for the debug file:
18436 For the ``debug link'' method, @value{GDBN} looks up the named file in
18437 the directory of the executable file, then in a subdirectory of that
18438 directory named @file{.debug}, and finally under each one of the global debug
18439 directories, in a subdirectory whose name is identical to the leading
18440 directories of the executable's absolute file name.
18443 For the ``build ID'' method, @value{GDBN} looks in the
18444 @file{.build-id} subdirectory of each one of the global debug directories for
18445 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18446 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18447 are the rest of the bit string. (Real build ID strings are 32 or more
18448 hex characters, not 10.)
18451 So, for example, suppose you ask @value{GDBN} to debug
18452 @file{/usr/bin/ls}, which has a debug link that specifies the
18453 file @file{ls.debug}, and a build ID whose value in hex is
18454 @code{abcdef1234}. If the list of the global debug directories includes
18455 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18456 debug information files, in the indicated order:
18460 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18462 @file{/usr/bin/ls.debug}
18464 @file{/usr/bin/.debug/ls.debug}
18466 @file{/usr/lib/debug/usr/bin/ls.debug}.
18469 @anchor{debug-file-directory}
18470 Global debugging info directories default to what is set by @value{GDBN}
18471 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18472 you can also set the global debugging info directories, and view the list
18473 @value{GDBN} is currently using.
18477 @kindex set debug-file-directory
18478 @item set debug-file-directory @var{directories}
18479 Set the directories which @value{GDBN} searches for separate debugging
18480 information files to @var{directory}. Multiple path components can be set
18481 concatenating them by a path separator.
18483 @kindex show debug-file-directory
18484 @item show debug-file-directory
18485 Show the directories @value{GDBN} searches for separate debugging
18490 @cindex @code{.gnu_debuglink} sections
18491 @cindex debug link sections
18492 A debug link is a special section of the executable file named
18493 @code{.gnu_debuglink}. The section must contain:
18497 A filename, with any leading directory components removed, followed by
18500 zero to three bytes of padding, as needed to reach the next four-byte
18501 boundary within the section, and
18503 a four-byte CRC checksum, stored in the same endianness used for the
18504 executable file itself. The checksum is computed on the debugging
18505 information file's full contents by the function given below, passing
18506 zero as the @var{crc} argument.
18509 Any executable file format can carry a debug link, as long as it can
18510 contain a section named @code{.gnu_debuglink} with the contents
18513 @cindex @code{.note.gnu.build-id} sections
18514 @cindex build ID sections
18515 The build ID is a special section in the executable file (and in other
18516 ELF binary files that @value{GDBN} may consider). This section is
18517 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18518 It contains unique identification for the built files---the ID remains
18519 the same across multiple builds of the same build tree. The default
18520 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18521 content for the build ID string. The same section with an identical
18522 value is present in the original built binary with symbols, in its
18523 stripped variant, and in the separate debugging information file.
18525 The debugging information file itself should be an ordinary
18526 executable, containing a full set of linker symbols, sections, and
18527 debugging information. The sections of the debugging information file
18528 should have the same names, addresses, and sizes as the original file,
18529 but they need not contain any data---much like a @code{.bss} section
18530 in an ordinary executable.
18532 The @sc{gnu} binary utilities (Binutils) package includes the
18533 @samp{objcopy} utility that can produce
18534 the separated executable / debugging information file pairs using the
18535 following commands:
18538 @kbd{objcopy --only-keep-debug foo foo.debug}
18543 These commands remove the debugging
18544 information from the executable file @file{foo} and place it in the file
18545 @file{foo.debug}. You can use the first, second or both methods to link the
18550 The debug link method needs the following additional command to also leave
18551 behind a debug link in @file{foo}:
18554 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18557 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18558 a version of the @code{strip} command such that the command @kbd{strip foo -f
18559 foo.debug} has the same functionality as the two @code{objcopy} commands and
18560 the @code{ln -s} command above, together.
18563 Build ID gets embedded into the main executable using @code{ld --build-id} or
18564 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18565 compatibility fixes for debug files separation are present in @sc{gnu} binary
18566 utilities (Binutils) package since version 2.18.
18571 @cindex CRC algorithm definition
18572 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18573 IEEE 802.3 using the polynomial:
18575 @c TexInfo requires naked braces for multi-digit exponents for Tex
18576 @c output, but this causes HTML output to barf. HTML has to be set using
18577 @c raw commands. So we end up having to specify this equation in 2
18582 <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>
18583 + <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
18589 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18590 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18594 The function is computed byte at a time, taking the least
18595 significant bit of each byte first. The initial pattern
18596 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18597 the final result is inverted to ensure trailing zeros also affect the
18600 @emph{Note:} This is the same CRC polynomial as used in handling the
18601 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18602 However in the case of the Remote Serial Protocol, the CRC is computed
18603 @emph{most} significant bit first, and the result is not inverted, so
18604 trailing zeros have no effect on the CRC value.
18606 To complete the description, we show below the code of the function
18607 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18608 initially supplied @code{crc} argument means that an initial call to
18609 this function passing in zero will start computing the CRC using
18612 @kindex gnu_debuglink_crc32
18615 gnu_debuglink_crc32 (unsigned long crc,
18616 unsigned char *buf, size_t len)
18618 static const unsigned long crc32_table[256] =
18620 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18621 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18622 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18623 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18624 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18625 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18626 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18627 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18628 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18629 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18630 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18631 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18632 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18633 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18634 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18635 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18636 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18637 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18638 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18639 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18640 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18641 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18642 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18643 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18644 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18645 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18646 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18647 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18648 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18649 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18650 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18651 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18652 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18653 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18654 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18655 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18656 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18657 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18658 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18659 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18660 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18661 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18662 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18663 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18664 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18665 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18666 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18667 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18668 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18669 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18670 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18673 unsigned char *end;
18675 crc = ~crc & 0xffffffff;
18676 for (end = buf + len; buf < end; ++buf)
18677 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18678 return ~crc & 0xffffffff;
18683 This computation does not apply to the ``build ID'' method.
18685 @node MiniDebugInfo
18686 @section Debugging information in a special section
18687 @cindex separate debug sections
18688 @cindex @samp{.gnu_debugdata} section
18690 Some systems ship pre-built executables and libraries that have a
18691 special @samp{.gnu_debugdata} section. This feature is called
18692 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18693 is used to supply extra symbols for backtraces.
18695 The intent of this section is to provide extra minimal debugging
18696 information for use in simple backtraces. It is not intended to be a
18697 replacement for full separate debugging information (@pxref{Separate
18698 Debug Files}). The example below shows the intended use; however,
18699 @value{GDBN} does not currently put restrictions on what sort of
18700 debugging information might be included in the section.
18702 @value{GDBN} has support for this extension. If the section exists,
18703 then it is used provided that no other source of debugging information
18704 can be found, and that @value{GDBN} was configured with LZMA support.
18706 This section can be easily created using @command{objcopy} and other
18707 standard utilities:
18710 # Extract the dynamic symbols from the main binary, there is no need
18711 # to also have these in the normal symbol table.
18712 nm -D @var{binary} --format=posix --defined-only \
18713 | awk '@{ print $1 @}' | sort > dynsyms
18715 # Extract all the text (i.e. function) symbols from the debuginfo.
18716 # (Note that we actually also accept "D" symbols, for the benefit
18717 # of platforms like PowerPC64 that use function descriptors.)
18718 nm @var{binary} --format=posix --defined-only \
18719 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18722 # Keep all the function symbols not already in the dynamic symbol
18724 comm -13 dynsyms funcsyms > keep_symbols
18726 # Separate full debug info into debug binary.
18727 objcopy --only-keep-debug @var{binary} debug
18729 # Copy the full debuginfo, keeping only a minimal set of symbols and
18730 # removing some unnecessary sections.
18731 objcopy -S --remove-section .gdb_index --remove-section .comment \
18732 --keep-symbols=keep_symbols debug mini_debuginfo
18734 # Drop the full debug info from the original binary.
18735 strip --strip-all -R .comment @var{binary}
18737 # Inject the compressed data into the .gnu_debugdata section of the
18740 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18744 @section Index Files Speed Up @value{GDBN}
18745 @cindex index files
18746 @cindex @samp{.gdb_index} section
18748 When @value{GDBN} finds a symbol file, it scans the symbols in the
18749 file in order to construct an internal symbol table. This lets most
18750 @value{GDBN} operations work quickly---at the cost of a delay early
18751 on. For large programs, this delay can be quite lengthy, so
18752 @value{GDBN} provides a way to build an index, which speeds up
18755 The index is stored as a section in the symbol file. @value{GDBN} can
18756 write the index to a file, then you can put it into the symbol file
18757 using @command{objcopy}.
18759 To create an index file, use the @code{save gdb-index} command:
18762 @item save gdb-index @var{directory}
18763 @kindex save gdb-index
18764 Create an index file for each symbol file currently known by
18765 @value{GDBN}. Each file is named after its corresponding symbol file,
18766 with @samp{.gdb-index} appended, and is written into the given
18770 Once you have created an index file you can merge it into your symbol
18771 file, here named @file{symfile}, using @command{objcopy}:
18774 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18775 --set-section-flags .gdb_index=readonly symfile symfile
18778 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18779 sections that have been deprecated. Usually they are deprecated because
18780 they are missing a new feature or have performance issues.
18781 To tell @value{GDBN} to use a deprecated index section anyway
18782 specify @code{set use-deprecated-index-sections on}.
18783 The default is @code{off}.
18784 This can speed up startup, but may result in some functionality being lost.
18785 @xref{Index Section Format}.
18787 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18788 must be done before gdb reads the file. The following will not work:
18791 $ gdb -ex "set use-deprecated-index-sections on" <program>
18794 Instead you must do, for example,
18797 $ gdb -iex "set use-deprecated-index-sections on" <program>
18800 There are currently some limitation on indices. They only work when
18801 for DWARF debugging information, not stabs. And, they do not
18802 currently work for programs using Ada.
18804 @node Symbol Errors
18805 @section Errors Reading Symbol Files
18807 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18808 such as symbol types it does not recognize, or known bugs in compiler
18809 output. By default, @value{GDBN} does not notify you of such problems, since
18810 they are relatively common and primarily of interest to people
18811 debugging compilers. If you are interested in seeing information
18812 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18813 only one message about each such type of problem, no matter how many
18814 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18815 to see how many times the problems occur, with the @code{set
18816 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18819 The messages currently printed, and their meanings, include:
18822 @item inner block not inside outer block in @var{symbol}
18824 The symbol information shows where symbol scopes begin and end
18825 (such as at the start of a function or a block of statements). This
18826 error indicates that an inner scope block is not fully contained
18827 in its outer scope blocks.
18829 @value{GDBN} circumvents the problem by treating the inner block as if it had
18830 the same scope as the outer block. In the error message, @var{symbol}
18831 may be shown as ``@code{(don't know)}'' if the outer block is not a
18834 @item block at @var{address} out of order
18836 The symbol information for symbol scope blocks should occur in
18837 order of increasing addresses. This error indicates that it does not
18840 @value{GDBN} does not circumvent this problem, and has trouble
18841 locating symbols in the source file whose symbols it is reading. (You
18842 can often determine what source file is affected by specifying
18843 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18846 @item bad block start address patched
18848 The symbol information for a symbol scope block has a start address
18849 smaller than the address of the preceding source line. This is known
18850 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18852 @value{GDBN} circumvents the problem by treating the symbol scope block as
18853 starting on the previous source line.
18855 @item bad string table offset in symbol @var{n}
18858 Symbol number @var{n} contains a pointer into the string table which is
18859 larger than the size of the string table.
18861 @value{GDBN} circumvents the problem by considering the symbol to have the
18862 name @code{foo}, which may cause other problems if many symbols end up
18865 @item unknown symbol type @code{0x@var{nn}}
18867 The symbol information contains new data types that @value{GDBN} does
18868 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18869 uncomprehended information, in hexadecimal.
18871 @value{GDBN} circumvents the error by ignoring this symbol information.
18872 This usually allows you to debug your program, though certain symbols
18873 are not accessible. If you encounter such a problem and feel like
18874 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18875 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18876 and examine @code{*bufp} to see the symbol.
18878 @item stub type has NULL name
18880 @value{GDBN} could not find the full definition for a struct or class.
18882 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18883 The symbol information for a C@t{++} member function is missing some
18884 information that recent versions of the compiler should have output for
18887 @item info mismatch between compiler and debugger
18889 @value{GDBN} could not parse a type specification output by the compiler.
18894 @section GDB Data Files
18896 @cindex prefix for data files
18897 @value{GDBN} will sometimes read an auxiliary data file. These files
18898 are kept in a directory known as the @dfn{data directory}.
18900 You can set the data directory's name, and view the name @value{GDBN}
18901 is currently using.
18904 @kindex set data-directory
18905 @item set data-directory @var{directory}
18906 Set the directory which @value{GDBN} searches for auxiliary data files
18907 to @var{directory}.
18909 @kindex show data-directory
18910 @item show data-directory
18911 Show the directory @value{GDBN} searches for auxiliary data files.
18914 @cindex default data directory
18915 @cindex @samp{--with-gdb-datadir}
18916 You can set the default data directory by using the configure-time
18917 @samp{--with-gdb-datadir} option. If the data directory is inside
18918 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18919 @samp{--exec-prefix}), then the default data directory will be updated
18920 automatically if the installed @value{GDBN} is moved to a new
18923 The data directory may also be specified with the
18924 @code{--data-directory} command line option.
18925 @xref{Mode Options}.
18928 @chapter Specifying a Debugging Target
18930 @cindex debugging target
18931 A @dfn{target} is the execution environment occupied by your program.
18933 Often, @value{GDBN} runs in the same host environment as your program;
18934 in that case, the debugging target is specified as a side effect when
18935 you use the @code{file} or @code{core} commands. When you need more
18936 flexibility---for example, running @value{GDBN} on a physically separate
18937 host, or controlling a standalone system over a serial port or a
18938 realtime system over a TCP/IP connection---you can use the @code{target}
18939 command to specify one of the target types configured for @value{GDBN}
18940 (@pxref{Target Commands, ,Commands for Managing Targets}).
18942 @cindex target architecture
18943 It is possible to build @value{GDBN} for several different @dfn{target
18944 architectures}. When @value{GDBN} is built like that, you can choose
18945 one of the available architectures with the @kbd{set architecture}
18949 @kindex set architecture
18950 @kindex show architecture
18951 @item set architecture @var{arch}
18952 This command sets the current target architecture to @var{arch}. The
18953 value of @var{arch} can be @code{"auto"}, in addition to one of the
18954 supported architectures.
18956 @item show architecture
18957 Show the current target architecture.
18959 @item set processor
18961 @kindex set processor
18962 @kindex show processor
18963 These are alias commands for, respectively, @code{set architecture}
18964 and @code{show architecture}.
18968 * Active Targets:: Active targets
18969 * Target Commands:: Commands for managing targets
18970 * Byte Order:: Choosing target byte order
18973 @node Active Targets
18974 @section Active Targets
18976 @cindex stacking targets
18977 @cindex active targets
18978 @cindex multiple targets
18980 There are multiple classes of targets such as: processes, executable files or
18981 recording sessions. Core files belong to the process class, making core file
18982 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
18983 on multiple active targets, one in each class. This allows you to (for
18984 example) start a process and inspect its activity, while still having access to
18985 the executable file after the process finishes. Or if you start process
18986 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
18987 presented a virtual layer of the recording target, while the process target
18988 remains stopped at the chronologically last point of the process execution.
18990 Use the @code{core-file} and @code{exec-file} commands to select a new core
18991 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
18992 specify as a target a process that is already running, use the @code{attach}
18993 command (@pxref{Attach, ,Debugging an Already-running Process}).
18995 @node Target Commands
18996 @section Commands for Managing Targets
18999 @item target @var{type} @var{parameters}
19000 Connects the @value{GDBN} host environment to a target machine or
19001 process. A target is typically a protocol for talking to debugging
19002 facilities. You use the argument @var{type} to specify the type or
19003 protocol of the target machine.
19005 Further @var{parameters} are interpreted by the target protocol, but
19006 typically include things like device names or host names to connect
19007 with, process numbers, and baud rates.
19009 The @code{target} command does not repeat if you press @key{RET} again
19010 after executing the command.
19012 @kindex help target
19014 Displays the names of all targets available. To display targets
19015 currently selected, use either @code{info target} or @code{info files}
19016 (@pxref{Files, ,Commands to Specify Files}).
19018 @item help target @var{name}
19019 Describe a particular target, including any parameters necessary to
19022 @kindex set gnutarget
19023 @item set gnutarget @var{args}
19024 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19025 knows whether it is reading an @dfn{executable},
19026 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19027 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19028 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19031 @emph{Warning:} To specify a file format with @code{set gnutarget},
19032 you must know the actual BFD name.
19036 @xref{Files, , Commands to Specify Files}.
19038 @kindex show gnutarget
19039 @item show gnutarget
19040 Use the @code{show gnutarget} command to display what file format
19041 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19042 @value{GDBN} will determine the file format for each file automatically,
19043 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19046 @cindex common targets
19047 Here are some common targets (available, or not, depending on the GDB
19052 @item target exec @var{program}
19053 @cindex executable file target
19054 An executable file. @samp{target exec @var{program}} is the same as
19055 @samp{exec-file @var{program}}.
19057 @item target core @var{filename}
19058 @cindex core dump file target
19059 A core dump file. @samp{target core @var{filename}} is the same as
19060 @samp{core-file @var{filename}}.
19062 @item target remote @var{medium}
19063 @cindex remote target
19064 A remote system connected to @value{GDBN} via a serial line or network
19065 connection. This command tells @value{GDBN} to use its own remote
19066 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19068 For example, if you have a board connected to @file{/dev/ttya} on the
19069 machine running @value{GDBN}, you could say:
19072 target remote /dev/ttya
19075 @code{target remote} supports the @code{load} command. This is only
19076 useful if you have some other way of getting the stub to the target
19077 system, and you can put it somewhere in memory where it won't get
19078 clobbered by the download.
19080 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19081 @cindex built-in simulator target
19082 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19090 works; however, you cannot assume that a specific memory map, device
19091 drivers, or even basic I/O is available, although some simulators do
19092 provide these. For info about any processor-specific simulator details,
19093 see the appropriate section in @ref{Embedded Processors, ,Embedded
19096 @item target native
19097 @cindex native target
19098 Setup for local/native process debugging. Useful to make the
19099 @code{run} command spawn native processes (likewise @code{attach},
19100 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19101 (@pxref{set auto-connect-native-target}).
19105 Different targets are available on different configurations of @value{GDBN};
19106 your configuration may have more or fewer targets.
19108 Many remote targets require you to download the executable's code once
19109 you've successfully established a connection. You may wish to control
19110 various aspects of this process.
19115 @kindex set hash@r{, for remote monitors}
19116 @cindex hash mark while downloading
19117 This command controls whether a hash mark @samp{#} is displayed while
19118 downloading a file to the remote monitor. If on, a hash mark is
19119 displayed after each S-record is successfully downloaded to the
19123 @kindex show hash@r{, for remote monitors}
19124 Show the current status of displaying the hash mark.
19126 @item set debug monitor
19127 @kindex set debug monitor
19128 @cindex display remote monitor communications
19129 Enable or disable display of communications messages between
19130 @value{GDBN} and the remote monitor.
19132 @item show debug monitor
19133 @kindex show debug monitor
19134 Show the current status of displaying communications between
19135 @value{GDBN} and the remote monitor.
19140 @kindex load @var{filename}
19141 @item load @var{filename}
19143 Depending on what remote debugging facilities are configured into
19144 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19145 is meant to make @var{filename} (an executable) available for debugging
19146 on the remote system---by downloading, or dynamic linking, for example.
19147 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19148 the @code{add-symbol-file} command.
19150 If your @value{GDBN} does not have a @code{load} command, attempting to
19151 execute it gets the error message ``@code{You can't do that when your
19152 target is @dots{}}''
19154 The file is loaded at whatever address is specified in the executable.
19155 For some object file formats, you can specify the load address when you
19156 link the program; for other formats, like a.out, the object file format
19157 specifies a fixed address.
19158 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19160 Depending on the remote side capabilities, @value{GDBN} may be able to
19161 load programs into flash memory.
19163 @code{load} does not repeat if you press @key{RET} again after using it.
19167 @section Choosing Target Byte Order
19169 @cindex choosing target byte order
19170 @cindex target byte order
19172 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19173 offer the ability to run either big-endian or little-endian byte
19174 orders. Usually the executable or symbol will include a bit to
19175 designate the endian-ness, and you will not need to worry about
19176 which to use. However, you may still find it useful to adjust
19177 @value{GDBN}'s idea of processor endian-ness manually.
19181 @item set endian big
19182 Instruct @value{GDBN} to assume the target is big-endian.
19184 @item set endian little
19185 Instruct @value{GDBN} to assume the target is little-endian.
19187 @item set endian auto
19188 Instruct @value{GDBN} to use the byte order associated with the
19192 Display @value{GDBN}'s current idea of the target byte order.
19196 Note that these commands merely adjust interpretation of symbolic
19197 data on the host, and that they have absolutely no effect on the
19201 @node Remote Debugging
19202 @chapter Debugging Remote Programs
19203 @cindex remote debugging
19205 If you are trying to debug a program running on a machine that cannot run
19206 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19207 For example, you might use remote debugging on an operating system kernel,
19208 or on a small system which does not have a general purpose operating system
19209 powerful enough to run a full-featured debugger.
19211 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19212 to make this work with particular debugging targets. In addition,
19213 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19214 but not specific to any particular target system) which you can use if you
19215 write the remote stubs---the code that runs on the remote system to
19216 communicate with @value{GDBN}.
19218 Other remote targets may be available in your
19219 configuration of @value{GDBN}; use @code{help target} to list them.
19222 * Connecting:: Connecting to a remote target
19223 * File Transfer:: Sending files to a remote system
19224 * Server:: Using the gdbserver program
19225 * Remote Configuration:: Remote configuration
19226 * Remote Stub:: Implementing a remote stub
19230 @section Connecting to a Remote Target
19232 @value{GDBN} needs an unstripped copy of your program to access symbol
19233 and debugging information. Some remote targets (@pxref{qXfer
19234 executable filename read}, and @pxref{Host I/O Packets}) allow
19235 @value{GDBN} to access program files over the same connection used to
19236 communicate with @value{GDBN}. With such a target, if the remote
19237 program is unstripped, the only command you need is @code{target
19238 remote}. Otherwise, start up @value{GDBN} using the name of the local
19239 unstripped copy of your program as the first argument, or use the
19240 @code{file} command.
19242 @cindex @code{target remote}
19243 @value{GDBN} can communicate with the target over a serial line, or
19244 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19245 each case, @value{GDBN} uses the same protocol for debugging your
19246 program; only the medium carrying the debugging packets varies. The
19247 @code{target remote} command establishes a connection to the target.
19248 Its arguments indicate which medium to use:
19252 @item target remote @var{serial-device}
19253 @cindex serial line, @code{target remote}
19254 Use @var{serial-device} to communicate with the target. For example,
19255 to use a serial line connected to the device named @file{/dev/ttyb}:
19258 target remote /dev/ttyb
19261 If you're using a serial line, you may want to give @value{GDBN} the
19262 @samp{--baud} option, or use the @code{set serial baud} command
19263 (@pxref{Remote Configuration, set serial baud}) before the
19264 @code{target} command.
19266 @item target remote @code{@var{host}:@var{port}}
19267 @itemx target remote @code{tcp:@var{host}:@var{port}}
19268 @cindex @acronym{TCP} port, @code{target remote}
19269 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19270 The @var{host} may be either a host name or a numeric @acronym{IP}
19271 address; @var{port} must be a decimal number. The @var{host} could be
19272 the target machine itself, if it is directly connected to the net, or
19273 it might be a terminal server which in turn has a serial line to the
19276 For example, to connect to port 2828 on a terminal server named
19280 target remote manyfarms:2828
19283 If your remote target is actually running on the same machine as your
19284 debugger session (e.g.@: a simulator for your target running on the
19285 same host), you can omit the hostname. For example, to connect to
19286 port 1234 on your local machine:
19289 target remote :1234
19293 Note that the colon is still required here.
19295 @item target remote @code{udp:@var{host}:@var{port}}
19296 @cindex @acronym{UDP} port, @code{target remote}
19297 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19298 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19301 target remote udp:manyfarms:2828
19304 When using a @acronym{UDP} connection for remote debugging, you should
19305 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19306 can silently drop packets on busy or unreliable networks, which will
19307 cause havoc with your debugging session.
19309 @item target remote | @var{command}
19310 @cindex pipe, @code{target remote} to
19311 Run @var{command} in the background and communicate with it using a
19312 pipe. The @var{command} is a shell command, to be parsed and expanded
19313 by the system's command shell, @code{/bin/sh}; it should expect remote
19314 protocol packets on its standard input, and send replies on its
19315 standard output. You could use this to run a stand-alone simulator
19316 that speaks the remote debugging protocol, to make net connections
19317 using programs like @code{ssh}, or for other similar tricks.
19319 If @var{command} closes its standard output (perhaps by exiting),
19320 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19321 program has already exited, this will have no effect.)
19325 Once the connection has been established, you can use all the usual
19326 commands to examine and change data. The remote program is already
19327 running; you can use @kbd{step} and @kbd{continue}, and you do not
19328 need to use @kbd{run}.
19330 @cindex interrupting remote programs
19331 @cindex remote programs, interrupting
19332 Whenever @value{GDBN} is waiting for the remote program, if you type the
19333 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19334 program. This may or may not succeed, depending in part on the hardware
19335 and the serial drivers the remote system uses. If you type the
19336 interrupt character once again, @value{GDBN} displays this prompt:
19339 Interrupted while waiting for the program.
19340 Give up (and stop debugging it)? (y or n)
19343 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
19344 (If you decide you want to try again later, you can use @samp{target
19345 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
19346 goes back to waiting.
19349 @kindex detach (remote)
19351 When you have finished debugging the remote program, you can use the
19352 @code{detach} command to release it from @value{GDBN} control.
19353 Detaching from the target normally resumes its execution, but the results
19354 will depend on your particular remote stub. After the @code{detach}
19355 command, @value{GDBN} is free to connect to another target.
19359 The @code{disconnect} command behaves like @code{detach}, except that
19360 the target is generally not resumed. It will wait for @value{GDBN}
19361 (this instance or another one) to connect and continue debugging. After
19362 the @code{disconnect} command, @value{GDBN} is again free to connect to
19365 @cindex send command to remote monitor
19366 @cindex extend @value{GDBN} for remote targets
19367 @cindex add new commands for external monitor
19369 @item monitor @var{cmd}
19370 This command allows you to send arbitrary commands directly to the
19371 remote monitor. Since @value{GDBN} doesn't care about the commands it
19372 sends like this, this command is the way to extend @value{GDBN}---you
19373 can add new commands that only the external monitor will understand
19377 @node File Transfer
19378 @section Sending files to a remote system
19379 @cindex remote target, file transfer
19380 @cindex file transfer
19381 @cindex sending files to remote systems
19383 Some remote targets offer the ability to transfer files over the same
19384 connection used to communicate with @value{GDBN}. This is convenient
19385 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19386 running @code{gdbserver} over a network interface. For other targets,
19387 e.g.@: embedded devices with only a single serial port, this may be
19388 the only way to upload or download files.
19390 Not all remote targets support these commands.
19394 @item remote put @var{hostfile} @var{targetfile}
19395 Copy file @var{hostfile} from the host system (the machine running
19396 @value{GDBN}) to @var{targetfile} on the target system.
19399 @item remote get @var{targetfile} @var{hostfile}
19400 Copy file @var{targetfile} from the target system to @var{hostfile}
19401 on the host system.
19403 @kindex remote delete
19404 @item remote delete @var{targetfile}
19405 Delete @var{targetfile} from the target system.
19410 @section Using the @code{gdbserver} Program
19413 @cindex remote connection without stubs
19414 @code{gdbserver} is a control program for Unix-like systems, which
19415 allows you to connect your program with a remote @value{GDBN} via
19416 @code{target remote}---but without linking in the usual debugging stub.
19418 @code{gdbserver} is not a complete replacement for the debugging stubs,
19419 because it requires essentially the same operating-system facilities
19420 that @value{GDBN} itself does. In fact, a system that can run
19421 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19422 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19423 because it is a much smaller program than @value{GDBN} itself. It is
19424 also easier to port than all of @value{GDBN}, so you may be able to get
19425 started more quickly on a new system by using @code{gdbserver}.
19426 Finally, if you develop code for real-time systems, you may find that
19427 the tradeoffs involved in real-time operation make it more convenient to
19428 do as much development work as possible on another system, for example
19429 by cross-compiling. You can use @code{gdbserver} to make a similar
19430 choice for debugging.
19432 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19433 or a TCP connection, using the standard @value{GDBN} remote serial
19437 @emph{Warning:} @code{gdbserver} does not have any built-in security.
19438 Do not run @code{gdbserver} connected to any public network; a
19439 @value{GDBN} connection to @code{gdbserver} provides access to the
19440 target system with the same privileges as the user running
19444 @subsection Running @code{gdbserver}
19445 @cindex arguments, to @code{gdbserver}
19446 @cindex @code{gdbserver}, command-line arguments
19448 Run @code{gdbserver} on the target system. You need a copy of the
19449 program you want to debug, including any libraries it requires.
19450 @code{gdbserver} does not need your program's symbol table, so you can
19451 strip the program if necessary to save space. @value{GDBN} on the host
19452 system does all the symbol handling.
19454 To use the server, you must tell it how to communicate with @value{GDBN};
19455 the name of your program; and the arguments for your program. The usual
19459 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
19462 @var{comm} is either a device name (to use a serial line), or a TCP
19463 hostname and portnumber, or @code{-} or @code{stdio} to use
19464 stdin/stdout of @code{gdbserver}.
19465 For example, to debug Emacs with the argument
19466 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
19470 target> gdbserver /dev/com1 emacs foo.txt
19473 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
19476 To use a TCP connection instead of a serial line:
19479 target> gdbserver host:2345 emacs foo.txt
19482 The only difference from the previous example is the first argument,
19483 specifying that you are communicating with the host @value{GDBN} via
19484 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
19485 expect a TCP connection from machine @samp{host} to local TCP port 2345.
19486 (Currently, the @samp{host} part is ignored.) You can choose any number
19487 you want for the port number as long as it does not conflict with any
19488 TCP ports already in use on the target system (for example, @code{23} is
19489 reserved for @code{telnet}).@footnote{If you choose a port number that
19490 conflicts with another service, @code{gdbserver} prints an error message
19491 and exits.} You must use the same port number with the host @value{GDBN}
19492 @code{target remote} command.
19494 The @code{stdio} connection is useful when starting @code{gdbserver}
19498 (gdb) target remote | ssh -T hostname gdbserver - hello
19501 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19502 and we don't want escape-character handling. Ssh does this by default when
19503 a command is provided, the flag is provided to make it explicit.
19504 You could elide it if you want to.
19506 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19507 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19508 display through a pipe connected to gdbserver.
19509 Both @code{stdout} and @code{stderr} use the same pipe.
19511 @subsubsection Attaching to a Running Program
19512 @cindex attach to a program, @code{gdbserver}
19513 @cindex @option{--attach}, @code{gdbserver} option
19515 On some targets, @code{gdbserver} can also attach to running programs.
19516 This is accomplished via the @code{--attach} argument. The syntax is:
19519 target> gdbserver --attach @var{comm} @var{pid}
19522 @var{pid} is the process ID of a currently running process. It isn't necessary
19523 to point @code{gdbserver} at a binary for the running process.
19526 You can debug processes by name instead of process ID if your target has the
19527 @code{pidof} utility:
19530 target> gdbserver --attach @var{comm} `pidof @var{program}`
19533 In case more than one copy of @var{program} is running, or @var{program}
19534 has multiple threads, most versions of @code{pidof} support the
19535 @code{-s} option to only return the first process ID.
19537 @subsubsection Multi-Process Mode for @code{gdbserver}
19538 @cindex @code{gdbserver}, multiple processes
19539 @cindex multiple processes with @code{gdbserver}
19541 When you connect to @code{gdbserver} using @code{target remote},
19542 @code{gdbserver} debugs the specified program only once. When the
19543 program exits, or you detach from it, @value{GDBN} closes the connection
19544 and @code{gdbserver} exits.
19546 If you connect using @kbd{target extended-remote}, @code{gdbserver}
19547 enters multi-process mode. When the debugged program exits, or you
19548 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
19549 though no program is running. The @code{run} and @code{attach}
19550 commands instruct @code{gdbserver} to run or attach to a new program.
19551 The @code{run} command uses @code{set remote exec-file} (@pxref{set
19552 remote exec-file}) to select the program to run. Command line
19553 arguments are supported, except for wildcard expansion and I/O
19554 redirection (@pxref{Arguments}).
19556 @cindex @option{--multi}, @code{gdbserver} option
19557 To start @code{gdbserver} without supplying an initial command to run
19558 or process ID to attach, use the @option{--multi} command line option.
19559 Then you can connect using @kbd{target extended-remote} and start
19560 the program you want to debug.
19562 In multi-process mode @code{gdbserver} does not automatically exit unless you
19563 use the option @option{--once}. You can terminate it by using
19564 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
19565 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
19566 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
19567 @option{--multi} option to @code{gdbserver} has no influence on that.
19569 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19571 This section applies only when @code{gdbserver} is run to listen on a TCP port.
19573 @code{gdbserver} normally terminates after all of its debugged processes have
19574 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19575 extended-remote}, @code{gdbserver} stays running even with no processes left.
19576 @value{GDBN} normally terminates the spawned debugged process on its exit,
19577 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19578 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19579 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19580 stays running even in the @kbd{target remote} mode.
19582 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19583 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19584 completeness, at most one @value{GDBN} can be connected at a time.
19586 @cindex @option{--once}, @code{gdbserver} option
19587 By default, @code{gdbserver} keeps the listening TCP port open, so that
19588 subsequent connections are possible. However, if you start @code{gdbserver}
19589 with the @option{--once} option, it will stop listening for any further
19590 connection attempts after connecting to the first @value{GDBN} session. This
19591 means no further connections to @code{gdbserver} will be possible after the
19592 first one. It also means @code{gdbserver} will terminate after the first
19593 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19594 connections and even in the @kbd{target extended-remote} mode. The
19595 @option{--once} option allows reusing the same port number for connecting to
19596 multiple instances of @code{gdbserver} running on the same host, since each
19597 instance closes its port after the first connection.
19599 @anchor{Other Command-Line Arguments for gdbserver}
19600 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19602 @cindex @option{--debug}, @code{gdbserver} option
19603 The @option{--debug} option tells @code{gdbserver} to display extra
19604 status information about the debugging process.
19605 @cindex @option{--remote-debug}, @code{gdbserver} option
19606 The @option{--remote-debug} option tells @code{gdbserver} to display
19607 remote protocol debug output. These options are intended for
19608 @code{gdbserver} development and for bug reports to the developers.
19610 @cindex @option{--debug-format}, @code{gdbserver} option
19611 The @option{--debug-format=option1[,option2,...]} option tells
19612 @code{gdbserver} to include additional information in each output.
19613 Possible options are:
19617 Turn off all extra information in debugging output.
19619 Turn on all extra information in debugging output.
19621 Include a timestamp in each line of debugging output.
19624 Options are processed in order. Thus, for example, if @option{none}
19625 appears last then no additional information is added to debugging output.
19627 @cindex @option{--wrapper}, @code{gdbserver} option
19628 The @option{--wrapper} option specifies a wrapper to launch programs
19629 for debugging. The option should be followed by the name of the
19630 wrapper, then any command-line arguments to pass to the wrapper, then
19631 @kbd{--} indicating the end of the wrapper arguments.
19633 @code{gdbserver} runs the specified wrapper program with a combined
19634 command line including the wrapper arguments, then the name of the
19635 program to debug, then any arguments to the program. The wrapper
19636 runs until it executes your program, and then @value{GDBN} gains control.
19638 You can use any program that eventually calls @code{execve} with
19639 its arguments as a wrapper. Several standard Unix utilities do
19640 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19641 with @code{exec "$@@"} will also work.
19643 For example, you can use @code{env} to pass an environment variable to
19644 the debugged program, without setting the variable in @code{gdbserver}'s
19648 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19651 @subsection Connecting to @code{gdbserver}
19653 Run @value{GDBN} on the host system.
19655 First make sure you have the necessary symbol files. Load symbols for
19656 your application using the @code{file} command before you connect. Use
19657 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
19658 was compiled with the correct sysroot using @code{--with-sysroot}).
19660 The symbol file and target libraries must exactly match the executable
19661 and libraries on the target, with one exception: the files on the host
19662 system should not be stripped, even if the files on the target system
19663 are. Mismatched or missing files will lead to confusing results
19664 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19665 files may also prevent @code{gdbserver} from debugging multi-threaded
19668 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19669 For TCP connections, you must start up @code{gdbserver} prior to using
19670 the @code{target remote} command. Otherwise you may get an error whose
19671 text depends on the host system, but which usually looks something like
19672 @samp{Connection refused}. Don't use the @code{load}
19673 command in @value{GDBN} when using @code{gdbserver}, since the program is
19674 already on the target.
19676 @subsection Monitor Commands for @code{gdbserver}
19677 @cindex monitor commands, for @code{gdbserver}
19678 @anchor{Monitor Commands for gdbserver}
19680 During a @value{GDBN} session using @code{gdbserver}, you can use the
19681 @code{monitor} command to send special requests to @code{gdbserver}.
19682 Here are the available commands.
19686 List the available monitor commands.
19688 @item monitor set debug 0
19689 @itemx monitor set debug 1
19690 Disable or enable general debugging messages.
19692 @item monitor set remote-debug 0
19693 @itemx monitor set remote-debug 1
19694 Disable or enable specific debugging messages associated with the remote
19695 protocol (@pxref{Remote Protocol}).
19697 @item monitor set debug-format option1@r{[},option2,...@r{]}
19698 Specify additional text to add to debugging messages.
19699 Possible options are:
19703 Turn off all extra information in debugging output.
19705 Turn on all extra information in debugging output.
19707 Include a timestamp in each line of debugging output.
19710 Options are processed in order. Thus, for example, if @option{none}
19711 appears last then no additional information is added to debugging output.
19713 @item monitor set libthread-db-search-path [PATH]
19714 @cindex gdbserver, search path for @code{libthread_db}
19715 When this command is issued, @var{path} is a colon-separated list of
19716 directories to search for @code{libthread_db} (@pxref{Threads,,set
19717 libthread-db-search-path}). If you omit @var{path},
19718 @samp{libthread-db-search-path} will be reset to its default value.
19720 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19721 not supported in @code{gdbserver}.
19724 Tell gdbserver to exit immediately. This command should be followed by
19725 @code{disconnect} to close the debugging session. @code{gdbserver} will
19726 detach from any attached processes and kill any processes it created.
19727 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19728 of a multi-process mode debug session.
19732 @subsection Tracepoints support in @code{gdbserver}
19733 @cindex tracepoints support in @code{gdbserver}
19735 On some targets, @code{gdbserver} supports tracepoints, fast
19736 tracepoints and static tracepoints.
19738 For fast or static tracepoints to work, a special library called the
19739 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19740 This library is built and distributed as an integral part of
19741 @code{gdbserver}. In addition, support for static tracepoints
19742 requires building the in-process agent library with static tracepoints
19743 support. At present, the UST (LTTng Userspace Tracer,
19744 @url{http://lttng.org/ust}) tracing engine is supported. This support
19745 is automatically available if UST development headers are found in the
19746 standard include path when @code{gdbserver} is built, or if
19747 @code{gdbserver} was explicitly configured using @option{--with-ust}
19748 to point at such headers. You can explicitly disable the support
19749 using @option{--with-ust=no}.
19751 There are several ways to load the in-process agent in your program:
19754 @item Specifying it as dependency at link time
19756 You can link your program dynamically with the in-process agent
19757 library. On most systems, this is accomplished by adding
19758 @code{-linproctrace} to the link command.
19760 @item Using the system's preloading mechanisms
19762 You can force loading the in-process agent at startup time by using
19763 your system's support for preloading shared libraries. Many Unixes
19764 support the concept of preloading user defined libraries. In most
19765 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19766 in the environment. See also the description of @code{gdbserver}'s
19767 @option{--wrapper} command line option.
19769 @item Using @value{GDBN} to force loading the agent at run time
19771 On some systems, you can force the inferior to load a shared library,
19772 by calling a dynamic loader function in the inferior that takes care
19773 of dynamically looking up and loading a shared library. On most Unix
19774 systems, the function is @code{dlopen}. You'll use the @code{call}
19775 command for that. For example:
19778 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19781 Note that on most Unix systems, for the @code{dlopen} function to be
19782 available, the program needs to be linked with @code{-ldl}.
19785 On systems that have a userspace dynamic loader, like most Unix
19786 systems, when you connect to @code{gdbserver} using @code{target
19787 remote}, you'll find that the program is stopped at the dynamic
19788 loader's entry point, and no shared library has been loaded in the
19789 program's address space yet, including the in-process agent. In that
19790 case, before being able to use any of the fast or static tracepoints
19791 features, you need to let the loader run and load the shared
19792 libraries. The simplest way to do that is to run the program to the
19793 main procedure. E.g., if debugging a C or C@t{++} program, start
19794 @code{gdbserver} like so:
19797 $ gdbserver :9999 myprogram
19800 Start GDB and connect to @code{gdbserver} like so, and run to main:
19804 (@value{GDBP}) target remote myhost:9999
19805 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
19806 (@value{GDBP}) b main
19807 (@value{GDBP}) continue
19810 The in-process tracing agent library should now be loaded into the
19811 process; you can confirm it with the @code{info sharedlibrary}
19812 command, which will list @file{libinproctrace.so} as loaded in the
19813 process. You are now ready to install fast tracepoints, list static
19814 tracepoint markers, probe static tracepoints markers, and start
19817 @node Remote Configuration
19818 @section Remote Configuration
19821 @kindex show remote
19822 This section documents the configuration options available when
19823 debugging remote programs. For the options related to the File I/O
19824 extensions of the remote protocol, see @ref{system,
19825 system-call-allowed}.
19828 @item set remoteaddresssize @var{bits}
19829 @cindex address size for remote targets
19830 @cindex bits in remote address
19831 Set the maximum size of address in a memory packet to the specified
19832 number of bits. @value{GDBN} will mask off the address bits above
19833 that number, when it passes addresses to the remote target. The
19834 default value is the number of bits in the target's address.
19836 @item show remoteaddresssize
19837 Show the current value of remote address size in bits.
19839 @item set serial baud @var{n}
19840 @cindex baud rate for remote targets
19841 Set the baud rate for the remote serial I/O to @var{n} baud. The
19842 value is used to set the speed of the serial port used for debugging
19845 @item show serial baud
19846 Show the current speed of the remote connection.
19848 @item set serial parity @var{parity}
19849 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
19850 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
19852 @item show serial parity
19853 Show the current parity of the serial port.
19855 @item set remotebreak
19856 @cindex interrupt remote programs
19857 @cindex BREAK signal instead of Ctrl-C
19858 @anchor{set remotebreak}
19859 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19860 when you type @kbd{Ctrl-c} to interrupt the program running
19861 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19862 character instead. The default is off, since most remote systems
19863 expect to see @samp{Ctrl-C} as the interrupt signal.
19865 @item show remotebreak
19866 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19867 interrupt the remote program.
19869 @item set remoteflow on
19870 @itemx set remoteflow off
19871 @kindex set remoteflow
19872 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
19873 on the serial port used to communicate to the remote target.
19875 @item show remoteflow
19876 @kindex show remoteflow
19877 Show the current setting of hardware flow control.
19879 @item set remotelogbase @var{base}
19880 Set the base (a.k.a.@: radix) of logging serial protocol
19881 communications to @var{base}. Supported values of @var{base} are:
19882 @code{ascii}, @code{octal}, and @code{hex}. The default is
19885 @item show remotelogbase
19886 Show the current setting of the radix for logging remote serial
19889 @item set remotelogfile @var{file}
19890 @cindex record serial communications on file
19891 Record remote serial communications on the named @var{file}. The
19892 default is not to record at all.
19894 @item show remotelogfile.
19895 Show the current setting of the file name on which to record the
19896 serial communications.
19898 @item set remotetimeout @var{num}
19899 @cindex timeout for serial communications
19900 @cindex remote timeout
19901 Set the timeout limit to wait for the remote target to respond to
19902 @var{num} seconds. The default is 2 seconds.
19904 @item show remotetimeout
19905 Show the current number of seconds to wait for the remote target
19908 @cindex limit hardware breakpoints and watchpoints
19909 @cindex remote target, limit break- and watchpoints
19910 @anchor{set remote hardware-watchpoint-limit}
19911 @anchor{set remote hardware-breakpoint-limit}
19912 @item set remote hardware-watchpoint-limit @var{limit}
19913 @itemx set remote hardware-breakpoint-limit @var{limit}
19914 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
19915 watchpoints. A limit of -1, the default, is treated as unlimited.
19917 @cindex limit hardware watchpoints length
19918 @cindex remote target, limit watchpoints length
19919 @anchor{set remote hardware-watchpoint-length-limit}
19920 @item set remote hardware-watchpoint-length-limit @var{limit}
19921 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
19922 a remote hardware watchpoint. A limit of -1, the default, is treated
19925 @item show remote hardware-watchpoint-length-limit
19926 Show the current limit (in bytes) of the maximum length of
19927 a remote hardware watchpoint.
19929 @item set remote exec-file @var{filename}
19930 @itemx show remote exec-file
19931 @anchor{set remote exec-file}
19932 @cindex executable file, for remote target
19933 Select the file used for @code{run} with @code{target
19934 extended-remote}. This should be set to a filename valid on the
19935 target system. If it is not set, the target will use a default
19936 filename (e.g.@: the last program run).
19938 @item set remote interrupt-sequence
19939 @cindex interrupt remote programs
19940 @cindex select Ctrl-C, BREAK or BREAK-g
19941 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
19942 @samp{BREAK-g} as the
19943 sequence to the remote target in order to interrupt the execution.
19944 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
19945 is high level of serial line for some certain time.
19946 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
19947 It is @code{BREAK} signal followed by character @code{g}.
19949 @item show interrupt-sequence
19950 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
19951 is sent by @value{GDBN} to interrupt the remote program.
19952 @code{BREAK-g} is BREAK signal followed by @code{g} and
19953 also known as Magic SysRq g.
19955 @item set remote interrupt-on-connect
19956 @cindex send interrupt-sequence on start
19957 Specify whether interrupt-sequence is sent to remote target when
19958 @value{GDBN} connects to it. This is mostly needed when you debug
19959 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
19960 which is known as Magic SysRq g in order to connect @value{GDBN}.
19962 @item show interrupt-on-connect
19963 Show whether interrupt-sequence is sent
19964 to remote target when @value{GDBN} connects to it.
19968 @item set tcp auto-retry on
19969 @cindex auto-retry, for remote TCP target
19970 Enable auto-retry for remote TCP connections. This is useful if the remote
19971 debugging agent is launched in parallel with @value{GDBN}; there is a race
19972 condition because the agent may not become ready to accept the connection
19973 before @value{GDBN} attempts to connect. When auto-retry is
19974 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
19975 to establish the connection using the timeout specified by
19976 @code{set tcp connect-timeout}.
19978 @item set tcp auto-retry off
19979 Do not auto-retry failed TCP connections.
19981 @item show tcp auto-retry
19982 Show the current auto-retry setting.
19984 @item set tcp connect-timeout @var{seconds}
19985 @itemx set tcp connect-timeout unlimited
19986 @cindex connection timeout, for remote TCP target
19987 @cindex timeout, for remote target connection
19988 Set the timeout for establishing a TCP connection to the remote target to
19989 @var{seconds}. The timeout affects both polling to retry failed connections
19990 (enabled by @code{set tcp auto-retry on}) and waiting for connections
19991 that are merely slow to complete, and represents an approximate cumulative
19992 value. If @var{seconds} is @code{unlimited}, there is no timeout and
19993 @value{GDBN} will keep attempting to establish a connection forever,
19994 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
19996 @item show tcp connect-timeout
19997 Show the current connection timeout setting.
20000 @cindex remote packets, enabling and disabling
20001 The @value{GDBN} remote protocol autodetects the packets supported by
20002 your debugging stub. If you need to override the autodetection, you
20003 can use these commands to enable or disable individual packets. Each
20004 packet can be set to @samp{on} (the remote target supports this
20005 packet), @samp{off} (the remote target does not support this packet),
20006 or @samp{auto} (detect remote target support for this packet). They
20007 all default to @samp{auto}. For more information about each packet,
20008 see @ref{Remote Protocol}.
20010 During normal use, you should not have to use any of these commands.
20011 If you do, that may be a bug in your remote debugging stub, or a bug
20012 in @value{GDBN}. You may want to report the problem to the
20013 @value{GDBN} developers.
20015 For each packet @var{name}, the command to enable or disable the
20016 packet is @code{set remote @var{name}-packet}. The available settings
20019 @multitable @columnfractions 0.28 0.32 0.25
20022 @tab Related Features
20024 @item @code{fetch-register}
20026 @tab @code{info registers}
20028 @item @code{set-register}
20032 @item @code{binary-download}
20034 @tab @code{load}, @code{set}
20036 @item @code{read-aux-vector}
20037 @tab @code{qXfer:auxv:read}
20038 @tab @code{info auxv}
20040 @item @code{symbol-lookup}
20041 @tab @code{qSymbol}
20042 @tab Detecting multiple threads
20044 @item @code{attach}
20045 @tab @code{vAttach}
20048 @item @code{verbose-resume}
20050 @tab Stepping or resuming multiple threads
20056 @item @code{software-breakpoint}
20060 @item @code{hardware-breakpoint}
20064 @item @code{write-watchpoint}
20068 @item @code{read-watchpoint}
20072 @item @code{access-watchpoint}
20076 @item @code{pid-to-exec-file}
20077 @tab @code{qXfer:exec-file:read}
20078 @tab @code{attach}, @code{run}
20080 @item @code{target-features}
20081 @tab @code{qXfer:features:read}
20082 @tab @code{set architecture}
20084 @item @code{library-info}
20085 @tab @code{qXfer:libraries:read}
20086 @tab @code{info sharedlibrary}
20088 @item @code{memory-map}
20089 @tab @code{qXfer:memory-map:read}
20090 @tab @code{info mem}
20092 @item @code{read-sdata-object}
20093 @tab @code{qXfer:sdata:read}
20094 @tab @code{print $_sdata}
20096 @item @code{read-spu-object}
20097 @tab @code{qXfer:spu:read}
20098 @tab @code{info spu}
20100 @item @code{write-spu-object}
20101 @tab @code{qXfer:spu:write}
20102 @tab @code{info spu}
20104 @item @code{read-siginfo-object}
20105 @tab @code{qXfer:siginfo:read}
20106 @tab @code{print $_siginfo}
20108 @item @code{write-siginfo-object}
20109 @tab @code{qXfer:siginfo:write}
20110 @tab @code{set $_siginfo}
20112 @item @code{threads}
20113 @tab @code{qXfer:threads:read}
20114 @tab @code{info threads}
20116 @item @code{get-thread-local-@*storage-address}
20117 @tab @code{qGetTLSAddr}
20118 @tab Displaying @code{__thread} variables
20120 @item @code{get-thread-information-block-address}
20121 @tab @code{qGetTIBAddr}
20122 @tab Display MS-Windows Thread Information Block.
20124 @item @code{search-memory}
20125 @tab @code{qSearch:memory}
20128 @item @code{supported-packets}
20129 @tab @code{qSupported}
20130 @tab Remote communications parameters
20132 @item @code{pass-signals}
20133 @tab @code{QPassSignals}
20134 @tab @code{handle @var{signal}}
20136 @item @code{program-signals}
20137 @tab @code{QProgramSignals}
20138 @tab @code{handle @var{signal}}
20140 @item @code{hostio-close-packet}
20141 @tab @code{vFile:close}
20142 @tab @code{remote get}, @code{remote put}
20144 @item @code{hostio-open-packet}
20145 @tab @code{vFile:open}
20146 @tab @code{remote get}, @code{remote put}
20148 @item @code{hostio-pread-packet}
20149 @tab @code{vFile:pread}
20150 @tab @code{remote get}, @code{remote put}
20152 @item @code{hostio-pwrite-packet}
20153 @tab @code{vFile:pwrite}
20154 @tab @code{remote get}, @code{remote put}
20156 @item @code{hostio-unlink-packet}
20157 @tab @code{vFile:unlink}
20158 @tab @code{remote delete}
20160 @item @code{hostio-readlink-packet}
20161 @tab @code{vFile:readlink}
20164 @item @code{hostio-fstat-packet}
20165 @tab @code{vFile:fstat}
20168 @item @code{hostio-setfs-packet}
20169 @tab @code{vFile:setfs}
20172 @item @code{noack-packet}
20173 @tab @code{QStartNoAckMode}
20174 @tab Packet acknowledgment
20176 @item @code{osdata}
20177 @tab @code{qXfer:osdata:read}
20178 @tab @code{info os}
20180 @item @code{query-attached}
20181 @tab @code{qAttached}
20182 @tab Querying remote process attach state.
20184 @item @code{trace-buffer-size}
20185 @tab @code{QTBuffer:size}
20186 @tab @code{set trace-buffer-size}
20188 @item @code{trace-status}
20189 @tab @code{qTStatus}
20190 @tab @code{tstatus}
20192 @item @code{traceframe-info}
20193 @tab @code{qXfer:traceframe-info:read}
20194 @tab Traceframe info
20196 @item @code{install-in-trace}
20197 @tab @code{InstallInTrace}
20198 @tab Install tracepoint in tracing
20200 @item @code{disable-randomization}
20201 @tab @code{QDisableRandomization}
20202 @tab @code{set disable-randomization}
20204 @item @code{conditional-breakpoints-packet}
20205 @tab @code{Z0 and Z1}
20206 @tab @code{Support for target-side breakpoint condition evaluation}
20208 @item @code{multiprocess-extensions}
20209 @tab @code{multiprocess extensions}
20210 @tab Debug multiple processes and remote process PID awareness
20212 @item @code{swbreak-feature}
20213 @tab @code{swbreak stop reason}
20216 @item @code{hwbreak-feature}
20217 @tab @code{hwbreak stop reason}
20220 @item @code{fork-event-feature}
20221 @tab @code{fork stop reason}
20224 @item @code{vfork-event-feature}
20225 @tab @code{vfork stop reason}
20231 @section Implementing a Remote Stub
20233 @cindex debugging stub, example
20234 @cindex remote stub, example
20235 @cindex stub example, remote debugging
20236 The stub files provided with @value{GDBN} implement the target side of the
20237 communication protocol, and the @value{GDBN} side is implemented in the
20238 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20239 these subroutines to communicate, and ignore the details. (If you're
20240 implementing your own stub file, you can still ignore the details: start
20241 with one of the existing stub files. @file{sparc-stub.c} is the best
20242 organized, and therefore the easiest to read.)
20244 @cindex remote serial debugging, overview
20245 To debug a program running on another machine (the debugging
20246 @dfn{target} machine), you must first arrange for all the usual
20247 prerequisites for the program to run by itself. For example, for a C
20252 A startup routine to set up the C runtime environment; these usually
20253 have a name like @file{crt0}. The startup routine may be supplied by
20254 your hardware supplier, or you may have to write your own.
20257 A C subroutine library to support your program's
20258 subroutine calls, notably managing input and output.
20261 A way of getting your program to the other machine---for example, a
20262 download program. These are often supplied by the hardware
20263 manufacturer, but you may have to write your own from hardware
20267 The next step is to arrange for your program to use a serial port to
20268 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20269 machine). In general terms, the scheme looks like this:
20273 @value{GDBN} already understands how to use this protocol; when everything
20274 else is set up, you can simply use the @samp{target remote} command
20275 (@pxref{Targets,,Specifying a Debugging Target}).
20277 @item On the target,
20278 you must link with your program a few special-purpose subroutines that
20279 implement the @value{GDBN} remote serial protocol. The file containing these
20280 subroutines is called a @dfn{debugging stub}.
20282 On certain remote targets, you can use an auxiliary program
20283 @code{gdbserver} instead of linking a stub into your program.
20284 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20287 The debugging stub is specific to the architecture of the remote
20288 machine; for example, use @file{sparc-stub.c} to debug programs on
20291 @cindex remote serial stub list
20292 These working remote stubs are distributed with @value{GDBN}:
20297 @cindex @file{i386-stub.c}
20300 For Intel 386 and compatible architectures.
20303 @cindex @file{m68k-stub.c}
20304 @cindex Motorola 680x0
20306 For Motorola 680x0 architectures.
20309 @cindex @file{sh-stub.c}
20312 For Renesas SH architectures.
20315 @cindex @file{sparc-stub.c}
20317 For @sc{sparc} architectures.
20319 @item sparcl-stub.c
20320 @cindex @file{sparcl-stub.c}
20323 For Fujitsu @sc{sparclite} architectures.
20327 The @file{README} file in the @value{GDBN} distribution may list other
20328 recently added stubs.
20331 * Stub Contents:: What the stub can do for you
20332 * Bootstrapping:: What you must do for the stub
20333 * Debug Session:: Putting it all together
20336 @node Stub Contents
20337 @subsection What the Stub Can Do for You
20339 @cindex remote serial stub
20340 The debugging stub for your architecture supplies these three
20344 @item set_debug_traps
20345 @findex set_debug_traps
20346 @cindex remote serial stub, initialization
20347 This routine arranges for @code{handle_exception} to run when your
20348 program stops. You must call this subroutine explicitly in your
20349 program's startup code.
20351 @item handle_exception
20352 @findex handle_exception
20353 @cindex remote serial stub, main routine
20354 This is the central workhorse, but your program never calls it
20355 explicitly---the setup code arranges for @code{handle_exception} to
20356 run when a trap is triggered.
20358 @code{handle_exception} takes control when your program stops during
20359 execution (for example, on a breakpoint), and mediates communications
20360 with @value{GDBN} on the host machine. This is where the communications
20361 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20362 representative on the target machine. It begins by sending summary
20363 information on the state of your program, then continues to execute,
20364 retrieving and transmitting any information @value{GDBN} needs, until you
20365 execute a @value{GDBN} command that makes your program resume; at that point,
20366 @code{handle_exception} returns control to your own code on the target
20370 @cindex @code{breakpoint} subroutine, remote
20371 Use this auxiliary subroutine to make your program contain a
20372 breakpoint. Depending on the particular situation, this may be the only
20373 way for @value{GDBN} to get control. For instance, if your target
20374 machine has some sort of interrupt button, you won't need to call this;
20375 pressing the interrupt button transfers control to
20376 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20377 simply receiving characters on the serial port may also trigger a trap;
20378 again, in that situation, you don't need to call @code{breakpoint} from
20379 your own program---simply running @samp{target remote} from the host
20380 @value{GDBN} session gets control.
20382 Call @code{breakpoint} if none of these is true, or if you simply want
20383 to make certain your program stops at a predetermined point for the
20384 start of your debugging session.
20387 @node Bootstrapping
20388 @subsection What You Must Do for the Stub
20390 @cindex remote stub, support routines
20391 The debugging stubs that come with @value{GDBN} are set up for a particular
20392 chip architecture, but they have no information about the rest of your
20393 debugging target machine.
20395 First of all you need to tell the stub how to communicate with the
20399 @item int getDebugChar()
20400 @findex getDebugChar
20401 Write this subroutine to read a single character from the serial port.
20402 It may be identical to @code{getchar} for your target system; a
20403 different name is used to allow you to distinguish the two if you wish.
20405 @item void putDebugChar(int)
20406 @findex putDebugChar
20407 Write this subroutine to write a single character to the serial port.
20408 It may be identical to @code{putchar} for your target system; a
20409 different name is used to allow you to distinguish the two if you wish.
20412 @cindex control C, and remote debugging
20413 @cindex interrupting remote targets
20414 If you want @value{GDBN} to be able to stop your program while it is
20415 running, you need to use an interrupt-driven serial driver, and arrange
20416 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20417 character). That is the character which @value{GDBN} uses to tell the
20418 remote system to stop.
20420 Getting the debugging target to return the proper status to @value{GDBN}
20421 probably requires changes to the standard stub; one quick and dirty way
20422 is to just execute a breakpoint instruction (the ``dirty'' part is that
20423 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20425 Other routines you need to supply are:
20428 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20429 @findex exceptionHandler
20430 Write this function to install @var{exception_address} in the exception
20431 handling tables. You need to do this because the stub does not have any
20432 way of knowing what the exception handling tables on your target system
20433 are like (for example, the processor's table might be in @sc{rom},
20434 containing entries which point to a table in @sc{ram}).
20435 The @var{exception_number} specifies the exception which should be changed;
20436 its meaning is architecture-dependent (for example, different numbers
20437 might represent divide by zero, misaligned access, etc). When this
20438 exception occurs, control should be transferred directly to
20439 @var{exception_address}, and the processor state (stack, registers,
20440 and so on) should be just as it is when a processor exception occurs. So if
20441 you want to use a jump instruction to reach @var{exception_address}, it
20442 should be a simple jump, not a jump to subroutine.
20444 For the 386, @var{exception_address} should be installed as an interrupt
20445 gate so that interrupts are masked while the handler runs. The gate
20446 should be at privilege level 0 (the most privileged level). The
20447 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
20448 help from @code{exceptionHandler}.
20450 @item void flush_i_cache()
20451 @findex flush_i_cache
20452 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
20453 instruction cache, if any, on your target machine. If there is no
20454 instruction cache, this subroutine may be a no-op.
20456 On target machines that have instruction caches, @value{GDBN} requires this
20457 function to make certain that the state of your program is stable.
20461 You must also make sure this library routine is available:
20464 @item void *memset(void *, int, int)
20466 This is the standard library function @code{memset} that sets an area of
20467 memory to a known value. If you have one of the free versions of
20468 @code{libc.a}, @code{memset} can be found there; otherwise, you must
20469 either obtain it from your hardware manufacturer, or write your own.
20472 If you do not use the GNU C compiler, you may need other standard
20473 library subroutines as well; this varies from one stub to another,
20474 but in general the stubs are likely to use any of the common library
20475 subroutines which @code{@value{NGCC}} generates as inline code.
20478 @node Debug Session
20479 @subsection Putting it All Together
20481 @cindex remote serial debugging summary
20482 In summary, when your program is ready to debug, you must follow these
20487 Make sure you have defined the supporting low-level routines
20488 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
20490 @code{getDebugChar}, @code{putDebugChar},
20491 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
20495 Insert these lines in your program's startup code, before the main
20496 procedure is called:
20503 On some machines, when a breakpoint trap is raised, the hardware
20504 automatically makes the PC point to the instruction after the
20505 breakpoint. If your machine doesn't do that, you may need to adjust
20506 @code{handle_exception} to arrange for it to return to the instruction
20507 after the breakpoint on this first invocation, so that your program
20508 doesn't keep hitting the initial breakpoint instead of making
20512 For the 680x0 stub only, you need to provide a variable called
20513 @code{exceptionHook}. Normally you just use:
20516 void (*exceptionHook)() = 0;
20520 but if before calling @code{set_debug_traps}, you set it to point to a
20521 function in your program, that function is called when
20522 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
20523 error). The function indicated by @code{exceptionHook} is called with
20524 one parameter: an @code{int} which is the exception number.
20527 Compile and link together: your program, the @value{GDBN} debugging stub for
20528 your target architecture, and the supporting subroutines.
20531 Make sure you have a serial connection between your target machine and
20532 the @value{GDBN} host, and identify the serial port on the host.
20535 @c The "remote" target now provides a `load' command, so we should
20536 @c document that. FIXME.
20537 Download your program to your target machine (or get it there by
20538 whatever means the manufacturer provides), and start it.
20541 Start @value{GDBN} on the host, and connect to the target
20542 (@pxref{Connecting,,Connecting to a Remote Target}).
20546 @node Configurations
20547 @chapter Configuration-Specific Information
20549 While nearly all @value{GDBN} commands are available for all native and
20550 cross versions of the debugger, there are some exceptions. This chapter
20551 describes things that are only available in certain configurations.
20553 There are three major categories of configurations: native
20554 configurations, where the host and target are the same, embedded
20555 operating system configurations, which are usually the same for several
20556 different processor architectures, and bare embedded processors, which
20557 are quite different from each other.
20562 * Embedded Processors::
20569 This section describes details specific to particular native
20574 * BSD libkvm Interface:: Debugging BSD kernel memory images
20575 * SVR4 Process Information:: SVR4 process information
20576 * DJGPP Native:: Features specific to the DJGPP port
20577 * Cygwin Native:: Features specific to the Cygwin port
20578 * Hurd Native:: Features specific to @sc{gnu} Hurd
20579 * Darwin:: Features specific to Darwin
20585 On HP-UX systems, if you refer to a function or variable name that
20586 begins with a dollar sign, @value{GDBN} searches for a user or system
20587 name first, before it searches for a convenience variable.
20590 @node BSD libkvm Interface
20591 @subsection BSD libkvm Interface
20594 @cindex kernel memory image
20595 @cindex kernel crash dump
20597 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
20598 interface that provides a uniform interface for accessing kernel virtual
20599 memory images, including live systems and crash dumps. @value{GDBN}
20600 uses this interface to allow you to debug live kernels and kernel crash
20601 dumps on many native BSD configurations. This is implemented as a
20602 special @code{kvm} debugging target. For debugging a live system, load
20603 the currently running kernel into @value{GDBN} and connect to the
20607 (@value{GDBP}) @b{target kvm}
20610 For debugging crash dumps, provide the file name of the crash dump as an
20614 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20617 Once connected to the @code{kvm} target, the following commands are
20623 Set current context from the @dfn{Process Control Block} (PCB) address.
20626 Set current context from proc address. This command isn't available on
20627 modern FreeBSD systems.
20630 @node SVR4 Process Information
20631 @subsection SVR4 Process Information
20633 @cindex examine process image
20634 @cindex process info via @file{/proc}
20636 Many versions of SVR4 and compatible systems provide a facility called
20637 @samp{/proc} that can be used to examine the image of a running
20638 process using file-system subroutines.
20640 If @value{GDBN} is configured for an operating system with this
20641 facility, the command @code{info proc} is available to report
20642 information about the process running your program, or about any
20643 process running on your system. This includes, as of this writing,
20644 @sc{gnu}/Linux and Solaris, but not HP-UX, for example.
20646 This command may also work on core files that were created on a system
20647 that has the @samp{/proc} facility.
20653 @itemx info proc @var{process-id}
20654 Summarize available information about any running process. If a
20655 process ID is specified by @var{process-id}, display information about
20656 that process; otherwise display information about the program being
20657 debugged. The summary includes the debugged process ID, the command
20658 line used to invoke it, its current working directory, and its
20659 executable file's absolute file name.
20661 On some systems, @var{process-id} can be of the form
20662 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20663 within a process. If the optional @var{pid} part is missing, it means
20664 a thread from the process being debugged (the leading @samp{/} still
20665 needs to be present, or else @value{GDBN} will interpret the number as
20666 a process ID rather than a thread ID).
20668 @item info proc cmdline
20669 @cindex info proc cmdline
20670 Show the original command line of the process. This command is
20671 specific to @sc{gnu}/Linux.
20673 @item info proc cwd
20674 @cindex info proc cwd
20675 Show the current working directory of the process. This command is
20676 specific to @sc{gnu}/Linux.
20678 @item info proc exe
20679 @cindex info proc exe
20680 Show the name of executable of the process. This command is specific
20683 @item info proc mappings
20684 @cindex memory address space mappings
20685 Report the memory address space ranges accessible in the program, with
20686 information on whether the process has read, write, or execute access
20687 rights to each range. On @sc{gnu}/Linux systems, each memory range
20688 includes the object file which is mapped to that range, instead of the
20689 memory access rights to that range.
20691 @item info proc stat
20692 @itemx info proc status
20693 @cindex process detailed status information
20694 These subcommands are specific to @sc{gnu}/Linux systems. They show
20695 the process-related information, including the user ID and group ID;
20696 how many threads are there in the process; its virtual memory usage;
20697 the signals that are pending, blocked, and ignored; its TTY; its
20698 consumption of system and user time; its stack size; its @samp{nice}
20699 value; etc. For more information, see the @samp{proc} man page
20700 (type @kbd{man 5 proc} from your shell prompt).
20702 @item info proc all
20703 Show all the information about the process described under all of the
20704 above @code{info proc} subcommands.
20707 @comment These sub-options of 'info proc' were not included when
20708 @comment procfs.c was re-written. Keep their descriptions around
20709 @comment against the day when someone finds the time to put them back in.
20710 @kindex info proc times
20711 @item info proc times
20712 Starting time, user CPU time, and system CPU time for your program and
20715 @kindex info proc id
20717 Report on the process IDs related to your program: its own process ID,
20718 the ID of its parent, the process group ID, and the session ID.
20721 @item set procfs-trace
20722 @kindex set procfs-trace
20723 @cindex @code{procfs} API calls
20724 This command enables and disables tracing of @code{procfs} API calls.
20726 @item show procfs-trace
20727 @kindex show procfs-trace
20728 Show the current state of @code{procfs} API call tracing.
20730 @item set procfs-file @var{file}
20731 @kindex set procfs-file
20732 Tell @value{GDBN} to write @code{procfs} API trace to the named
20733 @var{file}. @value{GDBN} appends the trace info to the previous
20734 contents of the file. The default is to display the trace on the
20737 @item show procfs-file
20738 @kindex show procfs-file
20739 Show the file to which @code{procfs} API trace is written.
20741 @item proc-trace-entry
20742 @itemx proc-trace-exit
20743 @itemx proc-untrace-entry
20744 @itemx proc-untrace-exit
20745 @kindex proc-trace-entry
20746 @kindex proc-trace-exit
20747 @kindex proc-untrace-entry
20748 @kindex proc-untrace-exit
20749 These commands enable and disable tracing of entries into and exits
20750 from the @code{syscall} interface.
20753 @kindex info pidlist
20754 @cindex process list, QNX Neutrino
20755 For QNX Neutrino only, this command displays the list of all the
20756 processes and all the threads within each process.
20759 @kindex info meminfo
20760 @cindex mapinfo list, QNX Neutrino
20761 For QNX Neutrino only, this command displays the list of all mapinfos.
20765 @subsection Features for Debugging @sc{djgpp} Programs
20766 @cindex @sc{djgpp} debugging
20767 @cindex native @sc{djgpp} debugging
20768 @cindex MS-DOS-specific commands
20771 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20772 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20773 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20774 top of real-mode DOS systems and their emulations.
20776 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20777 defines a few commands specific to the @sc{djgpp} port. This
20778 subsection describes those commands.
20783 This is a prefix of @sc{djgpp}-specific commands which print
20784 information about the target system and important OS structures.
20787 @cindex MS-DOS system info
20788 @cindex free memory information (MS-DOS)
20789 @item info dos sysinfo
20790 This command displays assorted information about the underlying
20791 platform: the CPU type and features, the OS version and flavor, the
20792 DPMI version, and the available conventional and DPMI memory.
20797 @cindex segment descriptor tables
20798 @cindex descriptor tables display
20800 @itemx info dos ldt
20801 @itemx info dos idt
20802 These 3 commands display entries from, respectively, Global, Local,
20803 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
20804 tables are data structures which store a descriptor for each segment
20805 that is currently in use. The segment's selector is an index into a
20806 descriptor table; the table entry for that index holds the
20807 descriptor's base address and limit, and its attributes and access
20810 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
20811 segment (used for both data and the stack), and a DOS segment (which
20812 allows access to DOS/BIOS data structures and absolute addresses in
20813 conventional memory). However, the DPMI host will usually define
20814 additional segments in order to support the DPMI environment.
20816 @cindex garbled pointers
20817 These commands allow to display entries from the descriptor tables.
20818 Without an argument, all entries from the specified table are
20819 displayed. An argument, which should be an integer expression, means
20820 display a single entry whose index is given by the argument. For
20821 example, here's a convenient way to display information about the
20822 debugged program's data segment:
20825 @exdent @code{(@value{GDBP}) info dos ldt $ds}
20826 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
20830 This comes in handy when you want to see whether a pointer is outside
20831 the data segment's limit (i.e.@: @dfn{garbled}).
20833 @cindex page tables display (MS-DOS)
20835 @itemx info dos pte
20836 These two commands display entries from, respectively, the Page
20837 Directory and the Page Tables. Page Directories and Page Tables are
20838 data structures which control how virtual memory addresses are mapped
20839 into physical addresses. A Page Table includes an entry for every
20840 page of memory that is mapped into the program's address space; there
20841 may be several Page Tables, each one holding up to 4096 entries. A
20842 Page Directory has up to 4096 entries, one each for every Page Table
20843 that is currently in use.
20845 Without an argument, @kbd{info dos pde} displays the entire Page
20846 Directory, and @kbd{info dos pte} displays all the entries in all of
20847 the Page Tables. An argument, an integer expression, given to the
20848 @kbd{info dos pde} command means display only that entry from the Page
20849 Directory table. An argument given to the @kbd{info dos pte} command
20850 means display entries from a single Page Table, the one pointed to by
20851 the specified entry in the Page Directory.
20853 @cindex direct memory access (DMA) on MS-DOS
20854 These commands are useful when your program uses @dfn{DMA} (Direct
20855 Memory Access), which needs physical addresses to program the DMA
20858 These commands are supported only with some DPMI servers.
20860 @cindex physical address from linear address
20861 @item info dos address-pte @var{addr}
20862 This command displays the Page Table entry for a specified linear
20863 address. The argument @var{addr} is a linear address which should
20864 already have the appropriate segment's base address added to it,
20865 because this command accepts addresses which may belong to @emph{any}
20866 segment. For example, here's how to display the Page Table entry for
20867 the page where a variable @code{i} is stored:
20870 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
20871 @exdent @code{Page Table entry for address 0x11a00d30:}
20872 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
20876 This says that @code{i} is stored at offset @code{0xd30} from the page
20877 whose physical base address is @code{0x02698000}, and shows all the
20878 attributes of that page.
20880 Note that you must cast the addresses of variables to a @code{char *},
20881 since otherwise the value of @code{__djgpp_base_address}, the base
20882 address of all variables and functions in a @sc{djgpp} program, will
20883 be added using the rules of C pointer arithmetics: if @code{i} is
20884 declared an @code{int}, @value{GDBN} will add 4 times the value of
20885 @code{__djgpp_base_address} to the address of @code{i}.
20887 Here's another example, it displays the Page Table entry for the
20891 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
20892 @exdent @code{Page Table entry for address 0x29110:}
20893 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
20897 (The @code{+ 3} offset is because the transfer buffer's address is the
20898 3rd member of the @code{_go32_info_block} structure.) The output
20899 clearly shows that this DPMI server maps the addresses in conventional
20900 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
20901 linear (@code{0x29110}) addresses are identical.
20903 This command is supported only with some DPMI servers.
20906 @cindex DOS serial data link, remote debugging
20907 In addition to native debugging, the DJGPP port supports remote
20908 debugging via a serial data link. The following commands are specific
20909 to remote serial debugging in the DJGPP port of @value{GDBN}.
20912 @kindex set com1base
20913 @kindex set com1irq
20914 @kindex set com2base
20915 @kindex set com2irq
20916 @kindex set com3base
20917 @kindex set com3irq
20918 @kindex set com4base
20919 @kindex set com4irq
20920 @item set com1base @var{addr}
20921 This command sets the base I/O port address of the @file{COM1} serial
20924 @item set com1irq @var{irq}
20925 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
20926 for the @file{COM1} serial port.
20928 There are similar commands @samp{set com2base}, @samp{set com3irq},
20929 etc.@: for setting the port address and the @code{IRQ} lines for the
20932 @kindex show com1base
20933 @kindex show com1irq
20934 @kindex show com2base
20935 @kindex show com2irq
20936 @kindex show com3base
20937 @kindex show com3irq
20938 @kindex show com4base
20939 @kindex show com4irq
20940 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
20941 display the current settings of the base address and the @code{IRQ}
20942 lines used by the COM ports.
20945 @kindex info serial
20946 @cindex DOS serial port status
20947 This command prints the status of the 4 DOS serial ports. For each
20948 port, it prints whether it's active or not, its I/O base address and
20949 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
20950 counts of various errors encountered so far.
20954 @node Cygwin Native
20955 @subsection Features for Debugging MS Windows PE Executables
20956 @cindex MS Windows debugging
20957 @cindex native Cygwin debugging
20958 @cindex Cygwin-specific commands
20960 @value{GDBN} supports native debugging of MS Windows programs, including
20961 DLLs with and without symbolic debugging information.
20963 @cindex Ctrl-BREAK, MS-Windows
20964 @cindex interrupt debuggee on MS-Windows
20965 MS-Windows programs that call @code{SetConsoleMode} to switch off the
20966 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
20967 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
20968 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
20969 sequence, which can be used to interrupt the debuggee even if it
20972 There are various additional Cygwin-specific commands, described in
20973 this section. Working with DLLs that have no debugging symbols is
20974 described in @ref{Non-debug DLL Symbols}.
20979 This is a prefix of MS Windows-specific commands which print
20980 information about the target system and important OS structures.
20982 @item info w32 selector
20983 This command displays information returned by
20984 the Win32 API @code{GetThreadSelectorEntry} function.
20985 It takes an optional argument that is evaluated to
20986 a long value to give the information about this given selector.
20987 Without argument, this command displays information
20988 about the six segment registers.
20990 @item info w32 thread-information-block
20991 This command displays thread specific information stored in the
20992 Thread Information Block (readable on the X86 CPU family using @code{$fs}
20993 selector for 32-bit programs and @code{$gs} for 64-bit programs).
20995 @kindex set cygwin-exceptions
20996 @cindex debugging the Cygwin DLL
20997 @cindex Cygwin DLL, debugging
20998 @item set cygwin-exceptions @var{mode}
20999 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21000 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21001 @value{GDBN} will delay recognition of exceptions, and may ignore some
21002 exceptions which seem to be caused by internal Cygwin DLL
21003 ``bookkeeping''. This option is meant primarily for debugging the
21004 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21005 @value{GDBN} users with false @code{SIGSEGV} signals.
21007 @kindex show cygwin-exceptions
21008 @item show cygwin-exceptions
21009 Displays whether @value{GDBN} will break on exceptions that happen
21010 inside the Cygwin DLL itself.
21012 @kindex set new-console
21013 @item set new-console @var{mode}
21014 If @var{mode} is @code{on} the debuggee will
21015 be started in a new console on next start.
21016 If @var{mode} is @code{off}, the debuggee will
21017 be started in the same console as the debugger.
21019 @kindex show new-console
21020 @item show new-console
21021 Displays whether a new console is used
21022 when the debuggee is started.
21024 @kindex set new-group
21025 @item set new-group @var{mode}
21026 This boolean value controls whether the debuggee should
21027 start a new group or stay in the same group as the debugger.
21028 This affects the way the Windows OS handles
21031 @kindex show new-group
21032 @item show new-group
21033 Displays current value of new-group boolean.
21035 @kindex set debugevents
21036 @item set debugevents
21037 This boolean value adds debug output concerning kernel events related
21038 to the debuggee seen by the debugger. This includes events that
21039 signal thread and process creation and exit, DLL loading and
21040 unloading, console interrupts, and debugging messages produced by the
21041 Windows @code{OutputDebugString} API call.
21043 @kindex set debugexec
21044 @item set debugexec
21045 This boolean value adds debug output concerning execute events
21046 (such as resume thread) seen by the debugger.
21048 @kindex set debugexceptions
21049 @item set debugexceptions
21050 This boolean value adds debug output concerning exceptions in the
21051 debuggee seen by the debugger.
21053 @kindex set debugmemory
21054 @item set debugmemory
21055 This boolean value adds debug output concerning debuggee memory reads
21056 and writes by the debugger.
21060 This boolean values specifies whether the debuggee is called
21061 via a shell or directly (default value is on).
21065 Displays if the debuggee will be started with a shell.
21070 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21073 @node Non-debug DLL Symbols
21074 @subsubsection Support for DLLs without Debugging Symbols
21075 @cindex DLLs with no debugging symbols
21076 @cindex Minimal symbols and DLLs
21078 Very often on windows, some of the DLLs that your program relies on do
21079 not include symbolic debugging information (for example,
21080 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21081 symbols in a DLL, it relies on the minimal amount of symbolic
21082 information contained in the DLL's export table. This section
21083 describes working with such symbols, known internally to @value{GDBN} as
21084 ``minimal symbols''.
21086 Note that before the debugged program has started execution, no DLLs
21087 will have been loaded. The easiest way around this problem is simply to
21088 start the program --- either by setting a breakpoint or letting the
21089 program run once to completion.
21091 @subsubsection DLL Name Prefixes
21093 In keeping with the naming conventions used by the Microsoft debugging
21094 tools, DLL export symbols are made available with a prefix based on the
21095 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21096 also entered into the symbol table, so @code{CreateFileA} is often
21097 sufficient. In some cases there will be name clashes within a program
21098 (particularly if the executable itself includes full debugging symbols)
21099 necessitating the use of the fully qualified name when referring to the
21100 contents of the DLL. Use single-quotes around the name to avoid the
21101 exclamation mark (``!'') being interpreted as a language operator.
21103 Note that the internal name of the DLL may be all upper-case, even
21104 though the file name of the DLL is lower-case, or vice-versa. Since
21105 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21106 some confusion. If in doubt, try the @code{info functions} and
21107 @code{info variables} commands or even @code{maint print msymbols}
21108 (@pxref{Symbols}). Here's an example:
21111 (@value{GDBP}) info function CreateFileA
21112 All functions matching regular expression "CreateFileA":
21114 Non-debugging symbols:
21115 0x77e885f4 CreateFileA
21116 0x77e885f4 KERNEL32!CreateFileA
21120 (@value{GDBP}) info function !
21121 All functions matching regular expression "!":
21123 Non-debugging symbols:
21124 0x6100114c cygwin1!__assert
21125 0x61004034 cygwin1!_dll_crt0@@0
21126 0x61004240 cygwin1!dll_crt0(per_process *)
21130 @subsubsection Working with Minimal Symbols
21132 Symbols extracted from a DLL's export table do not contain very much
21133 type information. All that @value{GDBN} can do is guess whether a symbol
21134 refers to a function or variable depending on the linker section that
21135 contains the symbol. Also note that the actual contents of the memory
21136 contained in a DLL are not available unless the program is running. This
21137 means that you cannot examine the contents of a variable or disassemble
21138 a function within a DLL without a running program.
21140 Variables are generally treated as pointers and dereferenced
21141 automatically. For this reason, it is often necessary to prefix a
21142 variable name with the address-of operator (``&'') and provide explicit
21143 type information in the command. Here's an example of the type of
21147 (@value{GDBP}) print 'cygwin1!__argv'
21152 (@value{GDBP}) x 'cygwin1!__argv'
21153 0x10021610: "\230y\""
21156 And two possible solutions:
21159 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21160 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21164 (@value{GDBP}) x/2x &'cygwin1!__argv'
21165 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21166 (@value{GDBP}) x/x 0x10021608
21167 0x10021608: 0x0022fd98
21168 (@value{GDBP}) x/s 0x0022fd98
21169 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21172 Setting a break point within a DLL is possible even before the program
21173 starts execution. However, under these circumstances, @value{GDBN} can't
21174 examine the initial instructions of the function in order to skip the
21175 function's frame set-up code. You can work around this by using ``*&''
21176 to set the breakpoint at a raw memory address:
21179 (@value{GDBP}) break *&'python22!PyOS_Readline'
21180 Breakpoint 1 at 0x1e04eff0
21183 The author of these extensions is not entirely convinced that setting a
21184 break point within a shared DLL like @file{kernel32.dll} is completely
21188 @subsection Commands Specific to @sc{gnu} Hurd Systems
21189 @cindex @sc{gnu} Hurd debugging
21191 This subsection describes @value{GDBN} commands specific to the
21192 @sc{gnu} Hurd native debugging.
21197 @kindex set signals@r{, Hurd command}
21198 @kindex set sigs@r{, Hurd command}
21199 This command toggles the state of inferior signal interception by
21200 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21201 affected by this command. @code{sigs} is a shorthand alias for
21206 @kindex show signals@r{, Hurd command}
21207 @kindex show sigs@r{, Hurd command}
21208 Show the current state of intercepting inferior's signals.
21210 @item set signal-thread
21211 @itemx set sigthread
21212 @kindex set signal-thread
21213 @kindex set sigthread
21214 This command tells @value{GDBN} which thread is the @code{libc} signal
21215 thread. That thread is run when a signal is delivered to a running
21216 process. @code{set sigthread} is the shorthand alias of @code{set
21219 @item show signal-thread
21220 @itemx show sigthread
21221 @kindex show signal-thread
21222 @kindex show sigthread
21223 These two commands show which thread will run when the inferior is
21224 delivered a signal.
21227 @kindex set stopped@r{, Hurd command}
21228 This commands tells @value{GDBN} that the inferior process is stopped,
21229 as with the @code{SIGSTOP} signal. The stopped process can be
21230 continued by delivering a signal to it.
21233 @kindex show stopped@r{, Hurd command}
21234 This command shows whether @value{GDBN} thinks the debuggee is
21237 @item set exceptions
21238 @kindex set exceptions@r{, Hurd command}
21239 Use this command to turn off trapping of exceptions in the inferior.
21240 When exception trapping is off, neither breakpoints nor
21241 single-stepping will work. To restore the default, set exception
21244 @item show exceptions
21245 @kindex show exceptions@r{, Hurd command}
21246 Show the current state of trapping exceptions in the inferior.
21248 @item set task pause
21249 @kindex set task@r{, Hurd commands}
21250 @cindex task attributes (@sc{gnu} Hurd)
21251 @cindex pause current task (@sc{gnu} Hurd)
21252 This command toggles task suspension when @value{GDBN} has control.
21253 Setting it to on takes effect immediately, and the task is suspended
21254 whenever @value{GDBN} gets control. Setting it to off will take
21255 effect the next time the inferior is continued. If this option is set
21256 to off, you can use @code{set thread default pause on} or @code{set
21257 thread pause on} (see below) to pause individual threads.
21259 @item show task pause
21260 @kindex show task@r{, Hurd commands}
21261 Show the current state of task suspension.
21263 @item set task detach-suspend-count
21264 @cindex task suspend count
21265 @cindex detach from task, @sc{gnu} Hurd
21266 This command sets the suspend count the task will be left with when
21267 @value{GDBN} detaches from it.
21269 @item show task detach-suspend-count
21270 Show the suspend count the task will be left with when detaching.
21272 @item set task exception-port
21273 @itemx set task excp
21274 @cindex task exception port, @sc{gnu} Hurd
21275 This command sets the task exception port to which @value{GDBN} will
21276 forward exceptions. The argument should be the value of the @dfn{send
21277 rights} of the task. @code{set task excp} is a shorthand alias.
21279 @item set noninvasive
21280 @cindex noninvasive task options
21281 This command switches @value{GDBN} to a mode that is the least
21282 invasive as far as interfering with the inferior is concerned. This
21283 is the same as using @code{set task pause}, @code{set exceptions}, and
21284 @code{set signals} to values opposite to the defaults.
21286 @item info send-rights
21287 @itemx info receive-rights
21288 @itemx info port-rights
21289 @itemx info port-sets
21290 @itemx info dead-names
21293 @cindex send rights, @sc{gnu} Hurd
21294 @cindex receive rights, @sc{gnu} Hurd
21295 @cindex port rights, @sc{gnu} Hurd
21296 @cindex port sets, @sc{gnu} Hurd
21297 @cindex dead names, @sc{gnu} Hurd
21298 These commands display information about, respectively, send rights,
21299 receive rights, port rights, port sets, and dead names of a task.
21300 There are also shorthand aliases: @code{info ports} for @code{info
21301 port-rights} and @code{info psets} for @code{info port-sets}.
21303 @item set thread pause
21304 @kindex set thread@r{, Hurd command}
21305 @cindex thread properties, @sc{gnu} Hurd
21306 @cindex pause current thread (@sc{gnu} Hurd)
21307 This command toggles current thread suspension when @value{GDBN} has
21308 control. Setting it to on takes effect immediately, and the current
21309 thread is suspended whenever @value{GDBN} gets control. Setting it to
21310 off will take effect the next time the inferior is continued.
21311 Normally, this command has no effect, since when @value{GDBN} has
21312 control, the whole task is suspended. However, if you used @code{set
21313 task pause off} (see above), this command comes in handy to suspend
21314 only the current thread.
21316 @item show thread pause
21317 @kindex show thread@r{, Hurd command}
21318 This command shows the state of current thread suspension.
21320 @item set thread run
21321 This command sets whether the current thread is allowed to run.
21323 @item show thread run
21324 Show whether the current thread is allowed to run.
21326 @item set thread detach-suspend-count
21327 @cindex thread suspend count, @sc{gnu} Hurd
21328 @cindex detach from thread, @sc{gnu} Hurd
21329 This command sets the suspend count @value{GDBN} will leave on a
21330 thread when detaching. This number is relative to the suspend count
21331 found by @value{GDBN} when it notices the thread; use @code{set thread
21332 takeover-suspend-count} to force it to an absolute value.
21334 @item show thread detach-suspend-count
21335 Show the suspend count @value{GDBN} will leave on the thread when
21338 @item set thread exception-port
21339 @itemx set thread excp
21340 Set the thread exception port to which to forward exceptions. This
21341 overrides the port set by @code{set task exception-port} (see above).
21342 @code{set thread excp} is the shorthand alias.
21344 @item set thread takeover-suspend-count
21345 Normally, @value{GDBN}'s thread suspend counts are relative to the
21346 value @value{GDBN} finds when it notices each thread. This command
21347 changes the suspend counts to be absolute instead.
21349 @item set thread default
21350 @itemx show thread default
21351 @cindex thread default settings, @sc{gnu} Hurd
21352 Each of the above @code{set thread} commands has a @code{set thread
21353 default} counterpart (e.g., @code{set thread default pause}, @code{set
21354 thread default exception-port}, etc.). The @code{thread default}
21355 variety of commands sets the default thread properties for all
21356 threads; you can then change the properties of individual threads with
21357 the non-default commands.
21364 @value{GDBN} provides the following commands specific to the Darwin target:
21367 @item set debug darwin @var{num}
21368 @kindex set debug darwin
21369 When set to a non zero value, enables debugging messages specific to
21370 the Darwin support. Higher values produce more verbose output.
21372 @item show debug darwin
21373 @kindex show debug darwin
21374 Show the current state of Darwin messages.
21376 @item set debug mach-o @var{num}
21377 @kindex set debug mach-o
21378 When set to a non zero value, enables debugging messages while
21379 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21380 file format used on Darwin for object and executable files.) Higher
21381 values produce more verbose output. This is a command to diagnose
21382 problems internal to @value{GDBN} and should not be needed in normal
21385 @item show debug mach-o
21386 @kindex show debug mach-o
21387 Show the current state of Mach-O file messages.
21389 @item set mach-exceptions on
21390 @itemx set mach-exceptions off
21391 @kindex set mach-exceptions
21392 On Darwin, faults are first reported as a Mach exception and are then
21393 mapped to a Posix signal. Use this command to turn on trapping of
21394 Mach exceptions in the inferior. This might be sometimes useful to
21395 better understand the cause of a fault. The default is off.
21397 @item show mach-exceptions
21398 @kindex show mach-exceptions
21399 Show the current state of exceptions trapping.
21404 @section Embedded Operating Systems
21406 This section describes configurations involving the debugging of
21407 embedded operating systems that are available for several different
21410 @value{GDBN} includes the ability to debug programs running on
21411 various real-time operating systems.
21413 @node Embedded Processors
21414 @section Embedded Processors
21416 This section goes into details specific to particular embedded
21419 @cindex send command to simulator
21420 Whenever a specific embedded processor has a simulator, @value{GDBN}
21421 allows to send an arbitrary command to the simulator.
21424 @item sim @var{command}
21425 @kindex sim@r{, a command}
21426 Send an arbitrary @var{command} string to the simulator. Consult the
21427 documentation for the specific simulator in use for information about
21428 acceptable commands.
21434 * M32R/SDI:: Renesas M32R/SDI
21435 * M68K:: Motorola M68K
21436 * MicroBlaze:: Xilinx MicroBlaze
21437 * MIPS Embedded:: MIPS Embedded
21438 * PowerPC Embedded:: PowerPC Embedded
21441 * Super-H:: Renesas Super-H
21447 @value{GDBN} provides the following ARM-specific commands:
21450 @item set arm disassembler
21452 This commands selects from a list of disassembly styles. The
21453 @code{"std"} style is the standard style.
21455 @item show arm disassembler
21457 Show the current disassembly style.
21459 @item set arm apcs32
21460 @cindex ARM 32-bit mode
21461 This command toggles ARM operation mode between 32-bit and 26-bit.
21463 @item show arm apcs32
21464 Display the current usage of the ARM 32-bit mode.
21466 @item set arm fpu @var{fputype}
21467 This command sets the ARM floating-point unit (FPU) type. The
21468 argument @var{fputype} can be one of these:
21472 Determine the FPU type by querying the OS ABI.
21474 Software FPU, with mixed-endian doubles on little-endian ARM
21477 GCC-compiled FPA co-processor.
21479 Software FPU with pure-endian doubles.
21485 Show the current type of the FPU.
21488 This command forces @value{GDBN} to use the specified ABI.
21491 Show the currently used ABI.
21493 @item set arm fallback-mode (arm|thumb|auto)
21494 @value{GDBN} uses the symbol table, when available, to determine
21495 whether instructions are ARM or Thumb. This command controls
21496 @value{GDBN}'s default behavior when the symbol table is not
21497 available. The default is @samp{auto}, which causes @value{GDBN} to
21498 use the current execution mode (from the @code{T} bit in the @code{CPSR}
21501 @item show arm fallback-mode
21502 Show the current fallback instruction mode.
21504 @item set arm force-mode (arm|thumb|auto)
21505 This command overrides use of the symbol table to determine whether
21506 instructions are ARM or Thumb. The default is @samp{auto}, which
21507 causes @value{GDBN} to use the symbol table and then the setting
21508 of @samp{set arm fallback-mode}.
21510 @item show arm force-mode
21511 Show the current forced instruction mode.
21513 @item set debug arm
21514 Toggle whether to display ARM-specific debugging messages from the ARM
21515 target support subsystem.
21517 @item show debug arm
21518 Show whether ARM-specific debugging messages are enabled.
21522 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21523 The @value{GDBN} ARM simulator accepts the following optional arguments.
21526 @item --swi-support=@var{type}
21527 Tell the simulator which SWI interfaces to support. The argument
21528 @var{type} may be a comma separated list of the following values.
21529 The default value is @code{all}.
21542 @subsection Renesas M32R/SDI
21544 The following commands are available for M32R/SDI:
21549 @cindex reset SDI connection, M32R
21550 This command resets the SDI connection.
21554 This command shows the SDI connection status.
21557 @kindex debug_chaos
21558 @cindex M32R/Chaos debugging
21559 Instructs the remote that M32R/Chaos debugging is to be used.
21561 @item use_debug_dma
21562 @kindex use_debug_dma
21563 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21566 @kindex use_mon_code
21567 Instructs the remote to use the MON_CODE method of accessing memory.
21570 @kindex use_ib_break
21571 Instructs the remote to set breakpoints by IB break.
21573 @item use_dbt_break
21574 @kindex use_dbt_break
21575 Instructs the remote to set breakpoints by DBT.
21581 The Motorola m68k configuration includes ColdFire support.
21584 @subsection MicroBlaze
21585 @cindex Xilinx MicroBlaze
21586 @cindex XMD, Xilinx Microprocessor Debugger
21588 The MicroBlaze is a soft-core processor supported on various Xilinx
21589 FPGAs, such as Spartan or Virtex series. Boards with these processors
21590 usually have JTAG ports which connect to a host system running the Xilinx
21591 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21592 This host system is used to download the configuration bitstream to
21593 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21594 communicates with the target board using the JTAG interface and
21595 presents a @code{gdbserver} interface to the board. By default
21596 @code{xmd} uses port @code{1234}. (While it is possible to change
21597 this default port, it requires the use of undocumented @code{xmd}
21598 commands. Contact Xilinx support if you need to do this.)
21600 Use these GDB commands to connect to the MicroBlaze target processor.
21603 @item target remote :1234
21604 Use this command to connect to the target if you are running @value{GDBN}
21605 on the same system as @code{xmd}.
21607 @item target remote @var{xmd-host}:1234
21608 Use this command to connect to the target if it is connected to @code{xmd}
21609 running on a different system named @var{xmd-host}.
21612 Use this command to download a program to the MicroBlaze target.
21614 @item set debug microblaze @var{n}
21615 Enable MicroBlaze-specific debugging messages if non-zero.
21617 @item show debug microblaze @var{n}
21618 Show MicroBlaze-specific debugging level.
21621 @node MIPS Embedded
21622 @subsection @acronym{MIPS} Embedded
21624 @cindex @acronym{MIPS} boards
21625 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21626 @acronym{MIPS} board attached to a serial line. This is available when
21627 you configure @value{GDBN} with @samp{--target=mips-elf}.
21630 Use these @value{GDBN} commands to specify the connection to your target board:
21633 @item target mips @var{port}
21634 @kindex target mips @var{port}
21635 To run a program on the board, start up @code{@value{GDBP}} with the
21636 name of your program as the argument. To connect to the board, use the
21637 command @samp{target mips @var{port}}, where @var{port} is the name of
21638 the serial port connected to the board. If the program has not already
21639 been downloaded to the board, you may use the @code{load} command to
21640 download it. You can then use all the usual @value{GDBN} commands.
21642 For example, this sequence connects to the target board through a serial
21643 port, and loads and runs a program called @var{prog} through the
21647 host$ @value{GDBP} @var{prog}
21648 @value{GDBN} is free software and @dots{}
21649 (@value{GDBP}) target mips /dev/ttyb
21650 (@value{GDBP}) load @var{prog}
21654 @item target mips @var{hostname}:@var{portnumber}
21655 On some @value{GDBN} host configurations, you can specify a TCP
21656 connection (for instance, to a serial line managed by a terminal
21657 concentrator) instead of a serial port, using the syntax
21658 @samp{@var{hostname}:@var{portnumber}}.
21660 @item target pmon @var{port}
21661 @kindex target pmon @var{port}
21664 @item target ddb @var{port}
21665 @kindex target ddb @var{port}
21666 NEC's DDB variant of PMON for Vr4300.
21668 @item target lsi @var{port}
21669 @kindex target lsi @var{port}
21670 LSI variant of PMON.
21676 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21679 @item set mipsfpu double
21680 @itemx set mipsfpu single
21681 @itemx set mipsfpu none
21682 @itemx set mipsfpu auto
21683 @itemx show mipsfpu
21684 @kindex set mipsfpu
21685 @kindex show mipsfpu
21686 @cindex @acronym{MIPS} remote floating point
21687 @cindex floating point, @acronym{MIPS} remote
21688 If your target board does not support the @acronym{MIPS} floating point
21689 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21690 need this, you may wish to put the command in your @value{GDBN} init
21691 file). This tells @value{GDBN} how to find the return value of
21692 functions which return floating point values. It also allows
21693 @value{GDBN} to avoid saving the floating point registers when calling
21694 functions on the board. If you are using a floating point coprocessor
21695 with only single precision floating point support, as on the @sc{r4650}
21696 processor, use the command @samp{set mipsfpu single}. The default
21697 double precision floating point coprocessor may be selected using
21698 @samp{set mipsfpu double}.
21700 In previous versions the only choices were double precision or no
21701 floating point, so @samp{set mipsfpu on} will select double precision
21702 and @samp{set mipsfpu off} will select no floating point.
21704 As usual, you can inquire about the @code{mipsfpu} variable with
21705 @samp{show mipsfpu}.
21707 @item set timeout @var{seconds}
21708 @itemx set retransmit-timeout @var{seconds}
21709 @itemx show timeout
21710 @itemx show retransmit-timeout
21711 @cindex @code{timeout}, @acronym{MIPS} protocol
21712 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21713 @kindex set timeout
21714 @kindex show timeout
21715 @kindex set retransmit-timeout
21716 @kindex show retransmit-timeout
21717 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21718 remote protocol, with the @code{set timeout @var{seconds}} command. The
21719 default is 5 seconds. Similarly, you can control the timeout used while
21720 waiting for an acknowledgment of a packet with the @code{set
21721 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21722 You can inspect both values with @code{show timeout} and @code{show
21723 retransmit-timeout}. (These commands are @emph{only} available when
21724 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21726 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21727 is waiting for your program to stop. In that case, @value{GDBN} waits
21728 forever because it has no way of knowing how long the program is going
21729 to run before stopping.
21731 @item set syn-garbage-limit @var{num}
21732 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21733 @cindex synchronize with remote @acronym{MIPS} target
21734 Limit the maximum number of characters @value{GDBN} should ignore when
21735 it tries to synchronize with the remote target. The default is 10
21736 characters. Setting the limit to -1 means there's no limit.
21738 @item show syn-garbage-limit
21739 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21740 Show the current limit on the number of characters to ignore when
21741 trying to synchronize with the remote system.
21743 @item set monitor-prompt @var{prompt}
21744 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21745 @cindex remote monitor prompt
21746 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21747 remote monitor. The default depends on the target:
21757 @item show monitor-prompt
21758 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21759 Show the current strings @value{GDBN} expects as the prompt from the
21762 @item set monitor-warnings
21763 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21764 Enable or disable monitor warnings about hardware breakpoints. This
21765 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21766 display warning messages whose codes are returned by the @code{lsi}
21767 PMON monitor for breakpoint commands.
21769 @item show monitor-warnings
21770 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21771 Show the current setting of printing monitor warnings.
21773 @item pmon @var{command}
21774 @kindex pmon@r{, @acronym{MIPS} remote}
21775 @cindex send PMON command
21776 This command allows sending an arbitrary @var{command} string to the
21777 monitor. The monitor must be in debug mode for this to work.
21780 @node PowerPC Embedded
21781 @subsection PowerPC Embedded
21783 @cindex DVC register
21784 @value{GDBN} supports using the DVC (Data Value Compare) register to
21785 implement in hardware simple hardware watchpoint conditions of the form:
21788 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21789 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21792 The DVC register will be automatically used when @value{GDBN} detects
21793 such pattern in a condition expression, and the created watchpoint uses one
21794 debug register (either the @code{exact-watchpoints} option is on and the
21795 variable is scalar, or the variable has a length of one byte). This feature
21796 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21799 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21800 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21801 in which case watchpoints using only one debug register are created when
21802 watching variables of scalar types.
21804 You can create an artificial array to watch an arbitrary memory
21805 region using one of the following commands (@pxref{Expressions}):
21808 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21809 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21812 PowerPC embedded processors support masked watchpoints. See the discussion
21813 about the @code{mask} argument in @ref{Set Watchpoints}.
21815 @cindex ranged breakpoint
21816 PowerPC embedded processors support hardware accelerated
21817 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21818 the inferior whenever it executes an instruction at any address within
21819 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21820 use the @code{break-range} command.
21822 @value{GDBN} provides the following PowerPC-specific commands:
21825 @kindex break-range
21826 @item break-range @var{start-location}, @var{end-location}
21827 Set a breakpoint for an address range given by
21828 @var{start-location} and @var{end-location}, which can specify a function name,
21829 a line number, an offset of lines from the current line or from the start
21830 location, or an address of an instruction (see @ref{Specify Location},
21831 for a list of all the possible ways to specify a @var{location}.)
21832 The breakpoint will stop execution of the inferior whenever it
21833 executes an instruction at any address within the specified range,
21834 (including @var{start-location} and @var{end-location}.)
21836 @kindex set powerpc
21837 @item set powerpc soft-float
21838 @itemx show powerpc soft-float
21839 Force @value{GDBN} to use (or not use) a software floating point calling
21840 convention. By default, @value{GDBN} selects the calling convention based
21841 on the selected architecture and the provided executable file.
21843 @item set powerpc vector-abi
21844 @itemx show powerpc vector-abi
21845 Force @value{GDBN} to use the specified calling convention for vector
21846 arguments and return values. The valid options are @samp{auto};
21847 @samp{generic}, to avoid vector registers even if they are present;
21848 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21849 registers. By default, @value{GDBN} selects the calling convention
21850 based on the selected architecture and the provided executable file.
21852 @item set powerpc exact-watchpoints
21853 @itemx show powerpc exact-watchpoints
21854 Allow @value{GDBN} to use only one debug register when watching a variable
21855 of scalar type, thus assuming that the variable is accessed through the
21856 address of its first byte.
21861 @subsection Atmel AVR
21864 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21865 following AVR-specific commands:
21868 @item info io_registers
21869 @kindex info io_registers@r{, AVR}
21870 @cindex I/O registers (Atmel AVR)
21871 This command displays information about the AVR I/O registers. For
21872 each register, @value{GDBN} prints its number and value.
21879 When configured for debugging CRIS, @value{GDBN} provides the
21880 following CRIS-specific commands:
21883 @item set cris-version @var{ver}
21884 @cindex CRIS version
21885 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21886 The CRIS version affects register names and sizes. This command is useful in
21887 case autodetection of the CRIS version fails.
21889 @item show cris-version
21890 Show the current CRIS version.
21892 @item set cris-dwarf2-cfi
21893 @cindex DWARF-2 CFI and CRIS
21894 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21895 Change to @samp{off} when using @code{gcc-cris} whose version is below
21898 @item show cris-dwarf2-cfi
21899 Show the current state of using DWARF-2 CFI.
21901 @item set cris-mode @var{mode}
21903 Set the current CRIS mode to @var{mode}. It should only be changed when
21904 debugging in guru mode, in which case it should be set to
21905 @samp{guru} (the default is @samp{normal}).
21907 @item show cris-mode
21908 Show the current CRIS mode.
21912 @subsection Renesas Super-H
21915 For the Renesas Super-H processor, @value{GDBN} provides these
21919 @item set sh calling-convention @var{convention}
21920 @kindex set sh calling-convention
21921 Set the calling-convention used when calling functions from @value{GDBN}.
21922 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21923 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21924 convention. If the DWARF-2 information of the called function specifies
21925 that the function follows the Renesas calling convention, the function
21926 is called using the Renesas calling convention. If the calling convention
21927 is set to @samp{renesas}, the Renesas calling convention is always used,
21928 regardless of the DWARF-2 information. This can be used to override the
21929 default of @samp{gcc} if debug information is missing, or the compiler
21930 does not emit the DWARF-2 calling convention entry for a function.
21932 @item show sh calling-convention
21933 @kindex show sh calling-convention
21934 Show the current calling convention setting.
21939 @node Architectures
21940 @section Architectures
21942 This section describes characteristics of architectures that affect
21943 all uses of @value{GDBN} with the architecture, both native and cross.
21950 * HPPA:: HP PA architecture
21951 * SPU:: Cell Broadband Engine SPU architecture
21957 @subsection AArch64
21958 @cindex AArch64 support
21960 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21961 following special commands:
21964 @item set debug aarch64
21965 @kindex set debug aarch64
21966 This command determines whether AArch64 architecture-specific debugging
21967 messages are to be displayed.
21969 @item show debug aarch64
21970 Show whether AArch64 debugging messages are displayed.
21975 @subsection x86 Architecture-specific Issues
21978 @item set struct-convention @var{mode}
21979 @kindex set struct-convention
21980 @cindex struct return convention
21981 @cindex struct/union returned in registers
21982 Set the convention used by the inferior to return @code{struct}s and
21983 @code{union}s from functions to @var{mode}. Possible values of
21984 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21985 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21986 are returned on the stack, while @code{"reg"} means that a
21987 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21988 be returned in a register.
21990 @item show struct-convention
21991 @kindex show struct-convention
21992 Show the current setting of the convention to return @code{struct}s
21997 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
21998 @cindex Intel(R) Memory Protection Extensions (MPX).
22000 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22001 @footnote{The register named with capital letters represent the architecture
22002 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22003 which are the lower bound and upper bound. Bounds are effective addresses or
22004 memory locations. The upper bounds are architecturally represented in 1's
22005 complement form. A bound having lower bound = 0, and upper bound = 0
22006 (1's complement of all bits set) will allow access to the entire address space.
22008 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22009 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22010 display the upper bound performing the complement of one operation on the
22011 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22012 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22013 can also be noted that the upper bounds are inclusive.
22015 As an example, assume that the register BND0 holds bounds for a pointer having
22016 access allowed for the range between 0x32 and 0x71. The values present on
22017 bnd0raw and bnd registers are presented as follows:
22020 bnd0raw = @{0x32, 0xffffffff8e@}
22021 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22024 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22025 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22026 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22027 Python, the display includes the memory size, in bits, accessible to
22030 Bounds can also be stored in bounds tables, which are stored in
22031 application memory. These tables store bounds for pointers by specifying
22032 the bounds pointer's value along with its bounds. Evaluating and changing
22033 bounds located in bound tables is therefore interesting while investigating
22034 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22037 @item show mpx bound @var{pointer}
22038 @kindex show mpx bound
22039 Display bounds of the given @var{pointer}.
22041 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22042 @kindex set mpx bound
22043 Set the bounds of a pointer in the bound table.
22044 This command takes three parameters: @var{pointer} is the pointers
22045 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22046 for lower and upper bounds respectively.
22052 See the following section.
22055 @subsection @acronym{MIPS}
22057 @cindex stack on Alpha
22058 @cindex stack on @acronym{MIPS}
22059 @cindex Alpha stack
22060 @cindex @acronym{MIPS} stack
22061 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22062 sometimes requires @value{GDBN} to search backward in the object code to
22063 find the beginning of a function.
22065 @cindex response time, @acronym{MIPS} debugging
22066 To improve response time (especially for embedded applications, where
22067 @value{GDBN} may be restricted to a slow serial line for this search)
22068 you may want to limit the size of this search, using one of these
22072 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22073 @item set heuristic-fence-post @var{limit}
22074 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22075 search for the beginning of a function. A value of @var{0} (the
22076 default) means there is no limit. However, except for @var{0}, the
22077 larger the limit the more bytes @code{heuristic-fence-post} must search
22078 and therefore the longer it takes to run. You should only need to use
22079 this command when debugging a stripped executable.
22081 @item show heuristic-fence-post
22082 Display the current limit.
22086 These commands are available @emph{only} when @value{GDBN} is configured
22087 for debugging programs on Alpha or @acronym{MIPS} processors.
22089 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22093 @item set mips abi @var{arg}
22094 @kindex set mips abi
22095 @cindex set ABI for @acronym{MIPS}
22096 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22097 values of @var{arg} are:
22101 The default ABI associated with the current binary (this is the
22111 @item show mips abi
22112 @kindex show mips abi
22113 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22115 @item set mips compression @var{arg}
22116 @kindex set mips compression
22117 @cindex code compression, @acronym{MIPS}
22118 Tell @value{GDBN} which @acronym{MIPS} compressed
22119 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22120 inferior. @value{GDBN} uses this for code disassembly and other
22121 internal interpretation purposes. This setting is only referred to
22122 when no executable has been associated with the debugging session or
22123 the executable does not provide information about the encoding it uses.
22124 Otherwise this setting is automatically updated from information
22125 provided by the executable.
22127 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22128 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22129 executables containing @acronym{MIPS16} code frequently are not
22130 identified as such.
22132 This setting is ``sticky''; that is, it retains its value across
22133 debugging sessions until reset either explicitly with this command or
22134 implicitly from an executable.
22136 The compiler and/or assembler typically add symbol table annotations to
22137 identify functions compiled for the @acronym{MIPS16} or
22138 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22139 are present, @value{GDBN} uses them in preference to the global
22140 compressed @acronym{ISA} encoding setting.
22142 @item show mips compression
22143 @kindex show mips compression
22144 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22145 @value{GDBN} to debug the inferior.
22148 @itemx show mipsfpu
22149 @xref{MIPS Embedded, set mipsfpu}.
22151 @item set mips mask-address @var{arg}
22152 @kindex set mips mask-address
22153 @cindex @acronym{MIPS} addresses, masking
22154 This command determines whether the most-significant 32 bits of 64-bit
22155 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22156 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22157 setting, which lets @value{GDBN} determine the correct value.
22159 @item show mips mask-address
22160 @kindex show mips mask-address
22161 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22164 @item set remote-mips64-transfers-32bit-regs
22165 @kindex set remote-mips64-transfers-32bit-regs
22166 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22167 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22168 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22169 and 64 bits for other registers, set this option to @samp{on}.
22171 @item show remote-mips64-transfers-32bit-regs
22172 @kindex show remote-mips64-transfers-32bit-regs
22173 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22175 @item set debug mips
22176 @kindex set debug mips
22177 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22178 target code in @value{GDBN}.
22180 @item show debug mips
22181 @kindex show debug mips
22182 Show the current setting of @acronym{MIPS} debugging messages.
22188 @cindex HPPA support
22190 When @value{GDBN} is debugging the HP PA architecture, it provides the
22191 following special commands:
22194 @item set debug hppa
22195 @kindex set debug hppa
22196 This command determines whether HPPA architecture-specific debugging
22197 messages are to be displayed.
22199 @item show debug hppa
22200 Show whether HPPA debugging messages are displayed.
22202 @item maint print unwind @var{address}
22203 @kindex maint print unwind@r{, HPPA}
22204 This command displays the contents of the unwind table entry at the
22205 given @var{address}.
22211 @subsection Cell Broadband Engine SPU architecture
22212 @cindex Cell Broadband Engine
22215 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22216 it provides the following special commands:
22219 @item info spu event
22221 Display SPU event facility status. Shows current event mask
22222 and pending event status.
22224 @item info spu signal
22225 Display SPU signal notification facility status. Shows pending
22226 signal-control word and signal notification mode of both signal
22227 notification channels.
22229 @item info spu mailbox
22230 Display SPU mailbox facility status. Shows all pending entries,
22231 in order of processing, in each of the SPU Write Outbound,
22232 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22235 Display MFC DMA status. Shows all pending commands in the MFC
22236 DMA queue. For each entry, opcode, tag, class IDs, effective
22237 and local store addresses and transfer size are shown.
22239 @item info spu proxydma
22240 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22241 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22242 and local store addresses and transfer size are shown.
22246 When @value{GDBN} is debugging a combined PowerPC/SPU application
22247 on the Cell Broadband Engine, it provides in addition the following
22251 @item set spu stop-on-load @var{arg}
22253 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22254 will give control to the user when a new SPE thread enters its @code{main}
22255 function. The default is @code{off}.
22257 @item show spu stop-on-load
22259 Show whether to stop for new SPE threads.
22261 @item set spu auto-flush-cache @var{arg}
22262 Set whether to automatically flush the software-managed cache. When set to
22263 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22264 cache to be flushed whenever SPE execution stops. This provides a consistent
22265 view of PowerPC memory that is accessed via the cache. If an application
22266 does not use the software-managed cache, this option has no effect.
22268 @item show spu auto-flush-cache
22269 Show whether to automatically flush the software-managed cache.
22274 @subsection PowerPC
22275 @cindex PowerPC architecture
22277 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22278 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22279 numbers stored in the floating point registers. These values must be stored
22280 in two consecutive registers, always starting at an even register like
22281 @code{f0} or @code{f2}.
22283 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22284 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22285 @code{f2} and @code{f3} for @code{$dl1} and so on.
22287 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22288 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22291 @subsection Nios II
22292 @cindex Nios II architecture
22294 When @value{GDBN} is debugging the Nios II architecture,
22295 it provides the following special commands:
22299 @item set debug nios2
22300 @kindex set debug nios2
22301 This command turns on and off debugging messages for the Nios II
22302 target code in @value{GDBN}.
22304 @item show debug nios2
22305 @kindex show debug nios2
22306 Show the current setting of Nios II debugging messages.
22309 @node Controlling GDB
22310 @chapter Controlling @value{GDBN}
22312 You can alter the way @value{GDBN} interacts with you by using the
22313 @code{set} command. For commands controlling how @value{GDBN} displays
22314 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22319 * Editing:: Command editing
22320 * Command History:: Command history
22321 * Screen Size:: Screen size
22322 * Numbers:: Numbers
22323 * ABI:: Configuring the current ABI
22324 * Auto-loading:: Automatically loading associated files
22325 * Messages/Warnings:: Optional warnings and messages
22326 * Debugging Output:: Optional messages about internal happenings
22327 * Other Misc Settings:: Other Miscellaneous Settings
22335 @value{GDBN} indicates its readiness to read a command by printing a string
22336 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22337 can change the prompt string with the @code{set prompt} command. For
22338 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22339 the prompt in one of the @value{GDBN} sessions so that you can always tell
22340 which one you are talking to.
22342 @emph{Note:} @code{set prompt} does not add a space for you after the
22343 prompt you set. This allows you to set a prompt which ends in a space
22344 or a prompt that does not.
22348 @item set prompt @var{newprompt}
22349 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22351 @kindex show prompt
22353 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22356 Versions of @value{GDBN} that ship with Python scripting enabled have
22357 prompt extensions. The commands for interacting with these extensions
22361 @kindex set extended-prompt
22362 @item set extended-prompt @var{prompt}
22363 Set an extended prompt that allows for substitutions.
22364 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22365 substitution. Any escape sequences specified as part of the prompt
22366 string are replaced with the corresponding strings each time the prompt
22372 set extended-prompt Current working directory: \w (gdb)
22375 Note that when an extended-prompt is set, it takes control of the
22376 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22378 @kindex show extended-prompt
22379 @item show extended-prompt
22380 Prints the extended prompt. Any escape sequences specified as part of
22381 the prompt string with @code{set extended-prompt}, are replaced with the
22382 corresponding strings each time the prompt is displayed.
22386 @section Command Editing
22388 @cindex command line editing
22390 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22391 @sc{gnu} library provides consistent behavior for programs which provide a
22392 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22393 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22394 substitution, and a storage and recall of command history across
22395 debugging sessions.
22397 You may control the behavior of command line editing in @value{GDBN} with the
22398 command @code{set}.
22401 @kindex set editing
22404 @itemx set editing on
22405 Enable command line editing (enabled by default).
22407 @item set editing off
22408 Disable command line editing.
22410 @kindex show editing
22412 Show whether command line editing is enabled.
22415 @ifset SYSTEM_READLINE
22416 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22418 @ifclear SYSTEM_READLINE
22419 @xref{Command Line Editing},
22421 for more details about the Readline
22422 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22423 encouraged to read that chapter.
22425 @node Command History
22426 @section Command History
22427 @cindex command history
22429 @value{GDBN} can keep track of the commands you type during your
22430 debugging sessions, so that you can be certain of precisely what
22431 happened. Use these commands to manage the @value{GDBN} command
22434 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22435 package, to provide the history facility.
22436 @ifset SYSTEM_READLINE
22437 @xref{Using History Interactively, , , history, GNU History Library},
22439 @ifclear SYSTEM_READLINE
22440 @xref{Using History Interactively},
22442 for the detailed description of the History library.
22444 To issue a command to @value{GDBN} without affecting certain aspects of
22445 the state which is seen by users, prefix it with @samp{server }
22446 (@pxref{Server Prefix}). This
22447 means that this command will not affect the command history, nor will it
22448 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22449 pressed on a line by itself.
22451 @cindex @code{server}, command prefix
22452 The server prefix does not affect the recording of values into the value
22453 history; to print a value without recording it into the value history,
22454 use the @code{output} command instead of the @code{print} command.
22456 Here is the description of @value{GDBN} commands related to command
22460 @cindex history substitution
22461 @cindex history file
22462 @kindex set history filename
22463 @cindex @env{GDBHISTFILE}, environment variable
22464 @item set history filename @var{fname}
22465 Set the name of the @value{GDBN} command history file to @var{fname}.
22466 This is the file where @value{GDBN} reads an initial command history
22467 list, and where it writes the command history from this session when it
22468 exits. You can access this list through history expansion or through
22469 the history command editing characters listed below. This file defaults
22470 to the value of the environment variable @code{GDBHISTFILE}, or to
22471 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22474 @cindex save command history
22475 @kindex set history save
22476 @item set history save
22477 @itemx set history save on
22478 Record command history in a file, whose name may be specified with the
22479 @code{set history filename} command. By default, this option is disabled.
22481 @item set history save off
22482 Stop recording command history in a file.
22484 @cindex history size
22485 @kindex set history size
22486 @cindex @env{GDBHISTSIZE}, environment variable
22487 @item set history size @var{size}
22488 @itemx set history size unlimited
22489 Set the number of commands which @value{GDBN} keeps in its history list.
22490 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
22491 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
22492 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
22493 either a negative number or the empty string, then the number of commands
22494 @value{GDBN} keeps in the history list is unlimited.
22496 @cindex remove duplicate history
22497 @kindex set history remove-duplicates
22498 @item set history remove-duplicates @var{count}
22499 @itemx set history remove-duplicates unlimited
22500 Control the removal of duplicate history entries in the command history list.
22501 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
22502 history entries and remove the first entry that is a duplicate of the current
22503 entry being added to the command history list. If @var{count} is
22504 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
22505 removal of duplicate history entries is disabled.
22507 Only history entries added during the current session are considered for
22508 removal. This option is set to 0 by default.
22512 History expansion assigns special meaning to the character @kbd{!}.
22513 @ifset SYSTEM_READLINE
22514 @xref{Event Designators, , , history, GNU History Library},
22516 @ifclear SYSTEM_READLINE
22517 @xref{Event Designators},
22521 @cindex history expansion, turn on/off
22522 Since @kbd{!} is also the logical not operator in C, history expansion
22523 is off by default. If you decide to enable history expansion with the
22524 @code{set history expansion on} command, you may sometimes need to
22525 follow @kbd{!} (when it is used as logical not, in an expression) with
22526 a space or a tab to prevent it from being expanded. The readline
22527 history facilities do not attempt substitution on the strings
22528 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22530 The commands to control history expansion are:
22533 @item set history expansion on
22534 @itemx set history expansion
22535 @kindex set history expansion
22536 Enable history expansion. History expansion is off by default.
22538 @item set history expansion off
22539 Disable history expansion.
22542 @kindex show history
22544 @itemx show history filename
22545 @itemx show history save
22546 @itemx show history size
22547 @itemx show history expansion
22548 These commands display the state of the @value{GDBN} history parameters.
22549 @code{show history} by itself displays all four states.
22554 @kindex show commands
22555 @cindex show last commands
22556 @cindex display command history
22557 @item show commands
22558 Display the last ten commands in the command history.
22560 @item show commands @var{n}
22561 Print ten commands centered on command number @var{n}.
22563 @item show commands +
22564 Print ten commands just after the commands last printed.
22568 @section Screen Size
22569 @cindex size of screen
22570 @cindex screen size
22573 @cindex pauses in output
22575 Certain commands to @value{GDBN} may produce large amounts of
22576 information output to the screen. To help you read all of it,
22577 @value{GDBN} pauses and asks you for input at the end of each page of
22578 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22579 to discard the remaining output. Also, the screen width setting
22580 determines when to wrap lines of output. Depending on what is being
22581 printed, @value{GDBN} tries to break the line at a readable place,
22582 rather than simply letting it overflow onto the following line.
22584 Normally @value{GDBN} knows the size of the screen from the terminal
22585 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22586 together with the value of the @code{TERM} environment variable and the
22587 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22588 you can override it with the @code{set height} and @code{set
22595 @kindex show height
22596 @item set height @var{lpp}
22597 @itemx set height unlimited
22599 @itemx set width @var{cpl}
22600 @itemx set width unlimited
22602 These @code{set} commands specify a screen height of @var{lpp} lines and
22603 a screen width of @var{cpl} characters. The associated @code{show}
22604 commands display the current settings.
22606 If you specify a height of either @code{unlimited} or zero lines,
22607 @value{GDBN} does not pause during output no matter how long the
22608 output is. This is useful if output is to a file or to an editor
22611 Likewise, you can specify @samp{set width unlimited} or @samp{set
22612 width 0} to prevent @value{GDBN} from wrapping its output.
22614 @item set pagination on
22615 @itemx set pagination off
22616 @kindex set pagination
22617 Turn the output pagination on or off; the default is on. Turning
22618 pagination off is the alternative to @code{set height unlimited}. Note that
22619 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22620 Options, -batch}) also automatically disables pagination.
22622 @item show pagination
22623 @kindex show pagination
22624 Show the current pagination mode.
22629 @cindex number representation
22630 @cindex entering numbers
22632 You can always enter numbers in octal, decimal, or hexadecimal in
22633 @value{GDBN} by the usual conventions: octal numbers begin with
22634 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22635 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22636 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22637 10; likewise, the default display for numbers---when no particular
22638 format is specified---is base 10. You can change the default base for
22639 both input and output with the commands described below.
22642 @kindex set input-radix
22643 @item set input-radix @var{base}
22644 Set the default base for numeric input. Supported choices
22645 for @var{base} are decimal 8, 10, or 16. The base must itself be
22646 specified either unambiguously or using the current input radix; for
22650 set input-radix 012
22651 set input-radix 10.
22652 set input-radix 0xa
22656 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22657 leaves the input radix unchanged, no matter what it was, since
22658 @samp{10}, being without any leading or trailing signs of its base, is
22659 interpreted in the current radix. Thus, if the current radix is 16,
22660 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22663 @kindex set output-radix
22664 @item set output-radix @var{base}
22665 Set the default base for numeric display. Supported choices
22666 for @var{base} are decimal 8, 10, or 16. The base must itself be
22667 specified either unambiguously or using the current input radix.
22669 @kindex show input-radix
22670 @item show input-radix
22671 Display the current default base for numeric input.
22673 @kindex show output-radix
22674 @item show output-radix
22675 Display the current default base for numeric display.
22677 @item set radix @r{[}@var{base}@r{]}
22681 These commands set and show the default base for both input and output
22682 of numbers. @code{set radix} sets the radix of input and output to
22683 the same base; without an argument, it resets the radix back to its
22684 default value of 10.
22689 @section Configuring the Current ABI
22691 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22692 application automatically. However, sometimes you need to override its
22693 conclusions. Use these commands to manage @value{GDBN}'s view of the
22699 @cindex Newlib OS ABI and its influence on the longjmp handling
22701 One @value{GDBN} configuration can debug binaries for multiple operating
22702 system targets, either via remote debugging or native emulation.
22703 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22704 but you can override its conclusion using the @code{set osabi} command.
22705 One example where this is useful is in debugging of binaries which use
22706 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22707 not have the same identifying marks that the standard C library for your
22710 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22711 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22712 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22713 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22717 Show the OS ABI currently in use.
22720 With no argument, show the list of registered available OS ABI's.
22722 @item set osabi @var{abi}
22723 Set the current OS ABI to @var{abi}.
22726 @cindex float promotion
22728 Generally, the way that an argument of type @code{float} is passed to a
22729 function depends on whether the function is prototyped. For a prototyped
22730 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22731 according to the architecture's convention for @code{float}. For unprototyped
22732 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22733 @code{double} and then passed.
22735 Unfortunately, some forms of debug information do not reliably indicate whether
22736 a function is prototyped. If @value{GDBN} calls a function that is not marked
22737 as prototyped, it consults @kbd{set coerce-float-to-double}.
22740 @kindex set coerce-float-to-double
22741 @item set coerce-float-to-double
22742 @itemx set coerce-float-to-double on
22743 Arguments of type @code{float} will be promoted to @code{double} when passed
22744 to an unprototyped function. This is the default setting.
22746 @item set coerce-float-to-double off
22747 Arguments of type @code{float} will be passed directly to unprototyped
22750 @kindex show coerce-float-to-double
22751 @item show coerce-float-to-double
22752 Show the current setting of promoting @code{float} to @code{double}.
22756 @kindex show cp-abi
22757 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22758 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22759 used to build your application. @value{GDBN} only fully supports
22760 programs with a single C@t{++} ABI; if your program contains code using
22761 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22762 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22763 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22764 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22765 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22766 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22771 Show the C@t{++} ABI currently in use.
22774 With no argument, show the list of supported C@t{++} ABI's.
22776 @item set cp-abi @var{abi}
22777 @itemx set cp-abi auto
22778 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22782 @section Automatically loading associated files
22783 @cindex auto-loading
22785 @value{GDBN} sometimes reads files with commands and settings automatically,
22786 without being explicitly told so by the user. We call this feature
22787 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22788 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22789 results or introduce security risks (e.g., if the file comes from untrusted
22793 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22794 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22796 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22797 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22800 There are various kinds of files @value{GDBN} can automatically load.
22801 In addition to these files, @value{GDBN} supports auto-loading code written
22802 in various extension languages. @xref{Auto-loading extensions}.
22804 Note that loading of these associated files (including the local @file{.gdbinit}
22805 file) requires accordingly configured @code{auto-load safe-path}
22806 (@pxref{Auto-loading safe path}).
22808 For these reasons, @value{GDBN} includes commands and options to let you
22809 control when to auto-load files and which files should be auto-loaded.
22812 @anchor{set auto-load off}
22813 @kindex set auto-load off
22814 @item set auto-load off
22815 Globally disable loading of all auto-loaded files.
22816 You may want to use this command with the @samp{-iex} option
22817 (@pxref{Option -init-eval-command}) such as:
22819 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22822 Be aware that system init file (@pxref{System-wide configuration})
22823 and init files from your home directory (@pxref{Home Directory Init File})
22824 still get read (as they come from generally trusted directories).
22825 To prevent @value{GDBN} from auto-loading even those init files, use the
22826 @option{-nx} option (@pxref{Mode Options}), in addition to
22827 @code{set auto-load no}.
22829 @anchor{show auto-load}
22830 @kindex show auto-load
22831 @item show auto-load
22832 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22836 (gdb) show auto-load
22837 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22838 libthread-db: Auto-loading of inferior specific libthread_db is on.
22839 local-gdbinit: Auto-loading of .gdbinit script from current directory
22841 python-scripts: Auto-loading of Python scripts is on.
22842 safe-path: List of directories from which it is safe to auto-load files
22843 is $debugdir:$datadir/auto-load.
22844 scripts-directory: List of directories from which to load auto-loaded scripts
22845 is $debugdir:$datadir/auto-load.
22848 @anchor{info auto-load}
22849 @kindex info auto-load
22850 @item info auto-load
22851 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22855 (gdb) info auto-load
22858 Yes /home/user/gdb/gdb-gdb.gdb
22859 libthread-db: No auto-loaded libthread-db.
22860 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22864 Yes /home/user/gdb/gdb-gdb.py
22868 These are @value{GDBN} control commands for the auto-loading:
22870 @multitable @columnfractions .5 .5
22871 @item @xref{set auto-load off}.
22872 @tab Disable auto-loading globally.
22873 @item @xref{show auto-load}.
22874 @tab Show setting of all kinds of files.
22875 @item @xref{info auto-load}.
22876 @tab Show state of all kinds of files.
22877 @item @xref{set auto-load gdb-scripts}.
22878 @tab Control for @value{GDBN} command scripts.
22879 @item @xref{show auto-load gdb-scripts}.
22880 @tab Show setting of @value{GDBN} command scripts.
22881 @item @xref{info auto-load gdb-scripts}.
22882 @tab Show state of @value{GDBN} command scripts.
22883 @item @xref{set auto-load python-scripts}.
22884 @tab Control for @value{GDBN} Python scripts.
22885 @item @xref{show auto-load python-scripts}.
22886 @tab Show setting of @value{GDBN} Python scripts.
22887 @item @xref{info auto-load python-scripts}.
22888 @tab Show state of @value{GDBN} Python scripts.
22889 @item @xref{set auto-load guile-scripts}.
22890 @tab Control for @value{GDBN} Guile scripts.
22891 @item @xref{show auto-load guile-scripts}.
22892 @tab Show setting of @value{GDBN} Guile scripts.
22893 @item @xref{info auto-load guile-scripts}.
22894 @tab Show state of @value{GDBN} Guile scripts.
22895 @item @xref{set auto-load scripts-directory}.
22896 @tab Control for @value{GDBN} auto-loaded scripts location.
22897 @item @xref{show auto-load scripts-directory}.
22898 @tab Show @value{GDBN} auto-loaded scripts location.
22899 @item @xref{add-auto-load-scripts-directory}.
22900 @tab Add directory for auto-loaded scripts location list.
22901 @item @xref{set auto-load local-gdbinit}.
22902 @tab Control for init file in the current directory.
22903 @item @xref{show auto-load local-gdbinit}.
22904 @tab Show setting of init file in the current directory.
22905 @item @xref{info auto-load local-gdbinit}.
22906 @tab Show state of init file in the current directory.
22907 @item @xref{set auto-load libthread-db}.
22908 @tab Control for thread debugging library.
22909 @item @xref{show auto-load libthread-db}.
22910 @tab Show setting of thread debugging library.
22911 @item @xref{info auto-load libthread-db}.
22912 @tab Show state of thread debugging library.
22913 @item @xref{set auto-load safe-path}.
22914 @tab Control directories trusted for automatic loading.
22915 @item @xref{show auto-load safe-path}.
22916 @tab Show directories trusted for automatic loading.
22917 @item @xref{add-auto-load-safe-path}.
22918 @tab Add directory trusted for automatic loading.
22921 @node Init File in the Current Directory
22922 @subsection Automatically loading init file in the current directory
22923 @cindex auto-loading init file in the current directory
22925 By default, @value{GDBN} reads and executes the canned sequences of commands
22926 from init file (if any) in the current working directory,
22927 see @ref{Init File in the Current Directory during Startup}.
22929 Note that loading of this local @file{.gdbinit} file also requires accordingly
22930 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22933 @anchor{set auto-load local-gdbinit}
22934 @kindex set auto-load local-gdbinit
22935 @item set auto-load local-gdbinit [on|off]
22936 Enable or disable the auto-loading of canned sequences of commands
22937 (@pxref{Sequences}) found in init file in the current directory.
22939 @anchor{show auto-load local-gdbinit}
22940 @kindex show auto-load local-gdbinit
22941 @item show auto-load local-gdbinit
22942 Show whether auto-loading of canned sequences of commands from init file in the
22943 current directory is enabled or disabled.
22945 @anchor{info auto-load local-gdbinit}
22946 @kindex info auto-load local-gdbinit
22947 @item info auto-load local-gdbinit
22948 Print whether canned sequences of commands from init file in the
22949 current directory have been auto-loaded.
22952 @node libthread_db.so.1 file
22953 @subsection Automatically loading thread debugging library
22954 @cindex auto-loading libthread_db.so.1
22956 This feature is currently present only on @sc{gnu}/Linux native hosts.
22958 @value{GDBN} reads in some cases thread debugging library from places specific
22959 to the inferior (@pxref{set libthread-db-search-path}).
22961 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22962 without checking this @samp{set auto-load libthread-db} switch as system
22963 libraries have to be trusted in general. In all other cases of
22964 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22965 auto-load libthread-db} is enabled before trying to open such thread debugging
22968 Note that loading of this debugging library also requires accordingly configured
22969 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22972 @anchor{set auto-load libthread-db}
22973 @kindex set auto-load libthread-db
22974 @item set auto-load libthread-db [on|off]
22975 Enable or disable the auto-loading of inferior specific thread debugging library.
22977 @anchor{show auto-load libthread-db}
22978 @kindex show auto-load libthread-db
22979 @item show auto-load libthread-db
22980 Show whether auto-loading of inferior specific thread debugging library is
22981 enabled or disabled.
22983 @anchor{info auto-load libthread-db}
22984 @kindex info auto-load libthread-db
22985 @item info auto-load libthread-db
22986 Print the list of all loaded inferior specific thread debugging libraries and
22987 for each such library print list of inferior @var{pid}s using it.
22990 @node Auto-loading safe path
22991 @subsection Security restriction for auto-loading
22992 @cindex auto-loading safe-path
22994 As the files of inferior can come from untrusted source (such as submitted by
22995 an application user) @value{GDBN} does not always load any files automatically.
22996 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22997 directories trusted for loading files not explicitly requested by user.
22998 Each directory can also be a shell wildcard pattern.
23000 If the path is not set properly you will see a warning and the file will not
23005 Reading symbols from /home/user/gdb/gdb...done.
23006 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23007 declined by your `auto-load safe-path' set
23008 to "$debugdir:$datadir/auto-load".
23009 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23010 declined by your `auto-load safe-path' set
23011 to "$debugdir:$datadir/auto-load".
23015 To instruct @value{GDBN} to go ahead and use the init files anyway,
23016 invoke @value{GDBN} like this:
23019 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23022 The list of trusted directories is controlled by the following commands:
23025 @anchor{set auto-load safe-path}
23026 @kindex set auto-load safe-path
23027 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23028 Set the list of directories (and their subdirectories) trusted for automatic
23029 loading and execution of scripts. You can also enter a specific trusted file.
23030 Each directory can also be a shell wildcard pattern; wildcards do not match
23031 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23032 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23033 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23034 its default value as specified during @value{GDBN} compilation.
23036 The list of directories uses path separator (@samp{:} on GNU and Unix
23037 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23038 to the @env{PATH} environment variable.
23040 @anchor{show auto-load safe-path}
23041 @kindex show auto-load safe-path
23042 @item show auto-load safe-path
23043 Show the list of directories trusted for automatic loading and execution of
23046 @anchor{add-auto-load-safe-path}
23047 @kindex add-auto-load-safe-path
23048 @item add-auto-load-safe-path
23049 Add an entry (or list of entries) to the list of directories trusted for
23050 automatic loading and execution of scripts. Multiple entries may be delimited
23051 by the host platform path separator in use.
23054 This variable defaults to what @code{--with-auto-load-dir} has been configured
23055 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23056 substitution applies the same as for @ref{set auto-load scripts-directory}.
23057 The default @code{set auto-load safe-path} value can be also overriden by
23058 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23060 Setting this variable to @file{/} disables this security protection,
23061 corresponding @value{GDBN} configuration option is
23062 @option{--without-auto-load-safe-path}.
23063 This variable is supposed to be set to the system directories writable by the
23064 system superuser only. Users can add their source directories in init files in
23065 their home directories (@pxref{Home Directory Init File}). See also deprecated
23066 init file in the current directory
23067 (@pxref{Init File in the Current Directory during Startup}).
23069 To force @value{GDBN} to load the files it declined to load in the previous
23070 example, you could use one of the following ways:
23073 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23074 Specify this trusted directory (or a file) as additional component of the list.
23075 You have to specify also any existing directories displayed by
23076 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23078 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23079 Specify this directory as in the previous case but just for a single
23080 @value{GDBN} session.
23082 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23083 Disable auto-loading safety for a single @value{GDBN} session.
23084 This assumes all the files you debug during this @value{GDBN} session will come
23085 from trusted sources.
23087 @item @kbd{./configure --without-auto-load-safe-path}
23088 During compilation of @value{GDBN} you may disable any auto-loading safety.
23089 This assumes all the files you will ever debug with this @value{GDBN} come from
23093 On the other hand you can also explicitly forbid automatic files loading which
23094 also suppresses any such warning messages:
23097 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23098 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23100 @item @file{~/.gdbinit}: @samp{set auto-load no}
23101 Disable auto-loading globally for the user
23102 (@pxref{Home Directory Init File}). While it is improbable, you could also
23103 use system init file instead (@pxref{System-wide configuration}).
23106 This setting applies to the file names as entered by user. If no entry matches
23107 @value{GDBN} tries as a last resort to also resolve all the file names into
23108 their canonical form (typically resolving symbolic links) and compare the
23109 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23110 own before starting the comparison so a canonical form of directories is
23111 recommended to be entered.
23113 @node Auto-loading verbose mode
23114 @subsection Displaying files tried for auto-load
23115 @cindex auto-loading verbose mode
23117 For better visibility of all the file locations where you can place scripts to
23118 be auto-loaded with inferior --- or to protect yourself against accidental
23119 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23120 all the files attempted to be loaded. Both existing and non-existing files may
23123 For example the list of directories from which it is safe to auto-load files
23124 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23125 may not be too obvious while setting it up.
23128 (gdb) set debug auto-load on
23129 (gdb) file ~/src/t/true
23130 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23131 for objfile "/tmp/true".
23132 auto-load: Updating directories of "/usr:/opt".
23133 auto-load: Using directory "/usr".
23134 auto-load: Using directory "/opt".
23135 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23136 by your `auto-load safe-path' set to "/usr:/opt".
23140 @anchor{set debug auto-load}
23141 @kindex set debug auto-load
23142 @item set debug auto-load [on|off]
23143 Set whether to print the filenames attempted to be auto-loaded.
23145 @anchor{show debug auto-load}
23146 @kindex show debug auto-load
23147 @item show debug auto-load
23148 Show whether printing of the filenames attempted to be auto-loaded is turned
23152 @node Messages/Warnings
23153 @section Optional Warnings and Messages
23155 @cindex verbose operation
23156 @cindex optional warnings
23157 By default, @value{GDBN} is silent about its inner workings. If you are
23158 running on a slow machine, you may want to use the @code{set verbose}
23159 command. This makes @value{GDBN} tell you when it does a lengthy
23160 internal operation, so you will not think it has crashed.
23162 Currently, the messages controlled by @code{set verbose} are those
23163 which announce that the symbol table for a source file is being read;
23164 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23167 @kindex set verbose
23168 @item set verbose on
23169 Enables @value{GDBN} output of certain informational messages.
23171 @item set verbose off
23172 Disables @value{GDBN} output of certain informational messages.
23174 @kindex show verbose
23176 Displays whether @code{set verbose} is on or off.
23179 By default, if @value{GDBN} encounters bugs in the symbol table of an
23180 object file, it is silent; but if you are debugging a compiler, you may
23181 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23186 @kindex set complaints
23187 @item set complaints @var{limit}
23188 Permits @value{GDBN} to output @var{limit} complaints about each type of
23189 unusual symbols before becoming silent about the problem. Set
23190 @var{limit} to zero to suppress all complaints; set it to a large number
23191 to prevent complaints from being suppressed.
23193 @kindex show complaints
23194 @item show complaints
23195 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23199 @anchor{confirmation requests}
23200 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23201 lot of stupid questions to confirm certain commands. For example, if
23202 you try to run a program which is already running:
23206 The program being debugged has been started already.
23207 Start it from the beginning? (y or n)
23210 If you are willing to unflinchingly face the consequences of your own
23211 commands, you can disable this ``feature'':
23215 @kindex set confirm
23217 @cindex confirmation
23218 @cindex stupid questions
23219 @item set confirm off
23220 Disables confirmation requests. Note that running @value{GDBN} with
23221 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23222 automatically disables confirmation requests.
23224 @item set confirm on
23225 Enables confirmation requests (the default).
23227 @kindex show confirm
23229 Displays state of confirmation requests.
23233 @cindex command tracing
23234 If you need to debug user-defined commands or sourced files you may find it
23235 useful to enable @dfn{command tracing}. In this mode each command will be
23236 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23237 quantity denoting the call depth of each command.
23240 @kindex set trace-commands
23241 @cindex command scripts, debugging
23242 @item set trace-commands on
23243 Enable command tracing.
23244 @item set trace-commands off
23245 Disable command tracing.
23246 @item show trace-commands
23247 Display the current state of command tracing.
23250 @node Debugging Output
23251 @section Optional Messages about Internal Happenings
23252 @cindex optional debugging messages
23254 @value{GDBN} has commands that enable optional debugging messages from
23255 various @value{GDBN} subsystems; normally these commands are of
23256 interest to @value{GDBN} maintainers, or when reporting a bug. This
23257 section documents those commands.
23260 @kindex set exec-done-display
23261 @item set exec-done-display
23262 Turns on or off the notification of asynchronous commands'
23263 completion. When on, @value{GDBN} will print a message when an
23264 asynchronous command finishes its execution. The default is off.
23265 @kindex show exec-done-display
23266 @item show exec-done-display
23267 Displays the current setting of asynchronous command completion
23270 @cindex ARM AArch64
23271 @item set debug aarch64
23272 Turns on or off display of debugging messages related to ARM AArch64.
23273 The default is off.
23275 @item show debug aarch64
23276 Displays the current state of displaying debugging messages related to
23278 @cindex gdbarch debugging info
23279 @cindex architecture debugging info
23280 @item set debug arch
23281 Turns on or off display of gdbarch debugging info. The default is off
23282 @item show debug arch
23283 Displays the current state of displaying gdbarch debugging info.
23284 @item set debug aix-solib
23285 @cindex AIX shared library debugging
23286 Control display of debugging messages from the AIX shared library
23287 support module. The default is off.
23288 @item show debug aix-thread
23289 Show the current state of displaying AIX shared library debugging messages.
23290 @item set debug aix-thread
23291 @cindex AIX threads
23292 Display debugging messages about inner workings of the AIX thread
23294 @item show debug aix-thread
23295 Show the current state of AIX thread debugging info display.
23296 @item set debug check-physname
23298 Check the results of the ``physname'' computation. When reading DWARF
23299 debugging information for C@t{++}, @value{GDBN} attempts to compute
23300 each entity's name. @value{GDBN} can do this computation in two
23301 different ways, depending on exactly what information is present.
23302 When enabled, this setting causes @value{GDBN} to compute the names
23303 both ways and display any discrepancies.
23304 @item show debug check-physname
23305 Show the current state of ``physname'' checking.
23306 @item set debug coff-pe-read
23307 @cindex COFF/PE exported symbols
23308 Control display of debugging messages related to reading of COFF/PE
23309 exported symbols. The default is off.
23310 @item show debug coff-pe-read
23311 Displays the current state of displaying debugging messages related to
23312 reading of COFF/PE exported symbols.
23313 @item set debug dwarf-die
23315 Dump DWARF DIEs after they are read in.
23316 The value is the number of nesting levels to print.
23317 A value of zero turns off the display.
23318 @item show debug dwarf-die
23319 Show the current state of DWARF DIE debugging.
23320 @item set debug dwarf-line
23321 @cindex DWARF Line Tables
23322 Turns on or off display of debugging messages related to reading
23323 DWARF line tables. The default is 0 (off).
23324 A value of 1 provides basic information.
23325 A value greater than 1 provides more verbose information.
23326 @item show debug dwarf-line
23327 Show the current state of DWARF line table debugging.
23328 @item set debug dwarf-read
23329 @cindex DWARF Reading
23330 Turns on or off display of debugging messages related to reading
23331 DWARF debug info. The default is 0 (off).
23332 A value of 1 provides basic information.
23333 A value greater than 1 provides more verbose information.
23334 @item show debug dwarf-read
23335 Show the current state of DWARF reader debugging.
23336 @item set debug displaced
23337 @cindex displaced stepping debugging info
23338 Turns on or off display of @value{GDBN} debugging info for the
23339 displaced stepping support. The default is off.
23340 @item show debug displaced
23341 Displays the current state of displaying @value{GDBN} debugging info
23342 related to displaced stepping.
23343 @item set debug event
23344 @cindex event debugging info
23345 Turns on or off display of @value{GDBN} event debugging info. The
23347 @item show debug event
23348 Displays the current state of displaying @value{GDBN} event debugging
23350 @item set debug expression
23351 @cindex expression debugging info
23352 Turns on or off display of debugging info about @value{GDBN}
23353 expression parsing. The default is off.
23354 @item show debug expression
23355 Displays the current state of displaying debugging info about
23356 @value{GDBN} expression parsing.
23357 @item set debug frame
23358 @cindex frame debugging info
23359 Turns on or off display of @value{GDBN} frame debugging info. The
23361 @item show debug frame
23362 Displays the current state of displaying @value{GDBN} frame debugging
23364 @item set debug gnu-nat
23365 @cindex @sc{gnu}/Hurd debug messages
23366 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23367 @item show debug gnu-nat
23368 Show the current state of @sc{gnu}/Hurd debugging messages.
23369 @item set debug infrun
23370 @cindex inferior debugging info
23371 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23372 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23373 for implementing operations such as single-stepping the inferior.
23374 @item show debug infrun
23375 Displays the current state of @value{GDBN} inferior debugging.
23376 @item set debug jit
23377 @cindex just-in-time compilation, debugging messages
23378 Turns on or off debugging messages from JIT debug support.
23379 @item show debug jit
23380 Displays the current state of @value{GDBN} JIT debugging.
23381 @item set debug lin-lwp
23382 @cindex @sc{gnu}/Linux LWP debug messages
23383 @cindex Linux lightweight processes
23384 Turns on or off debugging messages from the Linux LWP debug support.
23385 @item show debug lin-lwp
23386 Show the current state of Linux LWP debugging messages.
23387 @item set debug linux-namespaces
23388 @cindex @sc{gnu}/Linux namespaces debug messages
23389 Turns on or off debugging messages from the Linux namespaces debug support.
23390 @item show debug linux-namespaces
23391 Show the current state of Linux namespaces debugging messages.
23392 @item set debug mach-o
23393 @cindex Mach-O symbols processing
23394 Control display of debugging messages related to Mach-O symbols
23395 processing. The default is off.
23396 @item show debug mach-o
23397 Displays the current state of displaying debugging messages related to
23398 reading of COFF/PE exported symbols.
23399 @item set debug notification
23400 @cindex remote async notification debugging info
23401 Turns on or off debugging messages about remote async notification.
23402 The default is off.
23403 @item show debug notification
23404 Displays the current state of remote async notification debugging messages.
23405 @item set debug observer
23406 @cindex observer debugging info
23407 Turns on or off display of @value{GDBN} observer debugging. This
23408 includes info such as the notification of observable events.
23409 @item show debug observer
23410 Displays the current state of observer debugging.
23411 @item set debug overload
23412 @cindex C@t{++} overload debugging info
23413 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23414 info. This includes info such as ranking of functions, etc. The default
23416 @item show debug overload
23417 Displays the current state of displaying @value{GDBN} C@t{++} overload
23419 @cindex expression parser, debugging info
23420 @cindex debug expression parser
23421 @item set debug parser
23422 Turns on or off the display of expression parser debugging output.
23423 Internally, this sets the @code{yydebug} variable in the expression
23424 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23425 details. The default is off.
23426 @item show debug parser
23427 Show the current state of expression parser debugging.
23428 @cindex packets, reporting on stdout
23429 @cindex serial connections, debugging
23430 @cindex debug remote protocol
23431 @cindex remote protocol debugging
23432 @cindex display remote packets
23433 @item set debug remote
23434 Turns on or off display of reports on all packets sent back and forth across
23435 the serial line to the remote machine. The info is printed on the
23436 @value{GDBN} standard output stream. The default is off.
23437 @item show debug remote
23438 Displays the state of display of remote packets.
23439 @item set debug serial
23440 Turns on or off display of @value{GDBN} serial debugging info. The
23442 @item show debug serial
23443 Displays the current state of displaying @value{GDBN} serial debugging
23445 @item set debug solib-frv
23446 @cindex FR-V shared-library debugging
23447 Turns on or off debugging messages for FR-V shared-library code.
23448 @item show debug solib-frv
23449 Display the current state of FR-V shared-library code debugging
23451 @item set debug symbol-lookup
23452 @cindex symbol lookup
23453 Turns on or off display of debugging messages related to symbol lookup.
23454 The default is 0 (off).
23455 A value of 1 provides basic information.
23456 A value greater than 1 provides more verbose information.
23457 @item show debug symbol-lookup
23458 Show the current state of symbol lookup debugging messages.
23459 @item set debug symfile
23460 @cindex symbol file functions
23461 Turns on or off display of debugging messages related to symbol file functions.
23462 The default is off. @xref{Files}.
23463 @item show debug symfile
23464 Show the current state of symbol file debugging messages.
23465 @item set debug symtab-create
23466 @cindex symbol table creation
23467 Turns on or off display of debugging messages related to symbol table creation.
23468 The default is 0 (off).
23469 A value of 1 provides basic information.
23470 A value greater than 1 provides more verbose information.
23471 @item show debug symtab-create
23472 Show the current state of symbol table creation debugging.
23473 @item set debug target
23474 @cindex target debugging info
23475 Turns on or off display of @value{GDBN} target debugging info. This info
23476 includes what is going on at the target level of GDB, as it happens. The
23477 default is 0. Set it to 1 to track events, and to 2 to also track the
23478 value of large memory transfers.
23479 @item show debug target
23480 Displays the current state of displaying @value{GDBN} target debugging
23482 @item set debug timestamp
23483 @cindex timestampping debugging info
23484 Turns on or off display of timestamps with @value{GDBN} debugging info.
23485 When enabled, seconds and microseconds are displayed before each debugging
23487 @item show debug timestamp
23488 Displays the current state of displaying timestamps with @value{GDBN}
23490 @item set debug varobj
23491 @cindex variable object debugging info
23492 Turns on or off display of @value{GDBN} variable object debugging
23493 info. The default is off.
23494 @item show debug varobj
23495 Displays the current state of displaying @value{GDBN} variable object
23497 @item set debug xml
23498 @cindex XML parser debugging
23499 Turns on or off debugging messages for built-in XML parsers.
23500 @item show debug xml
23501 Displays the current state of XML debugging messages.
23504 @node Other Misc Settings
23505 @section Other Miscellaneous Settings
23506 @cindex miscellaneous settings
23509 @kindex set interactive-mode
23510 @item set interactive-mode
23511 If @code{on}, forces @value{GDBN} to assume that GDB was started
23512 in a terminal. In practice, this means that @value{GDBN} should wait
23513 for the user to answer queries generated by commands entered at
23514 the command prompt. If @code{off}, forces @value{GDBN} to operate
23515 in the opposite mode, and it uses the default answers to all queries.
23516 If @code{auto} (the default), @value{GDBN} tries to determine whether
23517 its standard input is a terminal, and works in interactive-mode if it
23518 is, non-interactively otherwise.
23520 In the vast majority of cases, the debugger should be able to guess
23521 correctly which mode should be used. But this setting can be useful
23522 in certain specific cases, such as running a MinGW @value{GDBN}
23523 inside a cygwin window.
23525 @kindex show interactive-mode
23526 @item show interactive-mode
23527 Displays whether the debugger is operating in interactive mode or not.
23530 @node Extending GDB
23531 @chapter Extending @value{GDBN}
23532 @cindex extending GDB
23534 @value{GDBN} provides several mechanisms for extension.
23535 @value{GDBN} also provides the ability to automatically load
23536 extensions when it reads a file for debugging. This allows the
23537 user to automatically customize @value{GDBN} for the program
23541 * Sequences:: Canned Sequences of @value{GDBN} Commands
23542 * Python:: Extending @value{GDBN} using Python
23543 * Guile:: Extending @value{GDBN} using Guile
23544 * Auto-loading extensions:: Automatically loading extensions
23545 * Multiple Extension Languages:: Working with multiple extension languages
23546 * Aliases:: Creating new spellings of existing commands
23549 To facilitate the use of extension languages, @value{GDBN} is capable
23550 of evaluating the contents of a file. When doing so, @value{GDBN}
23551 can recognize which extension language is being used by looking at
23552 the filename extension. Files with an unrecognized filename extension
23553 are always treated as a @value{GDBN} Command Files.
23554 @xref{Command Files,, Command files}.
23556 You can control how @value{GDBN} evaluates these files with the following
23560 @kindex set script-extension
23561 @kindex show script-extension
23562 @item set script-extension off
23563 All scripts are always evaluated as @value{GDBN} Command Files.
23565 @item set script-extension soft
23566 The debugger determines the scripting language based on filename
23567 extension. If this scripting language is supported, @value{GDBN}
23568 evaluates the script using that language. Otherwise, it evaluates
23569 the file as a @value{GDBN} Command File.
23571 @item set script-extension strict
23572 The debugger determines the scripting language based on filename
23573 extension, and evaluates the script using that language. If the
23574 language is not supported, then the evaluation fails.
23576 @item show script-extension
23577 Display the current value of the @code{script-extension} option.
23582 @section Canned Sequences of Commands
23584 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23585 Command Lists}), @value{GDBN} provides two ways to store sequences of
23586 commands for execution as a unit: user-defined commands and command
23590 * Define:: How to define your own commands
23591 * Hooks:: Hooks for user-defined commands
23592 * Command Files:: How to write scripts of commands to be stored in a file
23593 * Output:: Commands for controlled output
23594 * Auto-loading sequences:: Controlling auto-loaded command files
23598 @subsection User-defined Commands
23600 @cindex user-defined command
23601 @cindex arguments, to user-defined commands
23602 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23603 which you assign a new name as a command. This is done with the
23604 @code{define} command. User commands may accept up to 10 arguments
23605 separated by whitespace. Arguments are accessed within the user command
23606 via @code{$arg0@dots{}$arg9}. A trivial example:
23610 print $arg0 + $arg1 + $arg2
23615 To execute the command use:
23622 This defines the command @code{adder}, which prints the sum of
23623 its three arguments. Note the arguments are text substitutions, so they may
23624 reference variables, use complex expressions, or even perform inferior
23627 @cindex argument count in user-defined commands
23628 @cindex how many arguments (user-defined commands)
23629 In addition, @code{$argc} may be used to find out how many arguments have
23630 been passed. This expands to a number in the range 0@dots{}10.
23635 print $arg0 + $arg1
23638 print $arg0 + $arg1 + $arg2
23646 @item define @var{commandname}
23647 Define a command named @var{commandname}. If there is already a command
23648 by that name, you are asked to confirm that you want to redefine it.
23649 The argument @var{commandname} may be a bare command name consisting of letters,
23650 numbers, dashes, and underscores. It may also start with any predefined
23651 prefix command. For example, @samp{define target my-target} creates
23652 a user-defined @samp{target my-target} command.
23654 The definition of the command is made up of other @value{GDBN} command lines,
23655 which are given following the @code{define} command. The end of these
23656 commands is marked by a line containing @code{end}.
23659 @kindex end@r{ (user-defined commands)}
23660 @item document @var{commandname}
23661 Document the user-defined command @var{commandname}, so that it can be
23662 accessed by @code{help}. The command @var{commandname} must already be
23663 defined. This command reads lines of documentation just as @code{define}
23664 reads the lines of the command definition, ending with @code{end}.
23665 After the @code{document} command is finished, @code{help} on command
23666 @var{commandname} displays the documentation you have written.
23668 You may use the @code{document} command again to change the
23669 documentation of a command. Redefining the command with @code{define}
23670 does not change the documentation.
23672 @kindex dont-repeat
23673 @cindex don't repeat command
23675 Used inside a user-defined command, this tells @value{GDBN} that this
23676 command should not be repeated when the user hits @key{RET}
23677 (@pxref{Command Syntax, repeat last command}).
23679 @kindex help user-defined
23680 @item help user-defined
23681 List all user-defined commands and all python commands defined in class
23682 COMAND_USER. The first line of the documentation or docstring is
23687 @itemx show user @var{commandname}
23688 Display the @value{GDBN} commands used to define @var{commandname} (but
23689 not its documentation). If no @var{commandname} is given, display the
23690 definitions for all user-defined commands.
23691 This does not work for user-defined python commands.
23693 @cindex infinite recursion in user-defined commands
23694 @kindex show max-user-call-depth
23695 @kindex set max-user-call-depth
23696 @item show max-user-call-depth
23697 @itemx set max-user-call-depth
23698 The value of @code{max-user-call-depth} controls how many recursion
23699 levels are allowed in user-defined commands before @value{GDBN} suspects an
23700 infinite recursion and aborts the command.
23701 This does not apply to user-defined python commands.
23704 In addition to the above commands, user-defined commands frequently
23705 use control flow commands, described in @ref{Command Files}.
23707 When user-defined commands are executed, the
23708 commands of the definition are not printed. An error in any command
23709 stops execution of the user-defined command.
23711 If used interactively, commands that would ask for confirmation proceed
23712 without asking when used inside a user-defined command. Many @value{GDBN}
23713 commands that normally print messages to say what they are doing omit the
23714 messages when used in a user-defined command.
23717 @subsection User-defined Command Hooks
23718 @cindex command hooks
23719 @cindex hooks, for commands
23720 @cindex hooks, pre-command
23723 You may define @dfn{hooks}, which are a special kind of user-defined
23724 command. Whenever you run the command @samp{foo}, if the user-defined
23725 command @samp{hook-foo} exists, it is executed (with no arguments)
23726 before that command.
23728 @cindex hooks, post-command
23730 A hook may also be defined which is run after the command you executed.
23731 Whenever you run the command @samp{foo}, if the user-defined command
23732 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23733 that command. Post-execution hooks may exist simultaneously with
23734 pre-execution hooks, for the same command.
23736 It is valid for a hook to call the command which it hooks. If this
23737 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23739 @c It would be nice if hookpost could be passed a parameter indicating
23740 @c if the command it hooks executed properly or not. FIXME!
23742 @kindex stop@r{, a pseudo-command}
23743 In addition, a pseudo-command, @samp{stop} exists. Defining
23744 (@samp{hook-stop}) makes the associated commands execute every time
23745 execution stops in your program: before breakpoint commands are run,
23746 displays are printed, or the stack frame is printed.
23748 For example, to ignore @code{SIGALRM} signals while
23749 single-stepping, but treat them normally during normal execution,
23754 handle SIGALRM nopass
23758 handle SIGALRM pass
23761 define hook-continue
23762 handle SIGALRM pass
23766 As a further example, to hook at the beginning and end of the @code{echo}
23767 command, and to add extra text to the beginning and end of the message,
23775 define hookpost-echo
23779 (@value{GDBP}) echo Hello World
23780 <<<---Hello World--->>>
23785 You can define a hook for any single-word command in @value{GDBN}, but
23786 not for command aliases; you should define a hook for the basic command
23787 name, e.g.@: @code{backtrace} rather than @code{bt}.
23788 @c FIXME! So how does Joe User discover whether a command is an alias
23790 You can hook a multi-word command by adding @code{hook-} or
23791 @code{hookpost-} to the last word of the command, e.g.@:
23792 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23794 If an error occurs during the execution of your hook, execution of
23795 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23796 (before the command that you actually typed had a chance to run).
23798 If you try to define a hook which does not match any known command, you
23799 get a warning from the @code{define} command.
23801 @node Command Files
23802 @subsection Command Files
23804 @cindex command files
23805 @cindex scripting commands
23806 A command file for @value{GDBN} is a text file made of lines that are
23807 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23808 also be included. An empty line in a command file does nothing; it
23809 does not mean to repeat the last command, as it would from the
23812 You can request the execution of a command file with the @code{source}
23813 command. Note that the @code{source} command is also used to evaluate
23814 scripts that are not Command Files. The exact behavior can be configured
23815 using the @code{script-extension} setting.
23816 @xref{Extending GDB,, Extending GDB}.
23820 @cindex execute commands from a file
23821 @item source [-s] [-v] @var{filename}
23822 Execute the command file @var{filename}.
23825 The lines in a command file are generally executed sequentially,
23826 unless the order of execution is changed by one of the
23827 @emph{flow-control commands} described below. The commands are not
23828 printed as they are executed. An error in any command terminates
23829 execution of the command file and control is returned to the console.
23831 @value{GDBN} first searches for @var{filename} in the current directory.
23832 If the file is not found there, and @var{filename} does not specify a
23833 directory, then @value{GDBN} also looks for the file on the source search path
23834 (specified with the @samp{directory} command);
23835 except that @file{$cdir} is not searched because the compilation directory
23836 is not relevant to scripts.
23838 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23839 on the search path even if @var{filename} specifies a directory.
23840 The search is done by appending @var{filename} to each element of the
23841 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23842 and the search path contains @file{/home/user} then @value{GDBN} will
23843 look for the script @file{/home/user/mylib/myscript}.
23844 The search is also done if @var{filename} is an absolute path.
23845 For example, if @var{filename} is @file{/tmp/myscript} and
23846 the search path contains @file{/home/user} then @value{GDBN} will
23847 look for the script @file{/home/user/tmp/myscript}.
23848 For DOS-like systems, if @var{filename} contains a drive specification,
23849 it is stripped before concatenation. For example, if @var{filename} is
23850 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23851 will look for the script @file{c:/tmp/myscript}.
23853 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23854 each command as it is executed. The option must be given before
23855 @var{filename}, and is interpreted as part of the filename anywhere else.
23857 Commands that would ask for confirmation if used interactively proceed
23858 without asking when used in a command file. Many @value{GDBN} commands that
23859 normally print messages to say what they are doing omit the messages
23860 when called from command files.
23862 @value{GDBN} also accepts command input from standard input. In this
23863 mode, normal output goes to standard output and error output goes to
23864 standard error. Errors in a command file supplied on standard input do
23865 not terminate execution of the command file---execution continues with
23869 gdb < cmds > log 2>&1
23872 (The syntax above will vary depending on the shell used.) This example
23873 will execute commands from the file @file{cmds}. All output and errors
23874 would be directed to @file{log}.
23876 Since commands stored on command files tend to be more general than
23877 commands typed interactively, they frequently need to deal with
23878 complicated situations, such as different or unexpected values of
23879 variables and symbols, changes in how the program being debugged is
23880 built, etc. @value{GDBN} provides a set of flow-control commands to
23881 deal with these complexities. Using these commands, you can write
23882 complex scripts that loop over data structures, execute commands
23883 conditionally, etc.
23890 This command allows to include in your script conditionally executed
23891 commands. The @code{if} command takes a single argument, which is an
23892 expression to evaluate. It is followed by a series of commands that
23893 are executed only if the expression is true (its value is nonzero).
23894 There can then optionally be an @code{else} line, followed by a series
23895 of commands that are only executed if the expression was false. The
23896 end of the list is marked by a line containing @code{end}.
23900 This command allows to write loops. Its syntax is similar to
23901 @code{if}: the command takes a single argument, which is an expression
23902 to evaluate, and must be followed by the commands to execute, one per
23903 line, terminated by an @code{end}. These commands are called the
23904 @dfn{body} of the loop. The commands in the body of @code{while} are
23905 executed repeatedly as long as the expression evaluates to true.
23909 This command exits the @code{while} loop in whose body it is included.
23910 Execution of the script continues after that @code{while}s @code{end}
23913 @kindex loop_continue
23914 @item loop_continue
23915 This command skips the execution of the rest of the body of commands
23916 in the @code{while} loop in whose body it is included. Execution
23917 branches to the beginning of the @code{while} loop, where it evaluates
23918 the controlling expression.
23920 @kindex end@r{ (if/else/while commands)}
23922 Terminate the block of commands that are the body of @code{if},
23923 @code{else}, or @code{while} flow-control commands.
23928 @subsection Commands for Controlled Output
23930 During the execution of a command file or a user-defined command, normal
23931 @value{GDBN} output is suppressed; the only output that appears is what is
23932 explicitly printed by the commands in the definition. This section
23933 describes three commands useful for generating exactly the output you
23938 @item echo @var{text}
23939 @c I do not consider backslash-space a standard C escape sequence
23940 @c because it is not in ANSI.
23941 Print @var{text}. Nonprinting characters can be included in
23942 @var{text} using C escape sequences, such as @samp{\n} to print a
23943 newline. @strong{No newline is printed unless you specify one.}
23944 In addition to the standard C escape sequences, a backslash followed
23945 by a space stands for a space. This is useful for displaying a
23946 string with spaces at the beginning or the end, since leading and
23947 trailing spaces are otherwise trimmed from all arguments.
23948 To print @samp{@w{ }and foo =@w{ }}, use the command
23949 @samp{echo \@w{ }and foo = \@w{ }}.
23951 A backslash at the end of @var{text} can be used, as in C, to continue
23952 the command onto subsequent lines. For example,
23955 echo This is some text\n\
23956 which is continued\n\
23957 onto several lines.\n
23960 produces the same output as
23963 echo This is some text\n
23964 echo which is continued\n
23965 echo onto several lines.\n
23969 @item output @var{expression}
23970 Print the value of @var{expression} and nothing but that value: no
23971 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23972 value history either. @xref{Expressions, ,Expressions}, for more information
23975 @item output/@var{fmt} @var{expression}
23976 Print the value of @var{expression} in format @var{fmt}. You can use
23977 the same formats as for @code{print}. @xref{Output Formats,,Output
23978 Formats}, for more information.
23981 @item printf @var{template}, @var{expressions}@dots{}
23982 Print the values of one or more @var{expressions} under the control of
23983 the string @var{template}. To print several values, make
23984 @var{expressions} be a comma-separated list of individual expressions,
23985 which may be either numbers or pointers. Their values are printed as
23986 specified by @var{template}, exactly as a C program would do by
23987 executing the code below:
23990 printf (@var{template}, @var{expressions}@dots{});
23993 As in @code{C} @code{printf}, ordinary characters in @var{template}
23994 are printed verbatim, while @dfn{conversion specification} introduced
23995 by the @samp{%} character cause subsequent @var{expressions} to be
23996 evaluated, their values converted and formatted according to type and
23997 style information encoded in the conversion specifications, and then
24000 For example, you can print two values in hex like this:
24003 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24006 @code{printf} supports all the standard @code{C} conversion
24007 specifications, including the flags and modifiers between the @samp{%}
24008 character and the conversion letter, with the following exceptions:
24012 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24015 The modifier @samp{*} is not supported for specifying precision or
24019 The @samp{'} flag (for separation of digits into groups according to
24020 @code{LC_NUMERIC'}) is not supported.
24023 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24027 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24030 The conversion letters @samp{a} and @samp{A} are not supported.
24034 Note that the @samp{ll} type modifier is supported only if the
24035 underlying @code{C} implementation used to build @value{GDBN} supports
24036 the @code{long long int} type, and the @samp{L} type modifier is
24037 supported only if @code{long double} type is available.
24039 As in @code{C}, @code{printf} supports simple backslash-escape
24040 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24041 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24042 single character. Octal and hexadecimal escape sequences are not
24045 Additionally, @code{printf} supports conversion specifications for DFP
24046 (@dfn{Decimal Floating Point}) types using the following length modifiers
24047 together with a floating point specifier.
24052 @samp{H} for printing @code{Decimal32} types.
24055 @samp{D} for printing @code{Decimal64} types.
24058 @samp{DD} for printing @code{Decimal128} types.
24061 If the underlying @code{C} implementation used to build @value{GDBN} has
24062 support for the three length modifiers for DFP types, other modifiers
24063 such as width and precision will also be available for @value{GDBN} to use.
24065 In case there is no such @code{C} support, no additional modifiers will be
24066 available and the value will be printed in the standard way.
24068 Here's an example of printing DFP types using the above conversion letters:
24070 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24074 @item eval @var{template}, @var{expressions}@dots{}
24075 Convert the values of one or more @var{expressions} under the control of
24076 the string @var{template} to a command line, and call it.
24080 @node Auto-loading sequences
24081 @subsection Controlling auto-loading native @value{GDBN} scripts
24082 @cindex native script auto-loading
24084 When a new object file is read (for example, due to the @code{file}
24085 command, or because the inferior has loaded a shared library),
24086 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24087 @xref{Auto-loading extensions}.
24089 Auto-loading can be enabled or disabled,
24090 and the list of auto-loaded scripts can be printed.
24093 @anchor{set auto-load gdb-scripts}
24094 @kindex set auto-load gdb-scripts
24095 @item set auto-load gdb-scripts [on|off]
24096 Enable or disable the auto-loading of canned sequences of commands scripts.
24098 @anchor{show auto-load gdb-scripts}
24099 @kindex show auto-load gdb-scripts
24100 @item show auto-load gdb-scripts
24101 Show whether auto-loading of canned sequences of commands scripts is enabled or
24104 @anchor{info auto-load gdb-scripts}
24105 @kindex info auto-load gdb-scripts
24106 @cindex print list of auto-loaded canned sequences of commands scripts
24107 @item info auto-load gdb-scripts [@var{regexp}]
24108 Print the list of all canned sequences of commands scripts that @value{GDBN}
24112 If @var{regexp} is supplied only canned sequences of commands scripts with
24113 matching names are printed.
24115 @c Python docs live in a separate file.
24116 @include python.texi
24118 @c Guile docs live in a separate file.
24119 @include guile.texi
24121 @node Auto-loading extensions
24122 @section Auto-loading extensions
24123 @cindex auto-loading extensions
24125 @value{GDBN} provides two mechanisms for automatically loading extensions
24126 when a new object file is read (for example, due to the @code{file}
24127 command, or because the inferior has loaded a shared library):
24128 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24129 section of modern file formats like ELF.
24132 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24133 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24134 * Which flavor to choose?::
24137 The auto-loading feature is useful for supplying application-specific
24138 debugging commands and features.
24140 Auto-loading can be enabled or disabled,
24141 and the list of auto-loaded scripts can be printed.
24142 See the @samp{auto-loading} section of each extension language
24143 for more information.
24144 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24145 For Python files see @ref{Python Auto-loading}.
24147 Note that loading of this script file also requires accordingly configured
24148 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24150 @node objfile-gdbdotext file
24151 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24152 @cindex @file{@var{objfile}-gdb.gdb}
24153 @cindex @file{@var{objfile}-gdb.py}
24154 @cindex @file{@var{objfile}-gdb.scm}
24156 When a new object file is read, @value{GDBN} looks for a file named
24157 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24158 where @var{objfile} is the object file's name and
24159 where @var{ext} is the file extension for the extension language:
24162 @item @file{@var{objfile}-gdb.gdb}
24163 GDB's own command language
24164 @item @file{@var{objfile}-gdb.py}
24166 @item @file{@var{objfile}-gdb.scm}
24170 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24171 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24172 components, and appending the @file{-gdb.@var{ext}} suffix.
24173 If this file exists and is readable, @value{GDBN} will evaluate it as a
24174 script in the specified extension language.
24176 If this file does not exist, then @value{GDBN} will look for
24177 @var{script-name} file in all of the directories as specified below.
24179 Note that loading of these files requires an accordingly configured
24180 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24182 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24183 scripts normally according to its @file{.exe} filename. But if no scripts are
24184 found @value{GDBN} also tries script filenames matching the object file without
24185 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24186 is attempted on any platform. This makes the script filenames compatible
24187 between Unix and MS-Windows hosts.
24190 @anchor{set auto-load scripts-directory}
24191 @kindex set auto-load scripts-directory
24192 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24193 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24194 may be delimited by the host platform path separator in use
24195 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24197 Each entry here needs to be covered also by the security setting
24198 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24200 @anchor{with-auto-load-dir}
24201 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24202 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24203 configuration option @option{--with-auto-load-dir}.
24205 Any reference to @file{$debugdir} will get replaced by
24206 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24207 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24208 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24209 @file{$datadir} must be placed as a directory component --- either alone or
24210 delimited by @file{/} or @file{\} directory separators, depending on the host
24213 The list of directories uses path separator (@samp{:} on GNU and Unix
24214 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24215 to the @env{PATH} environment variable.
24217 @anchor{show auto-load scripts-directory}
24218 @kindex show auto-load scripts-directory
24219 @item show auto-load scripts-directory
24220 Show @value{GDBN} auto-loaded scripts location.
24222 @anchor{add-auto-load-scripts-directory}
24223 @kindex add-auto-load-scripts-directory
24224 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24225 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24226 Multiple entries may be delimited by the host platform path separator in use.
24229 @value{GDBN} does not track which files it has already auto-loaded this way.
24230 @value{GDBN} will load the associated script every time the corresponding
24231 @var{objfile} is opened.
24232 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24233 is evaluated more than once.
24235 @node dotdebug_gdb_scripts section
24236 @subsection The @code{.debug_gdb_scripts} section
24237 @cindex @code{.debug_gdb_scripts} section
24239 For systems using file formats like ELF and COFF,
24240 when @value{GDBN} loads a new object file
24241 it will look for a special section named @code{.debug_gdb_scripts}.
24242 If this section exists, its contents is a list of null-terminated entries
24243 specifying scripts to load. Each entry begins with a non-null prefix byte that
24244 specifies the kind of entry, typically the extension language and whether the
24245 script is in a file or inlined in @code{.debug_gdb_scripts}.
24247 The following entries are supported:
24250 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24251 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24252 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24253 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24256 @subsubsection Script File Entries
24258 If the entry specifies a file, @value{GDBN} will look for the file first
24259 in the current directory and then along the source search path
24260 (@pxref{Source Path, ,Specifying Source Directories}),
24261 except that @file{$cdir} is not searched, since the compilation
24262 directory is not relevant to scripts.
24264 File entries can be placed in section @code{.debug_gdb_scripts} with,
24265 for example, this GCC macro for Python scripts.
24268 /* Note: The "MS" section flags are to remove duplicates. */
24269 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24271 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24272 .byte 1 /* Python */\n\
24273 .asciz \"" script_name "\"\n\
24279 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24280 Then one can reference the macro in a header or source file like this:
24283 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24286 The script name may include directories if desired.
24288 Note that loading of this script file also requires accordingly configured
24289 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24291 If the macro invocation is put in a header, any application or library
24292 using this header will get a reference to the specified script,
24293 and with the use of @code{"MS"} attributes on the section, the linker
24294 will remove duplicates.
24296 @subsubsection Script Text Entries
24298 Script text entries allow to put the executable script in the entry
24299 itself instead of loading it from a file.
24300 The first line of the entry, everything after the prefix byte and up to
24301 the first newline (@code{0xa}) character, is the script name, and must not
24302 contain any kind of space character, e.g., spaces or tabs.
24303 The rest of the entry, up to the trailing null byte, is the script to
24304 execute in the specified language. The name needs to be unique among
24305 all script names, as @value{GDBN} executes each script only once based
24308 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24312 #include "symcat.h"
24313 #include "gdb/section-scripts.h"
24315 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24316 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24317 ".ascii \"gdb.inlined-script\\n\"\n"
24318 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24319 ".ascii \" def __init__ (self):\\n\"\n"
24320 ".ascii \" super (test_cmd, self).__init__ ("
24321 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24322 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24323 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24324 ".ascii \"test_cmd ()\\n\"\n"
24330 Loading of inlined scripts requires a properly configured
24331 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24332 The path to specify in @code{auto-load safe-path} is the path of the file
24333 containing the @code{.debug_gdb_scripts} section.
24335 @node Which flavor to choose?
24336 @subsection Which flavor to choose?
24338 Given the multiple ways of auto-loading extensions, it might not always
24339 be clear which one to choose. This section provides some guidance.
24342 Benefits of the @file{-gdb.@var{ext}} way:
24346 Can be used with file formats that don't support multiple sections.
24349 Ease of finding scripts for public libraries.
24351 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24352 in the source search path.
24353 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24354 isn't a source directory in which to find the script.
24357 Doesn't require source code additions.
24361 Benefits of the @code{.debug_gdb_scripts} way:
24365 Works with static linking.
24367 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24368 trigger their loading. When an application is statically linked the only
24369 objfile available is the executable, and it is cumbersome to attach all the
24370 scripts from all the input libraries to the executable's
24371 @file{-gdb.@var{ext}} script.
24374 Works with classes that are entirely inlined.
24376 Some classes can be entirely inlined, and thus there may not be an associated
24377 shared library to attach a @file{-gdb.@var{ext}} script to.
24380 Scripts needn't be copied out of the source tree.
24382 In some circumstances, apps can be built out of large collections of internal
24383 libraries, and the build infrastructure necessary to install the
24384 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24385 cumbersome. It may be easier to specify the scripts in the
24386 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24387 top of the source tree to the source search path.
24390 @node Multiple Extension Languages
24391 @section Multiple Extension Languages
24393 The Guile and Python extension languages do not share any state,
24394 and generally do not interfere with each other.
24395 There are some things to be aware of, however.
24397 @subsection Python comes first
24399 Python was @value{GDBN}'s first extension language, and to avoid breaking
24400 existing behaviour Python comes first. This is generally solved by the
24401 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24402 extension languages, and when it makes a call to an extension language,
24403 (say to pretty-print a value), it tries each in turn until an extension
24404 language indicates it has performed the request (e.g., has returned the
24405 pretty-printed form of a value).
24406 This extends to errors while performing such requests: If an error happens
24407 while, for example, trying to pretty-print an object then the error is
24408 reported and any following extension languages are not tried.
24411 @section Creating new spellings of existing commands
24412 @cindex aliases for commands
24414 It is often useful to define alternate spellings of existing commands.
24415 For example, if a new @value{GDBN} command defined in Python has
24416 a long name to type, it is handy to have an abbreviated version of it
24417 that involves less typing.
24419 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24420 of the @samp{step} command even though it is otherwise an ambiguous
24421 abbreviation of other commands like @samp{set} and @samp{show}.
24423 Aliases are also used to provide shortened or more common versions
24424 of multi-word commands. For example, @value{GDBN} provides the
24425 @samp{tty} alias of the @samp{set inferior-tty} command.
24427 You can define a new alias with the @samp{alias} command.
24432 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24436 @var{ALIAS} specifies the name of the new alias.
24437 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24440 @var{COMMAND} specifies the name of an existing command
24441 that is being aliased.
24443 The @samp{-a} option specifies that the new alias is an abbreviation
24444 of the command. Abbreviations are not shown in command
24445 lists displayed by the @samp{help} command.
24447 The @samp{--} option specifies the end of options,
24448 and is useful when @var{ALIAS} begins with a dash.
24450 Here is a simple example showing how to make an abbreviation
24451 of a command so that there is less to type.
24452 Suppose you were tired of typing @samp{disas}, the current
24453 shortest unambiguous abbreviation of the @samp{disassemble} command
24454 and you wanted an even shorter version named @samp{di}.
24455 The following will accomplish this.
24458 (gdb) alias -a di = disas
24461 Note that aliases are different from user-defined commands.
24462 With a user-defined command, you also need to write documentation
24463 for it with the @samp{document} command.
24464 An alias automatically picks up the documentation of the existing command.
24466 Here is an example where we make @samp{elms} an abbreviation of
24467 @samp{elements} in the @samp{set print elements} command.
24468 This is to show that you can make an abbreviation of any part
24472 (gdb) alias -a set print elms = set print elements
24473 (gdb) alias -a show print elms = show print elements
24474 (gdb) set p elms 20
24476 Limit on string chars or array elements to print is 200.
24479 Note that if you are defining an alias of a @samp{set} command,
24480 and you want to have an alias for the corresponding @samp{show}
24481 command, then you need to define the latter separately.
24483 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24484 @var{ALIAS}, just as they are normally.
24487 (gdb) alias -a set pr elms = set p ele
24490 Finally, here is an example showing the creation of a one word
24491 alias for a more complex command.
24492 This creates alias @samp{spe} of the command @samp{set print elements}.
24495 (gdb) alias spe = set print elements
24500 @chapter Command Interpreters
24501 @cindex command interpreters
24503 @value{GDBN} supports multiple command interpreters, and some command
24504 infrastructure to allow users or user interface writers to switch
24505 between interpreters or run commands in other interpreters.
24507 @value{GDBN} currently supports two command interpreters, the console
24508 interpreter (sometimes called the command-line interpreter or @sc{cli})
24509 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24510 describes both of these interfaces in great detail.
24512 By default, @value{GDBN} will start with the console interpreter.
24513 However, the user may choose to start @value{GDBN} with another
24514 interpreter by specifying the @option{-i} or @option{--interpreter}
24515 startup options. Defined interpreters include:
24519 @cindex console interpreter
24520 The traditional console or command-line interpreter. This is the most often
24521 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24522 @value{GDBN} will use this interpreter.
24525 @cindex mi interpreter
24526 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24527 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24528 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24532 @cindex mi2 interpreter
24533 The current @sc{gdb/mi} interface.
24536 @cindex mi1 interpreter
24537 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24541 @cindex invoke another interpreter
24542 The interpreter being used by @value{GDBN} may not be dynamically
24543 switched at runtime. Although possible, this could lead to a very
24544 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24545 enters the command "interpreter-set console" in a console view,
24546 @value{GDBN} would switch to using the console interpreter, rendering
24547 the IDE inoperable!
24549 @kindex interpreter-exec
24550 Although you may only choose a single interpreter at startup, you may execute
24551 commands in any interpreter from the current interpreter using the appropriate
24552 command. If you are running the console interpreter, simply use the
24553 @code{interpreter-exec} command:
24556 interpreter-exec mi "-data-list-register-names"
24559 @sc{gdb/mi} has a similar command, although it is only available in versions of
24560 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24563 @chapter @value{GDBN} Text User Interface
24565 @cindex Text User Interface
24568 * TUI Overview:: TUI overview
24569 * TUI Keys:: TUI key bindings
24570 * TUI Single Key Mode:: TUI single key mode
24571 * TUI Commands:: TUI-specific commands
24572 * TUI Configuration:: TUI configuration variables
24575 The @value{GDBN} Text User Interface (TUI) is a terminal
24576 interface which uses the @code{curses} library to show the source
24577 file, the assembly output, the program registers and @value{GDBN}
24578 commands in separate text windows. The TUI mode is supported only
24579 on platforms where a suitable version of the @code{curses} library
24582 The TUI mode is enabled by default when you invoke @value{GDBN} as
24583 @samp{@value{GDBP} -tui}.
24584 You can also switch in and out of TUI mode while @value{GDBN} runs by
24585 using various TUI commands and key bindings, such as @command{tui
24586 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
24587 @ref{TUI Keys, ,TUI Key Bindings}.
24590 @section TUI Overview
24592 In TUI mode, @value{GDBN} can display several text windows:
24596 This window is the @value{GDBN} command window with the @value{GDBN}
24597 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24598 managed using readline.
24601 The source window shows the source file of the program. The current
24602 line and active breakpoints are displayed in this window.
24605 The assembly window shows the disassembly output of the program.
24608 This window shows the processor registers. Registers are highlighted
24609 when their values change.
24612 The source and assembly windows show the current program position
24613 by highlighting the current line and marking it with a @samp{>} marker.
24614 Breakpoints are indicated with two markers. The first marker
24615 indicates the breakpoint type:
24619 Breakpoint which was hit at least once.
24622 Breakpoint which was never hit.
24625 Hardware breakpoint which was hit at least once.
24628 Hardware breakpoint which was never hit.
24631 The second marker indicates whether the breakpoint is enabled or not:
24635 Breakpoint is enabled.
24638 Breakpoint is disabled.
24641 The source, assembly and register windows are updated when the current
24642 thread changes, when the frame changes, or when the program counter
24645 These windows are not all visible at the same time. The command
24646 window is always visible. The others can be arranged in several
24657 source and assembly,
24660 source and registers, or
24663 assembly and registers.
24666 A status line above the command window shows the following information:
24670 Indicates the current @value{GDBN} target.
24671 (@pxref{Targets, ,Specifying a Debugging Target}).
24674 Gives the current process or thread number.
24675 When no process is being debugged, this field is set to @code{No process}.
24678 Gives the current function name for the selected frame.
24679 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24680 When there is no symbol corresponding to the current program counter,
24681 the string @code{??} is displayed.
24684 Indicates the current line number for the selected frame.
24685 When the current line number is not known, the string @code{??} is displayed.
24688 Indicates the current program counter address.
24692 @section TUI Key Bindings
24693 @cindex TUI key bindings
24695 The TUI installs several key bindings in the readline keymaps
24696 @ifset SYSTEM_READLINE
24697 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24699 @ifclear SYSTEM_READLINE
24700 (@pxref{Command Line Editing}).
24702 The following key bindings are installed for both TUI mode and the
24703 @value{GDBN} standard mode.
24712 Enter or leave the TUI mode. When leaving the TUI mode,
24713 the curses window management stops and @value{GDBN} operates using
24714 its standard mode, writing on the terminal directly. When reentering
24715 the TUI mode, control is given back to the curses windows.
24716 The screen is then refreshed.
24720 Use a TUI layout with only one window. The layout will
24721 either be @samp{source} or @samp{assembly}. When the TUI mode
24722 is not active, it will switch to the TUI mode.
24724 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24728 Use a TUI layout with at least two windows. When the current
24729 layout already has two windows, the next layout with two windows is used.
24730 When a new layout is chosen, one window will always be common to the
24731 previous layout and the new one.
24733 Think of it as the Emacs @kbd{C-x 2} binding.
24737 Change the active window. The TUI associates several key bindings
24738 (like scrolling and arrow keys) with the active window. This command
24739 gives the focus to the next TUI window.
24741 Think of it as the Emacs @kbd{C-x o} binding.
24745 Switch in and out of the TUI SingleKey mode that binds single
24746 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24749 The following key bindings only work in the TUI mode:
24754 Scroll the active window one page up.
24758 Scroll the active window one page down.
24762 Scroll the active window one line up.
24766 Scroll the active window one line down.
24770 Scroll the active window one column left.
24774 Scroll the active window one column right.
24778 Refresh the screen.
24781 Because the arrow keys scroll the active window in the TUI mode, they
24782 are not available for their normal use by readline unless the command
24783 window has the focus. When another window is active, you must use
24784 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24785 and @kbd{C-f} to control the command window.
24787 @node TUI Single Key Mode
24788 @section TUI Single Key Mode
24789 @cindex TUI single key mode
24791 The TUI also provides a @dfn{SingleKey} mode, which binds several
24792 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24793 switch into this mode, where the following key bindings are used:
24796 @kindex c @r{(SingleKey TUI key)}
24800 @kindex d @r{(SingleKey TUI key)}
24804 @kindex f @r{(SingleKey TUI key)}
24808 @kindex n @r{(SingleKey TUI key)}
24812 @kindex q @r{(SingleKey TUI key)}
24814 exit the SingleKey mode.
24816 @kindex r @r{(SingleKey TUI key)}
24820 @kindex s @r{(SingleKey TUI key)}
24824 @kindex u @r{(SingleKey TUI key)}
24828 @kindex v @r{(SingleKey TUI key)}
24832 @kindex w @r{(SingleKey TUI key)}
24837 Other keys temporarily switch to the @value{GDBN} command prompt.
24838 The key that was pressed is inserted in the editing buffer so that
24839 it is possible to type most @value{GDBN} commands without interaction
24840 with the TUI SingleKey mode. Once the command is entered the TUI
24841 SingleKey mode is restored. The only way to permanently leave
24842 this mode is by typing @kbd{q} or @kbd{C-x s}.
24846 @section TUI-specific Commands
24847 @cindex TUI commands
24849 The TUI has specific commands to control the text windows.
24850 These commands are always available, even when @value{GDBN} is not in
24851 the TUI mode. When @value{GDBN} is in the standard mode, most
24852 of these commands will automatically switch to the TUI mode.
24854 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24855 terminal, or @value{GDBN} has been started with the machine interface
24856 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24857 these commands will fail with an error, because it would not be
24858 possible or desirable to enable curses window management.
24863 Activate TUI mode. The last active TUI window layout will be used if
24864 TUI mode has prevsiouly been used in the current debugging session,
24865 otherwise a default layout is used.
24868 @kindex tui disable
24869 Disable TUI mode, returning to the console interpreter.
24873 List and give the size of all displayed windows.
24875 @item layout @var{name}
24877 Changes which TUI windows are displayed. In each layout the command
24878 window is always displayed, the @var{name} parameter controls which
24879 additional windows are displayed, and can be any of the following:
24883 Display the next layout.
24886 Display the previous layout.
24889 Display the source and command windows.
24892 Display the assembly and command windows.
24895 Display the source, assembly, and command windows.
24898 When in @code{src} layout display the register, source, and command
24899 windows. When in @code{asm} or @code{split} layout display the
24900 register, assembler, and command windows.
24903 @item focus @var{name}
24905 Changes which TUI window is currently active for scrolling. The
24906 @var{name} parameter can be any of the following:
24910 Make the next window active for scrolling.
24913 Make the previous window active for scrolling.
24916 Make the source window active for scrolling.
24919 Make the assembly window active for scrolling.
24922 Make the register window active for scrolling.
24925 Make the command window active for scrolling.
24930 Refresh the screen. This is similar to typing @kbd{C-L}.
24932 @item tui reg @var{group}
24934 Changes the register group displayed in the tui register window to
24935 @var{group}. If the register window is not currently displayed this
24936 command will cause the register window to be displayed. The list of
24937 register groups, as well as their order is target specific. The
24938 following groups are available on most targets:
24941 Repeatedly selecting this group will cause the display to cycle
24942 through all of the available register groups.
24945 Repeatedly selecting this group will cause the display to cycle
24946 through all of the available register groups in the reverse order to
24950 Display the general registers.
24952 Display the floating point registers.
24954 Display the system registers.
24956 Display the vector registers.
24958 Display all registers.
24963 Update the source window and the current execution point.
24965 @item winheight @var{name} +@var{count}
24966 @itemx winheight @var{name} -@var{count}
24968 Change the height of the window @var{name} by @var{count}
24969 lines. Positive counts increase the height, while negative counts
24970 decrease it. The @var{name} parameter can be one of @code{src} (the
24971 source window), @code{cmd} (the command window), @code{asm} (the
24972 disassembly window), or @code{regs} (the register display window).
24974 @item tabset @var{nchars}
24976 Set the width of tab stops to be @var{nchars} characters. This
24977 setting affects the display of TAB characters in the source and
24981 @node TUI Configuration
24982 @section TUI Configuration Variables
24983 @cindex TUI configuration variables
24985 Several configuration variables control the appearance of TUI windows.
24988 @item set tui border-kind @var{kind}
24989 @kindex set tui border-kind
24990 Select the border appearance for the source, assembly and register windows.
24991 The possible values are the following:
24994 Use a space character to draw the border.
24997 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25000 Use the Alternate Character Set to draw the border. The border is
25001 drawn using character line graphics if the terminal supports them.
25004 @item set tui border-mode @var{mode}
25005 @kindex set tui border-mode
25006 @itemx set tui active-border-mode @var{mode}
25007 @kindex set tui active-border-mode
25008 Select the display attributes for the borders of the inactive windows
25009 or the active window. The @var{mode} can be one of the following:
25012 Use normal attributes to display the border.
25018 Use reverse video mode.
25021 Use half bright mode.
25023 @item half-standout
25024 Use half bright and standout mode.
25027 Use extra bright or bold mode.
25029 @item bold-standout
25030 Use extra bright or bold and standout mode.
25035 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25038 @cindex @sc{gnu} Emacs
25039 A special interface allows you to use @sc{gnu} Emacs to view (and
25040 edit) the source files for the program you are debugging with
25043 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25044 executable file you want to debug as an argument. This command starts
25045 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25046 created Emacs buffer.
25047 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25049 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25054 All ``terminal'' input and output goes through an Emacs buffer, called
25057 This applies both to @value{GDBN} commands and their output, and to the input
25058 and output done by the program you are debugging.
25060 This is useful because it means that you can copy the text of previous
25061 commands and input them again; you can even use parts of the output
25064 All the facilities of Emacs' Shell mode are available for interacting
25065 with your program. In particular, you can send signals the usual
25066 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25070 @value{GDBN} displays source code through Emacs.
25072 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25073 source file for that frame and puts an arrow (@samp{=>}) at the
25074 left margin of the current line. Emacs uses a separate buffer for
25075 source display, and splits the screen to show both your @value{GDBN} session
25078 Explicit @value{GDBN} @code{list} or search commands still produce output as
25079 usual, but you probably have no reason to use them from Emacs.
25082 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25083 a graphical mode, enabled by default, which provides further buffers
25084 that can control the execution and describe the state of your program.
25085 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25087 If you specify an absolute file name when prompted for the @kbd{M-x
25088 gdb} argument, then Emacs sets your current working directory to where
25089 your program resides. If you only specify the file name, then Emacs
25090 sets your current working directory to the directory associated
25091 with the previous buffer. In this case, @value{GDBN} may find your
25092 program by searching your environment's @code{PATH} variable, but on
25093 some operating systems it might not find the source. So, although the
25094 @value{GDBN} input and output session proceeds normally, the auxiliary
25095 buffer does not display the current source and line of execution.
25097 The initial working directory of @value{GDBN} is printed on the top
25098 line of the GUD buffer and this serves as a default for the commands
25099 that specify files for @value{GDBN} to operate on. @xref{Files,
25100 ,Commands to Specify Files}.
25102 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25103 need to call @value{GDBN} by a different name (for example, if you
25104 keep several configurations around, with different names) you can
25105 customize the Emacs variable @code{gud-gdb-command-name} to run the
25108 In the GUD buffer, you can use these special Emacs commands in
25109 addition to the standard Shell mode commands:
25113 Describe the features of Emacs' GUD Mode.
25116 Execute to another source line, like the @value{GDBN} @code{step} command; also
25117 update the display window to show the current file and location.
25120 Execute to next source line in this function, skipping all function
25121 calls, like the @value{GDBN} @code{next} command. Then update the display window
25122 to show the current file and location.
25125 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25126 display window accordingly.
25129 Execute until exit from the selected stack frame, like the @value{GDBN}
25130 @code{finish} command.
25133 Continue execution of your program, like the @value{GDBN} @code{continue}
25137 Go up the number of frames indicated by the numeric argument
25138 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25139 like the @value{GDBN} @code{up} command.
25142 Go down the number of frames indicated by the numeric argument, like the
25143 @value{GDBN} @code{down} command.
25146 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25147 tells @value{GDBN} to set a breakpoint on the source line point is on.
25149 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25150 separate frame which shows a backtrace when the GUD buffer is current.
25151 Move point to any frame in the stack and type @key{RET} to make it
25152 become the current frame and display the associated source in the
25153 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25154 selected frame become the current one. In graphical mode, the
25155 speedbar displays watch expressions.
25157 If you accidentally delete the source-display buffer, an easy way to get
25158 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25159 request a frame display; when you run under Emacs, this recreates
25160 the source buffer if necessary to show you the context of the current
25163 The source files displayed in Emacs are in ordinary Emacs buffers
25164 which are visiting the source files in the usual way. You can edit
25165 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25166 communicates with Emacs in terms of line numbers. If you add or
25167 delete lines from the text, the line numbers that @value{GDBN} knows cease
25168 to correspond properly with the code.
25170 A more detailed description of Emacs' interaction with @value{GDBN} is
25171 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25175 @chapter The @sc{gdb/mi} Interface
25177 @unnumberedsec Function and Purpose
25179 @cindex @sc{gdb/mi}, its purpose
25180 @sc{gdb/mi} is a line based machine oriented text interface to
25181 @value{GDBN} and is activated by specifying using the
25182 @option{--interpreter} command line option (@pxref{Mode Options}). It
25183 is specifically intended to support the development of systems which
25184 use the debugger as just one small component of a larger system.
25186 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25187 in the form of a reference manual.
25189 Note that @sc{gdb/mi} is still under construction, so some of the
25190 features described below are incomplete and subject to change
25191 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25193 @unnumberedsec Notation and Terminology
25195 @cindex notational conventions, for @sc{gdb/mi}
25196 This chapter uses the following notation:
25200 @code{|} separates two alternatives.
25203 @code{[ @var{something} ]} indicates that @var{something} is optional:
25204 it may or may not be given.
25207 @code{( @var{group} )*} means that @var{group} inside the parentheses
25208 may repeat zero or more times.
25211 @code{( @var{group} )+} means that @var{group} inside the parentheses
25212 may repeat one or more times.
25215 @code{"@var{string}"} means a literal @var{string}.
25219 @heading Dependencies
25223 * GDB/MI General Design::
25224 * GDB/MI Command Syntax::
25225 * GDB/MI Compatibility with CLI::
25226 * GDB/MI Development and Front Ends::
25227 * GDB/MI Output Records::
25228 * GDB/MI Simple Examples::
25229 * GDB/MI Command Description Format::
25230 * GDB/MI Breakpoint Commands::
25231 * GDB/MI Catchpoint Commands::
25232 * GDB/MI Program Context::
25233 * GDB/MI Thread Commands::
25234 * GDB/MI Ada Tasking Commands::
25235 * GDB/MI Program Execution::
25236 * GDB/MI Stack Manipulation::
25237 * GDB/MI Variable Objects::
25238 * GDB/MI Data Manipulation::
25239 * GDB/MI Tracepoint Commands::
25240 * GDB/MI Symbol Query::
25241 * GDB/MI File Commands::
25243 * GDB/MI Kod Commands::
25244 * GDB/MI Memory Overlay Commands::
25245 * GDB/MI Signal Handling Commands::
25247 * GDB/MI Target Manipulation::
25248 * GDB/MI File Transfer Commands::
25249 * GDB/MI Ada Exceptions Commands::
25250 * GDB/MI Support Commands::
25251 * GDB/MI Miscellaneous Commands::
25254 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25255 @node GDB/MI General Design
25256 @section @sc{gdb/mi} General Design
25257 @cindex GDB/MI General Design
25259 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25260 parts---commands sent to @value{GDBN}, responses to those commands
25261 and notifications. Each command results in exactly one response,
25262 indicating either successful completion of the command, or an error.
25263 For the commands that do not resume the target, the response contains the
25264 requested information. For the commands that resume the target, the
25265 response only indicates whether the target was successfully resumed.
25266 Notifications is the mechanism for reporting changes in the state of the
25267 target, or in @value{GDBN} state, that cannot conveniently be associated with
25268 a command and reported as part of that command response.
25270 The important examples of notifications are:
25274 Exec notifications. These are used to report changes in
25275 target state---when a target is resumed, or stopped. It would not
25276 be feasible to include this information in response of resuming
25277 commands, because one resume commands can result in multiple events in
25278 different threads. Also, quite some time may pass before any event
25279 happens in the target, while a frontend needs to know whether the resuming
25280 command itself was successfully executed.
25283 Console output, and status notifications. Console output
25284 notifications are used to report output of CLI commands, as well as
25285 diagnostics for other commands. Status notifications are used to
25286 report the progress of a long-running operation. Naturally, including
25287 this information in command response would mean no output is produced
25288 until the command is finished, which is undesirable.
25291 General notifications. Commands may have various side effects on
25292 the @value{GDBN} or target state beyond their official purpose. For example,
25293 a command may change the selected thread. Although such changes can
25294 be included in command response, using notification allows for more
25295 orthogonal frontend design.
25299 There's no guarantee that whenever an MI command reports an error,
25300 @value{GDBN} or the target are in any specific state, and especially,
25301 the state is not reverted to the state before the MI command was
25302 processed. Therefore, whenever an MI command results in an error,
25303 we recommend that the frontend refreshes all the information shown in
25304 the user interface.
25308 * Context management::
25309 * Asynchronous and non-stop modes::
25313 @node Context management
25314 @subsection Context management
25316 @subsubsection Threads and Frames
25318 In most cases when @value{GDBN} accesses the target, this access is
25319 done in context of a specific thread and frame (@pxref{Frames}).
25320 Often, even when accessing global data, the target requires that a thread
25321 be specified. The CLI interface maintains the selected thread and frame,
25322 and supplies them to target on each command. This is convenient,
25323 because a command line user would not want to specify that information
25324 explicitly on each command, and because user interacts with
25325 @value{GDBN} via a single terminal, so no confusion is possible as
25326 to what thread and frame are the current ones.
25328 In the case of MI, the concept of selected thread and frame is less
25329 useful. First, a frontend can easily remember this information
25330 itself. Second, a graphical frontend can have more than one window,
25331 each one used for debugging a different thread, and the frontend might
25332 want to access additional threads for internal purposes. This
25333 increases the risk that by relying on implicitly selected thread, the
25334 frontend may be operating on a wrong one. Therefore, each MI command
25335 should explicitly specify which thread and frame to operate on. To
25336 make it possible, each MI command accepts the @samp{--thread} and
25337 @samp{--frame} options, the value to each is @value{GDBN} identifier
25338 for thread and frame to operate on.
25340 Usually, each top-level window in a frontend allows the user to select
25341 a thread and a frame, and remembers the user selection for further
25342 operations. However, in some cases @value{GDBN} may suggest that the
25343 current thread be changed. For example, when stopping on a breakpoint
25344 it is reasonable to switch to the thread where breakpoint is hit. For
25345 another example, if the user issues the CLI @samp{thread} command via
25346 the frontend, it is desirable to change the frontend's selected thread to the
25347 one specified by user. @value{GDBN} communicates the suggestion to
25348 change current thread using the @samp{=thread-selected} notification.
25349 No such notification is available for the selected frame at the moment.
25351 Note that historically, MI shares the selected thread with CLI, so
25352 frontends used the @code{-thread-select} to execute commands in the
25353 right context. However, getting this to work right is cumbersome. The
25354 simplest way is for frontend to emit @code{-thread-select} command
25355 before every command. This doubles the number of commands that need
25356 to be sent. The alternative approach is to suppress @code{-thread-select}
25357 if the selected thread in @value{GDBN} is supposed to be identical to the
25358 thread the frontend wants to operate on. However, getting this
25359 optimization right can be tricky. In particular, if the frontend
25360 sends several commands to @value{GDBN}, and one of the commands changes the
25361 selected thread, then the behaviour of subsequent commands will
25362 change. So, a frontend should either wait for response from such
25363 problematic commands, or explicitly add @code{-thread-select} for
25364 all subsequent commands. No frontend is known to do this exactly
25365 right, so it is suggested to just always pass the @samp{--thread} and
25366 @samp{--frame} options.
25368 @subsubsection Language
25370 The execution of several commands depends on which language is selected.
25371 By default, the current language (@pxref{show language}) is used.
25372 But for commands known to be language-sensitive, it is recommended
25373 to use the @samp{--language} option. This option takes one argument,
25374 which is the name of the language to use while executing the command.
25378 -data-evaluate-expression --language c "sizeof (void*)"
25383 The valid language names are the same names accepted by the
25384 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25385 @samp{local} or @samp{unknown}.
25387 @node Asynchronous and non-stop modes
25388 @subsection Asynchronous command execution and non-stop mode
25390 On some targets, @value{GDBN} is capable of processing MI commands
25391 even while the target is running. This is called @dfn{asynchronous
25392 command execution} (@pxref{Background Execution}). The frontend may
25393 specify a preferrence for asynchronous execution using the
25394 @code{-gdb-set mi-async 1} command, which should be emitted before
25395 either running the executable or attaching to the target. After the
25396 frontend has started the executable or attached to the target, it can
25397 find if asynchronous execution is enabled using the
25398 @code{-list-target-features} command.
25401 @item -gdb-set mi-async on
25402 @item -gdb-set mi-async off
25403 Set whether MI is in asynchronous mode.
25405 When @code{off}, which is the default, MI execution commands (e.g.,
25406 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25407 for the program to stop before processing further commands.
25409 When @code{on}, MI execution commands are background execution
25410 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25411 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25412 MI commands even while the target is running.
25414 @item -gdb-show mi-async
25415 Show whether MI asynchronous mode is enabled.
25418 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25419 @code{target-async} instead of @code{mi-async}, and it had the effect
25420 of both putting MI in asynchronous mode and making CLI background
25421 commands possible. CLI background commands are now always possible
25422 ``out of the box'' if the target supports them. The old spelling is
25423 kept as a deprecated alias for backwards compatibility.
25425 Even if @value{GDBN} can accept a command while target is running,
25426 many commands that access the target do not work when the target is
25427 running. Therefore, asynchronous command execution is most useful
25428 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25429 it is possible to examine the state of one thread, while other threads
25432 When a given thread is running, MI commands that try to access the
25433 target in the context of that thread may not work, or may work only on
25434 some targets. In particular, commands that try to operate on thread's
25435 stack will not work, on any target. Commands that read memory, or
25436 modify breakpoints, may work or not work, depending on the target. Note
25437 that even commands that operate on global state, such as @code{print},
25438 @code{set}, and breakpoint commands, still access the target in the
25439 context of a specific thread, so frontend should try to find a
25440 stopped thread and perform the operation on that thread (using the
25441 @samp{--thread} option).
25443 Which commands will work in the context of a running thread is
25444 highly target dependent. However, the two commands
25445 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25446 to find the state of a thread, will always work.
25448 @node Thread groups
25449 @subsection Thread groups
25450 @value{GDBN} may be used to debug several processes at the same time.
25451 On some platfroms, @value{GDBN} may support debugging of several
25452 hardware systems, each one having several cores with several different
25453 processes running on each core. This section describes the MI
25454 mechanism to support such debugging scenarios.
25456 The key observation is that regardless of the structure of the
25457 target, MI can have a global list of threads, because most commands that
25458 accept the @samp{--thread} option do not need to know what process that
25459 thread belongs to. Therefore, it is not necessary to introduce
25460 neither additional @samp{--process} option, nor an notion of the
25461 current process in the MI interface. The only strictly new feature
25462 that is required is the ability to find how the threads are grouped
25465 To allow the user to discover such grouping, and to support arbitrary
25466 hierarchy of machines/cores/processes, MI introduces the concept of a
25467 @dfn{thread group}. Thread group is a collection of threads and other
25468 thread groups. A thread group always has a string identifier, a type,
25469 and may have additional attributes specific to the type. A new
25470 command, @code{-list-thread-groups}, returns the list of top-level
25471 thread groups, which correspond to processes that @value{GDBN} is
25472 debugging at the moment. By passing an identifier of a thread group
25473 to the @code{-list-thread-groups} command, it is possible to obtain
25474 the members of specific thread group.
25476 To allow the user to easily discover processes, and other objects, he
25477 wishes to debug, a concept of @dfn{available thread group} is
25478 introduced. Available thread group is an thread group that
25479 @value{GDBN} is not debugging, but that can be attached to, using the
25480 @code{-target-attach} command. The list of available top-level thread
25481 groups can be obtained using @samp{-list-thread-groups --available}.
25482 In general, the content of a thread group may be only retrieved only
25483 after attaching to that thread group.
25485 Thread groups are related to inferiors (@pxref{Inferiors and
25486 Programs}). Each inferior corresponds to a thread group of a special
25487 type @samp{process}, and some additional operations are permitted on
25488 such thread groups.
25490 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25491 @node GDB/MI Command Syntax
25492 @section @sc{gdb/mi} Command Syntax
25495 * GDB/MI Input Syntax::
25496 * GDB/MI Output Syntax::
25499 @node GDB/MI Input Syntax
25500 @subsection @sc{gdb/mi} Input Syntax
25502 @cindex input syntax for @sc{gdb/mi}
25503 @cindex @sc{gdb/mi}, input syntax
25505 @item @var{command} @expansion{}
25506 @code{@var{cli-command} | @var{mi-command}}
25508 @item @var{cli-command} @expansion{}
25509 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25510 @var{cli-command} is any existing @value{GDBN} CLI command.
25512 @item @var{mi-command} @expansion{}
25513 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25514 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25516 @item @var{token} @expansion{}
25517 "any sequence of digits"
25519 @item @var{option} @expansion{}
25520 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25522 @item @var{parameter} @expansion{}
25523 @code{@var{non-blank-sequence} | @var{c-string}}
25525 @item @var{operation} @expansion{}
25526 @emph{any of the operations described in this chapter}
25528 @item @var{non-blank-sequence} @expansion{}
25529 @emph{anything, provided it doesn't contain special characters such as
25530 "-", @var{nl}, """ and of course " "}
25532 @item @var{c-string} @expansion{}
25533 @code{""" @var{seven-bit-iso-c-string-content} """}
25535 @item @var{nl} @expansion{}
25544 The CLI commands are still handled by the @sc{mi} interpreter; their
25545 output is described below.
25548 The @code{@var{token}}, when present, is passed back when the command
25552 Some @sc{mi} commands accept optional arguments as part of the parameter
25553 list. Each option is identified by a leading @samp{-} (dash) and may be
25554 followed by an optional argument parameter. Options occur first in the
25555 parameter list and can be delimited from normal parameters using
25556 @samp{--} (this is useful when some parameters begin with a dash).
25563 We want easy access to the existing CLI syntax (for debugging).
25566 We want it to be easy to spot a @sc{mi} operation.
25569 @node GDB/MI Output Syntax
25570 @subsection @sc{gdb/mi} Output Syntax
25572 @cindex output syntax of @sc{gdb/mi}
25573 @cindex @sc{gdb/mi}, output syntax
25574 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25575 followed, optionally, by a single result record. This result record
25576 is for the most recent command. The sequence of output records is
25577 terminated by @samp{(gdb)}.
25579 If an input command was prefixed with a @code{@var{token}} then the
25580 corresponding output for that command will also be prefixed by that same
25584 @item @var{output} @expansion{}
25585 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25587 @item @var{result-record} @expansion{}
25588 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25590 @item @var{out-of-band-record} @expansion{}
25591 @code{@var{async-record} | @var{stream-record}}
25593 @item @var{async-record} @expansion{}
25594 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25596 @item @var{exec-async-output} @expansion{}
25597 @code{[ @var{token} ] "*" @var{async-output nl}}
25599 @item @var{status-async-output} @expansion{}
25600 @code{[ @var{token} ] "+" @var{async-output nl}}
25602 @item @var{notify-async-output} @expansion{}
25603 @code{[ @var{token} ] "=" @var{async-output nl}}
25605 @item @var{async-output} @expansion{}
25606 @code{@var{async-class} ( "," @var{result} )*}
25608 @item @var{result-class} @expansion{}
25609 @code{"done" | "running" | "connected" | "error" | "exit"}
25611 @item @var{async-class} @expansion{}
25612 @code{"stopped" | @var{others}} (where @var{others} will be added
25613 depending on the needs---this is still in development).
25615 @item @var{result} @expansion{}
25616 @code{ @var{variable} "=" @var{value}}
25618 @item @var{variable} @expansion{}
25619 @code{ @var{string} }
25621 @item @var{value} @expansion{}
25622 @code{ @var{const} | @var{tuple} | @var{list} }
25624 @item @var{const} @expansion{}
25625 @code{@var{c-string}}
25627 @item @var{tuple} @expansion{}
25628 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25630 @item @var{list} @expansion{}
25631 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25632 @var{result} ( "," @var{result} )* "]" }
25634 @item @var{stream-record} @expansion{}
25635 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25637 @item @var{console-stream-output} @expansion{}
25638 @code{"~" @var{c-string nl}}
25640 @item @var{target-stream-output} @expansion{}
25641 @code{"@@" @var{c-string nl}}
25643 @item @var{log-stream-output} @expansion{}
25644 @code{"&" @var{c-string nl}}
25646 @item @var{nl} @expansion{}
25649 @item @var{token} @expansion{}
25650 @emph{any sequence of digits}.
25658 All output sequences end in a single line containing a period.
25661 The @code{@var{token}} is from the corresponding request. Note that
25662 for all async output, while the token is allowed by the grammar and
25663 may be output by future versions of @value{GDBN} for select async
25664 output messages, it is generally omitted. Frontends should treat
25665 all async output as reporting general changes in the state of the
25666 target and there should be no need to associate async output to any
25670 @cindex status output in @sc{gdb/mi}
25671 @var{status-async-output} contains on-going status information about the
25672 progress of a slow operation. It can be discarded. All status output is
25673 prefixed by @samp{+}.
25676 @cindex async output in @sc{gdb/mi}
25677 @var{exec-async-output} contains asynchronous state change on the target
25678 (stopped, started, disappeared). All async output is prefixed by
25682 @cindex notify output in @sc{gdb/mi}
25683 @var{notify-async-output} contains supplementary information that the
25684 client should handle (e.g., a new breakpoint information). All notify
25685 output is prefixed by @samp{=}.
25688 @cindex console output in @sc{gdb/mi}
25689 @var{console-stream-output} is output that should be displayed as is in the
25690 console. It is the textual response to a CLI command. All the console
25691 output is prefixed by @samp{~}.
25694 @cindex target output in @sc{gdb/mi}
25695 @var{target-stream-output} is the output produced by the target program.
25696 All the target output is prefixed by @samp{@@}.
25699 @cindex log output in @sc{gdb/mi}
25700 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25701 instance messages that should be displayed as part of an error log. All
25702 the log output is prefixed by @samp{&}.
25705 @cindex list output in @sc{gdb/mi}
25706 New @sc{gdb/mi} commands should only output @var{lists} containing
25712 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25713 details about the various output records.
25715 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25716 @node GDB/MI Compatibility with CLI
25717 @section @sc{gdb/mi} Compatibility with CLI
25719 @cindex compatibility, @sc{gdb/mi} and CLI
25720 @cindex @sc{gdb/mi}, compatibility with CLI
25722 For the developers convenience CLI commands can be entered directly,
25723 but there may be some unexpected behaviour. For example, commands
25724 that query the user will behave as if the user replied yes, breakpoint
25725 command lists are not executed and some CLI commands, such as
25726 @code{if}, @code{when} and @code{define}, prompt for further input with
25727 @samp{>}, which is not valid MI output.
25729 This feature may be removed at some stage in the future and it is
25730 recommended that front ends use the @code{-interpreter-exec} command
25731 (@pxref{-interpreter-exec}).
25733 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25734 @node GDB/MI Development and Front Ends
25735 @section @sc{gdb/mi} Development and Front Ends
25736 @cindex @sc{gdb/mi} development
25738 The application which takes the MI output and presents the state of the
25739 program being debugged to the user is called a @dfn{front end}.
25741 Although @sc{gdb/mi} is still incomplete, it is currently being used
25742 by a variety of front ends to @value{GDBN}. This makes it difficult
25743 to introduce new functionality without breaking existing usage. This
25744 section tries to minimize the problems by describing how the protocol
25747 Some changes in MI need not break a carefully designed front end, and
25748 for these the MI version will remain unchanged. The following is a
25749 list of changes that may occur within one level, so front ends should
25750 parse MI output in a way that can handle them:
25754 New MI commands may be added.
25757 New fields may be added to the output of any MI command.
25760 The range of values for fields with specified values, e.g.,
25761 @code{in_scope} (@pxref{-var-update}) may be extended.
25763 @c The format of field's content e.g type prefix, may change so parse it
25764 @c at your own risk. Yes, in general?
25766 @c The order of fields may change? Shouldn't really matter but it might
25767 @c resolve inconsistencies.
25770 If the changes are likely to break front ends, the MI version level
25771 will be increased by one. This will allow the front end to parse the
25772 output according to the MI version. Apart from mi0, new versions of
25773 @value{GDBN} will not support old versions of MI and it will be the
25774 responsibility of the front end to work with the new one.
25776 @c Starting with mi3, add a new command -mi-version that prints the MI
25779 The best way to avoid unexpected changes in MI that might break your front
25780 end is to make your project known to @value{GDBN} developers and
25781 follow development on @email{gdb@@sourceware.org} and
25782 @email{gdb-patches@@sourceware.org}.
25783 @cindex mailing lists
25785 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25786 @node GDB/MI Output Records
25787 @section @sc{gdb/mi} Output Records
25790 * GDB/MI Result Records::
25791 * GDB/MI Stream Records::
25792 * GDB/MI Async Records::
25793 * GDB/MI Breakpoint Information::
25794 * GDB/MI Frame Information::
25795 * GDB/MI Thread Information::
25796 * GDB/MI Ada Exception Information::
25799 @node GDB/MI Result Records
25800 @subsection @sc{gdb/mi} Result Records
25802 @cindex result records in @sc{gdb/mi}
25803 @cindex @sc{gdb/mi}, result records
25804 In addition to a number of out-of-band notifications, the response to a
25805 @sc{gdb/mi} command includes one of the following result indications:
25809 @item "^done" [ "," @var{results} ]
25810 The synchronous operation was successful, @code{@var{results}} are the return
25815 This result record is equivalent to @samp{^done}. Historically, it
25816 was output instead of @samp{^done} if the command has resumed the
25817 target. This behaviour is maintained for backward compatibility, but
25818 all frontends should treat @samp{^done} and @samp{^running}
25819 identically and rely on the @samp{*running} output record to determine
25820 which threads are resumed.
25824 @value{GDBN} has connected to a remote target.
25826 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25828 The operation failed. The @code{msg=@var{c-string}} variable contains
25829 the corresponding error message.
25831 If present, the @code{code=@var{c-string}} variable provides an error
25832 code on which consumers can rely on to detect the corresponding
25833 error condition. At present, only one error code is defined:
25836 @item "undefined-command"
25837 Indicates that the command causing the error does not exist.
25842 @value{GDBN} has terminated.
25846 @node GDB/MI Stream Records
25847 @subsection @sc{gdb/mi} Stream Records
25849 @cindex @sc{gdb/mi}, stream records
25850 @cindex stream records in @sc{gdb/mi}
25851 @value{GDBN} internally maintains a number of output streams: the console, the
25852 target, and the log. The output intended for each of these streams is
25853 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25855 Each stream record begins with a unique @dfn{prefix character} which
25856 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25857 Syntax}). In addition to the prefix, each stream record contains a
25858 @code{@var{string-output}}. This is either raw text (with an implicit new
25859 line) or a quoted C string (which does not contain an implicit newline).
25862 @item "~" @var{string-output}
25863 The console output stream contains text that should be displayed in the
25864 CLI console window. It contains the textual responses to CLI commands.
25866 @item "@@" @var{string-output}
25867 The target output stream contains any textual output from the running
25868 target. This is only present when GDB's event loop is truly
25869 asynchronous, which is currently only the case for remote targets.
25871 @item "&" @var{string-output}
25872 The log stream contains debugging messages being produced by @value{GDBN}'s
25876 @node GDB/MI Async Records
25877 @subsection @sc{gdb/mi} Async Records
25879 @cindex async records in @sc{gdb/mi}
25880 @cindex @sc{gdb/mi}, async records
25881 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25882 additional changes that have occurred. Those changes can either be a
25883 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25884 target activity (e.g., target stopped).
25886 The following is the list of possible async records:
25890 @item *running,thread-id="@var{thread}"
25891 The target is now running. The @var{thread} field tells which
25892 specific thread is now running, and can be @samp{all} if all threads
25893 are running. The frontend should assume that no interaction with a
25894 running thread is possible after this notification is produced.
25895 The frontend should not assume that this notification is output
25896 only once for any command. @value{GDBN} may emit this notification
25897 several times, either for different threads, because it cannot resume
25898 all threads together, or even for a single thread, if the thread must
25899 be stepped though some code before letting it run freely.
25901 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25902 The target has stopped. The @var{reason} field can have one of the
25906 @item breakpoint-hit
25907 A breakpoint was reached.
25908 @item watchpoint-trigger
25909 A watchpoint was triggered.
25910 @item read-watchpoint-trigger
25911 A read watchpoint was triggered.
25912 @item access-watchpoint-trigger
25913 An access watchpoint was triggered.
25914 @item function-finished
25915 An -exec-finish or similar CLI command was accomplished.
25916 @item location-reached
25917 An -exec-until or similar CLI command was accomplished.
25918 @item watchpoint-scope
25919 A watchpoint has gone out of scope.
25920 @item end-stepping-range
25921 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25922 similar CLI command was accomplished.
25923 @item exited-signalled
25924 The inferior exited because of a signal.
25926 The inferior exited.
25927 @item exited-normally
25928 The inferior exited normally.
25929 @item signal-received
25930 A signal was received by the inferior.
25932 The inferior has stopped due to a library being loaded or unloaded.
25933 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25934 set or when a @code{catch load} or @code{catch unload} catchpoint is
25935 in use (@pxref{Set Catchpoints}).
25937 The inferior has forked. This is reported when @code{catch fork}
25938 (@pxref{Set Catchpoints}) has been used.
25940 The inferior has vforked. This is reported in when @code{catch vfork}
25941 (@pxref{Set Catchpoints}) has been used.
25942 @item syscall-entry
25943 The inferior entered a system call. This is reported when @code{catch
25944 syscall} (@pxref{Set Catchpoints}) has been used.
25945 @item syscall-return
25946 The inferior returned from a system call. This is reported when
25947 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
25949 The inferior called @code{exec}. This is reported when @code{catch exec}
25950 (@pxref{Set Catchpoints}) has been used.
25953 The @var{id} field identifies the thread that directly caused the stop
25954 -- for example by hitting a breakpoint. Depending on whether all-stop
25955 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25956 stop all threads, or only the thread that directly triggered the stop.
25957 If all threads are stopped, the @var{stopped} field will have the
25958 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25959 field will be a list of thread identifiers. Presently, this list will
25960 always include a single thread, but frontend should be prepared to see
25961 several threads in the list. The @var{core} field reports the
25962 processor core on which the stop event has happened. This field may be absent
25963 if such information is not available.
25965 @item =thread-group-added,id="@var{id}"
25966 @itemx =thread-group-removed,id="@var{id}"
25967 A thread group was either added or removed. The @var{id} field
25968 contains the @value{GDBN} identifier of the thread group. When a thread
25969 group is added, it generally might not be associated with a running
25970 process. When a thread group is removed, its id becomes invalid and
25971 cannot be used in any way.
25973 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25974 A thread group became associated with a running program,
25975 either because the program was just started or the thread group
25976 was attached to a program. The @var{id} field contains the
25977 @value{GDBN} identifier of the thread group. The @var{pid} field
25978 contains process identifier, specific to the operating system.
25980 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25981 A thread group is no longer associated with a running program,
25982 either because the program has exited, or because it was detached
25983 from. The @var{id} field contains the @value{GDBN} identifier of the
25984 thread group. The @var{code} field is the exit code of the inferior; it exists
25985 only when the inferior exited with some code.
25987 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25988 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25989 A thread either was created, or has exited. The @var{id} field
25990 contains the @value{GDBN} identifier of the thread. The @var{gid}
25991 field identifies the thread group this thread belongs to.
25993 @item =thread-selected,id="@var{id}"
25994 Informs that the selected thread was changed as result of the last
25995 command. This notification is not emitted as result of @code{-thread-select}
25996 command but is emitted whenever an MI command that is not documented
25997 to change the selected thread actually changes it. In particular,
25998 invoking, directly or indirectly (via user-defined command), the CLI
25999 @code{thread} command, will generate this notification.
26001 We suggest that in response to this notification, front ends
26002 highlight the selected thread and cause subsequent commands to apply to
26005 @item =library-loaded,...
26006 Reports that a new library file was loaded by the program. This
26007 notification has 4 fields---@var{id}, @var{target-name},
26008 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26009 opaque identifier of the library. For remote debugging case,
26010 @var{target-name} and @var{host-name} fields give the name of the
26011 library file on the target, and on the host respectively. For native
26012 debugging, both those fields have the same value. The
26013 @var{symbols-loaded} field is emitted only for backward compatibility
26014 and should not be relied on to convey any useful information. The
26015 @var{thread-group} field, if present, specifies the id of the thread
26016 group in whose context the library was loaded. If the field is
26017 absent, it means the library was loaded in the context of all present
26020 @item =library-unloaded,...
26021 Reports that a library was unloaded by the program. This notification
26022 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26023 the same meaning as for the @code{=library-loaded} notification.
26024 The @var{thread-group} field, if present, specifies the id of the
26025 thread group in whose context the library was unloaded. If the field is
26026 absent, it means the library was unloaded in the context of all present
26029 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26030 @itemx =traceframe-changed,end
26031 Reports that the trace frame was changed and its new number is
26032 @var{tfnum}. The number of the tracepoint associated with this trace
26033 frame is @var{tpnum}.
26035 @item =tsv-created,name=@var{name},initial=@var{initial}
26036 Reports that the new trace state variable @var{name} is created with
26037 initial value @var{initial}.
26039 @item =tsv-deleted,name=@var{name}
26040 @itemx =tsv-deleted
26041 Reports that the trace state variable @var{name} is deleted or all
26042 trace state variables are deleted.
26044 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26045 Reports that the trace state variable @var{name} is modified with
26046 the initial value @var{initial}. The current value @var{current} of
26047 trace state variable is optional and is reported if the current
26048 value of trace state variable is known.
26050 @item =breakpoint-created,bkpt=@{...@}
26051 @itemx =breakpoint-modified,bkpt=@{...@}
26052 @itemx =breakpoint-deleted,id=@var{number}
26053 Reports that a breakpoint was created, modified, or deleted,
26054 respectively. Only user-visible breakpoints are reported to the MI
26057 The @var{bkpt} argument is of the same form as returned by the various
26058 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26059 @var{number} is the ordinal number of the breakpoint.
26061 Note that if a breakpoint is emitted in the result record of a
26062 command, then it will not also be emitted in an async record.
26064 @item =record-started,thread-group="@var{id}"
26065 @itemx =record-stopped,thread-group="@var{id}"
26066 Execution log recording was either started or stopped on an
26067 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26068 group corresponding to the affected inferior.
26070 @item =cmd-param-changed,param=@var{param},value=@var{value}
26071 Reports that a parameter of the command @code{set @var{param}} is
26072 changed to @var{value}. In the multi-word @code{set} command,
26073 the @var{param} is the whole parameter list to @code{set} command.
26074 For example, In command @code{set check type on}, @var{param}
26075 is @code{check type} and @var{value} is @code{on}.
26077 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26078 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26079 written in an inferior. The @var{id} is the identifier of the
26080 thread group corresponding to the affected inferior. The optional
26081 @code{type="code"} part is reported if the memory written to holds
26085 @node GDB/MI Breakpoint Information
26086 @subsection @sc{gdb/mi} Breakpoint Information
26088 When @value{GDBN} reports information about a breakpoint, a
26089 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26094 The breakpoint number. For a breakpoint that represents one location
26095 of a multi-location breakpoint, this will be a dotted pair, like
26099 The type of the breakpoint. For ordinary breakpoints this will be
26100 @samp{breakpoint}, but many values are possible.
26103 If the type of the breakpoint is @samp{catchpoint}, then this
26104 indicates the exact type of catchpoint.
26107 This is the breakpoint disposition---either @samp{del}, meaning that
26108 the breakpoint will be deleted at the next stop, or @samp{keep},
26109 meaning that the breakpoint will not be deleted.
26112 This indicates whether the breakpoint is enabled, in which case the
26113 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26114 Note that this is not the same as the field @code{enable}.
26117 The address of the breakpoint. This may be a hexidecimal number,
26118 giving the address; or the string @samp{<PENDING>}, for a pending
26119 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26120 multiple locations. This field will not be present if no address can
26121 be determined. For example, a watchpoint does not have an address.
26124 If known, the function in which the breakpoint appears.
26125 If not known, this field is not present.
26128 The name of the source file which contains this function, if known.
26129 If not known, this field is not present.
26132 The full file name of the source file which contains this function, if
26133 known. If not known, this field is not present.
26136 The line number at which this breakpoint appears, if known.
26137 If not known, this field is not present.
26140 If the source file is not known, this field may be provided. If
26141 provided, this holds the address of the breakpoint, possibly followed
26145 If this breakpoint is pending, this field is present and holds the
26146 text used to set the breakpoint, as entered by the user.
26149 Where this breakpoint's condition is evaluated, either @samp{host} or
26153 If this is a thread-specific breakpoint, then this identifies the
26154 thread in which the breakpoint can trigger.
26157 If this breakpoint is restricted to a particular Ada task, then this
26158 field will hold the task identifier.
26161 If the breakpoint is conditional, this is the condition expression.
26164 The ignore count of the breakpoint.
26167 The enable count of the breakpoint.
26169 @item traceframe-usage
26172 @item static-tracepoint-marker-string-id
26173 For a static tracepoint, the name of the static tracepoint marker.
26176 For a masked watchpoint, this is the mask.
26179 A tracepoint's pass count.
26181 @item original-location
26182 The location of the breakpoint as originally specified by the user.
26183 This field is optional.
26186 The number of times the breakpoint has been hit.
26189 This field is only given for tracepoints. This is either @samp{y},
26190 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26194 Some extra data, the exact contents of which are type-dependent.
26198 For example, here is what the output of @code{-break-insert}
26199 (@pxref{GDB/MI Breakpoint Commands}) might be:
26202 -> -break-insert main
26203 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26204 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26205 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26210 @node GDB/MI Frame Information
26211 @subsection @sc{gdb/mi} Frame Information
26213 Response from many MI commands includes an information about stack
26214 frame. This information is a tuple that may have the following
26219 The level of the stack frame. The innermost frame has the level of
26220 zero. This field is always present.
26223 The name of the function corresponding to the frame. This field may
26224 be absent if @value{GDBN} is unable to determine the function name.
26227 The code address for the frame. This field is always present.
26230 The name of the source files that correspond to the frame's code
26231 address. This field may be absent.
26234 The source line corresponding to the frames' code address. This field
26238 The name of the binary file (either executable or shared library) the
26239 corresponds to the frame's code address. This field may be absent.
26243 @node GDB/MI Thread Information
26244 @subsection @sc{gdb/mi} Thread Information
26246 Whenever @value{GDBN} has to report an information about a thread, it
26247 uses a tuple with the following fields:
26251 The numeric id assigned to the thread by @value{GDBN}. This field is
26255 Target-specific string identifying the thread. This field is always present.
26258 Additional information about the thread provided by the target.
26259 It is supposed to be human-readable and not interpreted by the
26260 frontend. This field is optional.
26263 Either @samp{stopped} or @samp{running}, depending on whether the
26264 thread is presently running. This field is always present.
26267 The value of this field is an integer number of the processor core the
26268 thread was last seen on. This field is optional.
26271 @node GDB/MI Ada Exception Information
26272 @subsection @sc{gdb/mi} Ada Exception Information
26274 Whenever a @code{*stopped} record is emitted because the program
26275 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26276 @value{GDBN} provides the name of the exception that was raised via
26277 the @code{exception-name} field.
26279 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26280 @node GDB/MI Simple Examples
26281 @section Simple Examples of @sc{gdb/mi} Interaction
26282 @cindex @sc{gdb/mi}, simple examples
26284 This subsection presents several simple examples of interaction using
26285 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26286 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26287 the output received from @sc{gdb/mi}.
26289 Note the line breaks shown in the examples are here only for
26290 readability, they don't appear in the real output.
26292 @subheading Setting a Breakpoint
26294 Setting a breakpoint generates synchronous output which contains detailed
26295 information of the breakpoint.
26298 -> -break-insert main
26299 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26300 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26301 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26306 @subheading Program Execution
26308 Program execution generates asynchronous records and MI gives the
26309 reason that execution stopped.
26315 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26316 frame=@{addr="0x08048564",func="main",
26317 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26318 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26323 <- *stopped,reason="exited-normally"
26327 @subheading Quitting @value{GDBN}
26329 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26337 Please note that @samp{^exit} is printed immediately, but it might
26338 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26339 performs necessary cleanups, including killing programs being debugged
26340 or disconnecting from debug hardware, so the frontend should wait till
26341 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26342 fails to exit in reasonable time.
26344 @subheading A Bad Command
26346 Here's what happens if you pass a non-existent command:
26350 <- ^error,msg="Undefined MI command: rubbish"
26355 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26356 @node GDB/MI Command Description Format
26357 @section @sc{gdb/mi} Command Description Format
26359 The remaining sections describe blocks of commands. Each block of
26360 commands is laid out in a fashion similar to this section.
26362 @subheading Motivation
26364 The motivation for this collection of commands.
26366 @subheading Introduction
26368 A brief introduction to this collection of commands as a whole.
26370 @subheading Commands
26372 For each command in the block, the following is described:
26374 @subsubheading Synopsis
26377 -command @var{args}@dots{}
26380 @subsubheading Result
26382 @subsubheading @value{GDBN} Command
26384 The corresponding @value{GDBN} CLI command(s), if any.
26386 @subsubheading Example
26388 Example(s) formatted for readability. Some of the described commands have
26389 not been implemented yet and these are labeled N.A.@: (not available).
26392 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26393 @node GDB/MI Breakpoint Commands
26394 @section @sc{gdb/mi} Breakpoint Commands
26396 @cindex breakpoint commands for @sc{gdb/mi}
26397 @cindex @sc{gdb/mi}, breakpoint commands
26398 This section documents @sc{gdb/mi} commands for manipulating
26401 @subheading The @code{-break-after} Command
26402 @findex -break-after
26404 @subsubheading Synopsis
26407 -break-after @var{number} @var{count}
26410 The breakpoint number @var{number} is not in effect until it has been
26411 hit @var{count} times. To see how this is reflected in the output of
26412 the @samp{-break-list} command, see the description of the
26413 @samp{-break-list} command below.
26415 @subsubheading @value{GDBN} Command
26417 The corresponding @value{GDBN} command is @samp{ignore}.
26419 @subsubheading Example
26424 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26425 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26426 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26434 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26435 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26436 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26437 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26438 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26439 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26440 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26441 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26442 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26443 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26448 @subheading The @code{-break-catch} Command
26449 @findex -break-catch
26452 @subheading The @code{-break-commands} Command
26453 @findex -break-commands
26455 @subsubheading Synopsis
26458 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26461 Specifies the CLI commands that should be executed when breakpoint
26462 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26463 are the commands. If no command is specified, any previously-set
26464 commands are cleared. @xref{Break Commands}. Typical use of this
26465 functionality is tracing a program, that is, printing of values of
26466 some variables whenever breakpoint is hit and then continuing.
26468 @subsubheading @value{GDBN} Command
26470 The corresponding @value{GDBN} command is @samp{commands}.
26472 @subsubheading Example
26477 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26478 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26479 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26482 -break-commands 1 "print v" "continue"
26487 @subheading The @code{-break-condition} Command
26488 @findex -break-condition
26490 @subsubheading Synopsis
26493 -break-condition @var{number} @var{expr}
26496 Breakpoint @var{number} will stop the program only if the condition in
26497 @var{expr} is true. The condition becomes part of the
26498 @samp{-break-list} output (see the description of the @samp{-break-list}
26501 @subsubheading @value{GDBN} Command
26503 The corresponding @value{GDBN} command is @samp{condition}.
26505 @subsubheading Example
26509 -break-condition 1 1
26513 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26514 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26515 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26516 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26517 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26518 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26519 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26520 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26521 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26522 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26526 @subheading The @code{-break-delete} Command
26527 @findex -break-delete
26529 @subsubheading Synopsis
26532 -break-delete ( @var{breakpoint} )+
26535 Delete the breakpoint(s) whose number(s) are specified in the argument
26536 list. This is obviously reflected in the breakpoint list.
26538 @subsubheading @value{GDBN} Command
26540 The corresponding @value{GDBN} command is @samp{delete}.
26542 @subsubheading Example
26550 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26551 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26552 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26553 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26554 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26555 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26556 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26561 @subheading The @code{-break-disable} Command
26562 @findex -break-disable
26564 @subsubheading Synopsis
26567 -break-disable ( @var{breakpoint} )+
26570 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26571 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26573 @subsubheading @value{GDBN} Command
26575 The corresponding @value{GDBN} command is @samp{disable}.
26577 @subsubheading Example
26585 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26586 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26587 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26588 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26589 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26590 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26591 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26592 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26593 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26594 line="5",thread-groups=["i1"],times="0"@}]@}
26598 @subheading The @code{-break-enable} Command
26599 @findex -break-enable
26601 @subsubheading Synopsis
26604 -break-enable ( @var{breakpoint} )+
26607 Enable (previously disabled) @var{breakpoint}(s).
26609 @subsubheading @value{GDBN} Command
26611 The corresponding @value{GDBN} command is @samp{enable}.
26613 @subsubheading Example
26621 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26622 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26623 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26624 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26625 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26626 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26627 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26628 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26629 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26630 line="5",thread-groups=["i1"],times="0"@}]@}
26634 @subheading The @code{-break-info} Command
26635 @findex -break-info
26637 @subsubheading Synopsis
26640 -break-info @var{breakpoint}
26644 Get information about a single breakpoint.
26646 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26647 Information}, for details on the format of each breakpoint in the
26650 @subsubheading @value{GDBN} Command
26652 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26654 @subsubheading Example
26657 @subheading The @code{-break-insert} Command
26658 @findex -break-insert
26659 @anchor{-break-insert}
26661 @subsubheading Synopsis
26664 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26665 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26666 [ -p @var{thread-id} ] [ @var{location} ]
26670 If specified, @var{location}, can be one of:
26673 @item linespec location
26674 A linespec location. @xref{Linespec Locations}.
26676 @item explicit location
26677 An explicit location. @sc{gdb/mi} explicit locations are
26678 analogous to the CLI's explicit locations using the option names
26679 listed below. @xref{Explicit Locations}.
26682 @item --source @var{filename}
26683 The source file name of the location. This option requires the use
26684 of either @samp{--function} or @samp{--line}.
26686 @item --function @var{function}
26687 The name of a function or method.
26689 @item --label @var{label}
26690 The name of a label.
26692 @item --line @var{lineoffset}
26693 An absolute or relative line offset from the start of the location.
26696 @item address location
26697 An address location, *@var{address}. @xref{Address Locations}.
26701 The possible optional parameters of this command are:
26705 Insert a temporary breakpoint.
26707 Insert a hardware breakpoint.
26709 If @var{location} cannot be parsed (for example if it
26710 refers to unknown files or functions), create a pending
26711 breakpoint. Without this flag, @value{GDBN} will report
26712 an error, and won't create a breakpoint, if @var{location}
26715 Create a disabled breakpoint.
26717 Create a tracepoint. @xref{Tracepoints}. When this parameter
26718 is used together with @samp{-h}, a fast tracepoint is created.
26719 @item -c @var{condition}
26720 Make the breakpoint conditional on @var{condition}.
26721 @item -i @var{ignore-count}
26722 Initialize the @var{ignore-count}.
26723 @item -p @var{thread-id}
26724 Restrict the breakpoint to the specified @var{thread-id}.
26727 @subsubheading Result
26729 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26730 resulting breakpoint.
26732 Note: this format is open to change.
26733 @c An out-of-band breakpoint instead of part of the result?
26735 @subsubheading @value{GDBN} Command
26737 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26738 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26740 @subsubheading Example
26745 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26746 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26749 -break-insert -t foo
26750 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26751 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26755 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26756 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26757 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26758 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26759 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26760 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26761 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26762 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26763 addr="0x0001072c", func="main",file="recursive2.c",
26764 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26766 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26767 addr="0x00010774",func="foo",file="recursive2.c",
26768 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26771 @c -break-insert -r foo.*
26772 @c ~int foo(int, int);
26773 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26774 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26779 @subheading The @code{-dprintf-insert} Command
26780 @findex -dprintf-insert
26782 @subsubheading Synopsis
26785 -dprintf-insert [ -t ] [ -f ] [ -d ]
26786 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26787 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26792 If supplied, @var{location} may be specified the same way as for
26793 the @code{-break-insert} command. @xref{-break-insert}.
26795 The possible optional parameters of this command are:
26799 Insert a temporary breakpoint.
26801 If @var{location} cannot be parsed (for example, if it
26802 refers to unknown files or functions), create a pending
26803 breakpoint. Without this flag, @value{GDBN} will report
26804 an error, and won't create a breakpoint, if @var{location}
26807 Create a disabled breakpoint.
26808 @item -c @var{condition}
26809 Make the breakpoint conditional on @var{condition}.
26810 @item -i @var{ignore-count}
26811 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26812 to @var{ignore-count}.
26813 @item -p @var{thread-id}
26814 Restrict the breakpoint to the specified @var{thread-id}.
26817 @subsubheading Result
26819 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26820 resulting breakpoint.
26822 @c An out-of-band breakpoint instead of part of the result?
26824 @subsubheading @value{GDBN} Command
26826 The corresponding @value{GDBN} command is @samp{dprintf}.
26828 @subsubheading Example
26832 4-dprintf-insert foo "At foo entry\n"
26833 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26834 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26835 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26836 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26837 original-location="foo"@}
26839 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26840 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26841 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26842 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26843 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26844 original-location="mi-dprintf.c:26"@}
26848 @subheading The @code{-break-list} Command
26849 @findex -break-list
26851 @subsubheading Synopsis
26857 Displays the list of inserted breakpoints, showing the following fields:
26861 number of the breakpoint
26863 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26865 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26868 is the breakpoint enabled or no: @samp{y} or @samp{n}
26870 memory location at which the breakpoint is set
26872 logical location of the breakpoint, expressed by function name, file
26874 @item Thread-groups
26875 list of thread groups to which this breakpoint applies
26877 number of times the breakpoint has been hit
26880 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26881 @code{body} field is an empty list.
26883 @subsubheading @value{GDBN} Command
26885 The corresponding @value{GDBN} command is @samp{info break}.
26887 @subsubheading Example
26892 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26893 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26894 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26895 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26896 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26897 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26898 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26899 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26900 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26902 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26903 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26904 line="13",thread-groups=["i1"],times="0"@}]@}
26908 Here's an example of the result when there are no breakpoints:
26913 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26914 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26915 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26916 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26917 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26918 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26919 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26924 @subheading The @code{-break-passcount} Command
26925 @findex -break-passcount
26927 @subsubheading Synopsis
26930 -break-passcount @var{tracepoint-number} @var{passcount}
26933 Set the passcount for tracepoint @var{tracepoint-number} to
26934 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26935 is not a tracepoint, error is emitted. This corresponds to CLI
26936 command @samp{passcount}.
26938 @subheading The @code{-break-watch} Command
26939 @findex -break-watch
26941 @subsubheading Synopsis
26944 -break-watch [ -a | -r ]
26947 Create a watchpoint. With the @samp{-a} option it will create an
26948 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26949 read from or on a write to the memory location. With the @samp{-r}
26950 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26951 trigger only when the memory location is accessed for reading. Without
26952 either of the options, the watchpoint created is a regular watchpoint,
26953 i.e., it will trigger when the memory location is accessed for writing.
26954 @xref{Set Watchpoints, , Setting Watchpoints}.
26956 Note that @samp{-break-list} will report a single list of watchpoints and
26957 breakpoints inserted.
26959 @subsubheading @value{GDBN} Command
26961 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26964 @subsubheading Example
26966 Setting a watchpoint on a variable in the @code{main} function:
26971 ^done,wpt=@{number="2",exp="x"@}
26976 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26977 value=@{old="-268439212",new="55"@},
26978 frame=@{func="main",args=[],file="recursive2.c",
26979 fullname="/home/foo/bar/recursive2.c",line="5"@}
26983 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26984 the program execution twice: first for the variable changing value, then
26985 for the watchpoint going out of scope.
26990 ^done,wpt=@{number="5",exp="C"@}
26995 *stopped,reason="watchpoint-trigger",
26996 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26997 frame=@{func="callee4",args=[],
26998 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26999 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27004 *stopped,reason="watchpoint-scope",wpnum="5",
27005 frame=@{func="callee3",args=[@{name="strarg",
27006 value="0x11940 \"A string argument.\""@}],
27007 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27008 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27012 Listing breakpoints and watchpoints, at different points in the program
27013 execution. Note that once the watchpoint goes out of scope, it is
27019 ^done,wpt=@{number="2",exp="C"@}
27022 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27023 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27024 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27025 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27026 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27027 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27028 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27029 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27030 addr="0x00010734",func="callee4",
27031 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27032 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27034 bkpt=@{number="2",type="watchpoint",disp="keep",
27035 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27040 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27041 value=@{old="-276895068",new="3"@},
27042 frame=@{func="callee4",args=[],
27043 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27044 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27047 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27048 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27049 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27050 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27051 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27052 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27053 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27054 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27055 addr="0x00010734",func="callee4",
27056 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27057 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27059 bkpt=@{number="2",type="watchpoint",disp="keep",
27060 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27064 ^done,reason="watchpoint-scope",wpnum="2",
27065 frame=@{func="callee3",args=[@{name="strarg",
27066 value="0x11940 \"A string argument.\""@}],
27067 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27068 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27071 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27072 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27073 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27074 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27075 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27076 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27077 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27078 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27079 addr="0x00010734",func="callee4",
27080 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27081 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27082 thread-groups=["i1"],times="1"@}]@}
27087 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27088 @node GDB/MI Catchpoint Commands
27089 @section @sc{gdb/mi} Catchpoint Commands
27091 This section documents @sc{gdb/mi} commands for manipulating
27095 * Shared Library GDB/MI Catchpoint Commands::
27096 * Ada Exception GDB/MI Catchpoint Commands::
27099 @node Shared Library GDB/MI Catchpoint Commands
27100 @subsection Shared Library @sc{gdb/mi} Catchpoints
27102 @subheading The @code{-catch-load} Command
27103 @findex -catch-load
27105 @subsubheading Synopsis
27108 -catch-load [ -t ] [ -d ] @var{regexp}
27111 Add a catchpoint for library load events. If the @samp{-t} option is used,
27112 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27113 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27114 in a disabled state. The @samp{regexp} argument is a regular
27115 expression used to match the name of the loaded library.
27118 @subsubheading @value{GDBN} Command
27120 The corresponding @value{GDBN} command is @samp{catch load}.
27122 @subsubheading Example
27125 -catch-load -t foo.so
27126 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27127 what="load of library matching foo.so",catch-type="load",times="0"@}
27132 @subheading The @code{-catch-unload} Command
27133 @findex -catch-unload
27135 @subsubheading Synopsis
27138 -catch-unload [ -t ] [ -d ] @var{regexp}
27141 Add a catchpoint for library unload events. If the @samp{-t} option is
27142 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27143 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27144 created in a disabled state. The @samp{regexp} argument is a regular
27145 expression used to match the name of the unloaded library.
27147 @subsubheading @value{GDBN} Command
27149 The corresponding @value{GDBN} command is @samp{catch unload}.
27151 @subsubheading Example
27154 -catch-unload -d bar.so
27155 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27156 what="load of library matching bar.so",catch-type="unload",times="0"@}
27160 @node Ada Exception GDB/MI Catchpoint Commands
27161 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27163 The following @sc{gdb/mi} commands can be used to create catchpoints
27164 that stop the execution when Ada exceptions are being raised.
27166 @subheading The @code{-catch-assert} Command
27167 @findex -catch-assert
27169 @subsubheading Synopsis
27172 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27175 Add a catchpoint for failed Ada assertions.
27177 The possible optional parameters for this command are:
27180 @item -c @var{condition}
27181 Make the catchpoint conditional on @var{condition}.
27183 Create a disabled catchpoint.
27185 Create a temporary catchpoint.
27188 @subsubheading @value{GDBN} Command
27190 The corresponding @value{GDBN} command is @samp{catch assert}.
27192 @subsubheading Example
27196 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27197 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27198 thread-groups=["i1"],times="0",
27199 original-location="__gnat_debug_raise_assert_failure"@}
27203 @subheading The @code{-catch-exception} Command
27204 @findex -catch-exception
27206 @subsubheading Synopsis
27209 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27213 Add a catchpoint stopping when Ada exceptions are raised.
27214 By default, the command stops the program when any Ada exception
27215 gets raised. But it is also possible, by using some of the
27216 optional parameters described below, to create more selective
27219 The possible optional parameters for this command are:
27222 @item -c @var{condition}
27223 Make the catchpoint conditional on @var{condition}.
27225 Create a disabled catchpoint.
27226 @item -e @var{exception-name}
27227 Only stop when @var{exception-name} is raised. This option cannot
27228 be used combined with @samp{-u}.
27230 Create a temporary catchpoint.
27232 Stop only when an unhandled exception gets raised. This option
27233 cannot be used combined with @samp{-e}.
27236 @subsubheading @value{GDBN} Command
27238 The corresponding @value{GDBN} commands are @samp{catch exception}
27239 and @samp{catch exception unhandled}.
27241 @subsubheading Example
27244 -catch-exception -e Program_Error
27245 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27246 enabled="y",addr="0x0000000000404874",
27247 what="`Program_Error' Ada exception", thread-groups=["i1"],
27248 times="0",original-location="__gnat_debug_raise_exception"@}
27252 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27253 @node GDB/MI Program Context
27254 @section @sc{gdb/mi} Program Context
27256 @subheading The @code{-exec-arguments} Command
27257 @findex -exec-arguments
27260 @subsubheading Synopsis
27263 -exec-arguments @var{args}
27266 Set the inferior program arguments, to be used in the next
27269 @subsubheading @value{GDBN} Command
27271 The corresponding @value{GDBN} command is @samp{set args}.
27273 @subsubheading Example
27277 -exec-arguments -v word
27284 @subheading The @code{-exec-show-arguments} Command
27285 @findex -exec-show-arguments
27287 @subsubheading Synopsis
27290 -exec-show-arguments
27293 Print the arguments of the program.
27295 @subsubheading @value{GDBN} Command
27297 The corresponding @value{GDBN} command is @samp{show args}.
27299 @subsubheading Example
27304 @subheading The @code{-environment-cd} Command
27305 @findex -environment-cd
27307 @subsubheading Synopsis
27310 -environment-cd @var{pathdir}
27313 Set @value{GDBN}'s working directory.
27315 @subsubheading @value{GDBN} Command
27317 The corresponding @value{GDBN} command is @samp{cd}.
27319 @subsubheading Example
27323 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27329 @subheading The @code{-environment-directory} Command
27330 @findex -environment-directory
27332 @subsubheading Synopsis
27335 -environment-directory [ -r ] [ @var{pathdir} ]+
27338 Add directories @var{pathdir} to beginning of search path for source files.
27339 If the @samp{-r} option is used, the search path is reset to the default
27340 search path. If directories @var{pathdir} are supplied in addition to the
27341 @samp{-r} option, the search path is first reset and then addition
27343 Multiple directories may be specified, separated by blanks. Specifying
27344 multiple directories in a single command
27345 results in the directories added to the beginning of the
27346 search path in the same order they were presented in the command.
27347 If blanks are needed as
27348 part of a directory name, double-quotes should be used around
27349 the name. In the command output, the path will show up separated
27350 by the system directory-separator character. The directory-separator
27351 character must not be used
27352 in any directory name.
27353 If no directories are specified, the current search path is displayed.
27355 @subsubheading @value{GDBN} Command
27357 The corresponding @value{GDBN} command is @samp{dir}.
27359 @subsubheading Example
27363 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27364 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27366 -environment-directory ""
27367 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27369 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27370 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27372 -environment-directory -r
27373 ^done,source-path="$cdir:$cwd"
27378 @subheading The @code{-environment-path} Command
27379 @findex -environment-path
27381 @subsubheading Synopsis
27384 -environment-path [ -r ] [ @var{pathdir} ]+
27387 Add directories @var{pathdir} to beginning of search path for object files.
27388 If the @samp{-r} option is used, the search path is reset to the original
27389 search path that existed at gdb start-up. If directories @var{pathdir} are
27390 supplied in addition to the
27391 @samp{-r} option, the search path is first reset and then addition
27393 Multiple directories may be specified, separated by blanks. Specifying
27394 multiple directories in a single command
27395 results in the directories added to the beginning of the
27396 search path in the same order they were presented in the command.
27397 If blanks are needed as
27398 part of a directory name, double-quotes should be used around
27399 the name. In the command output, the path will show up separated
27400 by the system directory-separator character. The directory-separator
27401 character must not be used
27402 in any directory name.
27403 If no directories are specified, the current path is displayed.
27406 @subsubheading @value{GDBN} Command
27408 The corresponding @value{GDBN} command is @samp{path}.
27410 @subsubheading Example
27415 ^done,path="/usr/bin"
27417 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27418 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27420 -environment-path -r /usr/local/bin
27421 ^done,path="/usr/local/bin:/usr/bin"
27426 @subheading The @code{-environment-pwd} Command
27427 @findex -environment-pwd
27429 @subsubheading Synopsis
27435 Show the current working directory.
27437 @subsubheading @value{GDBN} Command
27439 The corresponding @value{GDBN} command is @samp{pwd}.
27441 @subsubheading Example
27446 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27450 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27451 @node GDB/MI Thread Commands
27452 @section @sc{gdb/mi} Thread Commands
27455 @subheading The @code{-thread-info} Command
27456 @findex -thread-info
27458 @subsubheading Synopsis
27461 -thread-info [ @var{thread-id} ]
27464 Reports information about either a specific thread, if
27465 the @var{thread-id} parameter is present, or about all
27466 threads. When printing information about all threads,
27467 also reports the current thread.
27469 @subsubheading @value{GDBN} Command
27471 The @samp{info thread} command prints the same information
27474 @subsubheading Result
27476 The result is a list of threads. The following attributes are
27477 defined for a given thread:
27481 This field exists only for the current thread. It has the value @samp{*}.
27484 The identifier that @value{GDBN} uses to refer to the thread.
27487 The identifier that the target uses to refer to the thread.
27490 Extra information about the thread, in a target-specific format. This
27494 The name of the thread. If the user specified a name using the
27495 @code{thread name} command, then this name is given. Otherwise, if
27496 @value{GDBN} can extract the thread name from the target, then that
27497 name is given. If @value{GDBN} cannot find the thread name, then this
27501 The stack frame currently executing in the thread.
27504 The thread's state. The @samp{state} field may have the following
27509 The thread is stopped. Frame information is available for stopped
27513 The thread is running. There's no frame information for running
27519 If @value{GDBN} can find the CPU core on which this thread is running,
27520 then this field is the core identifier. This field is optional.
27524 @subsubheading Example
27529 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27530 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27531 args=[]@},state="running"@},
27532 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27533 frame=@{level="0",addr="0x0804891f",func="foo",
27534 args=[@{name="i",value="10"@}],
27535 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27536 state="running"@}],
27537 current-thread-id="1"
27541 @subheading The @code{-thread-list-ids} Command
27542 @findex -thread-list-ids
27544 @subsubheading Synopsis
27550 Produces a list of the currently known @value{GDBN} thread ids. At the
27551 end of the list it also prints the total number of such threads.
27553 This command is retained for historical reasons, the
27554 @code{-thread-info} command should be used instead.
27556 @subsubheading @value{GDBN} Command
27558 Part of @samp{info threads} supplies the same information.
27560 @subsubheading Example
27565 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27566 current-thread-id="1",number-of-threads="3"
27571 @subheading The @code{-thread-select} Command
27572 @findex -thread-select
27574 @subsubheading Synopsis
27577 -thread-select @var{threadnum}
27580 Make @var{threadnum} the current thread. It prints the number of the new
27581 current thread, and the topmost frame for that thread.
27583 This command is deprecated in favor of explicitly using the
27584 @samp{--thread} option to each command.
27586 @subsubheading @value{GDBN} Command
27588 The corresponding @value{GDBN} command is @samp{thread}.
27590 @subsubheading Example
27597 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27598 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27602 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27603 number-of-threads="3"
27606 ^done,new-thread-id="3",
27607 frame=@{level="0",func="vprintf",
27608 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27609 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27613 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27614 @node GDB/MI Ada Tasking Commands
27615 @section @sc{gdb/mi} Ada Tasking Commands
27617 @subheading The @code{-ada-task-info} Command
27618 @findex -ada-task-info
27620 @subsubheading Synopsis
27623 -ada-task-info [ @var{task-id} ]
27626 Reports information about either a specific Ada task, if the
27627 @var{task-id} parameter is present, or about all Ada tasks.
27629 @subsubheading @value{GDBN} Command
27631 The @samp{info tasks} command prints the same information
27632 about all Ada tasks (@pxref{Ada Tasks}).
27634 @subsubheading Result
27636 The result is a table of Ada tasks. The following columns are
27637 defined for each Ada task:
27641 This field exists only for the current thread. It has the value @samp{*}.
27644 The identifier that @value{GDBN} uses to refer to the Ada task.
27647 The identifier that the target uses to refer to the Ada task.
27650 The identifier of the thread corresponding to the Ada task.
27652 This field should always exist, as Ada tasks are always implemented
27653 on top of a thread. But if @value{GDBN} cannot find this corresponding
27654 thread for any reason, the field is omitted.
27657 This field exists only when the task was created by another task.
27658 In this case, it provides the ID of the parent task.
27661 The base priority of the task.
27664 The current state of the task. For a detailed description of the
27665 possible states, see @ref{Ada Tasks}.
27668 The name of the task.
27672 @subsubheading Example
27676 ^done,tasks=@{nr_rows="3",nr_cols="8",
27677 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27678 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27679 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27680 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27681 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27682 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27683 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27684 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27685 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27686 state="Child Termination Wait",name="main_task"@}]@}
27690 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27691 @node GDB/MI Program Execution
27692 @section @sc{gdb/mi} Program Execution
27694 These are the asynchronous commands which generate the out-of-band
27695 record @samp{*stopped}. Currently @value{GDBN} only really executes
27696 asynchronously with remote targets and this interaction is mimicked in
27699 @subheading The @code{-exec-continue} Command
27700 @findex -exec-continue
27702 @subsubheading Synopsis
27705 -exec-continue [--reverse] [--all|--thread-group N]
27708 Resumes the execution of the inferior program, which will continue
27709 to execute until it reaches a debugger stop event. If the
27710 @samp{--reverse} option is specified, execution resumes in reverse until
27711 it reaches a stop event. Stop events may include
27714 breakpoints or watchpoints
27716 signals or exceptions
27718 the end of the process (or its beginning under @samp{--reverse})
27720 the end or beginning of a replay log if one is being used.
27722 In all-stop mode (@pxref{All-Stop
27723 Mode}), may resume only one thread, or all threads, depending on the
27724 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27725 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27726 ignored in all-stop mode. If the @samp{--thread-group} options is
27727 specified, then all threads in that thread group are resumed.
27729 @subsubheading @value{GDBN} Command
27731 The corresponding @value{GDBN} corresponding is @samp{continue}.
27733 @subsubheading Example
27740 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27741 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27747 @subheading The @code{-exec-finish} Command
27748 @findex -exec-finish
27750 @subsubheading Synopsis
27753 -exec-finish [--reverse]
27756 Resumes the execution of the inferior program until the current
27757 function is exited. Displays the results returned by the function.
27758 If the @samp{--reverse} option is specified, resumes the reverse
27759 execution of the inferior program until the point where current
27760 function was called.
27762 @subsubheading @value{GDBN} Command
27764 The corresponding @value{GDBN} command is @samp{finish}.
27766 @subsubheading Example
27768 Function returning @code{void}.
27775 *stopped,reason="function-finished",frame=@{func="main",args=[],
27776 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27780 Function returning other than @code{void}. The name of the internal
27781 @value{GDBN} variable storing the result is printed, together with the
27788 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27789 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27790 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27791 gdb-result-var="$1",return-value="0"
27796 @subheading The @code{-exec-interrupt} Command
27797 @findex -exec-interrupt
27799 @subsubheading Synopsis
27802 -exec-interrupt [--all|--thread-group N]
27805 Interrupts the background execution of the target. Note how the token
27806 associated with the stop message is the one for the execution command
27807 that has been interrupted. The token for the interrupt itself only
27808 appears in the @samp{^done} output. If the user is trying to
27809 interrupt a non-running program, an error message will be printed.
27811 Note that when asynchronous execution is enabled, this command is
27812 asynchronous just like other execution commands. That is, first the
27813 @samp{^done} response will be printed, and the target stop will be
27814 reported after that using the @samp{*stopped} notification.
27816 In non-stop mode, only the context thread is interrupted by default.
27817 All threads (in all inferiors) will be interrupted if the
27818 @samp{--all} option is specified. If the @samp{--thread-group}
27819 option is specified, all threads in that group will be interrupted.
27821 @subsubheading @value{GDBN} Command
27823 The corresponding @value{GDBN} command is @samp{interrupt}.
27825 @subsubheading Example
27836 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27837 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27838 fullname="/home/foo/bar/try.c",line="13"@}
27843 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27847 @subheading The @code{-exec-jump} Command
27850 @subsubheading Synopsis
27853 -exec-jump @var{location}
27856 Resumes execution of the inferior program at the location specified by
27857 parameter. @xref{Specify Location}, for a description of the
27858 different forms of @var{location}.
27860 @subsubheading @value{GDBN} Command
27862 The corresponding @value{GDBN} command is @samp{jump}.
27864 @subsubheading Example
27867 -exec-jump foo.c:10
27868 *running,thread-id="all"
27873 @subheading The @code{-exec-next} Command
27876 @subsubheading Synopsis
27879 -exec-next [--reverse]
27882 Resumes execution of the inferior program, stopping when the beginning
27883 of the next source line is reached.
27885 If the @samp{--reverse} option is specified, resumes reverse execution
27886 of the inferior program, stopping at the beginning of the previous
27887 source line. If you issue this command on the first line of a
27888 function, it will take you back to the caller of that function, to the
27889 source line where the function was called.
27892 @subsubheading @value{GDBN} Command
27894 The corresponding @value{GDBN} command is @samp{next}.
27896 @subsubheading Example
27902 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27907 @subheading The @code{-exec-next-instruction} Command
27908 @findex -exec-next-instruction
27910 @subsubheading Synopsis
27913 -exec-next-instruction [--reverse]
27916 Executes one machine instruction. If the instruction is a function
27917 call, continues until the function returns. If the program stops at an
27918 instruction in the middle of a source line, the address will be
27921 If the @samp{--reverse} option is specified, resumes reverse execution
27922 of the inferior program, stopping at the previous instruction. If the
27923 previously executed instruction was a return from another function,
27924 it will continue to execute in reverse until the call to that function
27925 (from the current stack frame) is reached.
27927 @subsubheading @value{GDBN} Command
27929 The corresponding @value{GDBN} command is @samp{nexti}.
27931 @subsubheading Example
27935 -exec-next-instruction
27939 *stopped,reason="end-stepping-range",
27940 addr="0x000100d4",line="5",file="hello.c"
27945 @subheading The @code{-exec-return} Command
27946 @findex -exec-return
27948 @subsubheading Synopsis
27954 Makes current function return immediately. Doesn't execute the inferior.
27955 Displays the new current frame.
27957 @subsubheading @value{GDBN} Command
27959 The corresponding @value{GDBN} command is @samp{return}.
27961 @subsubheading Example
27965 200-break-insert callee4
27966 200^done,bkpt=@{number="1",addr="0x00010734",
27967 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27972 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27973 frame=@{func="callee4",args=[],
27974 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27975 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27981 111^done,frame=@{level="0",func="callee3",
27982 args=[@{name="strarg",
27983 value="0x11940 \"A string argument.\""@}],
27984 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27985 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27990 @subheading The @code{-exec-run} Command
27993 @subsubheading Synopsis
27996 -exec-run [ --all | --thread-group N ] [ --start ]
27999 Starts execution of the inferior from the beginning. The inferior
28000 executes until either a breakpoint is encountered or the program
28001 exits. In the latter case the output will include an exit code, if
28002 the program has exited exceptionally.
28004 When neither the @samp{--all} nor the @samp{--thread-group} option
28005 is specified, the current inferior is started. If the
28006 @samp{--thread-group} option is specified, it should refer to a thread
28007 group of type @samp{process}, and that thread group will be started.
28008 If the @samp{--all} option is specified, then all inferiors will be started.
28010 Using the @samp{--start} option instructs the debugger to stop
28011 the execution at the start of the inferior's main subprogram,
28012 following the same behavior as the @code{start} command
28013 (@pxref{Starting}).
28015 @subsubheading @value{GDBN} Command
28017 The corresponding @value{GDBN} command is @samp{run}.
28019 @subsubheading Examples
28024 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28029 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28030 frame=@{func="main",args=[],file="recursive2.c",
28031 fullname="/home/foo/bar/recursive2.c",line="4"@}
28036 Program exited normally:
28044 *stopped,reason="exited-normally"
28049 Program exited exceptionally:
28057 *stopped,reason="exited",exit-code="01"
28061 Another way the program can terminate is if it receives a signal such as
28062 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28066 *stopped,reason="exited-signalled",signal-name="SIGINT",
28067 signal-meaning="Interrupt"
28071 @c @subheading -exec-signal
28074 @subheading The @code{-exec-step} Command
28077 @subsubheading Synopsis
28080 -exec-step [--reverse]
28083 Resumes execution of the inferior program, stopping when the beginning
28084 of the next source line is reached, if the next source line is not a
28085 function call. If it is, stop at the first instruction of the called
28086 function. If the @samp{--reverse} option is specified, resumes reverse
28087 execution of the inferior program, stopping at the beginning of the
28088 previously executed source line.
28090 @subsubheading @value{GDBN} Command
28092 The corresponding @value{GDBN} command is @samp{step}.
28094 @subsubheading Example
28096 Stepping into a function:
28102 *stopped,reason="end-stepping-range",
28103 frame=@{func="foo",args=[@{name="a",value="10"@},
28104 @{name="b",value="0"@}],file="recursive2.c",
28105 fullname="/home/foo/bar/recursive2.c",line="11"@}
28115 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28120 @subheading The @code{-exec-step-instruction} Command
28121 @findex -exec-step-instruction
28123 @subsubheading Synopsis
28126 -exec-step-instruction [--reverse]
28129 Resumes the inferior which executes one machine instruction. If the
28130 @samp{--reverse} option is specified, resumes reverse execution of the
28131 inferior program, stopping at the previously executed instruction.
28132 The output, once @value{GDBN} has stopped, will vary depending on
28133 whether we have stopped in the middle of a source line or not. In the
28134 former case, the address at which the program stopped will be printed
28137 @subsubheading @value{GDBN} Command
28139 The corresponding @value{GDBN} command is @samp{stepi}.
28141 @subsubheading Example
28145 -exec-step-instruction
28149 *stopped,reason="end-stepping-range",
28150 frame=@{func="foo",args=[],file="try.c",
28151 fullname="/home/foo/bar/try.c",line="10"@}
28153 -exec-step-instruction
28157 *stopped,reason="end-stepping-range",
28158 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28159 fullname="/home/foo/bar/try.c",line="10"@}
28164 @subheading The @code{-exec-until} Command
28165 @findex -exec-until
28167 @subsubheading Synopsis
28170 -exec-until [ @var{location} ]
28173 Executes the inferior until the @var{location} specified in the
28174 argument is reached. If there is no argument, the inferior executes
28175 until a source line greater than the current one is reached. The
28176 reason for stopping in this case will be @samp{location-reached}.
28178 @subsubheading @value{GDBN} Command
28180 The corresponding @value{GDBN} command is @samp{until}.
28182 @subsubheading Example
28186 -exec-until recursive2.c:6
28190 *stopped,reason="location-reached",frame=@{func="main",args=[],
28191 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28196 @subheading -file-clear
28197 Is this going away????
28200 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28201 @node GDB/MI Stack Manipulation
28202 @section @sc{gdb/mi} Stack Manipulation Commands
28204 @subheading The @code{-enable-frame-filters} Command
28205 @findex -enable-frame-filters
28208 -enable-frame-filters
28211 @value{GDBN} allows Python-based frame filters to affect the output of
28212 the MI commands relating to stack traces. As there is no way to
28213 implement this in a fully backward-compatible way, a front end must
28214 request that this functionality be enabled.
28216 Once enabled, this feature cannot be disabled.
28218 Note that if Python support has not been compiled into @value{GDBN},
28219 this command will still succeed (and do nothing).
28221 @subheading The @code{-stack-info-frame} Command
28222 @findex -stack-info-frame
28224 @subsubheading Synopsis
28230 Get info on the selected frame.
28232 @subsubheading @value{GDBN} Command
28234 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28235 (without arguments).
28237 @subsubheading Example
28242 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28243 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28244 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28248 @subheading The @code{-stack-info-depth} Command
28249 @findex -stack-info-depth
28251 @subsubheading Synopsis
28254 -stack-info-depth [ @var{max-depth} ]
28257 Return the depth of the stack. If the integer argument @var{max-depth}
28258 is specified, do not count beyond @var{max-depth} frames.
28260 @subsubheading @value{GDBN} Command
28262 There's no equivalent @value{GDBN} command.
28264 @subsubheading Example
28266 For a stack with frame levels 0 through 11:
28273 -stack-info-depth 4
28276 -stack-info-depth 12
28279 -stack-info-depth 11
28282 -stack-info-depth 13
28287 @anchor{-stack-list-arguments}
28288 @subheading The @code{-stack-list-arguments} Command
28289 @findex -stack-list-arguments
28291 @subsubheading Synopsis
28294 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28295 [ @var{low-frame} @var{high-frame} ]
28298 Display a list of the arguments for the frames between @var{low-frame}
28299 and @var{high-frame} (inclusive). If @var{low-frame} and
28300 @var{high-frame} are not provided, list the arguments for the whole
28301 call stack. If the two arguments are equal, show the single frame
28302 at the corresponding level. It is an error if @var{low-frame} is
28303 larger than the actual number of frames. On the other hand,
28304 @var{high-frame} may be larger than the actual number of frames, in
28305 which case only existing frames will be returned.
28307 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28308 the variables; if it is 1 or @code{--all-values}, print also their
28309 values; and if it is 2 or @code{--simple-values}, print the name,
28310 type and value for simple data types, and the name and type for arrays,
28311 structures and unions. If the option @code{--no-frame-filters} is
28312 supplied, then Python frame filters will not be executed.
28314 If the @code{--skip-unavailable} option is specified, arguments that
28315 are not available are not listed. Partially available arguments
28316 are still displayed, however.
28318 Use of this command to obtain arguments in a single frame is
28319 deprecated in favor of the @samp{-stack-list-variables} command.
28321 @subsubheading @value{GDBN} Command
28323 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28324 @samp{gdb_get_args} command which partially overlaps with the
28325 functionality of @samp{-stack-list-arguments}.
28327 @subsubheading Example
28334 frame=@{level="0",addr="0x00010734",func="callee4",
28335 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28336 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28337 frame=@{level="1",addr="0x0001076c",func="callee3",
28338 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28339 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28340 frame=@{level="2",addr="0x0001078c",func="callee2",
28341 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28342 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28343 frame=@{level="3",addr="0x000107b4",func="callee1",
28344 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28345 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28346 frame=@{level="4",addr="0x000107e0",func="main",
28347 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28348 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28350 -stack-list-arguments 0
28353 frame=@{level="0",args=[]@},
28354 frame=@{level="1",args=[name="strarg"]@},
28355 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28356 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28357 frame=@{level="4",args=[]@}]
28359 -stack-list-arguments 1
28362 frame=@{level="0",args=[]@},
28364 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28365 frame=@{level="2",args=[
28366 @{name="intarg",value="2"@},
28367 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28368 @{frame=@{level="3",args=[
28369 @{name="intarg",value="2"@},
28370 @{name="strarg",value="0x11940 \"A string argument.\""@},
28371 @{name="fltarg",value="3.5"@}]@},
28372 frame=@{level="4",args=[]@}]
28374 -stack-list-arguments 0 2 2
28375 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28377 -stack-list-arguments 1 2 2
28378 ^done,stack-args=[frame=@{level="2",
28379 args=[@{name="intarg",value="2"@},
28380 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28384 @c @subheading -stack-list-exception-handlers
28387 @anchor{-stack-list-frames}
28388 @subheading The @code{-stack-list-frames} Command
28389 @findex -stack-list-frames
28391 @subsubheading Synopsis
28394 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28397 List the frames currently on the stack. For each frame it displays the
28402 The frame number, 0 being the topmost frame, i.e., the innermost function.
28404 The @code{$pc} value for that frame.
28408 File name of the source file where the function lives.
28409 @item @var{fullname}
28410 The full file name of the source file where the function lives.
28412 Line number corresponding to the @code{$pc}.
28414 The shared library where this function is defined. This is only given
28415 if the frame's function is not known.
28418 If invoked without arguments, this command prints a backtrace for the
28419 whole stack. If given two integer arguments, it shows the frames whose
28420 levels are between the two arguments (inclusive). If the two arguments
28421 are equal, it shows the single frame at the corresponding level. It is
28422 an error if @var{low-frame} is larger than the actual number of
28423 frames. On the other hand, @var{high-frame} may be larger than the
28424 actual number of frames, in which case only existing frames will be
28425 returned. If the option @code{--no-frame-filters} is supplied, then
28426 Python frame filters will not be executed.
28428 @subsubheading @value{GDBN} Command
28430 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28432 @subsubheading Example
28434 Full stack backtrace:
28440 [frame=@{level="0",addr="0x0001076c",func="foo",
28441 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28442 frame=@{level="1",addr="0x000107a4",func="foo",
28443 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28444 frame=@{level="2",addr="0x000107a4",func="foo",
28445 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28446 frame=@{level="3",addr="0x000107a4",func="foo",
28447 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28448 frame=@{level="4",addr="0x000107a4",func="foo",
28449 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28450 frame=@{level="5",addr="0x000107a4",func="foo",
28451 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28452 frame=@{level="6",addr="0x000107a4",func="foo",
28453 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28454 frame=@{level="7",addr="0x000107a4",func="foo",
28455 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28456 frame=@{level="8",addr="0x000107a4",func="foo",
28457 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28458 frame=@{level="9",addr="0x000107a4",func="foo",
28459 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28460 frame=@{level="10",addr="0x000107a4",func="foo",
28461 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28462 frame=@{level="11",addr="0x00010738",func="main",
28463 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28467 Show frames between @var{low_frame} and @var{high_frame}:
28471 -stack-list-frames 3 5
28473 [frame=@{level="3",addr="0x000107a4",func="foo",
28474 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28475 frame=@{level="4",addr="0x000107a4",func="foo",
28476 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28477 frame=@{level="5",addr="0x000107a4",func="foo",
28478 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28482 Show a single frame:
28486 -stack-list-frames 3 3
28488 [frame=@{level="3",addr="0x000107a4",func="foo",
28489 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28494 @subheading The @code{-stack-list-locals} Command
28495 @findex -stack-list-locals
28496 @anchor{-stack-list-locals}
28498 @subsubheading Synopsis
28501 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28504 Display the local variable names for the selected frame. If
28505 @var{print-values} is 0 or @code{--no-values}, print only the names of
28506 the variables; if it is 1 or @code{--all-values}, print also their
28507 values; and if it is 2 or @code{--simple-values}, print the name,
28508 type and value for simple data types, and the name and type for arrays,
28509 structures and unions. In this last case, a frontend can immediately
28510 display the value of simple data types and create variable objects for
28511 other data types when the user wishes to explore their values in
28512 more detail. If the option @code{--no-frame-filters} is supplied, then
28513 Python frame filters will not be executed.
28515 If the @code{--skip-unavailable} option is specified, local variables
28516 that are not available are not listed. Partially available local
28517 variables are still displayed, however.
28519 This command is deprecated in favor of the
28520 @samp{-stack-list-variables} command.
28522 @subsubheading @value{GDBN} Command
28524 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28526 @subsubheading Example
28530 -stack-list-locals 0
28531 ^done,locals=[name="A",name="B",name="C"]
28533 -stack-list-locals --all-values
28534 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28535 @{name="C",value="@{1, 2, 3@}"@}]
28536 -stack-list-locals --simple-values
28537 ^done,locals=[@{name="A",type="int",value="1"@},
28538 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28542 @anchor{-stack-list-variables}
28543 @subheading The @code{-stack-list-variables} Command
28544 @findex -stack-list-variables
28546 @subsubheading Synopsis
28549 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28552 Display the names of local variables and function arguments for the selected frame. If
28553 @var{print-values} is 0 or @code{--no-values}, print only the names of
28554 the variables; if it is 1 or @code{--all-values}, print also their
28555 values; and if it is 2 or @code{--simple-values}, print the name,
28556 type and value for simple data types, and the name and type for arrays,
28557 structures and unions. If the option @code{--no-frame-filters} is
28558 supplied, then Python frame filters will not be executed.
28560 If the @code{--skip-unavailable} option is specified, local variables
28561 and arguments that are not available are not listed. Partially
28562 available arguments and local variables are still displayed, however.
28564 @subsubheading Example
28568 -stack-list-variables --thread 1 --frame 0 --all-values
28569 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28574 @subheading The @code{-stack-select-frame} Command
28575 @findex -stack-select-frame
28577 @subsubheading Synopsis
28580 -stack-select-frame @var{framenum}
28583 Change the selected frame. Select a different frame @var{framenum} on
28586 This command in deprecated in favor of passing the @samp{--frame}
28587 option to every command.
28589 @subsubheading @value{GDBN} Command
28591 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28592 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28594 @subsubheading Example
28598 -stack-select-frame 2
28603 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28604 @node GDB/MI Variable Objects
28605 @section @sc{gdb/mi} Variable Objects
28609 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28611 For the implementation of a variable debugger window (locals, watched
28612 expressions, etc.), we are proposing the adaptation of the existing code
28613 used by @code{Insight}.
28615 The two main reasons for that are:
28619 It has been proven in practice (it is already on its second generation).
28622 It will shorten development time (needless to say how important it is
28626 The original interface was designed to be used by Tcl code, so it was
28627 slightly changed so it could be used through @sc{gdb/mi}. This section
28628 describes the @sc{gdb/mi} operations that will be available and gives some
28629 hints about their use.
28631 @emph{Note}: In addition to the set of operations described here, we
28632 expect the @sc{gui} implementation of a variable window to require, at
28633 least, the following operations:
28636 @item @code{-gdb-show} @code{output-radix}
28637 @item @code{-stack-list-arguments}
28638 @item @code{-stack-list-locals}
28639 @item @code{-stack-select-frame}
28644 @subheading Introduction to Variable Objects
28646 @cindex variable objects in @sc{gdb/mi}
28648 Variable objects are "object-oriented" MI interface for examining and
28649 changing values of expressions. Unlike some other MI interfaces that
28650 work with expressions, variable objects are specifically designed for
28651 simple and efficient presentation in the frontend. A variable object
28652 is identified by string name. When a variable object is created, the
28653 frontend specifies the expression for that variable object. The
28654 expression can be a simple variable, or it can be an arbitrary complex
28655 expression, and can even involve CPU registers. After creating a
28656 variable object, the frontend can invoke other variable object
28657 operations---for example to obtain or change the value of a variable
28658 object, or to change display format.
28660 Variable objects have hierarchical tree structure. Any variable object
28661 that corresponds to a composite type, such as structure in C, has
28662 a number of child variable objects, for example corresponding to each
28663 element of a structure. A child variable object can itself have
28664 children, recursively. Recursion ends when we reach
28665 leaf variable objects, which always have built-in types. Child variable
28666 objects are created only by explicit request, so if a frontend
28667 is not interested in the children of a particular variable object, no
28668 child will be created.
28670 For a leaf variable object it is possible to obtain its value as a
28671 string, or set the value from a string. String value can be also
28672 obtained for a non-leaf variable object, but it's generally a string
28673 that only indicates the type of the object, and does not list its
28674 contents. Assignment to a non-leaf variable object is not allowed.
28676 A frontend does not need to read the values of all variable objects each time
28677 the program stops. Instead, MI provides an update command that lists all
28678 variable objects whose values has changed since the last update
28679 operation. This considerably reduces the amount of data that must
28680 be transferred to the frontend. As noted above, children variable
28681 objects are created on demand, and only leaf variable objects have a
28682 real value. As result, gdb will read target memory only for leaf
28683 variables that frontend has created.
28685 The automatic update is not always desirable. For example, a frontend
28686 might want to keep a value of some expression for future reference,
28687 and never update it. For another example, fetching memory is
28688 relatively slow for embedded targets, so a frontend might want
28689 to disable automatic update for the variables that are either not
28690 visible on the screen, or ``closed''. This is possible using so
28691 called ``frozen variable objects''. Such variable objects are never
28692 implicitly updated.
28694 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28695 fixed variable object, the expression is parsed when the variable
28696 object is created, including associating identifiers to specific
28697 variables. The meaning of expression never changes. For a floating
28698 variable object the values of variables whose names appear in the
28699 expressions are re-evaluated every time in the context of the current
28700 frame. Consider this example:
28705 struct work_state state;
28712 If a fixed variable object for the @code{state} variable is created in
28713 this function, and we enter the recursive call, the variable
28714 object will report the value of @code{state} in the top-level
28715 @code{do_work} invocation. On the other hand, a floating variable
28716 object will report the value of @code{state} in the current frame.
28718 If an expression specified when creating a fixed variable object
28719 refers to a local variable, the variable object becomes bound to the
28720 thread and frame in which the variable object is created. When such
28721 variable object is updated, @value{GDBN} makes sure that the
28722 thread/frame combination the variable object is bound to still exists,
28723 and re-evaluates the variable object in context of that thread/frame.
28725 The following is the complete set of @sc{gdb/mi} operations defined to
28726 access this functionality:
28728 @multitable @columnfractions .4 .6
28729 @item @strong{Operation}
28730 @tab @strong{Description}
28732 @item @code{-enable-pretty-printing}
28733 @tab enable Python-based pretty-printing
28734 @item @code{-var-create}
28735 @tab create a variable object
28736 @item @code{-var-delete}
28737 @tab delete the variable object and/or its children
28738 @item @code{-var-set-format}
28739 @tab set the display format of this variable
28740 @item @code{-var-show-format}
28741 @tab show the display format of this variable
28742 @item @code{-var-info-num-children}
28743 @tab tells how many children this object has
28744 @item @code{-var-list-children}
28745 @tab return a list of the object's children
28746 @item @code{-var-info-type}
28747 @tab show the type of this variable object
28748 @item @code{-var-info-expression}
28749 @tab print parent-relative expression that this variable object represents
28750 @item @code{-var-info-path-expression}
28751 @tab print full expression that this variable object represents
28752 @item @code{-var-show-attributes}
28753 @tab is this variable editable? does it exist here?
28754 @item @code{-var-evaluate-expression}
28755 @tab get the value of this variable
28756 @item @code{-var-assign}
28757 @tab set the value of this variable
28758 @item @code{-var-update}
28759 @tab update the variable and its children
28760 @item @code{-var-set-frozen}
28761 @tab set frozeness attribute
28762 @item @code{-var-set-update-range}
28763 @tab set range of children to display on update
28766 In the next subsection we describe each operation in detail and suggest
28767 how it can be used.
28769 @subheading Description And Use of Operations on Variable Objects
28771 @subheading The @code{-enable-pretty-printing} Command
28772 @findex -enable-pretty-printing
28775 -enable-pretty-printing
28778 @value{GDBN} allows Python-based visualizers to affect the output of the
28779 MI variable object commands. However, because there was no way to
28780 implement this in a fully backward-compatible way, a front end must
28781 request that this functionality be enabled.
28783 Once enabled, this feature cannot be disabled.
28785 Note that if Python support has not been compiled into @value{GDBN},
28786 this command will still succeed (and do nothing).
28788 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28789 may work differently in future versions of @value{GDBN}.
28791 @subheading The @code{-var-create} Command
28792 @findex -var-create
28794 @subsubheading Synopsis
28797 -var-create @{@var{name} | "-"@}
28798 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28801 This operation creates a variable object, which allows the monitoring of
28802 a variable, the result of an expression, a memory cell or a CPU
28805 The @var{name} parameter is the string by which the object can be
28806 referenced. It must be unique. If @samp{-} is specified, the varobj
28807 system will generate a string ``varNNNNNN'' automatically. It will be
28808 unique provided that one does not specify @var{name} of that format.
28809 The command fails if a duplicate name is found.
28811 The frame under which the expression should be evaluated can be
28812 specified by @var{frame-addr}. A @samp{*} indicates that the current
28813 frame should be used. A @samp{@@} indicates that a floating variable
28814 object must be created.
28816 @var{expression} is any expression valid on the current language set (must not
28817 begin with a @samp{*}), or one of the following:
28821 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28824 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28827 @samp{$@var{regname}} --- a CPU register name
28830 @cindex dynamic varobj
28831 A varobj's contents may be provided by a Python-based pretty-printer. In this
28832 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28833 have slightly different semantics in some cases. If the
28834 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28835 will never create a dynamic varobj. This ensures backward
28836 compatibility for existing clients.
28838 @subsubheading Result
28840 This operation returns attributes of the newly-created varobj. These
28845 The name of the varobj.
28848 The number of children of the varobj. This number is not necessarily
28849 reliable for a dynamic varobj. Instead, you must examine the
28850 @samp{has_more} attribute.
28853 The varobj's scalar value. For a varobj whose type is some sort of
28854 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28855 will not be interesting.
28858 The varobj's type. This is a string representation of the type, as
28859 would be printed by the @value{GDBN} CLI. If @samp{print object}
28860 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28861 @emph{actual} (derived) type of the object is shown rather than the
28862 @emph{declared} one.
28865 If a variable object is bound to a specific thread, then this is the
28866 thread's identifier.
28869 For a dynamic varobj, this indicates whether there appear to be any
28870 children available. For a non-dynamic varobj, this will be 0.
28873 This attribute will be present and have the value @samp{1} if the
28874 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28875 then this attribute will not be present.
28878 A dynamic varobj can supply a display hint to the front end. The
28879 value comes directly from the Python pretty-printer object's
28880 @code{display_hint} method. @xref{Pretty Printing API}.
28883 Typical output will look like this:
28886 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28887 has_more="@var{has_more}"
28891 @subheading The @code{-var-delete} Command
28892 @findex -var-delete
28894 @subsubheading Synopsis
28897 -var-delete [ -c ] @var{name}
28900 Deletes a previously created variable object and all of its children.
28901 With the @samp{-c} option, just deletes the children.
28903 Returns an error if the object @var{name} is not found.
28906 @subheading The @code{-var-set-format} Command
28907 @findex -var-set-format
28909 @subsubheading Synopsis
28912 -var-set-format @var{name} @var{format-spec}
28915 Sets the output format for the value of the object @var{name} to be
28918 @anchor{-var-set-format}
28919 The syntax for the @var{format-spec} is as follows:
28922 @var{format-spec} @expansion{}
28923 @{binary | decimal | hexadecimal | octal | natural@}
28926 The natural format is the default format choosen automatically
28927 based on the variable type (like decimal for an @code{int}, hex
28928 for pointers, etc.).
28930 For a variable with children, the format is set only on the
28931 variable itself, and the children are not affected.
28933 @subheading The @code{-var-show-format} Command
28934 @findex -var-show-format
28936 @subsubheading Synopsis
28939 -var-show-format @var{name}
28942 Returns the format used to display the value of the object @var{name}.
28945 @var{format} @expansion{}
28950 @subheading The @code{-var-info-num-children} Command
28951 @findex -var-info-num-children
28953 @subsubheading Synopsis
28956 -var-info-num-children @var{name}
28959 Returns the number of children of a variable object @var{name}:
28965 Note that this number is not completely reliable for a dynamic varobj.
28966 It will return the current number of children, but more children may
28970 @subheading The @code{-var-list-children} Command
28971 @findex -var-list-children
28973 @subsubheading Synopsis
28976 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28978 @anchor{-var-list-children}
28980 Return a list of the children of the specified variable object and
28981 create variable objects for them, if they do not already exist. With
28982 a single argument or if @var{print-values} has a value of 0 or
28983 @code{--no-values}, print only the names of the variables; if
28984 @var{print-values} is 1 or @code{--all-values}, also print their
28985 values; and if it is 2 or @code{--simple-values} print the name and
28986 value for simple data types and just the name for arrays, structures
28989 @var{from} and @var{to}, if specified, indicate the range of children
28990 to report. If @var{from} or @var{to} is less than zero, the range is
28991 reset and all children will be reported. Otherwise, children starting
28992 at @var{from} (zero-based) and up to and excluding @var{to} will be
28995 If a child range is requested, it will only affect the current call to
28996 @code{-var-list-children}, but not future calls to @code{-var-update}.
28997 For this, you must instead use @code{-var-set-update-range}. The
28998 intent of this approach is to enable a front end to implement any
28999 update approach it likes; for example, scrolling a view may cause the
29000 front end to request more children with @code{-var-list-children}, and
29001 then the front end could call @code{-var-set-update-range} with a
29002 different range to ensure that future updates are restricted to just
29005 For each child the following results are returned:
29010 Name of the variable object created for this child.
29013 The expression to be shown to the user by the front end to designate this child.
29014 For example this may be the name of a structure member.
29016 For a dynamic varobj, this value cannot be used to form an
29017 expression. There is no way to do this at all with a dynamic varobj.
29019 For C/C@t{++} structures there are several pseudo children returned to
29020 designate access qualifiers. For these pseudo children @var{exp} is
29021 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29022 type and value are not present.
29024 A dynamic varobj will not report the access qualifying
29025 pseudo-children, regardless of the language. This information is not
29026 available at all with a dynamic varobj.
29029 Number of children this child has. For a dynamic varobj, this will be
29033 The type of the child. If @samp{print object}
29034 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29035 @emph{actual} (derived) type of the object is shown rather than the
29036 @emph{declared} one.
29039 If values were requested, this is the value.
29042 If this variable object is associated with a thread, this is the thread id.
29043 Otherwise this result is not present.
29046 If the variable object is frozen, this variable will be present with a value of 1.
29049 A dynamic varobj can supply a display hint to the front end. The
29050 value comes directly from the Python pretty-printer object's
29051 @code{display_hint} method. @xref{Pretty Printing API}.
29054 This attribute will be present and have the value @samp{1} if the
29055 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29056 then this attribute will not be present.
29060 The result may have its own attributes:
29064 A dynamic varobj can supply a display hint to the front end. The
29065 value comes directly from the Python pretty-printer object's
29066 @code{display_hint} method. @xref{Pretty Printing API}.
29069 This is an integer attribute which is nonzero if there are children
29070 remaining after the end of the selected range.
29073 @subsubheading Example
29077 -var-list-children n
29078 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29079 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29081 -var-list-children --all-values n
29082 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29083 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29087 @subheading The @code{-var-info-type} Command
29088 @findex -var-info-type
29090 @subsubheading Synopsis
29093 -var-info-type @var{name}
29096 Returns the type of the specified variable @var{name}. The type is
29097 returned as a string in the same format as it is output by the
29101 type=@var{typename}
29105 @subheading The @code{-var-info-expression} Command
29106 @findex -var-info-expression
29108 @subsubheading Synopsis
29111 -var-info-expression @var{name}
29114 Returns a string that is suitable for presenting this
29115 variable object in user interface. The string is generally
29116 not valid expression in the current language, and cannot be evaluated.
29118 For example, if @code{a} is an array, and variable object
29119 @code{A} was created for @code{a}, then we'll get this output:
29122 (gdb) -var-info-expression A.1
29123 ^done,lang="C",exp="1"
29127 Here, the value of @code{lang} is the language name, which can be
29128 found in @ref{Supported Languages}.
29130 Note that the output of the @code{-var-list-children} command also
29131 includes those expressions, so the @code{-var-info-expression} command
29134 @subheading The @code{-var-info-path-expression} Command
29135 @findex -var-info-path-expression
29137 @subsubheading Synopsis
29140 -var-info-path-expression @var{name}
29143 Returns an expression that can be evaluated in the current
29144 context and will yield the same value that a variable object has.
29145 Compare this with the @code{-var-info-expression} command, which
29146 result can be used only for UI presentation. Typical use of
29147 the @code{-var-info-path-expression} command is creating a
29148 watchpoint from a variable object.
29150 This command is currently not valid for children of a dynamic varobj,
29151 and will give an error when invoked on one.
29153 For example, suppose @code{C} is a C@t{++} class, derived from class
29154 @code{Base}, and that the @code{Base} class has a member called
29155 @code{m_size}. Assume a variable @code{c} is has the type of
29156 @code{C} and a variable object @code{C} was created for variable
29157 @code{c}. Then, we'll get this output:
29159 (gdb) -var-info-path-expression C.Base.public.m_size
29160 ^done,path_expr=((Base)c).m_size)
29163 @subheading The @code{-var-show-attributes} Command
29164 @findex -var-show-attributes
29166 @subsubheading Synopsis
29169 -var-show-attributes @var{name}
29172 List attributes of the specified variable object @var{name}:
29175 status=@var{attr} [ ( ,@var{attr} )* ]
29179 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29181 @subheading The @code{-var-evaluate-expression} Command
29182 @findex -var-evaluate-expression
29184 @subsubheading Synopsis
29187 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29190 Evaluates the expression that is represented by the specified variable
29191 object and returns its value as a string. The format of the string
29192 can be specified with the @samp{-f} option. The possible values of
29193 this option are the same as for @code{-var-set-format}
29194 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29195 the current display format will be used. The current display format
29196 can be changed using the @code{-var-set-format} command.
29202 Note that one must invoke @code{-var-list-children} for a variable
29203 before the value of a child variable can be evaluated.
29205 @subheading The @code{-var-assign} Command
29206 @findex -var-assign
29208 @subsubheading Synopsis
29211 -var-assign @var{name} @var{expression}
29214 Assigns the value of @var{expression} to the variable object specified
29215 by @var{name}. The object must be @samp{editable}. If the variable's
29216 value is altered by the assign, the variable will show up in any
29217 subsequent @code{-var-update} list.
29219 @subsubheading Example
29227 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29231 @subheading The @code{-var-update} Command
29232 @findex -var-update
29234 @subsubheading Synopsis
29237 -var-update [@var{print-values}] @{@var{name} | "*"@}
29240 Reevaluate the expressions corresponding to the variable object
29241 @var{name} and all its direct and indirect children, and return the
29242 list of variable objects whose values have changed; @var{name} must
29243 be a root variable object. Here, ``changed'' means that the result of
29244 @code{-var-evaluate-expression} before and after the
29245 @code{-var-update} is different. If @samp{*} is used as the variable
29246 object names, all existing variable objects are updated, except
29247 for frozen ones (@pxref{-var-set-frozen}). The option
29248 @var{print-values} determines whether both names and values, or just
29249 names are printed. The possible values of this option are the same
29250 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29251 recommended to use the @samp{--all-values} option, to reduce the
29252 number of MI commands needed on each program stop.
29254 With the @samp{*} parameter, if a variable object is bound to a
29255 currently running thread, it will not be updated, without any
29258 If @code{-var-set-update-range} was previously used on a varobj, then
29259 only the selected range of children will be reported.
29261 @code{-var-update} reports all the changed varobjs in a tuple named
29264 Each item in the change list is itself a tuple holding:
29268 The name of the varobj.
29271 If values were requested for this update, then this field will be
29272 present and will hold the value of the varobj.
29275 @anchor{-var-update}
29276 This field is a string which may take one of three values:
29280 The variable object's current value is valid.
29283 The variable object does not currently hold a valid value but it may
29284 hold one in the future if its associated expression comes back into
29288 The variable object no longer holds a valid value.
29289 This can occur when the executable file being debugged has changed,
29290 either through recompilation or by using the @value{GDBN} @code{file}
29291 command. The front end should normally choose to delete these variable
29295 In the future new values may be added to this list so the front should
29296 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29299 This is only present if the varobj is still valid. If the type
29300 changed, then this will be the string @samp{true}; otherwise it will
29303 When a varobj's type changes, its children are also likely to have
29304 become incorrect. Therefore, the varobj's children are automatically
29305 deleted when this attribute is @samp{true}. Also, the varobj's update
29306 range, when set using the @code{-var-set-update-range} command, is
29310 If the varobj's type changed, then this field will be present and will
29313 @item new_num_children
29314 For a dynamic varobj, if the number of children changed, or if the
29315 type changed, this will be the new number of children.
29317 The @samp{numchild} field in other varobj responses is generally not
29318 valid for a dynamic varobj -- it will show the number of children that
29319 @value{GDBN} knows about, but because dynamic varobjs lazily
29320 instantiate their children, this will not reflect the number of
29321 children which may be available.
29323 The @samp{new_num_children} attribute only reports changes to the
29324 number of children known by @value{GDBN}. This is the only way to
29325 detect whether an update has removed children (which necessarily can
29326 only happen at the end of the update range).
29329 The display hint, if any.
29332 This is an integer value, which will be 1 if there are more children
29333 available outside the varobj's update range.
29336 This attribute will be present and have the value @samp{1} if the
29337 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29338 then this attribute will not be present.
29341 If new children were added to a dynamic varobj within the selected
29342 update range (as set by @code{-var-set-update-range}), then they will
29343 be listed in this attribute.
29346 @subsubheading Example
29353 -var-update --all-values var1
29354 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29355 type_changed="false"@}]
29359 @subheading The @code{-var-set-frozen} Command
29360 @findex -var-set-frozen
29361 @anchor{-var-set-frozen}
29363 @subsubheading Synopsis
29366 -var-set-frozen @var{name} @var{flag}
29369 Set the frozenness flag on the variable object @var{name}. The
29370 @var{flag} parameter should be either @samp{1} to make the variable
29371 frozen or @samp{0} to make it unfrozen. If a variable object is
29372 frozen, then neither itself, nor any of its children, are
29373 implicitly updated by @code{-var-update} of
29374 a parent variable or by @code{-var-update *}. Only
29375 @code{-var-update} of the variable itself will update its value and
29376 values of its children. After a variable object is unfrozen, it is
29377 implicitly updated by all subsequent @code{-var-update} operations.
29378 Unfreezing a variable does not update it, only subsequent
29379 @code{-var-update} does.
29381 @subsubheading Example
29385 -var-set-frozen V 1
29390 @subheading The @code{-var-set-update-range} command
29391 @findex -var-set-update-range
29392 @anchor{-var-set-update-range}
29394 @subsubheading Synopsis
29397 -var-set-update-range @var{name} @var{from} @var{to}
29400 Set the range of children to be returned by future invocations of
29401 @code{-var-update}.
29403 @var{from} and @var{to} indicate the range of children to report. If
29404 @var{from} or @var{to} is less than zero, the range is reset and all
29405 children will be reported. Otherwise, children starting at @var{from}
29406 (zero-based) and up to and excluding @var{to} will be reported.
29408 @subsubheading Example
29412 -var-set-update-range V 1 2
29416 @subheading The @code{-var-set-visualizer} command
29417 @findex -var-set-visualizer
29418 @anchor{-var-set-visualizer}
29420 @subsubheading Synopsis
29423 -var-set-visualizer @var{name} @var{visualizer}
29426 Set a visualizer for the variable object @var{name}.
29428 @var{visualizer} is the visualizer to use. The special value
29429 @samp{None} means to disable any visualizer in use.
29431 If not @samp{None}, @var{visualizer} must be a Python expression.
29432 This expression must evaluate to a callable object which accepts a
29433 single argument. @value{GDBN} will call this object with the value of
29434 the varobj @var{name} as an argument (this is done so that the same
29435 Python pretty-printing code can be used for both the CLI and MI).
29436 When called, this object must return an object which conforms to the
29437 pretty-printing interface (@pxref{Pretty Printing API}).
29439 The pre-defined function @code{gdb.default_visualizer} may be used to
29440 select a visualizer by following the built-in process
29441 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29442 a varobj is created, and so ordinarily is not needed.
29444 This feature is only available if Python support is enabled. The MI
29445 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29446 can be used to check this.
29448 @subsubheading Example
29450 Resetting the visualizer:
29454 -var-set-visualizer V None
29458 Reselecting the default (type-based) visualizer:
29462 -var-set-visualizer V gdb.default_visualizer
29466 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29467 can be used to instantiate this class for a varobj:
29471 -var-set-visualizer V "lambda val: SomeClass()"
29475 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29476 @node GDB/MI Data Manipulation
29477 @section @sc{gdb/mi} Data Manipulation
29479 @cindex data manipulation, in @sc{gdb/mi}
29480 @cindex @sc{gdb/mi}, data manipulation
29481 This section describes the @sc{gdb/mi} commands that manipulate data:
29482 examine memory and registers, evaluate expressions, etc.
29484 For details about what an addressable memory unit is,
29485 @pxref{addressable memory unit}.
29487 @c REMOVED FROM THE INTERFACE.
29488 @c @subheading -data-assign
29489 @c Change the value of a program variable. Plenty of side effects.
29490 @c @subsubheading GDB Command
29492 @c @subsubheading Example
29495 @subheading The @code{-data-disassemble} Command
29496 @findex -data-disassemble
29498 @subsubheading Synopsis
29502 [ -s @var{start-addr} -e @var{end-addr} ]
29503 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29511 @item @var{start-addr}
29512 is the beginning address (or @code{$pc})
29513 @item @var{end-addr}
29515 @item @var{filename}
29516 is the name of the file to disassemble
29517 @item @var{linenum}
29518 is the line number to disassemble around
29520 is the number of disassembly lines to be produced. If it is -1,
29521 the whole function will be disassembled, in case no @var{end-addr} is
29522 specified. If @var{end-addr} is specified as a non-zero value, and
29523 @var{lines} is lower than the number of disassembly lines between
29524 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29525 displayed; if @var{lines} is higher than the number of lines between
29526 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29531 @item 0 disassembly only
29532 @item 1 mixed source and disassembly (deprecated)
29533 @item 2 disassembly with raw opcodes
29534 @item 3 mixed source and disassembly with raw opcodes (deprecated)
29535 @item 4 mixed source and disassembly
29536 @item 5 mixed source and disassembly with raw opcodes
29539 Modes 1 and 3 are deprecated. The output is ``source centric''
29540 which hasn't proved useful in practice.
29541 @xref{Machine Code}, for a discussion of the difference between
29542 @code{/m} and @code{/s} output of the @code{disassemble} command.
29545 @subsubheading Result
29547 The result of the @code{-data-disassemble} command will be a list named
29548 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29549 used with the @code{-data-disassemble} command.
29551 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29556 The address at which this instruction was disassembled.
29559 The name of the function this instruction is within.
29562 The decimal offset in bytes from the start of @samp{func-name}.
29565 The text disassembly for this @samp{address}.
29568 This field is only present for modes 2, 3 and 5. This contains the raw opcode
29569 bytes for the @samp{inst} field.
29573 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
29574 @samp{src_and_asm_line}, each of which has the following fields:
29578 The line number within @samp{file}.
29581 The file name from the compilation unit. This might be an absolute
29582 file name or a relative file name depending on the compile command
29586 Absolute file name of @samp{file}. It is converted to a canonical form
29587 using the source file search path
29588 (@pxref{Source Path, ,Specifying Source Directories})
29589 and after resolving all the symbolic links.
29591 If the source file is not found this field will contain the path as
29592 present in the debug information.
29594 @item line_asm_insn
29595 This is a list of tuples containing the disassembly for @samp{line} in
29596 @samp{file}. The fields of each tuple are the same as for
29597 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29598 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29603 Note that whatever included in the @samp{inst} field, is not
29604 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29607 @subsubheading @value{GDBN} Command
29609 The corresponding @value{GDBN} command is @samp{disassemble}.
29611 @subsubheading Example
29613 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29617 -data-disassemble -s $pc -e "$pc + 20" -- 0
29620 @{address="0x000107c0",func-name="main",offset="4",
29621 inst="mov 2, %o0"@},
29622 @{address="0x000107c4",func-name="main",offset="8",
29623 inst="sethi %hi(0x11800), %o2"@},
29624 @{address="0x000107c8",func-name="main",offset="12",
29625 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29626 @{address="0x000107cc",func-name="main",offset="16",
29627 inst="sethi %hi(0x11800), %o2"@},
29628 @{address="0x000107d0",func-name="main",offset="20",
29629 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29633 Disassemble the whole @code{main} function. Line 32 is part of
29637 -data-disassemble -f basics.c -l 32 -- 0
29639 @{address="0x000107bc",func-name="main",offset="0",
29640 inst="save %sp, -112, %sp"@},
29641 @{address="0x000107c0",func-name="main",offset="4",
29642 inst="mov 2, %o0"@},
29643 @{address="0x000107c4",func-name="main",offset="8",
29644 inst="sethi %hi(0x11800), %o2"@},
29646 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29647 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29651 Disassemble 3 instructions from the start of @code{main}:
29655 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29657 @{address="0x000107bc",func-name="main",offset="0",
29658 inst="save %sp, -112, %sp"@},
29659 @{address="0x000107c0",func-name="main",offset="4",
29660 inst="mov 2, %o0"@},
29661 @{address="0x000107c4",func-name="main",offset="8",
29662 inst="sethi %hi(0x11800), %o2"@}]
29666 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29670 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29672 src_and_asm_line=@{line="31",
29673 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29674 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29675 line_asm_insn=[@{address="0x000107bc",
29676 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29677 src_and_asm_line=@{line="32",
29678 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29679 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29680 line_asm_insn=[@{address="0x000107c0",
29681 func-name="main",offset="4",inst="mov 2, %o0"@},
29682 @{address="0x000107c4",func-name="main",offset="8",
29683 inst="sethi %hi(0x11800), %o2"@}]@}]
29688 @subheading The @code{-data-evaluate-expression} Command
29689 @findex -data-evaluate-expression
29691 @subsubheading Synopsis
29694 -data-evaluate-expression @var{expr}
29697 Evaluate @var{expr} as an expression. The expression could contain an
29698 inferior function call. The function call will execute synchronously.
29699 If the expression contains spaces, it must be enclosed in double quotes.
29701 @subsubheading @value{GDBN} Command
29703 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29704 @samp{call}. In @code{gdbtk} only, there's a corresponding
29705 @samp{gdb_eval} command.
29707 @subsubheading Example
29709 In the following example, the numbers that precede the commands are the
29710 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29711 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29715 211-data-evaluate-expression A
29718 311-data-evaluate-expression &A
29719 311^done,value="0xefffeb7c"
29721 411-data-evaluate-expression A+3
29724 511-data-evaluate-expression "A + 3"
29730 @subheading The @code{-data-list-changed-registers} Command
29731 @findex -data-list-changed-registers
29733 @subsubheading Synopsis
29736 -data-list-changed-registers
29739 Display a list of the registers that have changed.
29741 @subsubheading @value{GDBN} Command
29743 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29744 has the corresponding command @samp{gdb_changed_register_list}.
29746 @subsubheading Example
29748 On a PPC MBX board:
29756 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29757 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29760 -data-list-changed-registers
29761 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29762 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29763 "24","25","26","27","28","30","31","64","65","66","67","69"]
29768 @subheading The @code{-data-list-register-names} Command
29769 @findex -data-list-register-names
29771 @subsubheading Synopsis
29774 -data-list-register-names [ ( @var{regno} )+ ]
29777 Show a list of register names for the current target. If no arguments
29778 are given, it shows a list of the names of all the registers. If
29779 integer numbers are given as arguments, it will print a list of the
29780 names of the registers corresponding to the arguments. To ensure
29781 consistency between a register name and its number, the output list may
29782 include empty register names.
29784 @subsubheading @value{GDBN} Command
29786 @value{GDBN} does not have a command which corresponds to
29787 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29788 corresponding command @samp{gdb_regnames}.
29790 @subsubheading Example
29792 For the PPC MBX board:
29795 -data-list-register-names
29796 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29797 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29798 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29799 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29800 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29801 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29802 "", "pc","ps","cr","lr","ctr","xer"]
29804 -data-list-register-names 1 2 3
29805 ^done,register-names=["r1","r2","r3"]
29809 @subheading The @code{-data-list-register-values} Command
29810 @findex -data-list-register-values
29812 @subsubheading Synopsis
29815 -data-list-register-values
29816 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29819 Display the registers' contents. The format according to which the
29820 registers' contents are to be returned is given by @var{fmt}, followed
29821 by an optional list of numbers specifying the registers to display. A
29822 missing list of numbers indicates that the contents of all the
29823 registers must be returned. The @code{--skip-unavailable} option
29824 indicates that only the available registers are to be returned.
29826 Allowed formats for @var{fmt} are:
29843 @subsubheading @value{GDBN} Command
29845 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29846 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29848 @subsubheading Example
29850 For a PPC MBX board (note: line breaks are for readability only, they
29851 don't appear in the actual output):
29855 -data-list-register-values r 64 65
29856 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29857 @{number="65",value="0x00029002"@}]
29859 -data-list-register-values x
29860 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29861 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29862 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29863 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29864 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29865 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29866 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29867 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29868 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29869 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29870 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29871 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29872 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29873 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29874 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29875 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29876 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29877 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29878 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29879 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29880 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29881 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29882 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29883 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29884 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29885 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29886 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29887 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29888 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29889 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29890 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29891 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29892 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29893 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29894 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29895 @{number="69",value="0x20002b03"@}]
29900 @subheading The @code{-data-read-memory} Command
29901 @findex -data-read-memory
29903 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29905 @subsubheading Synopsis
29908 -data-read-memory [ -o @var{byte-offset} ]
29909 @var{address} @var{word-format} @var{word-size}
29910 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29917 @item @var{address}
29918 An expression specifying the address of the first memory word to be
29919 read. Complex expressions containing embedded white space should be
29920 quoted using the C convention.
29922 @item @var{word-format}
29923 The format to be used to print the memory words. The notation is the
29924 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29927 @item @var{word-size}
29928 The size of each memory word in bytes.
29930 @item @var{nr-rows}
29931 The number of rows in the output table.
29933 @item @var{nr-cols}
29934 The number of columns in the output table.
29937 If present, indicates that each row should include an @sc{ascii} dump. The
29938 value of @var{aschar} is used as a padding character when a byte is not a
29939 member of the printable @sc{ascii} character set (printable @sc{ascii}
29940 characters are those whose code is between 32 and 126, inclusively).
29942 @item @var{byte-offset}
29943 An offset to add to the @var{address} before fetching memory.
29946 This command displays memory contents as a table of @var{nr-rows} by
29947 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29948 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29949 (returned as @samp{total-bytes}). Should less than the requested number
29950 of bytes be returned by the target, the missing words are identified
29951 using @samp{N/A}. The number of bytes read from the target is returned
29952 in @samp{nr-bytes} and the starting address used to read memory in
29955 The address of the next/previous row or page is available in
29956 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29959 @subsubheading @value{GDBN} Command
29961 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29962 @samp{gdb_get_mem} memory read command.
29964 @subsubheading Example
29966 Read six bytes of memory starting at @code{bytes+6} but then offset by
29967 @code{-6} bytes. Format as three rows of two columns. One byte per
29968 word. Display each word in hex.
29972 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29973 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29974 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29975 prev-page="0x0000138a",memory=[
29976 @{addr="0x00001390",data=["0x00","0x01"]@},
29977 @{addr="0x00001392",data=["0x02","0x03"]@},
29978 @{addr="0x00001394",data=["0x04","0x05"]@}]
29982 Read two bytes of memory starting at address @code{shorts + 64} and
29983 display as a single word formatted in decimal.
29987 5-data-read-memory shorts+64 d 2 1 1
29988 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29989 next-row="0x00001512",prev-row="0x0000150e",
29990 next-page="0x00001512",prev-page="0x0000150e",memory=[
29991 @{addr="0x00001510",data=["128"]@}]
29995 Read thirty two bytes of memory starting at @code{bytes+16} and format
29996 as eight rows of four columns. Include a string encoding with @samp{x}
29997 used as the non-printable character.
30001 4-data-read-memory bytes+16 x 1 8 4 x
30002 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30003 next-row="0x000013c0",prev-row="0x0000139c",
30004 next-page="0x000013c0",prev-page="0x00001380",memory=[
30005 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30006 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30007 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30008 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30009 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30010 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30011 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30012 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30016 @subheading The @code{-data-read-memory-bytes} Command
30017 @findex -data-read-memory-bytes
30019 @subsubheading Synopsis
30022 -data-read-memory-bytes [ -o @var{offset} ]
30023 @var{address} @var{count}
30030 @item @var{address}
30031 An expression specifying the address of the first addressable memory unit
30032 to be read. Complex expressions containing embedded white space should be
30033 quoted using the C convention.
30036 The number of addressable memory units to read. This should be an integer
30040 The offset relative to @var{address} at which to start reading. This
30041 should be an integer literal. This option is provided so that a frontend
30042 is not required to first evaluate address and then perform address
30043 arithmetics itself.
30047 This command attempts to read all accessible memory regions in the
30048 specified range. First, all regions marked as unreadable in the memory
30049 map (if one is defined) will be skipped. @xref{Memory Region
30050 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30051 regions. For each one, if reading full region results in an errors,
30052 @value{GDBN} will try to read a subset of the region.
30054 In general, every single memory unit in the region may be readable or not,
30055 and the only way to read every readable unit is to try a read at
30056 every address, which is not practical. Therefore, @value{GDBN} will
30057 attempt to read all accessible memory units at either beginning or the end
30058 of the region, using a binary division scheme. This heuristic works
30059 well for reading accross a memory map boundary. Note that if a region
30060 has a readable range that is neither at the beginning or the end,
30061 @value{GDBN} will not read it.
30063 The result record (@pxref{GDB/MI Result Records}) that is output of
30064 the command includes a field named @samp{memory} whose content is a
30065 list of tuples. Each tuple represent a successfully read memory block
30066 and has the following fields:
30070 The start address of the memory block, as hexadecimal literal.
30073 The end address of the memory block, as hexadecimal literal.
30076 The offset of the memory block, as hexadecimal literal, relative to
30077 the start address passed to @code{-data-read-memory-bytes}.
30080 The contents of the memory block, in hex.
30086 @subsubheading @value{GDBN} Command
30088 The corresponding @value{GDBN} command is @samp{x}.
30090 @subsubheading Example
30094 -data-read-memory-bytes &a 10
30095 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30097 contents="01000000020000000300"@}]
30102 @subheading The @code{-data-write-memory-bytes} Command
30103 @findex -data-write-memory-bytes
30105 @subsubheading Synopsis
30108 -data-write-memory-bytes @var{address} @var{contents}
30109 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30116 @item @var{address}
30117 An expression specifying the address of the first addressable memory unit
30118 to be written. Complex expressions containing embedded white space should
30119 be quoted using the C convention.
30121 @item @var{contents}
30122 The hex-encoded data to write. It is an error if @var{contents} does
30123 not represent an integral number of addressable memory units.
30126 Optional argument indicating the number of addressable memory units to be
30127 written. If @var{count} is greater than @var{contents}' length,
30128 @value{GDBN} will repeatedly write @var{contents} until it fills
30129 @var{count} memory units.
30133 @subsubheading @value{GDBN} Command
30135 There's no corresponding @value{GDBN} command.
30137 @subsubheading Example
30141 -data-write-memory-bytes &a "aabbccdd"
30148 -data-write-memory-bytes &a "aabbccdd" 16e
30153 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30154 @node GDB/MI Tracepoint Commands
30155 @section @sc{gdb/mi} Tracepoint Commands
30157 The commands defined in this section implement MI support for
30158 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30160 @subheading The @code{-trace-find} Command
30161 @findex -trace-find
30163 @subsubheading Synopsis
30166 -trace-find @var{mode} [@var{parameters}@dots{}]
30169 Find a trace frame using criteria defined by @var{mode} and
30170 @var{parameters}. The following table lists permissible
30171 modes and their parameters. For details of operation, see @ref{tfind}.
30176 No parameters are required. Stops examining trace frames.
30179 An integer is required as parameter. Selects tracepoint frame with
30182 @item tracepoint-number
30183 An integer is required as parameter. Finds next
30184 trace frame that corresponds to tracepoint with the specified number.
30187 An address is required as parameter. Finds
30188 next trace frame that corresponds to any tracepoint at the specified
30191 @item pc-inside-range
30192 Two addresses are required as parameters. Finds next trace
30193 frame that corresponds to a tracepoint at an address inside the
30194 specified range. Both bounds are considered to be inside the range.
30196 @item pc-outside-range
30197 Two addresses are required as parameters. Finds
30198 next trace frame that corresponds to a tracepoint at an address outside
30199 the specified range. Both bounds are considered to be inside the range.
30202 Line specification is required as parameter. @xref{Specify Location}.
30203 Finds next trace frame that corresponds to a tracepoint at
30204 the specified location.
30208 If @samp{none} was passed as @var{mode}, the response does not
30209 have fields. Otherwise, the response may have the following fields:
30213 This field has either @samp{0} or @samp{1} as the value, depending
30214 on whether a matching tracepoint was found.
30217 The index of the found traceframe. This field is present iff
30218 the @samp{found} field has value of @samp{1}.
30221 The index of the found tracepoint. This field is present iff
30222 the @samp{found} field has value of @samp{1}.
30225 The information about the frame corresponding to the found trace
30226 frame. This field is present only if a trace frame was found.
30227 @xref{GDB/MI Frame Information}, for description of this field.
30231 @subsubheading @value{GDBN} Command
30233 The corresponding @value{GDBN} command is @samp{tfind}.
30235 @subheading -trace-define-variable
30236 @findex -trace-define-variable
30238 @subsubheading Synopsis
30241 -trace-define-variable @var{name} [ @var{value} ]
30244 Create trace variable @var{name} if it does not exist. If
30245 @var{value} is specified, sets the initial value of the specified
30246 trace variable to that value. Note that the @var{name} should start
30247 with the @samp{$} character.
30249 @subsubheading @value{GDBN} Command
30251 The corresponding @value{GDBN} command is @samp{tvariable}.
30253 @subheading The @code{-trace-frame-collected} Command
30254 @findex -trace-frame-collected
30256 @subsubheading Synopsis
30259 -trace-frame-collected
30260 [--var-print-values @var{var_pval}]
30261 [--comp-print-values @var{comp_pval}]
30262 [--registers-format @var{regformat}]
30263 [--memory-contents]
30266 This command returns the set of collected objects, register names,
30267 trace state variable names, memory ranges and computed expressions
30268 that have been collected at a particular trace frame. The optional
30269 parameters to the command affect the output format in different ways.
30270 See the output description table below for more details.
30272 The reported names can be used in the normal manner to create
30273 varobjs and inspect the objects themselves. The items returned by
30274 this command are categorized so that it is clear which is a variable,
30275 which is a register, which is a trace state variable, which is a
30276 memory range and which is a computed expression.
30278 For instance, if the actions were
30280 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30281 collect *(int*)0xaf02bef0@@40
30285 the object collected in its entirety would be @code{myVar}. The
30286 object @code{myArray} would be partially collected, because only the
30287 element at index @code{myIndex} would be collected. The remaining
30288 objects would be computed expressions.
30290 An example output would be:
30294 -trace-frame-collected
30296 explicit-variables=[@{name="myVar",value="1"@}],
30297 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30298 @{name="myObj.field",value="0"@},
30299 @{name="myPtr->field",value="1"@},
30300 @{name="myCount + 2",value="3"@},
30301 @{name="$tvar1 + 1",value="43970027"@}],
30302 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30303 @{number="1",value="0x0"@},
30304 @{number="2",value="0x4"@},
30306 @{number="125",value="0x0"@}],
30307 tvars=[@{name="$tvar1",current="43970026"@}],
30308 memory=[@{address="0x0000000000602264",length="4"@},
30309 @{address="0x0000000000615bc0",length="4"@}]
30316 @item explicit-variables
30317 The set of objects that have been collected in their entirety (as
30318 opposed to collecting just a few elements of an array or a few struct
30319 members). For each object, its name and value are printed.
30320 The @code{--var-print-values} option affects how or whether the value
30321 field is output. If @var{var_pval} is 0, then print only the names;
30322 if it is 1, print also their values; and if it is 2, print the name,
30323 type and value for simple data types, and the name and type for
30324 arrays, structures and unions.
30326 @item computed-expressions
30327 The set of computed expressions that have been collected at the
30328 current trace frame. The @code{--comp-print-values} option affects
30329 this set like the @code{--var-print-values} option affects the
30330 @code{explicit-variables} set. See above.
30333 The registers that have been collected at the current trace frame.
30334 For each register collected, the name and current value are returned.
30335 The value is formatted according to the @code{--registers-format}
30336 option. See the @command{-data-list-register-values} command for a
30337 list of the allowed formats. The default is @samp{x}.
30340 The trace state variables that have been collected at the current
30341 trace frame. For each trace state variable collected, the name and
30342 current value are returned.
30345 The set of memory ranges that have been collected at the current trace
30346 frame. Its content is a list of tuples. Each tuple represents a
30347 collected memory range and has the following fields:
30351 The start address of the memory range, as hexadecimal literal.
30354 The length of the memory range, as decimal literal.
30357 The contents of the memory block, in hex. This field is only present
30358 if the @code{--memory-contents} option is specified.
30364 @subsubheading @value{GDBN} Command
30366 There is no corresponding @value{GDBN} command.
30368 @subsubheading Example
30370 @subheading -trace-list-variables
30371 @findex -trace-list-variables
30373 @subsubheading Synopsis
30376 -trace-list-variables
30379 Return a table of all defined trace variables. Each element of the
30380 table has the following fields:
30384 The name of the trace variable. This field is always present.
30387 The initial value. This is a 64-bit signed integer. This
30388 field is always present.
30391 The value the trace variable has at the moment. This is a 64-bit
30392 signed integer. This field is absent iff current value is
30393 not defined, for example if the trace was never run, or is
30398 @subsubheading @value{GDBN} Command
30400 The corresponding @value{GDBN} command is @samp{tvariables}.
30402 @subsubheading Example
30406 -trace-list-variables
30407 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30408 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30409 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30410 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30411 body=[variable=@{name="$trace_timestamp",initial="0"@}
30412 variable=@{name="$foo",initial="10",current="15"@}]@}
30416 @subheading -trace-save
30417 @findex -trace-save
30419 @subsubheading Synopsis
30422 -trace-save [-r ] @var{filename}
30425 Saves the collected trace data to @var{filename}. Without the
30426 @samp{-r} option, the data is downloaded from the target and saved
30427 in a local file. With the @samp{-r} option the target is asked
30428 to perform the save.
30430 @subsubheading @value{GDBN} Command
30432 The corresponding @value{GDBN} command is @samp{tsave}.
30435 @subheading -trace-start
30436 @findex -trace-start
30438 @subsubheading Synopsis
30444 Starts a tracing experiments. The result of this command does not
30447 @subsubheading @value{GDBN} Command
30449 The corresponding @value{GDBN} command is @samp{tstart}.
30451 @subheading -trace-status
30452 @findex -trace-status
30454 @subsubheading Synopsis
30460 Obtains the status of a tracing experiment. The result may include
30461 the following fields:
30466 May have a value of either @samp{0}, when no tracing operations are
30467 supported, @samp{1}, when all tracing operations are supported, or
30468 @samp{file} when examining trace file. In the latter case, examining
30469 of trace frame is possible but new tracing experiement cannot be
30470 started. This field is always present.
30473 May have a value of either @samp{0} or @samp{1} depending on whether
30474 tracing experiement is in progress on target. This field is present
30475 if @samp{supported} field is not @samp{0}.
30478 Report the reason why the tracing was stopped last time. This field
30479 may be absent iff tracing was never stopped on target yet. The
30480 value of @samp{request} means the tracing was stopped as result of
30481 the @code{-trace-stop} command. The value of @samp{overflow} means
30482 the tracing buffer is full. The value of @samp{disconnection} means
30483 tracing was automatically stopped when @value{GDBN} has disconnected.
30484 The value of @samp{passcount} means tracing was stopped when a
30485 tracepoint was passed a maximal number of times for that tracepoint.
30486 This field is present if @samp{supported} field is not @samp{0}.
30488 @item stopping-tracepoint
30489 The number of tracepoint whose passcount as exceeded. This field is
30490 present iff the @samp{stop-reason} field has the value of
30494 @itemx frames-created
30495 The @samp{frames} field is a count of the total number of trace frames
30496 in the trace buffer, while @samp{frames-created} is the total created
30497 during the run, including ones that were discarded, such as when a
30498 circular trace buffer filled up. Both fields are optional.
30502 These fields tell the current size of the tracing buffer and the
30503 remaining space. These fields are optional.
30506 The value of the circular trace buffer flag. @code{1} means that the
30507 trace buffer is circular and old trace frames will be discarded if
30508 necessary to make room, @code{0} means that the trace buffer is linear
30512 The value of the disconnected tracing flag. @code{1} means that
30513 tracing will continue after @value{GDBN} disconnects, @code{0} means
30514 that the trace run will stop.
30517 The filename of the trace file being examined. This field is
30518 optional, and only present when examining a trace file.
30522 @subsubheading @value{GDBN} Command
30524 The corresponding @value{GDBN} command is @samp{tstatus}.
30526 @subheading -trace-stop
30527 @findex -trace-stop
30529 @subsubheading Synopsis
30535 Stops a tracing experiment. The result of this command has the same
30536 fields as @code{-trace-status}, except that the @samp{supported} and
30537 @samp{running} fields are not output.
30539 @subsubheading @value{GDBN} Command
30541 The corresponding @value{GDBN} command is @samp{tstop}.
30544 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30545 @node GDB/MI Symbol Query
30546 @section @sc{gdb/mi} Symbol Query Commands
30550 @subheading The @code{-symbol-info-address} Command
30551 @findex -symbol-info-address
30553 @subsubheading Synopsis
30556 -symbol-info-address @var{symbol}
30559 Describe where @var{symbol} is stored.
30561 @subsubheading @value{GDBN} Command
30563 The corresponding @value{GDBN} command is @samp{info address}.
30565 @subsubheading Example
30569 @subheading The @code{-symbol-info-file} Command
30570 @findex -symbol-info-file
30572 @subsubheading Synopsis
30578 Show the file for the symbol.
30580 @subsubheading @value{GDBN} Command
30582 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30583 @samp{gdb_find_file}.
30585 @subsubheading Example
30589 @subheading The @code{-symbol-info-function} Command
30590 @findex -symbol-info-function
30592 @subsubheading Synopsis
30595 -symbol-info-function
30598 Show which function the symbol lives in.
30600 @subsubheading @value{GDBN} Command
30602 @samp{gdb_get_function} in @code{gdbtk}.
30604 @subsubheading Example
30608 @subheading The @code{-symbol-info-line} Command
30609 @findex -symbol-info-line
30611 @subsubheading Synopsis
30617 Show the core addresses of the code for a source line.
30619 @subsubheading @value{GDBN} Command
30621 The corresponding @value{GDBN} command is @samp{info line}.
30622 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30624 @subsubheading Example
30628 @subheading The @code{-symbol-info-symbol} Command
30629 @findex -symbol-info-symbol
30631 @subsubheading Synopsis
30634 -symbol-info-symbol @var{addr}
30637 Describe what symbol is at location @var{addr}.
30639 @subsubheading @value{GDBN} Command
30641 The corresponding @value{GDBN} command is @samp{info symbol}.
30643 @subsubheading Example
30647 @subheading The @code{-symbol-list-functions} Command
30648 @findex -symbol-list-functions
30650 @subsubheading Synopsis
30653 -symbol-list-functions
30656 List the functions in the executable.
30658 @subsubheading @value{GDBN} Command
30660 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30661 @samp{gdb_search} in @code{gdbtk}.
30663 @subsubheading Example
30668 @subheading The @code{-symbol-list-lines} Command
30669 @findex -symbol-list-lines
30671 @subsubheading Synopsis
30674 -symbol-list-lines @var{filename}
30677 Print the list of lines that contain code and their associated program
30678 addresses for the given source filename. The entries are sorted in
30679 ascending PC order.
30681 @subsubheading @value{GDBN} Command
30683 There is no corresponding @value{GDBN} command.
30685 @subsubheading Example
30688 -symbol-list-lines basics.c
30689 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30695 @subheading The @code{-symbol-list-types} Command
30696 @findex -symbol-list-types
30698 @subsubheading Synopsis
30704 List all the type names.
30706 @subsubheading @value{GDBN} Command
30708 The corresponding commands are @samp{info types} in @value{GDBN},
30709 @samp{gdb_search} in @code{gdbtk}.
30711 @subsubheading Example
30715 @subheading The @code{-symbol-list-variables} Command
30716 @findex -symbol-list-variables
30718 @subsubheading Synopsis
30721 -symbol-list-variables
30724 List all the global and static variable names.
30726 @subsubheading @value{GDBN} Command
30728 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30730 @subsubheading Example
30734 @subheading The @code{-symbol-locate} Command
30735 @findex -symbol-locate
30737 @subsubheading Synopsis
30743 @subsubheading @value{GDBN} Command
30745 @samp{gdb_loc} in @code{gdbtk}.
30747 @subsubheading Example
30751 @subheading The @code{-symbol-type} Command
30752 @findex -symbol-type
30754 @subsubheading Synopsis
30757 -symbol-type @var{variable}
30760 Show type of @var{variable}.
30762 @subsubheading @value{GDBN} Command
30764 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30765 @samp{gdb_obj_variable}.
30767 @subsubheading Example
30772 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30773 @node GDB/MI File Commands
30774 @section @sc{gdb/mi} File Commands
30776 This section describes the GDB/MI commands to specify executable file names
30777 and to read in and obtain symbol table information.
30779 @subheading The @code{-file-exec-and-symbols} Command
30780 @findex -file-exec-and-symbols
30782 @subsubheading Synopsis
30785 -file-exec-and-symbols @var{file}
30788 Specify the executable file to be debugged. This file is the one from
30789 which the symbol table is also read. If no file is specified, the
30790 command clears the executable and symbol information. If breakpoints
30791 are set when using this command with no arguments, @value{GDBN} will produce
30792 error messages. Otherwise, no output is produced, except a completion
30795 @subsubheading @value{GDBN} Command
30797 The corresponding @value{GDBN} command is @samp{file}.
30799 @subsubheading Example
30803 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30809 @subheading The @code{-file-exec-file} Command
30810 @findex -file-exec-file
30812 @subsubheading Synopsis
30815 -file-exec-file @var{file}
30818 Specify the executable file to be debugged. Unlike
30819 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30820 from this file. If used without argument, @value{GDBN} clears the information
30821 about the executable file. No output is produced, except a completion
30824 @subsubheading @value{GDBN} Command
30826 The corresponding @value{GDBN} command is @samp{exec-file}.
30828 @subsubheading Example
30832 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30839 @subheading The @code{-file-list-exec-sections} Command
30840 @findex -file-list-exec-sections
30842 @subsubheading Synopsis
30845 -file-list-exec-sections
30848 List the sections of the current executable file.
30850 @subsubheading @value{GDBN} Command
30852 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30853 information as this command. @code{gdbtk} has a corresponding command
30854 @samp{gdb_load_info}.
30856 @subsubheading Example
30861 @subheading The @code{-file-list-exec-source-file} Command
30862 @findex -file-list-exec-source-file
30864 @subsubheading Synopsis
30867 -file-list-exec-source-file
30870 List the line number, the current source file, and the absolute path
30871 to the current source file for the current executable. The macro
30872 information field has a value of @samp{1} or @samp{0} depending on
30873 whether or not the file includes preprocessor macro information.
30875 @subsubheading @value{GDBN} Command
30877 The @value{GDBN} equivalent is @samp{info source}
30879 @subsubheading Example
30883 123-file-list-exec-source-file
30884 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30889 @subheading The @code{-file-list-exec-source-files} Command
30890 @findex -file-list-exec-source-files
30892 @subsubheading Synopsis
30895 -file-list-exec-source-files
30898 List the source files for the current executable.
30900 It will always output both the filename and fullname (absolute file
30901 name) of a source file.
30903 @subsubheading @value{GDBN} Command
30905 The @value{GDBN} equivalent is @samp{info sources}.
30906 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30908 @subsubheading Example
30911 -file-list-exec-source-files
30913 @{file=foo.c,fullname=/home/foo.c@},
30914 @{file=/home/bar.c,fullname=/home/bar.c@},
30915 @{file=gdb_could_not_find_fullpath.c@}]
30920 @subheading The @code{-file-list-shared-libraries} Command
30921 @findex -file-list-shared-libraries
30923 @subsubheading Synopsis
30926 -file-list-shared-libraries
30929 List the shared libraries in the program.
30931 @subsubheading @value{GDBN} Command
30933 The corresponding @value{GDBN} command is @samp{info shared}.
30935 @subsubheading Example
30939 @subheading The @code{-file-list-symbol-files} Command
30940 @findex -file-list-symbol-files
30942 @subsubheading Synopsis
30945 -file-list-symbol-files
30950 @subsubheading @value{GDBN} Command
30952 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30954 @subsubheading Example
30959 @subheading The @code{-file-symbol-file} Command
30960 @findex -file-symbol-file
30962 @subsubheading Synopsis
30965 -file-symbol-file @var{file}
30968 Read symbol table info from the specified @var{file} argument. When
30969 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30970 produced, except for a completion notification.
30972 @subsubheading @value{GDBN} Command
30974 The corresponding @value{GDBN} command is @samp{symbol-file}.
30976 @subsubheading Example
30980 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30986 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30987 @node GDB/MI Memory Overlay Commands
30988 @section @sc{gdb/mi} Memory Overlay Commands
30990 The memory overlay commands are not implemented.
30992 @c @subheading -overlay-auto
30994 @c @subheading -overlay-list-mapping-state
30996 @c @subheading -overlay-list-overlays
30998 @c @subheading -overlay-map
31000 @c @subheading -overlay-off
31002 @c @subheading -overlay-on
31004 @c @subheading -overlay-unmap
31006 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31007 @node GDB/MI Signal Handling Commands
31008 @section @sc{gdb/mi} Signal Handling Commands
31010 Signal handling commands are not implemented.
31012 @c @subheading -signal-handle
31014 @c @subheading -signal-list-handle-actions
31016 @c @subheading -signal-list-signal-types
31020 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31021 @node GDB/MI Target Manipulation
31022 @section @sc{gdb/mi} Target Manipulation Commands
31025 @subheading The @code{-target-attach} Command
31026 @findex -target-attach
31028 @subsubheading Synopsis
31031 -target-attach @var{pid} | @var{gid} | @var{file}
31034 Attach to a process @var{pid} or a file @var{file} outside of
31035 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31036 group, the id previously returned by
31037 @samp{-list-thread-groups --available} must be used.
31039 @subsubheading @value{GDBN} Command
31041 The corresponding @value{GDBN} command is @samp{attach}.
31043 @subsubheading Example
31047 =thread-created,id="1"
31048 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31054 @subheading The @code{-target-compare-sections} Command
31055 @findex -target-compare-sections
31057 @subsubheading Synopsis
31060 -target-compare-sections [ @var{section} ]
31063 Compare data of section @var{section} on target to the exec file.
31064 Without the argument, all sections are compared.
31066 @subsubheading @value{GDBN} Command
31068 The @value{GDBN} equivalent is @samp{compare-sections}.
31070 @subsubheading Example
31075 @subheading The @code{-target-detach} Command
31076 @findex -target-detach
31078 @subsubheading Synopsis
31081 -target-detach [ @var{pid} | @var{gid} ]
31084 Detach from the remote target which normally resumes its execution.
31085 If either @var{pid} or @var{gid} is specified, detaches from either
31086 the specified process, or specified thread group. There's no output.
31088 @subsubheading @value{GDBN} Command
31090 The corresponding @value{GDBN} command is @samp{detach}.
31092 @subsubheading Example
31102 @subheading The @code{-target-disconnect} Command
31103 @findex -target-disconnect
31105 @subsubheading Synopsis
31111 Disconnect from the remote target. There's no output and the target is
31112 generally not resumed.
31114 @subsubheading @value{GDBN} Command
31116 The corresponding @value{GDBN} command is @samp{disconnect}.
31118 @subsubheading Example
31128 @subheading The @code{-target-download} Command
31129 @findex -target-download
31131 @subsubheading Synopsis
31137 Loads the executable onto the remote target.
31138 It prints out an update message every half second, which includes the fields:
31142 The name of the section.
31144 The size of what has been sent so far for that section.
31146 The size of the section.
31148 The total size of what was sent so far (the current and the previous sections).
31150 The size of the overall executable to download.
31154 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31155 @sc{gdb/mi} Output Syntax}).
31157 In addition, it prints the name and size of the sections, as they are
31158 downloaded. These messages include the following fields:
31162 The name of the section.
31164 The size of the section.
31166 The size of the overall executable to download.
31170 At the end, a summary is printed.
31172 @subsubheading @value{GDBN} Command
31174 The corresponding @value{GDBN} command is @samp{load}.
31176 @subsubheading Example
31178 Note: each status message appears on a single line. Here the messages
31179 have been broken down so that they can fit onto a page.
31184 +download,@{section=".text",section-size="6668",total-size="9880"@}
31185 +download,@{section=".text",section-sent="512",section-size="6668",
31186 total-sent="512",total-size="9880"@}
31187 +download,@{section=".text",section-sent="1024",section-size="6668",
31188 total-sent="1024",total-size="9880"@}
31189 +download,@{section=".text",section-sent="1536",section-size="6668",
31190 total-sent="1536",total-size="9880"@}
31191 +download,@{section=".text",section-sent="2048",section-size="6668",
31192 total-sent="2048",total-size="9880"@}
31193 +download,@{section=".text",section-sent="2560",section-size="6668",
31194 total-sent="2560",total-size="9880"@}
31195 +download,@{section=".text",section-sent="3072",section-size="6668",
31196 total-sent="3072",total-size="9880"@}
31197 +download,@{section=".text",section-sent="3584",section-size="6668",
31198 total-sent="3584",total-size="9880"@}
31199 +download,@{section=".text",section-sent="4096",section-size="6668",
31200 total-sent="4096",total-size="9880"@}
31201 +download,@{section=".text",section-sent="4608",section-size="6668",
31202 total-sent="4608",total-size="9880"@}
31203 +download,@{section=".text",section-sent="5120",section-size="6668",
31204 total-sent="5120",total-size="9880"@}
31205 +download,@{section=".text",section-sent="5632",section-size="6668",
31206 total-sent="5632",total-size="9880"@}
31207 +download,@{section=".text",section-sent="6144",section-size="6668",
31208 total-sent="6144",total-size="9880"@}
31209 +download,@{section=".text",section-sent="6656",section-size="6668",
31210 total-sent="6656",total-size="9880"@}
31211 +download,@{section=".init",section-size="28",total-size="9880"@}
31212 +download,@{section=".fini",section-size="28",total-size="9880"@}
31213 +download,@{section=".data",section-size="3156",total-size="9880"@}
31214 +download,@{section=".data",section-sent="512",section-size="3156",
31215 total-sent="7236",total-size="9880"@}
31216 +download,@{section=".data",section-sent="1024",section-size="3156",
31217 total-sent="7748",total-size="9880"@}
31218 +download,@{section=".data",section-sent="1536",section-size="3156",
31219 total-sent="8260",total-size="9880"@}
31220 +download,@{section=".data",section-sent="2048",section-size="3156",
31221 total-sent="8772",total-size="9880"@}
31222 +download,@{section=".data",section-sent="2560",section-size="3156",
31223 total-sent="9284",total-size="9880"@}
31224 +download,@{section=".data",section-sent="3072",section-size="3156",
31225 total-sent="9796",total-size="9880"@}
31226 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31233 @subheading The @code{-target-exec-status} Command
31234 @findex -target-exec-status
31236 @subsubheading Synopsis
31239 -target-exec-status
31242 Provide information on the state of the target (whether it is running or
31243 not, for instance).
31245 @subsubheading @value{GDBN} Command
31247 There's no equivalent @value{GDBN} command.
31249 @subsubheading Example
31253 @subheading The @code{-target-list-available-targets} Command
31254 @findex -target-list-available-targets
31256 @subsubheading Synopsis
31259 -target-list-available-targets
31262 List the possible targets to connect to.
31264 @subsubheading @value{GDBN} Command
31266 The corresponding @value{GDBN} command is @samp{help target}.
31268 @subsubheading Example
31272 @subheading The @code{-target-list-current-targets} Command
31273 @findex -target-list-current-targets
31275 @subsubheading Synopsis
31278 -target-list-current-targets
31281 Describe the current target.
31283 @subsubheading @value{GDBN} Command
31285 The corresponding information is printed by @samp{info file} (among
31288 @subsubheading Example
31292 @subheading The @code{-target-list-parameters} Command
31293 @findex -target-list-parameters
31295 @subsubheading Synopsis
31298 -target-list-parameters
31304 @subsubheading @value{GDBN} Command
31308 @subsubheading Example
31312 @subheading The @code{-target-select} Command
31313 @findex -target-select
31315 @subsubheading Synopsis
31318 -target-select @var{type} @var{parameters @dots{}}
31321 Connect @value{GDBN} to the remote target. This command takes two args:
31325 The type of target, for instance @samp{remote}, etc.
31326 @item @var{parameters}
31327 Device names, host names and the like. @xref{Target Commands, ,
31328 Commands for Managing Targets}, for more details.
31331 The output is a connection notification, followed by the address at
31332 which the target program is, in the following form:
31335 ^connected,addr="@var{address}",func="@var{function name}",
31336 args=[@var{arg list}]
31339 @subsubheading @value{GDBN} Command
31341 The corresponding @value{GDBN} command is @samp{target}.
31343 @subsubheading Example
31347 -target-select remote /dev/ttya
31348 ^connected,addr="0xfe00a300",func="??",args=[]
31352 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31353 @node GDB/MI File Transfer Commands
31354 @section @sc{gdb/mi} File Transfer Commands
31357 @subheading The @code{-target-file-put} Command
31358 @findex -target-file-put
31360 @subsubheading Synopsis
31363 -target-file-put @var{hostfile} @var{targetfile}
31366 Copy file @var{hostfile} from the host system (the machine running
31367 @value{GDBN}) to @var{targetfile} on the target system.
31369 @subsubheading @value{GDBN} Command
31371 The corresponding @value{GDBN} command is @samp{remote put}.
31373 @subsubheading Example
31377 -target-file-put localfile remotefile
31383 @subheading The @code{-target-file-get} Command
31384 @findex -target-file-get
31386 @subsubheading Synopsis
31389 -target-file-get @var{targetfile} @var{hostfile}
31392 Copy file @var{targetfile} from the target system to @var{hostfile}
31393 on the host system.
31395 @subsubheading @value{GDBN} Command
31397 The corresponding @value{GDBN} command is @samp{remote get}.
31399 @subsubheading Example
31403 -target-file-get remotefile localfile
31409 @subheading The @code{-target-file-delete} Command
31410 @findex -target-file-delete
31412 @subsubheading Synopsis
31415 -target-file-delete @var{targetfile}
31418 Delete @var{targetfile} from the target system.
31420 @subsubheading @value{GDBN} Command
31422 The corresponding @value{GDBN} command is @samp{remote delete}.
31424 @subsubheading Example
31428 -target-file-delete remotefile
31434 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31435 @node GDB/MI Ada Exceptions Commands
31436 @section Ada Exceptions @sc{gdb/mi} Commands
31438 @subheading The @code{-info-ada-exceptions} Command
31439 @findex -info-ada-exceptions
31441 @subsubheading Synopsis
31444 -info-ada-exceptions [ @var{regexp}]
31447 List all Ada exceptions defined within the program being debugged.
31448 With a regular expression @var{regexp}, only those exceptions whose
31449 names match @var{regexp} are listed.
31451 @subsubheading @value{GDBN} Command
31453 The corresponding @value{GDBN} command is @samp{info exceptions}.
31455 @subsubheading Result
31457 The result is a table of Ada exceptions. The following columns are
31458 defined for each exception:
31462 The name of the exception.
31465 The address of the exception.
31469 @subsubheading Example
31472 -info-ada-exceptions aint
31473 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31474 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31475 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31476 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31477 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31480 @subheading Catching Ada Exceptions
31482 The commands describing how to ask @value{GDBN} to stop when a program
31483 raises an exception are described at @ref{Ada Exception GDB/MI
31484 Catchpoint Commands}.
31487 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31488 @node GDB/MI Support Commands
31489 @section @sc{gdb/mi} Support Commands
31491 Since new commands and features get regularly added to @sc{gdb/mi},
31492 some commands are available to help front-ends query the debugger
31493 about support for these capabilities. Similarly, it is also possible
31494 to query @value{GDBN} about target support of certain features.
31496 @subheading The @code{-info-gdb-mi-command} Command
31497 @cindex @code{-info-gdb-mi-command}
31498 @findex -info-gdb-mi-command
31500 @subsubheading Synopsis
31503 -info-gdb-mi-command @var{cmd_name}
31506 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31508 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31509 is technically not part of the command name (@pxref{GDB/MI Input
31510 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31511 for ease of use, this command also accepts the form with the leading
31514 @subsubheading @value{GDBN} Command
31516 There is no corresponding @value{GDBN} command.
31518 @subsubheading Result
31520 The result is a tuple. There is currently only one field:
31524 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31525 @code{"false"} otherwise.
31529 @subsubheading Example
31531 Here is an example where the @sc{gdb/mi} command does not exist:
31534 -info-gdb-mi-command unsupported-command
31535 ^done,command=@{exists="false"@}
31539 And here is an example where the @sc{gdb/mi} command is known
31543 -info-gdb-mi-command symbol-list-lines
31544 ^done,command=@{exists="true"@}
31547 @subheading The @code{-list-features} Command
31548 @findex -list-features
31549 @cindex supported @sc{gdb/mi} features, list
31551 Returns a list of particular features of the MI protocol that
31552 this version of gdb implements. A feature can be a command,
31553 or a new field in an output of some command, or even an
31554 important bugfix. While a frontend can sometimes detect presence
31555 of a feature at runtime, it is easier to perform detection at debugger
31558 The command returns a list of strings, with each string naming an
31559 available feature. Each returned string is just a name, it does not
31560 have any internal structure. The list of possible feature names
31566 (gdb) -list-features
31567 ^done,result=["feature1","feature2"]
31570 The current list of features is:
31573 @item frozen-varobjs
31574 Indicates support for the @code{-var-set-frozen} command, as well
31575 as possible presense of the @code{frozen} field in the output
31576 of @code{-varobj-create}.
31577 @item pending-breakpoints
31578 Indicates support for the @option{-f} option to the @code{-break-insert}
31581 Indicates Python scripting support, Python-based
31582 pretty-printing commands, and possible presence of the
31583 @samp{display_hint} field in the output of @code{-var-list-children}
31585 Indicates support for the @code{-thread-info} command.
31586 @item data-read-memory-bytes
31587 Indicates support for the @code{-data-read-memory-bytes} and the
31588 @code{-data-write-memory-bytes} commands.
31589 @item breakpoint-notifications
31590 Indicates that changes to breakpoints and breakpoints created via the
31591 CLI will be announced via async records.
31592 @item ada-task-info
31593 Indicates support for the @code{-ada-task-info} command.
31594 @item language-option
31595 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31596 option (@pxref{Context management}).
31597 @item info-gdb-mi-command
31598 Indicates support for the @code{-info-gdb-mi-command} command.
31599 @item undefined-command-error-code
31600 Indicates support for the "undefined-command" error code in error result
31601 records, produced when trying to execute an undefined @sc{gdb/mi} command
31602 (@pxref{GDB/MI Result Records}).
31603 @item exec-run-start-option
31604 Indicates that the @code{-exec-run} command supports the @option{--start}
31605 option (@pxref{GDB/MI Program Execution}).
31608 @subheading The @code{-list-target-features} Command
31609 @findex -list-target-features
31611 Returns a list of particular features that are supported by the
31612 target. Those features affect the permitted MI commands, but
31613 unlike the features reported by the @code{-list-features} command, the
31614 features depend on which target GDB is using at the moment. Whenever
31615 a target can change, due to commands such as @code{-target-select},
31616 @code{-target-attach} or @code{-exec-run}, the list of target features
31617 may change, and the frontend should obtain it again.
31621 (gdb) -list-target-features
31622 ^done,result=["async"]
31625 The current list of features is:
31629 Indicates that the target is capable of asynchronous command
31630 execution, which means that @value{GDBN} will accept further commands
31631 while the target is running.
31634 Indicates that the target is capable of reverse execution.
31635 @xref{Reverse Execution}, for more information.
31639 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31640 @node GDB/MI Miscellaneous Commands
31641 @section Miscellaneous @sc{gdb/mi} Commands
31643 @c @subheading -gdb-complete
31645 @subheading The @code{-gdb-exit} Command
31648 @subsubheading Synopsis
31654 Exit @value{GDBN} immediately.
31656 @subsubheading @value{GDBN} Command
31658 Approximately corresponds to @samp{quit}.
31660 @subsubheading Example
31670 @subheading The @code{-exec-abort} Command
31671 @findex -exec-abort
31673 @subsubheading Synopsis
31679 Kill the inferior running program.
31681 @subsubheading @value{GDBN} Command
31683 The corresponding @value{GDBN} command is @samp{kill}.
31685 @subsubheading Example
31690 @subheading The @code{-gdb-set} Command
31693 @subsubheading Synopsis
31699 Set an internal @value{GDBN} variable.
31700 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31702 @subsubheading @value{GDBN} Command
31704 The corresponding @value{GDBN} command is @samp{set}.
31706 @subsubheading Example
31716 @subheading The @code{-gdb-show} Command
31719 @subsubheading Synopsis
31725 Show the current value of a @value{GDBN} variable.
31727 @subsubheading @value{GDBN} Command
31729 The corresponding @value{GDBN} command is @samp{show}.
31731 @subsubheading Example
31740 @c @subheading -gdb-source
31743 @subheading The @code{-gdb-version} Command
31744 @findex -gdb-version
31746 @subsubheading Synopsis
31752 Show version information for @value{GDBN}. Used mostly in testing.
31754 @subsubheading @value{GDBN} Command
31756 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31757 default shows this information when you start an interactive session.
31759 @subsubheading Example
31761 @c This example modifies the actual output from GDB to avoid overfull
31767 ~Copyright 2000 Free Software Foundation, Inc.
31768 ~GDB is free software, covered by the GNU General Public License, and
31769 ~you are welcome to change it and/or distribute copies of it under
31770 ~ certain conditions.
31771 ~Type "show copying" to see the conditions.
31772 ~There is absolutely no warranty for GDB. Type "show warranty" for
31774 ~This GDB was configured as
31775 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31780 @subheading The @code{-list-thread-groups} Command
31781 @findex -list-thread-groups
31783 @subheading Synopsis
31786 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31789 Lists thread groups (@pxref{Thread groups}). When a single thread
31790 group is passed as the argument, lists the children of that group.
31791 When several thread group are passed, lists information about those
31792 thread groups. Without any parameters, lists information about all
31793 top-level thread groups.
31795 Normally, thread groups that are being debugged are reported.
31796 With the @samp{--available} option, @value{GDBN} reports thread groups
31797 available on the target.
31799 The output of this command may have either a @samp{threads} result or
31800 a @samp{groups} result. The @samp{thread} result has a list of tuples
31801 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31802 Information}). The @samp{groups} result has a list of tuples as value,
31803 each tuple describing a thread group. If top-level groups are
31804 requested (that is, no parameter is passed), or when several groups
31805 are passed, the output always has a @samp{groups} result. The format
31806 of the @samp{group} result is described below.
31808 To reduce the number of roundtrips it's possible to list thread groups
31809 together with their children, by passing the @samp{--recurse} option
31810 and the recursion depth. Presently, only recursion depth of 1 is
31811 permitted. If this option is present, then every reported thread group
31812 will also include its children, either as @samp{group} or
31813 @samp{threads} field.
31815 In general, any combination of option and parameters is permitted, with
31816 the following caveats:
31820 When a single thread group is passed, the output will typically
31821 be the @samp{threads} result. Because threads may not contain
31822 anything, the @samp{recurse} option will be ignored.
31825 When the @samp{--available} option is passed, limited information may
31826 be available. In particular, the list of threads of a process might
31827 be inaccessible. Further, specifying specific thread groups might
31828 not give any performance advantage over listing all thread groups.
31829 The frontend should assume that @samp{-list-thread-groups --available}
31830 is always an expensive operation and cache the results.
31834 The @samp{groups} result is a list of tuples, where each tuple may
31835 have the following fields:
31839 Identifier of the thread group. This field is always present.
31840 The identifier is an opaque string; frontends should not try to
31841 convert it to an integer, even though it might look like one.
31844 The type of the thread group. At present, only @samp{process} is a
31848 The target-specific process identifier. This field is only present
31849 for thread groups of type @samp{process} and only if the process exists.
31852 The exit code of this group's last exited thread, formatted in octal.
31853 This field is only present for thread groups of type @samp{process} and
31854 only if the process is not running.
31857 The number of children this thread group has. This field may be
31858 absent for an available thread group.
31861 This field has a list of tuples as value, each tuple describing a
31862 thread. It may be present if the @samp{--recurse} option is
31863 specified, and it's actually possible to obtain the threads.
31866 This field is a list of integers, each identifying a core that one
31867 thread of the group is running on. This field may be absent if
31868 such information is not available.
31871 The name of the executable file that corresponds to this thread group.
31872 The field is only present for thread groups of type @samp{process},
31873 and only if there is a corresponding executable file.
31877 @subheading Example
31881 -list-thread-groups
31882 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31883 -list-thread-groups 17
31884 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31885 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31886 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31887 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31888 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31889 -list-thread-groups --available
31890 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31891 -list-thread-groups --available --recurse 1
31892 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31893 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31894 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31895 -list-thread-groups --available --recurse 1 17 18
31896 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31897 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31898 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31901 @subheading The @code{-info-os} Command
31904 @subsubheading Synopsis
31907 -info-os [ @var{type} ]
31910 If no argument is supplied, the command returns a table of available
31911 operating-system-specific information types. If one of these types is
31912 supplied as an argument @var{type}, then the command returns a table
31913 of data of that type.
31915 The types of information available depend on the target operating
31918 @subsubheading @value{GDBN} Command
31920 The corresponding @value{GDBN} command is @samp{info os}.
31922 @subsubheading Example
31924 When run on a @sc{gnu}/Linux system, the output will look something
31930 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
31931 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31932 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31933 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31934 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
31936 item=@{col0="files",col1="Listing of all file descriptors",
31937 col2="File descriptors"@},
31938 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31939 col2="Kernel modules"@},
31940 item=@{col0="msg",col1="Listing of all message queues",
31941 col2="Message queues"@},
31942 item=@{col0="processes",col1="Listing of all processes",
31943 col2="Processes"@},
31944 item=@{col0="procgroups",col1="Listing of all process groups",
31945 col2="Process groups"@},
31946 item=@{col0="semaphores",col1="Listing of all semaphores",
31947 col2="Semaphores"@},
31948 item=@{col0="shm",col1="Listing of all shared-memory regions",
31949 col2="Shared-memory regions"@},
31950 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
31952 item=@{col0="threads",col1="Listing of all threads",
31956 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
31957 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
31958 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
31959 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
31960 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
31961 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
31962 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
31963 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
31965 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
31966 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
31970 (Note that the MI output here includes a @code{"Title"} column that
31971 does not appear in command-line @code{info os}; this column is useful
31972 for MI clients that want to enumerate the types of data, such as in a
31973 popup menu, but is needless clutter on the command line, and
31974 @code{info os} omits it.)
31976 @subheading The @code{-add-inferior} Command
31977 @findex -add-inferior
31979 @subheading Synopsis
31985 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31986 inferior is not associated with any executable. Such association may
31987 be established with the @samp{-file-exec-and-symbols} command
31988 (@pxref{GDB/MI File Commands}). The command response has a single
31989 field, @samp{inferior}, whose value is the identifier of the
31990 thread group corresponding to the new inferior.
31992 @subheading Example
31997 ^done,inferior="i3"
32000 @subheading The @code{-interpreter-exec} Command
32001 @findex -interpreter-exec
32003 @subheading Synopsis
32006 -interpreter-exec @var{interpreter} @var{command}
32008 @anchor{-interpreter-exec}
32010 Execute the specified @var{command} in the given @var{interpreter}.
32012 @subheading @value{GDBN} Command
32014 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32016 @subheading Example
32020 -interpreter-exec console "break main"
32021 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32022 &"During symbol reading, bad structure-type format.\n"
32023 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32028 @subheading The @code{-inferior-tty-set} Command
32029 @findex -inferior-tty-set
32031 @subheading Synopsis
32034 -inferior-tty-set /dev/pts/1
32037 Set terminal for future runs of the program being debugged.
32039 @subheading @value{GDBN} Command
32041 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32043 @subheading Example
32047 -inferior-tty-set /dev/pts/1
32052 @subheading The @code{-inferior-tty-show} Command
32053 @findex -inferior-tty-show
32055 @subheading Synopsis
32061 Show terminal for future runs of program being debugged.
32063 @subheading @value{GDBN} Command
32065 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32067 @subheading Example
32071 -inferior-tty-set /dev/pts/1
32075 ^done,inferior_tty_terminal="/dev/pts/1"
32079 @subheading The @code{-enable-timings} Command
32080 @findex -enable-timings
32082 @subheading Synopsis
32085 -enable-timings [yes | no]
32088 Toggle the printing of the wallclock, user and system times for an MI
32089 command as a field in its output. This command is to help frontend
32090 developers optimize the performance of their code. No argument is
32091 equivalent to @samp{yes}.
32093 @subheading @value{GDBN} Command
32097 @subheading Example
32105 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32106 addr="0x080484ed",func="main",file="myprog.c",
32107 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32109 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32117 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32118 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32119 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32120 fullname="/home/nickrob/myprog.c",line="73"@}
32125 @chapter @value{GDBN} Annotations
32127 This chapter describes annotations in @value{GDBN}. Annotations were
32128 designed to interface @value{GDBN} to graphical user interfaces or other
32129 similar programs which want to interact with @value{GDBN} at a
32130 relatively high level.
32132 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32136 This is Edition @value{EDITION}, @value{DATE}.
32140 * Annotations Overview:: What annotations are; the general syntax.
32141 * Server Prefix:: Issuing a command without affecting user state.
32142 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32143 * Errors:: Annotations for error messages.
32144 * Invalidation:: Some annotations describe things now invalid.
32145 * Annotations for Running::
32146 Whether the program is running, how it stopped, etc.
32147 * Source Annotations:: Annotations describing source code.
32150 @node Annotations Overview
32151 @section What is an Annotation?
32152 @cindex annotations
32154 Annotations start with a newline character, two @samp{control-z}
32155 characters, and the name of the annotation. If there is no additional
32156 information associated with this annotation, the name of the annotation
32157 is followed immediately by a newline. If there is additional
32158 information, the name of the annotation is followed by a space, the
32159 additional information, and a newline. The additional information
32160 cannot contain newline characters.
32162 Any output not beginning with a newline and two @samp{control-z}
32163 characters denotes literal output from @value{GDBN}. Currently there is
32164 no need for @value{GDBN} to output a newline followed by two
32165 @samp{control-z} characters, but if there was such a need, the
32166 annotations could be extended with an @samp{escape} annotation which
32167 means those three characters as output.
32169 The annotation @var{level}, which is specified using the
32170 @option{--annotate} command line option (@pxref{Mode Options}), controls
32171 how much information @value{GDBN} prints together with its prompt,
32172 values of expressions, source lines, and other types of output. Level 0
32173 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32174 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32175 for programs that control @value{GDBN}, and level 2 annotations have
32176 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32177 Interface, annotate, GDB's Obsolete Annotations}).
32180 @kindex set annotate
32181 @item set annotate @var{level}
32182 The @value{GDBN} command @code{set annotate} sets the level of
32183 annotations to the specified @var{level}.
32185 @item show annotate
32186 @kindex show annotate
32187 Show the current annotation level.
32190 This chapter describes level 3 annotations.
32192 A simple example of starting up @value{GDBN} with annotations is:
32195 $ @kbd{gdb --annotate=3}
32197 Copyright 2003 Free Software Foundation, Inc.
32198 GDB is free software, covered by the GNU General Public License,
32199 and you are welcome to change it and/or distribute copies of it
32200 under certain conditions.
32201 Type "show copying" to see the conditions.
32202 There is absolutely no warranty for GDB. Type "show warranty"
32204 This GDB was configured as "i386-pc-linux-gnu"
32215 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32216 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32217 denotes a @samp{control-z} character) are annotations; the rest is
32218 output from @value{GDBN}.
32220 @node Server Prefix
32221 @section The Server Prefix
32222 @cindex server prefix
32224 If you prefix a command with @samp{server } then it will not affect
32225 the command history, nor will it affect @value{GDBN}'s notion of which
32226 command to repeat if @key{RET} is pressed on a line by itself. This
32227 means that commands can be run behind a user's back by a front-end in
32228 a transparent manner.
32230 The @code{server } prefix does not affect the recording of values into
32231 the value history; to print a value without recording it into the
32232 value history, use the @code{output} command instead of the
32233 @code{print} command.
32235 Using this prefix also disables confirmation requests
32236 (@pxref{confirmation requests}).
32239 @section Annotation for @value{GDBN} Input
32241 @cindex annotations for prompts
32242 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32243 to know when to send output, when the output from a given command is
32246 Different kinds of input each have a different @dfn{input type}. Each
32247 input type has three annotations: a @code{pre-} annotation, which
32248 denotes the beginning of any prompt which is being output, a plain
32249 annotation, which denotes the end of the prompt, and then a @code{post-}
32250 annotation which denotes the end of any echo which may (or may not) be
32251 associated with the input. For example, the @code{prompt} input type
32252 features the following annotations:
32260 The input types are
32263 @findex pre-prompt annotation
32264 @findex prompt annotation
32265 @findex post-prompt annotation
32267 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32269 @findex pre-commands annotation
32270 @findex commands annotation
32271 @findex post-commands annotation
32273 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32274 command. The annotations are repeated for each command which is input.
32276 @findex pre-overload-choice annotation
32277 @findex overload-choice annotation
32278 @findex post-overload-choice annotation
32279 @item overload-choice
32280 When @value{GDBN} wants the user to select between various overloaded functions.
32282 @findex pre-query annotation
32283 @findex query annotation
32284 @findex post-query annotation
32286 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32288 @findex pre-prompt-for-continue annotation
32289 @findex prompt-for-continue annotation
32290 @findex post-prompt-for-continue annotation
32291 @item prompt-for-continue
32292 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32293 expect this to work well; instead use @code{set height 0} to disable
32294 prompting. This is because the counting of lines is buggy in the
32295 presence of annotations.
32300 @cindex annotations for errors, warnings and interrupts
32302 @findex quit annotation
32307 This annotation occurs right before @value{GDBN} responds to an interrupt.
32309 @findex error annotation
32314 This annotation occurs right before @value{GDBN} responds to an error.
32316 Quit and error annotations indicate that any annotations which @value{GDBN} was
32317 in the middle of may end abruptly. For example, if a
32318 @code{value-history-begin} annotation is followed by a @code{error}, one
32319 cannot expect to receive the matching @code{value-history-end}. One
32320 cannot expect not to receive it either, however; an error annotation
32321 does not necessarily mean that @value{GDBN} is immediately returning all the way
32324 @findex error-begin annotation
32325 A quit or error annotation may be preceded by
32331 Any output between that and the quit or error annotation is the error
32334 Warning messages are not yet annotated.
32335 @c If we want to change that, need to fix warning(), type_error(),
32336 @c range_error(), and possibly other places.
32339 @section Invalidation Notices
32341 @cindex annotations for invalidation messages
32342 The following annotations say that certain pieces of state may have
32346 @findex frames-invalid annotation
32347 @item ^Z^Zframes-invalid
32349 The frames (for example, output from the @code{backtrace} command) may
32352 @findex breakpoints-invalid annotation
32353 @item ^Z^Zbreakpoints-invalid
32355 The breakpoints may have changed. For example, the user just added or
32356 deleted a breakpoint.
32359 @node Annotations for Running
32360 @section Running the Program
32361 @cindex annotations for running programs
32363 @findex starting annotation
32364 @findex stopping annotation
32365 When the program starts executing due to a @value{GDBN} command such as
32366 @code{step} or @code{continue},
32372 is output. When the program stops,
32378 is output. Before the @code{stopped} annotation, a variety of
32379 annotations describe how the program stopped.
32382 @findex exited annotation
32383 @item ^Z^Zexited @var{exit-status}
32384 The program exited, and @var{exit-status} is the exit status (zero for
32385 successful exit, otherwise nonzero).
32387 @findex signalled annotation
32388 @findex signal-name annotation
32389 @findex signal-name-end annotation
32390 @findex signal-string annotation
32391 @findex signal-string-end annotation
32392 @item ^Z^Zsignalled
32393 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32394 annotation continues:
32400 ^Z^Zsignal-name-end
32404 ^Z^Zsignal-string-end
32409 where @var{name} is the name of the signal, such as @code{SIGILL} or
32410 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32411 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32412 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32413 user's benefit and have no particular format.
32415 @findex signal annotation
32417 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32418 just saying that the program received the signal, not that it was
32419 terminated with it.
32421 @findex breakpoint annotation
32422 @item ^Z^Zbreakpoint @var{number}
32423 The program hit breakpoint number @var{number}.
32425 @findex watchpoint annotation
32426 @item ^Z^Zwatchpoint @var{number}
32427 The program hit watchpoint number @var{number}.
32430 @node Source Annotations
32431 @section Displaying Source
32432 @cindex annotations for source display
32434 @findex source annotation
32435 The following annotation is used instead of displaying source code:
32438 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32441 where @var{filename} is an absolute file name indicating which source
32442 file, @var{line} is the line number within that file (where 1 is the
32443 first line in the file), @var{character} is the character position
32444 within the file (where 0 is the first character in the file) (for most
32445 debug formats this will necessarily point to the beginning of a line),
32446 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32447 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32448 @var{addr} is the address in the target program associated with the
32449 source which is being displayed. The @var{addr} is in the form @samp{0x}
32450 followed by one or more lowercase hex digits (note that this does not
32451 depend on the language).
32453 @node JIT Interface
32454 @chapter JIT Compilation Interface
32455 @cindex just-in-time compilation
32456 @cindex JIT compilation interface
32458 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32459 interface. A JIT compiler is a program or library that generates native
32460 executable code at runtime and executes it, usually in order to achieve good
32461 performance while maintaining platform independence.
32463 Programs that use JIT compilation are normally difficult to debug because
32464 portions of their code are generated at runtime, instead of being loaded from
32465 object files, which is where @value{GDBN} normally finds the program's symbols
32466 and debug information. In order to debug programs that use JIT compilation,
32467 @value{GDBN} has an interface that allows the program to register in-memory
32468 symbol files with @value{GDBN} at runtime.
32470 If you are using @value{GDBN} to debug a program that uses this interface, then
32471 it should work transparently so long as you have not stripped the binary. If
32472 you are developing a JIT compiler, then the interface is documented in the rest
32473 of this chapter. At this time, the only known client of this interface is the
32476 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32477 JIT compiler communicates with @value{GDBN} by writing data into a global
32478 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32479 attaches, it reads a linked list of symbol files from the global variable to
32480 find existing code, and puts a breakpoint in the function so that it can find
32481 out about additional code.
32484 * Declarations:: Relevant C struct declarations
32485 * Registering Code:: Steps to register code
32486 * Unregistering Code:: Steps to unregister code
32487 * Custom Debug Info:: Emit debug information in a custom format
32491 @section JIT Declarations
32493 These are the relevant struct declarations that a C program should include to
32494 implement the interface:
32504 struct jit_code_entry
32506 struct jit_code_entry *next_entry;
32507 struct jit_code_entry *prev_entry;
32508 const char *symfile_addr;
32509 uint64_t symfile_size;
32512 struct jit_descriptor
32515 /* This type should be jit_actions_t, but we use uint32_t
32516 to be explicit about the bitwidth. */
32517 uint32_t action_flag;
32518 struct jit_code_entry *relevant_entry;
32519 struct jit_code_entry *first_entry;
32522 /* GDB puts a breakpoint in this function. */
32523 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32525 /* Make sure to specify the version statically, because the
32526 debugger may check the version before we can set it. */
32527 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32530 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32531 modifications to this global data properly, which can easily be done by putting
32532 a global mutex around modifications to these structures.
32534 @node Registering Code
32535 @section Registering Code
32537 To register code with @value{GDBN}, the JIT should follow this protocol:
32541 Generate an object file in memory with symbols and other desired debug
32542 information. The file must include the virtual addresses of the sections.
32545 Create a code entry for the file, which gives the start and size of the symbol
32549 Add it to the linked list in the JIT descriptor.
32552 Point the relevant_entry field of the descriptor at the entry.
32555 Set @code{action_flag} to @code{JIT_REGISTER} and call
32556 @code{__jit_debug_register_code}.
32559 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32560 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32561 new code. However, the linked list must still be maintained in order to allow
32562 @value{GDBN} to attach to a running process and still find the symbol files.
32564 @node Unregistering Code
32565 @section Unregistering Code
32567 If code is freed, then the JIT should use the following protocol:
32571 Remove the code entry corresponding to the code from the linked list.
32574 Point the @code{relevant_entry} field of the descriptor at the code entry.
32577 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32578 @code{__jit_debug_register_code}.
32581 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32582 and the JIT will leak the memory used for the associated symbol files.
32584 @node Custom Debug Info
32585 @section Custom Debug Info
32586 @cindex custom JIT debug info
32587 @cindex JIT debug info reader
32589 Generating debug information in platform-native file formats (like ELF
32590 or COFF) may be an overkill for JIT compilers; especially if all the
32591 debug info is used for is displaying a meaningful backtrace. The
32592 issue can be resolved by having the JIT writers decide on a debug info
32593 format and also provide a reader that parses the debug info generated
32594 by the JIT compiler. This section gives a brief overview on writing
32595 such a parser. More specific details can be found in the source file
32596 @file{gdb/jit-reader.in}, which is also installed as a header at
32597 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32599 The reader is implemented as a shared object (so this functionality is
32600 not available on platforms which don't allow loading shared objects at
32601 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32602 @code{jit-reader-unload} are provided, to be used to load and unload
32603 the readers from a preconfigured directory. Once loaded, the shared
32604 object is used the parse the debug information emitted by the JIT
32608 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32609 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32612 @node Using JIT Debug Info Readers
32613 @subsection Using JIT Debug Info Readers
32614 @kindex jit-reader-load
32615 @kindex jit-reader-unload
32617 Readers can be loaded and unloaded using the @code{jit-reader-load}
32618 and @code{jit-reader-unload} commands.
32621 @item jit-reader-load @var{reader}
32622 Load the JIT reader named @var{reader}, which is a shared
32623 object specified as either an absolute or a relative file name. In
32624 the latter case, @value{GDBN} will try to load the reader from a
32625 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32626 system (here @var{libdir} is the system library directory, often
32627 @file{/usr/local/lib}).
32629 Only one reader can be active at a time; trying to load a second
32630 reader when one is already loaded will result in @value{GDBN}
32631 reporting an error. A new JIT reader can be loaded by first unloading
32632 the current one using @code{jit-reader-unload} and then invoking
32633 @code{jit-reader-load}.
32635 @item jit-reader-unload
32636 Unload the currently loaded JIT reader.
32640 @node Writing JIT Debug Info Readers
32641 @subsection Writing JIT Debug Info Readers
32642 @cindex writing JIT debug info readers
32644 As mentioned, a reader is essentially a shared object conforming to a
32645 certain ABI. This ABI is described in @file{jit-reader.h}.
32647 @file{jit-reader.h} defines the structures, macros and functions
32648 required to write a reader. It is installed (along with
32649 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32650 the system include directory.
32652 Readers need to be released under a GPL compatible license. A reader
32653 can be declared as released under such a license by placing the macro
32654 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32656 The entry point for readers is the symbol @code{gdb_init_reader},
32657 which is expected to be a function with the prototype
32659 @findex gdb_init_reader
32661 extern struct gdb_reader_funcs *gdb_init_reader (void);
32664 @cindex @code{struct gdb_reader_funcs}
32666 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32667 functions. These functions are executed to read the debug info
32668 generated by the JIT compiler (@code{read}), to unwind stack frames
32669 (@code{unwind}) and to create canonical frame IDs
32670 (@code{get_Frame_id}). It also has a callback that is called when the
32671 reader is being unloaded (@code{destroy}). The struct looks like this
32674 struct gdb_reader_funcs
32676 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32677 int reader_version;
32679 /* For use by the reader. */
32682 gdb_read_debug_info *read;
32683 gdb_unwind_frame *unwind;
32684 gdb_get_frame_id *get_frame_id;
32685 gdb_destroy_reader *destroy;
32689 @cindex @code{struct gdb_symbol_callbacks}
32690 @cindex @code{struct gdb_unwind_callbacks}
32692 The callbacks are provided with another set of callbacks by
32693 @value{GDBN} to do their job. For @code{read}, these callbacks are
32694 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32695 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32696 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32697 files and new symbol tables inside those object files. @code{struct
32698 gdb_unwind_callbacks} has callbacks to read registers off the current
32699 frame and to write out the values of the registers in the previous
32700 frame. Both have a callback (@code{target_read}) to read bytes off the
32701 target's address space.
32703 @node In-Process Agent
32704 @chapter In-Process Agent
32705 @cindex debugging agent
32706 The traditional debugging model is conceptually low-speed, but works fine,
32707 because most bugs can be reproduced in debugging-mode execution. However,
32708 as multi-core or many-core processors are becoming mainstream, and
32709 multi-threaded programs become more and more popular, there should be more
32710 and more bugs that only manifest themselves at normal-mode execution, for
32711 example, thread races, because debugger's interference with the program's
32712 timing may conceal the bugs. On the other hand, in some applications,
32713 it is not feasible for the debugger to interrupt the program's execution
32714 long enough for the developer to learn anything helpful about its behavior.
32715 If the program's correctness depends on its real-time behavior, delays
32716 introduced by a debugger might cause the program to fail, even when the
32717 code itself is correct. It is useful to be able to observe the program's
32718 behavior without interrupting it.
32720 Therefore, traditional debugging model is too intrusive to reproduce
32721 some bugs. In order to reduce the interference with the program, we can
32722 reduce the number of operations performed by debugger. The
32723 @dfn{In-Process Agent}, a shared library, is running within the same
32724 process with inferior, and is able to perform some debugging operations
32725 itself. As a result, debugger is only involved when necessary, and
32726 performance of debugging can be improved accordingly. Note that
32727 interference with program can be reduced but can't be removed completely,
32728 because the in-process agent will still stop or slow down the program.
32730 The in-process agent can interpret and execute Agent Expressions
32731 (@pxref{Agent Expressions}) during performing debugging operations. The
32732 agent expressions can be used for different purposes, such as collecting
32733 data in tracepoints, and condition evaluation in breakpoints.
32735 @anchor{Control Agent}
32736 You can control whether the in-process agent is used as an aid for
32737 debugging with the following commands:
32740 @kindex set agent on
32742 Causes the in-process agent to perform some operations on behalf of the
32743 debugger. Just which operations requested by the user will be done
32744 by the in-process agent depends on the its capabilities. For example,
32745 if you request to evaluate breakpoint conditions in the in-process agent,
32746 and the in-process agent has such capability as well, then breakpoint
32747 conditions will be evaluated in the in-process agent.
32749 @kindex set agent off
32750 @item set agent off
32751 Disables execution of debugging operations by the in-process agent. All
32752 of the operations will be performed by @value{GDBN}.
32756 Display the current setting of execution of debugging operations by
32757 the in-process agent.
32761 * In-Process Agent Protocol::
32764 @node In-Process Agent Protocol
32765 @section In-Process Agent Protocol
32766 @cindex in-process agent protocol
32768 The in-process agent is able to communicate with both @value{GDBN} and
32769 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32770 used for communications between @value{GDBN} or GDBserver and the IPA.
32771 In general, @value{GDBN} or GDBserver sends commands
32772 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32773 in-process agent replies back with the return result of the command, or
32774 some other information. The data sent to in-process agent is composed
32775 of primitive data types, such as 4-byte or 8-byte type, and composite
32776 types, which are called objects (@pxref{IPA Protocol Objects}).
32779 * IPA Protocol Objects::
32780 * IPA Protocol Commands::
32783 @node IPA Protocol Objects
32784 @subsection IPA Protocol Objects
32785 @cindex ipa protocol objects
32787 The commands sent to and results received from agent may contain some
32788 complex data types called @dfn{objects}.
32790 The in-process agent is running on the same machine with @value{GDBN}
32791 or GDBserver, so it doesn't have to handle as much differences between
32792 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32793 However, there are still some differences of two ends in two processes:
32797 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32798 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32800 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32801 GDBserver is compiled with one, and in-process agent is compiled with
32805 Here are the IPA Protocol Objects:
32809 agent expression object. It represents an agent expression
32810 (@pxref{Agent Expressions}).
32811 @anchor{agent expression object}
32813 tracepoint action object. It represents a tracepoint action
32814 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32815 memory, static trace data and to evaluate expression.
32816 @anchor{tracepoint action object}
32818 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32819 @anchor{tracepoint object}
32823 The following table describes important attributes of each IPA protocol
32826 @multitable @columnfractions .30 .20 .50
32827 @headitem Name @tab Size @tab Description
32828 @item @emph{agent expression object} @tab @tab
32829 @item length @tab 4 @tab length of bytes code
32830 @item byte code @tab @var{length} @tab contents of byte code
32831 @item @emph{tracepoint action for collecting memory} @tab @tab
32832 @item 'M' @tab 1 @tab type of tracepoint action
32833 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32834 address of the lowest byte to collect, otherwise @var{addr} is the offset
32835 of @var{basereg} for memory collecting.
32836 @item len @tab 8 @tab length of memory for collecting
32837 @item basereg @tab 4 @tab the register number containing the starting
32838 memory address for collecting.
32839 @item @emph{tracepoint action for collecting registers} @tab @tab
32840 @item 'R' @tab 1 @tab type of tracepoint action
32841 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32842 @item 'L' @tab 1 @tab type of tracepoint action
32843 @item @emph{tracepoint action for expression evaluation} @tab @tab
32844 @item 'X' @tab 1 @tab type of tracepoint action
32845 @item agent expression @tab length of @tab @ref{agent expression object}
32846 @item @emph{tracepoint object} @tab @tab
32847 @item number @tab 4 @tab number of tracepoint
32848 @item address @tab 8 @tab address of tracepoint inserted on
32849 @item type @tab 4 @tab type of tracepoint
32850 @item enabled @tab 1 @tab enable or disable of tracepoint
32851 @item step_count @tab 8 @tab step
32852 @item pass_count @tab 8 @tab pass
32853 @item numactions @tab 4 @tab number of tracepoint actions
32854 @item hit count @tab 8 @tab hit count
32855 @item trace frame usage @tab 8 @tab trace frame usage
32856 @item compiled_cond @tab 8 @tab compiled condition
32857 @item orig_size @tab 8 @tab orig size
32858 @item condition @tab 4 if condition is NULL otherwise length of
32859 @ref{agent expression object}
32860 @tab zero if condition is NULL, otherwise is
32861 @ref{agent expression object}
32862 @item actions @tab variable
32863 @tab numactions number of @ref{tracepoint action object}
32866 @node IPA Protocol Commands
32867 @subsection IPA Protocol Commands
32868 @cindex ipa protocol commands
32870 The spaces in each command are delimiters to ease reading this commands
32871 specification. They don't exist in real commands.
32875 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32876 Installs a new fast tracepoint described by @var{tracepoint_object}
32877 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
32878 head of @dfn{jumppad}, which is used to jump to data collection routine
32883 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32884 @var{target_address} is address of tracepoint in the inferior.
32885 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32886 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32887 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
32888 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32895 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32896 is about to kill inferiors.
32904 @item probe_marker_at:@var{address}
32905 Asks in-process agent to probe the marker at @var{address}.
32912 @item unprobe_marker_at:@var{address}
32913 Asks in-process agent to unprobe the marker at @var{address}.
32917 @chapter Reporting Bugs in @value{GDBN}
32918 @cindex bugs in @value{GDBN}
32919 @cindex reporting bugs in @value{GDBN}
32921 Your bug reports play an essential role in making @value{GDBN} reliable.
32923 Reporting a bug may help you by bringing a solution to your problem, or it
32924 may not. But in any case the principal function of a bug report is to help
32925 the entire community by making the next version of @value{GDBN} work better. Bug
32926 reports are your contribution to the maintenance of @value{GDBN}.
32928 In order for a bug report to serve its purpose, you must include the
32929 information that enables us to fix the bug.
32932 * Bug Criteria:: Have you found a bug?
32933 * Bug Reporting:: How to report bugs
32937 @section Have You Found a Bug?
32938 @cindex bug criteria
32940 If you are not sure whether you have found a bug, here are some guidelines:
32943 @cindex fatal signal
32944 @cindex debugger crash
32945 @cindex crash of debugger
32947 If the debugger gets a fatal signal, for any input whatever, that is a
32948 @value{GDBN} bug. Reliable debuggers never crash.
32950 @cindex error on valid input
32952 If @value{GDBN} produces an error message for valid input, that is a
32953 bug. (Note that if you're cross debugging, the problem may also be
32954 somewhere in the connection to the target.)
32956 @cindex invalid input
32958 If @value{GDBN} does not produce an error message for invalid input,
32959 that is a bug. However, you should note that your idea of
32960 ``invalid input'' might be our idea of ``an extension'' or ``support
32961 for traditional practice''.
32964 If you are an experienced user of debugging tools, your suggestions
32965 for improvement of @value{GDBN} are welcome in any case.
32968 @node Bug Reporting
32969 @section How to Report Bugs
32970 @cindex bug reports
32971 @cindex @value{GDBN} bugs, reporting
32973 A number of companies and individuals offer support for @sc{gnu} products.
32974 If you obtained @value{GDBN} from a support organization, we recommend you
32975 contact that organization first.
32977 You can find contact information for many support companies and
32978 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32980 @c should add a web page ref...
32983 @ifset BUGURL_DEFAULT
32984 In any event, we also recommend that you submit bug reports for
32985 @value{GDBN}. The preferred method is to submit them directly using
32986 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32987 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32990 @strong{Do not send bug reports to @samp{info-gdb}, or to
32991 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32992 not want to receive bug reports. Those that do have arranged to receive
32995 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32996 serves as a repeater. The mailing list and the newsgroup carry exactly
32997 the same messages. Often people think of posting bug reports to the
32998 newsgroup instead of mailing them. This appears to work, but it has one
32999 problem which can be crucial: a newsgroup posting often lacks a mail
33000 path back to the sender. Thus, if we need to ask for more information,
33001 we may be unable to reach you. For this reason, it is better to send
33002 bug reports to the mailing list.
33004 @ifclear BUGURL_DEFAULT
33005 In any event, we also recommend that you submit bug reports for
33006 @value{GDBN} to @value{BUGURL}.
33010 The fundamental principle of reporting bugs usefully is this:
33011 @strong{report all the facts}. If you are not sure whether to state a
33012 fact or leave it out, state it!
33014 Often people omit facts because they think they know what causes the
33015 problem and assume that some details do not matter. Thus, you might
33016 assume that the name of the variable you use in an example does not matter.
33017 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33018 stray memory reference which happens to fetch from the location where that
33019 name is stored in memory; perhaps, if the name were different, the contents
33020 of that location would fool the debugger into doing the right thing despite
33021 the bug. Play it safe and give a specific, complete example. That is the
33022 easiest thing for you to do, and the most helpful.
33024 Keep in mind that the purpose of a bug report is to enable us to fix the
33025 bug. It may be that the bug has been reported previously, but neither
33026 you nor we can know that unless your bug report is complete and
33029 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33030 bell?'' Those bug reports are useless, and we urge everyone to
33031 @emph{refuse to respond to them} except to chide the sender to report
33034 To enable us to fix the bug, you should include all these things:
33038 The version of @value{GDBN}. @value{GDBN} announces it if you start
33039 with no arguments; you can also print it at any time using @code{show
33042 Without this, we will not know whether there is any point in looking for
33043 the bug in the current version of @value{GDBN}.
33046 The type of machine you are using, and the operating system name and
33050 The details of the @value{GDBN} build-time configuration.
33051 @value{GDBN} shows these details if you invoke it with the
33052 @option{--configuration} command-line option, or if you type
33053 @code{show configuration} at @value{GDBN}'s prompt.
33056 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33057 ``@value{GCC}--2.8.1''.
33060 What compiler (and its version) was used to compile the program you are
33061 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33062 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33063 to get this information; for other compilers, see the documentation for
33067 The command arguments you gave the compiler to compile your example and
33068 observe the bug. For example, did you use @samp{-O}? To guarantee
33069 you will not omit something important, list them all. A copy of the
33070 Makefile (or the output from make) is sufficient.
33072 If we were to try to guess the arguments, we would probably guess wrong
33073 and then we might not encounter the bug.
33076 A complete input script, and all necessary source files, that will
33080 A description of what behavior you observe that you believe is
33081 incorrect. For example, ``It gets a fatal signal.''
33083 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33084 will certainly notice it. But if the bug is incorrect output, we might
33085 not notice unless it is glaringly wrong. You might as well not give us
33086 a chance to make a mistake.
33088 Even if the problem you experience is a fatal signal, you should still
33089 say so explicitly. Suppose something strange is going on, such as, your
33090 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33091 the C library on your system. (This has happened!) Your copy might
33092 crash and ours would not. If you told us to expect a crash, then when
33093 ours fails to crash, we would know that the bug was not happening for
33094 us. If you had not told us to expect a crash, then we would not be able
33095 to draw any conclusion from our observations.
33098 @cindex recording a session script
33099 To collect all this information, you can use a session recording program
33100 such as @command{script}, which is available on many Unix systems.
33101 Just run your @value{GDBN} session inside @command{script} and then
33102 include the @file{typescript} file with your bug report.
33104 Another way to record a @value{GDBN} session is to run @value{GDBN}
33105 inside Emacs and then save the entire buffer to a file.
33108 If you wish to suggest changes to the @value{GDBN} source, send us context
33109 diffs. If you even discuss something in the @value{GDBN} source, refer to
33110 it by context, not by line number.
33112 The line numbers in our development sources will not match those in your
33113 sources. Your line numbers would convey no useful information to us.
33117 Here are some things that are not necessary:
33121 A description of the envelope of the bug.
33123 Often people who encounter a bug spend a lot of time investigating
33124 which changes to the input file will make the bug go away and which
33125 changes will not affect it.
33127 This is often time consuming and not very useful, because the way we
33128 will find the bug is by running a single example under the debugger
33129 with breakpoints, not by pure deduction from a series of examples.
33130 We recommend that you save your time for something else.
33132 Of course, if you can find a simpler example to report @emph{instead}
33133 of the original one, that is a convenience for us. Errors in the
33134 output will be easier to spot, running under the debugger will take
33135 less time, and so on.
33137 However, simplification is not vital; if you do not want to do this,
33138 report the bug anyway and send us the entire test case you used.
33141 A patch for the bug.
33143 A patch for the bug does help us if it is a good one. But do not omit
33144 the necessary information, such as the test case, on the assumption that
33145 a patch is all we need. We might see problems with your patch and decide
33146 to fix the problem another way, or we might not understand it at all.
33148 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33149 construct an example that will make the program follow a certain path
33150 through the code. If you do not send us the example, we will not be able
33151 to construct one, so we will not be able to verify that the bug is fixed.
33153 And if we cannot understand what bug you are trying to fix, or why your
33154 patch should be an improvement, we will not install it. A test case will
33155 help us to understand.
33158 A guess about what the bug is or what it depends on.
33160 Such guesses are usually wrong. Even we cannot guess right about such
33161 things without first using the debugger to find the facts.
33164 @c The readline documentation is distributed with the readline code
33165 @c and consists of the two following files:
33168 @c Use -I with makeinfo to point to the appropriate directory,
33169 @c environment var TEXINPUTS with TeX.
33170 @ifclear SYSTEM_READLINE
33171 @include rluser.texi
33172 @include hsuser.texi
33176 @appendix In Memoriam
33178 The @value{GDBN} project mourns the loss of the following long-time
33183 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33184 to Free Software in general. Outside of @value{GDBN}, he was known in
33185 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33187 @item Michael Snyder
33188 Michael was one of the Global Maintainers of the @value{GDBN} project,
33189 with contributions recorded as early as 1996, until 2011. In addition
33190 to his day to day participation, he was a large driving force behind
33191 adding Reverse Debugging to @value{GDBN}.
33194 Beyond their technical contributions to the project, they were also
33195 enjoyable members of the Free Software Community. We will miss them.
33197 @node Formatting Documentation
33198 @appendix Formatting Documentation
33200 @cindex @value{GDBN} reference card
33201 @cindex reference card
33202 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33203 for printing with PostScript or Ghostscript, in the @file{gdb}
33204 subdirectory of the main source directory@footnote{In
33205 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33206 release.}. If you can use PostScript or Ghostscript with your printer,
33207 you can print the reference card immediately with @file{refcard.ps}.
33209 The release also includes the source for the reference card. You
33210 can format it, using @TeX{}, by typing:
33216 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33217 mode on US ``letter'' size paper;
33218 that is, on a sheet 11 inches wide by 8.5 inches
33219 high. You will need to specify this form of printing as an option to
33220 your @sc{dvi} output program.
33222 @cindex documentation
33224 All the documentation for @value{GDBN} comes as part of the machine-readable
33225 distribution. The documentation is written in Texinfo format, which is
33226 a documentation system that uses a single source file to produce both
33227 on-line information and a printed manual. You can use one of the Info
33228 formatting commands to create the on-line version of the documentation
33229 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33231 @value{GDBN} includes an already formatted copy of the on-line Info
33232 version of this manual in the @file{gdb} subdirectory. The main Info
33233 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33234 subordinate files matching @samp{gdb.info*} in the same directory. If
33235 necessary, you can print out these files, or read them with any editor;
33236 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33237 Emacs or the standalone @code{info} program, available as part of the
33238 @sc{gnu} Texinfo distribution.
33240 If you want to format these Info files yourself, you need one of the
33241 Info formatting programs, such as @code{texinfo-format-buffer} or
33244 If you have @code{makeinfo} installed, and are in the top level
33245 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33246 version @value{GDBVN}), you can make the Info file by typing:
33253 If you want to typeset and print copies of this manual, you need @TeX{},
33254 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33255 Texinfo definitions file.
33257 @TeX{} is a typesetting program; it does not print files directly, but
33258 produces output files called @sc{dvi} files. To print a typeset
33259 document, you need a program to print @sc{dvi} files. If your system
33260 has @TeX{} installed, chances are it has such a program. The precise
33261 command to use depends on your system; @kbd{lpr -d} is common; another
33262 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33263 require a file name without any extension or a @samp{.dvi} extension.
33265 @TeX{} also requires a macro definitions file called
33266 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33267 written in Texinfo format. On its own, @TeX{} cannot either read or
33268 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33269 and is located in the @file{gdb-@var{version-number}/texinfo}
33272 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33273 typeset and print this manual. First switch to the @file{gdb}
33274 subdirectory of the main source directory (for example, to
33275 @file{gdb-@value{GDBVN}/gdb}) and type:
33281 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33283 @node Installing GDB
33284 @appendix Installing @value{GDBN}
33285 @cindex installation
33288 * Requirements:: Requirements for building @value{GDBN}
33289 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33290 * Separate Objdir:: Compiling @value{GDBN} in another directory
33291 * Config Names:: Specifying names for hosts and targets
33292 * Configure Options:: Summary of options for configure
33293 * System-wide configuration:: Having a system-wide init file
33297 @section Requirements for Building @value{GDBN}
33298 @cindex building @value{GDBN}, requirements for
33300 Building @value{GDBN} requires various tools and packages to be available.
33301 Other packages will be used only if they are found.
33303 @heading Tools/Packages Necessary for Building @value{GDBN}
33305 @item ISO C90 compiler
33306 @value{GDBN} is written in ISO C90. It should be buildable with any
33307 working C90 compiler, e.g.@: GCC.
33311 @heading Tools/Packages Optional for Building @value{GDBN}
33315 @value{GDBN} can use the Expat XML parsing library. This library may be
33316 included with your operating system distribution; if it is not, you
33317 can get the latest version from @url{http://expat.sourceforge.net}.
33318 The @file{configure} script will search for this library in several
33319 standard locations; if it is installed in an unusual path, you can
33320 use the @option{--with-libexpat-prefix} option to specify its location.
33326 Remote protocol memory maps (@pxref{Memory Map Format})
33328 Target descriptions (@pxref{Target Descriptions})
33330 Remote shared library lists (@xref{Library List Format},
33331 or alternatively @pxref{Library List Format for SVR4 Targets})
33333 MS-Windows shared libraries (@pxref{Shared Libraries})
33335 Traceframe info (@pxref{Traceframe Info Format})
33337 Branch trace (@pxref{Branch Trace Format},
33338 @pxref{Branch Trace Configuration Format})
33342 @cindex compressed debug sections
33343 @value{GDBN} will use the @samp{zlib} library, if available, to read
33344 compressed debug sections. Some linkers, such as GNU gold, are capable
33345 of producing binaries with compressed debug sections. If @value{GDBN}
33346 is compiled with @samp{zlib}, it will be able to read the debug
33347 information in such binaries.
33349 The @samp{zlib} library is likely included with your operating system
33350 distribution; if it is not, you can get the latest version from
33351 @url{http://zlib.net}.
33354 @value{GDBN}'s features related to character sets (@pxref{Character
33355 Sets}) require a functioning @code{iconv} implementation. If you are
33356 on a GNU system, then this is provided by the GNU C Library. Some
33357 other systems also provide a working @code{iconv}.
33359 If @value{GDBN} is using the @code{iconv} program which is installed
33360 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33361 This is done with @option{--with-iconv-bin} which specifies the
33362 directory that contains the @code{iconv} program.
33364 On systems without @code{iconv}, you can install GNU Libiconv. If you
33365 have previously installed Libiconv, you can use the
33366 @option{--with-libiconv-prefix} option to configure.
33368 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33369 arrange to build Libiconv if a directory named @file{libiconv} appears
33370 in the top-most source directory. If Libiconv is built this way, and
33371 if the operating system does not provide a suitable @code{iconv}
33372 implementation, then the just-built library will automatically be used
33373 by @value{GDBN}. One easy way to set this up is to download GNU
33374 Libiconv, unpack it, and then rename the directory holding the
33375 Libiconv source code to @samp{libiconv}.
33378 @node Running Configure
33379 @section Invoking the @value{GDBN} @file{configure} Script
33380 @cindex configuring @value{GDBN}
33381 @value{GDBN} comes with a @file{configure} script that automates the process
33382 of preparing @value{GDBN} for installation; you can then use @code{make} to
33383 build the @code{gdb} program.
33385 @c irrelevant in info file; it's as current as the code it lives with.
33386 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33387 look at the @file{README} file in the sources; we may have improved the
33388 installation procedures since publishing this manual.}
33391 The @value{GDBN} distribution includes all the source code you need for
33392 @value{GDBN} in a single directory, whose name is usually composed by
33393 appending the version number to @samp{gdb}.
33395 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33396 @file{gdb-@value{GDBVN}} directory. That directory contains:
33399 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33400 script for configuring @value{GDBN} and all its supporting libraries
33402 @item gdb-@value{GDBVN}/gdb
33403 the source specific to @value{GDBN} itself
33405 @item gdb-@value{GDBVN}/bfd
33406 source for the Binary File Descriptor library
33408 @item gdb-@value{GDBVN}/include
33409 @sc{gnu} include files
33411 @item gdb-@value{GDBVN}/libiberty
33412 source for the @samp{-liberty} free software library
33414 @item gdb-@value{GDBVN}/opcodes
33415 source for the library of opcode tables and disassemblers
33417 @item gdb-@value{GDBVN}/readline
33418 source for the @sc{gnu} command-line interface
33420 @item gdb-@value{GDBVN}/glob
33421 source for the @sc{gnu} filename pattern-matching subroutine
33423 @item gdb-@value{GDBVN}/mmalloc
33424 source for the @sc{gnu} memory-mapped malloc package
33427 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33428 from the @file{gdb-@var{version-number}} source directory, which in
33429 this example is the @file{gdb-@value{GDBVN}} directory.
33431 First switch to the @file{gdb-@var{version-number}} source directory
33432 if you are not already in it; then run @file{configure}. Pass the
33433 identifier for the platform on which @value{GDBN} will run as an
33439 cd gdb-@value{GDBVN}
33440 ./configure @var{host}
33445 where @var{host} is an identifier such as @samp{sun4} or
33446 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33447 (You can often leave off @var{host}; @file{configure} tries to guess the
33448 correct value by examining your system.)
33450 Running @samp{configure @var{host}} and then running @code{make} builds the
33451 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33452 libraries, then @code{gdb} itself. The configured source files, and the
33453 binaries, are left in the corresponding source directories.
33456 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33457 system does not recognize this automatically when you run a different
33458 shell, you may need to run @code{sh} on it explicitly:
33461 sh configure @var{host}
33464 If you run @file{configure} from a directory that contains source
33465 directories for multiple libraries or programs, such as the
33466 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33468 creates configuration files for every directory level underneath (unless
33469 you tell it not to, with the @samp{--norecursion} option).
33471 You should run the @file{configure} script from the top directory in the
33472 source tree, the @file{gdb-@var{version-number}} directory. If you run
33473 @file{configure} from one of the subdirectories, you will configure only
33474 that subdirectory. That is usually not what you want. In particular,
33475 if you run the first @file{configure} from the @file{gdb} subdirectory
33476 of the @file{gdb-@var{version-number}} directory, you will omit the
33477 configuration of @file{bfd}, @file{readline}, and other sibling
33478 directories of the @file{gdb} subdirectory. This leads to build errors
33479 about missing include files such as @file{bfd/bfd.h}.
33481 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33482 However, you should make sure that the shell on your path (named by
33483 the @samp{SHELL} environment variable) is publicly readable. Remember
33484 that @value{GDBN} uses the shell to start your program---some systems refuse to
33485 let @value{GDBN} debug child processes whose programs are not readable.
33487 @node Separate Objdir
33488 @section Compiling @value{GDBN} in Another Directory
33490 If you want to run @value{GDBN} versions for several host or target machines,
33491 you need a different @code{gdb} compiled for each combination of
33492 host and target. @file{configure} is designed to make this easy by
33493 allowing you to generate each configuration in a separate subdirectory,
33494 rather than in the source directory. If your @code{make} program
33495 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33496 @code{make} in each of these directories builds the @code{gdb}
33497 program specified there.
33499 To build @code{gdb} in a separate directory, run @file{configure}
33500 with the @samp{--srcdir} option to specify where to find the source.
33501 (You also need to specify a path to find @file{configure}
33502 itself from your working directory. If the path to @file{configure}
33503 would be the same as the argument to @samp{--srcdir}, you can leave out
33504 the @samp{--srcdir} option; it is assumed.)
33506 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33507 separate directory for a Sun 4 like this:
33511 cd gdb-@value{GDBVN}
33514 ../gdb-@value{GDBVN}/configure sun4
33519 When @file{configure} builds a configuration using a remote source
33520 directory, it creates a tree for the binaries with the same structure
33521 (and using the same names) as the tree under the source directory. In
33522 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33523 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33524 @file{gdb-sun4/gdb}.
33526 Make sure that your path to the @file{configure} script has just one
33527 instance of @file{gdb} in it. If your path to @file{configure} looks
33528 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33529 one subdirectory of @value{GDBN}, not the whole package. This leads to
33530 build errors about missing include files such as @file{bfd/bfd.h}.
33532 One popular reason to build several @value{GDBN} configurations in separate
33533 directories is to configure @value{GDBN} for cross-compiling (where
33534 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33535 programs that run on another machine---the @dfn{target}).
33536 You specify a cross-debugging target by
33537 giving the @samp{--target=@var{target}} option to @file{configure}.
33539 When you run @code{make} to build a program or library, you must run
33540 it in a configured directory---whatever directory you were in when you
33541 called @file{configure} (or one of its subdirectories).
33543 The @code{Makefile} that @file{configure} generates in each source
33544 directory also runs recursively. If you type @code{make} in a source
33545 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33546 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33547 will build all the required libraries, and then build GDB.
33549 When you have multiple hosts or targets configured in separate
33550 directories, you can run @code{make} on them in parallel (for example,
33551 if they are NFS-mounted on each of the hosts); they will not interfere
33555 @section Specifying Names for Hosts and Targets
33557 The specifications used for hosts and targets in the @file{configure}
33558 script are based on a three-part naming scheme, but some short predefined
33559 aliases are also supported. The full naming scheme encodes three pieces
33560 of information in the following pattern:
33563 @var{architecture}-@var{vendor}-@var{os}
33566 For example, you can use the alias @code{sun4} as a @var{host} argument,
33567 or as the value for @var{target} in a @code{--target=@var{target}}
33568 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33570 The @file{configure} script accompanying @value{GDBN} does not provide
33571 any query facility to list all supported host and target names or
33572 aliases. @file{configure} calls the Bourne shell script
33573 @code{config.sub} to map abbreviations to full names; you can read the
33574 script, if you wish, or you can use it to test your guesses on
33575 abbreviations---for example:
33578 % sh config.sub i386-linux
33580 % sh config.sub alpha-linux
33581 alpha-unknown-linux-gnu
33582 % sh config.sub hp9k700
33584 % sh config.sub sun4
33585 sparc-sun-sunos4.1.1
33586 % sh config.sub sun3
33587 m68k-sun-sunos4.1.1
33588 % sh config.sub i986v
33589 Invalid configuration `i986v': machine `i986v' not recognized
33593 @code{config.sub} is also distributed in the @value{GDBN} source
33594 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33596 @node Configure Options
33597 @section @file{configure} Options
33599 Here is a summary of the @file{configure} options and arguments that
33600 are most often useful for building @value{GDBN}. @file{configure} also has
33601 several other options not listed here. @inforef{What Configure
33602 Does,,configure.info}, for a full explanation of @file{configure}.
33605 configure @r{[}--help@r{]}
33606 @r{[}--prefix=@var{dir}@r{]}
33607 @r{[}--exec-prefix=@var{dir}@r{]}
33608 @r{[}--srcdir=@var{dirname}@r{]}
33609 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33610 @r{[}--target=@var{target}@r{]}
33615 You may introduce options with a single @samp{-} rather than
33616 @samp{--} if you prefer; but you may abbreviate option names if you use
33621 Display a quick summary of how to invoke @file{configure}.
33623 @item --prefix=@var{dir}
33624 Configure the source to install programs and files under directory
33627 @item --exec-prefix=@var{dir}
33628 Configure the source to install programs under directory
33631 @c avoid splitting the warning from the explanation:
33633 @item --srcdir=@var{dirname}
33634 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33635 @code{make} that implements the @code{VPATH} feature.}@*
33636 Use this option to make configurations in directories separate from the
33637 @value{GDBN} source directories. Among other things, you can use this to
33638 build (or maintain) several configurations simultaneously, in separate
33639 directories. @file{configure} writes configuration-specific files in
33640 the current directory, but arranges for them to use the source in the
33641 directory @var{dirname}. @file{configure} creates directories under
33642 the working directory in parallel to the source directories below
33645 @item --norecursion
33646 Configure only the directory level where @file{configure} is executed; do not
33647 propagate configuration to subdirectories.
33649 @item --target=@var{target}
33650 Configure @value{GDBN} for cross-debugging programs running on the specified
33651 @var{target}. Without this option, @value{GDBN} is configured to debug
33652 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33654 There is no convenient way to generate a list of all available targets.
33656 @item @var{host} @dots{}
33657 Configure @value{GDBN} to run on the specified @var{host}.
33659 There is no convenient way to generate a list of all available hosts.
33662 There are many other options available as well, but they are generally
33663 needed for special purposes only.
33665 @node System-wide configuration
33666 @section System-wide configuration and settings
33667 @cindex system-wide init file
33669 @value{GDBN} can be configured to have a system-wide init file;
33670 this file will be read and executed at startup (@pxref{Startup, , What
33671 @value{GDBN} does during startup}).
33673 Here is the corresponding configure option:
33676 @item --with-system-gdbinit=@var{file}
33677 Specify that the default location of the system-wide init file is
33681 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33682 it may be subject to relocation. Two possible cases:
33686 If the default location of this init file contains @file{$prefix},
33687 it will be subject to relocation. Suppose that the configure options
33688 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33689 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33690 init file is looked for as @file{$install/etc/gdbinit} instead of
33691 @file{$prefix/etc/gdbinit}.
33694 By contrast, if the default location does not contain the prefix,
33695 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33696 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33697 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33698 wherever @value{GDBN} is installed.
33701 If the configured location of the system-wide init file (as given by the
33702 @option{--with-system-gdbinit} option at configure time) is in the
33703 data-directory (as specified by @option{--with-gdb-datadir} at configure
33704 time) or in one of its subdirectories, then @value{GDBN} will look for the
33705 system-wide init file in the directory specified by the
33706 @option{--data-directory} command-line option.
33707 Note that the system-wide init file is only read once, during @value{GDBN}
33708 initialization. If the data-directory is changed after @value{GDBN} has
33709 started with the @code{set data-directory} command, the file will not be
33713 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33716 @node System-wide Configuration Scripts
33717 @subsection Installed System-wide Configuration Scripts
33718 @cindex system-wide configuration scripts
33720 The @file{system-gdbinit} directory, located inside the data-directory
33721 (as specified by @option{--with-gdb-datadir} at configure time) contains
33722 a number of scripts which can be used as system-wide init files. To
33723 automatically source those scripts at startup, @value{GDBN} should be
33724 configured with @option{--with-system-gdbinit}. Otherwise, any user
33725 should be able to source them by hand as needed.
33727 The following scripts are currently available:
33730 @item @file{elinos.py}
33732 @cindex ELinOS system-wide configuration script
33733 This script is useful when debugging a program on an ELinOS target.
33734 It takes advantage of the environment variables defined in a standard
33735 ELinOS environment in order to determine the location of the system
33736 shared libraries, and then sets the @samp{solib-absolute-prefix}
33737 and @samp{solib-search-path} variables appropriately.
33739 @item @file{wrs-linux.py}
33740 @pindex wrs-linux.py
33741 @cindex Wind River Linux system-wide configuration script
33742 This script is useful when debugging a program on a target running
33743 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33744 the host-side sysroot used by the target system.
33748 @node Maintenance Commands
33749 @appendix Maintenance Commands
33750 @cindex maintenance commands
33751 @cindex internal commands
33753 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33754 includes a number of commands intended for @value{GDBN} developers,
33755 that are not documented elsewhere in this manual. These commands are
33756 provided here for reference. (For commands that turn on debugging
33757 messages, see @ref{Debugging Output}.)
33760 @kindex maint agent
33761 @kindex maint agent-eval
33762 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33763 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33764 Translate the given @var{expression} into remote agent bytecodes.
33765 This command is useful for debugging the Agent Expression mechanism
33766 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33767 expression useful for data collection, such as by tracepoints, while
33768 @samp{maint agent-eval} produces an expression that evaluates directly
33769 to a result. For instance, a collection expression for @code{globa +
33770 globb} will include bytecodes to record four bytes of memory at each
33771 of the addresses of @code{globa} and @code{globb}, while discarding
33772 the result of the addition, while an evaluation expression will do the
33773 addition and return the sum.
33774 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33775 If not, generate remote agent bytecode for current frame PC address.
33777 @kindex maint agent-printf
33778 @item maint agent-printf @var{format},@var{expr},...
33779 Translate the given format string and list of argument expressions
33780 into remote agent bytecodes and display them as a disassembled list.
33781 This command is useful for debugging the agent version of dynamic
33782 printf (@pxref{Dynamic Printf}).
33784 @kindex maint info breakpoints
33785 @item @anchor{maint info breakpoints}maint info breakpoints
33786 Using the same format as @samp{info breakpoints}, display both the
33787 breakpoints you've set explicitly, and those @value{GDBN} is using for
33788 internal purposes. Internal breakpoints are shown with negative
33789 breakpoint numbers. The type column identifies what kind of breakpoint
33794 Normal, explicitly set breakpoint.
33797 Normal, explicitly set watchpoint.
33800 Internal breakpoint, used to handle correctly stepping through
33801 @code{longjmp} calls.
33803 @item longjmp resume
33804 Internal breakpoint at the target of a @code{longjmp}.
33807 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33810 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33813 Shared library events.
33817 @kindex maint info btrace
33818 @item maint info btrace
33819 Pint information about raw branch tracing data.
33821 @kindex maint btrace packet-history
33822 @item maint btrace packet-history
33823 Print the raw branch trace packets that are used to compute the
33824 execution history for the @samp{record btrace} command. Both the
33825 information and the format in which it is printed depend on the btrace
33830 For the BTS recording format, print a list of blocks of sequential
33831 code. For each block, the following information is printed:
33835 Newer blocks have higher numbers. The oldest block has number zero.
33836 @item Lowest @samp{PC}
33837 @item Highest @samp{PC}
33841 For the Intel(R) Processor Trace recording format, print a list of
33842 Intel(R) Processor Trace packets. For each packet, the following
33843 information is printed:
33846 @item Packet number
33847 Newer packets have higher numbers. The oldest packet has number zero.
33849 The packet's offset in the trace stream.
33850 @item Packet opcode and payload
33854 @kindex maint btrace clear-packet-history
33855 @item maint btrace clear-packet-history
33856 Discards the cached packet history printed by the @samp{maint btrace
33857 packet-history} command. The history will be computed again when
33860 @kindex maint btrace clear
33861 @item maint btrace clear
33862 Discard the branch trace data. The data will be fetched anew and the
33863 branch trace will be recomputed when needed.
33865 This implicitly truncates the branch trace to a single branch trace
33866 buffer. When updating branch trace incrementally, the branch trace
33867 available to @value{GDBN} may be bigger than a single branch trace
33870 @kindex maint set btrace pt skip-pad
33871 @item maint set btrace pt skip-pad
33872 @kindex maint show btrace pt skip-pad
33873 @item maint show btrace pt skip-pad
33874 Control whether @value{GDBN} will skip PAD packets when computing the
33877 @kindex set displaced-stepping
33878 @kindex show displaced-stepping
33879 @cindex displaced stepping support
33880 @cindex out-of-line single-stepping
33881 @item set displaced-stepping
33882 @itemx show displaced-stepping
33883 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33884 if the target supports it. Displaced stepping is a way to single-step
33885 over breakpoints without removing them from the inferior, by executing
33886 an out-of-line copy of the instruction that was originally at the
33887 breakpoint location. It is also known as out-of-line single-stepping.
33890 @item set displaced-stepping on
33891 If the target architecture supports it, @value{GDBN} will use
33892 displaced stepping to step over breakpoints.
33894 @item set displaced-stepping off
33895 @value{GDBN} will not use displaced stepping to step over breakpoints,
33896 even if such is supported by the target architecture.
33898 @cindex non-stop mode, and @samp{set displaced-stepping}
33899 @item set displaced-stepping auto
33900 This is the default mode. @value{GDBN} will use displaced stepping
33901 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33902 architecture supports displaced stepping.
33905 @kindex maint check-psymtabs
33906 @item maint check-psymtabs
33907 Check the consistency of currently expanded psymtabs versus symtabs.
33908 Use this to check, for example, whether a symbol is in one but not the other.
33910 @kindex maint check-symtabs
33911 @item maint check-symtabs
33912 Check the consistency of currently expanded symtabs.
33914 @kindex maint expand-symtabs
33915 @item maint expand-symtabs [@var{regexp}]
33916 Expand symbol tables.
33917 If @var{regexp} is specified, only expand symbol tables for file
33918 names matching @var{regexp}.
33920 @kindex maint set catch-demangler-crashes
33921 @kindex maint show catch-demangler-crashes
33922 @cindex demangler crashes
33923 @item maint set catch-demangler-crashes [on|off]
33924 @itemx maint show catch-demangler-crashes
33925 Control whether @value{GDBN} should attempt to catch crashes in the
33926 symbol name demangler. The default is to attempt to catch crashes.
33927 If enabled, the first time a crash is caught, a core file is created,
33928 the offending symbol is displayed and the user is presented with the
33929 option to terminate the current session.
33931 @kindex maint cplus first_component
33932 @item maint cplus first_component @var{name}
33933 Print the first C@t{++} class/namespace component of @var{name}.
33935 @kindex maint cplus namespace
33936 @item maint cplus namespace
33937 Print the list of possible C@t{++} namespaces.
33939 @kindex maint deprecate
33940 @kindex maint undeprecate
33941 @cindex deprecated commands
33942 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33943 @itemx maint undeprecate @var{command}
33944 Deprecate or undeprecate the named @var{command}. Deprecated commands
33945 cause @value{GDBN} to issue a warning when you use them. The optional
33946 argument @var{replacement} says which newer command should be used in
33947 favor of the deprecated one; if it is given, @value{GDBN} will mention
33948 the replacement as part of the warning.
33950 @kindex maint dump-me
33951 @item maint dump-me
33952 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33953 Cause a fatal signal in the debugger and force it to dump its core.
33954 This is supported only on systems which support aborting a program
33955 with the @code{SIGQUIT} signal.
33957 @kindex maint internal-error
33958 @kindex maint internal-warning
33959 @kindex maint demangler-warning
33960 @cindex demangler crashes
33961 @item maint internal-error @r{[}@var{message-text}@r{]}
33962 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33963 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
33965 Cause @value{GDBN} to call the internal function @code{internal_error},
33966 @code{internal_warning} or @code{demangler_warning} and hence behave
33967 as though an internal problem has been detected. In addition to
33968 reporting the internal problem, these functions give the user the
33969 opportunity to either quit @value{GDBN} or (for @code{internal_error}
33970 and @code{internal_warning}) create a core file of the current
33971 @value{GDBN} session.
33973 These commands take an optional parameter @var{message-text} that is
33974 used as the text of the error or warning message.
33976 Here's an example of using @code{internal-error}:
33979 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33980 @dots{}/maint.c:121: internal-error: testing, 1, 2
33981 A problem internal to GDB has been detected. Further
33982 debugging may prove unreliable.
33983 Quit this debugging session? (y or n) @kbd{n}
33984 Create a core file? (y or n) @kbd{n}
33988 @cindex @value{GDBN} internal error
33989 @cindex internal errors, control of @value{GDBN} behavior
33990 @cindex demangler crashes
33992 @kindex maint set internal-error
33993 @kindex maint show internal-error
33994 @kindex maint set internal-warning
33995 @kindex maint show internal-warning
33996 @kindex maint set demangler-warning
33997 @kindex maint show demangler-warning
33998 @item maint set internal-error @var{action} [ask|yes|no]
33999 @itemx maint show internal-error @var{action}
34000 @itemx maint set internal-warning @var{action} [ask|yes|no]
34001 @itemx maint show internal-warning @var{action}
34002 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34003 @itemx maint show demangler-warning @var{action}
34004 When @value{GDBN} reports an internal problem (error or warning) it
34005 gives the user the opportunity to both quit @value{GDBN} and create a
34006 core file of the current @value{GDBN} session. These commands let you
34007 override the default behaviour for each particular @var{action},
34008 described in the table below.
34012 You can specify that @value{GDBN} should always (yes) or never (no)
34013 quit. The default is to ask the user what to do.
34016 You can specify that @value{GDBN} should always (yes) or never (no)
34017 create a core file. The default is to ask the user what to do. Note
34018 that there is no @code{corefile} option for @code{demangler-warning}:
34019 demangler warnings always create a core file and this cannot be
34023 @kindex maint packet
34024 @item maint packet @var{text}
34025 If @value{GDBN} is talking to an inferior via the serial protocol,
34026 then this command sends the string @var{text} to the inferior, and
34027 displays the response packet. @value{GDBN} supplies the initial
34028 @samp{$} character, the terminating @samp{#} character, and the
34031 @kindex maint print architecture
34032 @item maint print architecture @r{[}@var{file}@r{]}
34033 Print the entire architecture configuration. The optional argument
34034 @var{file} names the file where the output goes.
34036 @kindex maint print c-tdesc
34037 @item maint print c-tdesc
34038 Print the current target description (@pxref{Target Descriptions}) as
34039 a C source file. The created source file can be used in @value{GDBN}
34040 when an XML parser is not available to parse the description.
34042 @kindex maint print dummy-frames
34043 @item maint print dummy-frames
34044 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34047 (@value{GDBP}) @kbd{b add}
34049 (@value{GDBP}) @kbd{print add(2,3)}
34050 Breakpoint 2, add (a=2, b=3) at @dots{}
34052 The program being debugged stopped while in a function called from GDB.
34054 (@value{GDBP}) @kbd{maint print dummy-frames}
34055 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34059 Takes an optional file parameter.
34061 @kindex maint print registers
34062 @kindex maint print raw-registers
34063 @kindex maint print cooked-registers
34064 @kindex maint print register-groups
34065 @kindex maint print remote-registers
34066 @item maint print registers @r{[}@var{file}@r{]}
34067 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34068 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34069 @itemx maint print register-groups @r{[}@var{file}@r{]}
34070 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34071 Print @value{GDBN}'s internal register data structures.
34073 The command @code{maint print raw-registers} includes the contents of
34074 the raw register cache; the command @code{maint print
34075 cooked-registers} includes the (cooked) value of all registers,
34076 including registers which aren't available on the target nor visible
34077 to user; the command @code{maint print register-groups} includes the
34078 groups that each register is a member of; and the command @code{maint
34079 print remote-registers} includes the remote target's register numbers
34080 and offsets in the `G' packets.
34082 These commands take an optional parameter, a file name to which to
34083 write the information.
34085 @kindex maint print reggroups
34086 @item maint print reggroups @r{[}@var{file}@r{]}
34087 Print @value{GDBN}'s internal register group data structures. The
34088 optional argument @var{file} tells to what file to write the
34091 The register groups info looks like this:
34094 (@value{GDBP}) @kbd{maint print reggroups}
34107 This command forces @value{GDBN} to flush its internal register cache.
34109 @kindex maint print objfiles
34110 @cindex info for known object files
34111 @item maint print objfiles @r{[}@var{regexp}@r{]}
34112 Print a dump of all known object files.
34113 If @var{regexp} is specified, only print object files whose names
34114 match @var{regexp}. For each object file, this command prints its name,
34115 address in memory, and all of its psymtabs and symtabs.
34117 @kindex maint print user-registers
34118 @cindex user registers
34119 @item maint print user-registers
34120 List all currently available @dfn{user registers}. User registers
34121 typically provide alternate names for actual hardware registers. They
34122 include the four ``standard'' registers @code{$fp}, @code{$pc},
34123 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34124 registers can be used in expressions in the same way as the canonical
34125 register names, but only the latter are listed by the @code{info
34126 registers} and @code{maint print registers} commands.
34128 @kindex maint print section-scripts
34129 @cindex info for known .debug_gdb_scripts-loaded scripts
34130 @item maint print section-scripts [@var{regexp}]
34131 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34132 If @var{regexp} is specified, only print scripts loaded by object files
34133 matching @var{regexp}.
34134 For each script, this command prints its name as specified in the objfile,
34135 and the full path if known.
34136 @xref{dotdebug_gdb_scripts section}.
34138 @kindex maint print statistics
34139 @cindex bcache statistics
34140 @item maint print statistics
34141 This command prints, for each object file in the program, various data
34142 about that object file followed by the byte cache (@dfn{bcache})
34143 statistics for the object file. The objfile data includes the number
34144 of minimal, partial, full, and stabs symbols, the number of types
34145 defined by the objfile, the number of as yet unexpanded psym tables,
34146 the number of line tables and string tables, and the amount of memory
34147 used by the various tables. The bcache statistics include the counts,
34148 sizes, and counts of duplicates of all and unique objects, max,
34149 average, and median entry size, total memory used and its overhead and
34150 savings, and various measures of the hash table size and chain
34153 @kindex maint print target-stack
34154 @cindex target stack description
34155 @item maint print target-stack
34156 A @dfn{target} is an interface between the debugger and a particular
34157 kind of file or process. Targets can be stacked in @dfn{strata},
34158 so that more than one target can potentially respond to a request.
34159 In particular, memory accesses will walk down the stack of targets
34160 until they find a target that is interested in handling that particular
34163 This command prints a short description of each layer that was pushed on
34164 the @dfn{target stack}, starting from the top layer down to the bottom one.
34166 @kindex maint print type
34167 @cindex type chain of a data type
34168 @item maint print type @var{expr}
34169 Print the type chain for a type specified by @var{expr}. The argument
34170 can be either a type name or a symbol. If it is a symbol, the type of
34171 that symbol is described. The type chain produced by this command is
34172 a recursive definition of the data type as stored in @value{GDBN}'s
34173 data structures, including its flags and contained types.
34175 @kindex maint set dwarf always-disassemble
34176 @kindex maint show dwarf always-disassemble
34177 @item maint set dwarf always-disassemble
34178 @item maint show dwarf always-disassemble
34179 Control the behavior of @code{info address} when using DWARF debugging
34182 The default is @code{off}, which means that @value{GDBN} should try to
34183 describe a variable's location in an easily readable format. When
34184 @code{on}, @value{GDBN} will instead display the DWARF location
34185 expression in an assembly-like format. Note that some locations are
34186 too complex for @value{GDBN} to describe simply; in this case you will
34187 always see the disassembly form.
34189 Here is an example of the resulting disassembly:
34192 (gdb) info addr argc
34193 Symbol "argc" is a complex DWARF expression:
34197 For more information on these expressions, see
34198 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34200 @kindex maint set dwarf max-cache-age
34201 @kindex maint show dwarf max-cache-age
34202 @item maint set dwarf max-cache-age
34203 @itemx maint show dwarf max-cache-age
34204 Control the DWARF compilation unit cache.
34206 @cindex DWARF compilation units cache
34207 In object files with inter-compilation-unit references, such as those
34208 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34209 reader needs to frequently refer to previously read compilation units.
34210 This setting controls how long a compilation unit will remain in the
34211 cache if it is not referenced. A higher limit means that cached
34212 compilation units will be stored in memory longer, and more total
34213 memory will be used. Setting it to zero disables caching, which will
34214 slow down @value{GDBN} startup, but reduce memory consumption.
34216 @kindex maint set profile
34217 @kindex maint show profile
34218 @cindex profiling GDB
34219 @item maint set profile
34220 @itemx maint show profile
34221 Control profiling of @value{GDBN}.
34223 Profiling will be disabled until you use the @samp{maint set profile}
34224 command to enable it. When you enable profiling, the system will begin
34225 collecting timing and execution count data; when you disable profiling or
34226 exit @value{GDBN}, the results will be written to a log file. Remember that
34227 if you use profiling, @value{GDBN} will overwrite the profiling log file
34228 (often called @file{gmon.out}). If you have a record of important profiling
34229 data in a @file{gmon.out} file, be sure to move it to a safe location.
34231 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34232 compiled with the @samp{-pg} compiler option.
34234 @kindex maint set show-debug-regs
34235 @kindex maint show show-debug-regs
34236 @cindex hardware debug registers
34237 @item maint set show-debug-regs
34238 @itemx maint show show-debug-regs
34239 Control whether to show variables that mirror the hardware debug
34240 registers. Use @code{on} to enable, @code{off} to disable. If
34241 enabled, the debug registers values are shown when @value{GDBN} inserts or
34242 removes a hardware breakpoint or watchpoint, and when the inferior
34243 triggers a hardware-assisted breakpoint or watchpoint.
34245 @kindex maint set show-all-tib
34246 @kindex maint show show-all-tib
34247 @item maint set show-all-tib
34248 @itemx maint show show-all-tib
34249 Control whether to show all non zero areas within a 1k block starting
34250 at thread local base, when using the @samp{info w32 thread-information-block}
34253 @kindex maint set target-async
34254 @kindex maint show target-async
34255 @item maint set target-async
34256 @itemx maint show target-async
34257 This controls whether @value{GDBN} targets operate in synchronous or
34258 asynchronous mode (@pxref{Background Execution}). Normally the
34259 default is asynchronous, if it is available; but this can be changed
34260 to more easily debug problems occurring only in synchronous mode.
34262 @kindex maint set target-non-stop @var{mode} [on|off|auto]
34263 @kindex maint show target-non-stop
34264 @item maint set target-non-stop
34265 @itemx maint show target-non-stop
34267 This controls whether @value{GDBN} targets always operate in non-stop
34268 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
34269 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
34270 if supported by the target.
34273 @item maint set target-non-stop auto
34274 This is the default mode. @value{GDBN} controls the target in
34275 non-stop mode if the target supports it.
34277 @item maint set target-non-stop on
34278 @value{GDBN} controls the target in non-stop mode even if the target
34279 does not indicate support.
34281 @item maint set target-non-stop off
34282 @value{GDBN} does not control the target in non-stop mode even if the
34283 target supports it.
34286 @kindex maint set per-command
34287 @kindex maint show per-command
34288 @item maint set per-command
34289 @itemx maint show per-command
34290 @cindex resources used by commands
34292 @value{GDBN} can display the resources used by each command.
34293 This is useful in debugging performance problems.
34296 @item maint set per-command space [on|off]
34297 @itemx maint show per-command space
34298 Enable or disable the printing of the memory used by GDB for each command.
34299 If enabled, @value{GDBN} will display how much memory each command
34300 took, following the command's own output.
34301 This can also be requested by invoking @value{GDBN} with the
34302 @option{--statistics} command-line switch (@pxref{Mode Options}).
34304 @item maint set per-command time [on|off]
34305 @itemx maint show per-command time
34306 Enable or disable the printing of the execution time of @value{GDBN}
34308 If enabled, @value{GDBN} will display how much time it
34309 took to execute each command, following the command's own output.
34310 Both CPU time and wallclock time are printed.
34311 Printing both is useful when trying to determine whether the cost is
34312 CPU or, e.g., disk/network latency.
34313 Note that the CPU time printed is for @value{GDBN} only, it does not include
34314 the execution time of the inferior because there's no mechanism currently
34315 to compute how much time was spent by @value{GDBN} and how much time was
34316 spent by the program been debugged.
34317 This can also be requested by invoking @value{GDBN} with the
34318 @option{--statistics} command-line switch (@pxref{Mode Options}).
34320 @item maint set per-command symtab [on|off]
34321 @itemx maint show per-command symtab
34322 Enable or disable the printing of basic symbol table statistics
34324 If enabled, @value{GDBN} will display the following information:
34328 number of symbol tables
34330 number of primary symbol tables
34332 number of blocks in the blockvector
34336 @kindex maint space
34337 @cindex memory used by commands
34338 @item maint space @var{value}
34339 An alias for @code{maint set per-command space}.
34340 A non-zero value enables it, zero disables it.
34343 @cindex time of command execution
34344 @item maint time @var{value}
34345 An alias for @code{maint set per-command time}.
34346 A non-zero value enables it, zero disables it.
34348 @kindex maint translate-address
34349 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34350 Find the symbol stored at the location specified by the address
34351 @var{addr} and an optional section name @var{section}. If found,
34352 @value{GDBN} prints the name of the closest symbol and an offset from
34353 the symbol's location to the specified address. This is similar to
34354 the @code{info address} command (@pxref{Symbols}), except that this
34355 command also allows to find symbols in other sections.
34357 If section was not specified, the section in which the symbol was found
34358 is also printed. For dynamically linked executables, the name of
34359 executable or shared library containing the symbol is printed as well.
34363 The following command is useful for non-interactive invocations of
34364 @value{GDBN}, such as in the test suite.
34367 @item set watchdog @var{nsec}
34368 @kindex set watchdog
34369 @cindex watchdog timer
34370 @cindex timeout for commands
34371 Set the maximum number of seconds @value{GDBN} will wait for the
34372 target operation to finish. If this time expires, @value{GDBN}
34373 reports and error and the command is aborted.
34375 @item show watchdog
34376 Show the current setting of the target wait timeout.
34379 @node Remote Protocol
34380 @appendix @value{GDBN} Remote Serial Protocol
34385 * Stop Reply Packets::
34386 * General Query Packets::
34387 * Architecture-Specific Protocol Details::
34388 * Tracepoint Packets::
34389 * Host I/O Packets::
34391 * Notification Packets::
34392 * Remote Non-Stop::
34393 * Packet Acknowledgment::
34395 * File-I/O Remote Protocol Extension::
34396 * Library List Format::
34397 * Library List Format for SVR4 Targets::
34398 * Memory Map Format::
34399 * Thread List Format::
34400 * Traceframe Info Format::
34401 * Branch Trace Format::
34402 * Branch Trace Configuration Format::
34408 There may be occasions when you need to know something about the
34409 protocol---for example, if there is only one serial port to your target
34410 machine, you might want your program to do something special if it
34411 recognizes a packet meant for @value{GDBN}.
34413 In the examples below, @samp{->} and @samp{<-} are used to indicate
34414 transmitted and received data, respectively.
34416 @cindex protocol, @value{GDBN} remote serial
34417 @cindex serial protocol, @value{GDBN} remote
34418 @cindex remote serial protocol
34419 All @value{GDBN} commands and responses (other than acknowledgments
34420 and notifications, see @ref{Notification Packets}) are sent as a
34421 @var{packet}. A @var{packet} is introduced with the character
34422 @samp{$}, the actual @var{packet-data}, and the terminating character
34423 @samp{#} followed by a two-digit @var{checksum}:
34426 @code{$}@var{packet-data}@code{#}@var{checksum}
34430 @cindex checksum, for @value{GDBN} remote
34432 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34433 characters between the leading @samp{$} and the trailing @samp{#} (an
34434 eight bit unsigned checksum).
34436 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34437 specification also included an optional two-digit @var{sequence-id}:
34440 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34443 @cindex sequence-id, for @value{GDBN} remote
34445 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34446 has never output @var{sequence-id}s. Stubs that handle packets added
34447 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34449 When either the host or the target machine receives a packet, the first
34450 response expected is an acknowledgment: either @samp{+} (to indicate
34451 the package was received correctly) or @samp{-} (to request
34455 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34460 The @samp{+}/@samp{-} acknowledgments can be disabled
34461 once a connection is established.
34462 @xref{Packet Acknowledgment}, for details.
34464 The host (@value{GDBN}) sends @var{command}s, and the target (the
34465 debugging stub incorporated in your program) sends a @var{response}. In
34466 the case of step and continue @var{command}s, the response is only sent
34467 when the operation has completed, and the target has again stopped all
34468 threads in all attached processes. This is the default all-stop mode
34469 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34470 execution mode; see @ref{Remote Non-Stop}, for details.
34472 @var{packet-data} consists of a sequence of characters with the
34473 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34476 @cindex remote protocol, field separator
34477 Fields within the packet should be separated using @samp{,} @samp{;} or
34478 @samp{:}. Except where otherwise noted all numbers are represented in
34479 @sc{hex} with leading zeros suppressed.
34481 Implementors should note that prior to @value{GDBN} 5.0, the character
34482 @samp{:} could not appear as the third character in a packet (as it
34483 would potentially conflict with the @var{sequence-id}).
34485 @cindex remote protocol, binary data
34486 @anchor{Binary Data}
34487 Binary data in most packets is encoded either as two hexadecimal
34488 digits per byte of binary data. This allowed the traditional remote
34489 protocol to work over connections which were only seven-bit clean.
34490 Some packets designed more recently assume an eight-bit clean
34491 connection, and use a more efficient encoding to send and receive
34494 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34495 as an escape character. Any escaped byte is transmitted as the escape
34496 character followed by the original character XORed with @code{0x20}.
34497 For example, the byte @code{0x7d} would be transmitted as the two
34498 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34499 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34500 @samp{@}}) must always be escaped. Responses sent by the stub
34501 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34502 is not interpreted as the start of a run-length encoded sequence
34505 Response @var{data} can be run-length encoded to save space.
34506 Run-length encoding replaces runs of identical characters with one
34507 instance of the repeated character, followed by a @samp{*} and a
34508 repeat count. The repeat count is itself sent encoded, to avoid
34509 binary characters in @var{data}: a value of @var{n} is sent as
34510 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34511 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34512 code 32) for a repeat count of 3. (This is because run-length
34513 encoding starts to win for counts 3 or more.) Thus, for example,
34514 @samp{0* } is a run-length encoding of ``0000'': the space character
34515 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34518 The printable characters @samp{#} and @samp{$} or with a numeric value
34519 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34520 seven repeats (@samp{$}) can be expanded using a repeat count of only
34521 five (@samp{"}). For example, @samp{00000000} can be encoded as
34524 The error response returned for some packets includes a two character
34525 error number. That number is not well defined.
34527 @cindex empty response, for unsupported packets
34528 For any @var{command} not supported by the stub, an empty response
34529 (@samp{$#00}) should be returned. That way it is possible to extend the
34530 protocol. A newer @value{GDBN} can tell if a packet is supported based
34533 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34534 commands for register access, and the @samp{m} and @samp{M} commands
34535 for memory access. Stubs that only control single-threaded targets
34536 can implement run control with the @samp{c} (continue), and @samp{s}
34537 (step) commands. Stubs that support multi-threading targets should
34538 support the @samp{vCont} command. All other commands are optional.
34543 The following table provides a complete list of all currently defined
34544 @var{command}s and their corresponding response @var{data}.
34545 @xref{File-I/O Remote Protocol Extension}, for details about the File
34546 I/O extension of the remote protocol.
34548 Each packet's description has a template showing the packet's overall
34549 syntax, followed by an explanation of the packet's meaning. We
34550 include spaces in some of the templates for clarity; these are not
34551 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34552 separate its components. For example, a template like @samp{foo
34553 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34554 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34555 @var{baz}. @value{GDBN} does not transmit a space character between the
34556 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34559 @cindex @var{thread-id}, in remote protocol
34560 @anchor{thread-id syntax}
34561 Several packets and replies include a @var{thread-id} field to identify
34562 a thread. Normally these are positive numbers with a target-specific
34563 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34564 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34567 In addition, the remote protocol supports a multiprocess feature in
34568 which the @var{thread-id} syntax is extended to optionally include both
34569 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34570 The @var{pid} (process) and @var{tid} (thread) components each have the
34571 format described above: a positive number with target-specific
34572 interpretation formatted as a big-endian hex string, literal @samp{-1}
34573 to indicate all processes or threads (respectively), or @samp{0} to
34574 indicate an arbitrary process or thread. Specifying just a process, as
34575 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34576 error to specify all processes but a specific thread, such as
34577 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34578 for those packets and replies explicitly documented to include a process
34579 ID, rather than a @var{thread-id}.
34581 The multiprocess @var{thread-id} syntax extensions are only used if both
34582 @value{GDBN} and the stub report support for the @samp{multiprocess}
34583 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34586 Note that all packet forms beginning with an upper- or lower-case
34587 letter, other than those described here, are reserved for future use.
34589 Here are the packet descriptions.
34594 @cindex @samp{!} packet
34595 @anchor{extended mode}
34596 Enable extended mode. In extended mode, the remote server is made
34597 persistent. The @samp{R} packet is used to restart the program being
34603 The remote target both supports and has enabled extended mode.
34607 @cindex @samp{?} packet
34609 Indicate the reason the target halted. The reply is the same as for
34610 step and continue. This packet has a special interpretation when the
34611 target is in non-stop mode; see @ref{Remote Non-Stop}.
34614 @xref{Stop Reply Packets}, for the reply specifications.
34616 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34617 @cindex @samp{A} packet
34618 Initialized @code{argv[]} array passed into program. @var{arglen}
34619 specifies the number of bytes in the hex encoded byte stream
34620 @var{arg}. See @code{gdbserver} for more details.
34625 The arguments were set.
34631 @cindex @samp{b} packet
34632 (Don't use this packet; its behavior is not well-defined.)
34633 Change the serial line speed to @var{baud}.
34635 JTC: @emph{When does the transport layer state change? When it's
34636 received, or after the ACK is transmitted. In either case, there are
34637 problems if the command or the acknowledgment packet is dropped.}
34639 Stan: @emph{If people really wanted to add something like this, and get
34640 it working for the first time, they ought to modify ser-unix.c to send
34641 some kind of out-of-band message to a specially-setup stub and have the
34642 switch happen "in between" packets, so that from remote protocol's point
34643 of view, nothing actually happened.}
34645 @item B @var{addr},@var{mode}
34646 @cindex @samp{B} packet
34647 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34648 breakpoint at @var{addr}.
34650 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34651 (@pxref{insert breakpoint or watchpoint packet}).
34653 @cindex @samp{bc} packet
34656 Backward continue. Execute the target system in reverse. No parameter.
34657 @xref{Reverse Execution}, for more information.
34660 @xref{Stop Reply Packets}, for the reply specifications.
34662 @cindex @samp{bs} packet
34665 Backward single step. Execute one instruction in reverse. No parameter.
34666 @xref{Reverse Execution}, for more information.
34669 @xref{Stop Reply Packets}, for the reply specifications.
34671 @item c @r{[}@var{addr}@r{]}
34672 @cindex @samp{c} packet
34673 Continue at @var{addr}, which is the address to resume. If @var{addr}
34674 is omitted, resume at current address.
34676 This packet is deprecated for multi-threading support. @xref{vCont
34680 @xref{Stop Reply Packets}, for the reply specifications.
34682 @item C @var{sig}@r{[};@var{addr}@r{]}
34683 @cindex @samp{C} packet
34684 Continue with signal @var{sig} (hex signal number). If
34685 @samp{;@var{addr}} is omitted, resume at same address.
34687 This packet is deprecated for multi-threading support. @xref{vCont
34691 @xref{Stop Reply Packets}, for the reply specifications.
34694 @cindex @samp{d} packet
34697 Don't use this packet; instead, define a general set packet
34698 (@pxref{General Query Packets}).
34702 @cindex @samp{D} packet
34703 The first form of the packet is used to detach @value{GDBN} from the
34704 remote system. It is sent to the remote target
34705 before @value{GDBN} disconnects via the @code{detach} command.
34707 The second form, including a process ID, is used when multiprocess
34708 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34709 detach only a specific process. The @var{pid} is specified as a
34710 big-endian hex string.
34720 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34721 @cindex @samp{F} packet
34722 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34723 This is part of the File-I/O protocol extension. @xref{File-I/O
34724 Remote Protocol Extension}, for the specification.
34727 @anchor{read registers packet}
34728 @cindex @samp{g} packet
34729 Read general registers.
34733 @item @var{XX@dots{}}
34734 Each byte of register data is described by two hex digits. The bytes
34735 with the register are transmitted in target byte order. The size of
34736 each register and their position within the @samp{g} packet are
34737 determined by the @value{GDBN} internal gdbarch functions
34738 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34739 specification of several standard @samp{g} packets is specified below.
34741 When reading registers from a trace frame (@pxref{Analyze Collected
34742 Data,,Using the Collected Data}), the stub may also return a string of
34743 literal @samp{x}'s in place of the register data digits, to indicate
34744 that the corresponding register has not been collected, thus its value
34745 is unavailable. For example, for an architecture with 4 registers of
34746 4 bytes each, the following reply indicates to @value{GDBN} that
34747 registers 0 and 2 have not been collected, while registers 1 and 3
34748 have been collected, and both have zero value:
34752 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34759 @item G @var{XX@dots{}}
34760 @cindex @samp{G} packet
34761 Write general registers. @xref{read registers packet}, for a
34762 description of the @var{XX@dots{}} data.
34772 @item H @var{op} @var{thread-id}
34773 @cindex @samp{H} packet
34774 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34775 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34776 should be @samp{c} for step and continue operations (note that this
34777 is deprecated, supporting the @samp{vCont} command is a better
34778 option), and @samp{g} for other operations. The thread designator
34779 @var{thread-id} has the format and interpretation described in
34780 @ref{thread-id syntax}.
34791 @c 'H': How restrictive (or permissive) is the thread model. If a
34792 @c thread is selected and stopped, are other threads allowed
34793 @c to continue to execute? As I mentioned above, I think the
34794 @c semantics of each command when a thread is selected must be
34795 @c described. For example:
34797 @c 'g': If the stub supports threads and a specific thread is
34798 @c selected, returns the register block from that thread;
34799 @c otherwise returns current registers.
34801 @c 'G' If the stub supports threads and a specific thread is
34802 @c selected, sets the registers of the register block of
34803 @c that thread; otherwise sets current registers.
34805 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34806 @anchor{cycle step packet}
34807 @cindex @samp{i} packet
34808 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34809 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34810 step starting at that address.
34813 @cindex @samp{I} packet
34814 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34818 @cindex @samp{k} packet
34821 The exact effect of this packet is not specified.
34823 For a bare-metal target, it may power cycle or reset the target
34824 system. For that reason, the @samp{k} packet has no reply.
34826 For a single-process target, it may kill that process if possible.
34828 A multiple-process target may choose to kill just one process, or all
34829 that are under @value{GDBN}'s control. For more precise control, use
34830 the vKill packet (@pxref{vKill packet}).
34832 If the target system immediately closes the connection in response to
34833 @samp{k}, @value{GDBN} does not consider the lack of packet
34834 acknowledgment to be an error, and assumes the kill was successful.
34836 If connected using @kbd{target extended-remote}, and the target does
34837 not close the connection in response to a kill request, @value{GDBN}
34838 probes the target state as if a new connection was opened
34839 (@pxref{? packet}).
34841 @item m @var{addr},@var{length}
34842 @cindex @samp{m} packet
34843 Read @var{length} addressable memory units starting at address @var{addr}
34844 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
34845 any particular boundary.
34847 The stub need not use any particular size or alignment when gathering
34848 data from memory for the response; even if @var{addr} is word-aligned
34849 and @var{length} is a multiple of the word size, the stub is free to
34850 use byte accesses, or not. For this reason, this packet may not be
34851 suitable for accessing memory-mapped I/O devices.
34852 @cindex alignment of remote memory accesses
34853 @cindex size of remote memory accesses
34854 @cindex memory, alignment and size of remote accesses
34858 @item @var{XX@dots{}}
34859 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
34860 The reply may contain fewer addressable memory units than requested if the
34861 server was able to read only part of the region of memory.
34866 @item M @var{addr},@var{length}:@var{XX@dots{}}
34867 @cindex @samp{M} packet
34868 Write @var{length} addressable memory units starting at address @var{addr}
34869 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
34870 byte is transmitted as a two-digit hexadecimal number.
34877 for an error (this includes the case where only part of the data was
34882 @cindex @samp{p} packet
34883 Read the value of register @var{n}; @var{n} is in hex.
34884 @xref{read registers packet}, for a description of how the returned
34885 register value is encoded.
34889 @item @var{XX@dots{}}
34890 the register's value
34894 Indicating an unrecognized @var{query}.
34897 @item P @var{n@dots{}}=@var{r@dots{}}
34898 @anchor{write register packet}
34899 @cindex @samp{P} packet
34900 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34901 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34902 digits for each byte in the register (target byte order).
34912 @item q @var{name} @var{params}@dots{}
34913 @itemx Q @var{name} @var{params}@dots{}
34914 @cindex @samp{q} packet
34915 @cindex @samp{Q} packet
34916 General query (@samp{q}) and set (@samp{Q}). These packets are
34917 described fully in @ref{General Query Packets}.
34920 @cindex @samp{r} packet
34921 Reset the entire system.
34923 Don't use this packet; use the @samp{R} packet instead.
34926 @cindex @samp{R} packet
34927 Restart the program being debugged. The @var{XX}, while needed, is ignored.
34928 This packet is only available in extended mode (@pxref{extended mode}).
34930 The @samp{R} packet has no reply.
34932 @item s @r{[}@var{addr}@r{]}
34933 @cindex @samp{s} packet
34934 Single step, resuming at @var{addr}. If
34935 @var{addr} is omitted, resume at same address.
34937 This packet is deprecated for multi-threading support. @xref{vCont
34941 @xref{Stop Reply Packets}, for the reply specifications.
34943 @item S @var{sig}@r{[};@var{addr}@r{]}
34944 @anchor{step with signal packet}
34945 @cindex @samp{S} packet
34946 Step with signal. This is analogous to the @samp{C} packet, but
34947 requests a single-step, rather than a normal resumption of execution.
34949 This packet is deprecated for multi-threading support. @xref{vCont
34953 @xref{Stop Reply Packets}, for the reply specifications.
34955 @item t @var{addr}:@var{PP},@var{MM}
34956 @cindex @samp{t} packet
34957 Search backwards starting at address @var{addr} for a match with pattern
34958 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
34959 There must be at least 3 digits in @var{addr}.
34961 @item T @var{thread-id}
34962 @cindex @samp{T} packet
34963 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34968 thread is still alive
34974 Packets starting with @samp{v} are identified by a multi-letter name,
34975 up to the first @samp{;} or @samp{?} (or the end of the packet).
34977 @item vAttach;@var{pid}
34978 @cindex @samp{vAttach} packet
34979 Attach to a new process with the specified process ID @var{pid}.
34980 The process ID is a
34981 hexadecimal integer identifying the process. In all-stop mode, all
34982 threads in the attached process are stopped; in non-stop mode, it may be
34983 attached without being stopped if that is supported by the target.
34985 @c In non-stop mode, on a successful vAttach, the stub should set the
34986 @c current thread to a thread of the newly-attached process. After
34987 @c attaching, GDB queries for the attached process's thread ID with qC.
34988 @c Also note that, from a user perspective, whether or not the
34989 @c target is stopped on attach in non-stop mode depends on whether you
34990 @c use the foreground or background version of the attach command, not
34991 @c on what vAttach does; GDB does the right thing with respect to either
34992 @c stopping or restarting threads.
34994 This packet is only available in extended mode (@pxref{extended mode}).
35000 @item @r{Any stop packet}
35001 for success in all-stop mode (@pxref{Stop Reply Packets})
35003 for success in non-stop mode (@pxref{Remote Non-Stop})
35006 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35007 @cindex @samp{vCont} packet
35008 @anchor{vCont packet}
35009 Resume the inferior, specifying different actions for each thread.
35010 If an action is specified with no @var{thread-id}, then it is applied to any
35011 threads that don't have a specific action specified; if no default action is
35012 specified then other threads should remain stopped in all-stop mode and
35013 in their current state in non-stop mode.
35014 Specifying multiple
35015 default actions is an error; specifying no actions is also an error.
35016 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
35018 Currently supported actions are:
35024 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35028 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35031 @item r @var{start},@var{end}
35032 Step once, and then keep stepping as long as the thread stops at
35033 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35034 The remote stub reports a stop reply when either the thread goes out
35035 of the range or is stopped due to an unrelated reason, such as hitting
35036 a breakpoint. @xref{range stepping}.
35038 If the range is empty (@var{start} == @var{end}), then the action
35039 becomes equivalent to the @samp{s} action. In other words,
35040 single-step once, and report the stop (even if the stepped instruction
35041 jumps to @var{start}).
35043 (A stop reply may be sent at any point even if the PC is still within
35044 the stepping range; for example, it is valid to implement this packet
35045 in a degenerate way as a single instruction step operation.)
35049 The optional argument @var{addr} normally associated with the
35050 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35051 not supported in @samp{vCont}.
35053 The @samp{t} action is only relevant in non-stop mode
35054 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35055 A stop reply should be generated for any affected thread not already stopped.
35056 When a thread is stopped by means of a @samp{t} action,
35057 the corresponding stop reply should indicate that the thread has stopped with
35058 signal @samp{0}, regardless of whether the target uses some other signal
35059 as an implementation detail.
35061 The stub must support @samp{vCont} if it reports support for
35062 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
35063 this case @samp{vCont} actions can be specified to apply to all threads
35064 in a process by using the @samp{p@var{pid}.-1} form of the
35068 @xref{Stop Reply Packets}, for the reply specifications.
35071 @cindex @samp{vCont?} packet
35072 Request a list of actions supported by the @samp{vCont} packet.
35076 @item vCont@r{[};@var{action}@dots{}@r{]}
35077 The @samp{vCont} packet is supported. Each @var{action} is a supported
35078 command in the @samp{vCont} packet.
35080 The @samp{vCont} packet is not supported.
35083 @item vFile:@var{operation}:@var{parameter}@dots{}
35084 @cindex @samp{vFile} packet
35085 Perform a file operation on the target system. For details,
35086 see @ref{Host I/O Packets}.
35088 @item vFlashErase:@var{addr},@var{length}
35089 @cindex @samp{vFlashErase} packet
35090 Direct the stub to erase @var{length} bytes of flash starting at
35091 @var{addr}. The region may enclose any number of flash blocks, but
35092 its start and end must fall on block boundaries, as indicated by the
35093 flash block size appearing in the memory map (@pxref{Memory Map
35094 Format}). @value{GDBN} groups flash memory programming operations
35095 together, and sends a @samp{vFlashDone} request after each group; the
35096 stub is allowed to delay erase operation until the @samp{vFlashDone}
35097 packet is received.
35107 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35108 @cindex @samp{vFlashWrite} packet
35109 Direct the stub to write data to flash address @var{addr}. The data
35110 is passed in binary form using the same encoding as for the @samp{X}
35111 packet (@pxref{Binary Data}). The memory ranges specified by
35112 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35113 not overlap, and must appear in order of increasing addresses
35114 (although @samp{vFlashErase} packets for higher addresses may already
35115 have been received; the ordering is guaranteed only between
35116 @samp{vFlashWrite} packets). If a packet writes to an address that was
35117 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35118 target-specific method, the results are unpredictable.
35126 for vFlashWrite addressing non-flash memory
35132 @cindex @samp{vFlashDone} packet
35133 Indicate to the stub that flash programming operation is finished.
35134 The stub is permitted to delay or batch the effects of a group of
35135 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35136 @samp{vFlashDone} packet is received. The contents of the affected
35137 regions of flash memory are unpredictable until the @samp{vFlashDone}
35138 request is completed.
35140 @item vKill;@var{pid}
35141 @cindex @samp{vKill} packet
35142 @anchor{vKill packet}
35143 Kill the process with the specified process ID @var{pid}, which is a
35144 hexadecimal integer identifying the process. This packet is used in
35145 preference to @samp{k} when multiprocess protocol extensions are
35146 supported; see @ref{multiprocess extensions}.
35156 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35157 @cindex @samp{vRun} packet
35158 Run the program @var{filename}, passing it each @var{argument} on its
35159 command line. The file and arguments are hex-encoded strings. If
35160 @var{filename} is an empty string, the stub may use a default program
35161 (e.g.@: the last program run). The program is created in the stopped
35164 @c FIXME: What about non-stop mode?
35166 This packet is only available in extended mode (@pxref{extended mode}).
35172 @item @r{Any stop packet}
35173 for success (@pxref{Stop Reply Packets})
35177 @cindex @samp{vStopped} packet
35178 @xref{Notification Packets}.
35180 @item X @var{addr},@var{length}:@var{XX@dots{}}
35182 @cindex @samp{X} packet
35183 Write data to memory, where the data is transmitted in binary.
35184 Memory is specified by its address @var{addr} and number of addressable memory
35185 units @var{length} (@pxref{addressable memory unit});
35186 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35196 @item z @var{type},@var{addr},@var{kind}
35197 @itemx Z @var{type},@var{addr},@var{kind}
35198 @anchor{insert breakpoint or watchpoint packet}
35199 @cindex @samp{z} packet
35200 @cindex @samp{Z} packets
35201 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35202 watchpoint starting at address @var{address} of kind @var{kind}.
35204 Each breakpoint and watchpoint packet @var{type} is documented
35207 @emph{Implementation notes: A remote target shall return an empty string
35208 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35209 remote target shall support either both or neither of a given
35210 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35211 avoid potential problems with duplicate packets, the operations should
35212 be implemented in an idempotent way.}
35214 @item z0,@var{addr},@var{kind}
35215 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35216 @cindex @samp{z0} packet
35217 @cindex @samp{Z0} packet
35218 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35219 @var{addr} of type @var{kind}.
35221 A memory breakpoint is implemented by replacing the instruction at
35222 @var{addr} with a software breakpoint or trap instruction. The
35223 @var{kind} is target-specific and typically indicates the size of
35224 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35225 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35226 architectures have additional meanings for @var{kind};
35227 @var{cond_list} is an optional list of conditional expressions in bytecode
35228 form that should be evaluated on the target's side. These are the
35229 conditions that should be taken into consideration when deciding if
35230 the breakpoint trigger should be reported back to @var{GDBN}.
35232 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35233 for how to best report a memory breakpoint event to @value{GDBN}.
35235 The @var{cond_list} parameter is comprised of a series of expressions,
35236 concatenated without separators. Each expression has the following form:
35240 @item X @var{len},@var{expr}
35241 @var{len} is the length of the bytecode expression and @var{expr} is the
35242 actual conditional expression in bytecode form.
35246 The optional @var{cmd_list} parameter introduces commands that may be
35247 run on the target, rather than being reported back to @value{GDBN}.
35248 The parameter starts with a numeric flag @var{persist}; if the flag is
35249 nonzero, then the breakpoint may remain active and the commands
35250 continue to be run even when @value{GDBN} disconnects from the target.
35251 Following this flag is a series of expressions concatenated with no
35252 separators. Each expression has the following form:
35256 @item X @var{len},@var{expr}
35257 @var{len} is the length of the bytecode expression and @var{expr} is the
35258 actual conditional expression in bytecode form.
35262 see @ref{Architecture-Specific Protocol Details}.
35264 @emph{Implementation note: It is possible for a target to copy or move
35265 code that contains memory breakpoints (e.g., when implementing
35266 overlays). The behavior of this packet, in the presence of such a
35267 target, is not defined.}
35279 @item z1,@var{addr},@var{kind}
35280 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35281 @cindex @samp{z1} packet
35282 @cindex @samp{Z1} packet
35283 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35284 address @var{addr}.
35286 A hardware breakpoint is implemented using a mechanism that is not
35287 dependant on being able to modify the target's memory. The @var{kind}
35288 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35290 @emph{Implementation note: A hardware breakpoint is not affected by code
35303 @item z2,@var{addr},@var{kind}
35304 @itemx Z2,@var{addr},@var{kind}
35305 @cindex @samp{z2} packet
35306 @cindex @samp{Z2} packet
35307 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35308 The number of bytes to watch is specified by @var{kind}.
35320 @item z3,@var{addr},@var{kind}
35321 @itemx Z3,@var{addr},@var{kind}
35322 @cindex @samp{z3} packet
35323 @cindex @samp{Z3} packet
35324 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35325 The number of bytes to watch is specified by @var{kind}.
35337 @item z4,@var{addr},@var{kind}
35338 @itemx Z4,@var{addr},@var{kind}
35339 @cindex @samp{z4} packet
35340 @cindex @samp{Z4} packet
35341 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35342 The number of bytes to watch is specified by @var{kind}.
35356 @node Stop Reply Packets
35357 @section Stop Reply Packets
35358 @cindex stop reply packets
35360 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35361 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35362 receive any of the below as a reply. Except for @samp{?}
35363 and @samp{vStopped}, that reply is only returned
35364 when the target halts. In the below the exact meaning of @dfn{signal
35365 number} is defined by the header @file{include/gdb/signals.h} in the
35366 @value{GDBN} source code.
35368 As in the description of request packets, we include spaces in the
35369 reply templates for clarity; these are not part of the reply packet's
35370 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35376 The program received signal number @var{AA} (a two-digit hexadecimal
35377 number). This is equivalent to a @samp{T} response with no
35378 @var{n}:@var{r} pairs.
35380 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35381 @cindex @samp{T} packet reply
35382 The program received signal number @var{AA} (a two-digit hexadecimal
35383 number). This is equivalent to an @samp{S} response, except that the
35384 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35385 and other information directly in the stop reply packet, reducing
35386 round-trip latency. Single-step and breakpoint traps are reported
35387 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35391 If @var{n} is a hexadecimal number, it is a register number, and the
35392 corresponding @var{r} gives that register's value. The data @var{r} is a
35393 series of bytes in target byte order, with each byte given by a
35394 two-digit hex number.
35397 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35398 the stopped thread, as specified in @ref{thread-id syntax}.
35401 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35402 the core on which the stop event was detected.
35405 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35406 specific event that stopped the target. The currently defined stop
35407 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35408 signal. At most one stop reason should be present.
35411 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35412 and go on to the next; this allows us to extend the protocol in the
35416 The currently defined stop reasons are:
35422 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35425 @cindex shared library events, remote reply
35427 The packet indicates that the loaded libraries have changed.
35428 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35429 list of loaded libraries. The @var{r} part is ignored.
35431 @cindex replay log events, remote reply
35433 The packet indicates that the target cannot continue replaying
35434 logged execution events, because it has reached the end (or the
35435 beginning when executing backward) of the log. The value of @var{r}
35436 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35437 for more information.
35440 @anchor{swbreak stop reason}
35441 The packet indicates a memory breakpoint instruction was executed,
35442 irrespective of whether it was @value{GDBN} that planted the
35443 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35444 part must be left empty.
35446 On some architectures, such as x86, at the architecture level, when a
35447 breakpoint instruction executes the program counter points at the
35448 breakpoint address plus an offset. On such targets, the stub is
35449 responsible for adjusting the PC to point back at the breakpoint
35452 This packet should not be sent by default; older @value{GDBN} versions
35453 did not support it. @value{GDBN} requests it, by supplying an
35454 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35455 remote stub must also supply the appropriate @samp{qSupported} feature
35456 indicating support.
35458 This packet is required for correct non-stop mode operation.
35461 The packet indicates the target stopped for a hardware breakpoint.
35462 The @var{r} part must be left empty.
35464 The same remarks about @samp{qSupported} and non-stop mode above
35467 @cindex fork events, remote reply
35469 The packet indicates that @code{fork} was called, and @var{r}
35470 is the thread ID of the new child process. Refer to
35471 @ref{thread-id syntax} for the format of the @var{thread-id}
35472 field. This packet is only applicable to targets that support
35475 This packet should not be sent by default; older @value{GDBN} versions
35476 did not support it. @value{GDBN} requests it, by supplying an
35477 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35478 remote stub must also supply the appropriate @samp{qSupported} feature
35479 indicating support.
35481 @cindex vfork events, remote reply
35483 The packet indicates that @code{vfork} was called, and @var{r}
35484 is the thread ID of the new child process. Refer to
35485 @ref{thread-id syntax} for the format of the @var{thread-id}
35486 field. This packet is only applicable to targets that support
35489 This packet should not be sent by default; older @value{GDBN} versions
35490 did not support it. @value{GDBN} requests it, by supplying an
35491 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35492 remote stub must also supply the appropriate @samp{qSupported} feature
35493 indicating support.
35495 @cindex vforkdone events, remote reply
35497 The packet indicates that a child process created by a vfork
35498 has either called @code{exec} or terminated, so that the
35499 address spaces of the parent and child process are no longer
35500 shared. The @var{r} part is ignored. This packet is only
35501 applicable to targets that support vforkdone events.
35503 This packet should not be sent by default; older @value{GDBN} versions
35504 did not support it. @value{GDBN} requests it, by supplying an
35505 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35506 remote stub must also supply the appropriate @samp{qSupported} feature
35507 indicating support.
35512 @itemx W @var{AA} ; process:@var{pid}
35513 The process exited, and @var{AA} is the exit status. This is only
35514 applicable to certain targets.
35516 The second form of the response, including the process ID of the exited
35517 process, can be used only when @value{GDBN} has reported support for
35518 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35519 The @var{pid} is formatted as a big-endian hex string.
35522 @itemx X @var{AA} ; process:@var{pid}
35523 The process terminated with signal @var{AA}.
35525 The second form of the response, including the process ID of the
35526 terminated process, can be used only when @value{GDBN} has reported
35527 support for multiprocess protocol extensions; see @ref{multiprocess
35528 extensions}. The @var{pid} is formatted as a big-endian hex string.
35530 @item O @var{XX}@dots{}
35531 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35532 written as the program's console output. This can happen at any time
35533 while the program is running and the debugger should continue to wait
35534 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35536 @item F @var{call-id},@var{parameter}@dots{}
35537 @var{call-id} is the identifier which says which host system call should
35538 be called. This is just the name of the function. Translation into the
35539 correct system call is only applicable as it's defined in @value{GDBN}.
35540 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35543 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35544 this very system call.
35546 The target replies with this packet when it expects @value{GDBN} to
35547 call a host system call on behalf of the target. @value{GDBN} replies
35548 with an appropriate @samp{F} packet and keeps up waiting for the next
35549 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35550 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35551 Protocol Extension}, for more details.
35555 @node General Query Packets
35556 @section General Query Packets
35557 @cindex remote query requests
35559 Packets starting with @samp{q} are @dfn{general query packets};
35560 packets starting with @samp{Q} are @dfn{general set packets}. General
35561 query and set packets are a semi-unified form for retrieving and
35562 sending information to and from the stub.
35564 The initial letter of a query or set packet is followed by a name
35565 indicating what sort of thing the packet applies to. For example,
35566 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35567 definitions with the stub. These packet names follow some
35572 The name must not contain commas, colons or semicolons.
35574 Most @value{GDBN} query and set packets have a leading upper case
35577 The names of custom vendor packets should use a company prefix, in
35578 lower case, followed by a period. For example, packets designed at
35579 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35580 foos) or @samp{Qacme.bar} (for setting bars).
35583 The name of a query or set packet should be separated from any
35584 parameters by a @samp{:}; the parameters themselves should be
35585 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35586 full packet name, and check for a separator or the end of the packet,
35587 in case two packet names share a common prefix. New packets should not begin
35588 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35589 packets predate these conventions, and have arguments without any terminator
35590 for the packet name; we suspect they are in widespread use in places that
35591 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35592 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35595 Like the descriptions of the other packets, each description here
35596 has a template showing the packet's overall syntax, followed by an
35597 explanation of the packet's meaning. We include spaces in some of the
35598 templates for clarity; these are not part of the packet's syntax. No
35599 @value{GDBN} packet uses spaces to separate its components.
35601 Here are the currently defined query and set packets:
35607 Turn on or off the agent as a helper to perform some debugging operations
35608 delegated from @value{GDBN} (@pxref{Control Agent}).
35610 @item QAllow:@var{op}:@var{val}@dots{}
35611 @cindex @samp{QAllow} packet
35612 Specify which operations @value{GDBN} expects to request of the
35613 target, as a semicolon-separated list of operation name and value
35614 pairs. Possible values for @var{op} include @samp{WriteReg},
35615 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35616 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35617 indicating that @value{GDBN} will not request the operation, or 1,
35618 indicating that it may. (The target can then use this to set up its
35619 own internals optimally, for instance if the debugger never expects to
35620 insert breakpoints, it may not need to install its own trap handler.)
35623 @cindex current thread, remote request
35624 @cindex @samp{qC} packet
35625 Return the current thread ID.
35629 @item QC @var{thread-id}
35630 Where @var{thread-id} is a thread ID as documented in
35631 @ref{thread-id syntax}.
35632 @item @r{(anything else)}
35633 Any other reply implies the old thread ID.
35636 @item qCRC:@var{addr},@var{length}
35637 @cindex CRC of memory block, remote request
35638 @cindex @samp{qCRC} packet
35639 @anchor{qCRC packet}
35640 Compute the CRC checksum of a block of memory using CRC-32 defined in
35641 IEEE 802.3. The CRC is computed byte at a time, taking the most
35642 significant bit of each byte first. The initial pattern code
35643 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35645 @emph{Note:} This is the same CRC used in validating separate debug
35646 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35647 Files}). However the algorithm is slightly different. When validating
35648 separate debug files, the CRC is computed taking the @emph{least}
35649 significant bit of each byte first, and the final result is inverted to
35650 detect trailing zeros.
35655 An error (such as memory fault)
35656 @item C @var{crc32}
35657 The specified memory region's checksum is @var{crc32}.
35660 @item QDisableRandomization:@var{value}
35661 @cindex disable address space randomization, remote request
35662 @cindex @samp{QDisableRandomization} packet
35663 Some target operating systems will randomize the virtual address space
35664 of the inferior process as a security feature, but provide a feature
35665 to disable such randomization, e.g.@: to allow for a more deterministic
35666 debugging experience. On such systems, this packet with a @var{value}
35667 of 1 directs the target to disable address space randomization for
35668 processes subsequently started via @samp{vRun} packets, while a packet
35669 with a @var{value} of 0 tells the target to enable address space
35672 This packet is only available in extended mode (@pxref{extended mode}).
35677 The request succeeded.
35680 An error occurred. The error number @var{nn} is given as hex digits.
35683 An empty reply indicates that @samp{QDisableRandomization} is not supported
35687 This packet is not probed by default; the remote stub must request it,
35688 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35689 This should only be done on targets that actually support disabling
35690 address space randomization.
35693 @itemx qsThreadInfo
35694 @cindex list active threads, remote request
35695 @cindex @samp{qfThreadInfo} packet
35696 @cindex @samp{qsThreadInfo} packet
35697 Obtain a list of all active thread IDs from the target (OS). Since there
35698 may be too many active threads to fit into one reply packet, this query
35699 works iteratively: it may require more than one query/reply sequence to
35700 obtain the entire list of threads. The first query of the sequence will
35701 be the @samp{qfThreadInfo} query; subsequent queries in the
35702 sequence will be the @samp{qsThreadInfo} query.
35704 NOTE: This packet replaces the @samp{qL} query (see below).
35708 @item m @var{thread-id}
35710 @item m @var{thread-id},@var{thread-id}@dots{}
35711 a comma-separated list of thread IDs
35713 (lower case letter @samp{L}) denotes end of list.
35716 In response to each query, the target will reply with a list of one or
35717 more thread IDs, separated by commas.
35718 @value{GDBN} will respond to each reply with a request for more thread
35719 ids (using the @samp{qs} form of the query), until the target responds
35720 with @samp{l} (lower-case ell, for @dfn{last}).
35721 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35724 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
35725 initial connection with the remote target, and the very first thread ID
35726 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
35727 message. Therefore, the stub should ensure that the first thread ID in
35728 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
35730 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35731 @cindex get thread-local storage address, remote request
35732 @cindex @samp{qGetTLSAddr} packet
35733 Fetch the address associated with thread local storage specified
35734 by @var{thread-id}, @var{offset}, and @var{lm}.
35736 @var{thread-id} is the thread ID associated with the
35737 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35739 @var{offset} is the (big endian, hex encoded) offset associated with the
35740 thread local variable. (This offset is obtained from the debug
35741 information associated with the variable.)
35743 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35744 load module associated with the thread local storage. For example,
35745 a @sc{gnu}/Linux system will pass the link map address of the shared
35746 object associated with the thread local storage under consideration.
35747 Other operating environments may choose to represent the load module
35748 differently, so the precise meaning of this parameter will vary.
35752 @item @var{XX}@dots{}
35753 Hex encoded (big endian) bytes representing the address of the thread
35754 local storage requested.
35757 An error occurred. The error number @var{nn} is given as hex digits.
35760 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35763 @item qGetTIBAddr:@var{thread-id}
35764 @cindex get thread information block address
35765 @cindex @samp{qGetTIBAddr} packet
35766 Fetch address of the Windows OS specific Thread Information Block.
35768 @var{thread-id} is the thread ID associated with the thread.
35772 @item @var{XX}@dots{}
35773 Hex encoded (big endian) bytes representing the linear address of the
35774 thread information block.
35777 An error occured. This means that either the thread was not found, or the
35778 address could not be retrieved.
35781 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35784 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35785 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35786 digit) is one to indicate the first query and zero to indicate a
35787 subsequent query; @var{threadcount} (two hex digits) is the maximum
35788 number of threads the response packet can contain; and @var{nextthread}
35789 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35790 returned in the response as @var{argthread}.
35792 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35796 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35797 Where: @var{count} (two hex digits) is the number of threads being
35798 returned; @var{done} (one hex digit) is zero to indicate more threads
35799 and one indicates no further threads; @var{argthreadid} (eight hex
35800 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35801 is a sequence of thread IDs, @var{threadid} (eight hex
35802 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
35806 @cindex section offsets, remote request
35807 @cindex @samp{qOffsets} packet
35808 Get section offsets that the target used when relocating the downloaded
35813 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35814 Relocate the @code{Text} section by @var{xxx} from its original address.
35815 Relocate the @code{Data} section by @var{yyy} from its original address.
35816 If the object file format provides segment information (e.g.@: @sc{elf}
35817 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35818 segments by the supplied offsets.
35820 @emph{Note: while a @code{Bss} offset may be included in the response,
35821 @value{GDBN} ignores this and instead applies the @code{Data} offset
35822 to the @code{Bss} section.}
35824 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35825 Relocate the first segment of the object file, which conventionally
35826 contains program code, to a starting address of @var{xxx}. If
35827 @samp{DataSeg} is specified, relocate the second segment, which
35828 conventionally contains modifiable data, to a starting address of
35829 @var{yyy}. @value{GDBN} will report an error if the object file
35830 does not contain segment information, or does not contain at least
35831 as many segments as mentioned in the reply. Extra segments are
35832 kept at fixed offsets relative to the last relocated segment.
35835 @item qP @var{mode} @var{thread-id}
35836 @cindex thread information, remote request
35837 @cindex @samp{qP} packet
35838 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35839 encoded 32 bit mode; @var{thread-id} is a thread ID
35840 (@pxref{thread-id syntax}).
35842 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35845 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35849 @cindex non-stop mode, remote request
35850 @cindex @samp{QNonStop} packet
35852 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35853 @xref{Remote Non-Stop}, for more information.
35858 The request succeeded.
35861 An error occurred. The error number @var{nn} is given as hex digits.
35864 An empty reply indicates that @samp{QNonStop} is not supported by
35868 This packet is not probed by default; the remote stub must request it,
35869 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35870 Use of this packet is controlled by the @code{set non-stop} command;
35871 @pxref{Non-Stop Mode}.
35873 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35874 @cindex pass signals to inferior, remote request
35875 @cindex @samp{QPassSignals} packet
35876 @anchor{QPassSignals}
35877 Each listed @var{signal} should be passed directly to the inferior process.
35878 Signals are numbered identically to continue packets and stop replies
35879 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35880 strictly greater than the previous item. These signals do not need to stop
35881 the inferior, or be reported to @value{GDBN}. All other signals should be
35882 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35883 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35884 new list. This packet improves performance when using @samp{handle
35885 @var{signal} nostop noprint pass}.
35890 The request succeeded.
35893 An error occurred. The error number @var{nn} is given as hex digits.
35896 An empty reply indicates that @samp{QPassSignals} is not supported by
35900 Use of this packet is controlled by the @code{set remote pass-signals}
35901 command (@pxref{Remote Configuration, set remote pass-signals}).
35902 This packet is not probed by default; the remote stub must request it,
35903 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35905 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35906 @cindex signals the inferior may see, remote request
35907 @cindex @samp{QProgramSignals} packet
35908 @anchor{QProgramSignals}
35909 Each listed @var{signal} may be delivered to the inferior process.
35910 Others should be silently discarded.
35912 In some cases, the remote stub may need to decide whether to deliver a
35913 signal to the program or not without @value{GDBN} involvement. One
35914 example of that is while detaching --- the program's threads may have
35915 stopped for signals that haven't yet had a chance of being reported to
35916 @value{GDBN}, and so the remote stub can use the signal list specified
35917 by this packet to know whether to deliver or ignore those pending
35920 This does not influence whether to deliver a signal as requested by a
35921 resumption packet (@pxref{vCont packet}).
35923 Signals are numbered identically to continue packets and stop replies
35924 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35925 strictly greater than the previous item. Multiple
35926 @samp{QProgramSignals} packets do not combine; any earlier
35927 @samp{QProgramSignals} list is completely replaced by the new list.
35932 The request succeeded.
35935 An error occurred. The error number @var{nn} is given as hex digits.
35938 An empty reply indicates that @samp{QProgramSignals} is not supported
35942 Use of this packet is controlled by the @code{set remote program-signals}
35943 command (@pxref{Remote Configuration, set remote program-signals}).
35944 This packet is not probed by default; the remote stub must request it,
35945 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35947 @item qRcmd,@var{command}
35948 @cindex execute remote command, remote request
35949 @cindex @samp{qRcmd} packet
35950 @var{command} (hex encoded) is passed to the local interpreter for
35951 execution. Invalid commands should be reported using the output
35952 string. Before the final result packet, the target may also respond
35953 with a number of intermediate @samp{O@var{output}} console output
35954 packets. @emph{Implementors should note that providing access to a
35955 stubs's interpreter may have security implications}.
35960 A command response with no output.
35962 A command response with the hex encoded output string @var{OUTPUT}.
35964 Indicate a badly formed request.
35966 An empty reply indicates that @samp{qRcmd} is not recognized.
35969 (Note that the @code{qRcmd} packet's name is separated from the
35970 command by a @samp{,}, not a @samp{:}, contrary to the naming
35971 conventions above. Please don't use this packet as a model for new
35974 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35975 @cindex searching memory, in remote debugging
35977 @cindex @samp{qSearch:memory} packet
35979 @cindex @samp{qSearch memory} packet
35980 @anchor{qSearch memory}
35981 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35982 Both @var{address} and @var{length} are encoded in hex;
35983 @var{search-pattern} is a sequence of bytes, also hex encoded.
35988 The pattern was not found.
35990 The pattern was found at @var{address}.
35992 A badly formed request or an error was encountered while searching memory.
35994 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35997 @item QStartNoAckMode
35998 @cindex @samp{QStartNoAckMode} packet
35999 @anchor{QStartNoAckMode}
36000 Request that the remote stub disable the normal @samp{+}/@samp{-}
36001 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36006 The stub has switched to no-acknowledgment mode.
36007 @value{GDBN} acknowledges this reponse,
36008 but neither the stub nor @value{GDBN} shall send or expect further
36009 @samp{+}/@samp{-} acknowledgments in the current connection.
36011 An empty reply indicates that the stub does not support no-acknowledgment mode.
36014 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36015 @cindex supported packets, remote query
36016 @cindex features of the remote protocol
36017 @cindex @samp{qSupported} packet
36018 @anchor{qSupported}
36019 Tell the remote stub about features supported by @value{GDBN}, and
36020 query the stub for features it supports. This packet allows
36021 @value{GDBN} and the remote stub to take advantage of each others'
36022 features. @samp{qSupported} also consolidates multiple feature probes
36023 at startup, to improve @value{GDBN} performance---a single larger
36024 packet performs better than multiple smaller probe packets on
36025 high-latency links. Some features may enable behavior which must not
36026 be on by default, e.g.@: because it would confuse older clients or
36027 stubs. Other features may describe packets which could be
36028 automatically probed for, but are not. These features must be
36029 reported before @value{GDBN} will use them. This ``default
36030 unsupported'' behavior is not appropriate for all packets, but it
36031 helps to keep the initial connection time under control with new
36032 versions of @value{GDBN} which support increasing numbers of packets.
36036 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36037 The stub supports or does not support each returned @var{stubfeature},
36038 depending on the form of each @var{stubfeature} (see below for the
36041 An empty reply indicates that @samp{qSupported} is not recognized,
36042 or that no features needed to be reported to @value{GDBN}.
36045 The allowed forms for each feature (either a @var{gdbfeature} in the
36046 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36050 @item @var{name}=@var{value}
36051 The remote protocol feature @var{name} is supported, and associated
36052 with the specified @var{value}. The format of @var{value} depends
36053 on the feature, but it must not include a semicolon.
36055 The remote protocol feature @var{name} is supported, and does not
36056 need an associated value.
36058 The remote protocol feature @var{name} is not supported.
36060 The remote protocol feature @var{name} may be supported, and
36061 @value{GDBN} should auto-detect support in some other way when it is
36062 needed. This form will not be used for @var{gdbfeature} notifications,
36063 but may be used for @var{stubfeature} responses.
36066 Whenever the stub receives a @samp{qSupported} request, the
36067 supplied set of @value{GDBN} features should override any previous
36068 request. This allows @value{GDBN} to put the stub in a known
36069 state, even if the stub had previously been communicating with
36070 a different version of @value{GDBN}.
36072 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36077 This feature indicates whether @value{GDBN} supports multiprocess
36078 extensions to the remote protocol. @value{GDBN} does not use such
36079 extensions unless the stub also reports that it supports them by
36080 including @samp{multiprocess+} in its @samp{qSupported} reply.
36081 @xref{multiprocess extensions}, for details.
36084 This feature indicates that @value{GDBN} supports the XML target
36085 description. If the stub sees @samp{xmlRegisters=} with target
36086 specific strings separated by a comma, it will report register
36090 This feature indicates whether @value{GDBN} supports the
36091 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36092 instruction reply packet}).
36095 This feature indicates whether @value{GDBN} supports the swbreak stop
36096 reason in stop replies. @xref{swbreak stop reason}, for details.
36099 This feature indicates whether @value{GDBN} supports the hwbreak stop
36100 reason in stop replies. @xref{swbreak stop reason}, for details.
36103 This feature indicates whether @value{GDBN} supports fork event
36104 extensions to the remote protocol. @value{GDBN} does not use such
36105 extensions unless the stub also reports that it supports them by
36106 including @samp{fork-events+} in its @samp{qSupported} reply.
36109 This feature indicates whether @value{GDBN} supports vfork event
36110 extensions to the remote protocol. @value{GDBN} does not use such
36111 extensions unless the stub also reports that it supports them by
36112 including @samp{vfork-events+} in its @samp{qSupported} reply.
36115 Stubs should ignore any unknown values for
36116 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36117 packet supports receiving packets of unlimited length (earlier
36118 versions of @value{GDBN} may reject overly long responses). Additional values
36119 for @var{gdbfeature} may be defined in the future to let the stub take
36120 advantage of new features in @value{GDBN}, e.g.@: incompatible
36121 improvements in the remote protocol---the @samp{multiprocess} feature is
36122 an example of such a feature. The stub's reply should be independent
36123 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36124 describes all the features it supports, and then the stub replies with
36125 all the features it supports.
36127 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36128 responses, as long as each response uses one of the standard forms.
36130 Some features are flags. A stub which supports a flag feature
36131 should respond with a @samp{+} form response. Other features
36132 require values, and the stub should respond with an @samp{=}
36135 Each feature has a default value, which @value{GDBN} will use if
36136 @samp{qSupported} is not available or if the feature is not mentioned
36137 in the @samp{qSupported} response. The default values are fixed; a
36138 stub is free to omit any feature responses that match the defaults.
36140 Not all features can be probed, but for those which can, the probing
36141 mechanism is useful: in some cases, a stub's internal
36142 architecture may not allow the protocol layer to know some information
36143 about the underlying target in advance. This is especially common in
36144 stubs which may be configured for multiple targets.
36146 These are the currently defined stub features and their properties:
36148 @multitable @columnfractions 0.35 0.2 0.12 0.2
36149 @c NOTE: The first row should be @headitem, but we do not yet require
36150 @c a new enough version of Texinfo (4.7) to use @headitem.
36152 @tab Value Required
36156 @item @samp{PacketSize}
36161 @item @samp{qXfer:auxv:read}
36166 @item @samp{qXfer:btrace:read}
36171 @item @samp{qXfer:btrace-conf:read}
36176 @item @samp{qXfer:exec-file:read}
36181 @item @samp{qXfer:features:read}
36186 @item @samp{qXfer:libraries:read}
36191 @item @samp{qXfer:libraries-svr4:read}
36196 @item @samp{augmented-libraries-svr4-read}
36201 @item @samp{qXfer:memory-map:read}
36206 @item @samp{qXfer:sdata:read}
36211 @item @samp{qXfer:spu:read}
36216 @item @samp{qXfer:spu:write}
36221 @item @samp{qXfer:siginfo:read}
36226 @item @samp{qXfer:siginfo:write}
36231 @item @samp{qXfer:threads:read}
36236 @item @samp{qXfer:traceframe-info:read}
36241 @item @samp{qXfer:uib:read}
36246 @item @samp{qXfer:fdpic:read}
36251 @item @samp{Qbtrace:off}
36256 @item @samp{Qbtrace:bts}
36261 @item @samp{Qbtrace:pt}
36266 @item @samp{Qbtrace-conf:bts:size}
36271 @item @samp{Qbtrace-conf:pt:size}
36276 @item @samp{QNonStop}
36281 @item @samp{QPassSignals}
36286 @item @samp{QStartNoAckMode}
36291 @item @samp{multiprocess}
36296 @item @samp{ConditionalBreakpoints}
36301 @item @samp{ConditionalTracepoints}
36306 @item @samp{ReverseContinue}
36311 @item @samp{ReverseStep}
36316 @item @samp{TracepointSource}
36321 @item @samp{QAgent}
36326 @item @samp{QAllow}
36331 @item @samp{QDisableRandomization}
36336 @item @samp{EnableDisableTracepoints}
36341 @item @samp{QTBuffer:size}
36346 @item @samp{tracenz}
36351 @item @samp{BreakpointCommands}
36356 @item @samp{swbreak}
36361 @item @samp{hwbreak}
36366 @item @samp{fork-events}
36371 @item @samp{vfork-events}
36378 These are the currently defined stub features, in more detail:
36381 @cindex packet size, remote protocol
36382 @item PacketSize=@var{bytes}
36383 The remote stub can accept packets up to at least @var{bytes} in
36384 length. @value{GDBN} will send packets up to this size for bulk
36385 transfers, and will never send larger packets. This is a limit on the
36386 data characters in the packet, including the frame and checksum.
36387 There is no trailing NUL byte in a remote protocol packet; if the stub
36388 stores packets in a NUL-terminated format, it should allow an extra
36389 byte in its buffer for the NUL. If this stub feature is not supported,
36390 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36392 @item qXfer:auxv:read
36393 The remote stub understands the @samp{qXfer:auxv:read} packet
36394 (@pxref{qXfer auxiliary vector read}).
36396 @item qXfer:btrace:read
36397 The remote stub understands the @samp{qXfer:btrace:read}
36398 packet (@pxref{qXfer btrace read}).
36400 @item qXfer:btrace-conf:read
36401 The remote stub understands the @samp{qXfer:btrace-conf:read}
36402 packet (@pxref{qXfer btrace-conf read}).
36404 @item qXfer:exec-file:read
36405 The remote stub understands the @samp{qXfer:exec-file:read} packet
36406 (@pxref{qXfer executable filename read}).
36408 @item qXfer:features:read
36409 The remote stub understands the @samp{qXfer:features:read} packet
36410 (@pxref{qXfer target description read}).
36412 @item qXfer:libraries:read
36413 The remote stub understands the @samp{qXfer:libraries:read} packet
36414 (@pxref{qXfer library list read}).
36416 @item qXfer:libraries-svr4:read
36417 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36418 (@pxref{qXfer svr4 library list read}).
36420 @item augmented-libraries-svr4-read
36421 The remote stub understands the augmented form of the
36422 @samp{qXfer:libraries-svr4:read} packet
36423 (@pxref{qXfer svr4 library list read}).
36425 @item qXfer:memory-map:read
36426 The remote stub understands the @samp{qXfer:memory-map:read} packet
36427 (@pxref{qXfer memory map read}).
36429 @item qXfer:sdata:read
36430 The remote stub understands the @samp{qXfer:sdata:read} packet
36431 (@pxref{qXfer sdata read}).
36433 @item qXfer:spu:read
36434 The remote stub understands the @samp{qXfer:spu:read} packet
36435 (@pxref{qXfer spu read}).
36437 @item qXfer:spu:write
36438 The remote stub understands the @samp{qXfer:spu:write} packet
36439 (@pxref{qXfer spu write}).
36441 @item qXfer:siginfo:read
36442 The remote stub understands the @samp{qXfer:siginfo:read} packet
36443 (@pxref{qXfer siginfo read}).
36445 @item qXfer:siginfo:write
36446 The remote stub understands the @samp{qXfer:siginfo:write} packet
36447 (@pxref{qXfer siginfo write}).
36449 @item qXfer:threads:read
36450 The remote stub understands the @samp{qXfer:threads:read} packet
36451 (@pxref{qXfer threads read}).
36453 @item qXfer:traceframe-info:read
36454 The remote stub understands the @samp{qXfer:traceframe-info:read}
36455 packet (@pxref{qXfer traceframe info read}).
36457 @item qXfer:uib:read
36458 The remote stub understands the @samp{qXfer:uib:read}
36459 packet (@pxref{qXfer unwind info block}).
36461 @item qXfer:fdpic:read
36462 The remote stub understands the @samp{qXfer:fdpic:read}
36463 packet (@pxref{qXfer fdpic loadmap read}).
36466 The remote stub understands the @samp{QNonStop} packet
36467 (@pxref{QNonStop}).
36470 The remote stub understands the @samp{QPassSignals} packet
36471 (@pxref{QPassSignals}).
36473 @item QStartNoAckMode
36474 The remote stub understands the @samp{QStartNoAckMode} packet and
36475 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36478 @anchor{multiprocess extensions}
36479 @cindex multiprocess extensions, in remote protocol
36480 The remote stub understands the multiprocess extensions to the remote
36481 protocol syntax. The multiprocess extensions affect the syntax of
36482 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36483 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36484 replies. Note that reporting this feature indicates support for the
36485 syntactic extensions only, not that the stub necessarily supports
36486 debugging of more than one process at a time. The stub must not use
36487 multiprocess extensions in packet replies unless @value{GDBN} has also
36488 indicated it supports them in its @samp{qSupported} request.
36490 @item qXfer:osdata:read
36491 The remote stub understands the @samp{qXfer:osdata:read} packet
36492 ((@pxref{qXfer osdata read}).
36494 @item ConditionalBreakpoints
36495 The target accepts and implements evaluation of conditional expressions
36496 defined for breakpoints. The target will only report breakpoint triggers
36497 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36499 @item ConditionalTracepoints
36500 The remote stub accepts and implements conditional expressions defined
36501 for tracepoints (@pxref{Tracepoint Conditions}).
36503 @item ReverseContinue
36504 The remote stub accepts and implements the reverse continue packet
36508 The remote stub accepts and implements the reverse step packet
36511 @item TracepointSource
36512 The remote stub understands the @samp{QTDPsrc} packet that supplies
36513 the source form of tracepoint definitions.
36516 The remote stub understands the @samp{QAgent} packet.
36519 The remote stub understands the @samp{QAllow} packet.
36521 @item QDisableRandomization
36522 The remote stub understands the @samp{QDisableRandomization} packet.
36524 @item StaticTracepoint
36525 @cindex static tracepoints, in remote protocol
36526 The remote stub supports static tracepoints.
36528 @item InstallInTrace
36529 @anchor{install tracepoint in tracing}
36530 The remote stub supports installing tracepoint in tracing.
36532 @item EnableDisableTracepoints
36533 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36534 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36535 to be enabled and disabled while a trace experiment is running.
36537 @item QTBuffer:size
36538 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
36539 packet that allows to change the size of the trace buffer.
36542 @cindex string tracing, in remote protocol
36543 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36544 See @ref{Bytecode Descriptions} for details about the bytecode.
36546 @item BreakpointCommands
36547 @cindex breakpoint commands, in remote protocol
36548 The remote stub supports running a breakpoint's command list itself,
36549 rather than reporting the hit to @value{GDBN}.
36552 The remote stub understands the @samp{Qbtrace:off} packet.
36555 The remote stub understands the @samp{Qbtrace:bts} packet.
36558 The remote stub understands the @samp{Qbtrace:pt} packet.
36560 @item Qbtrace-conf:bts:size
36561 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
36563 @item Qbtrace-conf:pt:size
36564 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
36567 The remote stub reports the @samp{swbreak} stop reason for memory
36571 The remote stub reports the @samp{hwbreak} stop reason for hardware
36575 The remote stub reports the @samp{fork} stop reason for fork events.
36578 The remote stub reports the @samp{vfork} stop reason for vfork events
36579 and vforkdone events.
36584 @cindex symbol lookup, remote request
36585 @cindex @samp{qSymbol} packet
36586 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36587 requests. Accept requests from the target for the values of symbols.
36592 The target does not need to look up any (more) symbols.
36593 @item qSymbol:@var{sym_name}
36594 The target requests the value of symbol @var{sym_name} (hex encoded).
36595 @value{GDBN} may provide the value by using the
36596 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36600 @item qSymbol:@var{sym_value}:@var{sym_name}
36601 Set the value of @var{sym_name} to @var{sym_value}.
36603 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36604 target has previously requested.
36606 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36607 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36613 The target does not need to look up any (more) symbols.
36614 @item qSymbol:@var{sym_name}
36615 The target requests the value of a new symbol @var{sym_name} (hex
36616 encoded). @value{GDBN} will continue to supply the values of symbols
36617 (if available), until the target ceases to request them.
36622 @itemx QTDisconnected
36629 @itemx qTMinFTPILen
36631 @xref{Tracepoint Packets}.
36633 @item qThreadExtraInfo,@var{thread-id}
36634 @cindex thread attributes info, remote request
36635 @cindex @samp{qThreadExtraInfo} packet
36636 Obtain from the target OS a printable string description of thread
36637 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
36638 for the forms of @var{thread-id}. This
36639 string may contain anything that the target OS thinks is interesting
36640 for @value{GDBN} to tell the user about the thread. The string is
36641 displayed in @value{GDBN}'s @code{info threads} display. Some
36642 examples of possible thread extra info strings are @samp{Runnable}, or
36643 @samp{Blocked on Mutex}.
36647 @item @var{XX}@dots{}
36648 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36649 comprising the printable string containing the extra information about
36650 the thread's attributes.
36653 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36654 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36655 conventions above. Please don't use this packet as a model for new
36674 @xref{Tracepoint Packets}.
36676 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36677 @cindex read special object, remote request
36678 @cindex @samp{qXfer} packet
36679 @anchor{qXfer read}
36680 Read uninterpreted bytes from the target's special data area
36681 identified by the keyword @var{object}. Request @var{length} bytes
36682 starting at @var{offset} bytes into the data. The content and
36683 encoding of @var{annex} is specific to @var{object}; it can supply
36684 additional details about what data to access.
36686 Here are the specific requests of this form defined so far. All
36687 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36688 formats, listed below.
36691 @item qXfer:auxv:read::@var{offset},@var{length}
36692 @anchor{qXfer auxiliary vector read}
36693 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36694 auxiliary vector}. Note @var{annex} must be empty.
36696 This packet is not probed by default; the remote stub must request it,
36697 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36699 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
36700 @anchor{qXfer btrace read}
36702 Return a description of the current branch trace.
36703 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
36704 packet may have one of the following values:
36708 Returns all available branch trace.
36711 Returns all available branch trace if the branch trace changed since
36712 the last read request.
36715 Returns the new branch trace since the last read request. Adds a new
36716 block to the end of the trace that begins at zero and ends at the source
36717 location of the first branch in the trace buffer. This extra block is
36718 used to stitch traces together.
36720 If the trace buffer overflowed, returns an error indicating the overflow.
36723 This packet is not probed by default; the remote stub must request it
36724 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36726 @item qXfer:btrace-conf:read::@var{offset},@var{length}
36727 @anchor{qXfer btrace-conf read}
36729 Return a description of the current branch trace configuration.
36730 @xref{Branch Trace Configuration Format}.
36732 This packet is not probed by default; the remote stub must request it
36733 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36735 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
36736 @anchor{qXfer executable filename read}
36737 Return the full absolute name of the file that was executed to create
36738 a process running on the remote system. The annex specifies the
36739 numeric process ID of the process to query, encoded as a hexadecimal
36740 number. If the annex part is empty the remote stub should return the
36741 filename corresponding to the currently executing process.
36743 This packet is not probed by default; the remote stub must request it,
36744 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36746 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36747 @anchor{qXfer target description read}
36748 Access the @dfn{target description}. @xref{Target Descriptions}. The
36749 annex specifies which XML document to access. The main description is
36750 always loaded from the @samp{target.xml} annex.
36752 This packet is not probed by default; the remote stub must request it,
36753 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36755 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36756 @anchor{qXfer library list read}
36757 Access the target's list of loaded libraries. @xref{Library List Format}.
36758 The annex part of the generic @samp{qXfer} packet must be empty
36759 (@pxref{qXfer read}).
36761 Targets which maintain a list of libraries in the program's memory do
36762 not need to implement this packet; it is designed for platforms where
36763 the operating system manages the list of loaded libraries.
36765 This packet is not probed by default; the remote stub must request it,
36766 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36768 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36769 @anchor{qXfer svr4 library list read}
36770 Access the target's list of loaded libraries when the target is an SVR4
36771 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36772 of the generic @samp{qXfer} packet must be empty unless the remote
36773 stub indicated it supports the augmented form of this packet
36774 by supplying an appropriate @samp{qSupported} response
36775 (@pxref{qXfer read}, @ref{qSupported}).
36777 This packet is optional for better performance on SVR4 targets.
36778 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36780 This packet is not probed by default; the remote stub must request it,
36781 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36783 If the remote stub indicates it supports the augmented form of this
36784 packet then the annex part of the generic @samp{qXfer} packet may
36785 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
36786 arguments. The currently supported arguments are:
36789 @item start=@var{address}
36790 A hexadecimal number specifying the address of the @samp{struct
36791 link_map} to start reading the library list from. If unset or zero
36792 then the first @samp{struct link_map} in the library list will be
36793 chosen as the starting point.
36795 @item prev=@var{address}
36796 A hexadecimal number specifying the address of the @samp{struct
36797 link_map} immediately preceding the @samp{struct link_map}
36798 specified by the @samp{start} argument. If unset or zero then
36799 the remote stub will expect that no @samp{struct link_map}
36800 exists prior to the starting point.
36804 Arguments that are not understood by the remote stub will be silently
36807 @item qXfer:memory-map:read::@var{offset},@var{length}
36808 @anchor{qXfer memory map read}
36809 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
36810 annex part of the generic @samp{qXfer} packet must be empty
36811 (@pxref{qXfer read}).
36813 This packet is not probed by default; the remote stub must request it,
36814 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36816 @item qXfer:sdata:read::@var{offset},@var{length}
36817 @anchor{qXfer sdata read}
36819 Read contents of the extra collected static tracepoint marker
36820 information. The annex part of the generic @samp{qXfer} packet must
36821 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
36824 This packet is not probed by default; the remote stub must request it,
36825 by supplying an appropriate @samp{qSupported} response
36826 (@pxref{qSupported}).
36828 @item qXfer:siginfo:read::@var{offset},@var{length}
36829 @anchor{qXfer siginfo read}
36830 Read contents of the extra signal information on the target
36831 system. The annex part of the generic @samp{qXfer} packet must be
36832 empty (@pxref{qXfer read}).
36834 This packet is not probed by default; the remote stub must request it,
36835 by supplying an appropriate @samp{qSupported} response
36836 (@pxref{qSupported}).
36838 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
36839 @anchor{qXfer spu read}
36840 Read contents of an @code{spufs} file on the target system. The
36841 annex specifies which file to read; it must be of the form
36842 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36843 in the target process, and @var{name} identifes the @code{spufs} file
36844 in that context to be accessed.
36846 This packet is not probed by default; the remote stub must request it,
36847 by supplying an appropriate @samp{qSupported} response
36848 (@pxref{qSupported}).
36850 @item qXfer:threads:read::@var{offset},@var{length}
36851 @anchor{qXfer threads read}
36852 Access the list of threads on target. @xref{Thread List Format}. The
36853 annex part of the generic @samp{qXfer} packet must be empty
36854 (@pxref{qXfer read}).
36856 This packet is not probed by default; the remote stub must request it,
36857 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36859 @item qXfer:traceframe-info:read::@var{offset},@var{length}
36860 @anchor{qXfer traceframe info read}
36862 Return a description of the current traceframe's contents.
36863 @xref{Traceframe Info Format}. The annex part of the generic
36864 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
36866 This packet is not probed by default; the remote stub must request it,
36867 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36869 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
36870 @anchor{qXfer unwind info block}
36872 Return the unwind information block for @var{pc}. This packet is used
36873 on OpenVMS/ia64 to ask the kernel unwind information.
36875 This packet is not probed by default.
36877 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
36878 @anchor{qXfer fdpic loadmap read}
36879 Read contents of @code{loadmap}s on the target system. The
36880 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
36881 executable @code{loadmap} or interpreter @code{loadmap} to read.
36883 This packet is not probed by default; the remote stub must request it,
36884 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36886 @item qXfer:osdata:read::@var{offset},@var{length}
36887 @anchor{qXfer osdata read}
36888 Access the target's @dfn{operating system information}.
36889 @xref{Operating System Information}.
36896 Data @var{data} (@pxref{Binary Data}) has been read from the
36897 target. There may be more data at a higher address (although
36898 it is permitted to return @samp{m} even for the last valid
36899 block of data, as long as at least one byte of data was read).
36900 It is possible for @var{data} to have fewer bytes than the @var{length} in the
36904 Data @var{data} (@pxref{Binary Data}) has been read from the target.
36905 There is no more data to be read. It is possible for @var{data} to
36906 have fewer bytes than the @var{length} in the request.
36909 The @var{offset} in the request is at the end of the data.
36910 There is no more data to be read.
36913 The request was malformed, or @var{annex} was invalid.
36916 The offset was invalid, or there was an error encountered reading the data.
36917 The @var{nn} part is a hex-encoded @code{errno} value.
36920 An empty reply indicates the @var{object} string was not recognized by
36921 the stub, or that the object does not support reading.
36924 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
36925 @cindex write data into object, remote request
36926 @anchor{qXfer write}
36927 Write uninterpreted bytes into the target's special data area
36928 identified by the keyword @var{object}, starting at @var{offset} bytes
36929 into the data. The binary-encoded data (@pxref{Binary Data}) to be
36930 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
36931 is specific to @var{object}; it can supply additional details about what data
36934 Here are the specific requests of this form defined so far. All
36935 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
36936 formats, listed below.
36939 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
36940 @anchor{qXfer siginfo write}
36941 Write @var{data} to the extra signal information on the target system.
36942 The annex part of the generic @samp{qXfer} packet must be
36943 empty (@pxref{qXfer write}).
36945 This packet is not probed by default; the remote stub must request it,
36946 by supplying an appropriate @samp{qSupported} response
36947 (@pxref{qSupported}).
36949 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
36950 @anchor{qXfer spu write}
36951 Write @var{data} to an @code{spufs} file on the target system. The
36952 annex specifies which file to write; it must be of the form
36953 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36954 in the target process, and @var{name} identifes the @code{spufs} file
36955 in that context to be accessed.
36957 This packet is not probed by default; the remote stub must request it,
36958 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36964 @var{nn} (hex encoded) is the number of bytes written.
36965 This may be fewer bytes than supplied in the request.
36968 The request was malformed, or @var{annex} was invalid.
36971 The offset was invalid, or there was an error encountered writing the data.
36972 The @var{nn} part is a hex-encoded @code{errno} value.
36975 An empty reply indicates the @var{object} string was not
36976 recognized by the stub, or that the object does not support writing.
36979 @item qXfer:@var{object}:@var{operation}:@dots{}
36980 Requests of this form may be added in the future. When a stub does
36981 not recognize the @var{object} keyword, or its support for
36982 @var{object} does not recognize the @var{operation} keyword, the stub
36983 must respond with an empty packet.
36985 @item qAttached:@var{pid}
36986 @cindex query attached, remote request
36987 @cindex @samp{qAttached} packet
36988 Return an indication of whether the remote server attached to an
36989 existing process or created a new process. When the multiprocess
36990 protocol extensions are supported (@pxref{multiprocess extensions}),
36991 @var{pid} is an integer in hexadecimal format identifying the target
36992 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
36993 the query packet will be simplified as @samp{qAttached}.
36995 This query is used, for example, to know whether the remote process
36996 should be detached or killed when a @value{GDBN} session is ended with
36997 the @code{quit} command.
37002 The remote server attached to an existing process.
37004 The remote server created a new process.
37006 A badly formed request or an error was encountered.
37010 Enable branch tracing for the current thread using Branch Trace Store.
37015 Branch tracing has been enabled.
37017 A badly formed request or an error was encountered.
37021 Enable branch tracing for the current thread using Intel(R) Processor Trace.
37026 Branch tracing has been enabled.
37028 A badly formed request or an error was encountered.
37032 Disable branch tracing for the current thread.
37037 Branch tracing has been disabled.
37039 A badly formed request or an error was encountered.
37042 @item Qbtrace-conf:bts:size=@var{value}
37043 Set the requested ring buffer size for new threads that use the
37044 btrace recording method in bts format.
37049 The ring buffer size has been set.
37051 A badly formed request or an error was encountered.
37054 @item Qbtrace-conf:pt:size=@var{value}
37055 Set the requested ring buffer size for new threads that use the
37056 btrace recording method in pt format.
37061 The ring buffer size has been set.
37063 A badly formed request or an error was encountered.
37068 @node Architecture-Specific Protocol Details
37069 @section Architecture-Specific Protocol Details
37071 This section describes how the remote protocol is applied to specific
37072 target architectures. Also see @ref{Standard Target Features}, for
37073 details of XML target descriptions for each architecture.
37076 * ARM-Specific Protocol Details::
37077 * MIPS-Specific Protocol Details::
37080 @node ARM-Specific Protocol Details
37081 @subsection @acronym{ARM}-specific Protocol Details
37084 * ARM Breakpoint Kinds::
37087 @node ARM Breakpoint Kinds
37088 @subsubsection @acronym{ARM} Breakpoint Kinds
37089 @cindex breakpoint kinds, @acronym{ARM}
37091 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37096 16-bit Thumb mode breakpoint.
37099 32-bit Thumb mode (Thumb-2) breakpoint.
37102 32-bit @acronym{ARM} mode breakpoint.
37106 @node MIPS-Specific Protocol Details
37107 @subsection @acronym{MIPS}-specific Protocol Details
37110 * MIPS Register packet Format::
37111 * MIPS Breakpoint Kinds::
37114 @node MIPS Register packet Format
37115 @subsubsection @acronym{MIPS} Register Packet Format
37116 @cindex register packet format, @acronym{MIPS}
37118 The following @code{g}/@code{G} packets have previously been defined.
37119 In the below, some thirty-two bit registers are transferred as
37120 sixty-four bits. Those registers should be zero/sign extended (which?)
37121 to fill the space allocated. Register bytes are transferred in target
37122 byte order. The two nibbles within a register byte are transferred
37123 most-significant -- least-significant.
37128 All registers are transferred as thirty-two bit quantities in the order:
37129 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37130 registers; fsr; fir; fp.
37133 All registers are transferred as sixty-four bit quantities (including
37134 thirty-two bit registers such as @code{sr}). The ordering is the same
37139 @node MIPS Breakpoint Kinds
37140 @subsubsection @acronym{MIPS} Breakpoint Kinds
37141 @cindex breakpoint kinds, @acronym{MIPS}
37143 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37148 16-bit @acronym{MIPS16} mode breakpoint.
37151 16-bit @acronym{microMIPS} mode breakpoint.
37154 32-bit standard @acronym{MIPS} mode breakpoint.
37157 32-bit @acronym{microMIPS} mode breakpoint.
37161 @node Tracepoint Packets
37162 @section Tracepoint Packets
37163 @cindex tracepoint packets
37164 @cindex packets, tracepoint
37166 Here we describe the packets @value{GDBN} uses to implement
37167 tracepoints (@pxref{Tracepoints}).
37171 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37172 @cindex @samp{QTDP} packet
37173 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37174 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37175 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37176 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37177 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37178 the number of bytes that the target should copy elsewhere to make room
37179 for the tracepoint. If an @samp{X} is present, it introduces a
37180 tracepoint condition, which consists of a hexadecimal length, followed
37181 by a comma and hex-encoded bytes, in a manner similar to action
37182 encodings as described below. If the trailing @samp{-} is present,
37183 further @samp{QTDP} packets will follow to specify this tracepoint's
37189 The packet was understood and carried out.
37191 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37193 The packet was not recognized.
37196 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37197 Define actions to be taken when a tracepoint is hit. The @var{n} and
37198 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37199 this tracepoint. This packet may only be sent immediately after
37200 another @samp{QTDP} packet that ended with a @samp{-}. If the
37201 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37202 specifying more actions for this tracepoint.
37204 In the series of action packets for a given tracepoint, at most one
37205 can have an @samp{S} before its first @var{action}. If such a packet
37206 is sent, it and the following packets define ``while-stepping''
37207 actions. Any prior packets define ordinary actions --- that is, those
37208 taken when the tracepoint is first hit. If no action packet has an
37209 @samp{S}, then all the packets in the series specify ordinary
37210 tracepoint actions.
37212 The @samp{@var{action}@dots{}} portion of the packet is a series of
37213 actions, concatenated without separators. Each action has one of the
37219 Collect the registers whose bits are set in @var{mask},
37220 a hexadecimal number whose @var{i}'th bit is set if register number
37221 @var{i} should be collected. (The least significant bit is numbered
37222 zero.) Note that @var{mask} may be any number of digits long; it may
37223 not fit in a 32-bit word.
37225 @item M @var{basereg},@var{offset},@var{len}
37226 Collect @var{len} bytes of memory starting at the address in register
37227 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37228 @samp{-1}, then the range has a fixed address: @var{offset} is the
37229 address of the lowest byte to collect. The @var{basereg},
37230 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37231 values (the @samp{-1} value for @var{basereg} is a special case).
37233 @item X @var{len},@var{expr}
37234 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37235 it directs. The agent expression @var{expr} is as described in
37236 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37237 two-digit hex number in the packet; @var{len} is the number of bytes
37238 in the expression (and thus one-half the number of hex digits in the
37243 Any number of actions may be packed together in a single @samp{QTDP}
37244 packet, as long as the packet does not exceed the maximum packet
37245 length (400 bytes, for many stubs). There may be only one @samp{R}
37246 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37247 actions. Any registers referred to by @samp{M} and @samp{X} actions
37248 must be collected by a preceding @samp{R} action. (The
37249 ``while-stepping'' actions are treated as if they were attached to a
37250 separate tracepoint, as far as these restrictions are concerned.)
37255 The packet was understood and carried out.
37257 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37259 The packet was not recognized.
37262 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37263 @cindex @samp{QTDPsrc} packet
37264 Specify a source string of tracepoint @var{n} at address @var{addr}.
37265 This is useful to get accurate reproduction of the tracepoints
37266 originally downloaded at the beginning of the trace run. The @var{type}
37267 is the name of the tracepoint part, such as @samp{cond} for the
37268 tracepoint's conditional expression (see below for a list of types), while
37269 @var{bytes} is the string, encoded in hexadecimal.
37271 @var{start} is the offset of the @var{bytes} within the overall source
37272 string, while @var{slen} is the total length of the source string.
37273 This is intended for handling source strings that are longer than will
37274 fit in a single packet.
37275 @c Add detailed example when this info is moved into a dedicated
37276 @c tracepoint descriptions section.
37278 The available string types are @samp{at} for the location,
37279 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37280 @value{GDBN} sends a separate packet for each command in the action
37281 list, in the same order in which the commands are stored in the list.
37283 The target does not need to do anything with source strings except
37284 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37287 Although this packet is optional, and @value{GDBN} will only send it
37288 if the target replies with @samp{TracepointSource} @xref{General
37289 Query Packets}, it makes both disconnected tracing and trace files
37290 much easier to use. Otherwise the user must be careful that the
37291 tracepoints in effect while looking at trace frames are identical to
37292 the ones in effect during the trace run; even a small discrepancy
37293 could cause @samp{tdump} not to work, or a particular trace frame not
37296 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
37297 @cindex define trace state variable, remote request
37298 @cindex @samp{QTDV} packet
37299 Create a new trace state variable, number @var{n}, with an initial
37300 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37301 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37302 the option of not using this packet for initial values of zero; the
37303 target should simply create the trace state variables as they are
37304 mentioned in expressions. The value @var{builtin} should be 1 (one)
37305 if the trace state variable is builtin and 0 (zero) if it is not builtin.
37306 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
37307 @samp{qTsV} packet had it set. The contents of @var{name} is the
37308 hex-encoded name (without the leading @samp{$}) of the trace state
37311 @item QTFrame:@var{n}
37312 @cindex @samp{QTFrame} packet
37313 Select the @var{n}'th tracepoint frame from the buffer, and use the
37314 register and memory contents recorded there to answer subsequent
37315 request packets from @value{GDBN}.
37317 A successful reply from the stub indicates that the stub has found the
37318 requested frame. The response is a series of parts, concatenated
37319 without separators, describing the frame we selected. Each part has
37320 one of the following forms:
37324 The selected frame is number @var{n} in the trace frame buffer;
37325 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37326 was no frame matching the criteria in the request packet.
37329 The selected trace frame records a hit of tracepoint number @var{t};
37330 @var{t} is a hexadecimal number.
37334 @item QTFrame:pc:@var{addr}
37335 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37336 currently selected frame whose PC is @var{addr};
37337 @var{addr} is a hexadecimal number.
37339 @item QTFrame:tdp:@var{t}
37340 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37341 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37342 is a hexadecimal number.
37344 @item QTFrame:range:@var{start}:@var{end}
37345 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37346 currently selected frame whose PC is between @var{start} (inclusive)
37347 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37350 @item QTFrame:outside:@var{start}:@var{end}
37351 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37352 frame @emph{outside} the given range of addresses (exclusive).
37355 @cindex @samp{qTMinFTPILen} packet
37356 This packet requests the minimum length of instruction at which a fast
37357 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37358 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37359 it depends on the target system being able to create trampolines in
37360 the first 64K of memory, which might or might not be possible for that
37361 system. So the reply to this packet will be 4 if it is able to
37368 The minimum instruction length is currently unknown.
37370 The minimum instruction length is @var{length}, where @var{length}
37371 is a hexadecimal number greater or equal to 1. A reply
37372 of 1 means that a fast tracepoint may be placed on any instruction
37373 regardless of size.
37375 An error has occurred.
37377 An empty reply indicates that the request is not supported by the stub.
37381 @cindex @samp{QTStart} packet
37382 Begin the tracepoint experiment. Begin collecting data from
37383 tracepoint hits in the trace frame buffer. This packet supports the
37384 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37385 instruction reply packet}).
37388 @cindex @samp{QTStop} packet
37389 End the tracepoint experiment. Stop collecting trace frames.
37391 @item QTEnable:@var{n}:@var{addr}
37393 @cindex @samp{QTEnable} packet
37394 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37395 experiment. If the tracepoint was previously disabled, then collection
37396 of data from it will resume.
37398 @item QTDisable:@var{n}:@var{addr}
37400 @cindex @samp{QTDisable} packet
37401 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37402 experiment. No more data will be collected from the tracepoint unless
37403 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37406 @cindex @samp{QTinit} packet
37407 Clear the table of tracepoints, and empty the trace frame buffer.
37409 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37410 @cindex @samp{QTro} packet
37411 Establish the given ranges of memory as ``transparent''. The stub
37412 will answer requests for these ranges from memory's current contents,
37413 if they were not collected as part of the tracepoint hit.
37415 @value{GDBN} uses this to mark read-only regions of memory, like those
37416 containing program code. Since these areas never change, they should
37417 still have the same contents they did when the tracepoint was hit, so
37418 there's no reason for the stub to refuse to provide their contents.
37420 @item QTDisconnected:@var{value}
37421 @cindex @samp{QTDisconnected} packet
37422 Set the choice to what to do with the tracing run when @value{GDBN}
37423 disconnects from the target. A @var{value} of 1 directs the target to
37424 continue the tracing run, while 0 tells the target to stop tracing if
37425 @value{GDBN} is no longer in the picture.
37428 @cindex @samp{qTStatus} packet
37429 Ask the stub if there is a trace experiment running right now.
37431 The reply has the form:
37435 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37436 @var{running} is a single digit @code{1} if the trace is presently
37437 running, or @code{0} if not. It is followed by semicolon-separated
37438 optional fields that an agent may use to report additional status.
37442 If the trace is not running, the agent may report any of several
37443 explanations as one of the optional fields:
37448 No trace has been run yet.
37450 @item tstop[:@var{text}]:0
37451 The trace was stopped by a user-originated stop command. The optional
37452 @var{text} field is a user-supplied string supplied as part of the
37453 stop command (for instance, an explanation of why the trace was
37454 stopped manually). It is hex-encoded.
37457 The trace stopped because the trace buffer filled up.
37459 @item tdisconnected:0
37460 The trace stopped because @value{GDBN} disconnected from the target.
37462 @item tpasscount:@var{tpnum}
37463 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37465 @item terror:@var{text}:@var{tpnum}
37466 The trace stopped because tracepoint @var{tpnum} had an error. The
37467 string @var{text} is available to describe the nature of the error
37468 (for instance, a divide by zero in the condition expression); it
37472 The trace stopped for some other reason.
37476 Additional optional fields supply statistical and other information.
37477 Although not required, they are extremely useful for users monitoring
37478 the progress of a trace run. If a trace has stopped, and these
37479 numbers are reported, they must reflect the state of the just-stopped
37484 @item tframes:@var{n}
37485 The number of trace frames in the buffer.
37487 @item tcreated:@var{n}
37488 The total number of trace frames created during the run. This may
37489 be larger than the trace frame count, if the buffer is circular.
37491 @item tsize:@var{n}
37492 The total size of the trace buffer, in bytes.
37494 @item tfree:@var{n}
37495 The number of bytes still unused in the buffer.
37497 @item circular:@var{n}
37498 The value of the circular trace buffer flag. @code{1} means that the
37499 trace buffer is circular and old trace frames will be discarded if
37500 necessary to make room, @code{0} means that the trace buffer is linear
37503 @item disconn:@var{n}
37504 The value of the disconnected tracing flag. @code{1} means that
37505 tracing will continue after @value{GDBN} disconnects, @code{0} means
37506 that the trace run will stop.
37510 @item qTP:@var{tp}:@var{addr}
37511 @cindex tracepoint status, remote request
37512 @cindex @samp{qTP} packet
37513 Ask the stub for the current state of tracepoint number @var{tp} at
37514 address @var{addr}.
37518 @item V@var{hits}:@var{usage}
37519 The tracepoint has been hit @var{hits} times so far during the trace
37520 run, and accounts for @var{usage} in the trace buffer. Note that
37521 @code{while-stepping} steps are not counted as separate hits, but the
37522 steps' space consumption is added into the usage number.
37526 @item qTV:@var{var}
37527 @cindex trace state variable value, remote request
37528 @cindex @samp{qTV} packet
37529 Ask the stub for the value of the trace state variable number @var{var}.
37534 The value of the variable is @var{value}. This will be the current
37535 value of the variable if the user is examining a running target, or a
37536 saved value if the variable was collected in the trace frame that the
37537 user is looking at. Note that multiple requests may result in
37538 different reply values, such as when requesting values while the
37539 program is running.
37542 The value of the variable is unknown. This would occur, for example,
37543 if the user is examining a trace frame in which the requested variable
37548 @cindex @samp{qTfP} packet
37550 @cindex @samp{qTsP} packet
37551 These packets request data about tracepoints that are being used by
37552 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37553 of data, and multiple @code{qTsP} to get additional pieces. Replies
37554 to these packets generally take the form of the @code{QTDP} packets
37555 that define tracepoints. (FIXME add detailed syntax)
37558 @cindex @samp{qTfV} packet
37560 @cindex @samp{qTsV} packet
37561 These packets request data about trace state variables that are on the
37562 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37563 and multiple @code{qTsV} to get additional variables. Replies to
37564 these packets follow the syntax of the @code{QTDV} packets that define
37565 trace state variables.
37571 @cindex @samp{qTfSTM} packet
37572 @cindex @samp{qTsSTM} packet
37573 These packets request data about static tracepoint markers that exist
37574 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37575 first piece of data, and multiple @code{qTsSTM} to get additional
37576 pieces. Replies to these packets take the following form:
37580 @item m @var{address}:@var{id}:@var{extra}
37582 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37583 a comma-separated list of markers
37585 (lower case letter @samp{L}) denotes end of list.
37587 An error occurred. The error number @var{nn} is given as hex digits.
37589 An empty reply indicates that the request is not supported by the
37593 The @var{address} is encoded in hex;
37594 @var{id} and @var{extra} are strings encoded in hex.
37596 In response to each query, the target will reply with a list of one or
37597 more markers, separated by commas. @value{GDBN} will respond to each
37598 reply with a request for more markers (using the @samp{qs} form of the
37599 query), until the target responds with @samp{l} (lower-case ell, for
37602 @item qTSTMat:@var{address}
37604 @cindex @samp{qTSTMat} packet
37605 This packets requests data about static tracepoint markers in the
37606 target program at @var{address}. Replies to this packet follow the
37607 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37608 tracepoint markers.
37610 @item QTSave:@var{filename}
37611 @cindex @samp{QTSave} packet
37612 This packet directs the target to save trace data to the file name
37613 @var{filename} in the target's filesystem. The @var{filename} is encoded
37614 as a hex string; the interpretation of the file name (relative vs
37615 absolute, wild cards, etc) is up to the target.
37617 @item qTBuffer:@var{offset},@var{len}
37618 @cindex @samp{qTBuffer} packet
37619 Return up to @var{len} bytes of the current contents of trace buffer,
37620 starting at @var{offset}. The trace buffer is treated as if it were
37621 a contiguous collection of traceframes, as per the trace file format.
37622 The reply consists as many hex-encoded bytes as the target can deliver
37623 in a packet; it is not an error to return fewer than were asked for.
37624 A reply consisting of just @code{l} indicates that no bytes are
37627 @item QTBuffer:circular:@var{value}
37628 This packet directs the target to use a circular trace buffer if
37629 @var{value} is 1, or a linear buffer if the value is 0.
37631 @item QTBuffer:size:@var{size}
37632 @anchor{QTBuffer-size}
37633 @cindex @samp{QTBuffer size} packet
37634 This packet directs the target to make the trace buffer be of size
37635 @var{size} if possible. A value of @code{-1} tells the target to
37636 use whatever size it prefers.
37638 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37639 @cindex @samp{QTNotes} packet
37640 This packet adds optional textual notes to the trace run. Allowable
37641 types include @code{user}, @code{notes}, and @code{tstop}, the
37642 @var{text} fields are arbitrary strings, hex-encoded.
37646 @subsection Relocate instruction reply packet
37647 When installing fast tracepoints in memory, the target may need to
37648 relocate the instruction currently at the tracepoint address to a
37649 different address in memory. For most instructions, a simple copy is
37650 enough, but, for example, call instructions that implicitly push the
37651 return address on the stack, and relative branches or other
37652 PC-relative instructions require offset adjustment, so that the effect
37653 of executing the instruction at a different address is the same as if
37654 it had executed in the original location.
37656 In response to several of the tracepoint packets, the target may also
37657 respond with a number of intermediate @samp{qRelocInsn} request
37658 packets before the final result packet, to have @value{GDBN} handle
37659 this relocation operation. If a packet supports this mechanism, its
37660 documentation will explicitly say so. See for example the above
37661 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37662 format of the request is:
37665 @item qRelocInsn:@var{from};@var{to}
37667 This requests @value{GDBN} to copy instruction at address @var{from}
37668 to address @var{to}, possibly adjusted so that executing the
37669 instruction at @var{to} has the same effect as executing it at
37670 @var{from}. @value{GDBN} writes the adjusted instruction to target
37671 memory starting at @var{to}.
37676 @item qRelocInsn:@var{adjusted_size}
37677 Informs the stub the relocation is complete. The @var{adjusted_size} is
37678 the length in bytes of resulting relocated instruction sequence.
37680 A badly formed request was detected, or an error was encountered while
37681 relocating the instruction.
37684 @node Host I/O Packets
37685 @section Host I/O Packets
37686 @cindex Host I/O, remote protocol
37687 @cindex file transfer, remote protocol
37689 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37690 operations on the far side of a remote link. For example, Host I/O is
37691 used to upload and download files to a remote target with its own
37692 filesystem. Host I/O uses the same constant values and data structure
37693 layout as the target-initiated File-I/O protocol. However, the
37694 Host I/O packets are structured differently. The target-initiated
37695 protocol relies on target memory to store parameters and buffers.
37696 Host I/O requests are initiated by @value{GDBN}, and the
37697 target's memory is not involved. @xref{File-I/O Remote Protocol
37698 Extension}, for more details on the target-initiated protocol.
37700 The Host I/O request packets all encode a single operation along with
37701 its arguments. They have this format:
37705 @item vFile:@var{operation}: @var{parameter}@dots{}
37706 @var{operation} is the name of the particular request; the target
37707 should compare the entire packet name up to the second colon when checking
37708 for a supported operation. The format of @var{parameter} depends on
37709 the operation. Numbers are always passed in hexadecimal. Negative
37710 numbers have an explicit minus sign (i.e.@: two's complement is not
37711 used). Strings (e.g.@: filenames) are encoded as a series of
37712 hexadecimal bytes. The last argument to a system call may be a
37713 buffer of escaped binary data (@pxref{Binary Data}).
37717 The valid responses to Host I/O packets are:
37721 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37722 @var{result} is the integer value returned by this operation, usually
37723 non-negative for success and -1 for errors. If an error has occured,
37724 @var{errno} will be included in the result specifying a
37725 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37726 operations which return data, @var{attachment} supplies the data as a
37727 binary buffer. Binary buffers in response packets are escaped in the
37728 normal way (@pxref{Binary Data}). See the individual packet
37729 documentation for the interpretation of @var{result} and
37733 An empty response indicates that this operation is not recognized.
37737 These are the supported Host I/O operations:
37740 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
37741 Open a file at @var{filename} and return a file descriptor for it, or
37742 return -1 if an error occurs. The @var{filename} is a string,
37743 @var{flags} is an integer indicating a mask of open flags
37744 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37745 of mode bits to use if the file is created (@pxref{mode_t Values}).
37746 @xref{open}, for details of the open flags and mode values.
37748 @item vFile:close: @var{fd}
37749 Close the open file corresponding to @var{fd} and return 0, or
37750 -1 if an error occurs.
37752 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37753 Read data from the open file corresponding to @var{fd}. Up to
37754 @var{count} bytes will be read from the file, starting at @var{offset}
37755 relative to the start of the file. The target may read fewer bytes;
37756 common reasons include packet size limits and an end-of-file
37757 condition. The number of bytes read is returned. Zero should only be
37758 returned for a successful read at the end of the file, or if
37759 @var{count} was zero.
37761 The data read should be returned as a binary attachment on success.
37762 If zero bytes were read, the response should include an empty binary
37763 attachment (i.e.@: a trailing semicolon). The return value is the
37764 number of target bytes read; the binary attachment may be longer if
37765 some characters were escaped.
37767 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37768 Write @var{data} (a binary buffer) to the open file corresponding
37769 to @var{fd}. Start the write at @var{offset} from the start of the
37770 file. Unlike many @code{write} system calls, there is no
37771 separate @var{count} argument; the length of @var{data} in the
37772 packet is used. @samp{vFile:write} returns the number of bytes written,
37773 which may be shorter than the length of @var{data}, or -1 if an
37776 @item vFile:fstat: @var{fd}
37777 Get information about the open file corresponding to @var{fd}.
37778 On success the information is returned as a binary attachment
37779 and the return value is the size of this attachment in bytes.
37780 If an error occurs the return value is -1. The format of the
37781 returned binary attachment is as described in @ref{struct stat}.
37783 @item vFile:unlink: @var{filename}
37784 Delete the file at @var{filename} on the target. Return 0,
37785 or -1 if an error occurs. The @var{filename} is a string.
37787 @item vFile:readlink: @var{filename}
37788 Read value of symbolic link @var{filename} on the target. Return
37789 the number of bytes read, or -1 if an error occurs.
37791 The data read should be returned as a binary attachment on success.
37792 If zero bytes were read, the response should include an empty binary
37793 attachment (i.e.@: a trailing semicolon). The return value is the
37794 number of target bytes read; the binary attachment may be longer if
37795 some characters were escaped.
37797 @item vFile:setfs: @var{pid}
37798 Select the filesystem on which @code{vFile} operations with
37799 @var{filename} arguments will operate. This is required for
37800 @value{GDBN} to be able to access files on remote targets where
37801 the remote stub does not share a common filesystem with the
37804 If @var{pid} is nonzero, select the filesystem as seen by process
37805 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
37806 the remote stub. Return 0 on success, or -1 if an error occurs.
37807 If @code{vFile:setfs:} indicates success, the selected filesystem
37808 remains selected until the next successful @code{vFile:setfs:}
37814 @section Interrupts
37815 @cindex interrupts (remote protocol)
37817 When a program on the remote target is running, @value{GDBN} may
37818 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
37819 a @code{BREAK} followed by @code{g},
37820 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37822 The precise meaning of @code{BREAK} is defined by the transport
37823 mechanism and may, in fact, be undefined. @value{GDBN} does not
37824 currently define a @code{BREAK} mechanism for any of the network
37825 interfaces except for TCP, in which case @value{GDBN} sends the
37826 @code{telnet} BREAK sequence.
37828 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
37829 transport mechanisms. It is represented by sending the single byte
37830 @code{0x03} without any of the usual packet overhead described in
37831 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
37832 transmitted as part of a packet, it is considered to be packet data
37833 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
37834 (@pxref{X packet}), used for binary downloads, may include an unescaped
37835 @code{0x03} as part of its packet.
37837 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
37838 When Linux kernel receives this sequence from serial port,
37839 it stops execution and connects to gdb.
37841 Stubs are not required to recognize these interrupt mechanisms and the
37842 precise meaning associated with receipt of the interrupt is
37843 implementation defined. If the target supports debugging of multiple
37844 threads and/or processes, it should attempt to interrupt all
37845 currently-executing threads and processes.
37846 If the stub is successful at interrupting the
37847 running program, it should send one of the stop
37848 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
37849 of successfully stopping the program in all-stop mode, and a stop reply
37850 for each stopped thread in non-stop mode.
37851 Interrupts received while the
37852 program is stopped are discarded.
37854 @node Notification Packets
37855 @section Notification Packets
37856 @cindex notification packets
37857 @cindex packets, notification
37859 The @value{GDBN} remote serial protocol includes @dfn{notifications},
37860 packets that require no acknowledgment. Both the GDB and the stub
37861 may send notifications (although the only notifications defined at
37862 present are sent by the stub). Notifications carry information
37863 without incurring the round-trip latency of an acknowledgment, and so
37864 are useful for low-impact communications where occasional packet loss
37867 A notification packet has the form @samp{% @var{data} #
37868 @var{checksum}}, where @var{data} is the content of the notification,
37869 and @var{checksum} is a checksum of @var{data}, computed and formatted
37870 as for ordinary @value{GDBN} packets. A notification's @var{data}
37871 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
37872 receiving a notification, the recipient sends no @samp{+} or @samp{-}
37873 to acknowledge the notification's receipt or to report its corruption.
37875 Every notification's @var{data} begins with a name, which contains no
37876 colon characters, followed by a colon character.
37878 Recipients should silently ignore corrupted notifications and
37879 notifications they do not understand. Recipients should restart
37880 timeout periods on receipt of a well-formed notification, whether or
37881 not they understand it.
37883 Senders should only send the notifications described here when this
37884 protocol description specifies that they are permitted. In the
37885 future, we may extend the protocol to permit existing notifications in
37886 new contexts; this rule helps older senders avoid confusing newer
37889 (Older versions of @value{GDBN} ignore bytes received until they see
37890 the @samp{$} byte that begins an ordinary packet, so new stubs may
37891 transmit notifications without fear of confusing older clients. There
37892 are no notifications defined for @value{GDBN} to send at the moment, but we
37893 assume that most older stubs would ignore them, as well.)
37895 Each notification is comprised of three parts:
37897 @item @var{name}:@var{event}
37898 The notification packet is sent by the side that initiates the
37899 exchange (currently, only the stub does that), with @var{event}
37900 carrying the specific information about the notification, and
37901 @var{name} specifying the name of the notification.
37903 The acknowledge sent by the other side, usually @value{GDBN}, to
37904 acknowledge the exchange and request the event.
37907 The purpose of an asynchronous notification mechanism is to report to
37908 @value{GDBN} that something interesting happened in the remote stub.
37910 The remote stub may send notification @var{name}:@var{event}
37911 at any time, but @value{GDBN} acknowledges the notification when
37912 appropriate. The notification event is pending before @value{GDBN}
37913 acknowledges. Only one notification at a time may be pending; if
37914 additional events occur before @value{GDBN} has acknowledged the
37915 previous notification, they must be queued by the stub for later
37916 synchronous transmission in response to @var{ack} packets from
37917 @value{GDBN}. Because the notification mechanism is unreliable,
37918 the stub is permitted to resend a notification if it believes
37919 @value{GDBN} may not have received it.
37921 Specifically, notifications may appear when @value{GDBN} is not
37922 otherwise reading input from the stub, or when @value{GDBN} is
37923 expecting to read a normal synchronous response or a
37924 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
37925 Notification packets are distinct from any other communication from
37926 the stub so there is no ambiguity.
37928 After receiving a notification, @value{GDBN} shall acknowledge it by
37929 sending a @var{ack} packet as a regular, synchronous request to the
37930 stub. Such acknowledgment is not required to happen immediately, as
37931 @value{GDBN} is permitted to send other, unrelated packets to the
37932 stub first, which the stub should process normally.
37934 Upon receiving a @var{ack} packet, if the stub has other queued
37935 events to report to @value{GDBN}, it shall respond by sending a
37936 normal @var{event}. @value{GDBN} shall then send another @var{ack}
37937 packet to solicit further responses; again, it is permitted to send
37938 other, unrelated packets as well which the stub should process
37941 If the stub receives a @var{ack} packet and there are no additional
37942 @var{event} to report, the stub shall return an @samp{OK} response.
37943 At this point, @value{GDBN} has finished processing a notification
37944 and the stub has completed sending any queued events. @value{GDBN}
37945 won't accept any new notifications until the final @samp{OK} is
37946 received . If further notification events occur, the stub shall send
37947 a new notification, @value{GDBN} shall accept the notification, and
37948 the process shall be repeated.
37950 The process of asynchronous notification can be illustrated by the
37953 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
37956 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
37958 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
37963 The following notifications are defined:
37964 @multitable @columnfractions 0.12 0.12 0.38 0.38
37973 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
37974 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
37975 for information on how these notifications are acknowledged by
37977 @tab Report an asynchronous stop event in non-stop mode.
37981 @node Remote Non-Stop
37982 @section Remote Protocol Support for Non-Stop Mode
37984 @value{GDBN}'s remote protocol supports non-stop debugging of
37985 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
37986 supports non-stop mode, it should report that to @value{GDBN} by including
37987 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
37989 @value{GDBN} typically sends a @samp{QNonStop} packet only when
37990 establishing a new connection with the stub. Entering non-stop mode
37991 does not alter the state of any currently-running threads, but targets
37992 must stop all threads in any already-attached processes when entering
37993 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
37994 probe the target state after a mode change.
37996 In non-stop mode, when an attached process encounters an event that
37997 would otherwise be reported with a stop reply, it uses the
37998 asynchronous notification mechanism (@pxref{Notification Packets}) to
37999 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38000 in all processes are stopped when a stop reply is sent, in non-stop
38001 mode only the thread reporting the stop event is stopped. That is,
38002 when reporting a @samp{S} or @samp{T} response to indicate completion
38003 of a step operation, hitting a breakpoint, or a fault, only the
38004 affected thread is stopped; any other still-running threads continue
38005 to run. When reporting a @samp{W} or @samp{X} response, all running
38006 threads belonging to other attached processes continue to run.
38008 In non-stop mode, the target shall respond to the @samp{?} packet as
38009 follows. First, any incomplete stop reply notification/@samp{vStopped}
38010 sequence in progress is abandoned. The target must begin a new
38011 sequence reporting stop events for all stopped threads, whether or not
38012 it has previously reported those events to @value{GDBN}. The first
38013 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38014 subsequent stop replies are sent as responses to @samp{vStopped} packets
38015 using the mechanism described above. The target must not send
38016 asynchronous stop reply notifications until the sequence is complete.
38017 If all threads are running when the target receives the @samp{?} packet,
38018 or if the target is not attached to any process, it shall respond
38021 If the stub supports non-stop mode, it should also support the
38022 @samp{swbreak} stop reason if software breakpoints are supported, and
38023 the @samp{hwbreak} stop reason if hardware breakpoints are supported
38024 (@pxref{swbreak stop reason}). This is because given the asynchronous
38025 nature of non-stop mode, between the time a thread hits a breakpoint
38026 and the time the event is finally processed by @value{GDBN}, the
38027 breakpoint may have already been removed from the target. Due to
38028 this, @value{GDBN} needs to be able to tell whether a trap stop was
38029 caused by a delayed breakpoint event, which should be ignored, as
38030 opposed to a random trap signal, which should be reported to the user.
38031 Note the @samp{swbreak} feature implies that the target is responsible
38032 for adjusting the PC when a software breakpoint triggers, if
38033 necessary, such as on the x86 architecture.
38035 @node Packet Acknowledgment
38036 @section Packet Acknowledgment
38038 @cindex acknowledgment, for @value{GDBN} remote
38039 @cindex packet acknowledgment, for @value{GDBN} remote
38040 By default, when either the host or the target machine receives a packet,
38041 the first response expected is an acknowledgment: either @samp{+} (to indicate
38042 the package was received correctly) or @samp{-} (to request retransmission).
38043 This mechanism allows the @value{GDBN} remote protocol to operate over
38044 unreliable transport mechanisms, such as a serial line.
38046 In cases where the transport mechanism is itself reliable (such as a pipe or
38047 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38048 It may be desirable to disable them in that case to reduce communication
38049 overhead, or for other reasons. This can be accomplished by means of the
38050 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38052 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38053 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38054 and response format still includes the normal checksum, as described in
38055 @ref{Overview}, but the checksum may be ignored by the receiver.
38057 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38058 no-acknowledgment mode, it should report that to @value{GDBN}
38059 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38060 @pxref{qSupported}.
38061 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38062 disabled via the @code{set remote noack-packet off} command
38063 (@pxref{Remote Configuration}),
38064 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38065 Only then may the stub actually turn off packet acknowledgments.
38066 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38067 response, which can be safely ignored by the stub.
38069 Note that @code{set remote noack-packet} command only affects negotiation
38070 between @value{GDBN} and the stub when subsequent connections are made;
38071 it does not affect the protocol acknowledgment state for any current
38073 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38074 new connection is established,
38075 there is also no protocol request to re-enable the acknowledgments
38076 for the current connection, once disabled.
38081 Example sequence of a target being re-started. Notice how the restart
38082 does not get any direct output:
38087 @emph{target restarts}
38090 <- @code{T001:1234123412341234}
38094 Example sequence of a target being stepped by a single instruction:
38097 -> @code{G1445@dots{}}
38102 <- @code{T001:1234123412341234}
38106 <- @code{1455@dots{}}
38110 @node File-I/O Remote Protocol Extension
38111 @section File-I/O Remote Protocol Extension
38112 @cindex File-I/O remote protocol extension
38115 * File-I/O Overview::
38116 * Protocol Basics::
38117 * The F Request Packet::
38118 * The F Reply Packet::
38119 * The Ctrl-C Message::
38121 * List of Supported Calls::
38122 * Protocol-specific Representation of Datatypes::
38124 * File-I/O Examples::
38127 @node File-I/O Overview
38128 @subsection File-I/O Overview
38129 @cindex file-i/o overview
38131 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38132 target to use the host's file system and console I/O to perform various
38133 system calls. System calls on the target system are translated into a
38134 remote protocol packet to the host system, which then performs the needed
38135 actions and returns a response packet to the target system.
38136 This simulates file system operations even on targets that lack file systems.
38138 The protocol is defined to be independent of both the host and target systems.
38139 It uses its own internal representation of datatypes and values. Both
38140 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38141 translating the system-dependent value representations into the internal
38142 protocol representations when data is transmitted.
38144 The communication is synchronous. A system call is possible only when
38145 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38146 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38147 the target is stopped to allow deterministic access to the target's
38148 memory. Therefore File-I/O is not interruptible by target signals. On
38149 the other hand, it is possible to interrupt File-I/O by a user interrupt
38150 (@samp{Ctrl-C}) within @value{GDBN}.
38152 The target's request to perform a host system call does not finish
38153 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38154 after finishing the system call, the target returns to continuing the
38155 previous activity (continue, step). No additional continue or step
38156 request from @value{GDBN} is required.
38159 (@value{GDBP}) continue
38160 <- target requests 'system call X'
38161 target is stopped, @value{GDBN} executes system call
38162 -> @value{GDBN} returns result
38163 ... target continues, @value{GDBN} returns to wait for the target
38164 <- target hits breakpoint and sends a Txx packet
38167 The protocol only supports I/O on the console and to regular files on
38168 the host file system. Character or block special devices, pipes,
38169 named pipes, sockets or any other communication method on the host
38170 system are not supported by this protocol.
38172 File I/O is not supported in non-stop mode.
38174 @node Protocol Basics
38175 @subsection Protocol Basics
38176 @cindex protocol basics, file-i/o
38178 The File-I/O protocol uses the @code{F} packet as the request as well
38179 as reply packet. Since a File-I/O system call can only occur when
38180 @value{GDBN} is waiting for a response from the continuing or stepping target,
38181 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38182 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38183 This @code{F} packet contains all information needed to allow @value{GDBN}
38184 to call the appropriate host system call:
38188 A unique identifier for the requested system call.
38191 All parameters to the system call. Pointers are given as addresses
38192 in the target memory address space. Pointers to strings are given as
38193 pointer/length pair. Numerical values are given as they are.
38194 Numerical control flags are given in a protocol-specific representation.
38198 At this point, @value{GDBN} has to perform the following actions.
38202 If the parameters include pointer values to data needed as input to a
38203 system call, @value{GDBN} requests this data from the target with a
38204 standard @code{m} packet request. This additional communication has to be
38205 expected by the target implementation and is handled as any other @code{m}
38209 @value{GDBN} translates all value from protocol representation to host
38210 representation as needed. Datatypes are coerced into the host types.
38213 @value{GDBN} calls the system call.
38216 It then coerces datatypes back to protocol representation.
38219 If the system call is expected to return data in buffer space specified
38220 by pointer parameters to the call, the data is transmitted to the
38221 target using a @code{M} or @code{X} packet. This packet has to be expected
38222 by the target implementation and is handled as any other @code{M} or @code{X}
38227 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38228 necessary information for the target to continue. This at least contains
38235 @code{errno}, if has been changed by the system call.
38242 After having done the needed type and value coercion, the target continues
38243 the latest continue or step action.
38245 @node The F Request Packet
38246 @subsection The @code{F} Request Packet
38247 @cindex file-i/o request packet
38248 @cindex @code{F} request packet
38250 The @code{F} request packet has the following format:
38253 @item F@var{call-id},@var{parameter@dots{}}
38255 @var{call-id} is the identifier to indicate the host system call to be called.
38256 This is just the name of the function.
38258 @var{parameter@dots{}} are the parameters to the system call.
38259 Parameters are hexadecimal integer values, either the actual values in case
38260 of scalar datatypes, pointers to target buffer space in case of compound
38261 datatypes and unspecified memory areas, or pointer/length pairs in case
38262 of string parameters. These are appended to the @var{call-id} as a
38263 comma-delimited list. All values are transmitted in ASCII
38264 string representation, pointer/length pairs separated by a slash.
38270 @node The F Reply Packet
38271 @subsection The @code{F} Reply Packet
38272 @cindex file-i/o reply packet
38273 @cindex @code{F} reply packet
38275 The @code{F} reply packet has the following format:
38279 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38281 @var{retcode} is the return code of the system call as hexadecimal value.
38283 @var{errno} is the @code{errno} set by the call, in protocol-specific
38285 This parameter can be omitted if the call was successful.
38287 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38288 case, @var{errno} must be sent as well, even if the call was successful.
38289 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38296 or, if the call was interrupted before the host call has been performed:
38303 assuming 4 is the protocol-specific representation of @code{EINTR}.
38308 @node The Ctrl-C Message
38309 @subsection The @samp{Ctrl-C} Message
38310 @cindex ctrl-c message, in file-i/o protocol
38312 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38313 reply packet (@pxref{The F Reply Packet}),
38314 the target should behave as if it had
38315 gotten a break message. The meaning for the target is ``system call
38316 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38317 (as with a break message) and return to @value{GDBN} with a @code{T02}
38320 It's important for the target to know in which
38321 state the system call was interrupted. There are two possible cases:
38325 The system call hasn't been performed on the host yet.
38328 The system call on the host has been finished.
38332 These two states can be distinguished by the target by the value of the
38333 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38334 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38335 on POSIX systems. In any other case, the target may presume that the
38336 system call has been finished --- successfully or not --- and should behave
38337 as if the break message arrived right after the system call.
38339 @value{GDBN} must behave reliably. If the system call has not been called
38340 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38341 @code{errno} in the packet. If the system call on the host has been finished
38342 before the user requests a break, the full action must be finished by
38343 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38344 The @code{F} packet may only be sent when either nothing has happened
38345 or the full action has been completed.
38348 @subsection Console I/O
38349 @cindex console i/o as part of file-i/o
38351 By default and if not explicitly closed by the target system, the file
38352 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38353 on the @value{GDBN} console is handled as any other file output operation
38354 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38355 by @value{GDBN} so that after the target read request from file descriptor
38356 0 all following typing is buffered until either one of the following
38361 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38363 system call is treated as finished.
38366 The user presses @key{RET}. This is treated as end of input with a trailing
38370 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38371 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38375 If the user has typed more characters than fit in the buffer given to
38376 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38377 either another @code{read(0, @dots{})} is requested by the target, or debugging
38378 is stopped at the user's request.
38381 @node List of Supported Calls
38382 @subsection List of Supported Calls
38383 @cindex list of supported file-i/o calls
38400 @unnumberedsubsubsec open
38401 @cindex open, file-i/o system call
38406 int open(const char *pathname, int flags);
38407 int open(const char *pathname, int flags, mode_t mode);
38411 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38414 @var{flags} is the bitwise @code{OR} of the following values:
38418 If the file does not exist it will be created. The host
38419 rules apply as far as file ownership and time stamps
38423 When used with @code{O_CREAT}, if the file already exists it is
38424 an error and open() fails.
38427 If the file already exists and the open mode allows
38428 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38429 truncated to zero length.
38432 The file is opened in append mode.
38435 The file is opened for reading only.
38438 The file is opened for writing only.
38441 The file is opened for reading and writing.
38445 Other bits are silently ignored.
38449 @var{mode} is the bitwise @code{OR} of the following values:
38453 User has read permission.
38456 User has write permission.
38459 Group has read permission.
38462 Group has write permission.
38465 Others have read permission.
38468 Others have write permission.
38472 Other bits are silently ignored.
38475 @item Return value:
38476 @code{open} returns the new file descriptor or -1 if an error
38483 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38486 @var{pathname} refers to a directory.
38489 The requested access is not allowed.
38492 @var{pathname} was too long.
38495 A directory component in @var{pathname} does not exist.
38498 @var{pathname} refers to a device, pipe, named pipe or socket.
38501 @var{pathname} refers to a file on a read-only filesystem and
38502 write access was requested.
38505 @var{pathname} is an invalid pointer value.
38508 No space on device to create the file.
38511 The process already has the maximum number of files open.
38514 The limit on the total number of files open on the system
38518 The call was interrupted by the user.
38524 @unnumberedsubsubsec close
38525 @cindex close, file-i/o system call
38534 @samp{Fclose,@var{fd}}
38536 @item Return value:
38537 @code{close} returns zero on success, or -1 if an error occurred.
38543 @var{fd} isn't a valid open file descriptor.
38546 The call was interrupted by the user.
38552 @unnumberedsubsubsec read
38553 @cindex read, file-i/o system call
38558 int read(int fd, void *buf, unsigned int count);
38562 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38564 @item Return value:
38565 On success, the number of bytes read is returned.
38566 Zero indicates end of file. If count is zero, read
38567 returns zero as well. On error, -1 is returned.
38573 @var{fd} is not a valid file descriptor or is not open for
38577 @var{bufptr} is an invalid pointer value.
38580 The call was interrupted by the user.
38586 @unnumberedsubsubsec write
38587 @cindex write, file-i/o system call
38592 int write(int fd, const void *buf, unsigned int count);
38596 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38598 @item Return value:
38599 On success, the number of bytes written are returned.
38600 Zero indicates nothing was written. On error, -1
38607 @var{fd} is not a valid file descriptor or is not open for
38611 @var{bufptr} is an invalid pointer value.
38614 An attempt was made to write a file that exceeds the
38615 host-specific maximum file size allowed.
38618 No space on device to write the data.
38621 The call was interrupted by the user.
38627 @unnumberedsubsubsec lseek
38628 @cindex lseek, file-i/o system call
38633 long lseek (int fd, long offset, int flag);
38637 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
38639 @var{flag} is one of:
38643 The offset is set to @var{offset} bytes.
38646 The offset is set to its current location plus @var{offset}
38650 The offset is set to the size of the file plus @var{offset}
38654 @item Return value:
38655 On success, the resulting unsigned offset in bytes from
38656 the beginning of the file is returned. Otherwise, a
38657 value of -1 is returned.
38663 @var{fd} is not a valid open file descriptor.
38666 @var{fd} is associated with the @value{GDBN} console.
38669 @var{flag} is not a proper value.
38672 The call was interrupted by the user.
38678 @unnumberedsubsubsec rename
38679 @cindex rename, file-i/o system call
38684 int rename(const char *oldpath, const char *newpath);
38688 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
38690 @item Return value:
38691 On success, zero is returned. On error, -1 is returned.
38697 @var{newpath} is an existing directory, but @var{oldpath} is not a
38701 @var{newpath} is a non-empty directory.
38704 @var{oldpath} or @var{newpath} is a directory that is in use by some
38708 An attempt was made to make a directory a subdirectory
38712 A component used as a directory in @var{oldpath} or new
38713 path is not a directory. Or @var{oldpath} is a directory
38714 and @var{newpath} exists but is not a directory.
38717 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
38720 No access to the file or the path of the file.
38724 @var{oldpath} or @var{newpath} was too long.
38727 A directory component in @var{oldpath} or @var{newpath} does not exist.
38730 The file is on a read-only filesystem.
38733 The device containing the file has no room for the new
38737 The call was interrupted by the user.
38743 @unnumberedsubsubsec unlink
38744 @cindex unlink, file-i/o system call
38749 int unlink(const char *pathname);
38753 @samp{Funlink,@var{pathnameptr}/@var{len}}
38755 @item Return value:
38756 On success, zero is returned. On error, -1 is returned.
38762 No access to the file or the path of the file.
38765 The system does not allow unlinking of directories.
38768 The file @var{pathname} cannot be unlinked because it's
38769 being used by another process.
38772 @var{pathnameptr} is an invalid pointer value.
38775 @var{pathname} was too long.
38778 A directory component in @var{pathname} does not exist.
38781 A component of the path is not a directory.
38784 The file is on a read-only filesystem.
38787 The call was interrupted by the user.
38793 @unnumberedsubsubsec stat/fstat
38794 @cindex fstat, file-i/o system call
38795 @cindex stat, file-i/o system call
38800 int stat(const char *pathname, struct stat *buf);
38801 int fstat(int fd, struct stat *buf);
38805 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38806 @samp{Ffstat,@var{fd},@var{bufptr}}
38808 @item Return value:
38809 On success, zero is returned. On error, -1 is returned.
38815 @var{fd} is not a valid open file.
38818 A directory component in @var{pathname} does not exist or the
38819 path is an empty string.
38822 A component of the path is not a directory.
38825 @var{pathnameptr} is an invalid pointer value.
38828 No access to the file or the path of the file.
38831 @var{pathname} was too long.
38834 The call was interrupted by the user.
38840 @unnumberedsubsubsec gettimeofday
38841 @cindex gettimeofday, file-i/o system call
38846 int gettimeofday(struct timeval *tv, void *tz);
38850 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
38852 @item Return value:
38853 On success, 0 is returned, -1 otherwise.
38859 @var{tz} is a non-NULL pointer.
38862 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
38868 @unnumberedsubsubsec isatty
38869 @cindex isatty, file-i/o system call
38874 int isatty(int fd);
38878 @samp{Fisatty,@var{fd}}
38880 @item Return value:
38881 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
38887 The call was interrupted by the user.
38892 Note that the @code{isatty} call is treated as a special case: it returns
38893 1 to the target if the file descriptor is attached
38894 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
38895 would require implementing @code{ioctl} and would be more complex than
38900 @unnumberedsubsubsec system
38901 @cindex system, file-i/o system call
38906 int system(const char *command);
38910 @samp{Fsystem,@var{commandptr}/@var{len}}
38912 @item Return value:
38913 If @var{len} is zero, the return value indicates whether a shell is
38914 available. A zero return value indicates a shell is not available.
38915 For non-zero @var{len}, the value returned is -1 on error and the
38916 return status of the command otherwise. Only the exit status of the
38917 command is returned, which is extracted from the host's @code{system}
38918 return value by calling @code{WEXITSTATUS(retval)}. In case
38919 @file{/bin/sh} could not be executed, 127 is returned.
38925 The call was interrupted by the user.
38930 @value{GDBN} takes over the full task of calling the necessary host calls
38931 to perform the @code{system} call. The return value of @code{system} on
38932 the host is simplified before it's returned
38933 to the target. Any termination signal information from the child process
38934 is discarded, and the return value consists
38935 entirely of the exit status of the called command.
38937 Due to security concerns, the @code{system} call is by default refused
38938 by @value{GDBN}. The user has to allow this call explicitly with the
38939 @code{set remote system-call-allowed 1} command.
38942 @item set remote system-call-allowed
38943 @kindex set remote system-call-allowed
38944 Control whether to allow the @code{system} calls in the File I/O
38945 protocol for the remote target. The default is zero (disabled).
38947 @item show remote system-call-allowed
38948 @kindex show remote system-call-allowed
38949 Show whether the @code{system} calls are allowed in the File I/O
38953 @node Protocol-specific Representation of Datatypes
38954 @subsection Protocol-specific Representation of Datatypes
38955 @cindex protocol-specific representation of datatypes, in file-i/o protocol
38958 * Integral Datatypes::
38960 * Memory Transfer::
38965 @node Integral Datatypes
38966 @unnumberedsubsubsec Integral Datatypes
38967 @cindex integral datatypes, in file-i/o protocol
38969 The integral datatypes used in the system calls are @code{int},
38970 @code{unsigned int}, @code{long}, @code{unsigned long},
38971 @code{mode_t}, and @code{time_t}.
38973 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
38974 implemented as 32 bit values in this protocol.
38976 @code{long} and @code{unsigned long} are implemented as 64 bit types.
38978 @xref{Limits}, for corresponding MIN and MAX values (similar to those
38979 in @file{limits.h}) to allow range checking on host and target.
38981 @code{time_t} datatypes are defined as seconds since the Epoch.
38983 All integral datatypes transferred as part of a memory read or write of a
38984 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
38987 @node Pointer Values
38988 @unnumberedsubsubsec Pointer Values
38989 @cindex pointer values, in file-i/o protocol
38991 Pointers to target data are transmitted as they are. An exception
38992 is made for pointers to buffers for which the length isn't
38993 transmitted as part of the function call, namely strings. Strings
38994 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39001 which is a pointer to data of length 18 bytes at position 0x1aaf.
39002 The length is defined as the full string length in bytes, including
39003 the trailing null byte. For example, the string @code{"hello world"}
39004 at address 0x123456 is transmitted as
39010 @node Memory Transfer
39011 @unnumberedsubsubsec Memory Transfer
39012 @cindex memory transfer, in file-i/o protocol
39014 Structured data which is transferred using a memory read or write (for
39015 example, a @code{struct stat}) is expected to be in a protocol-specific format
39016 with all scalar multibyte datatypes being big endian. Translation to
39017 this representation needs to be done both by the target before the @code{F}
39018 packet is sent, and by @value{GDBN} before
39019 it transfers memory to the target. Transferred pointers to structured
39020 data should point to the already-coerced data at any time.
39024 @unnumberedsubsubsec struct stat
39025 @cindex struct stat, in file-i/o protocol
39027 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39028 is defined as follows:
39032 unsigned int st_dev; /* device */
39033 unsigned int st_ino; /* inode */
39034 mode_t st_mode; /* protection */
39035 unsigned int st_nlink; /* number of hard links */
39036 unsigned int st_uid; /* user ID of owner */
39037 unsigned int st_gid; /* group ID of owner */
39038 unsigned int st_rdev; /* device type (if inode device) */
39039 unsigned long st_size; /* total size, in bytes */
39040 unsigned long st_blksize; /* blocksize for filesystem I/O */
39041 unsigned long st_blocks; /* number of blocks allocated */
39042 time_t st_atime; /* time of last access */
39043 time_t st_mtime; /* time of last modification */
39044 time_t st_ctime; /* time of last change */
39048 The integral datatypes conform to the definitions given in the
39049 appropriate section (see @ref{Integral Datatypes}, for details) so this
39050 structure is of size 64 bytes.
39052 The values of several fields have a restricted meaning and/or
39058 A value of 0 represents a file, 1 the console.
39061 No valid meaning for the target. Transmitted unchanged.
39064 Valid mode bits are described in @ref{Constants}. Any other
39065 bits have currently no meaning for the target.
39070 No valid meaning for the target. Transmitted unchanged.
39075 These values have a host and file system dependent
39076 accuracy. Especially on Windows hosts, the file system may not
39077 support exact timing values.
39080 The target gets a @code{struct stat} of the above representation and is
39081 responsible for coercing it to the target representation before
39084 Note that due to size differences between the host, target, and protocol
39085 representations of @code{struct stat} members, these members could eventually
39086 get truncated on the target.
39088 @node struct timeval
39089 @unnumberedsubsubsec struct timeval
39090 @cindex struct timeval, in file-i/o protocol
39092 The buffer of type @code{struct timeval} used by the File-I/O protocol
39093 is defined as follows:
39097 time_t tv_sec; /* second */
39098 long tv_usec; /* microsecond */
39102 The integral datatypes conform to the definitions given in the
39103 appropriate section (see @ref{Integral Datatypes}, for details) so this
39104 structure is of size 8 bytes.
39107 @subsection Constants
39108 @cindex constants, in file-i/o protocol
39110 The following values are used for the constants inside of the
39111 protocol. @value{GDBN} and target are responsible for translating these
39112 values before and after the call as needed.
39123 @unnumberedsubsubsec Open Flags
39124 @cindex open flags, in file-i/o protocol
39126 All values are given in hexadecimal representation.
39138 @node mode_t Values
39139 @unnumberedsubsubsec mode_t Values
39140 @cindex mode_t values, in file-i/o protocol
39142 All values are given in octal representation.
39159 @unnumberedsubsubsec Errno Values
39160 @cindex errno values, in file-i/o protocol
39162 All values are given in decimal representation.
39187 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39188 any error value not in the list of supported error numbers.
39191 @unnumberedsubsubsec Lseek Flags
39192 @cindex lseek flags, in file-i/o protocol
39201 @unnumberedsubsubsec Limits
39202 @cindex limits, in file-i/o protocol
39204 All values are given in decimal representation.
39207 INT_MIN -2147483648
39209 UINT_MAX 4294967295
39210 LONG_MIN -9223372036854775808
39211 LONG_MAX 9223372036854775807
39212 ULONG_MAX 18446744073709551615
39215 @node File-I/O Examples
39216 @subsection File-I/O Examples
39217 @cindex file-i/o examples
39219 Example sequence of a write call, file descriptor 3, buffer is at target
39220 address 0x1234, 6 bytes should be written:
39223 <- @code{Fwrite,3,1234,6}
39224 @emph{request memory read from target}
39227 @emph{return "6 bytes written"}
39231 Example sequence of a read call, file descriptor 3, buffer is at target
39232 address 0x1234, 6 bytes should be read:
39235 <- @code{Fread,3,1234,6}
39236 @emph{request memory write to target}
39237 -> @code{X1234,6:XXXXXX}
39238 @emph{return "6 bytes read"}
39242 Example sequence of a read call, call fails on the host due to invalid
39243 file descriptor (@code{EBADF}):
39246 <- @code{Fread,3,1234,6}
39250 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39254 <- @code{Fread,3,1234,6}
39259 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39263 <- @code{Fread,3,1234,6}
39264 -> @code{X1234,6:XXXXXX}
39268 @node Library List Format
39269 @section Library List Format
39270 @cindex library list format, remote protocol
39272 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39273 same process as your application to manage libraries. In this case,
39274 @value{GDBN} can use the loader's symbol table and normal memory
39275 operations to maintain a list of shared libraries. On other
39276 platforms, the operating system manages loaded libraries.
39277 @value{GDBN} can not retrieve the list of currently loaded libraries
39278 through memory operations, so it uses the @samp{qXfer:libraries:read}
39279 packet (@pxref{qXfer library list read}) instead. The remote stub
39280 queries the target's operating system and reports which libraries
39283 The @samp{qXfer:libraries:read} packet returns an XML document which
39284 lists loaded libraries and their offsets. Each library has an
39285 associated name and one or more segment or section base addresses,
39286 which report where the library was loaded in memory.
39288 For the common case of libraries that are fully linked binaries, the
39289 library should have a list of segments. If the target supports
39290 dynamic linking of a relocatable object file, its library XML element
39291 should instead include a list of allocated sections. The segment or
39292 section bases are start addresses, not relocation offsets; they do not
39293 depend on the library's link-time base addresses.
39295 @value{GDBN} must be linked with the Expat library to support XML
39296 library lists. @xref{Expat}.
39298 A simple memory map, with one loaded library relocated by a single
39299 offset, looks like this:
39303 <library name="/lib/libc.so.6">
39304 <segment address="0x10000000"/>
39309 Another simple memory map, with one loaded library with three
39310 allocated sections (.text, .data, .bss), looks like this:
39314 <library name="sharedlib.o">
39315 <section address="0x10000000"/>
39316 <section address="0x20000000"/>
39317 <section address="0x30000000"/>
39322 The format of a library list is described by this DTD:
39325 <!-- library-list: Root element with versioning -->
39326 <!ELEMENT library-list (library)*>
39327 <!ATTLIST library-list version CDATA #FIXED "1.0">
39328 <!ELEMENT library (segment*, section*)>
39329 <!ATTLIST library name CDATA #REQUIRED>
39330 <!ELEMENT segment EMPTY>
39331 <!ATTLIST segment address CDATA #REQUIRED>
39332 <!ELEMENT section EMPTY>
39333 <!ATTLIST section address CDATA #REQUIRED>
39336 In addition, segments and section descriptors cannot be mixed within a
39337 single library element, and you must supply at least one segment or
39338 section for each library.
39340 @node Library List Format for SVR4 Targets
39341 @section Library List Format for SVR4 Targets
39342 @cindex library list format, remote protocol
39344 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39345 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39346 shared libraries. Still a special library list provided by this packet is
39347 more efficient for the @value{GDBN} remote protocol.
39349 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39350 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39351 target, the following parameters are reported:
39355 @code{name}, the absolute file name from the @code{l_name} field of
39356 @code{struct link_map}.
39358 @code{lm} with address of @code{struct link_map} used for TLS
39359 (Thread Local Storage) access.
39361 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39362 @code{struct link_map}. For prelinked libraries this is not an absolute
39363 memory address. It is a displacement of absolute memory address against
39364 address the file was prelinked to during the library load.
39366 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39369 Additionally the single @code{main-lm} attribute specifies address of
39370 @code{struct link_map} used for the main executable. This parameter is used
39371 for TLS access and its presence is optional.
39373 @value{GDBN} must be linked with the Expat library to support XML
39374 SVR4 library lists. @xref{Expat}.
39376 A simple memory map, with two loaded libraries (which do not use prelink),
39380 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39381 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39383 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39385 </library-list-svr>
39388 The format of an SVR4 library list is described by this DTD:
39391 <!-- library-list-svr4: Root element with versioning -->
39392 <!ELEMENT library-list-svr4 (library)*>
39393 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39394 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39395 <!ELEMENT library EMPTY>
39396 <!ATTLIST library name CDATA #REQUIRED>
39397 <!ATTLIST library lm CDATA #REQUIRED>
39398 <!ATTLIST library l_addr CDATA #REQUIRED>
39399 <!ATTLIST library l_ld CDATA #REQUIRED>
39402 @node Memory Map Format
39403 @section Memory Map Format
39404 @cindex memory map format
39406 To be able to write into flash memory, @value{GDBN} needs to obtain a
39407 memory map from the target. This section describes the format of the
39410 The memory map is obtained using the @samp{qXfer:memory-map:read}
39411 (@pxref{qXfer memory map read}) packet and is an XML document that
39412 lists memory regions.
39414 @value{GDBN} must be linked with the Expat library to support XML
39415 memory maps. @xref{Expat}.
39417 The top-level structure of the document is shown below:
39420 <?xml version="1.0"?>
39421 <!DOCTYPE memory-map
39422 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39423 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39429 Each region can be either:
39434 A region of RAM starting at @var{addr} and extending for @var{length}
39438 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39443 A region of read-only memory:
39446 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39451 A region of flash memory, with erasure blocks @var{blocksize}
39455 <memory type="flash" start="@var{addr}" length="@var{length}">
39456 <property name="blocksize">@var{blocksize}</property>
39462 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39463 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39464 packets to write to addresses in such ranges.
39466 The formal DTD for memory map format is given below:
39469 <!-- ................................................... -->
39470 <!-- Memory Map XML DTD ................................ -->
39471 <!-- File: memory-map.dtd .............................. -->
39472 <!-- .................................... .............. -->
39473 <!-- memory-map.dtd -->
39474 <!-- memory-map: Root element with versioning -->
39475 <!ELEMENT memory-map (memory | property)>
39476 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39477 <!ELEMENT memory (property)>
39478 <!-- memory: Specifies a memory region,
39479 and its type, or device. -->
39480 <!ATTLIST memory type CDATA #REQUIRED
39481 start CDATA #REQUIRED
39482 length CDATA #REQUIRED
39483 device CDATA #IMPLIED>
39484 <!-- property: Generic attribute tag -->
39485 <!ELEMENT property (#PCDATA | property)*>
39486 <!ATTLIST property name CDATA #REQUIRED>
39489 @node Thread List Format
39490 @section Thread List Format
39491 @cindex thread list format
39493 To efficiently update the list of threads and their attributes,
39494 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39495 (@pxref{qXfer threads read}) and obtains the XML document with
39496 the following structure:
39499 <?xml version="1.0"?>
39501 <thread id="id" core="0">
39502 ... description ...
39507 Each @samp{thread} element must have the @samp{id} attribute that
39508 identifies the thread (@pxref{thread-id syntax}). The
39509 @samp{core} attribute, if present, specifies which processor core
39510 the thread was last executing on. The content of the of @samp{thread}
39511 element is interpreted as human-readable auxilliary information.
39513 @node Traceframe Info Format
39514 @section Traceframe Info Format
39515 @cindex traceframe info format
39517 To be able to know which objects in the inferior can be examined when
39518 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39519 memory ranges, registers and trace state variables that have been
39520 collected in a traceframe.
39522 This list is obtained using the @samp{qXfer:traceframe-info:read}
39523 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39525 @value{GDBN} must be linked with the Expat library to support XML
39526 traceframe info discovery. @xref{Expat}.
39528 The top-level structure of the document is shown below:
39531 <?xml version="1.0"?>
39532 <!DOCTYPE traceframe-info
39533 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39534 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39540 Each traceframe block can be either:
39545 A region of collected memory starting at @var{addr} and extending for
39546 @var{length} bytes from there:
39549 <memory start="@var{addr}" length="@var{length}"/>
39553 A block indicating trace state variable numbered @var{number} has been
39557 <tvar id="@var{number}"/>
39562 The formal DTD for the traceframe info format is given below:
39565 <!ELEMENT traceframe-info (memory | tvar)* >
39566 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39568 <!ELEMENT memory EMPTY>
39569 <!ATTLIST memory start CDATA #REQUIRED
39570 length CDATA #REQUIRED>
39572 <!ATTLIST tvar id CDATA #REQUIRED>
39575 @node Branch Trace Format
39576 @section Branch Trace Format
39577 @cindex branch trace format
39579 In order to display the branch trace of an inferior thread,
39580 @value{GDBN} needs to obtain the list of branches. This list is
39581 represented as list of sequential code blocks that are connected via
39582 branches. The code in each block has been executed sequentially.
39584 This list is obtained using the @samp{qXfer:btrace:read}
39585 (@pxref{qXfer btrace read}) packet and is an XML document.
39587 @value{GDBN} must be linked with the Expat library to support XML
39588 traceframe info discovery. @xref{Expat}.
39590 The top-level structure of the document is shown below:
39593 <?xml version="1.0"?>
39595 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
39596 "http://sourceware.org/gdb/gdb-btrace.dtd">
39605 A block of sequentially executed instructions starting at @var{begin}
39606 and ending at @var{end}:
39609 <block begin="@var{begin}" end="@var{end}"/>
39614 The formal DTD for the branch trace format is given below:
39617 <!ELEMENT btrace (block* | pt) >
39618 <!ATTLIST btrace version CDATA #FIXED "1.0">
39620 <!ELEMENT block EMPTY>
39621 <!ATTLIST block begin CDATA #REQUIRED
39622 end CDATA #REQUIRED>
39624 <!ELEMENT pt (pt-config?, raw?)>
39626 <!ELEMENT pt-config (cpu?)>
39628 <!ELEMENT cpu EMPTY>
39629 <!ATTLIST cpu vendor CDATA #REQUIRED
39630 family CDATA #REQUIRED
39631 model CDATA #REQUIRED
39632 stepping CDATA #REQUIRED>
39634 <!ELEMENT raw (#PCDATA)>
39637 @node Branch Trace Configuration Format
39638 @section Branch Trace Configuration Format
39639 @cindex branch trace configuration format
39641 For each inferior thread, @value{GDBN} can obtain the branch trace
39642 configuration using the @samp{qXfer:btrace-conf:read}
39643 (@pxref{qXfer btrace-conf read}) packet.
39645 The configuration describes the branch trace format and configuration
39646 settings for that format. The following information is described:
39650 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
39653 The size of the @acronym{BTS} ring buffer in bytes.
39656 This thread uses the @dfn{Intel(R) Processor Trace} (@acronym{Intel(R)
39660 The size of the @acronym{Intel(R) PT} ring buffer in bytes.
39664 @value{GDBN} must be linked with the Expat library to support XML
39665 branch trace configuration discovery. @xref{Expat}.
39667 The formal DTD for the branch trace configuration format is given below:
39670 <!ELEMENT btrace-conf (bts?, pt?)>
39671 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
39673 <!ELEMENT bts EMPTY>
39674 <!ATTLIST bts size CDATA #IMPLIED>
39676 <!ELEMENT pt EMPTY>
39677 <!ATTLIST pt size CDATA #IMPLIED>
39680 @include agentexpr.texi
39682 @node Target Descriptions
39683 @appendix Target Descriptions
39684 @cindex target descriptions
39686 One of the challenges of using @value{GDBN} to debug embedded systems
39687 is that there are so many minor variants of each processor
39688 architecture in use. It is common practice for vendors to start with
39689 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
39690 and then make changes to adapt it to a particular market niche. Some
39691 architectures have hundreds of variants, available from dozens of
39692 vendors. This leads to a number of problems:
39696 With so many different customized processors, it is difficult for
39697 the @value{GDBN} maintainers to keep up with the changes.
39699 Since individual variants may have short lifetimes or limited
39700 audiences, it may not be worthwhile to carry information about every
39701 variant in the @value{GDBN} source tree.
39703 When @value{GDBN} does support the architecture of the embedded system
39704 at hand, the task of finding the correct architecture name to give the
39705 @command{set architecture} command can be error-prone.
39708 To address these problems, the @value{GDBN} remote protocol allows a
39709 target system to not only identify itself to @value{GDBN}, but to
39710 actually describe its own features. This lets @value{GDBN} support
39711 processor variants it has never seen before --- to the extent that the
39712 descriptions are accurate, and that @value{GDBN} understands them.
39714 @value{GDBN} must be linked with the Expat library to support XML
39715 target descriptions. @xref{Expat}.
39718 * Retrieving Descriptions:: How descriptions are fetched from a target.
39719 * Target Description Format:: The contents of a target description.
39720 * Predefined Target Types:: Standard types available for target
39722 * Standard Target Features:: Features @value{GDBN} knows about.
39725 @node Retrieving Descriptions
39726 @section Retrieving Descriptions
39728 Target descriptions can be read from the target automatically, or
39729 specified by the user manually. The default behavior is to read the
39730 description from the target. @value{GDBN} retrieves it via the remote
39731 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
39732 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
39733 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
39734 XML document, of the form described in @ref{Target Description
39737 Alternatively, you can specify a file to read for the target description.
39738 If a file is set, the target will not be queried. The commands to
39739 specify a file are:
39742 @cindex set tdesc filename
39743 @item set tdesc filename @var{path}
39744 Read the target description from @var{path}.
39746 @cindex unset tdesc filename
39747 @item unset tdesc filename
39748 Do not read the XML target description from a file. @value{GDBN}
39749 will use the description supplied by the current target.
39751 @cindex show tdesc filename
39752 @item show tdesc filename
39753 Show the filename to read for a target description, if any.
39757 @node Target Description Format
39758 @section Target Description Format
39759 @cindex target descriptions, XML format
39761 A target description annex is an @uref{http://www.w3.org/XML/, XML}
39762 document which complies with the Document Type Definition provided in
39763 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
39764 means you can use generally available tools like @command{xmllint} to
39765 check that your feature descriptions are well-formed and valid.
39766 However, to help people unfamiliar with XML write descriptions for
39767 their targets, we also describe the grammar here.
39769 Target descriptions can identify the architecture of the remote target
39770 and (for some architectures) provide information about custom register
39771 sets. They can also identify the OS ABI of the remote target.
39772 @value{GDBN} can use this information to autoconfigure for your
39773 target, or to warn you if you connect to an unsupported target.
39775 Here is a simple target description:
39778 <target version="1.0">
39779 <architecture>i386:x86-64</architecture>
39784 This minimal description only says that the target uses
39785 the x86-64 architecture.
39787 A target description has the following overall form, with [ ] marking
39788 optional elements and @dots{} marking repeatable elements. The elements
39789 are explained further below.
39792 <?xml version="1.0"?>
39793 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39794 <target version="1.0">
39795 @r{[}@var{architecture}@r{]}
39796 @r{[}@var{osabi}@r{]}
39797 @r{[}@var{compatible}@r{]}
39798 @r{[}@var{feature}@dots{}@r{]}
39803 The description is generally insensitive to whitespace and line
39804 breaks, under the usual common-sense rules. The XML version
39805 declaration and document type declaration can generally be omitted
39806 (@value{GDBN} does not require them), but specifying them may be
39807 useful for XML validation tools. The @samp{version} attribute for
39808 @samp{<target>} may also be omitted, but we recommend
39809 including it; if future versions of @value{GDBN} use an incompatible
39810 revision of @file{gdb-target.dtd}, they will detect and report
39811 the version mismatch.
39813 @subsection Inclusion
39814 @cindex target descriptions, inclusion
39817 @cindex <xi:include>
39820 It can sometimes be valuable to split a target description up into
39821 several different annexes, either for organizational purposes, or to
39822 share files between different possible target descriptions. You can
39823 divide a description into multiple files by replacing any element of
39824 the target description with an inclusion directive of the form:
39827 <xi:include href="@var{document}"/>
39831 When @value{GDBN} encounters an element of this form, it will retrieve
39832 the named XML @var{document}, and replace the inclusion directive with
39833 the contents of that document. If the current description was read
39834 using @samp{qXfer}, then so will be the included document;
39835 @var{document} will be interpreted as the name of an annex. If the
39836 current description was read from a file, @value{GDBN} will look for
39837 @var{document} as a file in the same directory where it found the
39838 original description.
39840 @subsection Architecture
39841 @cindex <architecture>
39843 An @samp{<architecture>} element has this form:
39846 <architecture>@var{arch}</architecture>
39849 @var{arch} is one of the architectures from the set accepted by
39850 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39853 @cindex @code{<osabi>}
39855 This optional field was introduced in @value{GDBN} version 7.0.
39856 Previous versions of @value{GDBN} ignore it.
39858 An @samp{<osabi>} element has this form:
39861 <osabi>@var{abi-name}</osabi>
39864 @var{abi-name} is an OS ABI name from the same selection accepted by
39865 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
39867 @subsection Compatible Architecture
39868 @cindex @code{<compatible>}
39870 This optional field was introduced in @value{GDBN} version 7.0.
39871 Previous versions of @value{GDBN} ignore it.
39873 A @samp{<compatible>} element has this form:
39876 <compatible>@var{arch}</compatible>
39879 @var{arch} is one of the architectures from the set accepted by
39880 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39882 A @samp{<compatible>} element is used to specify that the target
39883 is able to run binaries in some other than the main target architecture
39884 given by the @samp{<architecture>} element. For example, on the
39885 Cell Broadband Engine, the main architecture is @code{powerpc:common}
39886 or @code{powerpc:common64}, but the system is able to run binaries
39887 in the @code{spu} architecture as well. The way to describe this
39888 capability with @samp{<compatible>} is as follows:
39891 <architecture>powerpc:common</architecture>
39892 <compatible>spu</compatible>
39895 @subsection Features
39898 Each @samp{<feature>} describes some logical portion of the target
39899 system. Features are currently used to describe available CPU
39900 registers and the types of their contents. A @samp{<feature>} element
39904 <feature name="@var{name}">
39905 @r{[}@var{type}@dots{}@r{]}
39911 Each feature's name should be unique within the description. The name
39912 of a feature does not matter unless @value{GDBN} has some special
39913 knowledge of the contents of that feature; if it does, the feature
39914 should have its standard name. @xref{Standard Target Features}.
39918 Any register's value is a collection of bits which @value{GDBN} must
39919 interpret. The default interpretation is a two's complement integer,
39920 but other types can be requested by name in the register description.
39921 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
39922 Target Types}), and the description can define additional composite types.
39924 Each type element must have an @samp{id} attribute, which gives
39925 a unique (within the containing @samp{<feature>}) name to the type.
39926 Types must be defined before they are used.
39929 Some targets offer vector registers, which can be treated as arrays
39930 of scalar elements. These types are written as @samp{<vector>} elements,
39931 specifying the array element type, @var{type}, and the number of elements,
39935 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
39939 If a register's value is usefully viewed in multiple ways, define it
39940 with a union type containing the useful representations. The
39941 @samp{<union>} element contains one or more @samp{<field>} elements,
39942 each of which has a @var{name} and a @var{type}:
39945 <union id="@var{id}">
39946 <field name="@var{name}" type="@var{type}"/>
39952 If a register's value is composed from several separate values, define
39953 it with a structure type. There are two forms of the @samp{<struct>}
39954 element; a @samp{<struct>} element must either contain only bitfields
39955 or contain no bitfields. If the structure contains only bitfields,
39956 its total size in bytes must be specified, each bitfield must have an
39957 explicit start and end, and bitfields are automatically assigned an
39958 integer type. The field's @var{start} should be less than or
39959 equal to its @var{end}, and zero represents the least significant bit.
39962 <struct id="@var{id}" size="@var{size}">
39963 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39968 If the structure contains no bitfields, then each field has an
39969 explicit type, and no implicit padding is added.
39972 <struct id="@var{id}">
39973 <field name="@var{name}" type="@var{type}"/>
39979 If a register's value is a series of single-bit flags, define it with
39980 a flags type. The @samp{<flags>} element has an explicit @var{size}
39981 and contains one or more @samp{<field>} elements. Each field has a
39982 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
39986 <flags id="@var{id}" size="@var{size}">
39987 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39992 @subsection Registers
39995 Each register is represented as an element with this form:
39998 <reg name="@var{name}"
39999 bitsize="@var{size}"
40000 @r{[}regnum="@var{num}"@r{]}
40001 @r{[}save-restore="@var{save-restore}"@r{]}
40002 @r{[}type="@var{type}"@r{]}
40003 @r{[}group="@var{group}"@r{]}/>
40007 The components are as follows:
40012 The register's name; it must be unique within the target description.
40015 The register's size, in bits.
40018 The register's number. If omitted, a register's number is one greater
40019 than that of the previous register (either in the current feature or in
40020 a preceding feature); the first register in the target description
40021 defaults to zero. This register number is used to read or write
40022 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40023 packets, and registers appear in the @code{g} and @code{G} packets
40024 in order of increasing register number.
40027 Whether the register should be preserved across inferior function
40028 calls; this must be either @code{yes} or @code{no}. The default is
40029 @code{yes}, which is appropriate for most registers except for
40030 some system control registers; this is not related to the target's
40034 The type of the register. It may be a predefined type, a type
40035 defined in the current feature, or one of the special types @code{int}
40036 and @code{float}. @code{int} is an integer type of the correct size
40037 for @var{bitsize}, and @code{float} is a floating point type (in the
40038 architecture's normal floating point format) of the correct size for
40039 @var{bitsize}. The default is @code{int}.
40042 The register group to which this register belongs. It must
40043 be either @code{general}, @code{float}, or @code{vector}. If no
40044 @var{group} is specified, @value{GDBN} will not display the register
40045 in @code{info registers}.
40049 @node Predefined Target Types
40050 @section Predefined Target Types
40051 @cindex target descriptions, predefined types
40053 Type definitions in the self-description can build up composite types
40054 from basic building blocks, but can not define fundamental types. Instead,
40055 standard identifiers are provided by @value{GDBN} for the fundamental
40056 types. The currently supported types are:
40065 Signed integer types holding the specified number of bits.
40072 Unsigned integer types holding the specified number of bits.
40076 Pointers to unspecified code and data. The program counter and
40077 any dedicated return address register may be marked as code
40078 pointers; printing a code pointer converts it into a symbolic
40079 address. The stack pointer and any dedicated address registers
40080 may be marked as data pointers.
40083 Single precision IEEE floating point.
40086 Double precision IEEE floating point.
40089 The 12-byte extended precision format used by ARM FPA registers.
40092 The 10-byte extended precision format used by x87 registers.
40095 32bit @sc{eflags} register used by x86.
40098 32bit @sc{mxcsr} register used by x86.
40102 @node Standard Target Features
40103 @section Standard Target Features
40104 @cindex target descriptions, standard features
40106 A target description must contain either no registers or all the
40107 target's registers. If the description contains no registers, then
40108 @value{GDBN} will assume a default register layout, selected based on
40109 the architecture. If the description contains any registers, the
40110 default layout will not be used; the standard registers must be
40111 described in the target description, in such a way that @value{GDBN}
40112 can recognize them.
40114 This is accomplished by giving specific names to feature elements
40115 which contain standard registers. @value{GDBN} will look for features
40116 with those names and verify that they contain the expected registers;
40117 if any known feature is missing required registers, or if any required
40118 feature is missing, @value{GDBN} will reject the target
40119 description. You can add additional registers to any of the
40120 standard features --- @value{GDBN} will display them just as if
40121 they were added to an unrecognized feature.
40123 This section lists the known features and their expected contents.
40124 Sample XML documents for these features are included in the
40125 @value{GDBN} source tree, in the directory @file{gdb/features}.
40127 Names recognized by @value{GDBN} should include the name of the
40128 company or organization which selected the name, and the overall
40129 architecture to which the feature applies; so e.g.@: the feature
40130 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40132 The names of registers are not case sensitive for the purpose
40133 of recognizing standard features, but @value{GDBN} will only display
40134 registers using the capitalization used in the description.
40137 * AArch64 Features::
40140 * MicroBlaze Features::
40143 * Nios II Features::
40144 * PowerPC Features::
40145 * S/390 and System z Features::
40150 @node AArch64 Features
40151 @subsection AArch64 Features
40152 @cindex target descriptions, AArch64 features
40154 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
40155 targets. It should contain registers @samp{x0} through @samp{x30},
40156 @samp{sp}, @samp{pc}, and @samp{cpsr}.
40158 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
40159 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
40163 @subsection ARM Features
40164 @cindex target descriptions, ARM features
40166 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40168 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40169 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40171 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40172 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40173 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40176 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40177 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40179 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40180 it should contain at least registers @samp{wR0} through @samp{wR15} and
40181 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40182 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40184 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40185 should contain at least registers @samp{d0} through @samp{d15}. If
40186 they are present, @samp{d16} through @samp{d31} should also be included.
40187 @value{GDBN} will synthesize the single-precision registers from
40188 halves of the double-precision registers.
40190 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40191 need to contain registers; it instructs @value{GDBN} to display the
40192 VFP double-precision registers as vectors and to synthesize the
40193 quad-precision registers from pairs of double-precision registers.
40194 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40195 be present and include 32 double-precision registers.
40197 @node i386 Features
40198 @subsection i386 Features
40199 @cindex target descriptions, i386 features
40201 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40202 targets. It should describe the following registers:
40206 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40208 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40210 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40211 @samp{fs}, @samp{gs}
40213 @samp{st0} through @samp{st7}
40215 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40216 @samp{foseg}, @samp{fooff} and @samp{fop}
40219 The register sets may be different, depending on the target.
40221 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40222 describe registers:
40226 @samp{xmm0} through @samp{xmm7} for i386
40228 @samp{xmm0} through @samp{xmm15} for amd64
40233 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40234 @samp{org.gnu.gdb.i386.sse} feature. It should
40235 describe the upper 128 bits of @sc{ymm} registers:
40239 @samp{ymm0h} through @samp{ymm7h} for i386
40241 @samp{ymm0h} through @samp{ymm15h} for amd64
40244 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
40245 Memory Protection Extension (MPX). It should describe the following registers:
40249 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
40251 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
40254 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40255 describe a single register, @samp{orig_eax}.
40257 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
40258 @samp{org.gnu.gdb.i386.avx} feature. It should
40259 describe additional @sc{xmm} registers:
40263 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
40266 It should describe the upper 128 bits of additional @sc{ymm} registers:
40270 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
40274 describe the upper 256 bits of @sc{zmm} registers:
40278 @samp{zmm0h} through @samp{zmm7h} for i386.
40280 @samp{zmm0h} through @samp{zmm15h} for amd64.
40284 describe the additional @sc{zmm} registers:
40288 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
40291 @node MicroBlaze Features
40292 @subsection MicroBlaze Features
40293 @cindex target descriptions, MicroBlaze features
40295 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
40296 targets. It should contain registers @samp{r0} through @samp{r31},
40297 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
40298 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
40299 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
40301 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
40302 If present, it should contain registers @samp{rshr} and @samp{rslr}
40304 @node MIPS Features
40305 @subsection @acronym{MIPS} Features
40306 @cindex target descriptions, @acronym{MIPS} features
40308 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40309 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40310 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40313 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40314 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40315 registers. They may be 32-bit or 64-bit depending on the target.
40317 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40318 it may be optional in a future version of @value{GDBN}. It should
40319 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40320 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40322 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40323 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40324 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40325 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40327 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40328 contain a single register, @samp{restart}, which is used by the
40329 Linux kernel to control restartable syscalls.
40331 @node M68K Features
40332 @subsection M68K Features
40333 @cindex target descriptions, M68K features
40336 @item @samp{org.gnu.gdb.m68k.core}
40337 @itemx @samp{org.gnu.gdb.coldfire.core}
40338 @itemx @samp{org.gnu.gdb.fido.core}
40339 One of those features must be always present.
40340 The feature that is present determines which flavor of m68k is
40341 used. The feature that is present should contain registers
40342 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40343 @samp{sp}, @samp{ps} and @samp{pc}.
40345 @item @samp{org.gnu.gdb.coldfire.fp}
40346 This feature is optional. If present, it should contain registers
40347 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40351 @node Nios II Features
40352 @subsection Nios II Features
40353 @cindex target descriptions, Nios II features
40355 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
40356 targets. It should contain the 32 core registers (@samp{zero},
40357 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
40358 @samp{pc}, and the 16 control registers (@samp{status} through
40361 @node PowerPC Features
40362 @subsection PowerPC Features
40363 @cindex target descriptions, PowerPC features
40365 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40366 targets. It should contain registers @samp{r0} through @samp{r31},
40367 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40368 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40370 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40371 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40373 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40374 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40377 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40378 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40379 will combine these registers with the floating point registers
40380 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40381 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40382 through @samp{vs63}, the set of vector registers for POWER7.
40384 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40385 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40386 @samp{spefscr}. SPE targets should provide 32-bit registers in
40387 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40388 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40389 these to present registers @samp{ev0} through @samp{ev31} to the
40392 @node S/390 and System z Features
40393 @subsection S/390 and System z Features
40394 @cindex target descriptions, S/390 features
40395 @cindex target descriptions, System z features
40397 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
40398 System z targets. It should contain the PSW and the 16 general
40399 registers. In particular, System z targets should provide the 64-bit
40400 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
40401 S/390 targets should provide the 32-bit versions of these registers.
40402 A System z target that runs in 31-bit addressing mode should provide
40403 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
40404 register's upper halves @samp{r0h} through @samp{r15h}, and their
40405 lower halves @samp{r0l} through @samp{r15l}.
40407 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
40408 contain the 64-bit registers @samp{f0} through @samp{f15}, and
40411 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
40412 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
40414 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
40415 contain the register @samp{orig_r2}, which is 64-bit wide on System z
40416 targets and 32-bit otherwise. In addition, the feature may contain
40417 the @samp{last_break} register, whose width depends on the addressing
40418 mode, as well as the @samp{system_call} register, which is always
40421 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
40422 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
40423 @samp{atia}, and @samp{tr0} through @samp{tr15}.
40425 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
40426 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
40427 combined by @value{GDBN} with the floating point registers @samp{f0}
40428 through @samp{f15} to present the 128-bit wide vector registers
40429 @samp{v0} through @samp{v15}. In addition, this feature should
40430 contain the 128-bit wide vector registers @samp{v16} through
40433 @node TIC6x Features
40434 @subsection TMS320C6x Features
40435 @cindex target descriptions, TIC6x features
40436 @cindex target descriptions, TMS320C6x features
40437 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40438 targets. It should contain registers @samp{A0} through @samp{A15},
40439 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40441 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40442 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40443 through @samp{B31}.
40445 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40446 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40448 @node Operating System Information
40449 @appendix Operating System Information
40450 @cindex operating system information
40456 Users of @value{GDBN} often wish to obtain information about the state of
40457 the operating system running on the target---for example the list of
40458 processes, or the list of open files. This section describes the
40459 mechanism that makes it possible. This mechanism is similar to the
40460 target features mechanism (@pxref{Target Descriptions}), but focuses
40461 on a different aspect of target.
40463 Operating system information is retrived from the target via the
40464 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40465 read}). The object name in the request should be @samp{osdata}, and
40466 the @var{annex} identifies the data to be fetched.
40469 @appendixsection Process list
40470 @cindex operating system information, process list
40472 When requesting the process list, the @var{annex} field in the
40473 @samp{qXfer} request should be @samp{processes}. The returned data is
40474 an XML document. The formal syntax of this document is defined in
40475 @file{gdb/features/osdata.dtd}.
40477 An example document is:
40480 <?xml version="1.0"?>
40481 <!DOCTYPE target SYSTEM "osdata.dtd">
40482 <osdata type="processes">
40484 <column name="pid">1</column>
40485 <column name="user">root</column>
40486 <column name="command">/sbin/init</column>
40487 <column name="cores">1,2,3</column>
40492 Each item should include a column whose name is @samp{pid}. The value
40493 of that column should identify the process on the target. The
40494 @samp{user} and @samp{command} columns are optional, and will be
40495 displayed by @value{GDBN}. The @samp{cores} column, if present,
40496 should contain a comma-separated list of cores that this process
40497 is running on. Target may provide additional columns,
40498 which @value{GDBN} currently ignores.
40500 @node Trace File Format
40501 @appendix Trace File Format
40502 @cindex trace file format
40504 The trace file comes in three parts: a header, a textual description
40505 section, and a trace frame section with binary data.
40507 The header has the form @code{\x7fTRACE0\n}. The first byte is
40508 @code{0x7f} so as to indicate that the file contains binary data,
40509 while the @code{0} is a version number that may have different values
40512 The description section consists of multiple lines of @sc{ascii} text
40513 separated by newline characters (@code{0xa}). The lines may include a
40514 variety of optional descriptive or context-setting information, such
40515 as tracepoint definitions or register set size. @value{GDBN} will
40516 ignore any line that it does not recognize. An empty line marks the end
40519 @c FIXME add some specific types of data
40521 The trace frame section consists of a number of consecutive frames.
40522 Each frame begins with a two-byte tracepoint number, followed by a
40523 four-byte size giving the amount of data in the frame. The data in
40524 the frame consists of a number of blocks, each introduced by a
40525 character indicating its type (at least register, memory, and trace
40526 state variable). The data in this section is raw binary, not a
40527 hexadecimal or other encoding; its endianness matches the target's
40530 @c FIXME bi-arch may require endianness/arch info in description section
40533 @item R @var{bytes}
40534 Register block. The number and ordering of bytes matches that of a
40535 @code{g} packet in the remote protocol. Note that these are the
40536 actual bytes, in target order and @value{GDBN} register order, not a
40537 hexadecimal encoding.
40539 @item M @var{address} @var{length} @var{bytes}...
40540 Memory block. This is a contiguous block of memory, at the 8-byte
40541 address @var{address}, with a 2-byte length @var{length}, followed by
40542 @var{length} bytes.
40544 @item V @var{number} @var{value}
40545 Trace state variable block. This records the 8-byte signed value
40546 @var{value} of trace state variable numbered @var{number}.
40550 Future enhancements of the trace file format may include additional types
40553 @node Index Section Format
40554 @appendix @code{.gdb_index} section format
40555 @cindex .gdb_index section format
40556 @cindex index section format
40558 This section documents the index section that is created by @code{save
40559 gdb-index} (@pxref{Index Files}). The index section is
40560 DWARF-specific; some knowledge of DWARF is assumed in this
40563 The mapped index file format is designed to be directly
40564 @code{mmap}able on any architecture. In most cases, a datum is
40565 represented using a little-endian 32-bit integer value, called an
40566 @code{offset_type}. Big endian machines must byte-swap the values
40567 before using them. Exceptions to this rule are noted. The data is
40568 laid out such that alignment is always respected.
40570 A mapped index consists of several areas, laid out in order.
40574 The file header. This is a sequence of values, of @code{offset_type}
40575 unless otherwise noted:
40579 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
40580 Version 4 uses a different hashing function from versions 5 and 6.
40581 Version 6 includes symbols for inlined functions, whereas versions 4
40582 and 5 do not. Version 7 adds attributes to the CU indices in the
40583 symbol table. Version 8 specifies that symbols from DWARF type units
40584 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
40585 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
40587 @value{GDBN} will only read version 4, 5, or 6 indices
40588 by specifying @code{set use-deprecated-index-sections on}.
40589 GDB has a workaround for potentially broken version 7 indices so it is
40590 currently not flagged as deprecated.
40593 The offset, from the start of the file, of the CU list.
40596 The offset, from the start of the file, of the types CU list. Note
40597 that this area can be empty, in which case this offset will be equal
40598 to the next offset.
40601 The offset, from the start of the file, of the address area.
40604 The offset, from the start of the file, of the symbol table.
40607 The offset, from the start of the file, of the constant pool.
40611 The CU list. This is a sequence of pairs of 64-bit little-endian
40612 values, sorted by the CU offset. The first element in each pair is
40613 the offset of a CU in the @code{.debug_info} section. The second
40614 element in each pair is the length of that CU. References to a CU
40615 elsewhere in the map are done using a CU index, which is just the
40616 0-based index into this table. Note that if there are type CUs, then
40617 conceptually CUs and type CUs form a single list for the purposes of
40621 The types CU list. This is a sequence of triplets of 64-bit
40622 little-endian values. In a triplet, the first value is the CU offset,
40623 the second value is the type offset in the CU, and the third value is
40624 the type signature. The types CU list is not sorted.
40627 The address area. The address area consists of a sequence of address
40628 entries. Each address entry has three elements:
40632 The low address. This is a 64-bit little-endian value.
40635 The high address. This is a 64-bit little-endian value. Like
40636 @code{DW_AT_high_pc}, the value is one byte beyond the end.
40639 The CU index. This is an @code{offset_type} value.
40643 The symbol table. This is an open-addressed hash table. The size of
40644 the hash table is always a power of 2.
40646 Each slot in the hash table consists of a pair of @code{offset_type}
40647 values. The first value is the offset of the symbol's name in the
40648 constant pool. The second value is the offset of the CU vector in the
40651 If both values are 0, then this slot in the hash table is empty. This
40652 is ok because while 0 is a valid constant pool index, it cannot be a
40653 valid index for both a string and a CU vector.
40655 The hash value for a table entry is computed by applying an
40656 iterative hash function to the symbol's name. Starting with an
40657 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
40658 the string is incorporated into the hash using the formula depending on the
40663 The formula is @code{r = r * 67 + c - 113}.
40665 @item Versions 5 to 7
40666 The formula is @code{r = r * 67 + tolower (c) - 113}.
40669 The terminating @samp{\0} is not incorporated into the hash.
40671 The step size used in the hash table is computed via
40672 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
40673 value, and @samp{size} is the size of the hash table. The step size
40674 is used to find the next candidate slot when handling a hash
40677 The names of C@t{++} symbols in the hash table are canonicalized. We
40678 don't currently have a simple description of the canonicalization
40679 algorithm; if you intend to create new index sections, you must read
40683 The constant pool. This is simply a bunch of bytes. It is organized
40684 so that alignment is correct: CU vectors are stored first, followed by
40687 A CU vector in the constant pool is a sequence of @code{offset_type}
40688 values. The first value is the number of CU indices in the vector.
40689 Each subsequent value is the index and symbol attributes of a CU in
40690 the CU list. This element in the hash table is used to indicate which
40691 CUs define the symbol and how the symbol is used.
40692 See below for the format of each CU index+attributes entry.
40694 A string in the constant pool is zero-terminated.
40697 Attributes were added to CU index values in @code{.gdb_index} version 7.
40698 If a symbol has multiple uses within a CU then there is one
40699 CU index+attributes value for each use.
40701 The format of each CU index+attributes entry is as follows
40707 This is the index of the CU in the CU list.
40709 These bits are reserved for future purposes and must be zero.
40711 The kind of the symbol in the CU.
40715 This value is reserved and should not be used.
40716 By reserving zero the full @code{offset_type} value is backwards compatible
40717 with previous versions of the index.
40719 The symbol is a type.
40721 The symbol is a variable or an enum value.
40723 The symbol is a function.
40725 Any other kind of symbol.
40727 These values are reserved.
40731 This bit is zero if the value is global and one if it is static.
40733 The determination of whether a symbol is global or static is complicated.
40734 The authorative reference is the file @file{dwarf2read.c} in
40735 @value{GDBN} sources.
40739 This pseudo-code describes the computation of a symbol's kind and
40740 global/static attributes in the index.
40743 is_external = get_attribute (die, DW_AT_external);
40744 language = get_attribute (cu_die, DW_AT_language);
40747 case DW_TAG_typedef:
40748 case DW_TAG_base_type:
40749 case DW_TAG_subrange_type:
40753 case DW_TAG_enumerator:
40755 is_static = (language != CPLUS && language != JAVA);
40757 case DW_TAG_subprogram:
40759 is_static = ! (is_external || language == ADA);
40761 case DW_TAG_constant:
40763 is_static = ! is_external;
40765 case DW_TAG_variable:
40767 is_static = ! is_external;
40769 case DW_TAG_namespace:
40773 case DW_TAG_class_type:
40774 case DW_TAG_interface_type:
40775 case DW_TAG_structure_type:
40776 case DW_TAG_union_type:
40777 case DW_TAG_enumeration_type:
40779 is_static = (language != CPLUS && language != JAVA);
40787 @appendix Manual pages
40791 * gdb man:: The GNU Debugger man page
40792 * gdbserver man:: Remote Server for the GNU Debugger man page
40793 * gcore man:: Generate a core file of a running program
40794 * gdbinit man:: gdbinit scripts
40800 @c man title gdb The GNU Debugger
40802 @c man begin SYNOPSIS gdb
40803 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
40804 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
40805 [@option{-b}@w{ }@var{bps}]
40806 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
40807 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
40808 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
40809 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
40810 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
40813 @c man begin DESCRIPTION gdb
40814 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
40815 going on ``inside'' another program while it executes -- or what another
40816 program was doing at the moment it crashed.
40818 @value{GDBN} can do four main kinds of things (plus other things in support of
40819 these) to help you catch bugs in the act:
40823 Start your program, specifying anything that might affect its behavior.
40826 Make your program stop on specified conditions.
40829 Examine what has happened, when your program has stopped.
40832 Change things in your program, so you can experiment with correcting the
40833 effects of one bug and go on to learn about another.
40836 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
40839 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
40840 commands from the terminal until you tell it to exit with the @value{GDBN}
40841 command @code{quit}. You can get online help from @value{GDBN} itself
40842 by using the command @code{help}.
40844 You can run @code{gdb} with no arguments or options; but the most
40845 usual way to start @value{GDBN} is with one argument or two, specifying an
40846 executable program as the argument:
40852 You can also start with both an executable program and a core file specified:
40858 You can, instead, specify a process ID as a second argument, if you want
40859 to debug a running process:
40867 would attach @value{GDBN} to process @code{1234} (unless you also have a file
40868 named @file{1234}; @value{GDBN} does check for a core file first).
40869 With option @option{-p} you can omit the @var{program} filename.
40871 Here are some of the most frequently needed @value{GDBN} commands:
40873 @c pod2man highlights the right hand side of the @item lines.
40875 @item break [@var{file}:]@var{functiop}
40876 Set a breakpoint at @var{function} (in @var{file}).
40878 @item run [@var{arglist}]
40879 Start your program (with @var{arglist}, if specified).
40882 Backtrace: display the program stack.
40884 @item print @var{expr}
40885 Display the value of an expression.
40888 Continue running your program (after stopping, e.g. at a breakpoint).
40891 Execute next program line (after stopping); step @emph{over} any
40892 function calls in the line.
40894 @item edit [@var{file}:]@var{function}
40895 look at the program line where it is presently stopped.
40897 @item list [@var{file}:]@var{function}
40898 type the text of the program in the vicinity of where it is presently stopped.
40901 Execute next program line (after stopping); step @emph{into} any
40902 function calls in the line.
40904 @item help [@var{name}]
40905 Show information about @value{GDBN} command @var{name}, or general information
40906 about using @value{GDBN}.
40909 Exit from @value{GDBN}.
40913 For full details on @value{GDBN},
40914 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40915 by Richard M. Stallman and Roland H. Pesch. The same text is available online
40916 as the @code{gdb} entry in the @code{info} program.
40920 @c man begin OPTIONS gdb
40921 Any arguments other than options specify an executable
40922 file and core file (or process ID); that is, the first argument
40923 encountered with no
40924 associated option flag is equivalent to a @option{-se} option, and the second,
40925 if any, is equivalent to a @option{-c} option if it's the name of a file.
40927 both long and short forms; both are shown here. The long forms are also
40928 recognized if you truncate them, so long as enough of the option is
40929 present to be unambiguous. (If you prefer, you can flag option
40930 arguments with @option{+} rather than @option{-}, though we illustrate the
40931 more usual convention.)
40933 All the options and command line arguments you give are processed
40934 in sequential order. The order makes a difference when the @option{-x}
40940 List all options, with brief explanations.
40942 @item -symbols=@var{file}
40943 @itemx -s @var{file}
40944 Read symbol table from file @var{file}.
40947 Enable writing into executable and core files.
40949 @item -exec=@var{file}
40950 @itemx -e @var{file}
40951 Use file @var{file} as the executable file to execute when
40952 appropriate, and for examining pure data in conjunction with a core
40955 @item -se=@var{file}
40956 Read symbol table from file @var{file} and use it as the executable
40959 @item -core=@var{file}
40960 @itemx -c @var{file}
40961 Use file @var{file} as a core dump to examine.
40963 @item -command=@var{file}
40964 @itemx -x @var{file}
40965 Execute @value{GDBN} commands from file @var{file}.
40967 @item -ex @var{command}
40968 Execute given @value{GDBN} @var{command}.
40970 @item -directory=@var{directory}
40971 @itemx -d @var{directory}
40972 Add @var{directory} to the path to search for source files.
40975 Do not execute commands from @file{~/.gdbinit}.
40979 Do not execute commands from any @file{.gdbinit} initialization files.
40983 ``Quiet''. Do not print the introductory and copyright messages. These
40984 messages are also suppressed in batch mode.
40987 Run in batch mode. Exit with status @code{0} after processing all the command
40988 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
40989 Exit with nonzero status if an error occurs in executing the @value{GDBN}
40990 commands in the command files.
40992 Batch mode may be useful for running @value{GDBN} as a filter, for example to
40993 download and run a program on another computer; in order to make this
40994 more useful, the message
40997 Program exited normally.
41001 (which is ordinarily issued whenever a program running under @value{GDBN} control
41002 terminates) is not issued when running in batch mode.
41004 @item -cd=@var{directory}
41005 Run @value{GDBN} using @var{directory} as its working directory,
41006 instead of the current directory.
41010 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41011 @value{GDBN} to output the full file name and line number in a standard,
41012 recognizable fashion each time a stack frame is displayed (which
41013 includes each time the program stops). This recognizable format looks
41014 like two @samp{\032} characters, followed by the file name, line number
41015 and character position separated by colons, and a newline. The
41016 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41017 characters as a signal to display the source code for the frame.
41020 Set the line speed (baud rate or bits per second) of any serial
41021 interface used by @value{GDBN} for remote debugging.
41023 @item -tty=@var{device}
41024 Run using @var{device} for your program's standard input and output.
41028 @c man begin SEEALSO gdb
41030 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41031 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41032 documentation are properly installed at your site, the command
41039 should give you access to the complete manual.
41041 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41042 Richard M. Stallman and Roland H. Pesch, July 1991.
41046 @node gdbserver man
41047 @heading gdbserver man
41049 @c man title gdbserver Remote Server for the GNU Debugger
41051 @c man begin SYNOPSIS gdbserver
41052 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41054 gdbserver --attach @var{comm} @var{pid}
41056 gdbserver --multi @var{comm}
41060 @c man begin DESCRIPTION gdbserver
41061 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41062 than the one which is running the program being debugged.
41065 @subheading Usage (server (target) side)
41068 Usage (server (target) side):
41071 First, you need to have a copy of the program you want to debug put onto
41072 the target system. The program can be stripped to save space if needed, as
41073 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41074 the @value{GDBN} running on the host system.
41076 To use the server, you log on to the target system, and run the @command{gdbserver}
41077 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41078 your program, and (c) its arguments. The general syntax is:
41081 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41084 For example, using a serial port, you might say:
41088 @c @file would wrap it as F</dev/com1>.
41089 target> gdbserver /dev/com1 emacs foo.txt
41092 target> gdbserver @file{/dev/com1} emacs foo.txt
41096 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41097 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41098 waits patiently for the host @value{GDBN} to communicate with it.
41100 To use a TCP connection, you could say:
41103 target> gdbserver host:2345 emacs foo.txt
41106 This says pretty much the same thing as the last example, except that we are
41107 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
41108 that we are expecting to see a TCP connection from @code{host} to local TCP port
41109 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
41110 want for the port number as long as it does not conflict with any existing TCP
41111 ports on the target system. This same port number must be used in the host
41112 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
41113 you chose a port number that conflicts with another service, @command{gdbserver} will
41114 print an error message and exit.
41116 @command{gdbserver} can also attach to running programs.
41117 This is accomplished via the @option{--attach} argument. The syntax is:
41120 target> gdbserver --attach @var{comm} @var{pid}
41123 @var{pid} is the process ID of a currently running process. It isn't
41124 necessary to point @command{gdbserver} at a binary for the running process.
41126 To start @code{gdbserver} without supplying an initial command to run
41127 or process ID to attach, use the @option{--multi} command line option.
41128 In such case you should connect using @kbd{target extended-remote} to start
41129 the program you want to debug.
41132 target> gdbserver --multi @var{comm}
41136 @subheading Usage (host side)
41142 You need an unstripped copy of the target program on your host system, since
41143 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
41144 would, with the target program as the first argument. (You may need to use the
41145 @option{--baud} option if the serial line is running at anything except 9600 baud.)
41146 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
41147 new command you need to know about is @code{target remote}
41148 (or @code{target extended-remote}). Its argument is either
41149 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
41150 descriptor. For example:
41154 @c @file would wrap it as F</dev/ttyb>.
41155 (gdb) target remote /dev/ttyb
41158 (gdb) target remote @file{/dev/ttyb}
41163 communicates with the server via serial line @file{/dev/ttyb}, and:
41166 (gdb) target remote the-target:2345
41170 communicates via a TCP connection to port 2345 on host `the-target', where
41171 you previously started up @command{gdbserver} with the same port number. Note that for
41172 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
41173 command, otherwise you may get an error that looks something like
41174 `Connection refused'.
41176 @command{gdbserver} can also debug multiple inferiors at once,
41179 the @value{GDBN} manual in node @code{Inferiors and Programs}
41180 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
41183 @ref{Inferiors and Programs}.
41185 In such case use the @code{extended-remote} @value{GDBN} command variant:
41188 (gdb) target extended-remote the-target:2345
41191 The @command{gdbserver} option @option{--multi} may or may not be used in such
41195 @c man begin OPTIONS gdbserver
41196 There are three different modes for invoking @command{gdbserver}:
41201 Debug a specific program specified by its program name:
41204 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41207 The @var{comm} parameter specifies how should the server communicate
41208 with @value{GDBN}; it is either a device name (to use a serial line),
41209 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
41210 stdin/stdout of @code{gdbserver}. Specify the name of the program to
41211 debug in @var{prog}. Any remaining arguments will be passed to the
41212 program verbatim. When the program exits, @value{GDBN} will close the
41213 connection, and @code{gdbserver} will exit.
41216 Debug a specific program by specifying the process ID of a running
41220 gdbserver --attach @var{comm} @var{pid}
41223 The @var{comm} parameter is as described above. Supply the process ID
41224 of a running program in @var{pid}; @value{GDBN} will do everything
41225 else. Like with the previous mode, when the process @var{pid} exits,
41226 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
41229 Multi-process mode -- debug more than one program/process:
41232 gdbserver --multi @var{comm}
41235 In this mode, @value{GDBN} can instruct @command{gdbserver} which
41236 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
41237 close the connection when a process being debugged exits, so you can
41238 debug several processes in the same session.
41241 In each of the modes you may specify these options:
41246 List all options, with brief explanations.
41249 This option causes @command{gdbserver} to print its version number and exit.
41252 @command{gdbserver} will attach to a running program. The syntax is:
41255 target> gdbserver --attach @var{comm} @var{pid}
41258 @var{pid} is the process ID of a currently running process. It isn't
41259 necessary to point @command{gdbserver} at a binary for the running process.
41262 To start @code{gdbserver} without supplying an initial command to run
41263 or process ID to attach, use this command line option.
41264 Then you can connect using @kbd{target extended-remote} and start
41265 the program you want to debug. The syntax is:
41268 target> gdbserver --multi @var{comm}
41272 Instruct @code{gdbserver} to display extra status information about the debugging
41274 This option is intended for @code{gdbserver} development and for bug reports to
41277 @item --remote-debug
41278 Instruct @code{gdbserver} to display remote protocol debug output.
41279 This option is intended for @code{gdbserver} development and for bug reports to
41282 @item --debug-format=option1@r{[},option2,...@r{]}
41283 Instruct @code{gdbserver} to include extra information in each line
41284 of debugging output.
41285 @xref{Other Command-Line Arguments for gdbserver}.
41288 Specify a wrapper to launch programs
41289 for debugging. The option should be followed by the name of the
41290 wrapper, then any command-line arguments to pass to the wrapper, then
41291 @kbd{--} indicating the end of the wrapper arguments.
41294 By default, @command{gdbserver} keeps the listening TCP port open, so that
41295 additional connections are possible. However, if you start @code{gdbserver}
41296 with the @option{--once} option, it will stop listening for any further
41297 connection attempts after connecting to the first @value{GDBN} session.
41299 @c --disable-packet is not documented for users.
41301 @c --disable-randomization and --no-disable-randomization are superseded by
41302 @c QDisableRandomization.
41307 @c man begin SEEALSO gdbserver
41309 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41310 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41311 documentation are properly installed at your site, the command
41317 should give you access to the complete manual.
41319 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41320 Richard M. Stallman and Roland H. Pesch, July 1991.
41327 @c man title gcore Generate a core file of a running program
41330 @c man begin SYNOPSIS gcore
41331 gcore [-o @var{filename}] @var{pid}
41335 @c man begin DESCRIPTION gcore
41336 Generate a core dump of a running program with process ID @var{pid}.
41337 Produced file is equivalent to a kernel produced core file as if the process
41338 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
41339 limit). Unlike after a crash, after @command{gcore} the program remains
41340 running without any change.
41343 @c man begin OPTIONS gcore
41345 @item -o @var{filename}
41346 The optional argument
41347 @var{filename} specifies the file name where to put the core dump.
41348 If not specified, the file name defaults to @file{core.@var{pid}},
41349 where @var{pid} is the running program process ID.
41353 @c man begin SEEALSO gcore
41355 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41356 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41357 documentation are properly installed at your site, the command
41364 should give you access to the complete manual.
41366 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41367 Richard M. Stallman and Roland H. Pesch, July 1991.
41374 @c man title gdbinit GDB initialization scripts
41377 @c man begin SYNOPSIS gdbinit
41378 @ifset SYSTEM_GDBINIT
41379 @value{SYSTEM_GDBINIT}
41388 @c man begin DESCRIPTION gdbinit
41389 These files contain @value{GDBN} commands to automatically execute during
41390 @value{GDBN} startup. The lines of contents are canned sequences of commands,
41393 the @value{GDBN} manual in node @code{Sequences}
41394 -- shell command @code{info -f gdb -n Sequences}.
41400 Please read more in
41402 the @value{GDBN} manual in node @code{Startup}
41403 -- shell command @code{info -f gdb -n Startup}.
41410 @ifset SYSTEM_GDBINIT
41411 @item @value{SYSTEM_GDBINIT}
41413 @ifclear SYSTEM_GDBINIT
41414 @item (not enabled with @code{--with-system-gdbinit} during compilation)
41416 System-wide initialization file. It is executed unless user specified
41417 @value{GDBN} option @code{-nx} or @code{-n}.
41420 the @value{GDBN} manual in node @code{System-wide configuration}
41421 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
41424 @ref{System-wide configuration}.
41428 User initialization file. It is executed unless user specified
41429 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
41432 Initialization file for current directory. It may need to be enabled with
41433 @value{GDBN} security command @code{set auto-load local-gdbinit}.
41436 the @value{GDBN} manual in node @code{Init File in the Current Directory}
41437 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
41440 @ref{Init File in the Current Directory}.
41445 @c man begin SEEALSO gdbinit
41447 gdb(1), @code{info -f gdb -n Startup}
41449 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41450 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41451 documentation are properly installed at your site, the command
41457 should give you access to the complete manual.
41459 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41460 Richard M. Stallman and Roland H. Pesch, July 1991.
41466 @node GNU Free Documentation License
41467 @appendix GNU Free Documentation License
41470 @node Concept Index
41471 @unnumbered Concept Index
41475 @node Command and Variable Index
41476 @unnumbered Command, Variable, and Function Index
41481 % I think something like @@colophon should be in texinfo. In the
41483 \long\def\colophon{\hbox to0pt{}\vfill
41484 \centerline{The body of this manual is set in}
41485 \centerline{\fontname\tenrm,}
41486 \centerline{with headings in {\bf\fontname\tenbf}}
41487 \centerline{and examples in {\tt\fontname\tentt}.}
41488 \centerline{{\it\fontname\tenit\/},}
41489 \centerline{{\bf\fontname\tenbf}, and}
41490 \centerline{{\sl\fontname\tensl\/}}
41491 \centerline{are used for emphasis.}\vfill}
41493 % Blame: doc@@cygnus.com, 1991.