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
2796 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 GNU/Linux 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.
2847 @cindex focus of debugging
2848 @cindex current thread
2849 The @value{GDBN} thread debugging facility allows you to observe all
2850 threads while your program runs---but whenever @value{GDBN} takes
2851 control, one thread in particular is always the focus of debugging.
2852 This thread is called the @dfn{current thread}. Debugging commands show
2853 program information from the perspective of the current thread.
2855 @cindex @code{New} @var{systag} message
2856 @cindex thread identifier (system)
2857 @c FIXME-implementors!! It would be more helpful if the [New...] message
2858 @c included GDB's numeric thread handle, so you could just go to that
2859 @c thread without first checking `info threads'.
2860 Whenever @value{GDBN} detects a new thread in your program, it displays
2861 the target system's identification for the thread with a message in the
2862 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2863 whose form varies depending on the particular system. For example, on
2864 @sc{gnu}/Linux, you might see
2867 [New Thread 0x41e02940 (LWP 25582)]
2871 when @value{GDBN} notices a new thread. In contrast, on other systems,
2872 the @var{systag} is simply something like @samp{process 368}, with no
2875 @c FIXME!! (1) Does the [New...] message appear even for the very first
2876 @c thread of a program, or does it only appear for the
2877 @c second---i.e.@: when it becomes obvious we have a multithread
2879 @c (2) *Is* there necessarily a first thread always? Or do some
2880 @c multithread systems permit starting a program with multiple
2881 @c threads ab initio?
2883 @cindex thread number
2884 @cindex thread identifier (GDB)
2885 For debugging purposes, @value{GDBN} associates its own thread
2886 number---always a single integer---with each thread in your program.
2888 From @value{GDBN}'s perspective, a process always has at least one
2889 thread. In other words, @value{GDBN} assigns a thread number to the
2890 program's ``main thread'' even if the program is not multi-threaded.
2893 @kindex info threads
2894 @item info threads @r{[}@var{id}@dots{}@r{]}
2895 Display a summary of all threads currently in your program. Optional
2896 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2897 means to print information only about the specified thread or threads.
2898 @value{GDBN} displays for each thread (in this order):
2902 the thread number assigned by @value{GDBN}
2905 the target system's thread identifier (@var{systag})
2908 the thread's name, if one is known. A thread can either be named by
2909 the user (see @code{thread name}, below), or, in some cases, by the
2913 the current stack frame summary for that thread
2917 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2918 indicates the current thread.
2922 @c end table here to get a little more width for example
2925 (@value{GDBP}) info threads
2927 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2928 2 process 35 thread 23 0x34e5 in sigpause ()
2929 3 process 35 thread 27 0x34e5 in sigpause ()
2933 On Solaris, you can display more information about user threads with a
2934 Solaris-specific command:
2937 @item maint info sol-threads
2938 @kindex maint info sol-threads
2939 @cindex thread info (Solaris)
2940 Display info on Solaris user threads.
2944 @kindex thread @var{threadno}
2945 @item thread @var{threadno}
2946 Make thread number @var{threadno} the current thread. The command
2947 argument @var{threadno} is the internal @value{GDBN} thread number, as
2948 shown in the first field of the @samp{info threads} display.
2949 @value{GDBN} responds by displaying the system identifier of the thread
2950 you selected, and its current stack frame summary:
2953 (@value{GDBP}) thread 2
2954 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2955 #0 some_function (ignore=0x0) at example.c:8
2956 8 printf ("hello\n");
2960 As with the @samp{[New @dots{}]} message, the form of the text after
2961 @samp{Switching to} depends on your system's conventions for identifying
2964 @vindex $_thread@r{, convenience variable}
2965 The debugger convenience variable @samp{$_thread} contains the number
2966 of the current thread. You may find this useful in writing breakpoint
2967 conditional expressions, command scripts, and so forth. See
2968 @xref{Convenience Vars,, Convenience Variables}, for general
2969 information on convenience variables.
2971 @kindex thread apply
2972 @cindex apply command to several threads
2973 @item thread apply [@var{threadno} | all [-ascending]] @var{command}
2974 The @code{thread apply} command allows you to apply the named
2975 @var{command} to one or more threads. Specify the numbers of the
2976 threads that you want affected with the command argument
2977 @var{threadno}. It can be a single thread number, one of the numbers
2978 shown in the first field of the @samp{info threads} display; or it
2979 could be a range of thread numbers, as in @code{2-4}. To apply
2980 a command to all threads in descending order, type @kbd{thread apply all
2981 @var{command}}. To apply a command to all threads in ascending order,
2982 type @kbd{thread apply all -ascending @var{command}}.
2986 @cindex name a thread
2987 @item thread name [@var{name}]
2988 This command assigns a name to the current thread. If no argument is
2989 given, any existing user-specified name is removed. The thread name
2990 appears in the @samp{info threads} display.
2992 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2993 determine the name of the thread as given by the OS. On these
2994 systems, a name specified with @samp{thread name} will override the
2995 system-give name, and removing the user-specified name will cause
2996 @value{GDBN} to once again display the system-specified name.
2999 @cindex search for a thread
3000 @item thread find [@var{regexp}]
3001 Search for and display thread ids whose name or @var{systag}
3002 matches the supplied regular expression.
3004 As well as being the complement to the @samp{thread name} command,
3005 this command also allows you to identify a thread by its target
3006 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3010 (@value{GDBN}) thread find 26688
3011 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3012 (@value{GDBN}) info thread 4
3014 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3017 @kindex set print thread-events
3018 @cindex print messages on thread start and exit
3019 @item set print thread-events
3020 @itemx set print thread-events on
3021 @itemx set print thread-events off
3022 The @code{set print thread-events} command allows you to enable or
3023 disable printing of messages when @value{GDBN} notices that new threads have
3024 started or that threads have exited. By default, these messages will
3025 be printed if detection of these events is supported by the target.
3026 Note that these messages cannot be disabled on all targets.
3028 @kindex show print thread-events
3029 @item show print thread-events
3030 Show whether messages will be printed when @value{GDBN} detects that threads
3031 have started and exited.
3034 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3035 more information about how @value{GDBN} behaves when you stop and start
3036 programs with multiple threads.
3038 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3039 watchpoints in programs with multiple threads.
3041 @anchor{set libthread-db-search-path}
3043 @kindex set libthread-db-search-path
3044 @cindex search path for @code{libthread_db}
3045 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3046 If this variable is set, @var{path} is a colon-separated list of
3047 directories @value{GDBN} will use to search for @code{libthread_db}.
3048 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3049 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3050 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3053 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3054 @code{libthread_db} library to obtain information about threads in the
3055 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3056 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3057 specific thread debugging library loading is enabled
3058 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3060 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3061 refers to the default system directories that are
3062 normally searched for loading shared libraries. The @samp{$sdir} entry
3063 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3064 (@pxref{libthread_db.so.1 file}).
3066 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3067 refers to the directory from which @code{libpthread}
3068 was loaded in the inferior process.
3070 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3071 @value{GDBN} attempts to initialize it with the current inferior process.
3072 If this initialization fails (which could happen because of a version
3073 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3074 will unload @code{libthread_db}, and continue with the next directory.
3075 If none of @code{libthread_db} libraries initialize successfully,
3076 @value{GDBN} will issue a warning and thread debugging will be disabled.
3078 Setting @code{libthread-db-search-path} is currently implemented
3079 only on some platforms.
3081 @kindex show libthread-db-search-path
3082 @item show libthread-db-search-path
3083 Display current libthread_db search path.
3085 @kindex set debug libthread-db
3086 @kindex show debug libthread-db
3087 @cindex debugging @code{libthread_db}
3088 @item set debug libthread-db
3089 @itemx show debug libthread-db
3090 Turns on or off display of @code{libthread_db}-related events.
3091 Use @code{1} to enable, @code{0} to disable.
3095 @section Debugging Forks
3097 @cindex fork, debugging programs which call
3098 @cindex multiple processes
3099 @cindex processes, multiple
3100 On most systems, @value{GDBN} has no special support for debugging
3101 programs which create additional processes using the @code{fork}
3102 function. When a program forks, @value{GDBN} will continue to debug the
3103 parent process and the child process will run unimpeded. If you have
3104 set a breakpoint in any code which the child then executes, the child
3105 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3106 will cause it to terminate.
3108 However, if you want to debug the child process there is a workaround
3109 which isn't too painful. Put a call to @code{sleep} in the code which
3110 the child process executes after the fork. It may be useful to sleep
3111 only if a certain environment variable is set, or a certain file exists,
3112 so that the delay need not occur when you don't want to run @value{GDBN}
3113 on the child. While the child is sleeping, use the @code{ps} program to
3114 get its process ID. Then tell @value{GDBN} (a new invocation of
3115 @value{GDBN} if you are also debugging the parent process) to attach to
3116 the child process (@pxref{Attach}). From that point on you can debug
3117 the child process just like any other process which you attached to.
3119 On some systems, @value{GDBN} provides support for debugging programs
3120 that create additional processes using the @code{fork} or @code{vfork}
3121 functions. On @sc{gnu}/Linux platforms, this feature is supported
3122 with kernel version 2.5.60 and later.
3124 The fork debugging commands are supported in both native mode and when
3125 connected to @code{gdbserver} using @kbd{target extended-remote}.
3127 By default, when a program forks, @value{GDBN} will continue to debug
3128 the parent process and the child process will run unimpeded.
3130 If you want to follow the child process instead of the parent process,
3131 use the command @w{@code{set follow-fork-mode}}.
3134 @kindex set follow-fork-mode
3135 @item set follow-fork-mode @var{mode}
3136 Set the debugger response to a program call of @code{fork} or
3137 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3138 process. The @var{mode} argument can be:
3142 The original process is debugged after a fork. The child process runs
3143 unimpeded. This is the default.
3146 The new process is debugged after a fork. The parent process runs
3151 @kindex show follow-fork-mode
3152 @item show follow-fork-mode
3153 Display the current debugger response to a @code{fork} or @code{vfork} call.
3156 @cindex debugging multiple processes
3157 On Linux, if you want to debug both the parent and child processes, use the
3158 command @w{@code{set detach-on-fork}}.
3161 @kindex set detach-on-fork
3162 @item set detach-on-fork @var{mode}
3163 Tells gdb whether to detach one of the processes after a fork, or
3164 retain debugger control over them both.
3168 The child process (or parent process, depending on the value of
3169 @code{follow-fork-mode}) will be detached and allowed to run
3170 independently. This is the default.
3173 Both processes will be held under the control of @value{GDBN}.
3174 One process (child or parent, depending on the value of
3175 @code{follow-fork-mode}) is debugged as usual, while the other
3180 @kindex show detach-on-fork
3181 @item show detach-on-fork
3182 Show whether detach-on-fork mode is on/off.
3185 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3186 will retain control of all forked processes (including nested forks).
3187 You can list the forked processes under the control of @value{GDBN} by
3188 using the @w{@code{info inferiors}} command, and switch from one fork
3189 to another by using the @code{inferior} command (@pxref{Inferiors and
3190 Programs, ,Debugging Multiple Inferiors and Programs}).
3192 To quit debugging one of the forked processes, you can either detach
3193 from it by using the @w{@code{detach inferiors}} command (allowing it
3194 to run independently), or kill it using the @w{@code{kill inferiors}}
3195 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3198 If you ask to debug a child process and a @code{vfork} is followed by an
3199 @code{exec}, @value{GDBN} executes the new target up to the first
3200 breakpoint in the new target. If you have a breakpoint set on
3201 @code{main} in your original program, the breakpoint will also be set on
3202 the child process's @code{main}.
3204 On some systems, when a child process is spawned by @code{vfork}, you
3205 cannot debug the child or parent until an @code{exec} call completes.
3207 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3208 call executes, the new target restarts. To restart the parent
3209 process, use the @code{file} command with the parent executable name
3210 as its argument. By default, after an @code{exec} call executes,
3211 @value{GDBN} discards the symbols of the previous executable image.
3212 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3216 @kindex set follow-exec-mode
3217 @item set follow-exec-mode @var{mode}
3219 Set debugger response to a program call of @code{exec}. An
3220 @code{exec} call replaces the program image of a process.
3222 @code{follow-exec-mode} can be:
3226 @value{GDBN} creates a new inferior and rebinds the process to this
3227 new inferior. The program the process was running before the
3228 @code{exec} call can be restarted afterwards by restarting the
3234 (@value{GDBP}) info inferiors
3236 Id Description Executable
3239 process 12020 is executing new program: prog2
3240 Program exited normally.
3241 (@value{GDBP}) info inferiors
3242 Id Description Executable
3248 @value{GDBN} keeps the process bound to the same inferior. The new
3249 executable image replaces the previous executable loaded in the
3250 inferior. Restarting the inferior after the @code{exec} call, with
3251 e.g., the @code{run} command, restarts the executable the process was
3252 running after the @code{exec} call. This is the default mode.
3257 (@value{GDBP}) info inferiors
3258 Id Description Executable
3261 process 12020 is executing new program: prog2
3262 Program exited normally.
3263 (@value{GDBP}) info inferiors
3264 Id Description Executable
3271 You can use the @code{catch} command to make @value{GDBN} stop whenever
3272 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3273 Catchpoints, ,Setting Catchpoints}.
3275 @node Checkpoint/Restart
3276 @section Setting a @emph{Bookmark} to Return to Later
3281 @cindex snapshot of a process
3282 @cindex rewind program state
3284 On certain operating systems@footnote{Currently, only
3285 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3286 program's state, called a @dfn{checkpoint}, and come back to it
3289 Returning to a checkpoint effectively undoes everything that has
3290 happened in the program since the @code{checkpoint} was saved. This
3291 includes changes in memory, registers, and even (within some limits)
3292 system state. Effectively, it is like going back in time to the
3293 moment when the checkpoint was saved.
3295 Thus, if you're stepping thru a program and you think you're
3296 getting close to the point where things go wrong, you can save
3297 a checkpoint. Then, if you accidentally go too far and miss
3298 the critical statement, instead of having to restart your program
3299 from the beginning, you can just go back to the checkpoint and
3300 start again from there.
3302 This can be especially useful if it takes a lot of time or
3303 steps to reach the point where you think the bug occurs.
3305 To use the @code{checkpoint}/@code{restart} method of debugging:
3310 Save a snapshot of the debugged program's current execution state.
3311 The @code{checkpoint} command takes no arguments, but each checkpoint
3312 is assigned a small integer id, similar to a breakpoint id.
3314 @kindex info checkpoints
3315 @item info checkpoints
3316 List the checkpoints that have been saved in the current debugging
3317 session. For each checkpoint, the following information will be
3324 @item Source line, or label
3327 @kindex restart @var{checkpoint-id}
3328 @item restart @var{checkpoint-id}
3329 Restore the program state that was saved as checkpoint number
3330 @var{checkpoint-id}. All program variables, registers, stack frames
3331 etc.@: will be returned to the values that they had when the checkpoint
3332 was saved. In essence, gdb will ``wind back the clock'' to the point
3333 in time when the checkpoint was saved.
3335 Note that breakpoints, @value{GDBN} variables, command history etc.
3336 are not affected by restoring a checkpoint. In general, a checkpoint
3337 only restores things that reside in the program being debugged, not in
3340 @kindex delete checkpoint @var{checkpoint-id}
3341 @item delete checkpoint @var{checkpoint-id}
3342 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3346 Returning to a previously saved checkpoint will restore the user state
3347 of the program being debugged, plus a significant subset of the system
3348 (OS) state, including file pointers. It won't ``un-write'' data from
3349 a file, but it will rewind the file pointer to the previous location,
3350 so that the previously written data can be overwritten. For files
3351 opened in read mode, the pointer will also be restored so that the
3352 previously read data can be read again.
3354 Of course, characters that have been sent to a printer (or other
3355 external device) cannot be ``snatched back'', and characters received
3356 from eg.@: a serial device can be removed from internal program buffers,
3357 but they cannot be ``pushed back'' into the serial pipeline, ready to
3358 be received again. Similarly, the actual contents of files that have
3359 been changed cannot be restored (at this time).
3361 However, within those constraints, you actually can ``rewind'' your
3362 program to a previously saved point in time, and begin debugging it
3363 again --- and you can change the course of events so as to debug a
3364 different execution path this time.
3366 @cindex checkpoints and process id
3367 Finally, there is one bit of internal program state that will be
3368 different when you return to a checkpoint --- the program's process
3369 id. Each checkpoint will have a unique process id (or @var{pid}),
3370 and each will be different from the program's original @var{pid}.
3371 If your program has saved a local copy of its process id, this could
3372 potentially pose a problem.
3374 @subsection A Non-obvious Benefit of Using Checkpoints
3376 On some systems such as @sc{gnu}/Linux, address space randomization
3377 is performed on new processes for security reasons. This makes it
3378 difficult or impossible to set a breakpoint, or watchpoint, on an
3379 absolute address if you have to restart the program, since the
3380 absolute location of a symbol will change from one execution to the
3383 A checkpoint, however, is an @emph{identical} copy of a process.
3384 Therefore if you create a checkpoint at (eg.@:) the start of main,
3385 and simply return to that checkpoint instead of restarting the
3386 process, you can avoid the effects of address randomization and
3387 your symbols will all stay in the same place.
3390 @chapter Stopping and Continuing
3392 The principal purposes of using a debugger are so that you can stop your
3393 program before it terminates; or so that, if your program runs into
3394 trouble, you can investigate and find out why.
3396 Inside @value{GDBN}, your program may stop for any of several reasons,
3397 such as a signal, a breakpoint, or reaching a new line after a
3398 @value{GDBN} command such as @code{step}. You may then examine and
3399 change variables, set new breakpoints or remove old ones, and then
3400 continue execution. Usually, the messages shown by @value{GDBN} provide
3401 ample explanation of the status of your program---but you can also
3402 explicitly request this information at any time.
3405 @kindex info program
3407 Display information about the status of your program: whether it is
3408 running or not, what process it is, and why it stopped.
3412 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3413 * Continuing and Stepping:: Resuming execution
3414 * Skipping Over Functions and Files::
3415 Skipping over functions and files
3417 * Thread Stops:: Stopping and starting multi-thread programs
3421 @section Breakpoints, Watchpoints, and Catchpoints
3424 A @dfn{breakpoint} makes your program stop whenever a certain point in
3425 the program is reached. For each breakpoint, you can add conditions to
3426 control in finer detail whether your program stops. You can set
3427 breakpoints with the @code{break} command and its variants (@pxref{Set
3428 Breaks, ,Setting Breakpoints}), to specify the place where your program
3429 should stop by line number, function name or exact address in the
3432 On some systems, you can set breakpoints in shared libraries before
3433 the executable is run.
3436 @cindex data breakpoints
3437 @cindex memory tracing
3438 @cindex breakpoint on memory address
3439 @cindex breakpoint on variable modification
3440 A @dfn{watchpoint} is a special breakpoint that stops your program
3441 when the value of an expression changes. The expression may be a value
3442 of a variable, or it could involve values of one or more variables
3443 combined by operators, such as @samp{a + b}. This is sometimes called
3444 @dfn{data breakpoints}. You must use a different command to set
3445 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3446 from that, you can manage a watchpoint like any other breakpoint: you
3447 enable, disable, and delete both breakpoints and watchpoints using the
3450 You can arrange to have values from your program displayed automatically
3451 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3455 @cindex breakpoint on events
3456 A @dfn{catchpoint} is another special breakpoint that stops your program
3457 when a certain kind of event occurs, such as the throwing of a C@t{++}
3458 exception or the loading of a library. As with watchpoints, you use a
3459 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3460 Catchpoints}), but aside from that, you can manage a catchpoint like any
3461 other breakpoint. (To stop when your program receives a signal, use the
3462 @code{handle} command; see @ref{Signals, ,Signals}.)
3464 @cindex breakpoint numbers
3465 @cindex numbers for breakpoints
3466 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3467 catchpoint when you create it; these numbers are successive integers
3468 starting with one. In many of the commands for controlling various
3469 features of breakpoints you use the breakpoint number to say which
3470 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3471 @dfn{disabled}; if disabled, it has no effect on your program until you
3474 @cindex breakpoint ranges
3475 @cindex ranges of breakpoints
3476 Some @value{GDBN} commands accept a range of breakpoints on which to
3477 operate. A breakpoint range is either a single breakpoint number, like
3478 @samp{5}, or two such numbers, in increasing order, separated by a
3479 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3480 all breakpoints in that range are operated on.
3483 * Set Breaks:: Setting breakpoints
3484 * Set Watchpoints:: Setting watchpoints
3485 * Set Catchpoints:: Setting catchpoints
3486 * Delete Breaks:: Deleting breakpoints
3487 * Disabling:: Disabling breakpoints
3488 * Conditions:: Break conditions
3489 * Break Commands:: Breakpoint command lists
3490 * Dynamic Printf:: Dynamic printf
3491 * Save Breakpoints:: How to save breakpoints in a file
3492 * Static Probe Points:: Listing static probe points
3493 * Error in Breakpoints:: ``Cannot insert breakpoints''
3494 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3498 @subsection Setting Breakpoints
3500 @c FIXME LMB what does GDB do if no code on line of breakpt?
3501 @c consider in particular declaration with/without initialization.
3503 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3506 @kindex b @r{(@code{break})}
3507 @vindex $bpnum@r{, convenience variable}
3508 @cindex latest breakpoint
3509 Breakpoints are set with the @code{break} command (abbreviated
3510 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3511 number of the breakpoint you've set most recently; see @ref{Convenience
3512 Vars,, Convenience Variables}, for a discussion of what you can do with
3513 convenience variables.
3516 @item break @var{location}
3517 Set a breakpoint at the given @var{location}, which can specify a
3518 function name, a line number, or an address of an instruction.
3519 (@xref{Specify Location}, for a list of all the possible ways to
3520 specify a @var{location}.) The breakpoint will stop your program just
3521 before it executes any of the code in the specified @var{location}.
3523 When using source languages that permit overloading of symbols, such as
3524 C@t{++}, a function name may refer to more than one possible place to break.
3525 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3528 It is also possible to insert a breakpoint that will stop the program
3529 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3530 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3533 When called without any arguments, @code{break} sets a breakpoint at
3534 the next instruction to be executed in the selected stack frame
3535 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3536 innermost, this makes your program stop as soon as control
3537 returns to that frame. This is similar to the effect of a
3538 @code{finish} command in the frame inside the selected frame---except
3539 that @code{finish} does not leave an active breakpoint. If you use
3540 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3541 the next time it reaches the current location; this may be useful
3544 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3545 least one instruction has been executed. If it did not do this, you
3546 would be unable to proceed past a breakpoint without first disabling the
3547 breakpoint. This rule applies whether or not the breakpoint already
3548 existed when your program stopped.
3550 @item break @dots{} if @var{cond}
3551 Set a breakpoint with condition @var{cond}; evaluate the expression
3552 @var{cond} each time the breakpoint is reached, and stop only if the
3553 value is nonzero---that is, if @var{cond} evaluates as true.
3554 @samp{@dots{}} stands for one of the possible arguments described
3555 above (or no argument) specifying where to break. @xref{Conditions,
3556 ,Break Conditions}, for more information on breakpoint conditions.
3559 @item tbreak @var{args}
3560 Set a breakpoint enabled only for one stop. The @var{args} are the
3561 same as for the @code{break} command, and the breakpoint is set in the same
3562 way, but the breakpoint is automatically deleted after the first time your
3563 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3566 @cindex hardware breakpoints
3567 @item hbreak @var{args}
3568 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3569 @code{break} command and the breakpoint is set in the same way, but the
3570 breakpoint requires hardware support and some target hardware may not
3571 have this support. The main purpose of this is EPROM/ROM code
3572 debugging, so you can set a breakpoint at an instruction without
3573 changing the instruction. This can be used with the new trap-generation
3574 provided by SPARClite DSU and most x86-based targets. These targets
3575 will generate traps when a program accesses some data or instruction
3576 address that is assigned to the debug registers. However the hardware
3577 breakpoint registers can take a limited number of breakpoints. For
3578 example, on the DSU, only two data breakpoints can be set at a time, and
3579 @value{GDBN} will reject this command if more than two are used. Delete
3580 or disable unused hardware breakpoints before setting new ones
3581 (@pxref{Disabling, ,Disabling Breakpoints}).
3582 @xref{Conditions, ,Break Conditions}.
3583 For remote targets, you can restrict the number of hardware
3584 breakpoints @value{GDBN} will use, see @ref{set remote
3585 hardware-breakpoint-limit}.
3588 @item thbreak @var{args}
3589 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3590 are the same as for the @code{hbreak} command and the breakpoint is set in
3591 the same way. However, like the @code{tbreak} command,
3592 the breakpoint is automatically deleted after the
3593 first time your program stops there. Also, like the @code{hbreak}
3594 command, the breakpoint requires hardware support and some target hardware
3595 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3596 See also @ref{Conditions, ,Break Conditions}.
3599 @cindex regular expression
3600 @cindex breakpoints at functions matching a regexp
3601 @cindex set breakpoints in many functions
3602 @item rbreak @var{regex}
3603 Set breakpoints on all functions matching the regular expression
3604 @var{regex}. This command sets an unconditional breakpoint on all
3605 matches, printing a list of all breakpoints it set. Once these
3606 breakpoints are set, they are treated just like the breakpoints set with
3607 the @code{break} command. You can delete them, disable them, or make
3608 them conditional the same way as any other breakpoint.
3610 The syntax of the regular expression is the standard one used with tools
3611 like @file{grep}. Note that this is different from the syntax used by
3612 shells, so for instance @code{foo*} matches all functions that include
3613 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3614 @code{.*} leading and trailing the regular expression you supply, so to
3615 match only functions that begin with @code{foo}, use @code{^foo}.
3617 @cindex non-member C@t{++} functions, set breakpoint in
3618 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3619 breakpoints on overloaded functions that are not members of any special
3622 @cindex set breakpoints on all functions
3623 The @code{rbreak} command can be used to set breakpoints in
3624 @strong{all} the functions in a program, like this:
3627 (@value{GDBP}) rbreak .
3630 @item rbreak @var{file}:@var{regex}
3631 If @code{rbreak} is called with a filename qualification, it limits
3632 the search for functions matching the given regular expression to the
3633 specified @var{file}. This can be used, for example, to set breakpoints on
3634 every function in a given file:
3637 (@value{GDBP}) rbreak file.c:.
3640 The colon separating the filename qualifier from the regex may
3641 optionally be surrounded by spaces.
3643 @kindex info breakpoints
3644 @cindex @code{$_} and @code{info breakpoints}
3645 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3646 @itemx info break @r{[}@var{n}@dots{}@r{]}
3647 Print a table of all breakpoints, watchpoints, and catchpoints set and
3648 not deleted. Optional argument @var{n} means print information only
3649 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3650 For each breakpoint, following columns are printed:
3653 @item Breakpoint Numbers
3655 Breakpoint, watchpoint, or catchpoint.
3657 Whether the breakpoint is marked to be disabled or deleted when hit.
3658 @item Enabled or Disabled
3659 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3660 that are not enabled.
3662 Where the breakpoint is in your program, as a memory address. For a
3663 pending breakpoint whose address is not yet known, this field will
3664 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3665 library that has the symbol or line referred by breakpoint is loaded.
3666 See below for details. A breakpoint with several locations will
3667 have @samp{<MULTIPLE>} in this field---see below for details.
3669 Where the breakpoint is in the source for your program, as a file and
3670 line number. For a pending breakpoint, the original string passed to
3671 the breakpoint command will be listed as it cannot be resolved until
3672 the appropriate shared library is loaded in the future.
3676 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3677 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3678 @value{GDBN} on the host's side. If it is ``target'', then the condition
3679 is evaluated by the target. The @code{info break} command shows
3680 the condition on the line following the affected breakpoint, together with
3681 its condition evaluation mode in between parentheses.
3683 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3684 allowed to have a condition specified for it. The condition is not parsed for
3685 validity until a shared library is loaded that allows the pending
3686 breakpoint to resolve to a valid location.
3689 @code{info break} with a breakpoint
3690 number @var{n} as argument lists only that breakpoint. The
3691 convenience variable @code{$_} and the default examining-address for
3692 the @code{x} command are set to the address of the last breakpoint
3693 listed (@pxref{Memory, ,Examining Memory}).
3696 @code{info break} displays a count of the number of times the breakpoint
3697 has been hit. This is especially useful in conjunction with the
3698 @code{ignore} command. You can ignore a large number of breakpoint
3699 hits, look at the breakpoint info to see how many times the breakpoint
3700 was hit, and then run again, ignoring one less than that number. This
3701 will get you quickly to the last hit of that breakpoint.
3704 For a breakpoints with an enable count (xref) greater than 1,
3705 @code{info break} also displays that count.
3709 @value{GDBN} allows you to set any number of breakpoints at the same place in
3710 your program. There is nothing silly or meaningless about this. When
3711 the breakpoints are conditional, this is even useful
3712 (@pxref{Conditions, ,Break Conditions}).
3714 @cindex multiple locations, breakpoints
3715 @cindex breakpoints, multiple locations
3716 It is possible that a breakpoint corresponds to several locations
3717 in your program. Examples of this situation are:
3721 Multiple functions in the program may have the same name.
3724 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3725 instances of the function body, used in different cases.
3728 For a C@t{++} template function, a given line in the function can
3729 correspond to any number of instantiations.
3732 For an inlined function, a given source line can correspond to
3733 several places where that function is inlined.
3736 In all those cases, @value{GDBN} will insert a breakpoint at all
3737 the relevant locations.
3739 A breakpoint with multiple locations is displayed in the breakpoint
3740 table using several rows---one header row, followed by one row for
3741 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3742 address column. The rows for individual locations contain the actual
3743 addresses for locations, and show the functions to which those
3744 locations belong. The number column for a location is of the form
3745 @var{breakpoint-number}.@var{location-number}.
3750 Num Type Disp Enb Address What
3751 1 breakpoint keep y <MULTIPLE>
3753 breakpoint already hit 1 time
3754 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3755 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3758 Each location can be individually enabled or disabled by passing
3759 @var{breakpoint-number}.@var{location-number} as argument to the
3760 @code{enable} and @code{disable} commands. Note that you cannot
3761 delete the individual locations from the list, you can only delete the
3762 entire list of locations that belong to their parent breakpoint (with
3763 the @kbd{delete @var{num}} command, where @var{num} is the number of
3764 the parent breakpoint, 1 in the above example). Disabling or enabling
3765 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3766 that belong to that breakpoint.
3768 @cindex pending breakpoints
3769 It's quite common to have a breakpoint inside a shared library.
3770 Shared libraries can be loaded and unloaded explicitly,
3771 and possibly repeatedly, as the program is executed. To support
3772 this use case, @value{GDBN} updates breakpoint locations whenever
3773 any shared library is loaded or unloaded. Typically, you would
3774 set a breakpoint in a shared library at the beginning of your
3775 debugging session, when the library is not loaded, and when the
3776 symbols from the library are not available. When you try to set
3777 breakpoint, @value{GDBN} will ask you if you want to set
3778 a so called @dfn{pending breakpoint}---breakpoint whose address
3779 is not yet resolved.
3781 After the program is run, whenever a new shared library is loaded,
3782 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3783 shared library contains the symbol or line referred to by some
3784 pending breakpoint, that breakpoint is resolved and becomes an
3785 ordinary breakpoint. When a library is unloaded, all breakpoints
3786 that refer to its symbols or source lines become pending again.
3788 This logic works for breakpoints with multiple locations, too. For
3789 example, if you have a breakpoint in a C@t{++} template function, and
3790 a newly loaded shared library has an instantiation of that template,
3791 a new location is added to the list of locations for the breakpoint.
3793 Except for having unresolved address, pending breakpoints do not
3794 differ from regular breakpoints. You can set conditions or commands,
3795 enable and disable them and perform other breakpoint operations.
3797 @value{GDBN} provides some additional commands for controlling what
3798 happens when the @samp{break} command cannot resolve breakpoint
3799 address specification to an address:
3801 @kindex set breakpoint pending
3802 @kindex show breakpoint pending
3804 @item set breakpoint pending auto
3805 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3806 location, it queries you whether a pending breakpoint should be created.
3808 @item set breakpoint pending on
3809 This indicates that an unrecognized breakpoint location should automatically
3810 result in a pending breakpoint being created.
3812 @item set breakpoint pending off
3813 This indicates that pending breakpoints are not to be created. Any
3814 unrecognized breakpoint location results in an error. This setting does
3815 not affect any pending breakpoints previously created.
3817 @item show breakpoint pending
3818 Show the current behavior setting for creating pending breakpoints.
3821 The settings above only affect the @code{break} command and its
3822 variants. Once breakpoint is set, it will be automatically updated
3823 as shared libraries are loaded and unloaded.
3825 @cindex automatic hardware breakpoints
3826 For some targets, @value{GDBN} can automatically decide if hardware or
3827 software breakpoints should be used, depending on whether the
3828 breakpoint address is read-only or read-write. This applies to
3829 breakpoints set with the @code{break} command as well as to internal
3830 breakpoints set by commands like @code{next} and @code{finish}. For
3831 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3834 You can control this automatic behaviour with the following commands::
3836 @kindex set breakpoint auto-hw
3837 @kindex show breakpoint auto-hw
3839 @item set breakpoint auto-hw on
3840 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3841 will try to use the target memory map to decide if software or hardware
3842 breakpoint must be used.
3844 @item set breakpoint auto-hw off
3845 This indicates @value{GDBN} should not automatically select breakpoint
3846 type. If the target provides a memory map, @value{GDBN} will warn when
3847 trying to set software breakpoint at a read-only address.
3850 @value{GDBN} normally implements breakpoints by replacing the program code
3851 at the breakpoint address with a special instruction, which, when
3852 executed, given control to the debugger. By default, the program
3853 code is so modified only when the program is resumed. As soon as
3854 the program stops, @value{GDBN} restores the original instructions. This
3855 behaviour guards against leaving breakpoints inserted in the
3856 target should gdb abrubptly disconnect. However, with slow remote
3857 targets, inserting and removing breakpoint can reduce the performance.
3858 This behavior can be controlled with the following commands::
3860 @kindex set breakpoint always-inserted
3861 @kindex show breakpoint always-inserted
3863 @item set breakpoint always-inserted off
3864 All breakpoints, including newly added by the user, are inserted in
3865 the target only when the target is resumed. All breakpoints are
3866 removed from the target when it stops. This is the default mode.
3868 @item set breakpoint always-inserted on
3869 Causes all breakpoints to be inserted in the target at all times. If
3870 the user adds a new breakpoint, or changes an existing breakpoint, the
3871 breakpoints in the target are updated immediately. A breakpoint is
3872 removed from the target only when breakpoint itself is deleted.
3875 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3876 when a breakpoint breaks. If the condition is true, then the process being
3877 debugged stops, otherwise the process is resumed.
3879 If the target supports evaluating conditions on its end, @value{GDBN} may
3880 download the breakpoint, together with its conditions, to it.
3882 This feature can be controlled via the following commands:
3884 @kindex set breakpoint condition-evaluation
3885 @kindex show breakpoint condition-evaluation
3887 @item set breakpoint condition-evaluation host
3888 This option commands @value{GDBN} to evaluate the breakpoint
3889 conditions on the host's side. Unconditional breakpoints are sent to
3890 the target which in turn receives the triggers and reports them back to GDB
3891 for condition evaluation. This is the standard evaluation mode.
3893 @item set breakpoint condition-evaluation target
3894 This option commands @value{GDBN} to download breakpoint conditions
3895 to the target at the moment of their insertion. The target
3896 is responsible for evaluating the conditional expression and reporting
3897 breakpoint stop events back to @value{GDBN} whenever the condition
3898 is true. Due to limitations of target-side evaluation, some conditions
3899 cannot be evaluated there, e.g., conditions that depend on local data
3900 that is only known to the host. Examples include
3901 conditional expressions involving convenience variables, complex types
3902 that cannot be handled by the agent expression parser and expressions
3903 that are too long to be sent over to the target, specially when the
3904 target is a remote system. In these cases, the conditions will be
3905 evaluated by @value{GDBN}.
3907 @item set breakpoint condition-evaluation auto
3908 This is the default mode. If the target supports evaluating breakpoint
3909 conditions on its end, @value{GDBN} will download breakpoint conditions to
3910 the target (limitations mentioned previously apply). If the target does
3911 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3912 to evaluating all these conditions on the host's side.
3916 @cindex negative breakpoint numbers
3917 @cindex internal @value{GDBN} breakpoints
3918 @value{GDBN} itself sometimes sets breakpoints in your program for
3919 special purposes, such as proper handling of @code{longjmp} (in C
3920 programs). These internal breakpoints are assigned negative numbers,
3921 starting with @code{-1}; @samp{info breakpoints} does not display them.
3922 You can see these breakpoints with the @value{GDBN} maintenance command
3923 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3926 @node Set Watchpoints
3927 @subsection Setting Watchpoints
3929 @cindex setting watchpoints
3930 You can use a watchpoint to stop execution whenever the value of an
3931 expression changes, without having to predict a particular place where
3932 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3933 The expression may be as simple as the value of a single variable, or
3934 as complex as many variables combined by operators. Examples include:
3938 A reference to the value of a single variable.
3941 An address cast to an appropriate data type. For example,
3942 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3943 address (assuming an @code{int} occupies 4 bytes).
3946 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3947 expression can use any operators valid in the program's native
3948 language (@pxref{Languages}).
3951 You can set a watchpoint on an expression even if the expression can
3952 not be evaluated yet. For instance, you can set a watchpoint on
3953 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3954 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3955 the expression produces a valid value. If the expression becomes
3956 valid in some other way than changing a variable (e.g.@: if the memory
3957 pointed to by @samp{*global_ptr} becomes readable as the result of a
3958 @code{malloc} call), @value{GDBN} may not stop until the next time
3959 the expression changes.
3961 @cindex software watchpoints
3962 @cindex hardware watchpoints
3963 Depending on your system, watchpoints may be implemented in software or
3964 hardware. @value{GDBN} does software watchpointing by single-stepping your
3965 program and testing the variable's value each time, which is hundreds of
3966 times slower than normal execution. (But this may still be worth it, to
3967 catch errors where you have no clue what part of your program is the
3970 On some systems, such as most PowerPC or x86-based targets,
3971 @value{GDBN} includes support for hardware watchpoints, which do not
3972 slow down the running of your program.
3976 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3977 Set a watchpoint for an expression. @value{GDBN} will break when the
3978 expression @var{expr} is written into by the program and its value
3979 changes. The simplest (and the most popular) use of this command is
3980 to watch the value of a single variable:
3983 (@value{GDBP}) watch foo
3986 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3987 argument, @value{GDBN} breaks only when the thread identified by
3988 @var{threadnum} changes the value of @var{expr}. If any other threads
3989 change the value of @var{expr}, @value{GDBN} will not break. Note
3990 that watchpoints restricted to a single thread in this way only work
3991 with Hardware Watchpoints.
3993 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3994 (see below). The @code{-location} argument tells @value{GDBN} to
3995 instead watch the memory referred to by @var{expr}. In this case,
3996 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3997 and watch the memory at that address. The type of the result is used
3998 to determine the size of the watched memory. If the expression's
3999 result does not have an address, then @value{GDBN} will print an
4002 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4003 of masked watchpoints, if the current architecture supports this
4004 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4005 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4006 to an address to watch. The mask specifies that some bits of an address
4007 (the bits which are reset in the mask) should be ignored when matching
4008 the address accessed by the inferior against the watchpoint address.
4009 Thus, a masked watchpoint watches many addresses simultaneously---those
4010 addresses whose unmasked bits are identical to the unmasked bits in the
4011 watchpoint address. The @code{mask} argument implies @code{-location}.
4015 (@value{GDBP}) watch foo mask 0xffff00ff
4016 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4020 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4021 Set a watchpoint that will break when the value of @var{expr} is read
4025 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4026 Set a watchpoint that will break when @var{expr} is either read from
4027 or written into by the program.
4029 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4030 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4031 This command prints a list of watchpoints, using the same format as
4032 @code{info break} (@pxref{Set Breaks}).
4035 If you watch for a change in a numerically entered address you need to
4036 dereference it, as the address itself is just a constant number which will
4037 never change. @value{GDBN} refuses to create a watchpoint that watches
4038 a never-changing value:
4041 (@value{GDBP}) watch 0x600850
4042 Cannot watch constant value 0x600850.
4043 (@value{GDBP}) watch *(int *) 0x600850
4044 Watchpoint 1: *(int *) 6293584
4047 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4048 watchpoints execute very quickly, and the debugger reports a change in
4049 value at the exact instruction where the change occurs. If @value{GDBN}
4050 cannot set a hardware watchpoint, it sets a software watchpoint, which
4051 executes more slowly and reports the change in value at the next
4052 @emph{statement}, not the instruction, after the change occurs.
4054 @cindex use only software watchpoints
4055 You can force @value{GDBN} to use only software watchpoints with the
4056 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4057 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4058 the underlying system supports them. (Note that hardware-assisted
4059 watchpoints that were set @emph{before} setting
4060 @code{can-use-hw-watchpoints} to zero will still use the hardware
4061 mechanism of watching expression values.)
4064 @item set can-use-hw-watchpoints
4065 @kindex set can-use-hw-watchpoints
4066 Set whether or not to use hardware watchpoints.
4068 @item show can-use-hw-watchpoints
4069 @kindex show can-use-hw-watchpoints
4070 Show the current mode of using hardware watchpoints.
4073 For remote targets, you can restrict the number of hardware
4074 watchpoints @value{GDBN} will use, see @ref{set remote
4075 hardware-breakpoint-limit}.
4077 When you issue the @code{watch} command, @value{GDBN} reports
4080 Hardware watchpoint @var{num}: @var{expr}
4084 if it was able to set a hardware watchpoint.
4086 Currently, the @code{awatch} and @code{rwatch} commands can only set
4087 hardware watchpoints, because accesses to data that don't change the
4088 value of the watched expression cannot be detected without examining
4089 every instruction as it is being executed, and @value{GDBN} does not do
4090 that currently. If @value{GDBN} finds that it is unable to set a
4091 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4092 will print a message like this:
4095 Expression cannot be implemented with read/access watchpoint.
4098 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4099 data type of the watched expression is wider than what a hardware
4100 watchpoint on the target machine can handle. For example, some systems
4101 can only watch regions that are up to 4 bytes wide; on such systems you
4102 cannot set hardware watchpoints for an expression that yields a
4103 double-precision floating-point number (which is typically 8 bytes
4104 wide). As a work-around, it might be possible to break the large region
4105 into a series of smaller ones and watch them with separate watchpoints.
4107 If you set too many hardware watchpoints, @value{GDBN} might be unable
4108 to insert all of them when you resume the execution of your program.
4109 Since the precise number of active watchpoints is unknown until such
4110 time as the program is about to be resumed, @value{GDBN} might not be
4111 able to warn you about this when you set the watchpoints, and the
4112 warning will be printed only when the program is resumed:
4115 Hardware watchpoint @var{num}: Could not insert watchpoint
4119 If this happens, delete or disable some of the watchpoints.
4121 Watching complex expressions that reference many variables can also
4122 exhaust the resources available for hardware-assisted watchpoints.
4123 That's because @value{GDBN} needs to watch every variable in the
4124 expression with separately allocated resources.
4126 If you call a function interactively using @code{print} or @code{call},
4127 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4128 kind of breakpoint or the call completes.
4130 @value{GDBN} automatically deletes watchpoints that watch local
4131 (automatic) variables, or expressions that involve such variables, when
4132 they go out of scope, that is, when the execution leaves the block in
4133 which these variables were defined. In particular, when the program
4134 being debugged terminates, @emph{all} local variables go out of scope,
4135 and so only watchpoints that watch global variables remain set. If you
4136 rerun the program, you will need to set all such watchpoints again. One
4137 way of doing that would be to set a code breakpoint at the entry to the
4138 @code{main} function and when it breaks, set all the watchpoints.
4140 @cindex watchpoints and threads
4141 @cindex threads and watchpoints
4142 In multi-threaded programs, watchpoints will detect changes to the
4143 watched expression from every thread.
4146 @emph{Warning:} In multi-threaded programs, software watchpoints
4147 have only limited usefulness. If @value{GDBN} creates a software
4148 watchpoint, it can only watch the value of an expression @emph{in a
4149 single thread}. If you are confident that the expression can only
4150 change due to the current thread's activity (and if you are also
4151 confident that no other thread can become current), then you can use
4152 software watchpoints as usual. However, @value{GDBN} may not notice
4153 when a non-current thread's activity changes the expression. (Hardware
4154 watchpoints, in contrast, watch an expression in all threads.)
4157 @xref{set remote hardware-watchpoint-limit}.
4159 @node Set Catchpoints
4160 @subsection Setting Catchpoints
4161 @cindex catchpoints, setting
4162 @cindex exception handlers
4163 @cindex event handling
4165 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4166 kinds of program events, such as C@t{++} exceptions or the loading of a
4167 shared library. Use the @code{catch} command to set a catchpoint.
4171 @item catch @var{event}
4172 Stop when @var{event} occurs. The @var{event} can be any of the following:
4175 @item throw @r{[}@var{regexp}@r{]}
4176 @itemx rethrow @r{[}@var{regexp}@r{]}
4177 @itemx catch @r{[}@var{regexp}@r{]}
4179 @kindex catch rethrow
4181 @cindex stop on C@t{++} exceptions
4182 The throwing, re-throwing, or catching of a C@t{++} exception.
4184 If @var{regexp} is given, then only exceptions whose type matches the
4185 regular expression will be caught.
4187 @vindex $_exception@r{, convenience variable}
4188 The convenience variable @code{$_exception} is available at an
4189 exception-related catchpoint, on some systems. This holds the
4190 exception being thrown.
4192 There are currently some limitations to C@t{++} exception handling in
4197 The support for these commands is system-dependent. Currently, only
4198 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4202 The regular expression feature and the @code{$_exception} convenience
4203 variable rely on the presence of some SDT probes in @code{libstdc++}.
4204 If these probes are not present, then these features cannot be used.
4205 These probes were first available in the GCC 4.8 release, but whether
4206 or not they are available in your GCC also depends on how it was
4210 The @code{$_exception} convenience variable is only valid at the
4211 instruction at which an exception-related catchpoint is set.
4214 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4215 location in the system library which implements runtime exception
4216 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4217 (@pxref{Selection}) to get to your code.
4220 If you call a function interactively, @value{GDBN} normally returns
4221 control to you when the function has finished executing. If the call
4222 raises an exception, however, the call may bypass the mechanism that
4223 returns control to you and cause your program either to abort or to
4224 simply continue running until it hits a breakpoint, catches a signal
4225 that @value{GDBN} is listening for, or exits. This is the case even if
4226 you set a catchpoint for the exception; catchpoints on exceptions are
4227 disabled within interactive calls. @xref{Calling}, for information on
4228 controlling this with @code{set unwind-on-terminating-exception}.
4231 You cannot raise an exception interactively.
4234 You cannot install an exception handler interactively.
4238 @kindex catch exception
4239 @cindex Ada exception catching
4240 @cindex catch Ada exceptions
4241 An Ada exception being raised. If an exception name is specified
4242 at the end of the command (eg @code{catch exception Program_Error}),
4243 the debugger will stop only when this specific exception is raised.
4244 Otherwise, the debugger stops execution when any Ada exception is raised.
4246 When inserting an exception catchpoint on a user-defined exception whose
4247 name is identical to one of the exceptions defined by the language, the
4248 fully qualified name must be used as the exception name. Otherwise,
4249 @value{GDBN} will assume that it should stop on the pre-defined exception
4250 rather than the user-defined one. For instance, assuming an exception
4251 called @code{Constraint_Error} is defined in package @code{Pck}, then
4252 the command to use to catch such exceptions is @kbd{catch exception
4253 Pck.Constraint_Error}.
4255 @item exception unhandled
4256 @kindex catch exception unhandled
4257 An exception that was raised but is not handled by the program.
4260 @kindex catch assert
4261 A failed Ada assertion.
4265 @cindex break on fork/exec
4266 A call to @code{exec}.
4269 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4270 @kindex catch syscall
4271 @cindex break on a system call.
4272 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4273 syscall is a mechanism for application programs to request a service
4274 from the operating system (OS) or one of the OS system services.
4275 @value{GDBN} can catch some or all of the syscalls issued by the
4276 debuggee, and show the related information for each syscall. If no
4277 argument is specified, calls to and returns from all system calls
4280 @var{name} can be any system call name that is valid for the
4281 underlying OS. Just what syscalls are valid depends on the OS. On
4282 GNU and Unix systems, you can find the full list of valid syscall
4283 names on @file{/usr/include/asm/unistd.h}.
4285 @c For MS-Windows, the syscall names and the corresponding numbers
4286 @c can be found, e.g., on this URL:
4287 @c http://www.metasploit.com/users/opcode/syscalls.html
4288 @c but we don't support Windows syscalls yet.
4290 Normally, @value{GDBN} knows in advance which syscalls are valid for
4291 each OS, so you can use the @value{GDBN} command-line completion
4292 facilities (@pxref{Completion,, command completion}) to list the
4295 You may also specify the system call numerically. A syscall's
4296 number is the value passed to the OS's syscall dispatcher to
4297 identify the requested service. When you specify the syscall by its
4298 name, @value{GDBN} uses its database of syscalls to convert the name
4299 into the corresponding numeric code, but using the number directly
4300 may be useful if @value{GDBN}'s database does not have the complete
4301 list of syscalls on your system (e.g., because @value{GDBN} lags
4302 behind the OS upgrades).
4304 The example below illustrates how this command works if you don't provide
4308 (@value{GDBP}) catch syscall
4309 Catchpoint 1 (syscall)
4311 Starting program: /tmp/catch-syscall
4313 Catchpoint 1 (call to syscall 'close'), \
4314 0xffffe424 in __kernel_vsyscall ()
4318 Catchpoint 1 (returned from syscall 'close'), \
4319 0xffffe424 in __kernel_vsyscall ()
4323 Here is an example of catching a system call by name:
4326 (@value{GDBP}) catch syscall chroot
4327 Catchpoint 1 (syscall 'chroot' [61])
4329 Starting program: /tmp/catch-syscall
4331 Catchpoint 1 (call to syscall 'chroot'), \
4332 0xffffe424 in __kernel_vsyscall ()
4336 Catchpoint 1 (returned from syscall 'chroot'), \
4337 0xffffe424 in __kernel_vsyscall ()
4341 An example of specifying a system call numerically. In the case
4342 below, the syscall number has a corresponding entry in the XML
4343 file, so @value{GDBN} finds its name and prints it:
4346 (@value{GDBP}) catch syscall 252
4347 Catchpoint 1 (syscall(s) 'exit_group')
4349 Starting program: /tmp/catch-syscall
4351 Catchpoint 1 (call to syscall 'exit_group'), \
4352 0xffffe424 in __kernel_vsyscall ()
4356 Program exited normally.
4360 However, there can be situations when there is no corresponding name
4361 in XML file for that syscall number. In this case, @value{GDBN} prints
4362 a warning message saying that it was not able to find the syscall name,
4363 but the catchpoint will be set anyway. See the example below:
4366 (@value{GDBP}) catch syscall 764
4367 warning: The number '764' does not represent a known syscall.
4368 Catchpoint 2 (syscall 764)
4372 If you configure @value{GDBN} using the @samp{--without-expat} option,
4373 it will not be able to display syscall names. Also, if your
4374 architecture does not have an XML file describing its system calls,
4375 you will not be able to see the syscall names. It is important to
4376 notice that these two features are used for accessing the syscall
4377 name database. In either case, you will see a warning like this:
4380 (@value{GDBP}) catch syscall
4381 warning: Could not open "syscalls/i386-linux.xml"
4382 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4383 GDB will not be able to display syscall names.
4384 Catchpoint 1 (syscall)
4388 Of course, the file name will change depending on your architecture and system.
4390 Still using the example above, you can also try to catch a syscall by its
4391 number. In this case, you would see something like:
4394 (@value{GDBP}) catch syscall 252
4395 Catchpoint 1 (syscall(s) 252)
4398 Again, in this case @value{GDBN} would not be able to display syscall's names.
4402 A call to @code{fork}.
4406 A call to @code{vfork}.
4408 @item load @r{[}regexp@r{]}
4409 @itemx unload @r{[}regexp@r{]}
4411 @kindex catch unload
4412 The loading or unloading of a shared library. If @var{regexp} is
4413 given, then the catchpoint will stop only if the regular expression
4414 matches one of the affected libraries.
4416 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4417 @kindex catch signal
4418 The delivery of a signal.
4420 With no arguments, this catchpoint will catch any signal that is not
4421 used internally by @value{GDBN}, specifically, all signals except
4422 @samp{SIGTRAP} and @samp{SIGINT}.
4424 With the argument @samp{all}, all signals, including those used by
4425 @value{GDBN}, will be caught. This argument cannot be used with other
4428 Otherwise, the arguments are a list of signal names as given to
4429 @code{handle} (@pxref{Signals}). Only signals specified in this list
4432 One reason that @code{catch signal} can be more useful than
4433 @code{handle} is that you can attach commands and conditions to the
4436 When a signal is caught by a catchpoint, the signal's @code{stop} and
4437 @code{print} settings, as specified by @code{handle}, are ignored.
4438 However, whether the signal is still delivered to the inferior depends
4439 on the @code{pass} setting; this can be changed in the catchpoint's
4444 @item tcatch @var{event}
4446 Set a catchpoint that is enabled only for one stop. The catchpoint is
4447 automatically deleted after the first time the event is caught.
4451 Use the @code{info break} command to list the current catchpoints.
4455 @subsection Deleting Breakpoints
4457 @cindex clearing breakpoints, watchpoints, catchpoints
4458 @cindex deleting breakpoints, watchpoints, catchpoints
4459 It is often necessary to eliminate a breakpoint, watchpoint, or
4460 catchpoint once it has done its job and you no longer want your program
4461 to stop there. This is called @dfn{deleting} the breakpoint. A
4462 breakpoint that has been deleted no longer exists; it is forgotten.
4464 With the @code{clear} command you can delete breakpoints according to
4465 where they are in your program. With the @code{delete} command you can
4466 delete individual breakpoints, watchpoints, or catchpoints by specifying
4467 their breakpoint numbers.
4469 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4470 automatically ignores breakpoints on the first instruction to be executed
4471 when you continue execution without changing the execution address.
4476 Delete any breakpoints at the next instruction to be executed in the
4477 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4478 the innermost frame is selected, this is a good way to delete a
4479 breakpoint where your program just stopped.
4481 @item clear @var{location}
4482 Delete any breakpoints set at the specified @var{location}.
4483 @xref{Specify Location}, for the various forms of @var{location}; the
4484 most useful ones are listed below:
4487 @item clear @var{function}
4488 @itemx clear @var{filename}:@var{function}
4489 Delete any breakpoints set at entry to the named @var{function}.
4491 @item clear @var{linenum}
4492 @itemx clear @var{filename}:@var{linenum}
4493 Delete any breakpoints set at or within the code of the specified
4494 @var{linenum} of the specified @var{filename}.
4497 @cindex delete breakpoints
4499 @kindex d @r{(@code{delete})}
4500 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4501 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4502 ranges specified as arguments. If no argument is specified, delete all
4503 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4504 confirm off}). You can abbreviate this command as @code{d}.
4508 @subsection Disabling Breakpoints
4510 @cindex enable/disable a breakpoint
4511 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4512 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4513 it had been deleted, but remembers the information on the breakpoint so
4514 that you can @dfn{enable} it again later.
4516 You disable and enable breakpoints, watchpoints, and catchpoints with
4517 the @code{enable} and @code{disable} commands, optionally specifying
4518 one or more breakpoint numbers as arguments. Use @code{info break} to
4519 print a list of all breakpoints, watchpoints, and catchpoints if you
4520 do not know which numbers to use.
4522 Disabling and enabling a breakpoint that has multiple locations
4523 affects all of its locations.
4525 A breakpoint, watchpoint, or catchpoint can have any of several
4526 different states of enablement:
4530 Enabled. The breakpoint stops your program. A breakpoint set
4531 with the @code{break} command starts out in this state.
4533 Disabled. The breakpoint has no effect on your program.
4535 Enabled once. The breakpoint stops your program, but then becomes
4538 Enabled for a count. The breakpoint stops your program for the next
4539 N times, then becomes disabled.
4541 Enabled for deletion. The breakpoint stops your program, but
4542 immediately after it does so it is deleted permanently. A breakpoint
4543 set with the @code{tbreak} command starts out in this state.
4546 You can use the following commands to enable or disable breakpoints,
4547 watchpoints, and catchpoints:
4551 @kindex dis @r{(@code{disable})}
4552 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4553 Disable the specified breakpoints---or all breakpoints, if none are
4554 listed. A disabled breakpoint has no effect but is not forgotten. All
4555 options such as ignore-counts, conditions and commands are remembered in
4556 case the breakpoint is enabled again later. You may abbreviate
4557 @code{disable} as @code{dis}.
4560 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4561 Enable the specified breakpoints (or all defined breakpoints). They
4562 become effective once again in stopping your program.
4564 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4565 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4566 of these breakpoints immediately after stopping your program.
4568 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4569 Enable the specified breakpoints temporarily. @value{GDBN} records
4570 @var{count} with each of the specified breakpoints, and decrements a
4571 breakpoint's count when it is hit. When any count reaches 0,
4572 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4573 count (@pxref{Conditions, ,Break Conditions}), that will be
4574 decremented to 0 before @var{count} is affected.
4576 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4577 Enable the specified breakpoints to work once, then die. @value{GDBN}
4578 deletes any of these breakpoints as soon as your program stops there.
4579 Breakpoints set by the @code{tbreak} command start out in this state.
4582 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4583 @c confusing: tbreak is also initially enabled.
4584 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4585 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4586 subsequently, they become disabled or enabled only when you use one of
4587 the commands above. (The command @code{until} can set and delete a
4588 breakpoint of its own, but it does not change the state of your other
4589 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4593 @subsection Break Conditions
4594 @cindex conditional breakpoints
4595 @cindex breakpoint conditions
4597 @c FIXME what is scope of break condition expr? Context where wanted?
4598 @c in particular for a watchpoint?
4599 The simplest sort of breakpoint breaks every time your program reaches a
4600 specified place. You can also specify a @dfn{condition} for a
4601 breakpoint. A condition is just a Boolean expression in your
4602 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4603 a condition evaluates the expression each time your program reaches it,
4604 and your program stops only if the condition is @emph{true}.
4606 This is the converse of using assertions for program validation; in that
4607 situation, you want to stop when the assertion is violated---that is,
4608 when the condition is false. In C, if you want to test an assertion expressed
4609 by the condition @var{assert}, you should set the condition
4610 @samp{! @var{assert}} on the appropriate breakpoint.
4612 Conditions are also accepted for watchpoints; you may not need them,
4613 since a watchpoint is inspecting the value of an expression anyhow---but
4614 it might be simpler, say, to just set a watchpoint on a variable name,
4615 and specify a condition that tests whether the new value is an interesting
4618 Break conditions can have side effects, and may even call functions in
4619 your program. This can be useful, for example, to activate functions
4620 that log program progress, or to use your own print functions to
4621 format special data structures. The effects are completely predictable
4622 unless there is another enabled breakpoint at the same address. (In
4623 that case, @value{GDBN} might see the other breakpoint first and stop your
4624 program without checking the condition of this one.) Note that
4625 breakpoint commands are usually more convenient and flexible than break
4627 purpose of performing side effects when a breakpoint is reached
4628 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4630 Breakpoint conditions can also be evaluated on the target's side if
4631 the target supports it. Instead of evaluating the conditions locally,
4632 @value{GDBN} encodes the expression into an agent expression
4633 (@pxref{Agent Expressions}) suitable for execution on the target,
4634 independently of @value{GDBN}. Global variables become raw memory
4635 locations, locals become stack accesses, and so forth.
4637 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4638 when its condition evaluates to true. This mechanism may provide faster
4639 response times depending on the performance characteristics of the target
4640 since it does not need to keep @value{GDBN} informed about
4641 every breakpoint trigger, even those with false conditions.
4643 Break conditions can be specified when a breakpoint is set, by using
4644 @samp{if} in the arguments to the @code{break} command. @xref{Set
4645 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4646 with the @code{condition} command.
4648 You can also use the @code{if} keyword with the @code{watch} command.
4649 The @code{catch} command does not recognize the @code{if} keyword;
4650 @code{condition} is the only way to impose a further condition on a
4655 @item condition @var{bnum} @var{expression}
4656 Specify @var{expression} as the break condition for breakpoint,
4657 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4658 breakpoint @var{bnum} stops your program only if the value of
4659 @var{expression} is true (nonzero, in C). When you use
4660 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4661 syntactic correctness, and to determine whether symbols in it have
4662 referents in the context of your breakpoint. If @var{expression} uses
4663 symbols not referenced in the context of the breakpoint, @value{GDBN}
4664 prints an error message:
4667 No symbol "foo" in current context.
4672 not actually evaluate @var{expression} at the time the @code{condition}
4673 command (or a command that sets a breakpoint with a condition, like
4674 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4676 @item condition @var{bnum}
4677 Remove the condition from breakpoint number @var{bnum}. It becomes
4678 an ordinary unconditional breakpoint.
4681 @cindex ignore count (of breakpoint)
4682 A special case of a breakpoint condition is to stop only when the
4683 breakpoint has been reached a certain number of times. This is so
4684 useful that there is a special way to do it, using the @dfn{ignore
4685 count} of the breakpoint. Every breakpoint has an ignore count, which
4686 is an integer. Most of the time, the ignore count is zero, and
4687 therefore has no effect. But if your program reaches a breakpoint whose
4688 ignore count is positive, then instead of stopping, it just decrements
4689 the ignore count by one and continues. As a result, if the ignore count
4690 value is @var{n}, the breakpoint does not stop the next @var{n} times
4691 your program reaches it.
4695 @item ignore @var{bnum} @var{count}
4696 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4697 The next @var{count} times the breakpoint is reached, your program's
4698 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4701 To make the breakpoint stop the next time it is reached, specify
4704 When you use @code{continue} to resume execution of your program from a
4705 breakpoint, you can specify an ignore count directly as an argument to
4706 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4707 Stepping,,Continuing and Stepping}.
4709 If a breakpoint has a positive ignore count and a condition, the
4710 condition is not checked. Once the ignore count reaches zero,
4711 @value{GDBN} resumes checking the condition.
4713 You could achieve the effect of the ignore count with a condition such
4714 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4715 is decremented each time. @xref{Convenience Vars, ,Convenience
4719 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4722 @node Break Commands
4723 @subsection Breakpoint Command Lists
4725 @cindex breakpoint commands
4726 You can give any breakpoint (or watchpoint or catchpoint) a series of
4727 commands to execute when your program stops due to that breakpoint. For
4728 example, you might want to print the values of certain expressions, or
4729 enable other breakpoints.
4733 @kindex end@r{ (breakpoint commands)}
4734 @item commands @r{[}@var{range}@dots{}@r{]}
4735 @itemx @dots{} @var{command-list} @dots{}
4737 Specify a list of commands for the given breakpoints. The commands
4738 themselves appear on the following lines. Type a line containing just
4739 @code{end} to terminate the commands.
4741 To remove all commands from a breakpoint, type @code{commands} and
4742 follow it immediately with @code{end}; that is, give no commands.
4744 With no argument, @code{commands} refers to the last breakpoint,
4745 watchpoint, or catchpoint set (not to the breakpoint most recently
4746 encountered). If the most recent breakpoints were set with a single
4747 command, then the @code{commands} will apply to all the breakpoints
4748 set by that command. This applies to breakpoints set by
4749 @code{rbreak}, and also applies when a single @code{break} command
4750 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4754 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4755 disabled within a @var{command-list}.
4757 You can use breakpoint commands to start your program up again. Simply
4758 use the @code{continue} command, or @code{step}, or any other command
4759 that resumes execution.
4761 Any other commands in the command list, after a command that resumes
4762 execution, are ignored. This is because any time you resume execution
4763 (even with a simple @code{next} or @code{step}), you may encounter
4764 another breakpoint---which could have its own command list, leading to
4765 ambiguities about which list to execute.
4768 If the first command you specify in a command list is @code{silent}, the
4769 usual message about stopping at a breakpoint is not printed. This may
4770 be desirable for breakpoints that are to print a specific message and
4771 then continue. If none of the remaining commands print anything, you
4772 see no sign that the breakpoint was reached. @code{silent} is
4773 meaningful only at the beginning of a breakpoint command list.
4775 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4776 print precisely controlled output, and are often useful in silent
4777 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4779 For example, here is how you could use breakpoint commands to print the
4780 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4786 printf "x is %d\n",x
4791 One application for breakpoint commands is to compensate for one bug so
4792 you can test for another. Put a breakpoint just after the erroneous line
4793 of code, give it a condition to detect the case in which something
4794 erroneous has been done, and give it commands to assign correct values
4795 to any variables that need them. End with the @code{continue} command
4796 so that your program does not stop, and start with the @code{silent}
4797 command so that no output is produced. Here is an example:
4808 @node Dynamic Printf
4809 @subsection Dynamic Printf
4811 @cindex dynamic printf
4813 The dynamic printf command @code{dprintf} combines a breakpoint with
4814 formatted printing of your program's data to give you the effect of
4815 inserting @code{printf} calls into your program on-the-fly, without
4816 having to recompile it.
4818 In its most basic form, the output goes to the GDB console. However,
4819 you can set the variable @code{dprintf-style} for alternate handling.
4820 For instance, you can ask to format the output by calling your
4821 program's @code{printf} function. This has the advantage that the
4822 characters go to the program's output device, so they can recorded in
4823 redirects to files and so forth.
4825 If you are doing remote debugging with a stub or agent, you can also
4826 ask to have the printf handled by the remote agent. In addition to
4827 ensuring that the output goes to the remote program's device along
4828 with any other output the program might produce, you can also ask that
4829 the dprintf remain active even after disconnecting from the remote
4830 target. Using the stub/agent is also more efficient, as it can do
4831 everything without needing to communicate with @value{GDBN}.
4835 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4836 Whenever execution reaches @var{location}, print the values of one or
4837 more @var{expressions} under the control of the string @var{template}.
4838 To print several values, separate them with commas.
4840 @item set dprintf-style @var{style}
4841 Set the dprintf output to be handled in one of several different
4842 styles enumerated below. A change of style affects all existing
4843 dynamic printfs immediately. (If you need individual control over the
4844 print commands, simply define normal breakpoints with
4845 explicitly-supplied command lists.)
4848 @kindex dprintf-style gdb
4849 Handle the output using the @value{GDBN} @code{printf} command.
4852 @kindex dprintf-style call
4853 Handle the output by calling a function in your program (normally
4857 @kindex dprintf-style agent
4858 Have the remote debugging agent (such as @code{gdbserver}) handle
4859 the output itself. This style is only available for agents that
4860 support running commands on the target.
4862 @item set dprintf-function @var{function}
4863 Set the function to call if the dprintf style is @code{call}. By
4864 default its value is @code{printf}. You may set it to any expression.
4865 that @value{GDBN} can evaluate to a function, as per the @code{call}
4868 @item set dprintf-channel @var{channel}
4869 Set a ``channel'' for dprintf. If set to a non-empty value,
4870 @value{GDBN} will evaluate it as an expression and pass the result as
4871 a first argument to the @code{dprintf-function}, in the manner of
4872 @code{fprintf} and similar functions. Otherwise, the dprintf format
4873 string will be the first argument, in the manner of @code{printf}.
4875 As an example, if you wanted @code{dprintf} output to go to a logfile
4876 that is a standard I/O stream assigned to the variable @code{mylog},
4877 you could do the following:
4880 (gdb) set dprintf-style call
4881 (gdb) set dprintf-function fprintf
4882 (gdb) set dprintf-channel mylog
4883 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4884 Dprintf 1 at 0x123456: file main.c, line 25.
4886 1 dprintf keep y 0x00123456 in main at main.c:25
4887 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4892 Note that the @code{info break} displays the dynamic printf commands
4893 as normal breakpoint commands; you can thus easily see the effect of
4894 the variable settings.
4896 @item set disconnected-dprintf on
4897 @itemx set disconnected-dprintf off
4898 @kindex set disconnected-dprintf
4899 Choose whether @code{dprintf} commands should continue to run if
4900 @value{GDBN} has disconnected from the target. This only applies
4901 if the @code{dprintf-style} is @code{agent}.
4903 @item show disconnected-dprintf off
4904 @kindex show disconnected-dprintf
4905 Show the current choice for disconnected @code{dprintf}.
4909 @value{GDBN} does not check the validity of function and channel,
4910 relying on you to supply values that are meaningful for the contexts
4911 in which they are being used. For instance, the function and channel
4912 may be the values of local variables, but if that is the case, then
4913 all enabled dynamic prints must be at locations within the scope of
4914 those locals. If evaluation fails, @value{GDBN} will report an error.
4916 @node Save Breakpoints
4917 @subsection How to save breakpoints to a file
4919 To save breakpoint definitions to a file use the @w{@code{save
4920 breakpoints}} command.
4923 @kindex save breakpoints
4924 @cindex save breakpoints to a file for future sessions
4925 @item save breakpoints [@var{filename}]
4926 This command saves all current breakpoint definitions together with
4927 their commands and ignore counts, into a file @file{@var{filename}}
4928 suitable for use in a later debugging session. This includes all
4929 types of breakpoints (breakpoints, watchpoints, catchpoints,
4930 tracepoints). To read the saved breakpoint definitions, use the
4931 @code{source} command (@pxref{Command Files}). Note that watchpoints
4932 with expressions involving local variables may fail to be recreated
4933 because it may not be possible to access the context where the
4934 watchpoint is valid anymore. Because the saved breakpoint definitions
4935 are simply a sequence of @value{GDBN} commands that recreate the
4936 breakpoints, you can edit the file in your favorite editing program,
4937 and remove the breakpoint definitions you're not interested in, or
4938 that can no longer be recreated.
4941 @node Static Probe Points
4942 @subsection Static Probe Points
4944 @cindex static probe point, SystemTap
4945 @cindex static probe point, DTrace
4946 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4947 for Statically Defined Tracing, and the probes are designed to have a tiny
4948 runtime code and data footprint, and no dynamic relocations.
4950 Currently, the following types of probes are supported on
4951 ELF-compatible systems:
4955 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4956 @acronym{SDT} probes@footnote{See
4957 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4958 for more information on how to add @code{SystemTap} @acronym{SDT}
4959 probes in your applications.}. @code{SystemTap} probes are usable
4960 from assembly, C and C@t{++} languages@footnote{See
4961 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4962 for a good reference on how the @acronym{SDT} probes are implemented.}.
4964 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
4965 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
4969 @cindex semaphores on static probe points
4970 Some @code{SystemTap} probes have an associated semaphore variable;
4971 for instance, this happens automatically if you defined your probe
4972 using a DTrace-style @file{.d} file. If your probe has a semaphore,
4973 @value{GDBN} will automatically enable it when you specify a
4974 breakpoint using the @samp{-probe-stap} notation. But, if you put a
4975 breakpoint at a probe's location by some other method (e.g.,
4976 @code{break file:line}), then @value{GDBN} will not automatically set
4977 the semaphore. @code{DTrace} probes do not support semaphores.
4979 You can examine the available static static probes using @code{info
4980 probes}, with optional arguments:
4984 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4985 If given, @var{type} is either @code{stap} for listing
4986 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
4987 probes. If omitted all probes are listed regardless of their types.
4989 If given, @var{provider} is a regular expression used to match against provider
4990 names when selecting which probes to list. If omitted, probes by all
4991 probes from all providers are listed.
4993 If given, @var{name} is a regular expression to match against probe names
4994 when selecting which probes to list. If omitted, probe names are not
4995 considered when deciding whether to display them.
4997 If given, @var{objfile} is a regular expression used to select which
4998 object files (executable or shared libraries) to examine. If not
4999 given, all object files are considered.
5001 @item info probes all
5002 List the available static probes, from all types.
5005 @cindex enabling and disabling probes
5006 Some probe points can be enabled and/or disabled. The effect of
5007 enabling or disabling a probe depends on the type of probe being
5008 handled. Some @code{DTrace} probes can be enabled or
5009 disabled, but @code{SystemTap} probes cannot be disabled.
5011 You can enable (or disable) one or more probes using the following
5012 commands, with optional arguments:
5015 @kindex enable probes
5016 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5017 If given, @var{provider} is a regular expression used to match against
5018 provider names when selecting which probes to enable. If omitted,
5019 all probes from all providers are enabled.
5021 If given, @var{name} is a regular expression to match against probe
5022 names when selecting which probes to enable. If omitted, probe names
5023 are not considered when deciding whether to enable them.
5025 If given, @var{objfile} is a regular expression used to select which
5026 object files (executable or shared libraries) to examine. If not
5027 given, all object files are considered.
5029 @kindex disable probes
5030 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5031 See the @code{enable probes} command above for a description of the
5032 optional arguments accepted by this command.
5035 @vindex $_probe_arg@r{, convenience variable}
5036 A probe may specify up to twelve arguments. These are available at the
5037 point at which the probe is defined---that is, when the current PC is
5038 at the probe's location. The arguments are available using the
5039 convenience variables (@pxref{Convenience Vars})
5040 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5041 probes each probe argument is an integer of the appropriate size;
5042 types are not preserved. In @code{DTrace} probes types are preserved
5043 provided that they are recognized as such by @value{GDBN}; otherwise
5044 the value of the probe argument will be a long integer. The
5045 convenience variable @code{$_probe_argc} holds the number of arguments
5046 at the current probe point.
5048 These variables are always available, but attempts to access them at
5049 any location other than a probe point will cause @value{GDBN} to give
5053 @c @ifclear BARETARGET
5054 @node Error in Breakpoints
5055 @subsection ``Cannot insert breakpoints''
5057 If you request too many active hardware-assisted breakpoints and
5058 watchpoints, you will see this error message:
5060 @c FIXME: the precise wording of this message may change; the relevant
5061 @c source change is not committed yet (Sep 3, 1999).
5063 Stopped; cannot insert breakpoints.
5064 You may have requested too many hardware breakpoints and watchpoints.
5068 This message is printed when you attempt to resume the program, since
5069 only then @value{GDBN} knows exactly how many hardware breakpoints and
5070 watchpoints it needs to insert.
5072 When this message is printed, you need to disable or remove some of the
5073 hardware-assisted breakpoints and watchpoints, and then continue.
5075 @node Breakpoint-related Warnings
5076 @subsection ``Breakpoint address adjusted...''
5077 @cindex breakpoint address adjusted
5079 Some processor architectures place constraints on the addresses at
5080 which breakpoints may be placed. For architectures thus constrained,
5081 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5082 with the constraints dictated by the architecture.
5084 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5085 a VLIW architecture in which a number of RISC-like instructions may be
5086 bundled together for parallel execution. The FR-V architecture
5087 constrains the location of a breakpoint instruction within such a
5088 bundle to the instruction with the lowest address. @value{GDBN}
5089 honors this constraint by adjusting a breakpoint's address to the
5090 first in the bundle.
5092 It is not uncommon for optimized code to have bundles which contain
5093 instructions from different source statements, thus it may happen that
5094 a breakpoint's address will be adjusted from one source statement to
5095 another. Since this adjustment may significantly alter @value{GDBN}'s
5096 breakpoint related behavior from what the user expects, a warning is
5097 printed when the breakpoint is first set and also when the breakpoint
5100 A warning like the one below is printed when setting a breakpoint
5101 that's been subject to address adjustment:
5104 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5107 Such warnings are printed both for user settable and @value{GDBN}'s
5108 internal breakpoints. If you see one of these warnings, you should
5109 verify that a breakpoint set at the adjusted address will have the
5110 desired affect. If not, the breakpoint in question may be removed and
5111 other breakpoints may be set which will have the desired behavior.
5112 E.g., it may be sufficient to place the breakpoint at a later
5113 instruction. A conditional breakpoint may also be useful in some
5114 cases to prevent the breakpoint from triggering too often.
5116 @value{GDBN} will also issue a warning when stopping at one of these
5117 adjusted breakpoints:
5120 warning: Breakpoint 1 address previously adjusted from 0x00010414
5124 When this warning is encountered, it may be too late to take remedial
5125 action except in cases where the breakpoint is hit earlier or more
5126 frequently than expected.
5128 @node Continuing and Stepping
5129 @section Continuing and Stepping
5133 @cindex resuming execution
5134 @dfn{Continuing} means resuming program execution until your program
5135 completes normally. In contrast, @dfn{stepping} means executing just
5136 one more ``step'' of your program, where ``step'' may mean either one
5137 line of source code, or one machine instruction (depending on what
5138 particular command you use). Either when continuing or when stepping,
5139 your program may stop even sooner, due to a breakpoint or a signal. (If
5140 it stops due to a signal, you may want to use @code{handle}, or use
5141 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5142 or you may step into the signal's handler (@pxref{stepping and signal
5147 @kindex c @r{(@code{continue})}
5148 @kindex fg @r{(resume foreground execution)}
5149 @item continue @r{[}@var{ignore-count}@r{]}
5150 @itemx c @r{[}@var{ignore-count}@r{]}
5151 @itemx fg @r{[}@var{ignore-count}@r{]}
5152 Resume program execution, at the address where your program last stopped;
5153 any breakpoints set at that address are bypassed. The optional argument
5154 @var{ignore-count} allows you to specify a further number of times to
5155 ignore a breakpoint at this location; its effect is like that of
5156 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5158 The argument @var{ignore-count} is meaningful only when your program
5159 stopped due to a breakpoint. At other times, the argument to
5160 @code{continue} is ignored.
5162 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5163 debugged program is deemed to be the foreground program) are provided
5164 purely for convenience, and have exactly the same behavior as
5168 To resume execution at a different place, you can use @code{return}
5169 (@pxref{Returning, ,Returning from a Function}) to go back to the
5170 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5171 Different Address}) to go to an arbitrary location in your program.
5173 A typical technique for using stepping is to set a breakpoint
5174 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5175 beginning of the function or the section of your program where a problem
5176 is believed to lie, run your program until it stops at that breakpoint,
5177 and then step through the suspect area, examining the variables that are
5178 interesting, until you see the problem happen.
5182 @kindex s @r{(@code{step})}
5184 Continue running your program until control reaches a different source
5185 line, then stop it and return control to @value{GDBN}. This command is
5186 abbreviated @code{s}.
5189 @c "without debugging information" is imprecise; actually "without line
5190 @c numbers in the debugging information". (gcc -g1 has debugging info but
5191 @c not line numbers). But it seems complex to try to make that
5192 @c distinction here.
5193 @emph{Warning:} If you use the @code{step} command while control is
5194 within a function that was compiled without debugging information,
5195 execution proceeds until control reaches a function that does have
5196 debugging information. Likewise, it will not step into a function which
5197 is compiled without debugging information. To step through functions
5198 without debugging information, use the @code{stepi} command, described
5202 The @code{step} command only stops at the first instruction of a source
5203 line. This prevents the multiple stops that could otherwise occur in
5204 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5205 to stop if a function that has debugging information is called within
5206 the line. In other words, @code{step} @emph{steps inside} any functions
5207 called within the line.
5209 Also, the @code{step} command only enters a function if there is line
5210 number information for the function. Otherwise it acts like the
5211 @code{next} command. This avoids problems when using @code{cc -gl}
5212 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5213 was any debugging information about the routine.
5215 @item step @var{count}
5216 Continue running as in @code{step}, but do so @var{count} times. If a
5217 breakpoint is reached, or a signal not related to stepping occurs before
5218 @var{count} steps, stepping stops right away.
5221 @kindex n @r{(@code{next})}
5222 @item next @r{[}@var{count}@r{]}
5223 Continue to the next source line in the current (innermost) stack frame.
5224 This is similar to @code{step}, but function calls that appear within
5225 the line of code are executed without stopping. Execution stops when
5226 control reaches a different line of code at the original stack level
5227 that was executing when you gave the @code{next} command. This command
5228 is abbreviated @code{n}.
5230 An argument @var{count} is a repeat count, as for @code{step}.
5233 @c FIX ME!! Do we delete this, or is there a way it fits in with
5234 @c the following paragraph? --- Vctoria
5236 @c @code{next} within a function that lacks debugging information acts like
5237 @c @code{step}, but any function calls appearing within the code of the
5238 @c function are executed without stopping.
5240 The @code{next} command only stops at the first instruction of a
5241 source line. This prevents multiple stops that could otherwise occur in
5242 @code{switch} statements, @code{for} loops, etc.
5244 @kindex set step-mode
5246 @cindex functions without line info, and stepping
5247 @cindex stepping into functions with no line info
5248 @itemx set step-mode on
5249 The @code{set step-mode on} command causes the @code{step} command to
5250 stop at the first instruction of a function which contains no debug line
5251 information rather than stepping over it.
5253 This is useful in cases where you may be interested in inspecting the
5254 machine instructions of a function which has no symbolic info and do not
5255 want @value{GDBN} to automatically skip over this function.
5257 @item set step-mode off
5258 Causes the @code{step} command to step over any functions which contains no
5259 debug information. This is the default.
5261 @item show step-mode
5262 Show whether @value{GDBN} will stop in or step over functions without
5263 source line debug information.
5266 @kindex fin @r{(@code{finish})}
5268 Continue running until just after function in the selected stack frame
5269 returns. Print the returned value (if any). This command can be
5270 abbreviated as @code{fin}.
5272 Contrast this with the @code{return} command (@pxref{Returning,
5273 ,Returning from a Function}).
5276 @kindex u @r{(@code{until})}
5277 @cindex run until specified location
5280 Continue running until a source line past the current line, in the
5281 current stack frame, is reached. This command is used to avoid single
5282 stepping through a loop more than once. It is like the @code{next}
5283 command, except that when @code{until} encounters a jump, it
5284 automatically continues execution until the program counter is greater
5285 than the address of the jump.
5287 This means that when you reach the end of a loop after single stepping
5288 though it, @code{until} makes your program continue execution until it
5289 exits the loop. In contrast, a @code{next} command at the end of a loop
5290 simply steps back to the beginning of the loop, which forces you to step
5291 through the next iteration.
5293 @code{until} always stops your program if it attempts to exit the current
5296 @code{until} may produce somewhat counterintuitive results if the order
5297 of machine code does not match the order of the source lines. For
5298 example, in the following excerpt from a debugging session, the @code{f}
5299 (@code{frame}) command shows that execution is stopped at line
5300 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5304 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5306 (@value{GDBP}) until
5307 195 for ( ; argc > 0; NEXTARG) @{
5310 This happened because, for execution efficiency, the compiler had
5311 generated code for the loop closure test at the end, rather than the
5312 start, of the loop---even though the test in a C @code{for}-loop is
5313 written before the body of the loop. The @code{until} command appeared
5314 to step back to the beginning of the loop when it advanced to this
5315 expression; however, it has not really gone to an earlier
5316 statement---not in terms of the actual machine code.
5318 @code{until} with no argument works by means of single
5319 instruction stepping, and hence is slower than @code{until} with an
5322 @item until @var{location}
5323 @itemx u @var{location}
5324 Continue running your program until either the specified @var{location} is
5325 reached, or the current stack frame returns. The location is any of
5326 the forms described in @ref{Specify Location}.
5327 This form of the command uses temporary breakpoints, and
5328 hence is quicker than @code{until} without an argument. The specified
5329 location is actually reached only if it is in the current frame. This
5330 implies that @code{until} can be used to skip over recursive function
5331 invocations. For instance in the code below, if the current location is
5332 line @code{96}, issuing @code{until 99} will execute the program up to
5333 line @code{99} in the same invocation of factorial, i.e., after the inner
5334 invocations have returned.
5337 94 int factorial (int value)
5339 96 if (value > 1) @{
5340 97 value *= factorial (value - 1);
5347 @kindex advance @var{location}
5348 @item advance @var{location}
5349 Continue running the program up to the given @var{location}. An argument is
5350 required, which should be of one of the forms described in
5351 @ref{Specify Location}.
5352 Execution will also stop upon exit from the current stack
5353 frame. This command is similar to @code{until}, but @code{advance} will
5354 not skip over recursive function calls, and the target location doesn't
5355 have to be in the same frame as the current one.
5359 @kindex si @r{(@code{stepi})}
5361 @itemx stepi @var{arg}
5363 Execute one machine instruction, then stop and return to the debugger.
5365 It is often useful to do @samp{display/i $pc} when stepping by machine
5366 instructions. This makes @value{GDBN} automatically display the next
5367 instruction to be executed, each time your program stops. @xref{Auto
5368 Display,, Automatic Display}.
5370 An argument is a repeat count, as in @code{step}.
5374 @kindex ni @r{(@code{nexti})}
5376 @itemx nexti @var{arg}
5378 Execute one machine instruction, but if it is a function call,
5379 proceed until the function returns.
5381 An argument is a repeat count, as in @code{next}.
5385 @anchor{range stepping}
5386 @cindex range stepping
5387 @cindex target-assisted range stepping
5388 By default, and if available, @value{GDBN} makes use of
5389 target-assisted @dfn{range stepping}. In other words, whenever you
5390 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5391 tells the target to step the corresponding range of instruction
5392 addresses instead of issuing multiple single-steps. This speeds up
5393 line stepping, particularly for remote targets. Ideally, there should
5394 be no reason you would want to turn range stepping off. However, it's
5395 possible that a bug in the debug info, a bug in the remote stub (for
5396 remote targets), or even a bug in @value{GDBN} could make line
5397 stepping behave incorrectly when target-assisted range stepping is
5398 enabled. You can use the following command to turn off range stepping
5402 @kindex set range-stepping
5403 @kindex show range-stepping
5404 @item set range-stepping
5405 @itemx show range-stepping
5406 Control whether range stepping is enabled.
5408 If @code{on}, and the target supports it, @value{GDBN} tells the
5409 target to step a range of addresses itself, instead of issuing
5410 multiple single-steps. If @code{off}, @value{GDBN} always issues
5411 single-steps, even if range stepping is supported by the target. The
5412 default is @code{on}.
5416 @node Skipping Over Functions and Files
5417 @section Skipping Over Functions and Files
5418 @cindex skipping over functions and files
5420 The program you are debugging may contain some functions which are
5421 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5422 skip a function or all functions in a file when stepping.
5424 For example, consider the following C function:
5435 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5436 are not interested in stepping through @code{boring}. If you run @code{step}
5437 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5438 step over both @code{foo} and @code{boring}!
5440 One solution is to @code{step} into @code{boring} and use the @code{finish}
5441 command to immediately exit it. But this can become tedious if @code{boring}
5442 is called from many places.
5444 A more flexible solution is to execute @kbd{skip boring}. This instructs
5445 @value{GDBN} never to step into @code{boring}. Now when you execute
5446 @code{step} at line 103, you'll step over @code{boring} and directly into
5449 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5450 example, @code{skip file boring.c}.
5453 @kindex skip function
5454 @item skip @r{[}@var{linespec}@r{]}
5455 @itemx skip function @r{[}@var{linespec}@r{]}
5456 After running this command, the function named by @var{linespec} or the
5457 function containing the line named by @var{linespec} will be skipped over when
5458 stepping. @xref{Specify Location}.
5460 If you do not specify @var{linespec}, the function you're currently debugging
5463 (If you have a function called @code{file} that you want to skip, use
5464 @kbd{skip function file}.)
5467 @item skip file @r{[}@var{filename}@r{]}
5468 After running this command, any function whose source lives in @var{filename}
5469 will be skipped over when stepping.
5471 If you do not specify @var{filename}, functions whose source lives in the file
5472 you're currently debugging will be skipped.
5475 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5476 These are the commands for managing your list of skips:
5480 @item info skip @r{[}@var{range}@r{]}
5481 Print details about the specified skip(s). If @var{range} is not specified,
5482 print a table with details about all functions and files marked for skipping.
5483 @code{info skip} prints the following information about each skip:
5487 A number identifying this skip.
5489 The type of this skip, either @samp{function} or @samp{file}.
5490 @item Enabled or Disabled
5491 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5493 For function skips, this column indicates the address in memory of the function
5494 being skipped. If you've set a function skip on a function which has not yet
5495 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5496 which has the function is loaded, @code{info skip} will show the function's
5499 For file skips, this field contains the filename being skipped. For functions
5500 skips, this field contains the function name and its line number in the file
5501 where it is defined.
5505 @item skip delete @r{[}@var{range}@r{]}
5506 Delete the specified skip(s). If @var{range} is not specified, delete all
5510 @item skip enable @r{[}@var{range}@r{]}
5511 Enable the specified skip(s). If @var{range} is not specified, enable all
5514 @kindex skip disable
5515 @item skip disable @r{[}@var{range}@r{]}
5516 Disable the specified skip(s). If @var{range} is not specified, disable all
5525 A signal is an asynchronous event that can happen in a program. The
5526 operating system defines the possible kinds of signals, and gives each
5527 kind a name and a number. For example, in Unix @code{SIGINT} is the
5528 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5529 @code{SIGSEGV} is the signal a program gets from referencing a place in
5530 memory far away from all the areas in use; @code{SIGALRM} occurs when
5531 the alarm clock timer goes off (which happens only if your program has
5532 requested an alarm).
5534 @cindex fatal signals
5535 Some signals, including @code{SIGALRM}, are a normal part of the
5536 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5537 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5538 program has not specified in advance some other way to handle the signal.
5539 @code{SIGINT} does not indicate an error in your program, but it is normally
5540 fatal so it can carry out the purpose of the interrupt: to kill the program.
5542 @value{GDBN} has the ability to detect any occurrence of a signal in your
5543 program. You can tell @value{GDBN} in advance what to do for each kind of
5546 @cindex handling signals
5547 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5548 @code{SIGALRM} be silently passed to your program
5549 (so as not to interfere with their role in the program's functioning)
5550 but to stop your program immediately whenever an error signal happens.
5551 You can change these settings with the @code{handle} command.
5554 @kindex info signals
5558 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5559 handle each one. You can use this to see the signal numbers of all
5560 the defined types of signals.
5562 @item info signals @var{sig}
5563 Similar, but print information only about the specified signal number.
5565 @code{info handle} is an alias for @code{info signals}.
5567 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5568 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5569 for details about this command.
5572 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5573 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5574 can be the number of a signal or its name (with or without the
5575 @samp{SIG} at the beginning); a list of signal numbers of the form
5576 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5577 known signals. Optional arguments @var{keywords}, described below,
5578 say what change to make.
5582 The keywords allowed by the @code{handle} command can be abbreviated.
5583 Their full names are:
5587 @value{GDBN} should not stop your program when this signal happens. It may
5588 still print a message telling you that the signal has come in.
5591 @value{GDBN} should stop your program when this signal happens. This implies
5592 the @code{print} keyword as well.
5595 @value{GDBN} should print a message when this signal happens.
5598 @value{GDBN} should not mention the occurrence of the signal at all. This
5599 implies the @code{nostop} keyword as well.
5603 @value{GDBN} should allow your program to see this signal; your program
5604 can handle the signal, or else it may terminate if the signal is fatal
5605 and not handled. @code{pass} and @code{noignore} are synonyms.
5609 @value{GDBN} should not allow your program to see this signal.
5610 @code{nopass} and @code{ignore} are synonyms.
5614 When a signal stops your program, the signal is not visible to the
5616 continue. Your program sees the signal then, if @code{pass} is in
5617 effect for the signal in question @emph{at that time}. In other words,
5618 after @value{GDBN} reports a signal, you can use the @code{handle}
5619 command with @code{pass} or @code{nopass} to control whether your
5620 program sees that signal when you continue.
5622 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5623 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5624 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5627 You can also use the @code{signal} command to prevent your program from
5628 seeing a signal, or cause it to see a signal it normally would not see,
5629 or to give it any signal at any time. For example, if your program stopped
5630 due to some sort of memory reference error, you might store correct
5631 values into the erroneous variables and continue, hoping to see more
5632 execution; but your program would probably terminate immediately as
5633 a result of the fatal signal once it saw the signal. To prevent this,
5634 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5637 @cindex stepping and signal handlers
5638 @anchor{stepping and signal handlers}
5640 @value{GDBN} optimizes for stepping the mainline code. If a signal
5641 that has @code{handle nostop} and @code{handle pass} set arrives while
5642 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5643 in progress, @value{GDBN} lets the signal handler run and then resumes
5644 stepping the mainline code once the signal handler returns. In other
5645 words, @value{GDBN} steps over the signal handler. This prevents
5646 signals that you've specified as not interesting (with @code{handle
5647 nostop}) from changing the focus of debugging unexpectedly. Note that
5648 the signal handler itself may still hit a breakpoint, stop for another
5649 signal that has @code{handle stop} in effect, or for any other event
5650 that normally results in stopping the stepping command sooner. Also
5651 note that @value{GDBN} still informs you that the program received a
5652 signal if @code{handle print} is set.
5654 @anchor{stepping into signal handlers}
5656 If you set @code{handle pass} for a signal, and your program sets up a
5657 handler for it, then issuing a stepping command, such as @code{step}
5658 or @code{stepi}, when your program is stopped due to the signal will
5659 step @emph{into} the signal handler (if the target supports that).
5661 Likewise, if you use the @code{queue-signal} command to queue a signal
5662 to be delivered to the current thread when execution of the thread
5663 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5664 stepping command will step into the signal handler.
5666 Here's an example, using @code{stepi} to step to the first instruction
5667 of @code{SIGUSR1}'s handler:
5670 (@value{GDBP}) handle SIGUSR1
5671 Signal Stop Print Pass to program Description
5672 SIGUSR1 Yes Yes Yes User defined signal 1
5676 Program received signal SIGUSR1, User defined signal 1.
5677 main () sigusr1.c:28
5680 sigusr1_handler () at sigusr1.c:9
5684 The same, but using @code{queue-signal} instead of waiting for the
5685 program to receive the signal first:
5690 (@value{GDBP}) queue-signal SIGUSR1
5692 sigusr1_handler () at sigusr1.c:9
5697 @cindex extra signal information
5698 @anchor{extra signal information}
5700 On some targets, @value{GDBN} can inspect extra signal information
5701 associated with the intercepted signal, before it is actually
5702 delivered to the program being debugged. This information is exported
5703 by the convenience variable @code{$_siginfo}, and consists of data
5704 that is passed by the kernel to the signal handler at the time of the
5705 receipt of a signal. The data type of the information itself is
5706 target dependent. You can see the data type using the @code{ptype
5707 $_siginfo} command. On Unix systems, it typically corresponds to the
5708 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5711 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5712 referenced address that raised a segmentation fault.
5716 (@value{GDBP}) continue
5717 Program received signal SIGSEGV, Segmentation fault.
5718 0x0000000000400766 in main ()
5720 (@value{GDBP}) ptype $_siginfo
5727 struct @{...@} _kill;
5728 struct @{...@} _timer;
5730 struct @{...@} _sigchld;
5731 struct @{...@} _sigfault;
5732 struct @{...@} _sigpoll;
5735 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5739 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5740 $1 = (void *) 0x7ffff7ff7000
5744 Depending on target support, @code{$_siginfo} may also be writable.
5747 @section Stopping and Starting Multi-thread Programs
5749 @cindex stopped threads
5750 @cindex threads, stopped
5752 @cindex continuing threads
5753 @cindex threads, continuing
5755 @value{GDBN} supports debugging programs with multiple threads
5756 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5757 are two modes of controlling execution of your program within the
5758 debugger. In the default mode, referred to as @dfn{all-stop mode},
5759 when any thread in your program stops (for example, at a breakpoint
5760 or while being stepped), all other threads in the program are also stopped by
5761 @value{GDBN}. On some targets, @value{GDBN} also supports
5762 @dfn{non-stop mode}, in which other threads can continue to run freely while
5763 you examine the stopped thread in the debugger.
5766 * All-Stop Mode:: All threads stop when GDB takes control
5767 * Non-Stop Mode:: Other threads continue to execute
5768 * Background Execution:: Running your program asynchronously
5769 * Thread-Specific Breakpoints:: Controlling breakpoints
5770 * Interrupted System Calls:: GDB may interfere with system calls
5771 * Observer Mode:: GDB does not alter program behavior
5775 @subsection All-Stop Mode
5777 @cindex all-stop mode
5779 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5780 @emph{all} threads of execution stop, not just the current thread. This
5781 allows you to examine the overall state of the program, including
5782 switching between threads, without worrying that things may change
5785 Conversely, whenever you restart the program, @emph{all} threads start
5786 executing. @emph{This is true even when single-stepping} with commands
5787 like @code{step} or @code{next}.
5789 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5790 Since thread scheduling is up to your debugging target's operating
5791 system (not controlled by @value{GDBN}), other threads may
5792 execute more than one statement while the current thread completes a
5793 single step. Moreover, in general other threads stop in the middle of a
5794 statement, rather than at a clean statement boundary, when the program
5797 You might even find your program stopped in another thread after
5798 continuing or even single-stepping. This happens whenever some other
5799 thread runs into a breakpoint, a signal, or an exception before the
5800 first thread completes whatever you requested.
5802 @cindex automatic thread selection
5803 @cindex switching threads automatically
5804 @cindex threads, automatic switching
5805 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5806 signal, it automatically selects the thread where that breakpoint or
5807 signal happened. @value{GDBN} alerts you to the context switch with a
5808 message such as @samp{[Switching to Thread @var{n}]} to identify the
5811 On some OSes, you can modify @value{GDBN}'s default behavior by
5812 locking the OS scheduler to allow only a single thread to run.
5815 @item set scheduler-locking @var{mode}
5816 @cindex scheduler locking mode
5817 @cindex lock scheduler
5818 Set the scheduler locking mode. It applies to normal execution,
5819 record mode, and replay mode. If it is @code{off}, then there is no
5820 locking and any thread may run at any time. If @code{on}, then only
5821 the current thread may run when the inferior is resumed. The
5822 @code{step} mode optimizes for single-stepping; it prevents other
5823 threads from preempting the current thread while you are stepping, so
5824 that the focus of debugging does not change unexpectedly. Other
5825 threads never get a chance to run when you step, and they are
5826 completely free to run when you use commands like @samp{continue},
5827 @samp{until}, or @samp{finish}. However, unless another thread hits a
5828 breakpoint during its timeslice, @value{GDBN} does not change the
5829 current thread away from the thread that you are debugging. The
5830 @code{replay} mode behaves like @code{off} in record mode and like
5831 @code{on} in replay mode.
5833 @item show scheduler-locking
5834 Display the current scheduler locking mode.
5837 @cindex resume threads of multiple processes simultaneously
5838 By default, when you issue one of the execution commands such as
5839 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5840 threads of the current inferior to run. For example, if @value{GDBN}
5841 is attached to two inferiors, each with two threads, the
5842 @code{continue} command resumes only the two threads of the current
5843 inferior. This is useful, for example, when you debug a program that
5844 forks and you want to hold the parent stopped (so that, for instance,
5845 it doesn't run to exit), while you debug the child. In other
5846 situations, you may not be interested in inspecting the current state
5847 of any of the processes @value{GDBN} is attached to, and you may want
5848 to resume them all until some breakpoint is hit. In the latter case,
5849 you can instruct @value{GDBN} to allow all threads of all the
5850 inferiors to run with the @w{@code{set schedule-multiple}} command.
5853 @kindex set schedule-multiple
5854 @item set schedule-multiple
5855 Set the mode for allowing threads of multiple processes to be resumed
5856 when an execution command is issued. When @code{on}, all threads of
5857 all processes are allowed to run. When @code{off}, only the threads
5858 of the current process are resumed. The default is @code{off}. The
5859 @code{scheduler-locking} mode takes precedence when set to @code{on},
5860 or while you are stepping and set to @code{step}.
5862 @item show schedule-multiple
5863 Display the current mode for resuming the execution of threads of
5868 @subsection Non-Stop Mode
5870 @cindex non-stop mode
5872 @c This section is really only a place-holder, and needs to be expanded
5873 @c with more details.
5875 For some multi-threaded targets, @value{GDBN} supports an optional
5876 mode of operation in which you can examine stopped program threads in
5877 the debugger while other threads continue to execute freely. This
5878 minimizes intrusion when debugging live systems, such as programs
5879 where some threads have real-time constraints or must continue to
5880 respond to external events. This is referred to as @dfn{non-stop} mode.
5882 In non-stop mode, when a thread stops to report a debugging event,
5883 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5884 threads as well, in contrast to the all-stop mode behavior. Additionally,
5885 execution commands such as @code{continue} and @code{step} apply by default
5886 only to the current thread in non-stop mode, rather than all threads as
5887 in all-stop mode. This allows you to control threads explicitly in
5888 ways that are not possible in all-stop mode --- for example, stepping
5889 one thread while allowing others to run freely, stepping
5890 one thread while holding all others stopped, or stepping several threads
5891 independently and simultaneously.
5893 To enter non-stop mode, use this sequence of commands before you run
5894 or attach to your program:
5897 # If using the CLI, pagination breaks non-stop.
5900 # Finally, turn it on!
5904 You can use these commands to manipulate the non-stop mode setting:
5907 @kindex set non-stop
5908 @item set non-stop on
5909 Enable selection of non-stop mode.
5910 @item set non-stop off
5911 Disable selection of non-stop mode.
5912 @kindex show non-stop
5914 Show the current non-stop enablement setting.
5917 Note these commands only reflect whether non-stop mode is enabled,
5918 not whether the currently-executing program is being run in non-stop mode.
5919 In particular, the @code{set non-stop} preference is only consulted when
5920 @value{GDBN} starts or connects to the target program, and it is generally
5921 not possible to switch modes once debugging has started. Furthermore,
5922 since not all targets support non-stop mode, even when you have enabled
5923 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5926 In non-stop mode, all execution commands apply only to the current thread
5927 by default. That is, @code{continue} only continues one thread.
5928 To continue all threads, issue @code{continue -a} or @code{c -a}.
5930 You can use @value{GDBN}'s background execution commands
5931 (@pxref{Background Execution}) to run some threads in the background
5932 while you continue to examine or step others from @value{GDBN}.
5933 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5934 always executed asynchronously in non-stop mode.
5936 Suspending execution is done with the @code{interrupt} command when
5937 running in the background, or @kbd{Ctrl-c} during foreground execution.
5938 In all-stop mode, this stops the whole process;
5939 but in non-stop mode the interrupt applies only to the current thread.
5940 To stop the whole program, use @code{interrupt -a}.
5942 Other execution commands do not currently support the @code{-a} option.
5944 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5945 that thread current, as it does in all-stop mode. This is because the
5946 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5947 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5948 changed to a different thread just as you entered a command to operate on the
5949 previously current thread.
5951 @node Background Execution
5952 @subsection Background Execution
5954 @cindex foreground execution
5955 @cindex background execution
5956 @cindex asynchronous execution
5957 @cindex execution, foreground, background and asynchronous
5959 @value{GDBN}'s execution commands have two variants: the normal
5960 foreground (synchronous) behavior, and a background
5961 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5962 the program to report that some thread has stopped before prompting for
5963 another command. In background execution, @value{GDBN} immediately gives
5964 a command prompt so that you can issue other commands while your program runs.
5966 If the target doesn't support async mode, @value{GDBN} issues an error
5967 message if you attempt to use the background execution commands.
5969 To specify background execution, add a @code{&} to the command. For example,
5970 the background form of the @code{continue} command is @code{continue&}, or
5971 just @code{c&}. The execution commands that accept background execution
5977 @xref{Starting, , Starting your Program}.
5981 @xref{Attach, , Debugging an Already-running Process}.
5985 @xref{Continuing and Stepping, step}.
5989 @xref{Continuing and Stepping, stepi}.
5993 @xref{Continuing and Stepping, next}.
5997 @xref{Continuing and Stepping, nexti}.
6001 @xref{Continuing and Stepping, continue}.
6005 @xref{Continuing and Stepping, finish}.
6009 @xref{Continuing and Stepping, until}.
6013 Background execution is especially useful in conjunction with non-stop
6014 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6015 However, you can also use these commands in the normal all-stop mode with
6016 the restriction that you cannot issue another execution command until the
6017 previous one finishes. Examples of commands that are valid in all-stop
6018 mode while the program is running include @code{help} and @code{info break}.
6020 You can interrupt your program while it is running in the background by
6021 using the @code{interrupt} command.
6028 Suspend execution of the running program. In all-stop mode,
6029 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6030 only the current thread. To stop the whole program in non-stop mode,
6031 use @code{interrupt -a}.
6034 @node Thread-Specific Breakpoints
6035 @subsection Thread-Specific Breakpoints
6037 When your program has multiple threads (@pxref{Threads,, Debugging
6038 Programs with Multiple Threads}), you can choose whether to set
6039 breakpoints on all threads, or on a particular thread.
6042 @cindex breakpoints and threads
6043 @cindex thread breakpoints
6044 @kindex break @dots{} thread @var{threadno}
6045 @item break @var{location} thread @var{threadno}
6046 @itemx break @var{location} thread @var{threadno} if @dots{}
6047 @var{location} specifies source lines; there are several ways of
6048 writing them (@pxref{Specify Location}), but the effect is always to
6049 specify some source line.
6051 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
6052 to specify that you only want @value{GDBN} to stop the program when a
6053 particular thread reaches this breakpoint. The @var{threadno} specifier
6054 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
6055 in the first column of the @samp{info threads} display.
6057 If you do not specify @samp{thread @var{threadno}} when you set a
6058 breakpoint, the breakpoint applies to @emph{all} threads of your
6061 You can use the @code{thread} qualifier on conditional breakpoints as
6062 well; in this case, place @samp{thread @var{threadno}} before or
6063 after the breakpoint condition, like this:
6066 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6071 Thread-specific breakpoints are automatically deleted when
6072 @value{GDBN} detects the corresponding thread is no longer in the
6073 thread list. For example:
6077 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6080 There are several ways for a thread to disappear, such as a regular
6081 thread exit, but also when you detach from the process with the
6082 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6083 Process}), or if @value{GDBN} loses the remote connection
6084 (@pxref{Remote Debugging}), etc. Note that with some targets,
6085 @value{GDBN} is only able to detect a thread has exited when the user
6086 explictly asks for the thread list with the @code{info threads}
6089 @node Interrupted System Calls
6090 @subsection Interrupted System Calls
6092 @cindex thread breakpoints and system calls
6093 @cindex system calls and thread breakpoints
6094 @cindex premature return from system calls
6095 There is an unfortunate side effect when using @value{GDBN} to debug
6096 multi-threaded programs. If one thread stops for a
6097 breakpoint, or for some other reason, and another thread is blocked in a
6098 system call, then the system call may return prematurely. This is a
6099 consequence of the interaction between multiple threads and the signals
6100 that @value{GDBN} uses to implement breakpoints and other events that
6103 To handle this problem, your program should check the return value of
6104 each system call and react appropriately. This is good programming
6107 For example, do not write code like this:
6113 The call to @code{sleep} will return early if a different thread stops
6114 at a breakpoint or for some other reason.
6116 Instead, write this:
6121 unslept = sleep (unslept);
6124 A system call is allowed to return early, so the system is still
6125 conforming to its specification. But @value{GDBN} does cause your
6126 multi-threaded program to behave differently than it would without
6129 Also, @value{GDBN} uses internal breakpoints in the thread library to
6130 monitor certain events such as thread creation and thread destruction.
6131 When such an event happens, a system call in another thread may return
6132 prematurely, even though your program does not appear to stop.
6135 @subsection Observer Mode
6137 If you want to build on non-stop mode and observe program behavior
6138 without any chance of disruption by @value{GDBN}, you can set
6139 variables to disable all of the debugger's attempts to modify state,
6140 whether by writing memory, inserting breakpoints, etc. These operate
6141 at a low level, intercepting operations from all commands.
6143 When all of these are set to @code{off}, then @value{GDBN} is said to
6144 be @dfn{observer mode}. As a convenience, the variable
6145 @code{observer} can be set to disable these, plus enable non-stop
6148 Note that @value{GDBN} will not prevent you from making nonsensical
6149 combinations of these settings. For instance, if you have enabled
6150 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6151 then breakpoints that work by writing trap instructions into the code
6152 stream will still not be able to be placed.
6157 @item set observer on
6158 @itemx set observer off
6159 When set to @code{on}, this disables all the permission variables
6160 below (except for @code{insert-fast-tracepoints}), plus enables
6161 non-stop debugging. Setting this to @code{off} switches back to
6162 normal debugging, though remaining in non-stop mode.
6165 Show whether observer mode is on or off.
6167 @kindex may-write-registers
6168 @item set may-write-registers on
6169 @itemx set may-write-registers off
6170 This controls whether @value{GDBN} will attempt to alter the values of
6171 registers, such as with assignment expressions in @code{print}, or the
6172 @code{jump} command. It defaults to @code{on}.
6174 @item show may-write-registers
6175 Show the current permission to write registers.
6177 @kindex may-write-memory
6178 @item set may-write-memory on
6179 @itemx set may-write-memory off
6180 This controls whether @value{GDBN} will attempt to alter the contents
6181 of memory, such as with assignment expressions in @code{print}. It
6182 defaults to @code{on}.
6184 @item show may-write-memory
6185 Show the current permission to write memory.
6187 @kindex may-insert-breakpoints
6188 @item set may-insert-breakpoints on
6189 @itemx set may-insert-breakpoints off
6190 This controls whether @value{GDBN} will attempt to insert breakpoints.
6191 This affects all breakpoints, including internal breakpoints defined
6192 by @value{GDBN}. It defaults to @code{on}.
6194 @item show may-insert-breakpoints
6195 Show the current permission to insert breakpoints.
6197 @kindex may-insert-tracepoints
6198 @item set may-insert-tracepoints on
6199 @itemx set may-insert-tracepoints off
6200 This controls whether @value{GDBN} will attempt to insert (regular)
6201 tracepoints at the beginning of a tracing experiment. It affects only
6202 non-fast tracepoints, fast tracepoints being under the control of
6203 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6205 @item show may-insert-tracepoints
6206 Show the current permission to insert tracepoints.
6208 @kindex may-insert-fast-tracepoints
6209 @item set may-insert-fast-tracepoints on
6210 @itemx set may-insert-fast-tracepoints off
6211 This controls whether @value{GDBN} will attempt to insert fast
6212 tracepoints at the beginning of a tracing experiment. It affects only
6213 fast tracepoints, regular (non-fast) tracepoints being under the
6214 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6216 @item show may-insert-fast-tracepoints
6217 Show the current permission to insert fast tracepoints.
6219 @kindex may-interrupt
6220 @item set may-interrupt on
6221 @itemx set may-interrupt off
6222 This controls whether @value{GDBN} will attempt to interrupt or stop
6223 program execution. When this variable is @code{off}, the
6224 @code{interrupt} command will have no effect, nor will
6225 @kbd{Ctrl-c}. It defaults to @code{on}.
6227 @item show may-interrupt
6228 Show the current permission to interrupt or stop the program.
6232 @node Reverse Execution
6233 @chapter Running programs backward
6234 @cindex reverse execution
6235 @cindex running programs backward
6237 When you are debugging a program, it is not unusual to realize that
6238 you have gone too far, and some event of interest has already happened.
6239 If the target environment supports it, @value{GDBN} can allow you to
6240 ``rewind'' the program by running it backward.
6242 A target environment that supports reverse execution should be able
6243 to ``undo'' the changes in machine state that have taken place as the
6244 program was executing normally. Variables, registers etc.@: should
6245 revert to their previous values. Obviously this requires a great
6246 deal of sophistication on the part of the target environment; not
6247 all target environments can support reverse execution.
6249 When a program is executed in reverse, the instructions that
6250 have most recently been executed are ``un-executed'', in reverse
6251 order. The program counter runs backward, following the previous
6252 thread of execution in reverse. As each instruction is ``un-executed'',
6253 the values of memory and/or registers that were changed by that
6254 instruction are reverted to their previous states. After executing
6255 a piece of source code in reverse, all side effects of that code
6256 should be ``undone'', and all variables should be returned to their
6257 prior values@footnote{
6258 Note that some side effects are easier to undo than others. For instance,
6259 memory and registers are relatively easy, but device I/O is hard. Some
6260 targets may be able undo things like device I/O, and some may not.
6262 The contract between @value{GDBN} and the reverse executing target
6263 requires only that the target do something reasonable when
6264 @value{GDBN} tells it to execute backwards, and then report the
6265 results back to @value{GDBN}. Whatever the target reports back to
6266 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6267 assumes that the memory and registers that the target reports are in a
6268 consistant state, but @value{GDBN} accepts whatever it is given.
6271 If you are debugging in a target environment that supports
6272 reverse execution, @value{GDBN} provides the following commands.
6275 @kindex reverse-continue
6276 @kindex rc @r{(@code{reverse-continue})}
6277 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6278 @itemx rc @r{[}@var{ignore-count}@r{]}
6279 Beginning at the point where your program last stopped, start executing
6280 in reverse. Reverse execution will stop for breakpoints and synchronous
6281 exceptions (signals), just like normal execution. Behavior of
6282 asynchronous signals depends on the target environment.
6284 @kindex reverse-step
6285 @kindex rs @r{(@code{step})}
6286 @item reverse-step @r{[}@var{count}@r{]}
6287 Run the program backward until control reaches the start of a
6288 different source line; then stop it, and return control to @value{GDBN}.
6290 Like the @code{step} command, @code{reverse-step} will only stop
6291 at the beginning of a source line. It ``un-executes'' the previously
6292 executed source line. If the previous source line included calls to
6293 debuggable functions, @code{reverse-step} will step (backward) into
6294 the called function, stopping at the beginning of the @emph{last}
6295 statement in the called function (typically a return statement).
6297 Also, as with the @code{step} command, if non-debuggable functions are
6298 called, @code{reverse-step} will run thru them backward without stopping.
6300 @kindex reverse-stepi
6301 @kindex rsi @r{(@code{reverse-stepi})}
6302 @item reverse-stepi @r{[}@var{count}@r{]}
6303 Reverse-execute one machine instruction. Note that the instruction
6304 to be reverse-executed is @emph{not} the one pointed to by the program
6305 counter, but the instruction executed prior to that one. For instance,
6306 if the last instruction was a jump, @code{reverse-stepi} will take you
6307 back from the destination of the jump to the jump instruction itself.
6309 @kindex reverse-next
6310 @kindex rn @r{(@code{reverse-next})}
6311 @item reverse-next @r{[}@var{count}@r{]}
6312 Run backward to the beginning of the previous line executed in
6313 the current (innermost) stack frame. If the line contains function
6314 calls, they will be ``un-executed'' without stopping. Starting from
6315 the first line of a function, @code{reverse-next} will take you back
6316 to the caller of that function, @emph{before} the function was called,
6317 just as the normal @code{next} command would take you from the last
6318 line of a function back to its return to its caller
6319 @footnote{Unless the code is too heavily optimized.}.
6321 @kindex reverse-nexti
6322 @kindex rni @r{(@code{reverse-nexti})}
6323 @item reverse-nexti @r{[}@var{count}@r{]}
6324 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6325 in reverse, except that called functions are ``un-executed'' atomically.
6326 That is, if the previously executed instruction was a return from
6327 another function, @code{reverse-nexti} will continue to execute
6328 in reverse until the call to that function (from the current stack
6331 @kindex reverse-finish
6332 @item reverse-finish
6333 Just as the @code{finish} command takes you to the point where the
6334 current function returns, @code{reverse-finish} takes you to the point
6335 where it was called. Instead of ending up at the end of the current
6336 function invocation, you end up at the beginning.
6338 @kindex set exec-direction
6339 @item set exec-direction
6340 Set the direction of target execution.
6341 @item set exec-direction reverse
6342 @cindex execute forward or backward in time
6343 @value{GDBN} will perform all execution commands in reverse, until the
6344 exec-direction mode is changed to ``forward''. Affected commands include
6345 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6346 command cannot be used in reverse mode.
6347 @item set exec-direction forward
6348 @value{GDBN} will perform all execution commands in the normal fashion.
6349 This is the default.
6353 @node Process Record and Replay
6354 @chapter Recording Inferior's Execution and Replaying It
6355 @cindex process record and replay
6356 @cindex recording inferior's execution and replaying it
6358 On some platforms, @value{GDBN} provides a special @dfn{process record
6359 and replay} target that can record a log of the process execution, and
6360 replay it later with both forward and reverse execution commands.
6363 When this target is in use, if the execution log includes the record
6364 for the next instruction, @value{GDBN} will debug in @dfn{replay
6365 mode}. In the replay mode, the inferior does not really execute code
6366 instructions. Instead, all the events that normally happen during
6367 code execution are taken from the execution log. While code is not
6368 really executed in replay mode, the values of registers (including the
6369 program counter register) and the memory of the inferior are still
6370 changed as they normally would. Their contents are taken from the
6374 If the record for the next instruction is not in the execution log,
6375 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6376 inferior executes normally, and @value{GDBN} records the execution log
6379 The process record and replay target supports reverse execution
6380 (@pxref{Reverse Execution}), even if the platform on which the
6381 inferior runs does not. However, the reverse execution is limited in
6382 this case by the range of the instructions recorded in the execution
6383 log. In other words, reverse execution on platforms that don't
6384 support it directly can only be done in the replay mode.
6386 When debugging in the reverse direction, @value{GDBN} will work in
6387 replay mode as long as the execution log includes the record for the
6388 previous instruction; otherwise, it will work in record mode, if the
6389 platform supports reverse execution, or stop if not.
6391 For architecture environments that support process record and replay,
6392 @value{GDBN} provides the following commands:
6395 @kindex target record
6396 @kindex target record-full
6397 @kindex target record-btrace
6400 @kindex record btrace
6401 @kindex record btrace bts
6402 @kindex record btrace pt
6408 @kindex rec btrace bts
6409 @kindex rec btrace pt
6412 @item record @var{method}
6413 This command starts the process record and replay target. The
6414 recording method can be specified as parameter. Without a parameter
6415 the command uses the @code{full} recording method. The following
6416 recording methods are available:
6420 Full record/replay recording using @value{GDBN}'s software record and
6421 replay implementation. This method allows replaying and reverse
6424 @item btrace @var{format}
6425 Hardware-supported instruction recording. This method does not record
6426 data. Further, the data is collected in a ring buffer so old data will
6427 be overwritten when the buffer is full. It allows limited reverse
6428 execution. Variables and registers are not available during reverse
6431 The recording format can be specified as parameter. Without a parameter
6432 the command chooses the recording format. The following recording
6433 formats are available:
6437 @cindex branch trace store
6438 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6439 this format, the processor stores a from/to record for each executed
6440 branch in the btrace ring buffer.
6443 @cindex Intel(R) Processor Trace
6444 Use the @dfn{Intel(R) Processor Trace} recording format. In this
6445 format, the processor stores the execution trace in a compressed form
6446 that is afterwards decoded by @value{GDBN}.
6448 The trace can be recorded with very low overhead. The compressed
6449 trace format also allows small trace buffers to already contain a big
6450 number of instructions compared to @acronym{BTS}.
6452 Decoding the recorded execution trace, on the other hand, is more
6453 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6454 increased number of instructions to process. You should increase the
6455 buffer-size with care.
6458 Not all recording formats may be available on all processors.
6461 The process record and replay target can only debug a process that is
6462 already running. Therefore, you need first to start the process with
6463 the @kbd{run} or @kbd{start} commands, and then start the recording
6464 with the @kbd{record @var{method}} command.
6466 @cindex displaced stepping, and process record and replay
6467 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6468 will be automatically disabled when process record and replay target
6469 is started. That's because the process record and replay target
6470 doesn't support displaced stepping.
6472 @cindex non-stop mode, and process record and replay
6473 @cindex asynchronous execution, and process record and replay
6474 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6475 the asynchronous execution mode (@pxref{Background Execution}), not
6476 all recording methods are available. The @code{full} recording method
6477 does not support these two modes.
6482 Stop the process record and replay target. When process record and
6483 replay target stops, the entire execution log will be deleted and the
6484 inferior will either be terminated, or will remain in its final state.
6486 When you stop the process record and replay target in record mode (at
6487 the end of the execution log), the inferior will be stopped at the
6488 next instruction that would have been recorded. In other words, if
6489 you record for a while and then stop recording, the inferior process
6490 will be left in the same state as if the recording never happened.
6492 On the other hand, if the process record and replay target is stopped
6493 while in replay mode (that is, not at the end of the execution log,
6494 but at some earlier point), the inferior process will become ``live''
6495 at that earlier state, and it will then be possible to continue the
6496 usual ``live'' debugging of the process from that state.
6498 When the inferior process exits, or @value{GDBN} detaches from it,
6499 process record and replay target will automatically stop itself.
6503 Go to a specific location in the execution log. There are several
6504 ways to specify the location to go to:
6507 @item record goto begin
6508 @itemx record goto start
6509 Go to the beginning of the execution log.
6511 @item record goto end
6512 Go to the end of the execution log.
6514 @item record goto @var{n}
6515 Go to instruction number @var{n} in the execution log.
6519 @item record save @var{filename}
6520 Save the execution log to a file @file{@var{filename}}.
6521 Default filename is @file{gdb_record.@var{process_id}}, where
6522 @var{process_id} is the process ID of the inferior.
6524 This command may not be available for all recording methods.
6526 @kindex record restore
6527 @item record restore @var{filename}
6528 Restore the execution log from a file @file{@var{filename}}.
6529 File must have been created with @code{record save}.
6531 @kindex set record full
6532 @item set record full insn-number-max @var{limit}
6533 @itemx set record full insn-number-max unlimited
6534 Set the limit of instructions to be recorded for the @code{full}
6535 recording method. Default value is 200000.
6537 If @var{limit} is a positive number, then @value{GDBN} will start
6538 deleting instructions from the log once the number of the record
6539 instructions becomes greater than @var{limit}. For every new recorded
6540 instruction, @value{GDBN} will delete the earliest recorded
6541 instruction to keep the number of recorded instructions at the limit.
6542 (Since deleting recorded instructions loses information, @value{GDBN}
6543 lets you control what happens when the limit is reached, by means of
6544 the @code{stop-at-limit} option, described below.)
6546 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6547 delete recorded instructions from the execution log. The number of
6548 recorded instructions is limited only by the available memory.
6550 @kindex show record full
6551 @item show record full insn-number-max
6552 Show the limit of instructions to be recorded with the @code{full}
6555 @item set record full stop-at-limit
6556 Control the behavior of the @code{full} recording method when the
6557 number of recorded instructions reaches the limit. If ON (the
6558 default), @value{GDBN} will stop when the limit is reached for the
6559 first time and ask you whether you want to stop the inferior or
6560 continue running it and recording the execution log. If you decide
6561 to continue recording, each new recorded instruction will cause the
6562 oldest one to be deleted.
6564 If this option is OFF, @value{GDBN} will automatically delete the
6565 oldest record to make room for each new one, without asking.
6567 @item show record full stop-at-limit
6568 Show the current setting of @code{stop-at-limit}.
6570 @item set record full memory-query
6571 Control the behavior when @value{GDBN} is unable to record memory
6572 changes caused by an instruction for the @code{full} recording method.
6573 If ON, @value{GDBN} will query whether to stop the inferior in that
6576 If this option is OFF (the default), @value{GDBN} will automatically
6577 ignore the effect of such instructions on memory. Later, when
6578 @value{GDBN} replays this execution log, it will mark the log of this
6579 instruction as not accessible, and it will not affect the replay
6582 @item show record full memory-query
6583 Show the current setting of @code{memory-query}.
6585 @kindex set record btrace
6586 The @code{btrace} record target does not trace data. As a
6587 convenience, when replaying, @value{GDBN} reads read-only memory off
6588 the live program directly, assuming that the addresses of the
6589 read-only areas don't change. This for example makes it possible to
6590 disassemble code while replaying, but not to print variables.
6591 In some cases, being able to inspect variables might be useful.
6592 You can use the following command for that:
6594 @item set record btrace replay-memory-access
6595 Control the behavior of the @code{btrace} recording method when
6596 accessing memory during replay. If @code{read-only} (the default),
6597 @value{GDBN} will only allow accesses to read-only memory.
6598 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6599 and to read-write memory. Beware that the accessed memory corresponds
6600 to the live target and not necessarily to the current replay
6603 @kindex show record btrace
6604 @item show record btrace replay-memory-access
6605 Show the current setting of @code{replay-memory-access}.
6607 @kindex set record btrace bts
6608 @item set record btrace bts buffer-size @var{size}
6609 @itemx set record btrace bts buffer-size unlimited
6610 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6611 format. Default is 64KB.
6613 If @var{size} is a positive number, then @value{GDBN} will try to
6614 allocate a buffer of at least @var{size} bytes for each new thread
6615 that uses the btrace recording method and the @acronym{BTS} format.
6616 The actually obtained buffer size may differ from the requested
6617 @var{size}. Use the @code{info record} command to see the actual
6618 buffer size for each thread that uses the btrace recording method and
6619 the @acronym{BTS} format.
6621 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6622 allocate a buffer of 4MB.
6624 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6625 also need longer to process the branch trace data before it can be used.
6627 @item show record btrace bts buffer-size @var{size}
6628 Show the current setting of the requested ring buffer size for branch
6629 tracing in @acronym{BTS} format.
6631 @kindex set record btrace pt
6632 @item set record btrace pt buffer-size @var{size}
6633 @itemx set record btrace pt buffer-size unlimited
6634 Set the requested ring buffer size for branch tracing in Intel(R)
6635 Processor Trace format. Default is 16KB.
6637 If @var{size} is a positive number, then @value{GDBN} will try to
6638 allocate a buffer of at least @var{size} bytes for each new thread
6639 that uses the btrace recording method and the Intel(R) Processor Trace
6640 format. The actually obtained buffer size may differ from the
6641 requested @var{size}. Use the @code{info record} command to see the
6642 actual buffer size for each thread.
6644 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6645 allocate a buffer of 4MB.
6647 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6648 also need longer to process the branch trace data before it can be used.
6650 @item show record btrace pt buffer-size @var{size}
6651 Show the current setting of the requested ring buffer size for branch
6652 tracing in Intel(R) Processor Trace format.
6656 Show various statistics about the recording depending on the recording
6661 For the @code{full} recording method, it shows the state of process
6662 record and its in-memory execution log buffer, including:
6666 Whether in record mode or replay mode.
6668 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6670 Highest recorded instruction number.
6672 Current instruction about to be replayed (if in replay mode).
6674 Number of instructions contained in the execution log.
6676 Maximum number of instructions that may be contained in the execution log.
6680 For the @code{btrace} recording method, it shows:
6686 Number of instructions that have been recorded.
6688 Number of blocks of sequential control-flow formed by the recorded
6691 Whether in record mode or replay mode.
6694 For the @code{bts} recording format, it also shows:
6697 Size of the perf ring buffer.
6700 For the @code{pt} recording format, it also shows:
6703 Size of the perf ring buffer.
6707 @kindex record delete
6710 When record target runs in replay mode (``in the past''), delete the
6711 subsequent execution log and begin to record a new execution log starting
6712 from the current address. This means you will abandon the previously
6713 recorded ``future'' and begin recording a new ``future''.
6715 @kindex record instruction-history
6716 @kindex rec instruction-history
6717 @item record instruction-history
6718 Disassembles instructions from the recorded execution log. By
6719 default, ten instructions are disassembled. This can be changed using
6720 the @code{set record instruction-history-size} command. Instructions
6721 are printed in execution order.
6723 It can also print mixed source+disassembly if you specify the the
6724 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
6725 as well as in symbolic form by specifying the @code{/r} modifier.
6727 The current position marker is printed for the instruction at the
6728 current program counter value. This instruction can appear multiple
6729 times in the trace and the current position marker will be printed
6730 every time. To omit the current position marker, specify the
6733 To better align the printed instructions when the trace contains
6734 instructions from more than one function, the function name may be
6735 omitted by specifying the @code{/f} modifier.
6737 Speculatively executed instructions are prefixed with @samp{?}. This
6738 feature is not available for all recording formats.
6740 There are several ways to specify what part of the execution log to
6744 @item record instruction-history @var{insn}
6745 Disassembles ten instructions starting from instruction number
6748 @item record instruction-history @var{insn}, +/-@var{n}
6749 Disassembles @var{n} instructions around instruction number
6750 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6751 @var{n} instructions after instruction number @var{insn}. If
6752 @var{n} is preceded with @code{-}, disassembles @var{n}
6753 instructions before instruction number @var{insn}.
6755 @item record instruction-history
6756 Disassembles ten more instructions after the last disassembly.
6758 @item record instruction-history -
6759 Disassembles ten more instructions before the last disassembly.
6761 @item record instruction-history @var{begin}, @var{end}
6762 Disassembles instructions beginning with instruction number
6763 @var{begin} until instruction number @var{end}. The instruction
6764 number @var{end} is included.
6767 This command may not be available for all recording methods.
6770 @item set record instruction-history-size @var{size}
6771 @itemx set record instruction-history-size unlimited
6772 Define how many instructions to disassemble in the @code{record
6773 instruction-history} command. The default value is 10.
6774 A @var{size} of @code{unlimited} means unlimited instructions.
6777 @item show record instruction-history-size
6778 Show how many instructions to disassemble in the @code{record
6779 instruction-history} command.
6781 @kindex record function-call-history
6782 @kindex rec function-call-history
6783 @item record function-call-history
6784 Prints the execution history at function granularity. It prints one
6785 line for each sequence of instructions that belong to the same
6786 function giving the name of that function, the source lines
6787 for this instruction sequence (if the @code{/l} modifier is
6788 specified), and the instructions numbers that form the sequence (if
6789 the @code{/i} modifier is specified). The function names are indented
6790 to reflect the call stack depth if the @code{/c} modifier is
6791 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6795 (@value{GDBP}) @b{list 1, 10}
6806 (@value{GDBP}) @b{record function-call-history /ilc}
6807 1 bar inst 1,4 at foo.c:6,8
6808 2 foo inst 5,10 at foo.c:2,3
6809 3 bar inst 11,13 at foo.c:9,10
6812 By default, ten lines are printed. This can be changed using the
6813 @code{set record function-call-history-size} command. Functions are
6814 printed in execution order. There are several ways to specify what
6818 @item record function-call-history @var{func}
6819 Prints ten functions starting from function number @var{func}.
6821 @item record function-call-history @var{func}, +/-@var{n}
6822 Prints @var{n} functions around function number @var{func}. If
6823 @var{n} is preceded with @code{+}, prints @var{n} functions after
6824 function number @var{func}. If @var{n} is preceded with @code{-},
6825 prints @var{n} functions before function number @var{func}.
6827 @item record function-call-history
6828 Prints ten more functions after the last ten-line print.
6830 @item record function-call-history -
6831 Prints ten more functions before the last ten-line print.
6833 @item record function-call-history @var{begin}, @var{end}
6834 Prints functions beginning with function number @var{begin} until
6835 function number @var{end}. The function number @var{end} is included.
6838 This command may not be available for all recording methods.
6840 @item set record function-call-history-size @var{size}
6841 @itemx set record function-call-history-size unlimited
6842 Define how many lines to print in the
6843 @code{record function-call-history} command. The default value is 10.
6844 A size of @code{unlimited} means unlimited lines.
6846 @item show record function-call-history-size
6847 Show how many lines to print in the
6848 @code{record function-call-history} command.
6853 @chapter Examining the Stack
6855 When your program has stopped, the first thing you need to know is where it
6856 stopped and how it got there.
6859 Each time your program performs a function call, information about the call
6861 That information includes the location of the call in your program,
6862 the arguments of the call,
6863 and the local variables of the function being called.
6864 The information is saved in a block of data called a @dfn{stack frame}.
6865 The stack frames are allocated in a region of memory called the @dfn{call
6868 When your program stops, the @value{GDBN} commands for examining the
6869 stack allow you to see all of this information.
6871 @cindex selected frame
6872 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6873 @value{GDBN} commands refer implicitly to the selected frame. In
6874 particular, whenever you ask @value{GDBN} for the value of a variable in
6875 your program, the value is found in the selected frame. There are
6876 special @value{GDBN} commands to select whichever frame you are
6877 interested in. @xref{Selection, ,Selecting a Frame}.
6879 When your program stops, @value{GDBN} automatically selects the
6880 currently executing frame and describes it briefly, similar to the
6881 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6884 * Frames:: Stack frames
6885 * Backtrace:: Backtraces
6886 * Selection:: Selecting a frame
6887 * Frame Info:: Information on a frame
6888 * Frame Filter Management:: Managing frame filters
6893 @section Stack Frames
6895 @cindex frame, definition
6897 The call stack is divided up into contiguous pieces called @dfn{stack
6898 frames}, or @dfn{frames} for short; each frame is the data associated
6899 with one call to one function. The frame contains the arguments given
6900 to the function, the function's local variables, and the address at
6901 which the function is executing.
6903 @cindex initial frame
6904 @cindex outermost frame
6905 @cindex innermost frame
6906 When your program is started, the stack has only one frame, that of the
6907 function @code{main}. This is called the @dfn{initial} frame or the
6908 @dfn{outermost} frame. Each time a function is called, a new frame is
6909 made. Each time a function returns, the frame for that function invocation
6910 is eliminated. If a function is recursive, there can be many frames for
6911 the same function. The frame for the function in which execution is
6912 actually occurring is called the @dfn{innermost} frame. This is the most
6913 recently created of all the stack frames that still exist.
6915 @cindex frame pointer
6916 Inside your program, stack frames are identified by their addresses. A
6917 stack frame consists of many bytes, each of which has its own address; each
6918 kind of computer has a convention for choosing one byte whose
6919 address serves as the address of the frame. Usually this address is kept
6920 in a register called the @dfn{frame pointer register}
6921 (@pxref{Registers, $fp}) while execution is going on in that frame.
6923 @cindex frame number
6924 @value{GDBN} assigns numbers to all existing stack frames, starting with
6925 zero for the innermost frame, one for the frame that called it,
6926 and so on upward. These numbers do not really exist in your program;
6927 they are assigned by @value{GDBN} to give you a way of designating stack
6928 frames in @value{GDBN} commands.
6930 @c The -fomit-frame-pointer below perennially causes hbox overflow
6931 @c underflow problems.
6932 @cindex frameless execution
6933 Some compilers provide a way to compile functions so that they operate
6934 without stack frames. (For example, the @value{NGCC} option
6936 @samp{-fomit-frame-pointer}
6938 generates functions without a frame.)
6939 This is occasionally done with heavily used library functions to save
6940 the frame setup time. @value{GDBN} has limited facilities for dealing
6941 with these function invocations. If the innermost function invocation
6942 has no stack frame, @value{GDBN} nevertheless regards it as though
6943 it had a separate frame, which is numbered zero as usual, allowing
6944 correct tracing of the function call chain. However, @value{GDBN} has
6945 no provision for frameless functions elsewhere in the stack.
6951 @cindex call stack traces
6952 A backtrace is a summary of how your program got where it is. It shows one
6953 line per frame, for many frames, starting with the currently executing
6954 frame (frame zero), followed by its caller (frame one), and on up the
6957 @anchor{backtrace-command}
6960 @kindex bt @r{(@code{backtrace})}
6963 Print a backtrace of the entire stack: one line per frame for all
6964 frames in the stack.
6966 You can stop the backtrace at any time by typing the system interrupt
6967 character, normally @kbd{Ctrl-c}.
6969 @item backtrace @var{n}
6971 Similar, but print only the innermost @var{n} frames.
6973 @item backtrace -@var{n}
6975 Similar, but print only the outermost @var{n} frames.
6977 @item backtrace full
6979 @itemx bt full @var{n}
6980 @itemx bt full -@var{n}
6981 Print the values of the local variables also. As described above,
6982 @var{n} specifies the number of frames to print.
6984 @item backtrace no-filters
6985 @itemx bt no-filters
6986 @itemx bt no-filters @var{n}
6987 @itemx bt no-filters -@var{n}
6988 @itemx bt no-filters full
6989 @itemx bt no-filters full @var{n}
6990 @itemx bt no-filters full -@var{n}
6991 Do not run Python frame filters on this backtrace. @xref{Frame
6992 Filter API}, for more information. Additionally use @ref{disable
6993 frame-filter all} to turn off all frame filters. This is only
6994 relevant when @value{GDBN} has been configured with @code{Python}
7000 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7001 are additional aliases for @code{backtrace}.
7003 @cindex multiple threads, backtrace
7004 In a multi-threaded program, @value{GDBN} by default shows the
7005 backtrace only for the current thread. To display the backtrace for
7006 several or all of the threads, use the command @code{thread apply}
7007 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7008 apply all backtrace}, @value{GDBN} will display the backtrace for all
7009 the threads; this is handy when you debug a core dump of a
7010 multi-threaded program.
7012 Each line in the backtrace shows the frame number and the function name.
7013 The program counter value is also shown---unless you use @code{set
7014 print address off}. The backtrace also shows the source file name and
7015 line number, as well as the arguments to the function. The program
7016 counter value is omitted if it is at the beginning of the code for that
7019 Here is an example of a backtrace. It was made with the command
7020 @samp{bt 3}, so it shows the innermost three frames.
7024 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7026 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7027 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7029 (More stack frames follow...)
7034 The display for frame zero does not begin with a program counter
7035 value, indicating that your program has stopped at the beginning of the
7036 code for line @code{993} of @code{builtin.c}.
7039 The value of parameter @code{data} in frame 1 has been replaced by
7040 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7041 only if it is a scalar (integer, pointer, enumeration, etc). See command
7042 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7043 on how to configure the way function parameter values are printed.
7045 @cindex optimized out, in backtrace
7046 @cindex function call arguments, optimized out
7047 If your program was compiled with optimizations, some compilers will
7048 optimize away arguments passed to functions if those arguments are
7049 never used after the call. Such optimizations generate code that
7050 passes arguments through registers, but doesn't store those arguments
7051 in the stack frame. @value{GDBN} has no way of displaying such
7052 arguments in stack frames other than the innermost one. Here's what
7053 such a backtrace might look like:
7057 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7059 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7060 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7062 (More stack frames follow...)
7067 The values of arguments that were not saved in their stack frames are
7068 shown as @samp{<optimized out>}.
7070 If you need to display the values of such optimized-out arguments,
7071 either deduce that from other variables whose values depend on the one
7072 you are interested in, or recompile without optimizations.
7074 @cindex backtrace beyond @code{main} function
7075 @cindex program entry point
7076 @cindex startup code, and backtrace
7077 Most programs have a standard user entry point---a place where system
7078 libraries and startup code transition into user code. For C this is
7079 @code{main}@footnote{
7080 Note that embedded programs (the so-called ``free-standing''
7081 environment) are not required to have a @code{main} function as the
7082 entry point. They could even have multiple entry points.}.
7083 When @value{GDBN} finds the entry function in a backtrace
7084 it will terminate the backtrace, to avoid tracing into highly
7085 system-specific (and generally uninteresting) code.
7087 If you need to examine the startup code, or limit the number of levels
7088 in a backtrace, you can change this behavior:
7091 @item set backtrace past-main
7092 @itemx set backtrace past-main on
7093 @kindex set backtrace
7094 Backtraces will continue past the user entry point.
7096 @item set backtrace past-main off
7097 Backtraces will stop when they encounter the user entry point. This is the
7100 @item show backtrace past-main
7101 @kindex show backtrace
7102 Display the current user entry point backtrace policy.
7104 @item set backtrace past-entry
7105 @itemx set backtrace past-entry on
7106 Backtraces will continue past the internal entry point of an application.
7107 This entry point is encoded by the linker when the application is built,
7108 and is likely before the user entry point @code{main} (or equivalent) is called.
7110 @item set backtrace past-entry off
7111 Backtraces will stop when they encounter the internal entry point of an
7112 application. This is the default.
7114 @item show backtrace past-entry
7115 Display the current internal entry point backtrace policy.
7117 @item set backtrace limit @var{n}
7118 @itemx set backtrace limit 0
7119 @itemx set backtrace limit unlimited
7120 @cindex backtrace limit
7121 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7122 or zero means unlimited levels.
7124 @item show backtrace limit
7125 Display the current limit on backtrace levels.
7128 You can control how file names are displayed.
7131 @item set filename-display
7132 @itemx set filename-display relative
7133 @cindex filename-display
7134 Display file names relative to the compilation directory. This is the default.
7136 @item set filename-display basename
7137 Display only basename of a filename.
7139 @item set filename-display absolute
7140 Display an absolute filename.
7142 @item show filename-display
7143 Show the current way to display filenames.
7147 @section Selecting a Frame
7149 Most commands for examining the stack and other data in your program work on
7150 whichever stack frame is selected at the moment. Here are the commands for
7151 selecting a stack frame; all of them finish by printing a brief description
7152 of the stack frame just selected.
7155 @kindex frame@r{, selecting}
7156 @kindex f @r{(@code{frame})}
7159 Select frame number @var{n}. Recall that frame zero is the innermost
7160 (currently executing) frame, frame one is the frame that called the
7161 innermost one, and so on. The highest-numbered frame is the one for
7164 @item frame @var{stack-addr} [ @var{pc-addr} ]
7165 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7166 Select the frame at address @var{stack-addr}. This is useful mainly if the
7167 chaining of stack frames has been damaged by a bug, making it
7168 impossible for @value{GDBN} to assign numbers properly to all frames. In
7169 addition, this can be useful when your program has multiple stacks and
7170 switches between them. The optional @var{pc-addr} can also be given to
7171 specify the value of PC for the stack frame.
7175 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7176 numbers @var{n}, this advances toward the outermost frame, to higher
7177 frame numbers, to frames that have existed longer.
7180 @kindex do @r{(@code{down})}
7182 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7183 positive numbers @var{n}, this advances toward the innermost frame, to
7184 lower frame numbers, to frames that were created more recently.
7185 You may abbreviate @code{down} as @code{do}.
7188 All of these commands end by printing two lines of output describing the
7189 frame. The first line shows the frame number, the function name, the
7190 arguments, and the source file and line number of execution in that
7191 frame. The second line shows the text of that source line.
7199 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7201 10 read_input_file (argv[i]);
7205 After such a printout, the @code{list} command with no arguments
7206 prints ten lines centered on the point of execution in the frame.
7207 You can also edit the program at the point of execution with your favorite
7208 editing program by typing @code{edit}.
7209 @xref{List, ,Printing Source Lines},
7213 @kindex select-frame
7215 The @code{select-frame} command is a variant of @code{frame} that does
7216 not display the new frame after selecting it. This command is
7217 intended primarily for use in @value{GDBN} command scripts, where the
7218 output might be unnecessary and distracting.
7220 @kindex down-silently
7222 @item up-silently @var{n}
7223 @itemx down-silently @var{n}
7224 These two commands are variants of @code{up} and @code{down},
7225 respectively; they differ in that they do their work silently, without
7226 causing display of the new frame. They are intended primarily for use
7227 in @value{GDBN} command scripts, where the output might be unnecessary and
7232 @section Information About a Frame
7234 There are several other commands to print information about the selected
7240 When used without any argument, this command does not change which
7241 frame is selected, but prints a brief description of the currently
7242 selected stack frame. It can be abbreviated @code{f}. With an
7243 argument, this command is used to select a stack frame.
7244 @xref{Selection, ,Selecting a Frame}.
7247 @kindex info f @r{(@code{info frame})}
7250 This command prints a verbose description of the selected stack frame,
7255 the address of the frame
7257 the address of the next frame down (called by this frame)
7259 the address of the next frame up (caller of this frame)
7261 the language in which the source code corresponding to this frame is written
7263 the address of the frame's arguments
7265 the address of the frame's local variables
7267 the program counter saved in it (the address of execution in the caller frame)
7269 which registers were saved in the frame
7272 @noindent The verbose description is useful when
7273 something has gone wrong that has made the stack format fail to fit
7274 the usual conventions.
7276 @item info frame @var{addr}
7277 @itemx info f @var{addr}
7278 Print a verbose description of the frame at address @var{addr}, without
7279 selecting that frame. The selected frame remains unchanged by this
7280 command. This requires the same kind of address (more than one for some
7281 architectures) that you specify in the @code{frame} command.
7282 @xref{Selection, ,Selecting a Frame}.
7286 Print the arguments of the selected frame, each on a separate line.
7290 Print the local variables of the selected frame, each on a separate
7291 line. These are all variables (declared either static or automatic)
7292 accessible at the point of execution of the selected frame.
7296 @node Frame Filter Management
7297 @section Management of Frame Filters.
7298 @cindex managing frame filters
7300 Frame filters are Python based utilities to manage and decorate the
7301 output of frames. @xref{Frame Filter API}, for further information.
7303 Managing frame filters is performed by several commands available
7304 within @value{GDBN}, detailed here.
7307 @kindex info frame-filter
7308 @item info frame-filter
7309 Print a list of installed frame filters from all dictionaries, showing
7310 their name, priority and enabled status.
7312 @kindex disable frame-filter
7313 @anchor{disable frame-filter all}
7314 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7315 Disable a frame filter in the dictionary matching
7316 @var{filter-dictionary} and @var{filter-name}. The
7317 @var{filter-dictionary} may be @code{all}, @code{global},
7318 @code{progspace}, or the name of the object file where the frame filter
7319 dictionary resides. When @code{all} is specified, all frame filters
7320 across all dictionaries are disabled. The @var{filter-name} is the name
7321 of the frame filter and is used when @code{all} is not the option for
7322 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7323 may be enabled again later.
7325 @kindex enable frame-filter
7326 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7327 Enable a frame filter in the dictionary matching
7328 @var{filter-dictionary} and @var{filter-name}. The
7329 @var{filter-dictionary} may be @code{all}, @code{global},
7330 @code{progspace} or the name of the object file where the frame filter
7331 dictionary resides. When @code{all} is specified, all frame filters across
7332 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7333 filter and is used when @code{all} is not the option for
7334 @var{filter-dictionary}.
7339 (gdb) info frame-filter
7341 global frame-filters:
7342 Priority Enabled Name
7343 1000 No PrimaryFunctionFilter
7346 progspace /build/test frame-filters:
7347 Priority Enabled Name
7348 100 Yes ProgspaceFilter
7350 objfile /build/test frame-filters:
7351 Priority Enabled Name
7352 999 Yes BuildProgra Filter
7354 (gdb) disable frame-filter /build/test BuildProgramFilter
7355 (gdb) info frame-filter
7357 global frame-filters:
7358 Priority Enabled Name
7359 1000 No PrimaryFunctionFilter
7362 progspace /build/test frame-filters:
7363 Priority Enabled Name
7364 100 Yes ProgspaceFilter
7366 objfile /build/test frame-filters:
7367 Priority Enabled Name
7368 999 No BuildProgramFilter
7370 (gdb) enable frame-filter global PrimaryFunctionFilter
7371 (gdb) info frame-filter
7373 global frame-filters:
7374 Priority Enabled Name
7375 1000 Yes PrimaryFunctionFilter
7378 progspace /build/test frame-filters:
7379 Priority Enabled Name
7380 100 Yes ProgspaceFilter
7382 objfile /build/test frame-filters:
7383 Priority Enabled Name
7384 999 No BuildProgramFilter
7387 @kindex set frame-filter priority
7388 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7389 Set the @var{priority} of a frame filter in the dictionary matching
7390 @var{filter-dictionary}, and the frame filter name matching
7391 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7392 @code{progspace} or the name of the object file where the frame filter
7393 dictionary resides. The @var{priority} is an integer.
7395 @kindex show frame-filter priority
7396 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7397 Show the @var{priority} of a frame filter in the dictionary matching
7398 @var{filter-dictionary}, and the frame filter name matching
7399 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7400 @code{progspace} or the name of the object file where the frame filter
7406 (gdb) info frame-filter
7408 global frame-filters:
7409 Priority Enabled Name
7410 1000 Yes PrimaryFunctionFilter
7413 progspace /build/test frame-filters:
7414 Priority Enabled Name
7415 100 Yes ProgspaceFilter
7417 objfile /build/test frame-filters:
7418 Priority Enabled Name
7419 999 No BuildProgramFilter
7421 (gdb) set frame-filter priority global Reverse 50
7422 (gdb) info frame-filter
7424 global frame-filters:
7425 Priority Enabled Name
7426 1000 Yes PrimaryFunctionFilter
7429 progspace /build/test frame-filters:
7430 Priority Enabled Name
7431 100 Yes ProgspaceFilter
7433 objfile /build/test frame-filters:
7434 Priority Enabled Name
7435 999 No BuildProgramFilter
7440 @chapter Examining Source Files
7442 @value{GDBN} can print parts of your program's source, since the debugging
7443 information recorded in the program tells @value{GDBN} what source files were
7444 used to build it. When your program stops, @value{GDBN} spontaneously prints
7445 the line where it stopped. Likewise, when you select a stack frame
7446 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7447 execution in that frame has stopped. You can print other portions of
7448 source files by explicit command.
7450 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7451 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7452 @value{GDBN} under @sc{gnu} Emacs}.
7455 * List:: Printing source lines
7456 * Specify Location:: How to specify code locations
7457 * Edit:: Editing source files
7458 * Search:: Searching source files
7459 * Source Path:: Specifying source directories
7460 * Machine Code:: Source and machine code
7464 @section Printing Source Lines
7467 @kindex l @r{(@code{list})}
7468 To print lines from a source file, use the @code{list} command
7469 (abbreviated @code{l}). By default, ten lines are printed.
7470 There are several ways to specify what part of the file you want to
7471 print; see @ref{Specify Location}, for the full list.
7473 Here are the forms of the @code{list} command most commonly used:
7476 @item list @var{linenum}
7477 Print lines centered around line number @var{linenum} in the
7478 current source file.
7480 @item list @var{function}
7481 Print lines centered around the beginning of function
7485 Print more lines. If the last lines printed were printed with a
7486 @code{list} command, this prints lines following the last lines
7487 printed; however, if the last line printed was a solitary line printed
7488 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7489 Stack}), this prints lines centered around that line.
7492 Print lines just before the lines last printed.
7495 @cindex @code{list}, how many lines to display
7496 By default, @value{GDBN} prints ten source lines with any of these forms of
7497 the @code{list} command. You can change this using @code{set listsize}:
7500 @kindex set listsize
7501 @item set listsize @var{count}
7502 @itemx set listsize unlimited
7503 Make the @code{list} command display @var{count} source lines (unless
7504 the @code{list} argument explicitly specifies some other number).
7505 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7507 @kindex show listsize
7509 Display the number of lines that @code{list} prints.
7512 Repeating a @code{list} command with @key{RET} discards the argument,
7513 so it is equivalent to typing just @code{list}. This is more useful
7514 than listing the same lines again. An exception is made for an
7515 argument of @samp{-}; that argument is preserved in repetition so that
7516 each repetition moves up in the source file.
7518 In general, the @code{list} command expects you to supply zero, one or two
7519 @dfn{locations}. Locations specify source lines; there are several ways
7520 of writing them (@pxref{Specify Location}), but the effect is always
7521 to specify some source line.
7523 Here is a complete description of the possible arguments for @code{list}:
7526 @item list @var{location}
7527 Print lines centered around the line specified by @var{location}.
7529 @item list @var{first},@var{last}
7530 Print lines from @var{first} to @var{last}. Both arguments are
7531 locations. When a @code{list} command has two locations, and the
7532 source file of the second location is omitted, this refers to
7533 the same source file as the first location.
7535 @item list ,@var{last}
7536 Print lines ending with @var{last}.
7538 @item list @var{first},
7539 Print lines starting with @var{first}.
7542 Print lines just after the lines last printed.
7545 Print lines just before the lines last printed.
7548 As described in the preceding table.
7551 @node Specify Location
7552 @section Specifying a Location
7553 @cindex specifying location
7555 @cindex source location
7558 * Linespec Locations:: Linespec locations
7559 * Explicit Locations:: Explicit locations
7560 * Address Locations:: Address locations
7563 Several @value{GDBN} commands accept arguments that specify a location
7564 of your program's code. Since @value{GDBN} is a source-level
7565 debugger, a location usually specifies some line in the source code.
7566 Locations may be specified using three different formats:
7567 linespec locations, explicit locations, or address locations.
7569 @node Linespec Locations
7570 @subsection Linespec Locations
7571 @cindex linespec locations
7573 A @dfn{linespec} is a colon-separated list of source location parameters such
7574 as file name, function name, etc. Here are all the different ways of
7575 specifying a linespec:
7579 Specifies the line number @var{linenum} of the current source file.
7582 @itemx +@var{offset}
7583 Specifies the line @var{offset} lines before or after the @dfn{current
7584 line}. For the @code{list} command, the current line is the last one
7585 printed; for the breakpoint commands, this is the line at which
7586 execution stopped in the currently selected @dfn{stack frame}
7587 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7588 used as the second of the two linespecs in a @code{list} command,
7589 this specifies the line @var{offset} lines up or down from the first
7592 @item @var{filename}:@var{linenum}
7593 Specifies the line @var{linenum} in the source file @var{filename}.
7594 If @var{filename} is a relative file name, then it will match any
7595 source file name with the same trailing components. For example, if
7596 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7597 name of @file{/build/trunk/gcc/expr.c}, but not
7598 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7600 @item @var{function}
7601 Specifies the line that begins the body of the function @var{function}.
7602 For example, in C, this is the line with the open brace.
7604 @item @var{function}:@var{label}
7605 Specifies the line where @var{label} appears in @var{function}.
7607 @item @var{filename}:@var{function}
7608 Specifies the line that begins the body of the function @var{function}
7609 in the file @var{filename}. You only need the file name with a
7610 function name to avoid ambiguity when there are identically named
7611 functions in different source files.
7614 Specifies the line at which the label named @var{label} appears
7615 in the function corresponding to the currently selected stack frame.
7616 If there is no current selected stack frame (for instance, if the inferior
7617 is not running), then @value{GDBN} will not search for a label.
7619 @cindex breakpoint at static probe point
7620 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7621 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7622 applications to embed static probes. @xref{Static Probe Points}, for more
7623 information on finding and using static probes. This form of linespec
7624 specifies the location of such a static probe.
7626 If @var{objfile} is given, only probes coming from that shared library
7627 or executable matching @var{objfile} as a regular expression are considered.
7628 If @var{provider} is given, then only probes from that provider are considered.
7629 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7630 each one of those probes.
7633 @node Explicit Locations
7634 @subsection Explicit Locations
7635 @cindex explicit locations
7637 @dfn{Explicit locations} allow the user to directly specify the source
7638 location's parameters using option-value pairs.
7640 Explicit locations are useful when several functions, labels, or
7641 file names have the same name (base name for files) in the program's
7642 sources. In these cases, explicit locations point to the source
7643 line you meant more accurately and unambiguously. Also, using
7644 explicit locations might be faster in large programs.
7646 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7647 defined in the file named @file{foo} or the label @code{bar} in a function
7648 named @code{foo}. @value{GDBN} must search either the file system or
7649 the symbol table to know.
7651 The list of valid explicit location options is summarized in the
7655 @item -source @var{filename}
7656 The value specifies the source file name. To differentiate between
7657 files with the same base name, prepend as many directories as is necessary
7658 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7659 @value{GDBN} will use the first file it finds with the given base
7660 name. This option requires the use of either @code{-function} or @code{-line}.
7662 @item -function @var{function}
7663 The value specifies the name of a function. Operations
7664 on function locations unmodified by other options (such as @code{-label}
7665 or @code{-line}) refer to the line that begins the body of the function.
7666 In C, for example, this is the line with the open brace.
7668 @item -label @var{label}
7669 The value specifies the name of a label. When the function
7670 name is not specified, the label is searched in the function of the currently
7671 selected stack frame.
7673 @item -line @var{number}
7674 The value specifies a line offset for the location. The offset may either
7675 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7676 the command. When specified without any other options, the line offset is
7677 relative to the current line.
7680 Explicit location options may be abbreviated by omitting any non-unique
7681 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7683 @node Address Locations
7684 @subsection Address Locations
7685 @cindex address locations
7687 @dfn{Address locations} indicate a specific program address. They have
7688 the generalized form *@var{address}.
7690 For line-oriented commands, such as @code{list} and @code{edit}, this
7691 specifies a source line that contains @var{address}. For @code{break} and
7692 other breakpoint-oriented commands, this can be used to set breakpoints in
7693 parts of your program which do not have debugging information or
7696 Here @var{address} may be any expression valid in the current working
7697 language (@pxref{Languages, working language}) that specifies a code
7698 address. In addition, as a convenience, @value{GDBN} extends the
7699 semantics of expressions used in locations to cover several situations
7700 that frequently occur during debugging. Here are the various forms
7704 @item @var{expression}
7705 Any expression valid in the current working language.
7707 @item @var{funcaddr}
7708 An address of a function or procedure derived from its name. In C,
7709 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7710 simply the function's name @var{function} (and actually a special case
7711 of a valid expression). In Pascal and Modula-2, this is
7712 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7713 (although the Pascal form also works).
7715 This form specifies the address of the function's first instruction,
7716 before the stack frame and arguments have been set up.
7718 @item '@var{filename}':@var{funcaddr}
7719 Like @var{funcaddr} above, but also specifies the name of the source
7720 file explicitly. This is useful if the name of the function does not
7721 specify the function unambiguously, e.g., if there are several
7722 functions with identical names in different source files.
7726 @section Editing Source Files
7727 @cindex editing source files
7730 @kindex e @r{(@code{edit})}
7731 To edit the lines in a source file, use the @code{edit} command.
7732 The editing program of your choice
7733 is invoked with the current line set to
7734 the active line in the program.
7735 Alternatively, there are several ways to specify what part of the file you
7736 want to print if you want to see other parts of the program:
7739 @item edit @var{location}
7740 Edit the source file specified by @code{location}. Editing starts at
7741 that @var{location}, e.g., at the specified source line of the
7742 specified file. @xref{Specify Location}, for all the possible forms
7743 of the @var{location} argument; here are the forms of the @code{edit}
7744 command most commonly used:
7747 @item edit @var{number}
7748 Edit the current source file with @var{number} as the active line number.
7750 @item edit @var{function}
7751 Edit the file containing @var{function} at the beginning of its definition.
7756 @subsection Choosing your Editor
7757 You can customize @value{GDBN} to use any editor you want
7759 The only restriction is that your editor (say @code{ex}), recognizes the
7760 following command-line syntax:
7762 ex +@var{number} file
7764 The optional numeric value +@var{number} specifies the number of the line in
7765 the file where to start editing.}.
7766 By default, it is @file{@value{EDITOR}}, but you can change this
7767 by setting the environment variable @code{EDITOR} before using
7768 @value{GDBN}. For example, to configure @value{GDBN} to use the
7769 @code{vi} editor, you could use these commands with the @code{sh} shell:
7775 or in the @code{csh} shell,
7777 setenv EDITOR /usr/bin/vi
7782 @section Searching Source Files
7783 @cindex searching source files
7785 There are two commands for searching through the current source file for a
7790 @kindex forward-search
7791 @kindex fo @r{(@code{forward-search})}
7792 @item forward-search @var{regexp}
7793 @itemx search @var{regexp}
7794 The command @samp{forward-search @var{regexp}} checks each line,
7795 starting with the one following the last line listed, for a match for
7796 @var{regexp}. It lists the line that is found. You can use the
7797 synonym @samp{search @var{regexp}} or abbreviate the command name as
7800 @kindex reverse-search
7801 @item reverse-search @var{regexp}
7802 The command @samp{reverse-search @var{regexp}} checks each line, starting
7803 with the one before the last line listed and going backward, for a match
7804 for @var{regexp}. It lists the line that is found. You can abbreviate
7805 this command as @code{rev}.
7809 @section Specifying Source Directories
7812 @cindex directories for source files
7813 Executable programs sometimes do not record the directories of the source
7814 files from which they were compiled, just the names. Even when they do,
7815 the directories could be moved between the compilation and your debugging
7816 session. @value{GDBN} has a list of directories to search for source files;
7817 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7818 it tries all the directories in the list, in the order they are present
7819 in the list, until it finds a file with the desired name.
7821 For example, suppose an executable references the file
7822 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7823 @file{/mnt/cross}. The file is first looked up literally; if this
7824 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7825 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7826 message is printed. @value{GDBN} does not look up the parts of the
7827 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7828 Likewise, the subdirectories of the source path are not searched: if
7829 the source path is @file{/mnt/cross}, and the binary refers to
7830 @file{foo.c}, @value{GDBN} would not find it under
7831 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7833 Plain file names, relative file names with leading directories, file
7834 names containing dots, etc.@: are all treated as described above; for
7835 instance, if the source path is @file{/mnt/cross}, and the source file
7836 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7837 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7838 that---@file{/mnt/cross/foo.c}.
7840 Note that the executable search path is @emph{not} used to locate the
7843 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7844 any information it has cached about where source files are found and where
7845 each line is in the file.
7849 When you start @value{GDBN}, its source path includes only @samp{cdir}
7850 and @samp{cwd}, in that order.
7851 To add other directories, use the @code{directory} command.
7853 The search path is used to find both program source files and @value{GDBN}
7854 script files (read using the @samp{-command} option and @samp{source} command).
7856 In addition to the source path, @value{GDBN} provides a set of commands
7857 that manage a list of source path substitution rules. A @dfn{substitution
7858 rule} specifies how to rewrite source directories stored in the program's
7859 debug information in case the sources were moved to a different
7860 directory between compilation and debugging. A rule is made of
7861 two strings, the first specifying what needs to be rewritten in
7862 the path, and the second specifying how it should be rewritten.
7863 In @ref{set substitute-path}, we name these two parts @var{from} and
7864 @var{to} respectively. @value{GDBN} does a simple string replacement
7865 of @var{from} with @var{to} at the start of the directory part of the
7866 source file name, and uses that result instead of the original file
7867 name to look up the sources.
7869 Using the previous example, suppose the @file{foo-1.0} tree has been
7870 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7871 @value{GDBN} to replace @file{/usr/src} in all source path names with
7872 @file{/mnt/cross}. The first lookup will then be
7873 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7874 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7875 substitution rule, use the @code{set substitute-path} command
7876 (@pxref{set substitute-path}).
7878 To avoid unexpected substitution results, a rule is applied only if the
7879 @var{from} part of the directory name ends at a directory separator.
7880 For instance, a rule substituting @file{/usr/source} into
7881 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7882 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7883 is applied only at the beginning of the directory name, this rule will
7884 not be applied to @file{/root/usr/source/baz.c} either.
7886 In many cases, you can achieve the same result using the @code{directory}
7887 command. However, @code{set substitute-path} can be more efficient in
7888 the case where the sources are organized in a complex tree with multiple
7889 subdirectories. With the @code{directory} command, you need to add each
7890 subdirectory of your project. If you moved the entire tree while
7891 preserving its internal organization, then @code{set substitute-path}
7892 allows you to direct the debugger to all the sources with one single
7895 @code{set substitute-path} is also more than just a shortcut command.
7896 The source path is only used if the file at the original location no
7897 longer exists. On the other hand, @code{set substitute-path} modifies
7898 the debugger behavior to look at the rewritten location instead. So, if
7899 for any reason a source file that is not relevant to your executable is
7900 located at the original location, a substitution rule is the only
7901 method available to point @value{GDBN} at the new location.
7903 @cindex @samp{--with-relocated-sources}
7904 @cindex default source path substitution
7905 You can configure a default source path substitution rule by
7906 configuring @value{GDBN} with the
7907 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7908 should be the name of a directory under @value{GDBN}'s configured
7909 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7910 directory names in debug information under @var{dir} will be adjusted
7911 automatically if the installed @value{GDBN} is moved to a new
7912 location. This is useful if @value{GDBN}, libraries or executables
7913 with debug information and corresponding source code are being moved
7917 @item directory @var{dirname} @dots{}
7918 @item dir @var{dirname} @dots{}
7919 Add directory @var{dirname} to the front of the source path. Several
7920 directory names may be given to this command, separated by @samp{:}
7921 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7922 part of absolute file names) or
7923 whitespace. You may specify a directory that is already in the source
7924 path; this moves it forward, so @value{GDBN} searches it sooner.
7928 @vindex $cdir@r{, convenience variable}
7929 @vindex $cwd@r{, convenience variable}
7930 @cindex compilation directory
7931 @cindex current directory
7932 @cindex working directory
7933 @cindex directory, current
7934 @cindex directory, compilation
7935 You can use the string @samp{$cdir} to refer to the compilation
7936 directory (if one is recorded), and @samp{$cwd} to refer to the current
7937 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7938 tracks the current working directory as it changes during your @value{GDBN}
7939 session, while the latter is immediately expanded to the current
7940 directory at the time you add an entry to the source path.
7943 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7945 @c RET-repeat for @code{directory} is explicitly disabled, but since
7946 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7948 @item set directories @var{path-list}
7949 @kindex set directories
7950 Set the source path to @var{path-list}.
7951 @samp{$cdir:$cwd} are added if missing.
7953 @item show directories
7954 @kindex show directories
7955 Print the source path: show which directories it contains.
7957 @anchor{set substitute-path}
7958 @item set substitute-path @var{from} @var{to}
7959 @kindex set substitute-path
7960 Define a source path substitution rule, and add it at the end of the
7961 current list of existing substitution rules. If a rule with the same
7962 @var{from} was already defined, then the old rule is also deleted.
7964 For example, if the file @file{/foo/bar/baz.c} was moved to
7965 @file{/mnt/cross/baz.c}, then the command
7968 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
7972 will tell @value{GDBN} to replace @samp{/foo/bar} with
7973 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7974 @file{baz.c} even though it was moved.
7976 In the case when more than one substitution rule have been defined,
7977 the rules are evaluated one by one in the order where they have been
7978 defined. The first one matching, if any, is selected to perform
7981 For instance, if we had entered the following commands:
7984 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7985 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7989 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7990 @file{/mnt/include/defs.h} by using the first rule. However, it would
7991 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7992 @file{/mnt/src/lib/foo.c}.
7995 @item unset substitute-path [path]
7996 @kindex unset substitute-path
7997 If a path is specified, search the current list of substitution rules
7998 for a rule that would rewrite that path. Delete that rule if found.
7999 A warning is emitted by the debugger if no rule could be found.
8001 If no path is specified, then all substitution rules are deleted.
8003 @item show substitute-path [path]
8004 @kindex show substitute-path
8005 If a path is specified, then print the source path substitution rule
8006 which would rewrite that path, if any.
8008 If no path is specified, then print all existing source path substitution
8013 If your source path is cluttered with directories that are no longer of
8014 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8015 versions of source. You can correct the situation as follows:
8019 Use @code{directory} with no argument to reset the source path to its default value.
8022 Use @code{directory} with suitable arguments to reinstall the
8023 directories you want in the source path. You can add all the
8024 directories in one command.
8028 @section Source and Machine Code
8029 @cindex source line and its code address
8031 You can use the command @code{info line} to map source lines to program
8032 addresses (and vice versa), and the command @code{disassemble} to display
8033 a range of addresses as machine instructions. You can use the command
8034 @code{set disassemble-next-line} to set whether to disassemble next
8035 source line when execution stops. When run under @sc{gnu} Emacs
8036 mode, the @code{info line} command causes the arrow to point to the
8037 line specified. Also, @code{info line} prints addresses in symbolic form as
8042 @item info line @var{location}
8043 Print the starting and ending addresses of the compiled code for
8044 source line @var{location}. You can specify source lines in any of
8045 the ways documented in @ref{Specify Location}.
8048 For example, we can use @code{info line} to discover the location of
8049 the object code for the first line of function
8050 @code{m4_changequote}:
8052 @c FIXME: I think this example should also show the addresses in
8053 @c symbolic form, as they usually would be displayed.
8055 (@value{GDBP}) info line m4_changequote
8056 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8060 @cindex code address and its source line
8061 We can also inquire (using @code{*@var{addr}} as the form for
8062 @var{location}) what source line covers a particular address:
8064 (@value{GDBP}) info line *0x63ff
8065 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8068 @cindex @code{$_} and @code{info line}
8069 @cindex @code{x} command, default address
8070 @kindex x@r{(examine), and} info line
8071 After @code{info line}, the default address for the @code{x} command
8072 is changed to the starting address of the line, so that @samp{x/i} is
8073 sufficient to begin examining the machine code (@pxref{Memory,
8074 ,Examining Memory}). Also, this address is saved as the value of the
8075 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8080 @cindex assembly instructions
8081 @cindex instructions, assembly
8082 @cindex machine instructions
8083 @cindex listing machine instructions
8085 @itemx disassemble /m
8086 @itemx disassemble /s
8087 @itemx disassemble /r
8088 This specialized command dumps a range of memory as machine
8089 instructions. It can also print mixed source+disassembly by specifying
8090 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8091 as well as in symbolic form by specifying the @code{/r} modifier.
8092 The default memory range is the function surrounding the
8093 program counter of the selected frame. A single argument to this
8094 command is a program counter value; @value{GDBN} dumps the function
8095 surrounding this value. When two arguments are given, they should
8096 be separated by a comma, possibly surrounded by whitespace. The
8097 arguments specify a range of addresses to dump, in one of two forms:
8100 @item @var{start},@var{end}
8101 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8102 @item @var{start},+@var{length}
8103 the addresses from @var{start} (inclusive) to
8104 @code{@var{start}+@var{length}} (exclusive).
8108 When 2 arguments are specified, the name of the function is also
8109 printed (since there could be several functions in the given range).
8111 The argument(s) can be any expression yielding a numeric value, such as
8112 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8114 If the range of memory being disassembled contains current program counter,
8115 the instruction at that location is shown with a @code{=>} marker.
8118 The following example shows the disassembly of a range of addresses of
8119 HP PA-RISC 2.0 code:
8122 (@value{GDBP}) disas 0x32c4, 0x32e4
8123 Dump of assembler code from 0x32c4 to 0x32e4:
8124 0x32c4 <main+204>: addil 0,dp
8125 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8126 0x32cc <main+212>: ldil 0x3000,r31
8127 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8128 0x32d4 <main+220>: ldo 0(r31),rp
8129 0x32d8 <main+224>: addil -0x800,dp
8130 0x32dc <main+228>: ldo 0x588(r1),r26
8131 0x32e0 <main+232>: ldil 0x3000,r31
8132 End of assembler dump.
8135 Here is an example showing mixed source+assembly for Intel x86
8136 with @code{/m} or @code{/s}, when the program is stopped just after
8137 function prologue in a non-optimized function with no inline code.
8140 (@value{GDBP}) disas /m main
8141 Dump of assembler code for function main:
8143 0x08048330 <+0>: push %ebp
8144 0x08048331 <+1>: mov %esp,%ebp
8145 0x08048333 <+3>: sub $0x8,%esp
8146 0x08048336 <+6>: and $0xfffffff0,%esp
8147 0x08048339 <+9>: sub $0x10,%esp
8149 6 printf ("Hello.\n");
8150 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8151 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8155 0x08048348 <+24>: mov $0x0,%eax
8156 0x0804834d <+29>: leave
8157 0x0804834e <+30>: ret
8159 End of assembler dump.
8162 The @code{/m} option is deprecated as its output is not useful when
8163 there is either inlined code or re-ordered code.
8164 The @code{/s} option is the preferred choice.
8165 Here is an example for AMD x86-64 showing the difference between
8166 @code{/m} output and @code{/s} output.
8167 This example has one inline function defined in a header file,
8168 and the code is compiled with @samp{-O2} optimization.
8169 Note how the @code{/m} output is missing the disassembly of
8170 several instructions that are present in the @code{/s} output.
8200 (@value{GDBP}) disas /m main
8201 Dump of assembler code for function main:
8205 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8206 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8210 0x000000000040041d <+29>: xor %eax,%eax
8211 0x000000000040041f <+31>: retq
8212 0x0000000000400420 <+32>: add %eax,%eax
8213 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8215 End of assembler dump.
8216 (@value{GDBP}) disas /s main
8217 Dump of assembler code for function main:
8221 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8225 0x0000000000400406 <+6>: test %eax,%eax
8226 0x0000000000400408 <+8>: js 0x400420 <main+32>
8231 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8232 0x000000000040040d <+13>: test %eax,%eax
8233 0x000000000040040f <+15>: mov $0x1,%eax
8234 0x0000000000400414 <+20>: cmovne %edx,%eax
8238 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8242 0x000000000040041d <+29>: xor %eax,%eax
8243 0x000000000040041f <+31>: retq
8247 0x0000000000400420 <+32>: add %eax,%eax
8248 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8249 End of assembler dump.
8252 Here is another example showing raw instructions in hex for AMD x86-64,
8255 (gdb) disas /r 0x400281,+10
8256 Dump of assembler code from 0x400281 to 0x40028b:
8257 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8258 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8259 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8260 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8261 End of assembler dump.
8264 Addresses cannot be specified as a location (@pxref{Specify Location}).
8265 So, for example, if you want to disassemble function @code{bar}
8266 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8267 and not @samp{disassemble foo.c:bar}.
8269 Some architectures have more than one commonly-used set of instruction
8270 mnemonics or other syntax.
8272 For programs that were dynamically linked and use shared libraries,
8273 instructions that call functions or branch to locations in the shared
8274 libraries might show a seemingly bogus location---it's actually a
8275 location of the relocation table. On some architectures, @value{GDBN}
8276 might be able to resolve these to actual function names.
8279 @kindex set disassembly-flavor
8280 @cindex Intel disassembly flavor
8281 @cindex AT&T disassembly flavor
8282 @item set disassembly-flavor @var{instruction-set}
8283 Select the instruction set to use when disassembling the
8284 program via the @code{disassemble} or @code{x/i} commands.
8286 Currently this command is only defined for the Intel x86 family. You
8287 can set @var{instruction-set} to either @code{intel} or @code{att}.
8288 The default is @code{att}, the AT&T flavor used by default by Unix
8289 assemblers for x86-based targets.
8291 @kindex show disassembly-flavor
8292 @item show disassembly-flavor
8293 Show the current setting of the disassembly flavor.
8297 @kindex set disassemble-next-line
8298 @kindex show disassemble-next-line
8299 @item set disassemble-next-line
8300 @itemx show disassemble-next-line
8301 Control whether or not @value{GDBN} will disassemble the next source
8302 line or instruction when execution stops. If ON, @value{GDBN} will
8303 display disassembly of the next source line when execution of the
8304 program being debugged stops. This is @emph{in addition} to
8305 displaying the source line itself, which @value{GDBN} always does if
8306 possible. If the next source line cannot be displayed for some reason
8307 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8308 info in the debug info), @value{GDBN} will display disassembly of the
8309 next @emph{instruction} instead of showing the next source line. If
8310 AUTO, @value{GDBN} will display disassembly of next instruction only
8311 if the source line cannot be displayed. This setting causes
8312 @value{GDBN} to display some feedback when you step through a function
8313 with no line info or whose source file is unavailable. The default is
8314 OFF, which means never display the disassembly of the next line or
8320 @chapter Examining Data
8322 @cindex printing data
8323 @cindex examining data
8326 The usual way to examine data in your program is with the @code{print}
8327 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8328 evaluates and prints the value of an expression of the language your
8329 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8330 Different Languages}). It may also print the expression using a
8331 Python-based pretty-printer (@pxref{Pretty Printing}).
8334 @item print @var{expr}
8335 @itemx print /@var{f} @var{expr}
8336 @var{expr} is an expression (in the source language). By default the
8337 value of @var{expr} is printed in a format appropriate to its data type;
8338 you can choose a different format by specifying @samp{/@var{f}}, where
8339 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8343 @itemx print /@var{f}
8344 @cindex reprint the last value
8345 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8346 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8347 conveniently inspect the same value in an alternative format.
8350 A more low-level way of examining data is with the @code{x} command.
8351 It examines data in memory at a specified address and prints it in a
8352 specified format. @xref{Memory, ,Examining Memory}.
8354 If you are interested in information about types, or about how the
8355 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8356 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8359 @cindex exploring hierarchical data structures
8361 Another way of examining values of expressions and type information is
8362 through the Python extension command @code{explore} (available only if
8363 the @value{GDBN} build is configured with @code{--with-python}). It
8364 offers an interactive way to start at the highest level (or, the most
8365 abstract level) of the data type of an expression (or, the data type
8366 itself) and explore all the way down to leaf scalar values/fields
8367 embedded in the higher level data types.
8370 @item explore @var{arg}
8371 @var{arg} is either an expression (in the source language), or a type
8372 visible in the current context of the program being debugged.
8375 The working of the @code{explore} command can be illustrated with an
8376 example. If a data type @code{struct ComplexStruct} is defined in your
8386 struct ComplexStruct
8388 struct SimpleStruct *ss_p;
8394 followed by variable declarations as
8397 struct SimpleStruct ss = @{ 10, 1.11 @};
8398 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8402 then, the value of the variable @code{cs} can be explored using the
8403 @code{explore} command as follows.
8407 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8408 the following fields:
8410 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8411 arr = <Enter 1 to explore this field of type `int [10]'>
8413 Enter the field number of choice:
8417 Since the fields of @code{cs} are not scalar values, you are being
8418 prompted to chose the field you want to explore. Let's say you choose
8419 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8420 pointer, you will be asked if it is pointing to a single value. From
8421 the declaration of @code{cs} above, it is indeed pointing to a single
8422 value, hence you enter @code{y}. If you enter @code{n}, then you will
8423 be asked if it were pointing to an array of values, in which case this
8424 field will be explored as if it were an array.
8427 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8428 Continue exploring it as a pointer to a single value [y/n]: y
8429 The value of `*(cs.ss_p)' is a struct/class of type `struct
8430 SimpleStruct' with the following fields:
8432 i = 10 .. (Value of type `int')
8433 d = 1.1100000000000001 .. (Value of type `double')
8435 Press enter to return to parent value:
8439 If the field @code{arr} of @code{cs} was chosen for exploration by
8440 entering @code{1} earlier, then since it is as array, you will be
8441 prompted to enter the index of the element in the array that you want
8445 `cs.arr' is an array of `int'.
8446 Enter the index of the element you want to explore in `cs.arr': 5
8448 `(cs.arr)[5]' is a scalar value of type `int'.
8452 Press enter to return to parent value:
8455 In general, at any stage of exploration, you can go deeper towards the
8456 leaf values by responding to the prompts appropriately, or hit the
8457 return key to return to the enclosing data structure (the @i{higher}
8458 level data structure).
8460 Similar to exploring values, you can use the @code{explore} command to
8461 explore types. Instead of specifying a value (which is typically a
8462 variable name or an expression valid in the current context of the
8463 program being debugged), you specify a type name. If you consider the
8464 same example as above, your can explore the type
8465 @code{struct ComplexStruct} by passing the argument
8466 @code{struct ComplexStruct} to the @code{explore} command.
8469 (gdb) explore struct ComplexStruct
8473 By responding to the prompts appropriately in the subsequent interactive
8474 session, you can explore the type @code{struct ComplexStruct} in a
8475 manner similar to how the value @code{cs} was explored in the above
8478 The @code{explore} command also has two sub-commands,
8479 @code{explore value} and @code{explore type}. The former sub-command is
8480 a way to explicitly specify that value exploration of the argument is
8481 being invoked, while the latter is a way to explicitly specify that type
8482 exploration of the argument is being invoked.
8485 @item explore value @var{expr}
8486 @cindex explore value
8487 This sub-command of @code{explore} explores the value of the
8488 expression @var{expr} (if @var{expr} is an expression valid in the
8489 current context of the program being debugged). The behavior of this
8490 command is identical to that of the behavior of the @code{explore}
8491 command being passed the argument @var{expr}.
8493 @item explore type @var{arg}
8494 @cindex explore type
8495 This sub-command of @code{explore} explores the type of @var{arg} (if
8496 @var{arg} is a type visible in the current context of program being
8497 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8498 is an expression valid in the current context of the program being
8499 debugged). If @var{arg} is a type, then the behavior of this command is
8500 identical to that of the @code{explore} command being passed the
8501 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8502 this command will be identical to that of the @code{explore} command
8503 being passed the type of @var{arg} as the argument.
8507 * Expressions:: Expressions
8508 * Ambiguous Expressions:: Ambiguous Expressions
8509 * Variables:: Program variables
8510 * Arrays:: Artificial arrays
8511 * Output Formats:: Output formats
8512 * Memory:: Examining memory
8513 * Auto Display:: Automatic display
8514 * Print Settings:: Print settings
8515 * Pretty Printing:: Python pretty printing
8516 * Value History:: Value history
8517 * Convenience Vars:: Convenience variables
8518 * Convenience Funs:: Convenience functions
8519 * Registers:: Registers
8520 * Floating Point Hardware:: Floating point hardware
8521 * Vector Unit:: Vector Unit
8522 * OS Information:: Auxiliary data provided by operating system
8523 * Memory Region Attributes:: Memory region attributes
8524 * Dump/Restore Files:: Copy between memory and a file
8525 * Core File Generation:: Cause a program dump its core
8526 * Character Sets:: Debugging programs that use a different
8527 character set than GDB does
8528 * Caching Target Data:: Data caching for targets
8529 * Searching Memory:: Searching memory for a sequence of bytes
8533 @section Expressions
8536 @code{print} and many other @value{GDBN} commands accept an expression and
8537 compute its value. Any kind of constant, variable or operator defined
8538 by the programming language you are using is valid in an expression in
8539 @value{GDBN}. This includes conditional expressions, function calls,
8540 casts, and string constants. It also includes preprocessor macros, if
8541 you compiled your program to include this information; see
8544 @cindex arrays in expressions
8545 @value{GDBN} supports array constants in expressions input by
8546 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8547 you can use the command @code{print @{1, 2, 3@}} to create an array
8548 of three integers. If you pass an array to a function or assign it
8549 to a program variable, @value{GDBN} copies the array to memory that
8550 is @code{malloc}ed in the target program.
8552 Because C is so widespread, most of the expressions shown in examples in
8553 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8554 Languages}, for information on how to use expressions in other
8557 In this section, we discuss operators that you can use in @value{GDBN}
8558 expressions regardless of your programming language.
8560 @cindex casts, in expressions
8561 Casts are supported in all languages, not just in C, because it is so
8562 useful to cast a number into a pointer in order to examine a structure
8563 at that address in memory.
8564 @c FIXME: casts supported---Mod2 true?
8566 @value{GDBN} supports these operators, in addition to those common
8567 to programming languages:
8571 @samp{@@} is a binary operator for treating parts of memory as arrays.
8572 @xref{Arrays, ,Artificial Arrays}, for more information.
8575 @samp{::} allows you to specify a variable in terms of the file or
8576 function where it is defined. @xref{Variables, ,Program Variables}.
8578 @cindex @{@var{type}@}
8579 @cindex type casting memory
8580 @cindex memory, viewing as typed object
8581 @cindex casts, to view memory
8582 @item @{@var{type}@} @var{addr}
8583 Refers to an object of type @var{type} stored at address @var{addr} in
8584 memory. The address @var{addr} may be any expression whose value is
8585 an integer or pointer (but parentheses are required around binary
8586 operators, just as in a cast). This construct is allowed regardless
8587 of what kind of data is normally supposed to reside at @var{addr}.
8590 @node Ambiguous Expressions
8591 @section Ambiguous Expressions
8592 @cindex ambiguous expressions
8594 Expressions can sometimes contain some ambiguous elements. For instance,
8595 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8596 a single function name to be defined several times, for application in
8597 different contexts. This is called @dfn{overloading}. Another example
8598 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8599 templates and is typically instantiated several times, resulting in
8600 the same function name being defined in different contexts.
8602 In some cases and depending on the language, it is possible to adjust
8603 the expression to remove the ambiguity. For instance in C@t{++}, you
8604 can specify the signature of the function you want to break on, as in
8605 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8606 qualified name of your function often makes the expression unambiguous
8609 When an ambiguity that needs to be resolved is detected, the debugger
8610 has the capability to display a menu of numbered choices for each
8611 possibility, and then waits for the selection with the prompt @samp{>}.
8612 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8613 aborts the current command. If the command in which the expression was
8614 used allows more than one choice to be selected, the next option in the
8615 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8618 For example, the following session excerpt shows an attempt to set a
8619 breakpoint at the overloaded symbol @code{String::after}.
8620 We choose three particular definitions of that function name:
8622 @c FIXME! This is likely to change to show arg type lists, at least
8625 (@value{GDBP}) b String::after
8628 [2] file:String.cc; line number:867
8629 [3] file:String.cc; line number:860
8630 [4] file:String.cc; line number:875
8631 [5] file:String.cc; line number:853
8632 [6] file:String.cc; line number:846
8633 [7] file:String.cc; line number:735
8635 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8636 Breakpoint 2 at 0xb344: file String.cc, line 875.
8637 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8638 Multiple breakpoints were set.
8639 Use the "delete" command to delete unwanted
8646 @kindex set multiple-symbols
8647 @item set multiple-symbols @var{mode}
8648 @cindex multiple-symbols menu
8650 This option allows you to adjust the debugger behavior when an expression
8653 By default, @var{mode} is set to @code{all}. If the command with which
8654 the expression is used allows more than one choice, then @value{GDBN}
8655 automatically selects all possible choices. For instance, inserting
8656 a breakpoint on a function using an ambiguous name results in a breakpoint
8657 inserted on each possible match. However, if a unique choice must be made,
8658 then @value{GDBN} uses the menu to help you disambiguate the expression.
8659 For instance, printing the address of an overloaded function will result
8660 in the use of the menu.
8662 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8663 when an ambiguity is detected.
8665 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8666 an error due to the ambiguity and the command is aborted.
8668 @kindex show multiple-symbols
8669 @item show multiple-symbols
8670 Show the current value of the @code{multiple-symbols} setting.
8674 @section Program Variables
8676 The most common kind of expression to use is the name of a variable
8679 Variables in expressions are understood in the selected stack frame
8680 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8684 global (or file-static)
8691 visible according to the scope rules of the
8692 programming language from the point of execution in that frame
8695 @noindent This means that in the function
8710 you can examine and use the variable @code{a} whenever your program is
8711 executing within the function @code{foo}, but you can only use or
8712 examine the variable @code{b} while your program is executing inside
8713 the block where @code{b} is declared.
8715 @cindex variable name conflict
8716 There is an exception: you can refer to a variable or function whose
8717 scope is a single source file even if the current execution point is not
8718 in this file. But it is possible to have more than one such variable or
8719 function with the same name (in different source files). If that
8720 happens, referring to that name has unpredictable effects. If you wish,
8721 you can specify a static variable in a particular function or file by
8722 using the colon-colon (@code{::}) notation:
8724 @cindex colon-colon, context for variables/functions
8726 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8727 @cindex @code{::}, context for variables/functions
8730 @var{file}::@var{variable}
8731 @var{function}::@var{variable}
8735 Here @var{file} or @var{function} is the name of the context for the
8736 static @var{variable}. In the case of file names, you can use quotes to
8737 make sure @value{GDBN} parses the file name as a single word---for example,
8738 to print a global value of @code{x} defined in @file{f2.c}:
8741 (@value{GDBP}) p 'f2.c'::x
8744 The @code{::} notation is normally used for referring to
8745 static variables, since you typically disambiguate uses of local variables
8746 in functions by selecting the appropriate frame and using the
8747 simple name of the variable. However, you may also use this notation
8748 to refer to local variables in frames enclosing the selected frame:
8757 process (a); /* Stop here */
8768 For example, if there is a breakpoint at the commented line,
8769 here is what you might see
8770 when the program stops after executing the call @code{bar(0)}:
8775 (@value{GDBP}) p bar::a
8778 #2 0x080483d0 in foo (a=5) at foobar.c:12
8781 (@value{GDBP}) p bar::a
8785 @cindex C@t{++} scope resolution
8786 These uses of @samp{::} are very rarely in conflict with the very
8787 similar use of the same notation in C@t{++}. When they are in
8788 conflict, the C@t{++} meaning takes precedence; however, this can be
8789 overridden by quoting the file or function name with single quotes.
8791 For example, suppose the program is stopped in a method of a class
8792 that has a field named @code{includefile}, and there is also an
8793 include file named @file{includefile} that defines a variable,
8797 (@value{GDBP}) p includefile
8799 (@value{GDBP}) p includefile::some_global
8800 A syntax error in expression, near `'.
8801 (@value{GDBP}) p 'includefile'::some_global
8805 @cindex wrong values
8806 @cindex variable values, wrong
8807 @cindex function entry/exit, wrong values of variables
8808 @cindex optimized code, wrong values of variables
8810 @emph{Warning:} Occasionally, a local variable may appear to have the
8811 wrong value at certain points in a function---just after entry to a new
8812 scope, and just before exit.
8814 You may see this problem when you are stepping by machine instructions.
8815 This is because, on most machines, it takes more than one instruction to
8816 set up a stack frame (including local variable definitions); if you are
8817 stepping by machine instructions, variables may appear to have the wrong
8818 values until the stack frame is completely built. On exit, it usually
8819 also takes more than one machine instruction to destroy a stack frame;
8820 after you begin stepping through that group of instructions, local
8821 variable definitions may be gone.
8823 This may also happen when the compiler does significant optimizations.
8824 To be sure of always seeing accurate values, turn off all optimization
8827 @cindex ``No symbol "foo" in current context''
8828 Another possible effect of compiler optimizations is to optimize
8829 unused variables out of existence, or assign variables to registers (as
8830 opposed to memory addresses). Depending on the support for such cases
8831 offered by the debug info format used by the compiler, @value{GDBN}
8832 might not be able to display values for such local variables. If that
8833 happens, @value{GDBN} will print a message like this:
8836 No symbol "foo" in current context.
8839 To solve such problems, either recompile without optimizations, or use a
8840 different debug info format, if the compiler supports several such
8841 formats. @xref{Compilation}, for more information on choosing compiler
8842 options. @xref{C, ,C and C@t{++}}, for more information about debug
8843 info formats that are best suited to C@t{++} programs.
8845 If you ask to print an object whose contents are unknown to
8846 @value{GDBN}, e.g., because its data type is not completely specified
8847 by the debug information, @value{GDBN} will say @samp{<incomplete
8848 type>}. @xref{Symbols, incomplete type}, for more about this.
8850 If you append @kbd{@@entry} string to a function parameter name you get its
8851 value at the time the function got called. If the value is not available an
8852 error message is printed. Entry values are available only with some compilers.
8853 Entry values are normally also printed at the function parameter list according
8854 to @ref{set print entry-values}.
8857 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8863 (gdb) print i@@entry
8867 Strings are identified as arrays of @code{char} values without specified
8868 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8869 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8870 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8871 defines literal string type @code{"char"} as @code{char} without a sign.
8876 signed char var1[] = "A";
8879 You get during debugging
8884 $2 = @{65 'A', 0 '\0'@}
8888 @section Artificial Arrays
8890 @cindex artificial array
8892 @kindex @@@r{, referencing memory as an array}
8893 It is often useful to print out several successive objects of the
8894 same type in memory; a section of an array, or an array of
8895 dynamically determined size for which only a pointer exists in the
8898 You can do this by referring to a contiguous span of memory as an
8899 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8900 operand of @samp{@@} should be the first element of the desired array
8901 and be an individual object. The right operand should be the desired length
8902 of the array. The result is an array value whose elements are all of
8903 the type of the left argument. The first element is actually the left
8904 argument; the second element comes from bytes of memory immediately
8905 following those that hold the first element, and so on. Here is an
8906 example. If a program says
8909 int *array = (int *) malloc (len * sizeof (int));
8913 you can print the contents of @code{array} with
8919 The left operand of @samp{@@} must reside in memory. Array values made
8920 with @samp{@@} in this way behave just like other arrays in terms of
8921 subscripting, and are coerced to pointers when used in expressions.
8922 Artificial arrays most often appear in expressions via the value history
8923 (@pxref{Value History, ,Value History}), after printing one out.
8925 Another way to create an artificial array is to use a cast.
8926 This re-interprets a value as if it were an array.
8927 The value need not be in memory:
8929 (@value{GDBP}) p/x (short[2])0x12345678
8930 $1 = @{0x1234, 0x5678@}
8933 As a convenience, if you leave the array length out (as in
8934 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8935 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8937 (@value{GDBP}) p/x (short[])0x12345678
8938 $2 = @{0x1234, 0x5678@}
8941 Sometimes the artificial array mechanism is not quite enough; in
8942 moderately complex data structures, the elements of interest may not
8943 actually be adjacent---for example, if you are interested in the values
8944 of pointers in an array. One useful work-around in this situation is
8945 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8946 Variables}) as a counter in an expression that prints the first
8947 interesting value, and then repeat that expression via @key{RET}. For
8948 instance, suppose you have an array @code{dtab} of pointers to
8949 structures, and you are interested in the values of a field @code{fv}
8950 in each structure. Here is an example of what you might type:
8960 @node Output Formats
8961 @section Output Formats
8963 @cindex formatted output
8964 @cindex output formats
8965 By default, @value{GDBN} prints a value according to its data type. Sometimes
8966 this is not what you want. For example, you might want to print a number
8967 in hex, or a pointer in decimal. Or you might want to view data in memory
8968 at a certain address as a character string or as an instruction. To do
8969 these things, specify an @dfn{output format} when you print a value.
8971 The simplest use of output formats is to say how to print a value
8972 already computed. This is done by starting the arguments of the
8973 @code{print} command with a slash and a format letter. The format
8974 letters supported are:
8978 Regard the bits of the value as an integer, and print the integer in
8982 Print as integer in signed decimal.
8985 Print as integer in unsigned decimal.
8988 Print as integer in octal.
8991 Print as integer in binary. The letter @samp{t} stands for ``two''.
8992 @footnote{@samp{b} cannot be used because these format letters are also
8993 used with the @code{x} command, where @samp{b} stands for ``byte'';
8994 see @ref{Memory,,Examining Memory}.}
8997 @cindex unknown address, locating
8998 @cindex locate address
8999 Print as an address, both absolute in hexadecimal and as an offset from
9000 the nearest preceding symbol. You can use this format used to discover
9001 where (in what function) an unknown address is located:
9004 (@value{GDBP}) p/a 0x54320
9005 $3 = 0x54320 <_initialize_vx+396>
9009 The command @code{info symbol 0x54320} yields similar results.
9010 @xref{Symbols, info symbol}.
9013 Regard as an integer and print it as a character constant. This
9014 prints both the numerical value and its character representation. The
9015 character representation is replaced with the octal escape @samp{\nnn}
9016 for characters outside the 7-bit @sc{ascii} range.
9018 Without this format, @value{GDBN} displays @code{char},
9019 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9020 constants. Single-byte members of vectors are displayed as integer
9024 Regard the bits of the value as a floating point number and print
9025 using typical floating point syntax.
9028 @cindex printing strings
9029 @cindex printing byte arrays
9030 Regard as a string, if possible. With this format, pointers to single-byte
9031 data are displayed as null-terminated strings and arrays of single-byte data
9032 are displayed as fixed-length strings. Other values are displayed in their
9035 Without this format, @value{GDBN} displays pointers to and arrays of
9036 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9037 strings. Single-byte members of a vector are displayed as an integer
9041 Like @samp{x} formatting, the value is treated as an integer and
9042 printed as hexadecimal, but leading zeros are printed to pad the value
9043 to the size of the integer type.
9046 @cindex raw printing
9047 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9048 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9049 Printing}). This typically results in a higher-level display of the
9050 value's contents. The @samp{r} format bypasses any Python
9051 pretty-printer which might exist.
9054 For example, to print the program counter in hex (@pxref{Registers}), type
9061 Note that no space is required before the slash; this is because command
9062 names in @value{GDBN} cannot contain a slash.
9064 To reprint the last value in the value history with a different format,
9065 you can use the @code{print} command with just a format and no
9066 expression. For example, @samp{p/x} reprints the last value in hex.
9069 @section Examining Memory
9071 You can use the command @code{x} (for ``examine'') to examine memory in
9072 any of several formats, independently of your program's data types.
9074 @cindex examining memory
9076 @kindex x @r{(examine memory)}
9077 @item x/@var{nfu} @var{addr}
9080 Use the @code{x} command to examine memory.
9083 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9084 much memory to display and how to format it; @var{addr} is an
9085 expression giving the address where you want to start displaying memory.
9086 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9087 Several commands set convenient defaults for @var{addr}.
9090 @item @var{n}, the repeat count
9091 The repeat count is a decimal integer; the default is 1. It specifies
9092 how much memory (counting by units @var{u}) to display.
9093 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9096 @item @var{f}, the display format
9097 The display format is one of the formats used by @code{print}
9098 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9099 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9100 The default is @samp{x} (hexadecimal) initially. The default changes
9101 each time you use either @code{x} or @code{print}.
9103 @item @var{u}, the unit size
9104 The unit size is any of
9110 Halfwords (two bytes).
9112 Words (four bytes). This is the initial default.
9114 Giant words (eight bytes).
9117 Each time you specify a unit size with @code{x}, that size becomes the
9118 default unit the next time you use @code{x}. For the @samp{i} format,
9119 the unit size is ignored and is normally not written. For the @samp{s} format,
9120 the unit size defaults to @samp{b}, unless it is explicitly given.
9121 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9122 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9123 Note that the results depend on the programming language of the
9124 current compilation unit. If the language is C, the @samp{s}
9125 modifier will use the UTF-16 encoding while @samp{w} will use
9126 UTF-32. The encoding is set by the programming language and cannot
9129 @item @var{addr}, starting display address
9130 @var{addr} is the address where you want @value{GDBN} to begin displaying
9131 memory. The expression need not have a pointer value (though it may);
9132 it is always interpreted as an integer address of a byte of memory.
9133 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9134 @var{addr} is usually just after the last address examined---but several
9135 other commands also set the default address: @code{info breakpoints} (to
9136 the address of the last breakpoint listed), @code{info line} (to the
9137 starting address of a line), and @code{print} (if you use it to display
9138 a value from memory).
9141 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9142 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9143 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9144 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9145 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9147 Since the letters indicating unit sizes are all distinct from the
9148 letters specifying output formats, you do not have to remember whether
9149 unit size or format comes first; either order works. The output
9150 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9151 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9153 Even though the unit size @var{u} is ignored for the formats @samp{s}
9154 and @samp{i}, you might still want to use a count @var{n}; for example,
9155 @samp{3i} specifies that you want to see three machine instructions,
9156 including any operands. For convenience, especially when used with
9157 the @code{display} command, the @samp{i} format also prints branch delay
9158 slot instructions, if any, beyond the count specified, which immediately
9159 follow the last instruction that is within the count. The command
9160 @code{disassemble} gives an alternative way of inspecting machine
9161 instructions; see @ref{Machine Code,,Source and Machine Code}.
9163 All the defaults for the arguments to @code{x} are designed to make it
9164 easy to continue scanning memory with minimal specifications each time
9165 you use @code{x}. For example, after you have inspected three machine
9166 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9167 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9168 the repeat count @var{n} is used again; the other arguments default as
9169 for successive uses of @code{x}.
9171 When examining machine instructions, the instruction at current program
9172 counter is shown with a @code{=>} marker. For example:
9175 (@value{GDBP}) x/5i $pc-6
9176 0x804837f <main+11>: mov %esp,%ebp
9177 0x8048381 <main+13>: push %ecx
9178 0x8048382 <main+14>: sub $0x4,%esp
9179 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9180 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9183 @cindex @code{$_}, @code{$__}, and value history
9184 The addresses and contents printed by the @code{x} command are not saved
9185 in the value history because there is often too much of them and they
9186 would get in the way. Instead, @value{GDBN} makes these values available for
9187 subsequent use in expressions as values of the convenience variables
9188 @code{$_} and @code{$__}. After an @code{x} command, the last address
9189 examined is available for use in expressions in the convenience variable
9190 @code{$_}. The contents of that address, as examined, are available in
9191 the convenience variable @code{$__}.
9193 If the @code{x} command has a repeat count, the address and contents saved
9194 are from the last memory unit printed; this is not the same as the last
9195 address printed if several units were printed on the last line of output.
9197 @anchor{addressable memory unit}
9198 @cindex addressable memory unit
9199 Most targets have an addressable memory unit size of 8 bits. This means
9200 that to each memory address are associated 8 bits of data. Some
9201 targets, however, have other addressable memory unit sizes.
9202 Within @value{GDBN} and this document, the term
9203 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9204 when explicitly referring to a chunk of data of that size. The word
9205 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9206 the addressable memory unit size of the target. For most systems,
9207 addressable memory unit is a synonym of byte.
9209 @cindex remote memory comparison
9210 @cindex target memory comparison
9211 @cindex verify remote memory image
9212 @cindex verify target memory image
9213 When you are debugging a program running on a remote target machine
9214 (@pxref{Remote Debugging}), you may wish to verify the program's image
9215 in the remote machine's memory against the executable file you
9216 downloaded to the target. Or, on any target, you may want to check
9217 whether the program has corrupted its own read-only sections. The
9218 @code{compare-sections} command is provided for such situations.
9221 @kindex compare-sections
9222 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9223 Compare the data of a loadable section @var{section-name} in the
9224 executable file of the program being debugged with the same section in
9225 the target machine's memory, and report any mismatches. With no
9226 arguments, compares all loadable sections. With an argument of
9227 @code{-r}, compares all loadable read-only sections.
9229 Note: for remote targets, this command can be accelerated if the
9230 target supports computing the CRC checksum of a block of memory
9231 (@pxref{qCRC packet}).
9235 @section Automatic Display
9236 @cindex automatic display
9237 @cindex display of expressions
9239 If you find that you want to print the value of an expression frequently
9240 (to see how it changes), you might want to add it to the @dfn{automatic
9241 display list} so that @value{GDBN} prints its value each time your program stops.
9242 Each expression added to the list is given a number to identify it;
9243 to remove an expression from the list, you specify that number.
9244 The automatic display looks like this:
9248 3: bar[5] = (struct hack *) 0x3804
9252 This display shows item numbers, expressions and their current values. As with
9253 displays you request manually using @code{x} or @code{print}, you can
9254 specify the output format you prefer; in fact, @code{display} decides
9255 whether to use @code{print} or @code{x} depending your format
9256 specification---it uses @code{x} if you specify either the @samp{i}
9257 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9261 @item display @var{expr}
9262 Add the expression @var{expr} to the list of expressions to display
9263 each time your program stops. @xref{Expressions, ,Expressions}.
9265 @code{display} does not repeat if you press @key{RET} again after using it.
9267 @item display/@var{fmt} @var{expr}
9268 For @var{fmt} specifying only a display format and not a size or
9269 count, add the expression @var{expr} to the auto-display list but
9270 arrange to display it each time in the specified format @var{fmt}.
9271 @xref{Output Formats,,Output Formats}.
9273 @item display/@var{fmt} @var{addr}
9274 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9275 number of units, add the expression @var{addr} as a memory address to
9276 be examined each time your program stops. Examining means in effect
9277 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9280 For example, @samp{display/i $pc} can be helpful, to see the machine
9281 instruction about to be executed each time execution stops (@samp{$pc}
9282 is a common name for the program counter; @pxref{Registers, ,Registers}).
9285 @kindex delete display
9287 @item undisplay @var{dnums}@dots{}
9288 @itemx delete display @var{dnums}@dots{}
9289 Remove items from the list of expressions to display. Specify the
9290 numbers of the displays that you want affected with the command
9291 argument @var{dnums}. It can be a single display number, one of the
9292 numbers shown in the first field of the @samp{info display} display;
9293 or it could be a range of display numbers, as in @code{2-4}.
9295 @code{undisplay} does not repeat if you press @key{RET} after using it.
9296 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9298 @kindex disable display
9299 @item disable display @var{dnums}@dots{}
9300 Disable the display of item numbers @var{dnums}. A disabled display
9301 item is not printed automatically, but is not forgotten. It may be
9302 enabled again later. Specify the numbers of the displays that you
9303 want affected with the command argument @var{dnums}. It can be a
9304 single display number, one of the numbers shown in the first field of
9305 the @samp{info display} display; or it could be a range of display
9306 numbers, as in @code{2-4}.
9308 @kindex enable display
9309 @item enable display @var{dnums}@dots{}
9310 Enable display of item numbers @var{dnums}. It becomes effective once
9311 again in auto display of its expression, until you specify otherwise.
9312 Specify the numbers of the displays that you want affected with the
9313 command argument @var{dnums}. It can be a single display number, one
9314 of the numbers shown in the first field of the @samp{info display}
9315 display; or it could be a range of display numbers, as in @code{2-4}.
9318 Display the current values of the expressions on the list, just as is
9319 done when your program stops.
9321 @kindex info display
9323 Print the list of expressions previously set up to display
9324 automatically, each one with its item number, but without showing the
9325 values. This includes disabled expressions, which are marked as such.
9326 It also includes expressions which would not be displayed right now
9327 because they refer to automatic variables not currently available.
9330 @cindex display disabled out of scope
9331 If a display expression refers to local variables, then it does not make
9332 sense outside the lexical context for which it was set up. Such an
9333 expression is disabled when execution enters a context where one of its
9334 variables is not defined. For example, if you give the command
9335 @code{display last_char} while inside a function with an argument
9336 @code{last_char}, @value{GDBN} displays this argument while your program
9337 continues to stop inside that function. When it stops elsewhere---where
9338 there is no variable @code{last_char}---the display is disabled
9339 automatically. The next time your program stops where @code{last_char}
9340 is meaningful, you can enable the display expression once again.
9342 @node Print Settings
9343 @section Print Settings
9345 @cindex format options
9346 @cindex print settings
9347 @value{GDBN} provides the following ways to control how arrays, structures,
9348 and symbols are printed.
9351 These settings are useful for debugging programs in any language:
9355 @item set print address
9356 @itemx set print address on
9357 @cindex print/don't print memory addresses
9358 @value{GDBN} prints memory addresses showing the location of stack
9359 traces, structure values, pointer values, breakpoints, and so forth,
9360 even when it also displays the contents of those addresses. The default
9361 is @code{on}. For example, this is what a stack frame display looks like with
9362 @code{set print address on}:
9367 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9369 530 if (lquote != def_lquote)
9373 @item set print address off
9374 Do not print addresses when displaying their contents. For example,
9375 this is the same stack frame displayed with @code{set print address off}:
9379 (@value{GDBP}) set print addr off
9381 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9382 530 if (lquote != def_lquote)
9386 You can use @samp{set print address off} to eliminate all machine
9387 dependent displays from the @value{GDBN} interface. For example, with
9388 @code{print address off}, you should get the same text for backtraces on
9389 all machines---whether or not they involve pointer arguments.
9392 @item show print address
9393 Show whether or not addresses are to be printed.
9396 When @value{GDBN} prints a symbolic address, it normally prints the
9397 closest earlier symbol plus an offset. If that symbol does not uniquely
9398 identify the address (for example, it is a name whose scope is a single
9399 source file), you may need to clarify. One way to do this is with
9400 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9401 you can set @value{GDBN} to print the source file and line number when
9402 it prints a symbolic address:
9405 @item set print symbol-filename on
9406 @cindex source file and line of a symbol
9407 @cindex symbol, source file and line
9408 Tell @value{GDBN} to print the source file name and line number of a
9409 symbol in the symbolic form of an address.
9411 @item set print symbol-filename off
9412 Do not print source file name and line number of a symbol. This is the
9415 @item show print symbol-filename
9416 Show whether or not @value{GDBN} will print the source file name and
9417 line number of a symbol in the symbolic form of an address.
9420 Another situation where it is helpful to show symbol filenames and line
9421 numbers is when disassembling code; @value{GDBN} shows you the line
9422 number and source file that corresponds to each instruction.
9424 Also, you may wish to see the symbolic form only if the address being
9425 printed is reasonably close to the closest earlier symbol:
9428 @item set print max-symbolic-offset @var{max-offset}
9429 @itemx set print max-symbolic-offset unlimited
9430 @cindex maximum value for offset of closest symbol
9431 Tell @value{GDBN} to only display the symbolic form of an address if the
9432 offset between the closest earlier symbol and the address is less than
9433 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9434 to always print the symbolic form of an address if any symbol precedes
9435 it. Zero is equivalent to @code{unlimited}.
9437 @item show print max-symbolic-offset
9438 Ask how large the maximum offset is that @value{GDBN} prints in a
9442 @cindex wild pointer, interpreting
9443 @cindex pointer, finding referent
9444 If you have a pointer and you are not sure where it points, try
9445 @samp{set print symbol-filename on}. Then you can determine the name
9446 and source file location of the variable where it points, using
9447 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9448 For example, here @value{GDBN} shows that a variable @code{ptt} points
9449 at another variable @code{t}, defined in @file{hi2.c}:
9452 (@value{GDBP}) set print symbol-filename on
9453 (@value{GDBP}) p/a ptt
9454 $4 = 0xe008 <t in hi2.c>
9458 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9459 does not show the symbol name and filename of the referent, even with
9460 the appropriate @code{set print} options turned on.
9463 You can also enable @samp{/a}-like formatting all the time using
9464 @samp{set print symbol on}:
9467 @item set print symbol on
9468 Tell @value{GDBN} to print the symbol corresponding to an address, if
9471 @item set print symbol off
9472 Tell @value{GDBN} not to print the symbol corresponding to an
9473 address. In this mode, @value{GDBN} will still print the symbol
9474 corresponding to pointers to functions. This is the default.
9476 @item show print symbol
9477 Show whether @value{GDBN} will display the symbol corresponding to an
9481 Other settings control how different kinds of objects are printed:
9484 @item set print array
9485 @itemx set print array on
9486 @cindex pretty print arrays
9487 Pretty print arrays. This format is more convenient to read,
9488 but uses more space. The default is off.
9490 @item set print array off
9491 Return to compressed format for arrays.
9493 @item show print array
9494 Show whether compressed or pretty format is selected for displaying
9497 @cindex print array indexes
9498 @item set print array-indexes
9499 @itemx set print array-indexes on
9500 Print the index of each element when displaying arrays. May be more
9501 convenient to locate a given element in the array or quickly find the
9502 index of a given element in that printed array. The default is off.
9504 @item set print array-indexes off
9505 Stop printing element indexes when displaying arrays.
9507 @item show print array-indexes
9508 Show whether the index of each element is printed when displaying
9511 @item set print elements @var{number-of-elements}
9512 @itemx set print elements unlimited
9513 @cindex number of array elements to print
9514 @cindex limit on number of printed array elements
9515 Set a limit on how many elements of an array @value{GDBN} will print.
9516 If @value{GDBN} is printing a large array, it stops printing after it has
9517 printed the number of elements set by the @code{set print elements} command.
9518 This limit also applies to the display of strings.
9519 When @value{GDBN} starts, this limit is set to 200.
9520 Setting @var{number-of-elements} to @code{unlimited} or zero means
9521 that the number of elements to print is unlimited.
9523 @item show print elements
9524 Display the number of elements of a large array that @value{GDBN} will print.
9525 If the number is 0, then the printing is unlimited.
9527 @item set print frame-arguments @var{value}
9528 @kindex set print frame-arguments
9529 @cindex printing frame argument values
9530 @cindex print all frame argument values
9531 @cindex print frame argument values for scalars only
9532 @cindex do not print frame argument values
9533 This command allows to control how the values of arguments are printed
9534 when the debugger prints a frame (@pxref{Frames}). The possible
9539 The values of all arguments are printed.
9542 Print the value of an argument only if it is a scalar. The value of more
9543 complex arguments such as arrays, structures, unions, etc, is replaced
9544 by @code{@dots{}}. This is the default. Here is an example where
9545 only scalar arguments are shown:
9548 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9553 None of the argument values are printed. Instead, the value of each argument
9554 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9557 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9562 By default, only scalar arguments are printed. This command can be used
9563 to configure the debugger to print the value of all arguments, regardless
9564 of their type. However, it is often advantageous to not print the value
9565 of more complex parameters. For instance, it reduces the amount of
9566 information printed in each frame, making the backtrace more readable.
9567 Also, it improves performance when displaying Ada frames, because
9568 the computation of large arguments can sometimes be CPU-intensive,
9569 especially in large applications. Setting @code{print frame-arguments}
9570 to @code{scalars} (the default) or @code{none} avoids this computation,
9571 thus speeding up the display of each Ada frame.
9573 @item show print frame-arguments
9574 Show how the value of arguments should be displayed when printing a frame.
9576 @item set print raw frame-arguments on
9577 Print frame arguments in raw, non pretty-printed, form.
9579 @item set print raw frame-arguments off
9580 Print frame arguments in pretty-printed form, if there is a pretty-printer
9581 for the value (@pxref{Pretty Printing}),
9582 otherwise print the value in raw form.
9583 This is the default.
9585 @item show print raw frame-arguments
9586 Show whether to print frame arguments in raw form.
9588 @anchor{set print entry-values}
9589 @item set print entry-values @var{value}
9590 @kindex set print entry-values
9591 Set printing of frame argument values at function entry. In some cases
9592 @value{GDBN} can determine the value of function argument which was passed by
9593 the function caller, even if the value was modified inside the called function
9594 and therefore is different. With optimized code, the current value could be
9595 unavailable, but the entry value may still be known.
9597 The default value is @code{default} (see below for its description). Older
9598 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9599 this feature will behave in the @code{default} setting the same way as with the
9602 This functionality is currently supported only by DWARF 2 debugging format and
9603 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9604 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9607 The @var{value} parameter can be one of the following:
9611 Print only actual parameter values, never print values from function entry
9615 #0 different (val=6)
9616 #0 lost (val=<optimized out>)
9618 #0 invalid (val=<optimized out>)
9622 Print only parameter values from function entry point. The actual parameter
9623 values are never printed.
9625 #0 equal (val@@entry=5)
9626 #0 different (val@@entry=5)
9627 #0 lost (val@@entry=5)
9628 #0 born (val@@entry=<optimized out>)
9629 #0 invalid (val@@entry=<optimized out>)
9633 Print only parameter values from function entry point. If value from function
9634 entry point is not known while the actual value is known, print the actual
9635 value for such parameter.
9637 #0 equal (val@@entry=5)
9638 #0 different (val@@entry=5)
9639 #0 lost (val@@entry=5)
9641 #0 invalid (val@@entry=<optimized out>)
9645 Print actual parameter values. If actual parameter value is not known while
9646 value from function entry point is known, print the entry point value for such
9650 #0 different (val=6)
9651 #0 lost (val@@entry=5)
9653 #0 invalid (val=<optimized out>)
9657 Always print both the actual parameter value and its value from function entry
9658 point, even if values of one or both are not available due to compiler
9661 #0 equal (val=5, val@@entry=5)
9662 #0 different (val=6, val@@entry=5)
9663 #0 lost (val=<optimized out>, val@@entry=5)
9664 #0 born (val=10, val@@entry=<optimized out>)
9665 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9669 Print the actual parameter value if it is known and also its value from
9670 function entry point if it is known. If neither is known, print for the actual
9671 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9672 values are known and identical, print the shortened
9673 @code{param=param@@entry=VALUE} notation.
9675 #0 equal (val=val@@entry=5)
9676 #0 different (val=6, val@@entry=5)
9677 #0 lost (val@@entry=5)
9679 #0 invalid (val=<optimized out>)
9683 Always print the actual parameter value. Print also its value from function
9684 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9685 if both values are known and identical, print the shortened
9686 @code{param=param@@entry=VALUE} notation.
9688 #0 equal (val=val@@entry=5)
9689 #0 different (val=6, val@@entry=5)
9690 #0 lost (val=<optimized out>, val@@entry=5)
9692 #0 invalid (val=<optimized out>)
9696 For analysis messages on possible failures of frame argument values at function
9697 entry resolution see @ref{set debug entry-values}.
9699 @item show print entry-values
9700 Show the method being used for printing of frame argument values at function
9703 @item set print repeats @var{number-of-repeats}
9704 @itemx set print repeats unlimited
9705 @cindex repeated array elements
9706 Set the threshold for suppressing display of repeated array
9707 elements. When the number of consecutive identical elements of an
9708 array exceeds the threshold, @value{GDBN} prints the string
9709 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9710 identical repetitions, instead of displaying the identical elements
9711 themselves. Setting the threshold to @code{unlimited} or zero will
9712 cause all elements to be individually printed. The default threshold
9715 @item show print repeats
9716 Display the current threshold for printing repeated identical
9719 @item set print null-stop
9720 @cindex @sc{null} elements in arrays
9721 Cause @value{GDBN} to stop printing the characters of an array when the first
9722 @sc{null} is encountered. This is useful when large arrays actually
9723 contain only short strings.
9726 @item show print null-stop
9727 Show whether @value{GDBN} stops printing an array on the first
9728 @sc{null} character.
9730 @item set print pretty on
9731 @cindex print structures in indented form
9732 @cindex indentation in structure display
9733 Cause @value{GDBN} to print structures in an indented format with one member
9734 per line, like this:
9749 @item set print pretty off
9750 Cause @value{GDBN} to print structures in a compact format, like this:
9754 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9755 meat = 0x54 "Pork"@}
9760 This is the default format.
9762 @item show print pretty
9763 Show which format @value{GDBN} is using to print structures.
9765 @item set print sevenbit-strings on
9766 @cindex eight-bit characters in strings
9767 @cindex octal escapes in strings
9768 Print using only seven-bit characters; if this option is set,
9769 @value{GDBN} displays any eight-bit characters (in strings or
9770 character values) using the notation @code{\}@var{nnn}. This setting is
9771 best if you are working in English (@sc{ascii}) and you use the
9772 high-order bit of characters as a marker or ``meta'' bit.
9774 @item set print sevenbit-strings off
9775 Print full eight-bit characters. This allows the use of more
9776 international character sets, and is the default.
9778 @item show print sevenbit-strings
9779 Show whether or not @value{GDBN} is printing only seven-bit characters.
9781 @item set print union on
9782 @cindex unions in structures, printing
9783 Tell @value{GDBN} to print unions which are contained in structures
9784 and other unions. This is the default setting.
9786 @item set print union off
9787 Tell @value{GDBN} not to print unions which are contained in
9788 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9791 @item show print union
9792 Ask @value{GDBN} whether or not it will print unions which are contained in
9793 structures and other unions.
9795 For example, given the declarations
9798 typedef enum @{Tree, Bug@} Species;
9799 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9800 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9811 struct thing foo = @{Tree, @{Acorn@}@};
9815 with @code{set print union on} in effect @samp{p foo} would print
9818 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9822 and with @code{set print union off} in effect it would print
9825 $1 = @{it = Tree, form = @{...@}@}
9829 @code{set print union} affects programs written in C-like languages
9835 These settings are of interest when debugging C@t{++} programs:
9838 @cindex demangling C@t{++} names
9839 @item set print demangle
9840 @itemx set print demangle on
9841 Print C@t{++} names in their source form rather than in the encoded
9842 (``mangled'') form passed to the assembler and linker for type-safe
9843 linkage. The default is on.
9845 @item show print demangle
9846 Show whether C@t{++} names are printed in mangled or demangled form.
9848 @item set print asm-demangle
9849 @itemx set print asm-demangle on
9850 Print C@t{++} names in their source form rather than their mangled form, even
9851 in assembler code printouts such as instruction disassemblies.
9854 @item show print asm-demangle
9855 Show whether C@t{++} names in assembly listings are printed in mangled
9858 @cindex C@t{++} symbol decoding style
9859 @cindex symbol decoding style, C@t{++}
9860 @kindex set demangle-style
9861 @item set demangle-style @var{style}
9862 Choose among several encoding schemes used by different compilers to
9863 represent C@t{++} names. The choices for @var{style} are currently:
9867 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9868 This is the default.
9871 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9874 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9877 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9880 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9881 @strong{Warning:} this setting alone is not sufficient to allow
9882 debugging @code{cfront}-generated executables. @value{GDBN} would
9883 require further enhancement to permit that.
9886 If you omit @var{style}, you will see a list of possible formats.
9888 @item show demangle-style
9889 Display the encoding style currently in use for decoding C@t{++} symbols.
9891 @item set print object
9892 @itemx set print object on
9893 @cindex derived type of an object, printing
9894 @cindex display derived types
9895 When displaying a pointer to an object, identify the @emph{actual}
9896 (derived) type of the object rather than the @emph{declared} type, using
9897 the virtual function table. Note that the virtual function table is
9898 required---this feature can only work for objects that have run-time
9899 type identification; a single virtual method in the object's declared
9900 type is sufficient. Note that this setting is also taken into account when
9901 working with variable objects via MI (@pxref{GDB/MI}).
9903 @item set print object off
9904 Display only the declared type of objects, without reference to the
9905 virtual function table. This is the default setting.
9907 @item show print object
9908 Show whether actual, or declared, object types are displayed.
9910 @item set print static-members
9911 @itemx set print static-members on
9912 @cindex static members of C@t{++} objects
9913 Print static members when displaying a C@t{++} object. The default is on.
9915 @item set print static-members off
9916 Do not print static members when displaying a C@t{++} object.
9918 @item show print static-members
9919 Show whether C@t{++} static members are printed or not.
9921 @item set print pascal_static-members
9922 @itemx set print pascal_static-members on
9923 @cindex static members of Pascal objects
9924 @cindex Pascal objects, static members display
9925 Print static members when displaying a Pascal object. The default is on.
9927 @item set print pascal_static-members off
9928 Do not print static members when displaying a Pascal object.
9930 @item show print pascal_static-members
9931 Show whether Pascal static members are printed or not.
9933 @c These don't work with HP ANSI C++ yet.
9934 @item set print vtbl
9935 @itemx set print vtbl on
9936 @cindex pretty print C@t{++} virtual function tables
9937 @cindex virtual functions (C@t{++}) display
9938 @cindex VTBL display
9939 Pretty print C@t{++} virtual function tables. The default is off.
9940 (The @code{vtbl} commands do not work on programs compiled with the HP
9941 ANSI C@t{++} compiler (@code{aCC}).)
9943 @item set print vtbl off
9944 Do not pretty print C@t{++} virtual function tables.
9946 @item show print vtbl
9947 Show whether C@t{++} virtual function tables are pretty printed, or not.
9950 @node Pretty Printing
9951 @section Pretty Printing
9953 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9954 Python code. It greatly simplifies the display of complex objects. This
9955 mechanism works for both MI and the CLI.
9958 * Pretty-Printer Introduction:: Introduction to pretty-printers
9959 * Pretty-Printer Example:: An example pretty-printer
9960 * Pretty-Printer Commands:: Pretty-printer commands
9963 @node Pretty-Printer Introduction
9964 @subsection Pretty-Printer Introduction
9966 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9967 registered for the value. If there is then @value{GDBN} invokes the
9968 pretty-printer to print the value. Otherwise the value is printed normally.
9970 Pretty-printers are normally named. This makes them easy to manage.
9971 The @samp{info pretty-printer} command will list all the installed
9972 pretty-printers with their names.
9973 If a pretty-printer can handle multiple data types, then its
9974 @dfn{subprinters} are the printers for the individual data types.
9975 Each such subprinter has its own name.
9976 The format of the name is @var{printer-name};@var{subprinter-name}.
9978 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9979 Typically they are automatically loaded and registered when the corresponding
9980 debug information is loaded, thus making them available without having to
9981 do anything special.
9983 There are three places where a pretty-printer can be registered.
9987 Pretty-printers registered globally are available when debugging
9991 Pretty-printers registered with a program space are available only
9992 when debugging that program.
9993 @xref{Progspaces In Python}, for more details on program spaces in Python.
9996 Pretty-printers registered with an objfile are loaded and unloaded
9997 with the corresponding objfile (e.g., shared library).
9998 @xref{Objfiles In Python}, for more details on objfiles in Python.
10001 @xref{Selecting Pretty-Printers}, for further information on how
10002 pretty-printers are selected,
10004 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10007 @node Pretty-Printer Example
10008 @subsection Pretty-Printer Example
10010 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10013 (@value{GDBP}) print s
10015 static npos = 4294967295,
10017 <std::allocator<char>> = @{
10018 <__gnu_cxx::new_allocator<char>> = @{
10019 <No data fields>@}, <No data fields>
10021 members of std::basic_string<char, std::char_traits<char>,
10022 std::allocator<char> >::_Alloc_hider:
10023 _M_p = 0x804a014 "abcd"
10028 With a pretty-printer for @code{std::string} only the contents are printed:
10031 (@value{GDBP}) print s
10035 @node Pretty-Printer Commands
10036 @subsection Pretty-Printer Commands
10037 @cindex pretty-printer commands
10040 @kindex info pretty-printer
10041 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10042 Print the list of installed pretty-printers.
10043 This includes disabled pretty-printers, which are marked as such.
10045 @var{object-regexp} is a regular expression matching the objects
10046 whose pretty-printers to list.
10047 Objects can be @code{global}, the program space's file
10048 (@pxref{Progspaces In Python}),
10049 and the object files within that program space (@pxref{Objfiles In Python}).
10050 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10051 looks up a printer from these three objects.
10053 @var{name-regexp} is a regular expression matching the name of the printers
10056 @kindex disable pretty-printer
10057 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10058 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10059 A disabled pretty-printer is not forgotten, it may be enabled again later.
10061 @kindex enable pretty-printer
10062 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10063 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10068 Suppose we have three pretty-printers installed: one from library1.so
10069 named @code{foo} that prints objects of type @code{foo}, and
10070 another from library2.so named @code{bar} that prints two types of objects,
10071 @code{bar1} and @code{bar2}.
10074 (gdb) info pretty-printer
10081 (gdb) info pretty-printer library2
10086 (gdb) disable pretty-printer library1
10088 2 of 3 printers enabled
10089 (gdb) info pretty-printer
10096 (gdb) disable pretty-printer library2 bar:bar1
10098 1 of 3 printers enabled
10099 (gdb) info pretty-printer library2
10106 (gdb) disable pretty-printer library2 bar
10108 0 of 3 printers enabled
10109 (gdb) info pretty-printer library2
10118 Note that for @code{bar} the entire printer can be disabled,
10119 as can each individual subprinter.
10121 @node Value History
10122 @section Value History
10124 @cindex value history
10125 @cindex history of values printed by @value{GDBN}
10126 Values printed by the @code{print} command are saved in the @value{GDBN}
10127 @dfn{value history}. This allows you to refer to them in other expressions.
10128 Values are kept until the symbol table is re-read or discarded
10129 (for example with the @code{file} or @code{symbol-file} commands).
10130 When the symbol table changes, the value history is discarded,
10131 since the values may contain pointers back to the types defined in the
10136 @cindex history number
10137 The values printed are given @dfn{history numbers} by which you can
10138 refer to them. These are successive integers starting with one.
10139 @code{print} shows you the history number assigned to a value by
10140 printing @samp{$@var{num} = } before the value; here @var{num} is the
10143 To refer to any previous value, use @samp{$} followed by the value's
10144 history number. The way @code{print} labels its output is designed to
10145 remind you of this. Just @code{$} refers to the most recent value in
10146 the history, and @code{$$} refers to the value before that.
10147 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10148 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10149 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10151 For example, suppose you have just printed a pointer to a structure and
10152 want to see the contents of the structure. It suffices to type
10158 If you have a chain of structures where the component @code{next} points
10159 to the next one, you can print the contents of the next one with this:
10166 You can print successive links in the chain by repeating this
10167 command---which you can do by just typing @key{RET}.
10169 Note that the history records values, not expressions. If the value of
10170 @code{x} is 4 and you type these commands:
10178 then the value recorded in the value history by the @code{print} command
10179 remains 4 even though the value of @code{x} has changed.
10182 @kindex show values
10184 Print the last ten values in the value history, with their item numbers.
10185 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10186 values} does not change the history.
10188 @item show values @var{n}
10189 Print ten history values centered on history item number @var{n}.
10191 @item show values +
10192 Print ten history values just after the values last printed. If no more
10193 values are available, @code{show values +} produces no display.
10196 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10197 same effect as @samp{show values +}.
10199 @node Convenience Vars
10200 @section Convenience Variables
10202 @cindex convenience variables
10203 @cindex user-defined variables
10204 @value{GDBN} provides @dfn{convenience variables} that you can use within
10205 @value{GDBN} to hold on to a value and refer to it later. These variables
10206 exist entirely within @value{GDBN}; they are not part of your program, and
10207 setting a convenience variable has no direct effect on further execution
10208 of your program. That is why you can use them freely.
10210 Convenience variables are prefixed with @samp{$}. Any name preceded by
10211 @samp{$} can be used for a convenience variable, unless it is one of
10212 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10213 (Value history references, in contrast, are @emph{numbers} preceded
10214 by @samp{$}. @xref{Value History, ,Value History}.)
10216 You can save a value in a convenience variable with an assignment
10217 expression, just as you would set a variable in your program.
10221 set $foo = *object_ptr
10225 would save in @code{$foo} the value contained in the object pointed to by
10228 Using a convenience variable for the first time creates it, but its
10229 value is @code{void} until you assign a new value. You can alter the
10230 value with another assignment at any time.
10232 Convenience variables have no fixed types. You can assign a convenience
10233 variable any type of value, including structures and arrays, even if
10234 that variable already has a value of a different type. The convenience
10235 variable, when used as an expression, has the type of its current value.
10238 @kindex show convenience
10239 @cindex show all user variables and functions
10240 @item show convenience
10241 Print a list of convenience variables used so far, and their values,
10242 as well as a list of the convenience functions.
10243 Abbreviated @code{show conv}.
10245 @kindex init-if-undefined
10246 @cindex convenience variables, initializing
10247 @item init-if-undefined $@var{variable} = @var{expression}
10248 Set a convenience variable if it has not already been set. This is useful
10249 for user-defined commands that keep some state. It is similar, in concept,
10250 to using local static variables with initializers in C (except that
10251 convenience variables are global). It can also be used to allow users to
10252 override default values used in a command script.
10254 If the variable is already defined then the expression is not evaluated so
10255 any side-effects do not occur.
10258 One of the ways to use a convenience variable is as a counter to be
10259 incremented or a pointer to be advanced. For example, to print
10260 a field from successive elements of an array of structures:
10264 print bar[$i++]->contents
10268 Repeat that command by typing @key{RET}.
10270 Some convenience variables are created automatically by @value{GDBN} and given
10271 values likely to be useful.
10274 @vindex $_@r{, convenience variable}
10276 The variable @code{$_} is automatically set by the @code{x} command to
10277 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10278 commands which provide a default address for @code{x} to examine also
10279 set @code{$_} to that address; these commands include @code{info line}
10280 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10281 except when set by the @code{x} command, in which case it is a pointer
10282 to the type of @code{$__}.
10284 @vindex $__@r{, convenience variable}
10286 The variable @code{$__} is automatically set by the @code{x} command
10287 to the value found in the last address examined. Its type is chosen
10288 to match the format in which the data was printed.
10291 @vindex $_exitcode@r{, convenience variable}
10292 When the program being debugged terminates normally, @value{GDBN}
10293 automatically sets this variable to the exit code of the program, and
10294 resets @code{$_exitsignal} to @code{void}.
10297 @vindex $_exitsignal@r{, convenience variable}
10298 When the program being debugged dies due to an uncaught signal,
10299 @value{GDBN} automatically sets this variable to that signal's number,
10300 and resets @code{$_exitcode} to @code{void}.
10302 To distinguish between whether the program being debugged has exited
10303 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10304 @code{$_exitsignal} is not @code{void}), the convenience function
10305 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10306 Functions}). For example, considering the following source code:
10309 #include <signal.h>
10312 main (int argc, char *argv[])
10319 A valid way of telling whether the program being debugged has exited
10320 or signalled would be:
10323 (@value{GDBP}) define has_exited_or_signalled
10324 Type commands for definition of ``has_exited_or_signalled''.
10325 End with a line saying just ``end''.
10326 >if $_isvoid ($_exitsignal)
10327 >echo The program has exited\n
10329 >echo The program has signalled\n
10335 Program terminated with signal SIGALRM, Alarm clock.
10336 The program no longer exists.
10337 (@value{GDBP}) has_exited_or_signalled
10338 The program has signalled
10341 As can be seen, @value{GDBN} correctly informs that the program being
10342 debugged has signalled, since it calls @code{raise} and raises a
10343 @code{SIGALRM} signal. If the program being debugged had not called
10344 @code{raise}, then @value{GDBN} would report a normal exit:
10347 (@value{GDBP}) has_exited_or_signalled
10348 The program has exited
10352 The variable @code{$_exception} is set to the exception object being
10353 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10356 @itemx $_probe_arg0@dots{}$_probe_arg11
10357 Arguments to a static probe. @xref{Static Probe Points}.
10360 @vindex $_sdata@r{, inspect, convenience variable}
10361 The variable @code{$_sdata} contains extra collected static tracepoint
10362 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10363 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10364 if extra static tracepoint data has not been collected.
10367 @vindex $_siginfo@r{, convenience variable}
10368 The variable @code{$_siginfo} contains extra signal information
10369 (@pxref{extra signal information}). Note that @code{$_siginfo}
10370 could be empty, if the application has not yet received any signals.
10371 For example, it will be empty before you execute the @code{run} command.
10374 @vindex $_tlb@r{, convenience variable}
10375 The variable @code{$_tlb} is automatically set when debugging
10376 applications running on MS-Windows in native mode or connected to
10377 gdbserver that supports the @code{qGetTIBAddr} request.
10378 @xref{General Query Packets}.
10379 This variable contains the address of the thread information block.
10383 @node Convenience Funs
10384 @section Convenience Functions
10386 @cindex convenience functions
10387 @value{GDBN} also supplies some @dfn{convenience functions}. These
10388 have a syntax similar to convenience variables. A convenience
10389 function can be used in an expression just like an ordinary function;
10390 however, a convenience function is implemented internally to
10393 These functions do not require @value{GDBN} to be configured with
10394 @code{Python} support, which means that they are always available.
10398 @item $_isvoid (@var{expr})
10399 @findex $_isvoid@r{, convenience function}
10400 Return one if the expression @var{expr} is @code{void}. Otherwise it
10403 A @code{void} expression is an expression where the type of the result
10404 is @code{void}. For example, you can examine a convenience variable
10405 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10409 (@value{GDBP}) print $_exitcode
10411 (@value{GDBP}) print $_isvoid ($_exitcode)
10414 Starting program: ./a.out
10415 [Inferior 1 (process 29572) exited normally]
10416 (@value{GDBP}) print $_exitcode
10418 (@value{GDBP}) print $_isvoid ($_exitcode)
10422 In the example above, we used @code{$_isvoid} to check whether
10423 @code{$_exitcode} is @code{void} before and after the execution of the
10424 program being debugged. Before the execution there is no exit code to
10425 be examined, therefore @code{$_exitcode} is @code{void}. After the
10426 execution the program being debugged returned zero, therefore
10427 @code{$_exitcode} is zero, which means that it is not @code{void}
10430 The @code{void} expression can also be a call of a function from the
10431 program being debugged. For example, given the following function:
10440 The result of calling it inside @value{GDBN} is @code{void}:
10443 (@value{GDBP}) print foo ()
10445 (@value{GDBP}) print $_isvoid (foo ())
10447 (@value{GDBP}) set $v = foo ()
10448 (@value{GDBP}) print $v
10450 (@value{GDBP}) print $_isvoid ($v)
10456 These functions require @value{GDBN} to be configured with
10457 @code{Python} support.
10461 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10462 @findex $_memeq@r{, convenience function}
10463 Returns one if the @var{length} bytes at the addresses given by
10464 @var{buf1} and @var{buf2} are equal.
10465 Otherwise it returns zero.
10467 @item $_regex(@var{str}, @var{regex})
10468 @findex $_regex@r{, convenience function}
10469 Returns one if the string @var{str} matches the regular expression
10470 @var{regex}. Otherwise it returns zero.
10471 The syntax of the regular expression is that specified by @code{Python}'s
10472 regular expression support.
10474 @item $_streq(@var{str1}, @var{str2})
10475 @findex $_streq@r{, convenience function}
10476 Returns one if the strings @var{str1} and @var{str2} are equal.
10477 Otherwise it returns zero.
10479 @item $_strlen(@var{str})
10480 @findex $_strlen@r{, convenience function}
10481 Returns the length of string @var{str}.
10483 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10484 @findex $_caller_is@r{, convenience function}
10485 Returns one if the calling function's name is equal to @var{name}.
10486 Otherwise it returns zero.
10488 If the optional argument @var{number_of_frames} is provided,
10489 it is the number of frames up in the stack to look.
10497 at testsuite/gdb.python/py-caller-is.c:21
10498 #1 0x00000000004005a0 in middle_func ()
10499 at testsuite/gdb.python/py-caller-is.c:27
10500 #2 0x00000000004005ab in top_func ()
10501 at testsuite/gdb.python/py-caller-is.c:33
10502 #3 0x00000000004005b6 in main ()
10503 at testsuite/gdb.python/py-caller-is.c:39
10504 (gdb) print $_caller_is ("middle_func")
10506 (gdb) print $_caller_is ("top_func", 2)
10510 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10511 @findex $_caller_matches@r{, convenience function}
10512 Returns one if the calling function's name matches the regular expression
10513 @var{regexp}. Otherwise it returns zero.
10515 If the optional argument @var{number_of_frames} is provided,
10516 it is the number of frames up in the stack to look.
10519 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10520 @findex $_any_caller_is@r{, convenience function}
10521 Returns one if any calling function's name is equal to @var{name}.
10522 Otherwise it returns zero.
10524 If the optional argument @var{number_of_frames} is provided,
10525 it is the number of frames up in the stack to look.
10528 This function differs from @code{$_caller_is} in that this function
10529 checks all stack frames from the immediate caller to the frame specified
10530 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10531 frame specified by @var{number_of_frames}.
10533 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10534 @findex $_any_caller_matches@r{, convenience function}
10535 Returns one if any calling function's name matches the regular expression
10536 @var{regexp}. Otherwise it returns zero.
10538 If the optional argument @var{number_of_frames} is provided,
10539 it is the number of frames up in the stack to look.
10542 This function differs from @code{$_caller_matches} in that this function
10543 checks all stack frames from the immediate caller to the frame specified
10544 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10545 frame specified by @var{number_of_frames}.
10549 @value{GDBN} provides the ability to list and get help on
10550 convenience functions.
10553 @item help function
10554 @kindex help function
10555 @cindex show all convenience functions
10556 Print a list of all convenience functions.
10563 You can refer to machine register contents, in expressions, as variables
10564 with names starting with @samp{$}. The names of registers are different
10565 for each machine; use @code{info registers} to see the names used on
10569 @kindex info registers
10570 @item info registers
10571 Print the names and values of all registers except floating-point
10572 and vector registers (in the selected stack frame).
10574 @kindex info all-registers
10575 @cindex floating point registers
10576 @item info all-registers
10577 Print the names and values of all registers, including floating-point
10578 and vector registers (in the selected stack frame).
10580 @item info registers @var{regname} @dots{}
10581 Print the @dfn{relativized} value of each specified register @var{regname}.
10582 As discussed in detail below, register values are normally relative to
10583 the selected stack frame. The @var{regname} may be any register name valid on
10584 the machine you are using, with or without the initial @samp{$}.
10587 @anchor{standard registers}
10588 @cindex stack pointer register
10589 @cindex program counter register
10590 @cindex process status register
10591 @cindex frame pointer register
10592 @cindex standard registers
10593 @value{GDBN} has four ``standard'' register names that are available (in
10594 expressions) on most machines---whenever they do not conflict with an
10595 architecture's canonical mnemonics for registers. The register names
10596 @code{$pc} and @code{$sp} are used for the program counter register and
10597 the stack pointer. @code{$fp} is used for a register that contains a
10598 pointer to the current stack frame, and @code{$ps} is used for a
10599 register that contains the processor status. For example,
10600 you could print the program counter in hex with
10607 or print the instruction to be executed next with
10614 or add four to the stack pointer@footnote{This is a way of removing
10615 one word from the stack, on machines where stacks grow downward in
10616 memory (most machines, nowadays). This assumes that the innermost
10617 stack frame is selected; setting @code{$sp} is not allowed when other
10618 stack frames are selected. To pop entire frames off the stack,
10619 regardless of machine architecture, use @code{return};
10620 see @ref{Returning, ,Returning from a Function}.} with
10626 Whenever possible, these four standard register names are available on
10627 your machine even though the machine has different canonical mnemonics,
10628 so long as there is no conflict. The @code{info registers} command
10629 shows the canonical names. For example, on the SPARC, @code{info
10630 registers} displays the processor status register as @code{$psr} but you
10631 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10632 is an alias for the @sc{eflags} register.
10634 @value{GDBN} always considers the contents of an ordinary register as an
10635 integer when the register is examined in this way. Some machines have
10636 special registers which can hold nothing but floating point; these
10637 registers are considered to have floating point values. There is no way
10638 to refer to the contents of an ordinary register as floating point value
10639 (although you can @emph{print} it as a floating point value with
10640 @samp{print/f $@var{regname}}).
10642 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10643 means that the data format in which the register contents are saved by
10644 the operating system is not the same one that your program normally
10645 sees. For example, the registers of the 68881 floating point
10646 coprocessor are always saved in ``extended'' (raw) format, but all C
10647 programs expect to work with ``double'' (virtual) format. In such
10648 cases, @value{GDBN} normally works with the virtual format only (the format
10649 that makes sense for your program), but the @code{info registers} command
10650 prints the data in both formats.
10652 @cindex SSE registers (x86)
10653 @cindex MMX registers (x86)
10654 Some machines have special registers whose contents can be interpreted
10655 in several different ways. For example, modern x86-based machines
10656 have SSE and MMX registers that can hold several values packed
10657 together in several different formats. @value{GDBN} refers to such
10658 registers in @code{struct} notation:
10661 (@value{GDBP}) print $xmm1
10663 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10664 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10665 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10666 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10667 v4_int32 = @{0, 20657912, 11, 13@},
10668 v2_int64 = @{88725056443645952, 55834574859@},
10669 uint128 = 0x0000000d0000000b013b36f800000000
10674 To set values of such registers, you need to tell @value{GDBN} which
10675 view of the register you wish to change, as if you were assigning
10676 value to a @code{struct} member:
10679 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10682 Normally, register values are relative to the selected stack frame
10683 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10684 value that the register would contain if all stack frames farther in
10685 were exited and their saved registers restored. In order to see the
10686 true contents of hardware registers, you must select the innermost
10687 frame (with @samp{frame 0}).
10689 @cindex caller-saved registers
10690 @cindex call-clobbered registers
10691 @cindex volatile registers
10692 @cindex <not saved> values
10693 Usually ABIs reserve some registers as not needed to be saved by the
10694 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10695 registers). It may therefore not be possible for @value{GDBN} to know
10696 the value a register had before the call (in other words, in the outer
10697 frame), if the register value has since been changed by the callee.
10698 @value{GDBN} tries to deduce where the inner frame saved
10699 (``callee-saved'') registers, from the debug info, unwind info, or the
10700 machine code generated by your compiler. If some register is not
10701 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10702 its own knowledge of the ABI, or because the debug/unwind info
10703 explicitly says the register's value is undefined), @value{GDBN}
10704 displays @w{@samp{<not saved>}} as the register's value. With targets
10705 that @value{GDBN} has no knowledge of the register saving convention,
10706 if a register was not saved by the callee, then its value and location
10707 in the outer frame are assumed to be the same of the inner frame.
10708 This is usually harmless, because if the register is call-clobbered,
10709 the caller either does not care what is in the register after the
10710 call, or has code to restore the value that it does care about. Note,
10711 however, that if you change such a register in the outer frame, you
10712 may also be affecting the inner frame. Also, the more ``outer'' the
10713 frame is you're looking at, the more likely a call-clobbered
10714 register's value is to be wrong, in the sense that it doesn't actually
10715 represent the value the register had just before the call.
10717 @node Floating Point Hardware
10718 @section Floating Point Hardware
10719 @cindex floating point
10721 Depending on the configuration, @value{GDBN} may be able to give
10722 you more information about the status of the floating point hardware.
10727 Display hardware-dependent information about the floating
10728 point unit. The exact contents and layout vary depending on the
10729 floating point chip. Currently, @samp{info float} is supported on
10730 the ARM and x86 machines.
10734 @section Vector Unit
10735 @cindex vector unit
10737 Depending on the configuration, @value{GDBN} may be able to give you
10738 more information about the status of the vector unit.
10741 @kindex info vector
10743 Display information about the vector unit. The exact contents and
10744 layout vary depending on the hardware.
10747 @node OS Information
10748 @section Operating System Auxiliary Information
10749 @cindex OS information
10751 @value{GDBN} provides interfaces to useful OS facilities that can help
10752 you debug your program.
10754 @cindex auxiliary vector
10755 @cindex vector, auxiliary
10756 Some operating systems supply an @dfn{auxiliary vector} to programs at
10757 startup. This is akin to the arguments and environment that you
10758 specify for a program, but contains a system-dependent variety of
10759 binary values that tell system libraries important details about the
10760 hardware, operating system, and process. Each value's purpose is
10761 identified by an integer tag; the meanings are well-known but system-specific.
10762 Depending on the configuration and operating system facilities,
10763 @value{GDBN} may be able to show you this information. For remote
10764 targets, this functionality may further depend on the remote stub's
10765 support of the @samp{qXfer:auxv:read} packet, see
10766 @ref{qXfer auxiliary vector read}.
10771 Display the auxiliary vector of the inferior, which can be either a
10772 live process or a core dump file. @value{GDBN} prints each tag value
10773 numerically, and also shows names and text descriptions for recognized
10774 tags. Some values in the vector are numbers, some bit masks, and some
10775 pointers to strings or other data. @value{GDBN} displays each value in the
10776 most appropriate form for a recognized tag, and in hexadecimal for
10777 an unrecognized tag.
10780 On some targets, @value{GDBN} can access operating system-specific
10781 information and show it to you. The types of information available
10782 will differ depending on the type of operating system running on the
10783 target. The mechanism used to fetch the data is described in
10784 @ref{Operating System Information}. For remote targets, this
10785 functionality depends on the remote stub's support of the
10786 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10790 @item info os @var{infotype}
10792 Display OS information of the requested type.
10794 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10796 @anchor{linux info os infotypes}
10798 @kindex info os cpus
10800 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
10801 the available fields from /proc/cpuinfo. For each supported architecture
10802 different fields are available. Two common entries are processor which gives
10803 CPU number and bogomips; a system constant that is calculated during
10804 kernel initialization.
10806 @kindex info os files
10808 Display the list of open file descriptors on the target. For each
10809 file descriptor, @value{GDBN} prints the identifier of the process
10810 owning the descriptor, the command of the owning process, the value
10811 of the descriptor, and the target of the descriptor.
10813 @kindex info os modules
10815 Display the list of all loaded kernel modules on the target. For each
10816 module, @value{GDBN} prints the module name, the size of the module in
10817 bytes, the number of times the module is used, the dependencies of the
10818 module, the status of the module, and the address of the loaded module
10821 @kindex info os msg
10823 Display the list of all System V message queues on the target. For each
10824 message queue, @value{GDBN} prints the message queue key, the message
10825 queue identifier, the access permissions, the current number of bytes
10826 on the queue, the current number of messages on the queue, the processes
10827 that last sent and received a message on the queue, the user and group
10828 of the owner and creator of the message queue, the times at which a
10829 message was last sent and received on the queue, and the time at which
10830 the message queue was last changed.
10832 @kindex info os processes
10834 Display the list of processes on the target. For each process,
10835 @value{GDBN} prints the process identifier, the name of the user, the
10836 command corresponding to the process, and the list of processor cores
10837 that the process is currently running on. (To understand what these
10838 properties mean, for this and the following info types, please consult
10839 the general @sc{gnu}/Linux documentation.)
10841 @kindex info os procgroups
10843 Display the list of process groups on the target. For each process,
10844 @value{GDBN} prints the identifier of the process group that it belongs
10845 to, the command corresponding to the process group leader, the process
10846 identifier, and the command line of the process. The list is sorted
10847 first by the process group identifier, then by the process identifier,
10848 so that processes belonging to the same process group are grouped together
10849 and the process group leader is listed first.
10851 @kindex info os semaphores
10853 Display the list of all System V semaphore sets on the target. For each
10854 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10855 set identifier, the access permissions, the number of semaphores in the
10856 set, the user and group of the owner and creator of the semaphore set,
10857 and the times at which the semaphore set was operated upon and changed.
10859 @kindex info os shm
10861 Display the list of all System V shared-memory regions on the target.
10862 For each shared-memory region, @value{GDBN} prints the region key,
10863 the shared-memory identifier, the access permissions, the size of the
10864 region, the process that created the region, the process that last
10865 attached to or detached from the region, the current number of live
10866 attaches to the region, and the times at which the region was last
10867 attached to, detach from, and changed.
10869 @kindex info os sockets
10871 Display the list of Internet-domain sockets on the target. For each
10872 socket, @value{GDBN} prints the address and port of the local and
10873 remote endpoints, the current state of the connection, the creator of
10874 the socket, the IP address family of the socket, and the type of the
10877 @kindex info os threads
10879 Display the list of threads running on the target. For each thread,
10880 @value{GDBN} prints the identifier of the process that the thread
10881 belongs to, the command of the process, the thread identifier, and the
10882 processor core that it is currently running on. The main thread of a
10883 process is not listed.
10887 If @var{infotype} is omitted, then list the possible values for
10888 @var{infotype} and the kind of OS information available for each
10889 @var{infotype}. If the target does not return a list of possible
10890 types, this command will report an error.
10893 @node Memory Region Attributes
10894 @section Memory Region Attributes
10895 @cindex memory region attributes
10897 @dfn{Memory region attributes} allow you to describe special handling
10898 required by regions of your target's memory. @value{GDBN} uses
10899 attributes to determine whether to allow certain types of memory
10900 accesses; whether to use specific width accesses; and whether to cache
10901 target memory. By default the description of memory regions is
10902 fetched from the target (if the current target supports this), but the
10903 user can override the fetched regions.
10905 Defined memory regions can be individually enabled and disabled. When a
10906 memory region is disabled, @value{GDBN} uses the default attributes when
10907 accessing memory in that region. Similarly, if no memory regions have
10908 been defined, @value{GDBN} uses the default attributes when accessing
10911 When a memory region is defined, it is given a number to identify it;
10912 to enable, disable, or remove a memory region, you specify that number.
10916 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10917 Define a memory region bounded by @var{lower} and @var{upper} with
10918 attributes @var{attributes}@dots{}, and add it to the list of regions
10919 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10920 case: it is treated as the target's maximum memory address.
10921 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10924 Discard any user changes to the memory regions and use target-supplied
10925 regions, if available, or no regions if the target does not support.
10928 @item delete mem @var{nums}@dots{}
10929 Remove memory regions @var{nums}@dots{} from the list of regions
10930 monitored by @value{GDBN}.
10932 @kindex disable mem
10933 @item disable mem @var{nums}@dots{}
10934 Disable monitoring of memory regions @var{nums}@dots{}.
10935 A disabled memory region is not forgotten.
10936 It may be enabled again later.
10939 @item enable mem @var{nums}@dots{}
10940 Enable monitoring of memory regions @var{nums}@dots{}.
10944 Print a table of all defined memory regions, with the following columns
10948 @item Memory Region Number
10949 @item Enabled or Disabled.
10950 Enabled memory regions are marked with @samp{y}.
10951 Disabled memory regions are marked with @samp{n}.
10954 The address defining the inclusive lower bound of the memory region.
10957 The address defining the exclusive upper bound of the memory region.
10960 The list of attributes set for this memory region.
10965 @subsection Attributes
10967 @subsubsection Memory Access Mode
10968 The access mode attributes set whether @value{GDBN} may make read or
10969 write accesses to a memory region.
10971 While these attributes prevent @value{GDBN} from performing invalid
10972 memory accesses, they do nothing to prevent the target system, I/O DMA,
10973 etc.@: from accessing memory.
10977 Memory is read only.
10979 Memory is write only.
10981 Memory is read/write. This is the default.
10984 @subsubsection Memory Access Size
10985 The access size attribute tells @value{GDBN} to use specific sized
10986 accesses in the memory region. Often memory mapped device registers
10987 require specific sized accesses. If no access size attribute is
10988 specified, @value{GDBN} may use accesses of any size.
10992 Use 8 bit memory accesses.
10994 Use 16 bit memory accesses.
10996 Use 32 bit memory accesses.
10998 Use 64 bit memory accesses.
11001 @c @subsubsection Hardware/Software Breakpoints
11002 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11003 @c will use hardware or software breakpoints for the internal breakpoints
11004 @c used by the step, next, finish, until, etc. commands.
11008 @c Always use hardware breakpoints
11009 @c @item swbreak (default)
11012 @subsubsection Data Cache
11013 The data cache attributes set whether @value{GDBN} will cache target
11014 memory. While this generally improves performance by reducing debug
11015 protocol overhead, it can lead to incorrect results because @value{GDBN}
11016 does not know about volatile variables or memory mapped device
11021 Enable @value{GDBN} to cache target memory.
11023 Disable @value{GDBN} from caching target memory. This is the default.
11026 @subsection Memory Access Checking
11027 @value{GDBN} can be instructed to refuse accesses to memory that is
11028 not explicitly described. This can be useful if accessing such
11029 regions has undesired effects for a specific target, or to provide
11030 better error checking. The following commands control this behaviour.
11033 @kindex set mem inaccessible-by-default
11034 @item set mem inaccessible-by-default [on|off]
11035 If @code{on} is specified, make @value{GDBN} treat memory not
11036 explicitly described by the memory ranges as non-existent and refuse accesses
11037 to such memory. The checks are only performed if there's at least one
11038 memory range defined. If @code{off} is specified, make @value{GDBN}
11039 treat the memory not explicitly described by the memory ranges as RAM.
11040 The default value is @code{on}.
11041 @kindex show mem inaccessible-by-default
11042 @item show mem inaccessible-by-default
11043 Show the current handling of accesses to unknown memory.
11047 @c @subsubsection Memory Write Verification
11048 @c The memory write verification attributes set whether @value{GDBN}
11049 @c will re-reads data after each write to verify the write was successful.
11053 @c @item noverify (default)
11056 @node Dump/Restore Files
11057 @section Copy Between Memory and a File
11058 @cindex dump/restore files
11059 @cindex append data to a file
11060 @cindex dump data to a file
11061 @cindex restore data from a file
11063 You can use the commands @code{dump}, @code{append}, and
11064 @code{restore} to copy data between target memory and a file. The
11065 @code{dump} and @code{append} commands write data to a file, and the
11066 @code{restore} command reads data from a file back into the inferior's
11067 memory. Files may be in binary, Motorola S-record, Intel hex,
11068 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11069 append to binary files, and cannot read from Verilog Hex files.
11074 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11075 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11076 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11077 or the value of @var{expr}, to @var{filename} in the given format.
11079 The @var{format} parameter may be any one of:
11086 Motorola S-record format.
11088 Tektronix Hex format.
11090 Verilog Hex format.
11093 @value{GDBN} uses the same definitions of these formats as the
11094 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11095 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11099 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11100 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11101 Append the contents of memory from @var{start_addr} to @var{end_addr},
11102 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11103 (@value{GDBN} can only append data to files in raw binary form.)
11106 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11107 Restore the contents of file @var{filename} into memory. The
11108 @code{restore} command can automatically recognize any known @sc{bfd}
11109 file format, except for raw binary. To restore a raw binary file you
11110 must specify the optional keyword @code{binary} after the filename.
11112 If @var{bias} is non-zero, its value will be added to the addresses
11113 contained in the file. Binary files always start at address zero, so
11114 they will be restored at address @var{bias}. Other bfd files have
11115 a built-in location; they will be restored at offset @var{bias}
11116 from that location.
11118 If @var{start} and/or @var{end} are non-zero, then only data between
11119 file offset @var{start} and file offset @var{end} will be restored.
11120 These offsets are relative to the addresses in the file, before
11121 the @var{bias} argument is applied.
11125 @node Core File Generation
11126 @section How to Produce a Core File from Your Program
11127 @cindex dump core from inferior
11129 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11130 image of a running process and its process status (register values
11131 etc.). Its primary use is post-mortem debugging of a program that
11132 crashed while it ran outside a debugger. A program that crashes
11133 automatically produces a core file, unless this feature is disabled by
11134 the user. @xref{Files}, for information on invoking @value{GDBN} in
11135 the post-mortem debugging mode.
11137 Occasionally, you may wish to produce a core file of the program you
11138 are debugging in order to preserve a snapshot of its state.
11139 @value{GDBN} has a special command for that.
11143 @kindex generate-core-file
11144 @item generate-core-file [@var{file}]
11145 @itemx gcore [@var{file}]
11146 Produce a core dump of the inferior process. The optional argument
11147 @var{file} specifies the file name where to put the core dump. If not
11148 specified, the file name defaults to @file{core.@var{pid}}, where
11149 @var{pid} is the inferior process ID.
11151 Note that this command is implemented only for some systems (as of
11152 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11154 On @sc{gnu}/Linux, this command can take into account the value of the
11155 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11156 dump (@pxref{set use-coredump-filter}).
11158 @kindex set use-coredump-filter
11159 @anchor{set use-coredump-filter}
11160 @item set use-coredump-filter on
11161 @itemx set use-coredump-filter off
11162 Enable or disable the use of the file
11163 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11164 files. This file is used by the Linux kernel to decide what types of
11165 memory mappings will be dumped or ignored when generating a core dump
11166 file. @var{pid} is the process ID of a currently running process.
11168 To make use of this feature, you have to write in the
11169 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11170 which is a bit mask representing the memory mapping types. If a bit
11171 is set in the bit mask, then the memory mappings of the corresponding
11172 types will be dumped; otherwise, they will be ignored. This
11173 configuration is inherited by child processes. For more information
11174 about the bits that can be set in the
11175 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11176 manpage of @code{core(5)}.
11178 By default, this option is @code{on}. If this option is turned
11179 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11180 and instead uses the same default value as the Linux kernel in order
11181 to decide which pages will be dumped in the core dump file. This
11182 value is currently @code{0x33}, which means that bits @code{0}
11183 (anonymous private mappings), @code{1} (anonymous shared mappings),
11184 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11185 This will cause these memory mappings to be dumped automatically.
11188 @node Character Sets
11189 @section Character Sets
11190 @cindex character sets
11192 @cindex translating between character sets
11193 @cindex host character set
11194 @cindex target character set
11196 If the program you are debugging uses a different character set to
11197 represent characters and strings than the one @value{GDBN} uses itself,
11198 @value{GDBN} can automatically translate between the character sets for
11199 you. The character set @value{GDBN} uses we call the @dfn{host
11200 character set}; the one the inferior program uses we call the
11201 @dfn{target character set}.
11203 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11204 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11205 remote protocol (@pxref{Remote Debugging}) to debug a program
11206 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11207 then the host character set is Latin-1, and the target character set is
11208 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11209 target-charset EBCDIC-US}, then @value{GDBN} translates between
11210 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11211 character and string literals in expressions.
11213 @value{GDBN} has no way to automatically recognize which character set
11214 the inferior program uses; you must tell it, using the @code{set
11215 target-charset} command, described below.
11217 Here are the commands for controlling @value{GDBN}'s character set
11221 @item set target-charset @var{charset}
11222 @kindex set target-charset
11223 Set the current target character set to @var{charset}. To display the
11224 list of supported target character sets, type
11225 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11227 @item set host-charset @var{charset}
11228 @kindex set host-charset
11229 Set the current host character set to @var{charset}.
11231 By default, @value{GDBN} uses a host character set appropriate to the
11232 system it is running on; you can override that default using the
11233 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11234 automatically determine the appropriate host character set. In this
11235 case, @value{GDBN} uses @samp{UTF-8}.
11237 @value{GDBN} can only use certain character sets as its host character
11238 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11239 @value{GDBN} will list the host character sets it supports.
11241 @item set charset @var{charset}
11242 @kindex set charset
11243 Set the current host and target character sets to @var{charset}. As
11244 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11245 @value{GDBN} will list the names of the character sets that can be used
11246 for both host and target.
11249 @kindex show charset
11250 Show the names of the current host and target character sets.
11252 @item show host-charset
11253 @kindex show host-charset
11254 Show the name of the current host character set.
11256 @item show target-charset
11257 @kindex show target-charset
11258 Show the name of the current target character set.
11260 @item set target-wide-charset @var{charset}
11261 @kindex set target-wide-charset
11262 Set the current target's wide character set to @var{charset}. This is
11263 the character set used by the target's @code{wchar_t} type. To
11264 display the list of supported wide character sets, type
11265 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11267 @item show target-wide-charset
11268 @kindex show target-wide-charset
11269 Show the name of the current target's wide character set.
11272 Here is an example of @value{GDBN}'s character set support in action.
11273 Assume that the following source code has been placed in the file
11274 @file{charset-test.c}:
11280 = @{72, 101, 108, 108, 111, 44, 32, 119,
11281 111, 114, 108, 100, 33, 10, 0@};
11282 char ibm1047_hello[]
11283 = @{200, 133, 147, 147, 150, 107, 64, 166,
11284 150, 153, 147, 132, 90, 37, 0@};
11288 printf ("Hello, world!\n");
11292 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11293 containing the string @samp{Hello, world!} followed by a newline,
11294 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11296 We compile the program, and invoke the debugger on it:
11299 $ gcc -g charset-test.c -o charset-test
11300 $ gdb -nw charset-test
11301 GNU gdb 2001-12-19-cvs
11302 Copyright 2001 Free Software Foundation, Inc.
11307 We can use the @code{show charset} command to see what character sets
11308 @value{GDBN} is currently using to interpret and display characters and
11312 (@value{GDBP}) show charset
11313 The current host and target character set is `ISO-8859-1'.
11317 For the sake of printing this manual, let's use @sc{ascii} as our
11318 initial character set:
11320 (@value{GDBP}) set charset ASCII
11321 (@value{GDBP}) show charset
11322 The current host and target character set is `ASCII'.
11326 Let's assume that @sc{ascii} is indeed the correct character set for our
11327 host system --- in other words, let's assume that if @value{GDBN} prints
11328 characters using the @sc{ascii} character set, our terminal will display
11329 them properly. Since our current target character set is also
11330 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11333 (@value{GDBP}) print ascii_hello
11334 $1 = 0x401698 "Hello, world!\n"
11335 (@value{GDBP}) print ascii_hello[0]
11340 @value{GDBN} uses the target character set for character and string
11341 literals you use in expressions:
11344 (@value{GDBP}) print '+'
11349 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11352 @value{GDBN} relies on the user to tell it which character set the
11353 target program uses. If we print @code{ibm1047_hello} while our target
11354 character set is still @sc{ascii}, we get jibberish:
11357 (@value{GDBP}) print ibm1047_hello
11358 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11359 (@value{GDBP}) print ibm1047_hello[0]
11364 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11365 @value{GDBN} tells us the character sets it supports:
11368 (@value{GDBP}) set target-charset
11369 ASCII EBCDIC-US IBM1047 ISO-8859-1
11370 (@value{GDBP}) set target-charset
11373 We can select @sc{ibm1047} as our target character set, and examine the
11374 program's strings again. Now the @sc{ascii} string is wrong, but
11375 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11376 target character set, @sc{ibm1047}, to the host character set,
11377 @sc{ascii}, and they display correctly:
11380 (@value{GDBP}) set target-charset IBM1047
11381 (@value{GDBP}) show charset
11382 The current host character set is `ASCII'.
11383 The current target character set is `IBM1047'.
11384 (@value{GDBP}) print ascii_hello
11385 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11386 (@value{GDBP}) print ascii_hello[0]
11388 (@value{GDBP}) print ibm1047_hello
11389 $8 = 0x4016a8 "Hello, world!\n"
11390 (@value{GDBP}) print ibm1047_hello[0]
11395 As above, @value{GDBN} uses the target character set for character and
11396 string literals you use in expressions:
11399 (@value{GDBP}) print '+'
11404 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11407 @node Caching Target Data
11408 @section Caching Data of Targets
11409 @cindex caching data of targets
11411 @value{GDBN} caches data exchanged between the debugger and a target.
11412 Each cache is associated with the address space of the inferior.
11413 @xref{Inferiors and Programs}, about inferior and address space.
11414 Such caching generally improves performance in remote debugging
11415 (@pxref{Remote Debugging}), because it reduces the overhead of the
11416 remote protocol by bundling memory reads and writes into large chunks.
11417 Unfortunately, simply caching everything would lead to incorrect results,
11418 since @value{GDBN} does not necessarily know anything about volatile
11419 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11420 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11422 Therefore, by default, @value{GDBN} only caches data
11423 known to be on the stack@footnote{In non-stop mode, it is moderately
11424 rare for a running thread to modify the stack of a stopped thread
11425 in a way that would interfere with a backtrace, and caching of
11426 stack reads provides a significant speed up of remote backtraces.} or
11427 in the code segment.
11428 Other regions of memory can be explicitly marked as
11429 cacheable; @pxref{Memory Region Attributes}.
11432 @kindex set remotecache
11433 @item set remotecache on
11434 @itemx set remotecache off
11435 This option no longer does anything; it exists for compatibility
11438 @kindex show remotecache
11439 @item show remotecache
11440 Show the current state of the obsolete remotecache flag.
11442 @kindex set stack-cache
11443 @item set stack-cache on
11444 @itemx set stack-cache off
11445 Enable or disable caching of stack accesses. When @code{on}, use
11446 caching. By default, this option is @code{on}.
11448 @kindex show stack-cache
11449 @item show stack-cache
11450 Show the current state of data caching for memory accesses.
11452 @kindex set code-cache
11453 @item set code-cache on
11454 @itemx set code-cache off
11455 Enable or disable caching of code segment accesses. When @code{on},
11456 use caching. By default, this option is @code{on}. This improves
11457 performance of disassembly in remote debugging.
11459 @kindex show code-cache
11460 @item show code-cache
11461 Show the current state of target memory cache for code segment
11464 @kindex info dcache
11465 @item info dcache @r{[}line@r{]}
11466 Print the information about the performance of data cache of the
11467 current inferior's address space. The information displayed
11468 includes the dcache width and depth, and for each cache line, its
11469 number, address, and how many times it was referenced. This
11470 command is useful for debugging the data cache operation.
11472 If a line number is specified, the contents of that line will be
11475 @item set dcache size @var{size}
11476 @cindex dcache size
11477 @kindex set dcache size
11478 Set maximum number of entries in dcache (dcache depth above).
11480 @item set dcache line-size @var{line-size}
11481 @cindex dcache line-size
11482 @kindex set dcache line-size
11483 Set number of bytes each dcache entry caches (dcache width above).
11484 Must be a power of 2.
11486 @item show dcache size
11487 @kindex show dcache size
11488 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11490 @item show dcache line-size
11491 @kindex show dcache line-size
11492 Show default size of dcache lines.
11496 @node Searching Memory
11497 @section Search Memory
11498 @cindex searching memory
11500 Memory can be searched for a particular sequence of bytes with the
11501 @code{find} command.
11505 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11506 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11507 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11508 etc. The search begins at address @var{start_addr} and continues for either
11509 @var{len} bytes or through to @var{end_addr} inclusive.
11512 @var{s} and @var{n} are optional parameters.
11513 They may be specified in either order, apart or together.
11516 @item @var{s}, search query size
11517 The size of each search query value.
11523 halfwords (two bytes)
11527 giant words (eight bytes)
11530 All values are interpreted in the current language.
11531 This means, for example, that if the current source language is C/C@t{++}
11532 then searching for the string ``hello'' includes the trailing '\0'.
11534 If the value size is not specified, it is taken from the
11535 value's type in the current language.
11536 This is useful when one wants to specify the search
11537 pattern as a mixture of types.
11538 Note that this means, for example, that in the case of C-like languages
11539 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11540 which is typically four bytes.
11542 @item @var{n}, maximum number of finds
11543 The maximum number of matches to print. The default is to print all finds.
11546 You can use strings as search values. Quote them with double-quotes
11548 The string value is copied into the search pattern byte by byte,
11549 regardless of the endianness of the target and the size specification.
11551 The address of each match found is printed as well as a count of the
11552 number of matches found.
11554 The address of the last value found is stored in convenience variable
11556 A count of the number of matches is stored in @samp{$numfound}.
11558 For example, if stopped at the @code{printf} in this function:
11564 static char hello[] = "hello-hello";
11565 static struct @{ char c; short s; int i; @}
11566 __attribute__ ((packed)) mixed
11567 = @{ 'c', 0x1234, 0x87654321 @};
11568 printf ("%s\n", hello);
11573 you get during debugging:
11576 (gdb) find &hello[0], +sizeof(hello), "hello"
11577 0x804956d <hello.1620+6>
11579 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11580 0x8049567 <hello.1620>
11581 0x804956d <hello.1620+6>
11583 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11584 0x8049567 <hello.1620>
11586 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11587 0x8049560 <mixed.1625>
11589 (gdb) print $numfound
11592 $2 = (void *) 0x8049560
11595 @node Optimized Code
11596 @chapter Debugging Optimized Code
11597 @cindex optimized code, debugging
11598 @cindex debugging optimized code
11600 Almost all compilers support optimization. With optimization
11601 disabled, the compiler generates assembly code that corresponds
11602 directly to your source code, in a simplistic way. As the compiler
11603 applies more powerful optimizations, the generated assembly code
11604 diverges from your original source code. With help from debugging
11605 information generated by the compiler, @value{GDBN} can map from
11606 the running program back to constructs from your original source.
11608 @value{GDBN} is more accurate with optimization disabled. If you
11609 can recompile without optimization, it is easier to follow the
11610 progress of your program during debugging. But, there are many cases
11611 where you may need to debug an optimized version.
11613 When you debug a program compiled with @samp{-g -O}, remember that the
11614 optimizer has rearranged your code; the debugger shows you what is
11615 really there. Do not be too surprised when the execution path does not
11616 exactly match your source file! An extreme example: if you define a
11617 variable, but never use it, @value{GDBN} never sees that
11618 variable---because the compiler optimizes it out of existence.
11620 Some things do not work as well with @samp{-g -O} as with just
11621 @samp{-g}, particularly on machines with instruction scheduling. If in
11622 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11623 please report it to us as a bug (including a test case!).
11624 @xref{Variables}, for more information about debugging optimized code.
11627 * Inline Functions:: How @value{GDBN} presents inlining
11628 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11631 @node Inline Functions
11632 @section Inline Functions
11633 @cindex inline functions, debugging
11635 @dfn{Inlining} is an optimization that inserts a copy of the function
11636 body directly at each call site, instead of jumping to a shared
11637 routine. @value{GDBN} displays inlined functions just like
11638 non-inlined functions. They appear in backtraces. You can view their
11639 arguments and local variables, step into them with @code{step}, skip
11640 them with @code{next}, and escape from them with @code{finish}.
11641 You can check whether a function was inlined by using the
11642 @code{info frame} command.
11644 For @value{GDBN} to support inlined functions, the compiler must
11645 record information about inlining in the debug information ---
11646 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11647 other compilers do also. @value{GDBN} only supports inlined functions
11648 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11649 do not emit two required attributes (@samp{DW_AT_call_file} and
11650 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11651 function calls with earlier versions of @value{NGCC}. It instead
11652 displays the arguments and local variables of inlined functions as
11653 local variables in the caller.
11655 The body of an inlined function is directly included at its call site;
11656 unlike a non-inlined function, there are no instructions devoted to
11657 the call. @value{GDBN} still pretends that the call site and the
11658 start of the inlined function are different instructions. Stepping to
11659 the call site shows the call site, and then stepping again shows
11660 the first line of the inlined function, even though no additional
11661 instructions are executed.
11663 This makes source-level debugging much clearer; you can see both the
11664 context of the call and then the effect of the call. Only stepping by
11665 a single instruction using @code{stepi} or @code{nexti} does not do
11666 this; single instruction steps always show the inlined body.
11668 There are some ways that @value{GDBN} does not pretend that inlined
11669 function calls are the same as normal calls:
11673 Setting breakpoints at the call site of an inlined function may not
11674 work, because the call site does not contain any code. @value{GDBN}
11675 may incorrectly move the breakpoint to the next line of the enclosing
11676 function, after the call. This limitation will be removed in a future
11677 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11678 or inside the inlined function instead.
11681 @value{GDBN} cannot locate the return value of inlined calls after
11682 using the @code{finish} command. This is a limitation of compiler-generated
11683 debugging information; after @code{finish}, you can step to the next line
11684 and print a variable where your program stored the return value.
11688 @node Tail Call Frames
11689 @section Tail Call Frames
11690 @cindex tail call frames, debugging
11692 Function @code{B} can call function @code{C} in its very last statement. In
11693 unoptimized compilation the call of @code{C} is immediately followed by return
11694 instruction at the end of @code{B} code. Optimizing compiler may replace the
11695 call and return in function @code{B} into one jump to function @code{C}
11696 instead. Such use of a jump instruction is called @dfn{tail call}.
11698 During execution of function @code{C}, there will be no indication in the
11699 function call stack frames that it was tail-called from @code{B}. If function
11700 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11701 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11702 some cases @value{GDBN} can determine that @code{C} was tail-called from
11703 @code{B}, and it will then create fictitious call frame for that, with the
11704 return address set up as if @code{B} called @code{C} normally.
11706 This functionality is currently supported only by DWARF 2 debugging format and
11707 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11708 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11711 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11712 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11716 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11718 Stack level 1, frame at 0x7fffffffda30:
11719 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11720 tail call frame, caller of frame at 0x7fffffffda30
11721 source language c++.
11722 Arglist at unknown address.
11723 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11726 The detection of all the possible code path executions can find them ambiguous.
11727 There is no execution history stored (possible @ref{Reverse Execution} is never
11728 used for this purpose) and the last known caller could have reached the known
11729 callee by multiple different jump sequences. In such case @value{GDBN} still
11730 tries to show at least all the unambiguous top tail callers and all the
11731 unambiguous bottom tail calees, if any.
11734 @anchor{set debug entry-values}
11735 @item set debug entry-values
11736 @kindex set debug entry-values
11737 When set to on, enables printing of analysis messages for both frame argument
11738 values at function entry and tail calls. It will show all the possible valid
11739 tail calls code paths it has considered. It will also print the intersection
11740 of them with the final unambiguous (possibly partial or even empty) code path
11743 @item show debug entry-values
11744 @kindex show debug entry-values
11745 Show the current state of analysis messages printing for both frame argument
11746 values at function entry and tail calls.
11749 The analysis messages for tail calls can for example show why the virtual tail
11750 call frame for function @code{c} has not been recognized (due to the indirect
11751 reference by variable @code{x}):
11754 static void __attribute__((noinline, noclone)) c (void);
11755 void (*x) (void) = c;
11756 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11757 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11758 int main (void) @{ x (); return 0; @}
11760 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11761 DW_TAG_GNU_call_site 0x40039a in main
11763 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11766 #1 0x000000000040039a in main () at t.c:5
11769 Another possibility is an ambiguous virtual tail call frames resolution:
11773 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11774 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11775 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11776 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11777 static void __attribute__((noinline, noclone)) b (void)
11778 @{ if (i) c (); else e (); @}
11779 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11780 int main (void) @{ a (); return 0; @}
11782 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11783 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11784 tailcall: reduced: 0x4004d2(a) |
11787 #1 0x00000000004004d2 in a () at t.c:8
11788 #2 0x0000000000400395 in main () at t.c:9
11791 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11792 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11794 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11795 @ifset HAVE_MAKEINFO_CLICK
11796 @set ARROW @click{}
11797 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11798 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11800 @ifclear HAVE_MAKEINFO_CLICK
11802 @set CALLSEQ1B @value{CALLSEQ1A}
11803 @set CALLSEQ2B @value{CALLSEQ2A}
11806 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11807 The code can have possible execution paths @value{CALLSEQ1B} or
11808 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11810 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11811 has found. It then finds another possible calling sequcen - that one is
11812 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11813 printed as the @code{reduced:} calling sequence. That one could have many
11814 futher @code{compare:} and @code{reduced:} statements as long as there remain
11815 any non-ambiguous sequence entries.
11817 For the frame of function @code{b} in both cases there are different possible
11818 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11819 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11820 therefore this one is displayed to the user while the ambiguous frames are
11823 There can be also reasons why printing of frame argument values at function
11828 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11829 static void __attribute__((noinline, noclone)) a (int i);
11830 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11831 static void __attribute__((noinline, noclone)) a (int i)
11832 @{ if (i) b (i - 1); else c (0); @}
11833 int main (void) @{ a (5); return 0; @}
11836 #0 c (i=i@@entry=0) at t.c:2
11837 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11838 function "a" at 0x400420 can call itself via tail calls
11839 i=<optimized out>) at t.c:6
11840 #2 0x000000000040036e in main () at t.c:7
11843 @value{GDBN} cannot find out from the inferior state if and how many times did
11844 function @code{a} call itself (via function @code{b}) as these calls would be
11845 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11846 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11847 prints @code{<optimized out>} instead.
11850 @chapter C Preprocessor Macros
11852 Some languages, such as C and C@t{++}, provide a way to define and invoke
11853 ``preprocessor macros'' which expand into strings of tokens.
11854 @value{GDBN} can evaluate expressions containing macro invocations, show
11855 the result of macro expansion, and show a macro's definition, including
11856 where it was defined.
11858 You may need to compile your program specially to provide @value{GDBN}
11859 with information about preprocessor macros. Most compilers do not
11860 include macros in their debugging information, even when you compile
11861 with the @option{-g} flag. @xref{Compilation}.
11863 A program may define a macro at one point, remove that definition later,
11864 and then provide a different definition after that. Thus, at different
11865 points in the program, a macro may have different definitions, or have
11866 no definition at all. If there is a current stack frame, @value{GDBN}
11867 uses the macros in scope at that frame's source code line. Otherwise,
11868 @value{GDBN} uses the macros in scope at the current listing location;
11871 Whenever @value{GDBN} evaluates an expression, it always expands any
11872 macro invocations present in the expression. @value{GDBN} also provides
11873 the following commands for working with macros explicitly.
11877 @kindex macro expand
11878 @cindex macro expansion, showing the results of preprocessor
11879 @cindex preprocessor macro expansion, showing the results of
11880 @cindex expanding preprocessor macros
11881 @item macro expand @var{expression}
11882 @itemx macro exp @var{expression}
11883 Show the results of expanding all preprocessor macro invocations in
11884 @var{expression}. Since @value{GDBN} simply expands macros, but does
11885 not parse the result, @var{expression} need not be a valid expression;
11886 it can be any string of tokens.
11889 @item macro expand-once @var{expression}
11890 @itemx macro exp1 @var{expression}
11891 @cindex expand macro once
11892 @i{(This command is not yet implemented.)} Show the results of
11893 expanding those preprocessor macro invocations that appear explicitly in
11894 @var{expression}. Macro invocations appearing in that expansion are
11895 left unchanged. This command allows you to see the effect of a
11896 particular macro more clearly, without being confused by further
11897 expansions. Since @value{GDBN} simply expands macros, but does not
11898 parse the result, @var{expression} need not be a valid expression; it
11899 can be any string of tokens.
11902 @cindex macro definition, showing
11903 @cindex definition of a macro, showing
11904 @cindex macros, from debug info
11905 @item info macro [-a|-all] [--] @var{macro}
11906 Show the current definition or all definitions of the named @var{macro},
11907 and describe the source location or compiler command-line where that
11908 definition was established. The optional double dash is to signify the end of
11909 argument processing and the beginning of @var{macro} for non C-like macros where
11910 the macro may begin with a hyphen.
11912 @kindex info macros
11913 @item info macros @var{location}
11914 Show all macro definitions that are in effect at the location specified
11915 by @var{location}, and describe the source location or compiler
11916 command-line where those definitions were established.
11918 @kindex macro define
11919 @cindex user-defined macros
11920 @cindex defining macros interactively
11921 @cindex macros, user-defined
11922 @item macro define @var{macro} @var{replacement-list}
11923 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11924 Introduce a definition for a preprocessor macro named @var{macro},
11925 invocations of which are replaced by the tokens given in
11926 @var{replacement-list}. The first form of this command defines an
11927 ``object-like'' macro, which takes no arguments; the second form
11928 defines a ``function-like'' macro, which takes the arguments given in
11931 A definition introduced by this command is in scope in every
11932 expression evaluated in @value{GDBN}, until it is removed with the
11933 @code{macro undef} command, described below. The definition overrides
11934 all definitions for @var{macro} present in the program being debugged,
11935 as well as any previous user-supplied definition.
11937 @kindex macro undef
11938 @item macro undef @var{macro}
11939 Remove any user-supplied definition for the macro named @var{macro}.
11940 This command only affects definitions provided with the @code{macro
11941 define} command, described above; it cannot remove definitions present
11942 in the program being debugged.
11946 List all the macros defined using the @code{macro define} command.
11949 @cindex macros, example of debugging with
11950 Here is a transcript showing the above commands in action. First, we
11951 show our source files:
11956 #include "sample.h"
11959 #define ADD(x) (M + x)
11964 printf ("Hello, world!\n");
11966 printf ("We're so creative.\n");
11968 printf ("Goodbye, world!\n");
11975 Now, we compile the program using the @sc{gnu} C compiler,
11976 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11977 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11978 and @option{-gdwarf-4}; we recommend always choosing the most recent
11979 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11980 includes information about preprocessor macros in the debugging
11984 $ gcc -gdwarf-2 -g3 sample.c -o sample
11988 Now, we start @value{GDBN} on our sample program:
11992 GNU gdb 2002-05-06-cvs
11993 Copyright 2002 Free Software Foundation, Inc.
11994 GDB is free software, @dots{}
11998 We can expand macros and examine their definitions, even when the
11999 program is not running. @value{GDBN} uses the current listing position
12000 to decide which macro definitions are in scope:
12003 (@value{GDBP}) list main
12006 5 #define ADD(x) (M + x)
12011 10 printf ("Hello, world!\n");
12013 12 printf ("We're so creative.\n");
12014 (@value{GDBP}) info macro ADD
12015 Defined at /home/jimb/gdb/macros/play/sample.c:5
12016 #define ADD(x) (M + x)
12017 (@value{GDBP}) info macro Q
12018 Defined at /home/jimb/gdb/macros/play/sample.h:1
12019 included at /home/jimb/gdb/macros/play/sample.c:2
12021 (@value{GDBP}) macro expand ADD(1)
12022 expands to: (42 + 1)
12023 (@value{GDBP}) macro expand-once ADD(1)
12024 expands to: once (M + 1)
12028 In the example above, note that @code{macro expand-once} expands only
12029 the macro invocation explicit in the original text --- the invocation of
12030 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12031 which was introduced by @code{ADD}.
12033 Once the program is running, @value{GDBN} uses the macro definitions in
12034 force at the source line of the current stack frame:
12037 (@value{GDBP}) break main
12038 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12040 Starting program: /home/jimb/gdb/macros/play/sample
12042 Breakpoint 1, main () at sample.c:10
12043 10 printf ("Hello, world!\n");
12047 At line 10, the definition of the macro @code{N} at line 9 is in force:
12050 (@value{GDBP}) info macro N
12051 Defined at /home/jimb/gdb/macros/play/sample.c:9
12053 (@value{GDBP}) macro expand N Q M
12054 expands to: 28 < 42
12055 (@value{GDBP}) print N Q M
12060 As we step over directives that remove @code{N}'s definition, and then
12061 give it a new definition, @value{GDBN} finds the definition (or lack
12062 thereof) in force at each point:
12065 (@value{GDBP}) next
12067 12 printf ("We're so creative.\n");
12068 (@value{GDBP}) info macro N
12069 The symbol `N' has no definition as a C/C++ preprocessor macro
12070 at /home/jimb/gdb/macros/play/sample.c:12
12071 (@value{GDBP}) next
12073 14 printf ("Goodbye, world!\n");
12074 (@value{GDBP}) info macro N
12075 Defined at /home/jimb/gdb/macros/play/sample.c:13
12077 (@value{GDBP}) macro expand N Q M
12078 expands to: 1729 < 42
12079 (@value{GDBP}) print N Q M
12084 In addition to source files, macros can be defined on the compilation command
12085 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12086 such a way, @value{GDBN} displays the location of their definition as line zero
12087 of the source file submitted to the compiler.
12090 (@value{GDBP}) info macro __STDC__
12091 Defined at /home/jimb/gdb/macros/play/sample.c:0
12098 @chapter Tracepoints
12099 @c This chapter is based on the documentation written by Michael
12100 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12102 @cindex tracepoints
12103 In some applications, it is not feasible for the debugger to interrupt
12104 the program's execution long enough for the developer to learn
12105 anything helpful about its behavior. If the program's correctness
12106 depends on its real-time behavior, delays introduced by a debugger
12107 might cause the program to change its behavior drastically, or perhaps
12108 fail, even when the code itself is correct. It is useful to be able
12109 to observe the program's behavior without interrupting it.
12111 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12112 specify locations in the program, called @dfn{tracepoints}, and
12113 arbitrary expressions to evaluate when those tracepoints are reached.
12114 Later, using the @code{tfind} command, you can examine the values
12115 those expressions had when the program hit the tracepoints. The
12116 expressions may also denote objects in memory---structures or arrays,
12117 for example---whose values @value{GDBN} should record; while visiting
12118 a particular tracepoint, you may inspect those objects as if they were
12119 in memory at that moment. However, because @value{GDBN} records these
12120 values without interacting with you, it can do so quickly and
12121 unobtrusively, hopefully not disturbing the program's behavior.
12123 The tracepoint facility is currently available only for remote
12124 targets. @xref{Targets}. In addition, your remote target must know
12125 how to collect trace data. This functionality is implemented in the
12126 remote stub; however, none of the stubs distributed with @value{GDBN}
12127 support tracepoints as of this writing. The format of the remote
12128 packets used to implement tracepoints are described in @ref{Tracepoint
12131 It is also possible to get trace data from a file, in a manner reminiscent
12132 of corefiles; you specify the filename, and use @code{tfind} to search
12133 through the file. @xref{Trace Files}, for more details.
12135 This chapter describes the tracepoint commands and features.
12138 * Set Tracepoints::
12139 * Analyze Collected Data::
12140 * Tracepoint Variables::
12144 @node Set Tracepoints
12145 @section Commands to Set Tracepoints
12147 Before running such a @dfn{trace experiment}, an arbitrary number of
12148 tracepoints can be set. A tracepoint is actually a special type of
12149 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12150 standard breakpoint commands. For instance, as with breakpoints,
12151 tracepoint numbers are successive integers starting from one, and many
12152 of the commands associated with tracepoints take the tracepoint number
12153 as their argument, to identify which tracepoint to work on.
12155 For each tracepoint, you can specify, in advance, some arbitrary set
12156 of data that you want the target to collect in the trace buffer when
12157 it hits that tracepoint. The collected data can include registers,
12158 local variables, or global data. Later, you can use @value{GDBN}
12159 commands to examine the values these data had at the time the
12160 tracepoint was hit.
12162 Tracepoints do not support every breakpoint feature. Ignore counts on
12163 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12164 commands when they are hit. Tracepoints may not be thread-specific
12167 @cindex fast tracepoints
12168 Some targets may support @dfn{fast tracepoints}, which are inserted in
12169 a different way (such as with a jump instead of a trap), that is
12170 faster but possibly restricted in where they may be installed.
12172 @cindex static tracepoints
12173 @cindex markers, static tracepoints
12174 @cindex probing markers, static tracepoints
12175 Regular and fast tracepoints are dynamic tracing facilities, meaning
12176 that they can be used to insert tracepoints at (almost) any location
12177 in the target. Some targets may also support controlling @dfn{static
12178 tracepoints} from @value{GDBN}. With static tracing, a set of
12179 instrumentation points, also known as @dfn{markers}, are embedded in
12180 the target program, and can be activated or deactivated by name or
12181 address. These are usually placed at locations which facilitate
12182 investigating what the target is actually doing. @value{GDBN}'s
12183 support for static tracing includes being able to list instrumentation
12184 points, and attach them with @value{GDBN} defined high level
12185 tracepoints that expose the whole range of convenience of
12186 @value{GDBN}'s tracepoints support. Namely, support for collecting
12187 registers values and values of global or local (to the instrumentation
12188 point) variables; tracepoint conditions and trace state variables.
12189 The act of installing a @value{GDBN} static tracepoint on an
12190 instrumentation point, or marker, is referred to as @dfn{probing} a
12191 static tracepoint marker.
12193 @code{gdbserver} supports tracepoints on some target systems.
12194 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12196 This section describes commands to set tracepoints and associated
12197 conditions and actions.
12200 * Create and Delete Tracepoints::
12201 * Enable and Disable Tracepoints::
12202 * Tracepoint Passcounts::
12203 * Tracepoint Conditions::
12204 * Trace State Variables::
12205 * Tracepoint Actions::
12206 * Listing Tracepoints::
12207 * Listing Static Tracepoint Markers::
12208 * Starting and Stopping Trace Experiments::
12209 * Tracepoint Restrictions::
12212 @node Create and Delete Tracepoints
12213 @subsection Create and Delete Tracepoints
12216 @cindex set tracepoint
12218 @item trace @var{location}
12219 The @code{trace} command is very similar to the @code{break} command.
12220 Its argument @var{location} can be any valid location.
12221 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12222 which is a point in the target program where the debugger will briefly stop,
12223 collect some data, and then allow the program to continue. Setting a tracepoint
12224 or changing its actions takes effect immediately if the remote stub
12225 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12227 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12228 these changes don't take effect until the next @code{tstart}
12229 command, and once a trace experiment is running, further changes will
12230 not have any effect until the next trace experiment starts. In addition,
12231 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12232 address is not yet resolved. (This is similar to pending breakpoints.)
12233 Pending tracepoints are not downloaded to the target and not installed
12234 until they are resolved. The resolution of pending tracepoints requires
12235 @value{GDBN} support---when debugging with the remote target, and
12236 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12237 tracing}), pending tracepoints can not be resolved (and downloaded to
12238 the remote stub) while @value{GDBN} is disconnected.
12240 Here are some examples of using the @code{trace} command:
12243 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12245 (@value{GDBP}) @b{trace +2} // 2 lines forward
12247 (@value{GDBP}) @b{trace my_function} // first source line of function
12249 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12251 (@value{GDBP}) @b{trace *0x2117c4} // an address
12255 You can abbreviate @code{trace} as @code{tr}.
12257 @item trace @var{location} if @var{cond}
12258 Set a tracepoint with condition @var{cond}; evaluate the expression
12259 @var{cond} each time the tracepoint is reached, and collect data only
12260 if the value is nonzero---that is, if @var{cond} evaluates as true.
12261 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12262 information on tracepoint conditions.
12264 @item ftrace @var{location} [ if @var{cond} ]
12265 @cindex set fast tracepoint
12266 @cindex fast tracepoints, setting
12268 The @code{ftrace} command sets a fast tracepoint. For targets that
12269 support them, fast tracepoints will use a more efficient but possibly
12270 less general technique to trigger data collection, such as a jump
12271 instruction instead of a trap, or some sort of hardware support. It
12272 may not be possible to create a fast tracepoint at the desired
12273 location, in which case the command will exit with an explanatory
12276 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12279 On 32-bit x86-architecture systems, fast tracepoints normally need to
12280 be placed at an instruction that is 5 bytes or longer, but can be
12281 placed at 4-byte instructions if the low 64K of memory of the target
12282 program is available to install trampolines. Some Unix-type systems,
12283 such as @sc{gnu}/Linux, exclude low addresses from the program's
12284 address space; but for instance with the Linux kernel it is possible
12285 to let @value{GDBN} use this area by doing a @command{sysctl} command
12286 to set the @code{mmap_min_addr} kernel parameter, as in
12289 sudo sysctl -w vm.mmap_min_addr=32768
12293 which sets the low address to 32K, which leaves plenty of room for
12294 trampolines. The minimum address should be set to a page boundary.
12296 @item strace @var{location} [ if @var{cond} ]
12297 @cindex set static tracepoint
12298 @cindex static tracepoints, setting
12299 @cindex probe static tracepoint marker
12301 The @code{strace} command sets a static tracepoint. For targets that
12302 support it, setting a static tracepoint probes a static
12303 instrumentation point, or marker, found at @var{location}. It may not
12304 be possible to set a static tracepoint at the desired location, in
12305 which case the command will exit with an explanatory message.
12307 @value{GDBN} handles arguments to @code{strace} exactly as for
12308 @code{trace}, with the addition that the user can also specify
12309 @code{-m @var{marker}} as @var{location}. This probes the marker
12310 identified by the @var{marker} string identifier. This identifier
12311 depends on the static tracepoint backend library your program is
12312 using. You can find all the marker identifiers in the @samp{ID} field
12313 of the @code{info static-tracepoint-markers} command output.
12314 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12315 Markers}. For example, in the following small program using the UST
12321 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12326 the marker id is composed of joining the first two arguments to the
12327 @code{trace_mark} call with a slash, which translates to:
12330 (@value{GDBP}) info static-tracepoint-markers
12331 Cnt Enb ID Address What
12332 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12338 so you may probe the marker above with:
12341 (@value{GDBP}) strace -m ust/bar33
12344 Static tracepoints accept an extra collect action --- @code{collect
12345 $_sdata}. This collects arbitrary user data passed in the probe point
12346 call to the tracing library. In the UST example above, you'll see
12347 that the third argument to @code{trace_mark} is a printf-like format
12348 string. The user data is then the result of running that formating
12349 string against the following arguments. Note that @code{info
12350 static-tracepoint-markers} command output lists that format string in
12351 the @samp{Data:} field.
12353 You can inspect this data when analyzing the trace buffer, by printing
12354 the $_sdata variable like any other variable available to
12355 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12358 @cindex last tracepoint number
12359 @cindex recent tracepoint number
12360 @cindex tracepoint number
12361 The convenience variable @code{$tpnum} records the tracepoint number
12362 of the most recently set tracepoint.
12364 @kindex delete tracepoint
12365 @cindex tracepoint deletion
12366 @item delete tracepoint @r{[}@var{num}@r{]}
12367 Permanently delete one or more tracepoints. With no argument, the
12368 default is to delete all tracepoints. Note that the regular
12369 @code{delete} command can remove tracepoints also.
12374 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12376 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12380 You can abbreviate this command as @code{del tr}.
12383 @node Enable and Disable Tracepoints
12384 @subsection Enable and Disable Tracepoints
12386 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12389 @kindex disable tracepoint
12390 @item disable tracepoint @r{[}@var{num}@r{]}
12391 Disable tracepoint @var{num}, or all tracepoints if no argument
12392 @var{num} is given. A disabled tracepoint will have no effect during
12393 a trace experiment, but it is not forgotten. You can re-enable
12394 a disabled tracepoint using the @code{enable tracepoint} command.
12395 If the command is issued during a trace experiment and the debug target
12396 has support for disabling tracepoints during a trace experiment, then the
12397 change will be effective immediately. Otherwise, it will be applied to the
12398 next trace experiment.
12400 @kindex enable tracepoint
12401 @item enable tracepoint @r{[}@var{num}@r{]}
12402 Enable tracepoint @var{num}, or all tracepoints. If this command is
12403 issued during a trace experiment and the debug target supports enabling
12404 tracepoints during a trace experiment, then the enabled tracepoints will
12405 become effective immediately. Otherwise, they will become effective the
12406 next time a trace experiment is run.
12409 @node Tracepoint Passcounts
12410 @subsection Tracepoint Passcounts
12414 @cindex tracepoint pass count
12415 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12416 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12417 automatically stop a trace experiment. If a tracepoint's passcount is
12418 @var{n}, then the trace experiment will be automatically stopped on
12419 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12420 @var{num} is not specified, the @code{passcount} command sets the
12421 passcount of the most recently defined tracepoint. If no passcount is
12422 given, the trace experiment will run until stopped explicitly by the
12428 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12429 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12431 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12432 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12433 (@value{GDBP}) @b{trace foo}
12434 (@value{GDBP}) @b{pass 3}
12435 (@value{GDBP}) @b{trace bar}
12436 (@value{GDBP}) @b{pass 2}
12437 (@value{GDBP}) @b{trace baz}
12438 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12439 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12440 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12441 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12445 @node Tracepoint Conditions
12446 @subsection Tracepoint Conditions
12447 @cindex conditional tracepoints
12448 @cindex tracepoint conditions
12450 The simplest sort of tracepoint collects data every time your program
12451 reaches a specified place. You can also specify a @dfn{condition} for
12452 a tracepoint. A condition is just a Boolean expression in your
12453 programming language (@pxref{Expressions, ,Expressions}). A
12454 tracepoint with a condition evaluates the expression each time your
12455 program reaches it, and data collection happens only if the condition
12458 Tracepoint conditions can be specified when a tracepoint is set, by
12459 using @samp{if} in the arguments to the @code{trace} command.
12460 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12461 also be set or changed at any time with the @code{condition} command,
12462 just as with breakpoints.
12464 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12465 the conditional expression itself. Instead, @value{GDBN} encodes the
12466 expression into an agent expression (@pxref{Agent Expressions})
12467 suitable for execution on the target, independently of @value{GDBN}.
12468 Global variables become raw memory locations, locals become stack
12469 accesses, and so forth.
12471 For instance, suppose you have a function that is usually called
12472 frequently, but should not be called after an error has occurred. You
12473 could use the following tracepoint command to collect data about calls
12474 of that function that happen while the error code is propagating
12475 through the program; an unconditional tracepoint could end up
12476 collecting thousands of useless trace frames that you would have to
12480 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12483 @node Trace State Variables
12484 @subsection Trace State Variables
12485 @cindex trace state variables
12487 A @dfn{trace state variable} is a special type of variable that is
12488 created and managed by target-side code. The syntax is the same as
12489 that for GDB's convenience variables (a string prefixed with ``$''),
12490 but they are stored on the target. They must be created explicitly,
12491 using a @code{tvariable} command. They are always 64-bit signed
12494 Trace state variables are remembered by @value{GDBN}, and downloaded
12495 to the target along with tracepoint information when the trace
12496 experiment starts. There are no intrinsic limits on the number of
12497 trace state variables, beyond memory limitations of the target.
12499 @cindex convenience variables, and trace state variables
12500 Although trace state variables are managed by the target, you can use
12501 them in print commands and expressions as if they were convenience
12502 variables; @value{GDBN} will get the current value from the target
12503 while the trace experiment is running. Trace state variables share
12504 the same namespace as other ``$'' variables, which means that you
12505 cannot have trace state variables with names like @code{$23} or
12506 @code{$pc}, nor can you have a trace state variable and a convenience
12507 variable with the same name.
12511 @item tvariable $@var{name} [ = @var{expression} ]
12513 The @code{tvariable} command creates a new trace state variable named
12514 @code{$@var{name}}, and optionally gives it an initial value of
12515 @var{expression}. The @var{expression} is evaluated when this command is
12516 entered; the result will be converted to an integer if possible,
12517 otherwise @value{GDBN} will report an error. A subsequent
12518 @code{tvariable} command specifying the same name does not create a
12519 variable, but instead assigns the supplied initial value to the
12520 existing variable of that name, overwriting any previous initial
12521 value. The default initial value is 0.
12523 @item info tvariables
12524 @kindex info tvariables
12525 List all the trace state variables along with their initial values.
12526 Their current values may also be displayed, if the trace experiment is
12529 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12530 @kindex delete tvariable
12531 Delete the given trace state variables, or all of them if no arguments
12536 @node Tracepoint Actions
12537 @subsection Tracepoint Action Lists
12541 @cindex tracepoint actions
12542 @item actions @r{[}@var{num}@r{]}
12543 This command will prompt for a list of actions to be taken when the
12544 tracepoint is hit. If the tracepoint number @var{num} is not
12545 specified, this command sets the actions for the one that was most
12546 recently defined (so that you can define a tracepoint and then say
12547 @code{actions} without bothering about its number). You specify the
12548 actions themselves on the following lines, one action at a time, and
12549 terminate the actions list with a line containing just @code{end}. So
12550 far, the only defined actions are @code{collect}, @code{teval}, and
12551 @code{while-stepping}.
12553 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12554 Commands, ,Breakpoint Command Lists}), except that only the defined
12555 actions are allowed; any other @value{GDBN} command is rejected.
12557 @cindex remove actions from a tracepoint
12558 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12559 and follow it immediately with @samp{end}.
12562 (@value{GDBP}) @b{collect @var{data}} // collect some data
12564 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12566 (@value{GDBP}) @b{end} // signals the end of actions.
12569 In the following example, the action list begins with @code{collect}
12570 commands indicating the things to be collected when the tracepoint is
12571 hit. Then, in order to single-step and collect additional data
12572 following the tracepoint, a @code{while-stepping} command is used,
12573 followed by the list of things to be collected after each step in a
12574 sequence of single steps. The @code{while-stepping} command is
12575 terminated by its own separate @code{end} command. Lastly, the action
12576 list is terminated by an @code{end} command.
12579 (@value{GDBP}) @b{trace foo}
12580 (@value{GDBP}) @b{actions}
12581 Enter actions for tracepoint 1, one per line:
12584 > while-stepping 12
12585 > collect $pc, arr[i]
12590 @kindex collect @r{(tracepoints)}
12591 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12592 Collect values of the given expressions when the tracepoint is hit.
12593 This command accepts a comma-separated list of any valid expressions.
12594 In addition to global, static, or local variables, the following
12595 special arguments are supported:
12599 Collect all registers.
12602 Collect all function arguments.
12605 Collect all local variables.
12608 Collect the return address. This is helpful if you want to see more
12612 Collects the number of arguments from the static probe at which the
12613 tracepoint is located.
12614 @xref{Static Probe Points}.
12616 @item $_probe_arg@var{n}
12617 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12618 from the static probe at which the tracepoint is located.
12619 @xref{Static Probe Points}.
12622 @vindex $_sdata@r{, collect}
12623 Collect static tracepoint marker specific data. Only available for
12624 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12625 Lists}. On the UST static tracepoints library backend, an
12626 instrumentation point resembles a @code{printf} function call. The
12627 tracing library is able to collect user specified data formatted to a
12628 character string using the format provided by the programmer that
12629 instrumented the program. Other backends have similar mechanisms.
12630 Here's an example of a UST marker call:
12633 const char master_name[] = "$your_name";
12634 trace_mark(channel1, marker1, "hello %s", master_name)
12637 In this case, collecting @code{$_sdata} collects the string
12638 @samp{hello $yourname}. When analyzing the trace buffer, you can
12639 inspect @samp{$_sdata} like any other variable available to
12643 You can give several consecutive @code{collect} commands, each one
12644 with a single argument, or one @code{collect} command with several
12645 arguments separated by commas; the effect is the same.
12647 The optional @var{mods} changes the usual handling of the arguments.
12648 @code{s} requests that pointers to chars be handled as strings, in
12649 particular collecting the contents of the memory being pointed at, up
12650 to the first zero. The upper bound is by default the value of the
12651 @code{print elements} variable; if @code{s} is followed by a decimal
12652 number, that is the upper bound instead. So for instance
12653 @samp{collect/s25 mystr} collects as many as 25 characters at
12656 The command @code{info scope} (@pxref{Symbols, info scope}) is
12657 particularly useful for figuring out what data to collect.
12659 @kindex teval @r{(tracepoints)}
12660 @item teval @var{expr1}, @var{expr2}, @dots{}
12661 Evaluate the given expressions when the tracepoint is hit. This
12662 command accepts a comma-separated list of expressions. The results
12663 are discarded, so this is mainly useful for assigning values to trace
12664 state variables (@pxref{Trace State Variables}) without adding those
12665 values to the trace buffer, as would be the case if the @code{collect}
12668 @kindex while-stepping @r{(tracepoints)}
12669 @item while-stepping @var{n}
12670 Perform @var{n} single-step instruction traces after the tracepoint,
12671 collecting new data after each step. The @code{while-stepping}
12672 command is followed by the list of what to collect while stepping
12673 (followed by its own @code{end} command):
12676 > while-stepping 12
12677 > collect $regs, myglobal
12683 Note that @code{$pc} is not automatically collected by
12684 @code{while-stepping}; you need to explicitly collect that register if
12685 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12688 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12689 @kindex set default-collect
12690 @cindex default collection action
12691 This variable is a list of expressions to collect at each tracepoint
12692 hit. It is effectively an additional @code{collect} action prepended
12693 to every tracepoint action list. The expressions are parsed
12694 individually for each tracepoint, so for instance a variable named
12695 @code{xyz} may be interpreted as a global for one tracepoint, and a
12696 local for another, as appropriate to the tracepoint's location.
12698 @item show default-collect
12699 @kindex show default-collect
12700 Show the list of expressions that are collected by default at each
12705 @node Listing Tracepoints
12706 @subsection Listing Tracepoints
12709 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12710 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12711 @cindex information about tracepoints
12712 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12713 Display information about the tracepoint @var{num}. If you don't
12714 specify a tracepoint number, displays information about all the
12715 tracepoints defined so far. The format is similar to that used for
12716 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12717 command, simply restricting itself to tracepoints.
12719 A tracepoint's listing may include additional information specific to
12724 its passcount as given by the @code{passcount @var{n}} command
12727 the state about installed on target of each location
12731 (@value{GDBP}) @b{info trace}
12732 Num Type Disp Enb Address What
12733 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12735 collect globfoo, $regs
12740 2 tracepoint keep y <MULTIPLE>
12742 2.1 y 0x0804859c in func4 at change-loc.h:35
12743 installed on target
12744 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12745 installed on target
12746 2.3 y <PENDING> set_tracepoint
12747 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12748 not installed on target
12753 This command can be abbreviated @code{info tp}.
12756 @node Listing Static Tracepoint Markers
12757 @subsection Listing Static Tracepoint Markers
12760 @kindex info static-tracepoint-markers
12761 @cindex information about static tracepoint markers
12762 @item info static-tracepoint-markers
12763 Display information about all static tracepoint markers defined in the
12766 For each marker, the following columns are printed:
12770 An incrementing counter, output to help readability. This is not a
12773 The marker ID, as reported by the target.
12774 @item Enabled or Disabled
12775 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12776 that are not enabled.
12778 Where the marker is in your program, as a memory address.
12780 Where the marker is in the source for your program, as a file and line
12781 number. If the debug information included in the program does not
12782 allow @value{GDBN} to locate the source of the marker, this column
12783 will be left blank.
12787 In addition, the following information may be printed for each marker:
12791 User data passed to the tracing library by the marker call. In the
12792 UST backend, this is the format string passed as argument to the
12794 @item Static tracepoints probing the marker
12795 The list of static tracepoints attached to the marker.
12799 (@value{GDBP}) info static-tracepoint-markers
12800 Cnt ID Enb Address What
12801 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12802 Data: number1 %d number2 %d
12803 Probed by static tracepoints: #2
12804 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12810 @node Starting and Stopping Trace Experiments
12811 @subsection Starting and Stopping Trace Experiments
12814 @kindex tstart [ @var{notes} ]
12815 @cindex start a new trace experiment
12816 @cindex collected data discarded
12818 This command starts the trace experiment, and begins collecting data.
12819 It has the side effect of discarding all the data collected in the
12820 trace buffer during the previous trace experiment. If any arguments
12821 are supplied, they are taken as a note and stored with the trace
12822 experiment's state. The notes may be arbitrary text, and are
12823 especially useful with disconnected tracing in a multi-user context;
12824 the notes can explain what the trace is doing, supply user contact
12825 information, and so forth.
12827 @kindex tstop [ @var{notes} ]
12828 @cindex stop a running trace experiment
12830 This command stops the trace experiment. If any arguments are
12831 supplied, they are recorded with the experiment as a note. This is
12832 useful if you are stopping a trace started by someone else, for
12833 instance if the trace is interfering with the system's behavior and
12834 needs to be stopped quickly.
12836 @strong{Note}: a trace experiment and data collection may stop
12837 automatically if any tracepoint's passcount is reached
12838 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12841 @cindex status of trace data collection
12842 @cindex trace experiment, status of
12844 This command displays the status of the current trace data
12848 Here is an example of the commands we described so far:
12851 (@value{GDBP}) @b{trace gdb_c_test}
12852 (@value{GDBP}) @b{actions}
12853 Enter actions for tracepoint #1, one per line.
12854 > collect $regs,$locals,$args
12855 > while-stepping 11
12859 (@value{GDBP}) @b{tstart}
12860 [time passes @dots{}]
12861 (@value{GDBP}) @b{tstop}
12864 @anchor{disconnected tracing}
12865 @cindex disconnected tracing
12866 You can choose to continue running the trace experiment even if
12867 @value{GDBN} disconnects from the target, voluntarily or
12868 involuntarily. For commands such as @code{detach}, the debugger will
12869 ask what you want to do with the trace. But for unexpected
12870 terminations (@value{GDBN} crash, network outage), it would be
12871 unfortunate to lose hard-won trace data, so the variable
12872 @code{disconnected-tracing} lets you decide whether the trace should
12873 continue running without @value{GDBN}.
12876 @item set disconnected-tracing on
12877 @itemx set disconnected-tracing off
12878 @kindex set disconnected-tracing
12879 Choose whether a tracing run should continue to run if @value{GDBN}
12880 has disconnected from the target. Note that @code{detach} or
12881 @code{quit} will ask you directly what to do about a running trace no
12882 matter what this variable's setting, so the variable is mainly useful
12883 for handling unexpected situations, such as loss of the network.
12885 @item show disconnected-tracing
12886 @kindex show disconnected-tracing
12887 Show the current choice for disconnected tracing.
12891 When you reconnect to the target, the trace experiment may or may not
12892 still be running; it might have filled the trace buffer in the
12893 meantime, or stopped for one of the other reasons. If it is running,
12894 it will continue after reconnection.
12896 Upon reconnection, the target will upload information about the
12897 tracepoints in effect. @value{GDBN} will then compare that
12898 information to the set of tracepoints currently defined, and attempt
12899 to match them up, allowing for the possibility that the numbers may
12900 have changed due to creation and deletion in the meantime. If one of
12901 the target's tracepoints does not match any in @value{GDBN}, the
12902 debugger will create a new tracepoint, so that you have a number with
12903 which to specify that tracepoint. This matching-up process is
12904 necessarily heuristic, and it may result in useless tracepoints being
12905 created; you may simply delete them if they are of no use.
12907 @cindex circular trace buffer
12908 If your target agent supports a @dfn{circular trace buffer}, then you
12909 can run a trace experiment indefinitely without filling the trace
12910 buffer; when space runs out, the agent deletes already-collected trace
12911 frames, oldest first, until there is enough room to continue
12912 collecting. This is especially useful if your tracepoints are being
12913 hit too often, and your trace gets terminated prematurely because the
12914 buffer is full. To ask for a circular trace buffer, simply set
12915 @samp{circular-trace-buffer} to on. You can set this at any time,
12916 including during tracing; if the agent can do it, it will change
12917 buffer handling on the fly, otherwise it will not take effect until
12921 @item set circular-trace-buffer on
12922 @itemx set circular-trace-buffer off
12923 @kindex set circular-trace-buffer
12924 Choose whether a tracing run should use a linear or circular buffer
12925 for trace data. A linear buffer will not lose any trace data, but may
12926 fill up prematurely, while a circular buffer will discard old trace
12927 data, but it will have always room for the latest tracepoint hits.
12929 @item show circular-trace-buffer
12930 @kindex show circular-trace-buffer
12931 Show the current choice for the trace buffer. Note that this may not
12932 match the agent's current buffer handling, nor is it guaranteed to
12933 match the setting that might have been in effect during a past run,
12934 for instance if you are looking at frames from a trace file.
12939 @item set trace-buffer-size @var{n}
12940 @itemx set trace-buffer-size unlimited
12941 @kindex set trace-buffer-size
12942 Request that the target use a trace buffer of @var{n} bytes. Not all
12943 targets will honor the request; they may have a compiled-in size for
12944 the trace buffer, or some other limitation. Set to a value of
12945 @code{unlimited} or @code{-1} to let the target use whatever size it
12946 likes. This is also the default.
12948 @item show trace-buffer-size
12949 @kindex show trace-buffer-size
12950 Show the current requested size for the trace buffer. Note that this
12951 will only match the actual size if the target supports size-setting,
12952 and was able to handle the requested size. For instance, if the
12953 target can only change buffer size between runs, this variable will
12954 not reflect the change until the next run starts. Use @code{tstatus}
12955 to get a report of the actual buffer size.
12959 @item set trace-user @var{text}
12960 @kindex set trace-user
12962 @item show trace-user
12963 @kindex show trace-user
12965 @item set trace-notes @var{text}
12966 @kindex set trace-notes
12967 Set the trace run's notes.
12969 @item show trace-notes
12970 @kindex show trace-notes
12971 Show the trace run's notes.
12973 @item set trace-stop-notes @var{text}
12974 @kindex set trace-stop-notes
12975 Set the trace run's stop notes. The handling of the note is as for
12976 @code{tstop} arguments; the set command is convenient way to fix a
12977 stop note that is mistaken or incomplete.
12979 @item show trace-stop-notes
12980 @kindex show trace-stop-notes
12981 Show the trace run's stop notes.
12985 @node Tracepoint Restrictions
12986 @subsection Tracepoint Restrictions
12988 @cindex tracepoint restrictions
12989 There are a number of restrictions on the use of tracepoints. As
12990 described above, tracepoint data gathering occurs on the target
12991 without interaction from @value{GDBN}. Thus the full capabilities of
12992 the debugger are not available during data gathering, and then at data
12993 examination time, you will be limited by only having what was
12994 collected. The following items describe some common problems, but it
12995 is not exhaustive, and you may run into additional difficulties not
13001 Tracepoint expressions are intended to gather objects (lvalues). Thus
13002 the full flexibility of GDB's expression evaluator is not available.
13003 You cannot call functions, cast objects to aggregate types, access
13004 convenience variables or modify values (except by assignment to trace
13005 state variables). Some language features may implicitly call
13006 functions (for instance Objective-C fields with accessors), and therefore
13007 cannot be collected either.
13010 Collection of local variables, either individually or in bulk with
13011 @code{$locals} or @code{$args}, during @code{while-stepping} may
13012 behave erratically. The stepping action may enter a new scope (for
13013 instance by stepping into a function), or the location of the variable
13014 may change (for instance it is loaded into a register). The
13015 tracepoint data recorded uses the location information for the
13016 variables that is correct for the tracepoint location. When the
13017 tracepoint is created, it is not possible, in general, to determine
13018 where the steps of a @code{while-stepping} sequence will advance the
13019 program---particularly if a conditional branch is stepped.
13022 Collection of an incompletely-initialized or partially-destroyed object
13023 may result in something that @value{GDBN} cannot display, or displays
13024 in a misleading way.
13027 When @value{GDBN} displays a pointer to character it automatically
13028 dereferences the pointer to also display characters of the string
13029 being pointed to. However, collecting the pointer during tracing does
13030 not automatically collect the string. You need to explicitly
13031 dereference the pointer and provide size information if you want to
13032 collect not only the pointer, but the memory pointed to. For example,
13033 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13037 It is not possible to collect a complete stack backtrace at a
13038 tracepoint. Instead, you may collect the registers and a few hundred
13039 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13040 (adjust to use the name of the actual stack pointer register on your
13041 target architecture, and the amount of stack you wish to capture).
13042 Then the @code{backtrace} command will show a partial backtrace when
13043 using a trace frame. The number of stack frames that can be examined
13044 depends on the sizes of the frames in the collected stack. Note that
13045 if you ask for a block so large that it goes past the bottom of the
13046 stack, the target agent may report an error trying to read from an
13050 If you do not collect registers at a tracepoint, @value{GDBN} can
13051 infer that the value of @code{$pc} must be the same as the address of
13052 the tracepoint and use that when you are looking at a trace frame
13053 for that tracepoint. However, this cannot work if the tracepoint has
13054 multiple locations (for instance if it was set in a function that was
13055 inlined), or if it has a @code{while-stepping} loop. In those cases
13056 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13061 @node Analyze Collected Data
13062 @section Using the Collected Data
13064 After the tracepoint experiment ends, you use @value{GDBN} commands
13065 for examining the trace data. The basic idea is that each tracepoint
13066 collects a trace @dfn{snapshot} every time it is hit and another
13067 snapshot every time it single-steps. All these snapshots are
13068 consecutively numbered from zero and go into a buffer, and you can
13069 examine them later. The way you examine them is to @dfn{focus} on a
13070 specific trace snapshot. When the remote stub is focused on a trace
13071 snapshot, it will respond to all @value{GDBN} requests for memory and
13072 registers by reading from the buffer which belongs to that snapshot,
13073 rather than from @emph{real} memory or registers of the program being
13074 debugged. This means that @strong{all} @value{GDBN} commands
13075 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13076 behave as if we were currently debugging the program state as it was
13077 when the tracepoint occurred. Any requests for data that are not in
13078 the buffer will fail.
13081 * tfind:: How to select a trace snapshot
13082 * tdump:: How to display all data for a snapshot
13083 * save tracepoints:: How to save tracepoints for a future run
13087 @subsection @code{tfind @var{n}}
13090 @cindex select trace snapshot
13091 @cindex find trace snapshot
13092 The basic command for selecting a trace snapshot from the buffer is
13093 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13094 counting from zero. If no argument @var{n} is given, the next
13095 snapshot is selected.
13097 Here are the various forms of using the @code{tfind} command.
13101 Find the first snapshot in the buffer. This is a synonym for
13102 @code{tfind 0} (since 0 is the number of the first snapshot).
13105 Stop debugging trace snapshots, resume @emph{live} debugging.
13108 Same as @samp{tfind none}.
13111 No argument means find the next trace snapshot.
13114 Find the previous trace snapshot before the current one. This permits
13115 retracing earlier steps.
13117 @item tfind tracepoint @var{num}
13118 Find the next snapshot associated with tracepoint @var{num}. Search
13119 proceeds forward from the last examined trace snapshot. If no
13120 argument @var{num} is given, it means find the next snapshot collected
13121 for the same tracepoint as the current snapshot.
13123 @item tfind pc @var{addr}
13124 Find the next snapshot associated with the value @var{addr} of the
13125 program counter. Search proceeds forward from the last examined trace
13126 snapshot. If no argument @var{addr} is given, it means find the next
13127 snapshot with the same value of PC as the current snapshot.
13129 @item tfind outside @var{addr1}, @var{addr2}
13130 Find the next snapshot whose PC is outside the given range of
13131 addresses (exclusive).
13133 @item tfind range @var{addr1}, @var{addr2}
13134 Find the next snapshot whose PC is between @var{addr1} and
13135 @var{addr2} (inclusive).
13137 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13138 Find the next snapshot associated with the source line @var{n}. If
13139 the optional argument @var{file} is given, refer to line @var{n} in
13140 that source file. Search proceeds forward from the last examined
13141 trace snapshot. If no argument @var{n} is given, it means find the
13142 next line other than the one currently being examined; thus saying
13143 @code{tfind line} repeatedly can appear to have the same effect as
13144 stepping from line to line in a @emph{live} debugging session.
13147 The default arguments for the @code{tfind} commands are specifically
13148 designed to make it easy to scan through the trace buffer. For
13149 instance, @code{tfind} with no argument selects the next trace
13150 snapshot, and @code{tfind -} with no argument selects the previous
13151 trace snapshot. So, by giving one @code{tfind} command, and then
13152 simply hitting @key{RET} repeatedly you can examine all the trace
13153 snapshots in order. Or, by saying @code{tfind -} and then hitting
13154 @key{RET} repeatedly you can examine the snapshots in reverse order.
13155 The @code{tfind line} command with no argument selects the snapshot
13156 for the next source line executed. The @code{tfind pc} command with
13157 no argument selects the next snapshot with the same program counter
13158 (PC) as the current frame. The @code{tfind tracepoint} command with
13159 no argument selects the next trace snapshot collected by the same
13160 tracepoint as the current one.
13162 In addition to letting you scan through the trace buffer manually,
13163 these commands make it easy to construct @value{GDBN} scripts that
13164 scan through the trace buffer and print out whatever collected data
13165 you are interested in. Thus, if we want to examine the PC, FP, and SP
13166 registers from each trace frame in the buffer, we can say this:
13169 (@value{GDBP}) @b{tfind start}
13170 (@value{GDBP}) @b{while ($trace_frame != -1)}
13171 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13172 $trace_frame, $pc, $sp, $fp
13176 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13177 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13178 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13179 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13180 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13181 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13182 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13183 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13184 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13185 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13186 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13189 Or, if we want to examine the variable @code{X} at each source line in
13193 (@value{GDBP}) @b{tfind start}
13194 (@value{GDBP}) @b{while ($trace_frame != -1)}
13195 > printf "Frame %d, X == %d\n", $trace_frame, X
13205 @subsection @code{tdump}
13207 @cindex dump all data collected at tracepoint
13208 @cindex tracepoint data, display
13210 This command takes no arguments. It prints all the data collected at
13211 the current trace snapshot.
13214 (@value{GDBP}) @b{trace 444}
13215 (@value{GDBP}) @b{actions}
13216 Enter actions for tracepoint #2, one per line:
13217 > collect $regs, $locals, $args, gdb_long_test
13220 (@value{GDBP}) @b{tstart}
13222 (@value{GDBP}) @b{tfind line 444}
13223 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13225 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13227 (@value{GDBP}) @b{tdump}
13228 Data collected at tracepoint 2, trace frame 1:
13229 d0 0xc4aa0085 -995491707
13233 d4 0x71aea3d 119204413
13236 d7 0x380035 3670069
13237 a0 0x19e24a 1696330
13238 a1 0x3000668 50333288
13240 a3 0x322000 3284992
13241 a4 0x3000698 50333336
13242 a5 0x1ad3cc 1758156
13243 fp 0x30bf3c 0x30bf3c
13244 sp 0x30bf34 0x30bf34
13246 pc 0x20b2c8 0x20b2c8
13250 p = 0x20e5b4 "gdb-test"
13257 gdb_long_test = 17 '\021'
13262 @code{tdump} works by scanning the tracepoint's current collection
13263 actions and printing the value of each expression listed. So
13264 @code{tdump} can fail, if after a run, you change the tracepoint's
13265 actions to mention variables that were not collected during the run.
13267 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13268 uses the collected value of @code{$pc} to distinguish between trace
13269 frames that were collected at the tracepoint hit, and frames that were
13270 collected while stepping. This allows it to correctly choose whether
13271 to display the basic list of collections, or the collections from the
13272 body of the while-stepping loop. However, if @code{$pc} was not collected,
13273 then @code{tdump} will always attempt to dump using the basic collection
13274 list, and may fail if a while-stepping frame does not include all the
13275 same data that is collected at the tracepoint hit.
13276 @c This is getting pretty arcane, example would be good.
13278 @node save tracepoints
13279 @subsection @code{save tracepoints @var{filename}}
13280 @kindex save tracepoints
13281 @kindex save-tracepoints
13282 @cindex save tracepoints for future sessions
13284 This command saves all current tracepoint definitions together with
13285 their actions and passcounts, into a file @file{@var{filename}}
13286 suitable for use in a later debugging session. To read the saved
13287 tracepoint definitions, use the @code{source} command (@pxref{Command
13288 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13289 alias for @w{@code{save tracepoints}}
13291 @node Tracepoint Variables
13292 @section Convenience Variables for Tracepoints
13293 @cindex tracepoint variables
13294 @cindex convenience variables for tracepoints
13297 @vindex $trace_frame
13298 @item (int) $trace_frame
13299 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13300 snapshot is selected.
13302 @vindex $tracepoint
13303 @item (int) $tracepoint
13304 The tracepoint for the current trace snapshot.
13306 @vindex $trace_line
13307 @item (int) $trace_line
13308 The line number for the current trace snapshot.
13310 @vindex $trace_file
13311 @item (char []) $trace_file
13312 The source file for the current trace snapshot.
13314 @vindex $trace_func
13315 @item (char []) $trace_func
13316 The name of the function containing @code{$tracepoint}.
13319 Note: @code{$trace_file} is not suitable for use in @code{printf},
13320 use @code{output} instead.
13322 Here's a simple example of using these convenience variables for
13323 stepping through all the trace snapshots and printing some of their
13324 data. Note that these are not the same as trace state variables,
13325 which are managed by the target.
13328 (@value{GDBP}) @b{tfind start}
13330 (@value{GDBP}) @b{while $trace_frame != -1}
13331 > output $trace_file
13332 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13338 @section Using Trace Files
13339 @cindex trace files
13341 In some situations, the target running a trace experiment may no
13342 longer be available; perhaps it crashed, or the hardware was needed
13343 for a different activity. To handle these cases, you can arrange to
13344 dump the trace data into a file, and later use that file as a source
13345 of trace data, via the @code{target tfile} command.
13350 @item tsave [ -r ] @var{filename}
13351 @itemx tsave [-ctf] @var{dirname}
13352 Save the trace data to @var{filename}. By default, this command
13353 assumes that @var{filename} refers to the host filesystem, so if
13354 necessary @value{GDBN} will copy raw trace data up from the target and
13355 then save it. If the target supports it, you can also supply the
13356 optional argument @code{-r} (``remote'') to direct the target to save
13357 the data directly into @var{filename} in its own filesystem, which may be
13358 more efficient if the trace buffer is very large. (Note, however, that
13359 @code{target tfile} can only read from files accessible to the host.)
13360 By default, this command will save trace frame in tfile format.
13361 You can supply the optional argument @code{-ctf} to save date in CTF
13362 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13363 that can be shared by multiple debugging and tracing tools. Please go to
13364 @indicateurl{http://www.efficios.com/ctf} to get more information.
13366 @kindex target tfile
13370 @item target tfile @var{filename}
13371 @itemx target ctf @var{dirname}
13372 Use the file named @var{filename} or directory named @var{dirname} as
13373 a source of trace data. Commands that examine data work as they do with
13374 a live target, but it is not possible to run any new trace experiments.
13375 @code{tstatus} will report the state of the trace run at the moment
13376 the data was saved, as well as the current trace frame you are examining.
13377 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13381 (@value{GDBP}) target ctf ctf.ctf
13382 (@value{GDBP}) tfind
13383 Found trace frame 0, tracepoint 2
13384 39 ++a; /* set tracepoint 1 here */
13385 (@value{GDBP}) tdump
13386 Data collected at tracepoint 2, trace frame 0:
13390 c = @{"123", "456", "789", "123", "456", "789"@}
13391 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13399 @chapter Debugging Programs That Use Overlays
13402 If your program is too large to fit completely in your target system's
13403 memory, you can sometimes use @dfn{overlays} to work around this
13404 problem. @value{GDBN} provides some support for debugging programs that
13408 * How Overlays Work:: A general explanation of overlays.
13409 * Overlay Commands:: Managing overlays in @value{GDBN}.
13410 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13411 mapped by asking the inferior.
13412 * Overlay Sample Program:: A sample program using overlays.
13415 @node How Overlays Work
13416 @section How Overlays Work
13417 @cindex mapped overlays
13418 @cindex unmapped overlays
13419 @cindex load address, overlay's
13420 @cindex mapped address
13421 @cindex overlay area
13423 Suppose you have a computer whose instruction address space is only 64
13424 kilobytes long, but which has much more memory which can be accessed by
13425 other means: special instructions, segment registers, or memory
13426 management hardware, for example. Suppose further that you want to
13427 adapt a program which is larger than 64 kilobytes to run on this system.
13429 One solution is to identify modules of your program which are relatively
13430 independent, and need not call each other directly; call these modules
13431 @dfn{overlays}. Separate the overlays from the main program, and place
13432 their machine code in the larger memory. Place your main program in
13433 instruction memory, but leave at least enough space there to hold the
13434 largest overlay as well.
13436 Now, to call a function located in an overlay, you must first copy that
13437 overlay's machine code from the large memory into the space set aside
13438 for it in the instruction memory, and then jump to its entry point
13441 @c NB: In the below the mapped area's size is greater or equal to the
13442 @c size of all overlays. This is intentional to remind the developer
13443 @c that overlays don't necessarily need to be the same size.
13447 Data Instruction Larger
13448 Address Space Address Space Address Space
13449 +-----------+ +-----------+ +-----------+
13451 +-----------+ +-----------+ +-----------+<-- overlay 1
13452 | program | | main | .----| overlay 1 | load address
13453 | variables | | program | | +-----------+
13454 | and heap | | | | | |
13455 +-----------+ | | | +-----------+<-- overlay 2
13456 | | +-----------+ | | | load address
13457 +-----------+ | | | .-| overlay 2 |
13459 mapped --->+-----------+ | | +-----------+
13460 address | | | | | |
13461 | overlay | <-' | | |
13462 | area | <---' +-----------+<-- overlay 3
13463 | | <---. | | load address
13464 +-----------+ `--| overlay 3 |
13471 @anchor{A code overlay}A code overlay
13475 The diagram (@pxref{A code overlay}) shows a system with separate data
13476 and instruction address spaces. To map an overlay, the program copies
13477 its code from the larger address space to the instruction address space.
13478 Since the overlays shown here all use the same mapped address, only one
13479 may be mapped at a time. For a system with a single address space for
13480 data and instructions, the diagram would be similar, except that the
13481 program variables and heap would share an address space with the main
13482 program and the overlay area.
13484 An overlay loaded into instruction memory and ready for use is called a
13485 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13486 instruction memory. An overlay not present (or only partially present)
13487 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13488 is its address in the larger memory. The mapped address is also called
13489 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13490 called the @dfn{load memory address}, or @dfn{LMA}.
13492 Unfortunately, overlays are not a completely transparent way to adapt a
13493 program to limited instruction memory. They introduce a new set of
13494 global constraints you must keep in mind as you design your program:
13499 Before calling or returning to a function in an overlay, your program
13500 must make sure that overlay is actually mapped. Otherwise, the call or
13501 return will transfer control to the right address, but in the wrong
13502 overlay, and your program will probably crash.
13505 If the process of mapping an overlay is expensive on your system, you
13506 will need to choose your overlays carefully to minimize their effect on
13507 your program's performance.
13510 The executable file you load onto your system must contain each
13511 overlay's instructions, appearing at the overlay's load address, not its
13512 mapped address. However, each overlay's instructions must be relocated
13513 and its symbols defined as if the overlay were at its mapped address.
13514 You can use GNU linker scripts to specify different load and relocation
13515 addresses for pieces of your program; see @ref{Overlay Description,,,
13516 ld.info, Using ld: the GNU linker}.
13519 The procedure for loading executable files onto your system must be able
13520 to load their contents into the larger address space as well as the
13521 instruction and data spaces.
13525 The overlay system described above is rather simple, and could be
13526 improved in many ways:
13531 If your system has suitable bank switch registers or memory management
13532 hardware, you could use those facilities to make an overlay's load area
13533 contents simply appear at their mapped address in instruction space.
13534 This would probably be faster than copying the overlay to its mapped
13535 area in the usual way.
13538 If your overlays are small enough, you could set aside more than one
13539 overlay area, and have more than one overlay mapped at a time.
13542 You can use overlays to manage data, as well as instructions. In
13543 general, data overlays are even less transparent to your design than
13544 code overlays: whereas code overlays only require care when you call or
13545 return to functions, data overlays require care every time you access
13546 the data. Also, if you change the contents of a data overlay, you
13547 must copy its contents back out to its load address before you can copy a
13548 different data overlay into the same mapped area.
13553 @node Overlay Commands
13554 @section Overlay Commands
13556 To use @value{GDBN}'s overlay support, each overlay in your program must
13557 correspond to a separate section of the executable file. The section's
13558 virtual memory address and load memory address must be the overlay's
13559 mapped and load addresses. Identifying overlays with sections allows
13560 @value{GDBN} to determine the appropriate address of a function or
13561 variable, depending on whether the overlay is mapped or not.
13563 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13564 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13569 Disable @value{GDBN}'s overlay support. When overlay support is
13570 disabled, @value{GDBN} assumes that all functions and variables are
13571 always present at their mapped addresses. By default, @value{GDBN}'s
13572 overlay support is disabled.
13574 @item overlay manual
13575 @cindex manual overlay debugging
13576 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13577 relies on you to tell it which overlays are mapped, and which are not,
13578 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13579 commands described below.
13581 @item overlay map-overlay @var{overlay}
13582 @itemx overlay map @var{overlay}
13583 @cindex map an overlay
13584 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13585 be the name of the object file section containing the overlay. When an
13586 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13587 functions and variables at their mapped addresses. @value{GDBN} assumes
13588 that any other overlays whose mapped ranges overlap that of
13589 @var{overlay} are now unmapped.
13591 @item overlay unmap-overlay @var{overlay}
13592 @itemx overlay unmap @var{overlay}
13593 @cindex unmap an overlay
13594 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13595 must be the name of the object file section containing the overlay.
13596 When an overlay is unmapped, @value{GDBN} assumes it can find the
13597 overlay's functions and variables at their load addresses.
13600 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13601 consults a data structure the overlay manager maintains in the inferior
13602 to see which overlays are mapped. For details, see @ref{Automatic
13603 Overlay Debugging}.
13605 @item overlay load-target
13606 @itemx overlay load
13607 @cindex reloading the overlay table
13608 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13609 re-reads the table @value{GDBN} automatically each time the inferior
13610 stops, so this command should only be necessary if you have changed the
13611 overlay mapping yourself using @value{GDBN}. This command is only
13612 useful when using automatic overlay debugging.
13614 @item overlay list-overlays
13615 @itemx overlay list
13616 @cindex listing mapped overlays
13617 Display a list of the overlays currently mapped, along with their mapped
13618 addresses, load addresses, and sizes.
13622 Normally, when @value{GDBN} prints a code address, it includes the name
13623 of the function the address falls in:
13626 (@value{GDBP}) print main
13627 $3 = @{int ()@} 0x11a0 <main>
13630 When overlay debugging is enabled, @value{GDBN} recognizes code in
13631 unmapped overlays, and prints the names of unmapped functions with
13632 asterisks around them. For example, if @code{foo} is a function in an
13633 unmapped overlay, @value{GDBN} prints it this way:
13636 (@value{GDBP}) overlay list
13637 No sections are mapped.
13638 (@value{GDBP}) print foo
13639 $5 = @{int (int)@} 0x100000 <*foo*>
13642 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13646 (@value{GDBP}) overlay list
13647 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13648 mapped at 0x1016 - 0x104a
13649 (@value{GDBP}) print foo
13650 $6 = @{int (int)@} 0x1016 <foo>
13653 When overlay debugging is enabled, @value{GDBN} can find the correct
13654 address for functions and variables in an overlay, whether or not the
13655 overlay is mapped. This allows most @value{GDBN} commands, like
13656 @code{break} and @code{disassemble}, to work normally, even on unmapped
13657 code. However, @value{GDBN}'s breakpoint support has some limitations:
13661 @cindex breakpoints in overlays
13662 @cindex overlays, setting breakpoints in
13663 You can set breakpoints in functions in unmapped overlays, as long as
13664 @value{GDBN} can write to the overlay at its load address.
13666 @value{GDBN} can not set hardware or simulator-based breakpoints in
13667 unmapped overlays. However, if you set a breakpoint at the end of your
13668 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13669 you are using manual overlay management), @value{GDBN} will re-set its
13670 breakpoints properly.
13674 @node Automatic Overlay Debugging
13675 @section Automatic Overlay Debugging
13676 @cindex automatic overlay debugging
13678 @value{GDBN} can automatically track which overlays are mapped and which
13679 are not, given some simple co-operation from the overlay manager in the
13680 inferior. If you enable automatic overlay debugging with the
13681 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13682 looks in the inferior's memory for certain variables describing the
13683 current state of the overlays.
13685 Here are the variables your overlay manager must define to support
13686 @value{GDBN}'s automatic overlay debugging:
13690 @item @code{_ovly_table}:
13691 This variable must be an array of the following structures:
13696 /* The overlay's mapped address. */
13699 /* The size of the overlay, in bytes. */
13700 unsigned long size;
13702 /* The overlay's load address. */
13705 /* Non-zero if the overlay is currently mapped;
13707 unsigned long mapped;
13711 @item @code{_novlys}:
13712 This variable must be a four-byte signed integer, holding the total
13713 number of elements in @code{_ovly_table}.
13717 To decide whether a particular overlay is mapped or not, @value{GDBN}
13718 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13719 @code{lma} members equal the VMA and LMA of the overlay's section in the
13720 executable file. When @value{GDBN} finds a matching entry, it consults
13721 the entry's @code{mapped} member to determine whether the overlay is
13724 In addition, your overlay manager may define a function called
13725 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13726 will silently set a breakpoint there. If the overlay manager then
13727 calls this function whenever it has changed the overlay table, this
13728 will enable @value{GDBN} to accurately keep track of which overlays
13729 are in program memory, and update any breakpoints that may be set
13730 in overlays. This will allow breakpoints to work even if the
13731 overlays are kept in ROM or other non-writable memory while they
13732 are not being executed.
13734 @node Overlay Sample Program
13735 @section Overlay Sample Program
13736 @cindex overlay example program
13738 When linking a program which uses overlays, you must place the overlays
13739 at their load addresses, while relocating them to run at their mapped
13740 addresses. To do this, you must write a linker script (@pxref{Overlay
13741 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13742 since linker scripts are specific to a particular host system, target
13743 architecture, and target memory layout, this manual cannot provide
13744 portable sample code demonstrating @value{GDBN}'s overlay support.
13746 However, the @value{GDBN} source distribution does contain an overlaid
13747 program, with linker scripts for a few systems, as part of its test
13748 suite. The program consists of the following files from
13749 @file{gdb/testsuite/gdb.base}:
13753 The main program file.
13755 A simple overlay manager, used by @file{overlays.c}.
13760 Overlay modules, loaded and used by @file{overlays.c}.
13763 Linker scripts for linking the test program on the @code{d10v-elf}
13764 and @code{m32r-elf} targets.
13767 You can build the test program using the @code{d10v-elf} GCC
13768 cross-compiler like this:
13771 $ d10v-elf-gcc -g -c overlays.c
13772 $ d10v-elf-gcc -g -c ovlymgr.c
13773 $ d10v-elf-gcc -g -c foo.c
13774 $ d10v-elf-gcc -g -c bar.c
13775 $ d10v-elf-gcc -g -c baz.c
13776 $ d10v-elf-gcc -g -c grbx.c
13777 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13778 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13781 The build process is identical for any other architecture, except that
13782 you must substitute the appropriate compiler and linker script for the
13783 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13787 @chapter Using @value{GDBN} with Different Languages
13790 Although programming languages generally have common aspects, they are
13791 rarely expressed in the same manner. For instance, in ANSI C,
13792 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13793 Modula-2, it is accomplished by @code{p^}. Values can also be
13794 represented (and displayed) differently. Hex numbers in C appear as
13795 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13797 @cindex working language
13798 Language-specific information is built into @value{GDBN} for some languages,
13799 allowing you to express operations like the above in your program's
13800 native language, and allowing @value{GDBN} to output values in a manner
13801 consistent with the syntax of your program's native language. The
13802 language you use to build expressions is called the @dfn{working
13806 * Setting:: Switching between source languages
13807 * Show:: Displaying the language
13808 * Checks:: Type and range checks
13809 * Supported Languages:: Supported languages
13810 * Unsupported Languages:: Unsupported languages
13814 @section Switching Between Source Languages
13816 There are two ways to control the working language---either have @value{GDBN}
13817 set it automatically, or select it manually yourself. You can use the
13818 @code{set language} command for either purpose. On startup, @value{GDBN}
13819 defaults to setting the language automatically. The working language is
13820 used to determine how expressions you type are interpreted, how values
13823 In addition to the working language, every source file that
13824 @value{GDBN} knows about has its own working language. For some object
13825 file formats, the compiler might indicate which language a particular
13826 source file is in. However, most of the time @value{GDBN} infers the
13827 language from the name of the file. The language of a source file
13828 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13829 show each frame appropriately for its own language. There is no way to
13830 set the language of a source file from within @value{GDBN}, but you can
13831 set the language associated with a filename extension. @xref{Show, ,
13832 Displaying the Language}.
13834 This is most commonly a problem when you use a program, such
13835 as @code{cfront} or @code{f2c}, that generates C but is written in
13836 another language. In that case, make the
13837 program use @code{#line} directives in its C output; that way
13838 @value{GDBN} will know the correct language of the source code of the original
13839 program, and will display that source code, not the generated C code.
13842 * Filenames:: Filename extensions and languages.
13843 * Manually:: Setting the working language manually
13844 * Automatically:: Having @value{GDBN} infer the source language
13848 @subsection List of Filename Extensions and Languages
13850 If a source file name ends in one of the following extensions, then
13851 @value{GDBN} infers that its language is the one indicated.
13869 C@t{++} source file
13875 Objective-C source file
13879 Fortran source file
13882 Modula-2 source file
13886 Assembler source file. This actually behaves almost like C, but
13887 @value{GDBN} does not skip over function prologues when stepping.
13890 In addition, you may set the language associated with a filename
13891 extension. @xref{Show, , Displaying the Language}.
13894 @subsection Setting the Working Language
13896 If you allow @value{GDBN} to set the language automatically,
13897 expressions are interpreted the same way in your debugging session and
13900 @kindex set language
13901 If you wish, you may set the language manually. To do this, issue the
13902 command @samp{set language @var{lang}}, where @var{lang} is the name of
13903 a language, such as
13904 @code{c} or @code{modula-2}.
13905 For a list of the supported languages, type @samp{set language}.
13907 Setting the language manually prevents @value{GDBN} from updating the working
13908 language automatically. This can lead to confusion if you try
13909 to debug a program when the working language is not the same as the
13910 source language, when an expression is acceptable to both
13911 languages---but means different things. For instance, if the current
13912 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13920 might not have the effect you intended. In C, this means to add
13921 @code{b} and @code{c} and place the result in @code{a}. The result
13922 printed would be the value of @code{a}. In Modula-2, this means to compare
13923 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13925 @node Automatically
13926 @subsection Having @value{GDBN} Infer the Source Language
13928 To have @value{GDBN} set the working language automatically, use
13929 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13930 then infers the working language. That is, when your program stops in a
13931 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13932 working language to the language recorded for the function in that
13933 frame. If the language for a frame is unknown (that is, if the function
13934 or block corresponding to the frame was defined in a source file that
13935 does not have a recognized extension), the current working language is
13936 not changed, and @value{GDBN} issues a warning.
13938 This may not seem necessary for most programs, which are written
13939 entirely in one source language. However, program modules and libraries
13940 written in one source language can be used by a main program written in
13941 a different source language. Using @samp{set language auto} in this
13942 case frees you from having to set the working language manually.
13945 @section Displaying the Language
13947 The following commands help you find out which language is the
13948 working language, and also what language source files were written in.
13951 @item show language
13952 @anchor{show language}
13953 @kindex show language
13954 Display the current working language. This is the
13955 language you can use with commands such as @code{print} to
13956 build and compute expressions that may involve variables in your program.
13959 @kindex info frame@r{, show the source language}
13960 Display the source language for this frame. This language becomes the
13961 working language if you use an identifier from this frame.
13962 @xref{Frame Info, ,Information about a Frame}, to identify the other
13963 information listed here.
13966 @kindex info source@r{, show the source language}
13967 Display the source language of this source file.
13968 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13969 information listed here.
13972 In unusual circumstances, you may have source files with extensions
13973 not in the standard list. You can then set the extension associated
13974 with a language explicitly:
13977 @item set extension-language @var{ext} @var{language}
13978 @kindex set extension-language
13979 Tell @value{GDBN} that source files with extension @var{ext} are to be
13980 assumed as written in the source language @var{language}.
13982 @item info extensions
13983 @kindex info extensions
13984 List all the filename extensions and the associated languages.
13988 @section Type and Range Checking
13990 Some languages are designed to guard you against making seemingly common
13991 errors through a series of compile- and run-time checks. These include
13992 checking the type of arguments to functions and operators and making
13993 sure mathematical overflows are caught at run time. Checks such as
13994 these help to ensure a program's correctness once it has been compiled
13995 by eliminating type mismatches and providing active checks for range
13996 errors when your program is running.
13998 By default @value{GDBN} checks for these errors according to the
13999 rules of the current source language. Although @value{GDBN} does not check
14000 the statements in your program, it can check expressions entered directly
14001 into @value{GDBN} for evaluation via the @code{print} command, for example.
14004 * Type Checking:: An overview of type checking
14005 * Range Checking:: An overview of range checking
14008 @cindex type checking
14009 @cindex checks, type
14010 @node Type Checking
14011 @subsection An Overview of Type Checking
14013 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14014 arguments to operators and functions have to be of the correct type,
14015 otherwise an error occurs. These checks prevent type mismatch
14016 errors from ever causing any run-time problems. For example,
14019 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14021 (@value{GDBP}) print obj.my_method (0)
14024 (@value{GDBP}) print obj.my_method (0x1234)
14025 Cannot resolve method klass::my_method to any overloaded instance
14028 The second example fails because in C@t{++} the integer constant
14029 @samp{0x1234} is not type-compatible with the pointer parameter type.
14031 For the expressions you use in @value{GDBN} commands, you can tell
14032 @value{GDBN} to not enforce strict type checking or
14033 to treat any mismatches as errors and abandon the expression;
14034 When type checking is disabled, @value{GDBN} successfully evaluates
14035 expressions like the second example above.
14037 Even if type checking is off, there may be other reasons
14038 related to type that prevent @value{GDBN} from evaluating an expression.
14039 For instance, @value{GDBN} does not know how to add an @code{int} and
14040 a @code{struct foo}. These particular type errors have nothing to do
14041 with the language in use and usually arise from expressions which make
14042 little sense to evaluate anyway.
14044 @value{GDBN} provides some additional commands for controlling type checking:
14046 @kindex set check type
14047 @kindex show check type
14049 @item set check type on
14050 @itemx set check type off
14051 Set strict type checking on or off. If any type mismatches occur in
14052 evaluating an expression while type checking is on, @value{GDBN} prints a
14053 message and aborts evaluation of the expression.
14055 @item show check type
14056 Show the current setting of type checking and whether @value{GDBN}
14057 is enforcing strict type checking rules.
14060 @cindex range checking
14061 @cindex checks, range
14062 @node Range Checking
14063 @subsection An Overview of Range Checking
14065 In some languages (such as Modula-2), it is an error to exceed the
14066 bounds of a type; this is enforced with run-time checks. Such range
14067 checking is meant to ensure program correctness by making sure
14068 computations do not overflow, or indices on an array element access do
14069 not exceed the bounds of the array.
14071 For expressions you use in @value{GDBN} commands, you can tell
14072 @value{GDBN} to treat range errors in one of three ways: ignore them,
14073 always treat them as errors and abandon the expression, or issue
14074 warnings but evaluate the expression anyway.
14076 A range error can result from numerical overflow, from exceeding an
14077 array index bound, or when you type a constant that is not a member
14078 of any type. Some languages, however, do not treat overflows as an
14079 error. In many implementations of C, mathematical overflow causes the
14080 result to ``wrap around'' to lower values---for example, if @var{m} is
14081 the largest integer value, and @var{s} is the smallest, then
14084 @var{m} + 1 @result{} @var{s}
14087 This, too, is specific to individual languages, and in some cases
14088 specific to individual compilers or machines. @xref{Supported Languages, ,
14089 Supported Languages}, for further details on specific languages.
14091 @value{GDBN} provides some additional commands for controlling the range checker:
14093 @kindex set check range
14094 @kindex show check range
14096 @item set check range auto
14097 Set range checking on or off based on the current working language.
14098 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14101 @item set check range on
14102 @itemx set check range off
14103 Set range checking on or off, overriding the default setting for the
14104 current working language. A warning is issued if the setting does not
14105 match the language default. If a range error occurs and range checking is on,
14106 then a message is printed and evaluation of the expression is aborted.
14108 @item set check range warn
14109 Output messages when the @value{GDBN} range checker detects a range error,
14110 but attempt to evaluate the expression anyway. Evaluating the
14111 expression may still be impossible for other reasons, such as accessing
14112 memory that the process does not own (a typical example from many Unix
14116 Show the current setting of the range checker, and whether or not it is
14117 being set automatically by @value{GDBN}.
14120 @node Supported Languages
14121 @section Supported Languages
14123 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
14124 OpenCL C, Pascal, assembly, Modula-2, and Ada.
14125 @c This is false ...
14126 Some @value{GDBN} features may be used in expressions regardless of the
14127 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14128 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14129 ,Expressions}) can be used with the constructs of any supported
14132 The following sections detail to what degree each source language is
14133 supported by @value{GDBN}. These sections are not meant to be language
14134 tutorials or references, but serve only as a reference guide to what the
14135 @value{GDBN} expression parser accepts, and what input and output
14136 formats should look like for different languages. There are many good
14137 books written on each of these languages; please look to these for a
14138 language reference or tutorial.
14141 * C:: C and C@t{++}
14144 * Objective-C:: Objective-C
14145 * OpenCL C:: OpenCL C
14146 * Fortran:: Fortran
14148 * Modula-2:: Modula-2
14153 @subsection C and C@t{++}
14155 @cindex C and C@t{++}
14156 @cindex expressions in C or C@t{++}
14158 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14159 to both languages. Whenever this is the case, we discuss those languages
14163 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14164 @cindex @sc{gnu} C@t{++}
14165 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14166 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14167 effectively, you must compile your C@t{++} programs with a supported
14168 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14169 compiler (@code{aCC}).
14172 * C Operators:: C and C@t{++} operators
14173 * C Constants:: C and C@t{++} constants
14174 * C Plus Plus Expressions:: C@t{++} expressions
14175 * C Defaults:: Default settings for C and C@t{++}
14176 * C Checks:: C and C@t{++} type and range checks
14177 * Debugging C:: @value{GDBN} and C
14178 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14179 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14183 @subsubsection C and C@t{++} Operators
14185 @cindex C and C@t{++} operators
14187 Operators must be defined on values of specific types. For instance,
14188 @code{+} is defined on numbers, but not on structures. Operators are
14189 often defined on groups of types.
14191 For the purposes of C and C@t{++}, the following definitions hold:
14196 @emph{Integral types} include @code{int} with any of its storage-class
14197 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14200 @emph{Floating-point types} include @code{float}, @code{double}, and
14201 @code{long double} (if supported by the target platform).
14204 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14207 @emph{Scalar types} include all of the above.
14212 The following operators are supported. They are listed here
14213 in order of increasing precedence:
14217 The comma or sequencing operator. Expressions in a comma-separated list
14218 are evaluated from left to right, with the result of the entire
14219 expression being the last expression evaluated.
14222 Assignment. The value of an assignment expression is the value
14223 assigned. Defined on scalar types.
14226 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14227 and translated to @w{@code{@var{a} = @var{a op b}}}.
14228 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14229 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14230 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14233 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14234 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14235 should be of an integral type.
14238 Logical @sc{or}. Defined on integral types.
14241 Logical @sc{and}. Defined on integral types.
14244 Bitwise @sc{or}. Defined on integral types.
14247 Bitwise exclusive-@sc{or}. Defined on integral types.
14250 Bitwise @sc{and}. Defined on integral types.
14253 Equality and inequality. Defined on scalar types. The value of these
14254 expressions is 0 for false and non-zero for true.
14256 @item <@r{, }>@r{, }<=@r{, }>=
14257 Less than, greater than, less than or equal, greater than or equal.
14258 Defined on scalar types. The value of these expressions is 0 for false
14259 and non-zero for true.
14262 left shift, and right shift. Defined on integral types.
14265 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14268 Addition and subtraction. Defined on integral types, floating-point types and
14271 @item *@r{, }/@r{, }%
14272 Multiplication, division, and modulus. Multiplication and division are
14273 defined on integral and floating-point types. Modulus is defined on
14277 Increment and decrement. When appearing before a variable, the
14278 operation is performed before the variable is used in an expression;
14279 when appearing after it, the variable's value is used before the
14280 operation takes place.
14283 Pointer dereferencing. Defined on pointer types. Same precedence as
14287 Address operator. Defined on variables. Same precedence as @code{++}.
14289 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14290 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14291 to examine the address
14292 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14296 Negative. Defined on integral and floating-point types. Same
14297 precedence as @code{++}.
14300 Logical negation. Defined on integral types. Same precedence as
14304 Bitwise complement operator. Defined on integral types. Same precedence as
14309 Structure member, and pointer-to-structure member. For convenience,
14310 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14311 pointer based on the stored type information.
14312 Defined on @code{struct} and @code{union} data.
14315 Dereferences of pointers to members.
14318 Array indexing. @code{@var{a}[@var{i}]} is defined as
14319 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14322 Function parameter list. Same precedence as @code{->}.
14325 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14326 and @code{class} types.
14329 Doubled colons also represent the @value{GDBN} scope operator
14330 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14334 If an operator is redefined in the user code, @value{GDBN} usually
14335 attempts to invoke the redefined version instead of using the operator's
14336 predefined meaning.
14339 @subsubsection C and C@t{++} Constants
14341 @cindex C and C@t{++} constants
14343 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14348 Integer constants are a sequence of digits. Octal constants are
14349 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14350 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14351 @samp{l}, specifying that the constant should be treated as a
14355 Floating point constants are a sequence of digits, followed by a decimal
14356 point, followed by a sequence of digits, and optionally followed by an
14357 exponent. An exponent is of the form:
14358 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14359 sequence of digits. The @samp{+} is optional for positive exponents.
14360 A floating-point constant may also end with a letter @samp{f} or
14361 @samp{F}, specifying that the constant should be treated as being of
14362 the @code{float} (as opposed to the default @code{double}) type; or with
14363 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14367 Enumerated constants consist of enumerated identifiers, or their
14368 integral equivalents.
14371 Character constants are a single character surrounded by single quotes
14372 (@code{'}), or a number---the ordinal value of the corresponding character
14373 (usually its @sc{ascii} value). Within quotes, the single character may
14374 be represented by a letter or by @dfn{escape sequences}, which are of
14375 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14376 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14377 @samp{@var{x}} is a predefined special character---for example,
14378 @samp{\n} for newline.
14380 Wide character constants can be written by prefixing a character
14381 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14382 form of @samp{x}. The target wide character set is used when
14383 computing the value of this constant (@pxref{Character Sets}).
14386 String constants are a sequence of character constants surrounded by
14387 double quotes (@code{"}). Any valid character constant (as described
14388 above) may appear. Double quotes within the string must be preceded by
14389 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14392 Wide string constants can be written by prefixing a string constant
14393 with @samp{L}, as in C. The target wide character set is used when
14394 computing the value of this constant (@pxref{Character Sets}).
14397 Pointer constants are an integral value. You can also write pointers
14398 to constants using the C operator @samp{&}.
14401 Array constants are comma-separated lists surrounded by braces @samp{@{}
14402 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14403 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14404 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14407 @node C Plus Plus Expressions
14408 @subsubsection C@t{++} Expressions
14410 @cindex expressions in C@t{++}
14411 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14413 @cindex debugging C@t{++} programs
14414 @cindex C@t{++} compilers
14415 @cindex debug formats and C@t{++}
14416 @cindex @value{NGCC} and C@t{++}
14418 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14419 the proper compiler and the proper debug format. Currently,
14420 @value{GDBN} works best when debugging C@t{++} code that is compiled
14421 with the most recent version of @value{NGCC} possible. The DWARF
14422 debugging format is preferred; @value{NGCC} defaults to this on most
14423 popular platforms. Other compilers and/or debug formats are likely to
14424 work badly or not at all when using @value{GDBN} to debug C@t{++}
14425 code. @xref{Compilation}.
14430 @cindex member functions
14432 Member function calls are allowed; you can use expressions like
14435 count = aml->GetOriginal(x, y)
14438 @vindex this@r{, inside C@t{++} member functions}
14439 @cindex namespace in C@t{++}
14441 While a member function is active (in the selected stack frame), your
14442 expressions have the same namespace available as the member function;
14443 that is, @value{GDBN} allows implicit references to the class instance
14444 pointer @code{this} following the same rules as C@t{++}. @code{using}
14445 declarations in the current scope are also respected by @value{GDBN}.
14447 @cindex call overloaded functions
14448 @cindex overloaded functions, calling
14449 @cindex type conversions in C@t{++}
14451 You can call overloaded functions; @value{GDBN} resolves the function
14452 call to the right definition, with some restrictions. @value{GDBN} does not
14453 perform overload resolution involving user-defined type conversions,
14454 calls to constructors, or instantiations of templates that do not exist
14455 in the program. It also cannot handle ellipsis argument lists or
14458 It does perform integral conversions and promotions, floating-point
14459 promotions, arithmetic conversions, pointer conversions, conversions of
14460 class objects to base classes, and standard conversions such as those of
14461 functions or arrays to pointers; it requires an exact match on the
14462 number of function arguments.
14464 Overload resolution is always performed, unless you have specified
14465 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14466 ,@value{GDBN} Features for C@t{++}}.
14468 You must specify @code{set overload-resolution off} in order to use an
14469 explicit function signature to call an overloaded function, as in
14471 p 'foo(char,int)'('x', 13)
14474 The @value{GDBN} command-completion facility can simplify this;
14475 see @ref{Completion, ,Command Completion}.
14477 @cindex reference declarations
14479 @value{GDBN} understands variables declared as C@t{++} references; you can use
14480 them in expressions just as you do in C@t{++} source---they are automatically
14483 In the parameter list shown when @value{GDBN} displays a frame, the values of
14484 reference variables are not displayed (unlike other variables); this
14485 avoids clutter, since references are often used for large structures.
14486 The @emph{address} of a reference variable is always shown, unless
14487 you have specified @samp{set print address off}.
14490 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14491 expressions can use it just as expressions in your program do. Since
14492 one scope may be defined in another, you can use @code{::} repeatedly if
14493 necessary, for example in an expression like
14494 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14495 resolving name scope by reference to source files, in both C and C@t{++}
14496 debugging (@pxref{Variables, ,Program Variables}).
14499 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14504 @subsubsection C and C@t{++} Defaults
14506 @cindex C and C@t{++} defaults
14508 If you allow @value{GDBN} to set range checking automatically, it
14509 defaults to @code{off} whenever the working language changes to
14510 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14511 selects the working language.
14513 If you allow @value{GDBN} to set the language automatically, it
14514 recognizes source files whose names end with @file{.c}, @file{.C}, or
14515 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14516 these files, it sets the working language to C or C@t{++}.
14517 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14518 for further details.
14521 @subsubsection C and C@t{++} Type and Range Checks
14523 @cindex C and C@t{++} checks
14525 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14526 checking is used. However, if you turn type checking off, @value{GDBN}
14527 will allow certain non-standard conversions, such as promoting integer
14528 constants to pointers.
14530 Range checking, if turned on, is done on mathematical operations. Array
14531 indices are not checked, since they are often used to index a pointer
14532 that is not itself an array.
14535 @subsubsection @value{GDBN} and C
14537 The @code{set print union} and @code{show print union} commands apply to
14538 the @code{union} type. When set to @samp{on}, any @code{union} that is
14539 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14540 appears as @samp{@{...@}}.
14542 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14543 with pointers and a memory allocation function. @xref{Expressions,
14546 @node Debugging C Plus Plus
14547 @subsubsection @value{GDBN} Features for C@t{++}
14549 @cindex commands for C@t{++}
14551 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14552 designed specifically for use with C@t{++}. Here is a summary:
14555 @cindex break in overloaded functions
14556 @item @r{breakpoint menus}
14557 When you want a breakpoint in a function whose name is overloaded,
14558 @value{GDBN} has the capability to display a menu of possible breakpoint
14559 locations to help you specify which function definition you want.
14560 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14562 @cindex overloading in C@t{++}
14563 @item rbreak @var{regex}
14564 Setting breakpoints using regular expressions is helpful for setting
14565 breakpoints on overloaded functions that are not members of any special
14567 @xref{Set Breaks, ,Setting Breakpoints}.
14569 @cindex C@t{++} exception handling
14571 @itemx catch rethrow
14573 Debug C@t{++} exception handling using these commands. @xref{Set
14574 Catchpoints, , Setting Catchpoints}.
14576 @cindex inheritance
14577 @item ptype @var{typename}
14578 Print inheritance relationships as well as other information for type
14580 @xref{Symbols, ,Examining the Symbol Table}.
14582 @item info vtbl @var{expression}.
14583 The @code{info vtbl} command can be used to display the virtual
14584 method tables of the object computed by @var{expression}. This shows
14585 one entry per virtual table; there may be multiple virtual tables when
14586 multiple inheritance is in use.
14588 @cindex C@t{++} demangling
14589 @item demangle @var{name}
14590 Demangle @var{name}.
14591 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14593 @cindex C@t{++} symbol display
14594 @item set print demangle
14595 @itemx show print demangle
14596 @itemx set print asm-demangle
14597 @itemx show print asm-demangle
14598 Control whether C@t{++} symbols display in their source form, both when
14599 displaying code as C@t{++} source and when displaying disassemblies.
14600 @xref{Print Settings, ,Print Settings}.
14602 @item set print object
14603 @itemx show print object
14604 Choose whether to print derived (actual) or declared types of objects.
14605 @xref{Print Settings, ,Print Settings}.
14607 @item set print vtbl
14608 @itemx show print vtbl
14609 Control the format for printing virtual function tables.
14610 @xref{Print Settings, ,Print Settings}.
14611 (The @code{vtbl} commands do not work on programs compiled with the HP
14612 ANSI C@t{++} compiler (@code{aCC}).)
14614 @kindex set overload-resolution
14615 @cindex overloaded functions, overload resolution
14616 @item set overload-resolution on
14617 Enable overload resolution for C@t{++} expression evaluation. The default
14618 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14619 and searches for a function whose signature matches the argument types,
14620 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14621 Expressions, ,C@t{++} Expressions}, for details).
14622 If it cannot find a match, it emits a message.
14624 @item set overload-resolution off
14625 Disable overload resolution for C@t{++} expression evaluation. For
14626 overloaded functions that are not class member functions, @value{GDBN}
14627 chooses the first function of the specified name that it finds in the
14628 symbol table, whether or not its arguments are of the correct type. For
14629 overloaded functions that are class member functions, @value{GDBN}
14630 searches for a function whose signature @emph{exactly} matches the
14633 @kindex show overload-resolution
14634 @item show overload-resolution
14635 Show the current setting of overload resolution.
14637 @item @r{Overloaded symbol names}
14638 You can specify a particular definition of an overloaded symbol, using
14639 the same notation that is used to declare such symbols in C@t{++}: type
14640 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14641 also use the @value{GDBN} command-line word completion facilities to list the
14642 available choices, or to finish the type list for you.
14643 @xref{Completion,, Command Completion}, for details on how to do this.
14646 @node Decimal Floating Point
14647 @subsubsection Decimal Floating Point format
14648 @cindex decimal floating point format
14650 @value{GDBN} can examine, set and perform computations with numbers in
14651 decimal floating point format, which in the C language correspond to the
14652 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14653 specified by the extension to support decimal floating-point arithmetic.
14655 There are two encodings in use, depending on the architecture: BID (Binary
14656 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14657 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14660 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14661 to manipulate decimal floating point numbers, it is not possible to convert
14662 (using a cast, for example) integers wider than 32-bit to decimal float.
14664 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14665 point computations, error checking in decimal float operations ignores
14666 underflow, overflow and divide by zero exceptions.
14668 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14669 to inspect @code{_Decimal128} values stored in floating point registers.
14670 See @ref{PowerPC,,PowerPC} for more details.
14676 @value{GDBN} can be used to debug programs written in D and compiled with
14677 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14678 specific feature --- dynamic arrays.
14683 @cindex Go (programming language)
14684 @value{GDBN} can be used to debug programs written in Go and compiled with
14685 @file{gccgo} or @file{6g} compilers.
14687 Here is a summary of the Go-specific features and restrictions:
14690 @cindex current Go package
14691 @item The current Go package
14692 The name of the current package does not need to be specified when
14693 specifying global variables and functions.
14695 For example, given the program:
14699 var myglob = "Shall we?"
14705 When stopped inside @code{main} either of these work:
14709 (gdb) p main.myglob
14712 @cindex builtin Go types
14713 @item Builtin Go types
14714 The @code{string} type is recognized by @value{GDBN} and is printed
14717 @cindex builtin Go functions
14718 @item Builtin Go functions
14719 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14720 function and handles it internally.
14722 @cindex restrictions on Go expressions
14723 @item Restrictions on Go expressions
14724 All Go operators are supported except @code{&^}.
14725 The Go @code{_} ``blank identifier'' is not supported.
14726 Automatic dereferencing of pointers is not supported.
14730 @subsection Objective-C
14732 @cindex Objective-C
14733 This section provides information about some commands and command
14734 options that are useful for debugging Objective-C code. See also
14735 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14736 few more commands specific to Objective-C support.
14739 * Method Names in Commands::
14740 * The Print Command with Objective-C::
14743 @node Method Names in Commands
14744 @subsubsection Method Names in Commands
14746 The following commands have been extended to accept Objective-C method
14747 names as line specifications:
14749 @kindex clear@r{, and Objective-C}
14750 @kindex break@r{, and Objective-C}
14751 @kindex info line@r{, and Objective-C}
14752 @kindex jump@r{, and Objective-C}
14753 @kindex list@r{, and Objective-C}
14757 @item @code{info line}
14762 A fully qualified Objective-C method name is specified as
14765 -[@var{Class} @var{methodName}]
14768 where the minus sign is used to indicate an instance method and a
14769 plus sign (not shown) is used to indicate a class method. The class
14770 name @var{Class} and method name @var{methodName} are enclosed in
14771 brackets, similar to the way messages are specified in Objective-C
14772 source code. For example, to set a breakpoint at the @code{create}
14773 instance method of class @code{Fruit} in the program currently being
14777 break -[Fruit create]
14780 To list ten program lines around the @code{initialize} class method,
14784 list +[NSText initialize]
14787 In the current version of @value{GDBN}, the plus or minus sign is
14788 required. In future versions of @value{GDBN}, the plus or minus
14789 sign will be optional, but you can use it to narrow the search. It
14790 is also possible to specify just a method name:
14796 You must specify the complete method name, including any colons. If
14797 your program's source files contain more than one @code{create} method,
14798 you'll be presented with a numbered list of classes that implement that
14799 method. Indicate your choice by number, or type @samp{0} to exit if
14802 As another example, to clear a breakpoint established at the
14803 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14806 clear -[NSWindow makeKeyAndOrderFront:]
14809 @node The Print Command with Objective-C
14810 @subsubsection The Print Command With Objective-C
14811 @cindex Objective-C, print objects
14812 @kindex print-object
14813 @kindex po @r{(@code{print-object})}
14815 The print command has also been extended to accept methods. For example:
14818 print -[@var{object} hash]
14821 @cindex print an Objective-C object description
14822 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14824 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14825 and print the result. Also, an additional command has been added,
14826 @code{print-object} or @code{po} for short, which is meant to print
14827 the description of an object. However, this command may only work
14828 with certain Objective-C libraries that have a particular hook
14829 function, @code{_NSPrintForDebugger}, defined.
14832 @subsection OpenCL C
14835 This section provides information about @value{GDBN}s OpenCL C support.
14838 * OpenCL C Datatypes::
14839 * OpenCL C Expressions::
14840 * OpenCL C Operators::
14843 @node OpenCL C Datatypes
14844 @subsubsection OpenCL C Datatypes
14846 @cindex OpenCL C Datatypes
14847 @value{GDBN} supports the builtin scalar and vector datatypes specified
14848 by OpenCL 1.1. In addition the half- and double-precision floating point
14849 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14850 extensions are also known to @value{GDBN}.
14852 @node OpenCL C Expressions
14853 @subsubsection OpenCL C Expressions
14855 @cindex OpenCL C Expressions
14856 @value{GDBN} supports accesses to vector components including the access as
14857 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14858 supported by @value{GDBN} can be used as well.
14860 @node OpenCL C Operators
14861 @subsubsection OpenCL C Operators
14863 @cindex OpenCL C Operators
14864 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14868 @subsection Fortran
14869 @cindex Fortran-specific support in @value{GDBN}
14871 @value{GDBN} can be used to debug programs written in Fortran, but it
14872 currently supports only the features of Fortran 77 language.
14874 @cindex trailing underscore, in Fortran symbols
14875 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14876 among them) append an underscore to the names of variables and
14877 functions. When you debug programs compiled by those compilers, you
14878 will need to refer to variables and functions with a trailing
14882 * Fortran Operators:: Fortran operators and expressions
14883 * Fortran Defaults:: Default settings for Fortran
14884 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14887 @node Fortran Operators
14888 @subsubsection Fortran Operators and Expressions
14890 @cindex Fortran operators and expressions
14892 Operators must be defined on values of specific types. For instance,
14893 @code{+} is defined on numbers, but not on characters or other non-
14894 arithmetic types. Operators are often defined on groups of types.
14898 The exponentiation operator. It raises the first operand to the power
14902 The range operator. Normally used in the form of array(low:high) to
14903 represent a section of array.
14906 The access component operator. Normally used to access elements in derived
14907 types. Also suitable for unions. As unions aren't part of regular Fortran,
14908 this can only happen when accessing a register that uses a gdbarch-defined
14912 @node Fortran Defaults
14913 @subsubsection Fortran Defaults
14915 @cindex Fortran Defaults
14917 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14918 default uses case-insensitive matches for Fortran symbols. You can
14919 change that with the @samp{set case-insensitive} command, see
14920 @ref{Symbols}, for the details.
14922 @node Special Fortran Commands
14923 @subsubsection Special Fortran Commands
14925 @cindex Special Fortran commands
14927 @value{GDBN} has some commands to support Fortran-specific features,
14928 such as displaying common blocks.
14931 @cindex @code{COMMON} blocks, Fortran
14932 @kindex info common
14933 @item info common @r{[}@var{common-name}@r{]}
14934 This command prints the values contained in the Fortran @code{COMMON}
14935 block whose name is @var{common-name}. With no argument, the names of
14936 all @code{COMMON} blocks visible at the current program location are
14943 @cindex Pascal support in @value{GDBN}, limitations
14944 Debugging Pascal programs which use sets, subranges, file variables, or
14945 nested functions does not currently work. @value{GDBN} does not support
14946 entering expressions, printing values, or similar features using Pascal
14949 The Pascal-specific command @code{set print pascal_static-members}
14950 controls whether static members of Pascal objects are displayed.
14951 @xref{Print Settings, pascal_static-members}.
14954 @subsection Modula-2
14956 @cindex Modula-2, @value{GDBN} support
14958 The extensions made to @value{GDBN} to support Modula-2 only support
14959 output from the @sc{gnu} Modula-2 compiler (which is currently being
14960 developed). Other Modula-2 compilers are not currently supported, and
14961 attempting to debug executables produced by them is most likely
14962 to give an error as @value{GDBN} reads in the executable's symbol
14965 @cindex expressions in Modula-2
14967 * M2 Operators:: Built-in operators
14968 * Built-In Func/Proc:: Built-in functions and procedures
14969 * M2 Constants:: Modula-2 constants
14970 * M2 Types:: Modula-2 types
14971 * M2 Defaults:: Default settings for Modula-2
14972 * Deviations:: Deviations from standard Modula-2
14973 * M2 Checks:: Modula-2 type and range checks
14974 * M2 Scope:: The scope operators @code{::} and @code{.}
14975 * GDB/M2:: @value{GDBN} and Modula-2
14979 @subsubsection Operators
14980 @cindex Modula-2 operators
14982 Operators must be defined on values of specific types. For instance,
14983 @code{+} is defined on numbers, but not on structures. Operators are
14984 often defined on groups of types. For the purposes of Modula-2, the
14985 following definitions hold:
14990 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14994 @emph{Character types} consist of @code{CHAR} and its subranges.
14997 @emph{Floating-point types} consist of @code{REAL}.
15000 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15004 @emph{Scalar types} consist of all of the above.
15007 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15010 @emph{Boolean types} consist of @code{BOOLEAN}.
15014 The following operators are supported, and appear in order of
15015 increasing precedence:
15019 Function argument or array index separator.
15022 Assignment. The value of @var{var} @code{:=} @var{value} is
15026 Less than, greater than on integral, floating-point, or enumerated
15030 Less than or equal to, greater than or equal to
15031 on integral, floating-point and enumerated types, or set inclusion on
15032 set types. Same precedence as @code{<}.
15034 @item =@r{, }<>@r{, }#
15035 Equality and two ways of expressing inequality, valid on scalar types.
15036 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15037 available for inequality, since @code{#} conflicts with the script
15041 Set membership. Defined on set types and the types of their members.
15042 Same precedence as @code{<}.
15045 Boolean disjunction. Defined on boolean types.
15048 Boolean conjunction. Defined on boolean types.
15051 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15054 Addition and subtraction on integral and floating-point types, or union
15055 and difference on set types.
15058 Multiplication on integral and floating-point types, or set intersection
15062 Division on floating-point types, or symmetric set difference on set
15063 types. Same precedence as @code{*}.
15066 Integer division and remainder. Defined on integral types. Same
15067 precedence as @code{*}.
15070 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15073 Pointer dereferencing. Defined on pointer types.
15076 Boolean negation. Defined on boolean types. Same precedence as
15080 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15081 precedence as @code{^}.
15084 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15087 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15091 @value{GDBN} and Modula-2 scope operators.
15095 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15096 treats the use of the operator @code{IN}, or the use of operators
15097 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15098 @code{<=}, and @code{>=} on sets as an error.
15102 @node Built-In Func/Proc
15103 @subsubsection Built-in Functions and Procedures
15104 @cindex Modula-2 built-ins
15106 Modula-2 also makes available several built-in procedures and functions.
15107 In describing these, the following metavariables are used:
15112 represents an @code{ARRAY} variable.
15115 represents a @code{CHAR} constant or variable.
15118 represents a variable or constant of integral type.
15121 represents an identifier that belongs to a set. Generally used in the
15122 same function with the metavariable @var{s}. The type of @var{s} should
15123 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15126 represents a variable or constant of integral or floating-point type.
15129 represents a variable or constant of floating-point type.
15135 represents a variable.
15138 represents a variable or constant of one of many types. See the
15139 explanation of the function for details.
15142 All Modula-2 built-in procedures also return a result, described below.
15146 Returns the absolute value of @var{n}.
15149 If @var{c} is a lower case letter, it returns its upper case
15150 equivalent, otherwise it returns its argument.
15153 Returns the character whose ordinal value is @var{i}.
15156 Decrements the value in the variable @var{v} by one. Returns the new value.
15158 @item DEC(@var{v},@var{i})
15159 Decrements the value in the variable @var{v} by @var{i}. Returns the
15162 @item EXCL(@var{m},@var{s})
15163 Removes the element @var{m} from the set @var{s}. Returns the new
15166 @item FLOAT(@var{i})
15167 Returns the floating point equivalent of the integer @var{i}.
15169 @item HIGH(@var{a})
15170 Returns the index of the last member of @var{a}.
15173 Increments the value in the variable @var{v} by one. Returns the new value.
15175 @item INC(@var{v},@var{i})
15176 Increments the value in the variable @var{v} by @var{i}. Returns the
15179 @item INCL(@var{m},@var{s})
15180 Adds the element @var{m} to the set @var{s} if it is not already
15181 there. Returns the new set.
15184 Returns the maximum value of the type @var{t}.
15187 Returns the minimum value of the type @var{t}.
15190 Returns boolean TRUE if @var{i} is an odd number.
15193 Returns the ordinal value of its argument. For example, the ordinal
15194 value of a character is its @sc{ascii} value (on machines supporting
15195 the @sc{ascii} character set). The argument @var{x} must be of an
15196 ordered type, which include integral, character and enumerated types.
15198 @item SIZE(@var{x})
15199 Returns the size of its argument. The argument @var{x} can be a
15200 variable or a type.
15202 @item TRUNC(@var{r})
15203 Returns the integral part of @var{r}.
15205 @item TSIZE(@var{x})
15206 Returns the size of its argument. The argument @var{x} can be a
15207 variable or a type.
15209 @item VAL(@var{t},@var{i})
15210 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15214 @emph{Warning:} Sets and their operations are not yet supported, so
15215 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15219 @cindex Modula-2 constants
15221 @subsubsection Constants
15223 @value{GDBN} allows you to express the constants of Modula-2 in the following
15229 Integer constants are simply a sequence of digits. When used in an
15230 expression, a constant is interpreted to be type-compatible with the
15231 rest of the expression. Hexadecimal integers are specified by a
15232 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15235 Floating point constants appear as a sequence of digits, followed by a
15236 decimal point and another sequence of digits. An optional exponent can
15237 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15238 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15239 digits of the floating point constant must be valid decimal (base 10)
15243 Character constants consist of a single character enclosed by a pair of
15244 like quotes, either single (@code{'}) or double (@code{"}). They may
15245 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15246 followed by a @samp{C}.
15249 String constants consist of a sequence of characters enclosed by a
15250 pair of like quotes, either single (@code{'}) or double (@code{"}).
15251 Escape sequences in the style of C are also allowed. @xref{C
15252 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15256 Enumerated constants consist of an enumerated identifier.
15259 Boolean constants consist of the identifiers @code{TRUE} and
15263 Pointer constants consist of integral values only.
15266 Set constants are not yet supported.
15270 @subsubsection Modula-2 Types
15271 @cindex Modula-2 types
15273 Currently @value{GDBN} can print the following data types in Modula-2
15274 syntax: array types, record types, set types, pointer types, procedure
15275 types, enumerated types, subrange types and base types. You can also
15276 print the contents of variables declared using these type.
15277 This section gives a number of simple source code examples together with
15278 sample @value{GDBN} sessions.
15280 The first example contains the following section of code:
15289 and you can request @value{GDBN} to interrogate the type and value of
15290 @code{r} and @code{s}.
15293 (@value{GDBP}) print s
15295 (@value{GDBP}) ptype s
15297 (@value{GDBP}) print r
15299 (@value{GDBP}) ptype r
15304 Likewise if your source code declares @code{s} as:
15308 s: SET ['A'..'Z'] ;
15312 then you may query the type of @code{s} by:
15315 (@value{GDBP}) ptype s
15316 type = SET ['A'..'Z']
15320 Note that at present you cannot interactively manipulate set
15321 expressions using the debugger.
15323 The following example shows how you might declare an array in Modula-2
15324 and how you can interact with @value{GDBN} to print its type and contents:
15328 s: ARRAY [-10..10] OF CHAR ;
15332 (@value{GDBP}) ptype s
15333 ARRAY [-10..10] OF CHAR
15336 Note that the array handling is not yet complete and although the type
15337 is printed correctly, expression handling still assumes that all
15338 arrays have a lower bound of zero and not @code{-10} as in the example
15341 Here are some more type related Modula-2 examples:
15345 colour = (blue, red, yellow, green) ;
15346 t = [blue..yellow] ;
15354 The @value{GDBN} interaction shows how you can query the data type
15355 and value of a variable.
15358 (@value{GDBP}) print s
15360 (@value{GDBP}) ptype t
15361 type = [blue..yellow]
15365 In this example a Modula-2 array is declared and its contents
15366 displayed. Observe that the contents are written in the same way as
15367 their @code{C} counterparts.
15371 s: ARRAY [1..5] OF CARDINAL ;
15377 (@value{GDBP}) print s
15378 $1 = @{1, 0, 0, 0, 0@}
15379 (@value{GDBP}) ptype s
15380 type = ARRAY [1..5] OF CARDINAL
15383 The Modula-2 language interface to @value{GDBN} also understands
15384 pointer types as shown in this example:
15388 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15395 and you can request that @value{GDBN} describes the type of @code{s}.
15398 (@value{GDBP}) ptype s
15399 type = POINTER TO ARRAY [1..5] OF CARDINAL
15402 @value{GDBN} handles compound types as we can see in this example.
15403 Here we combine array types, record types, pointer types and subrange
15414 myarray = ARRAY myrange OF CARDINAL ;
15415 myrange = [-2..2] ;
15417 s: POINTER TO ARRAY myrange OF foo ;
15421 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15425 (@value{GDBP}) ptype s
15426 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15429 f3 : ARRAY [-2..2] OF CARDINAL;
15434 @subsubsection Modula-2 Defaults
15435 @cindex Modula-2 defaults
15437 If type and range checking are set automatically by @value{GDBN}, they
15438 both default to @code{on} whenever the working language changes to
15439 Modula-2. This happens regardless of whether you or @value{GDBN}
15440 selected the working language.
15442 If you allow @value{GDBN} to set the language automatically, then entering
15443 code compiled from a file whose name ends with @file{.mod} sets the
15444 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15445 Infer the Source Language}, for further details.
15448 @subsubsection Deviations from Standard Modula-2
15449 @cindex Modula-2, deviations from
15451 A few changes have been made to make Modula-2 programs easier to debug.
15452 This is done primarily via loosening its type strictness:
15456 Unlike in standard Modula-2, pointer constants can be formed by
15457 integers. This allows you to modify pointer variables during
15458 debugging. (In standard Modula-2, the actual address contained in a
15459 pointer variable is hidden from you; it can only be modified
15460 through direct assignment to another pointer variable or expression that
15461 returned a pointer.)
15464 C escape sequences can be used in strings and characters to represent
15465 non-printable characters. @value{GDBN} prints out strings with these
15466 escape sequences embedded. Single non-printable characters are
15467 printed using the @samp{CHR(@var{nnn})} format.
15470 The assignment operator (@code{:=}) returns the value of its right-hand
15474 All built-in procedures both modify @emph{and} return their argument.
15478 @subsubsection Modula-2 Type and Range Checks
15479 @cindex Modula-2 checks
15482 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15485 @c FIXME remove warning when type/range checks added
15487 @value{GDBN} considers two Modula-2 variables type equivalent if:
15491 They are of types that have been declared equivalent via a @code{TYPE
15492 @var{t1} = @var{t2}} statement
15495 They have been declared on the same line. (Note: This is true of the
15496 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15499 As long as type checking is enabled, any attempt to combine variables
15500 whose types are not equivalent is an error.
15502 Range checking is done on all mathematical operations, assignment, array
15503 index bounds, and all built-in functions and procedures.
15506 @subsubsection The Scope Operators @code{::} and @code{.}
15508 @cindex @code{.}, Modula-2 scope operator
15509 @cindex colon, doubled as scope operator
15511 @vindex colon-colon@r{, in Modula-2}
15512 @c Info cannot handle :: but TeX can.
15515 @vindex ::@r{, in Modula-2}
15518 There are a few subtle differences between the Modula-2 scope operator
15519 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15524 @var{module} . @var{id}
15525 @var{scope} :: @var{id}
15529 where @var{scope} is the name of a module or a procedure,
15530 @var{module} the name of a module, and @var{id} is any declared
15531 identifier within your program, except another module.
15533 Using the @code{::} operator makes @value{GDBN} search the scope
15534 specified by @var{scope} for the identifier @var{id}. If it is not
15535 found in the specified scope, then @value{GDBN} searches all scopes
15536 enclosing the one specified by @var{scope}.
15538 Using the @code{.} operator makes @value{GDBN} search the current scope for
15539 the identifier specified by @var{id} that was imported from the
15540 definition module specified by @var{module}. With this operator, it is
15541 an error if the identifier @var{id} was not imported from definition
15542 module @var{module}, or if @var{id} is not an identifier in
15546 @subsubsection @value{GDBN} and Modula-2
15548 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15549 Five subcommands of @code{set print} and @code{show print} apply
15550 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15551 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15552 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15553 analogue in Modula-2.
15555 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15556 with any language, is not useful with Modula-2. Its
15557 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15558 created in Modula-2 as they can in C or C@t{++}. However, because an
15559 address can be specified by an integral constant, the construct
15560 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15562 @cindex @code{#} in Modula-2
15563 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15564 interpreted as the beginning of a comment. Use @code{<>} instead.
15570 The extensions made to @value{GDBN} for Ada only support
15571 output from the @sc{gnu} Ada (GNAT) compiler.
15572 Other Ada compilers are not currently supported, and
15573 attempting to debug executables produced by them is most likely
15577 @cindex expressions in Ada
15579 * Ada Mode Intro:: General remarks on the Ada syntax
15580 and semantics supported by Ada mode
15582 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15583 * Additions to Ada:: Extensions of the Ada expression syntax.
15584 * Overloading support for Ada:: Support for expressions involving overloaded
15586 * Stopping Before Main Program:: Debugging the program during elaboration.
15587 * Ada Exceptions:: Ada Exceptions
15588 * Ada Tasks:: Listing and setting breakpoints in tasks.
15589 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15590 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15592 * Ada Glitches:: Known peculiarities of Ada mode.
15595 @node Ada Mode Intro
15596 @subsubsection Introduction
15597 @cindex Ada mode, general
15599 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15600 syntax, with some extensions.
15601 The philosophy behind the design of this subset is
15605 That @value{GDBN} should provide basic literals and access to operations for
15606 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15607 leaving more sophisticated computations to subprograms written into the
15608 program (which therefore may be called from @value{GDBN}).
15611 That type safety and strict adherence to Ada language restrictions
15612 are not particularly important to the @value{GDBN} user.
15615 That brevity is important to the @value{GDBN} user.
15618 Thus, for brevity, the debugger acts as if all names declared in
15619 user-written packages are directly visible, even if they are not visible
15620 according to Ada rules, thus making it unnecessary to fully qualify most
15621 names with their packages, regardless of context. Where this causes
15622 ambiguity, @value{GDBN} asks the user's intent.
15624 The debugger will start in Ada mode if it detects an Ada main program.
15625 As for other languages, it will enter Ada mode when stopped in a program that
15626 was translated from an Ada source file.
15628 While in Ada mode, you may use `@t{--}' for comments. This is useful
15629 mostly for documenting command files. The standard @value{GDBN} comment
15630 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15631 middle (to allow based literals).
15633 @node Omissions from Ada
15634 @subsubsection Omissions from Ada
15635 @cindex Ada, omissions from
15637 Here are the notable omissions from the subset:
15641 Only a subset of the attributes are supported:
15645 @t{'First}, @t{'Last}, and @t{'Length}
15646 on array objects (not on types and subtypes).
15649 @t{'Min} and @t{'Max}.
15652 @t{'Pos} and @t{'Val}.
15658 @t{'Range} on array objects (not subtypes), but only as the right
15659 operand of the membership (@code{in}) operator.
15662 @t{'Access}, @t{'Unchecked_Access}, and
15663 @t{'Unrestricted_Access} (a GNAT extension).
15671 @code{Characters.Latin_1} are not available and
15672 concatenation is not implemented. Thus, escape characters in strings are
15673 not currently available.
15676 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15677 equality of representations. They will generally work correctly
15678 for strings and arrays whose elements have integer or enumeration types.
15679 They may not work correctly for arrays whose element
15680 types have user-defined equality, for arrays of real values
15681 (in particular, IEEE-conformant floating point, because of negative
15682 zeroes and NaNs), and for arrays whose elements contain unused bits with
15683 indeterminate values.
15686 The other component-by-component array operations (@code{and}, @code{or},
15687 @code{xor}, @code{not}, and relational tests other than equality)
15688 are not implemented.
15691 @cindex array aggregates (Ada)
15692 @cindex record aggregates (Ada)
15693 @cindex aggregates (Ada)
15694 There is limited support for array and record aggregates. They are
15695 permitted only on the right sides of assignments, as in these examples:
15698 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15699 (@value{GDBP}) set An_Array := (1, others => 0)
15700 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15701 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15702 (@value{GDBP}) set A_Record := (1, "Peter", True);
15703 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15707 discriminant's value by assigning an aggregate has an
15708 undefined effect if that discriminant is used within the record.
15709 However, you can first modify discriminants by directly assigning to
15710 them (which normally would not be allowed in Ada), and then performing an
15711 aggregate assignment. For example, given a variable @code{A_Rec}
15712 declared to have a type such as:
15715 type Rec (Len : Small_Integer := 0) is record
15717 Vals : IntArray (1 .. Len);
15721 you can assign a value with a different size of @code{Vals} with two
15725 (@value{GDBP}) set A_Rec.Len := 4
15726 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15729 As this example also illustrates, @value{GDBN} is very loose about the usual
15730 rules concerning aggregates. You may leave out some of the
15731 components of an array or record aggregate (such as the @code{Len}
15732 component in the assignment to @code{A_Rec} above); they will retain their
15733 original values upon assignment. You may freely use dynamic values as
15734 indices in component associations. You may even use overlapping or
15735 redundant component associations, although which component values are
15736 assigned in such cases is not defined.
15739 Calls to dispatching subprograms are not implemented.
15742 The overloading algorithm is much more limited (i.e., less selective)
15743 than that of real Ada. It makes only limited use of the context in
15744 which a subexpression appears to resolve its meaning, and it is much
15745 looser in its rules for allowing type matches. As a result, some
15746 function calls will be ambiguous, and the user will be asked to choose
15747 the proper resolution.
15750 The @code{new} operator is not implemented.
15753 Entry calls are not implemented.
15756 Aside from printing, arithmetic operations on the native VAX floating-point
15757 formats are not supported.
15760 It is not possible to slice a packed array.
15763 The names @code{True} and @code{False}, when not part of a qualified name,
15764 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15766 Should your program
15767 redefine these names in a package or procedure (at best a dubious practice),
15768 you will have to use fully qualified names to access their new definitions.
15771 @node Additions to Ada
15772 @subsubsection Additions to Ada
15773 @cindex Ada, deviations from
15775 As it does for other languages, @value{GDBN} makes certain generic
15776 extensions to Ada (@pxref{Expressions}):
15780 If the expression @var{E} is a variable residing in memory (typically
15781 a local variable or array element) and @var{N} is a positive integer,
15782 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15783 @var{N}-1 adjacent variables following it in memory as an array. In
15784 Ada, this operator is generally not necessary, since its prime use is
15785 in displaying parts of an array, and slicing will usually do this in
15786 Ada. However, there are occasional uses when debugging programs in
15787 which certain debugging information has been optimized away.
15790 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15791 appears in function or file @var{B}.'' When @var{B} is a file name,
15792 you must typically surround it in single quotes.
15795 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15796 @var{type} that appears at address @var{addr}.''
15799 A name starting with @samp{$} is a convenience variable
15800 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15803 In addition, @value{GDBN} provides a few other shortcuts and outright
15804 additions specific to Ada:
15808 The assignment statement is allowed as an expression, returning
15809 its right-hand operand as its value. Thus, you may enter
15812 (@value{GDBP}) set x := y + 3
15813 (@value{GDBP}) print A(tmp := y + 1)
15817 The semicolon is allowed as an ``operator,'' returning as its value
15818 the value of its right-hand operand.
15819 This allows, for example,
15820 complex conditional breaks:
15823 (@value{GDBP}) break f
15824 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15828 Rather than use catenation and symbolic character names to introduce special
15829 characters into strings, one may instead use a special bracket notation,
15830 which is also used to print strings. A sequence of characters of the form
15831 @samp{["@var{XX}"]} within a string or character literal denotes the
15832 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15833 sequence of characters @samp{["""]} also denotes a single quotation mark
15834 in strings. For example,
15836 "One line.["0a"]Next line.["0a"]"
15839 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15843 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15844 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15848 (@value{GDBP}) print 'max(x, y)
15852 When printing arrays, @value{GDBN} uses positional notation when the
15853 array has a lower bound of 1, and uses a modified named notation otherwise.
15854 For example, a one-dimensional array of three integers with a lower bound
15855 of 3 might print as
15862 That is, in contrast to valid Ada, only the first component has a @code{=>}
15866 You may abbreviate attributes in expressions with any unique,
15867 multi-character subsequence of
15868 their names (an exact match gets preference).
15869 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15870 in place of @t{a'length}.
15873 @cindex quoting Ada internal identifiers
15874 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15875 to lower case. The GNAT compiler uses upper-case characters for
15876 some of its internal identifiers, which are normally of no interest to users.
15877 For the rare occasions when you actually have to look at them,
15878 enclose them in angle brackets to avoid the lower-case mapping.
15881 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15885 Printing an object of class-wide type or dereferencing an
15886 access-to-class-wide value will display all the components of the object's
15887 specific type (as indicated by its run-time tag). Likewise, component
15888 selection on such a value will operate on the specific type of the
15893 @node Overloading support for Ada
15894 @subsubsection Overloading support for Ada
15895 @cindex overloading, Ada
15897 The debugger supports limited overloading. Given a subprogram call in which
15898 the function symbol has multiple definitions, it will use the number of
15899 actual parameters and some information about their types to attempt to narrow
15900 the set of definitions. It also makes very limited use of context, preferring
15901 procedures to functions in the context of the @code{call} command, and
15902 functions to procedures elsewhere.
15904 If, after narrowing, the set of matching definitions still contains more than
15905 one definition, @value{GDBN} will display a menu to query which one it should
15909 (@value{GDBP}) print f(1)
15910 Multiple matches for f
15912 [1] foo.f (integer) return boolean at foo.adb:23
15913 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
15917 In this case, just select one menu entry either to cancel expression evaluation
15918 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
15919 instance (type the corresponding number and press @key{RET}).
15921 Here are a couple of commands to customize @value{GDBN}'s behavior in this
15926 @kindex set ada print-signatures
15927 @item set ada print-signatures
15928 Control whether parameter types and return types are displayed in overloads
15929 selection menus. It is @code{on} by default.
15930 @xref{Overloading support for Ada}.
15932 @kindex show ada print-signatures
15933 @item show ada print-signatures
15934 Show the current setting for displaying parameter types and return types in
15935 overloads selection menu.
15936 @xref{Overloading support for Ada}.
15940 @node Stopping Before Main Program
15941 @subsubsection Stopping at the Very Beginning
15943 @cindex breakpointing Ada elaboration code
15944 It is sometimes necessary to debug the program during elaboration, and
15945 before reaching the main procedure.
15946 As defined in the Ada Reference
15947 Manual, the elaboration code is invoked from a procedure called
15948 @code{adainit}. To run your program up to the beginning of
15949 elaboration, simply use the following two commands:
15950 @code{tbreak adainit} and @code{run}.
15952 @node Ada Exceptions
15953 @subsubsection Ada Exceptions
15955 A command is provided to list all Ada exceptions:
15958 @kindex info exceptions
15959 @item info exceptions
15960 @itemx info exceptions @var{regexp}
15961 The @code{info exceptions} command allows you to list all Ada exceptions
15962 defined within the program being debugged, as well as their addresses.
15963 With a regular expression, @var{regexp}, as argument, only those exceptions
15964 whose names match @var{regexp} are listed.
15967 Below is a small example, showing how the command can be used, first
15968 without argument, and next with a regular expression passed as an
15972 (@value{GDBP}) info exceptions
15973 All defined Ada exceptions:
15974 constraint_error: 0x613da0
15975 program_error: 0x613d20
15976 storage_error: 0x613ce0
15977 tasking_error: 0x613ca0
15978 const.aint_global_e: 0x613b00
15979 (@value{GDBP}) info exceptions const.aint
15980 All Ada exceptions matching regular expression "const.aint":
15981 constraint_error: 0x613da0
15982 const.aint_global_e: 0x613b00
15985 It is also possible to ask @value{GDBN} to stop your program's execution
15986 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15989 @subsubsection Extensions for Ada Tasks
15990 @cindex Ada, tasking
15992 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15993 @value{GDBN} provides the following task-related commands:
15998 This command shows a list of current Ada tasks, as in the following example:
16005 (@value{GDBP}) info tasks
16006 ID TID P-ID Pri State Name
16007 1 8088000 0 15 Child Activation Wait main_task
16008 2 80a4000 1 15 Accept Statement b
16009 3 809a800 1 15 Child Activation Wait a
16010 * 4 80ae800 3 15 Runnable c
16015 In this listing, the asterisk before the last task indicates it to be the
16016 task currently being inspected.
16020 Represents @value{GDBN}'s internal task number.
16026 The parent's task ID (@value{GDBN}'s internal task number).
16029 The base priority of the task.
16032 Current state of the task.
16036 The task has been created but has not been activated. It cannot be
16040 The task is not blocked for any reason known to Ada. (It may be waiting
16041 for a mutex, though.) It is conceptually "executing" in normal mode.
16044 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16045 that were waiting on terminate alternatives have been awakened and have
16046 terminated themselves.
16048 @item Child Activation Wait
16049 The task is waiting for created tasks to complete activation.
16051 @item Accept Statement
16052 The task is waiting on an accept or selective wait statement.
16054 @item Waiting on entry call
16055 The task is waiting on an entry call.
16057 @item Async Select Wait
16058 The task is waiting to start the abortable part of an asynchronous
16062 The task is waiting on a select statement with only a delay
16065 @item Child Termination Wait
16066 The task is sleeping having completed a master within itself, and is
16067 waiting for the tasks dependent on that master to become terminated or
16068 waiting on a terminate Phase.
16070 @item Wait Child in Term Alt
16071 The task is sleeping waiting for tasks on terminate alternatives to
16072 finish terminating.
16074 @item Accepting RV with @var{taskno}
16075 The task is accepting a rendez-vous with the task @var{taskno}.
16079 Name of the task in the program.
16083 @kindex info task @var{taskno}
16084 @item info task @var{taskno}
16085 This command shows detailled informations on the specified task, as in
16086 the following example:
16091 (@value{GDBP}) info tasks
16092 ID TID P-ID Pri State Name
16093 1 8077880 0 15 Child Activation Wait main_task
16094 * 2 807c468 1 15 Runnable task_1
16095 (@value{GDBP}) info task 2
16096 Ada Task: 0x807c468
16099 Parent: 1 (main_task)
16105 @kindex task@r{ (Ada)}
16106 @cindex current Ada task ID
16107 This command prints the ID of the current task.
16113 (@value{GDBP}) info tasks
16114 ID TID P-ID Pri State Name
16115 1 8077870 0 15 Child Activation Wait main_task
16116 * 2 807c458 1 15 Runnable t
16117 (@value{GDBP}) task
16118 [Current task is 2]
16121 @item task @var{taskno}
16122 @cindex Ada task switching
16123 This command is like the @code{thread @var{threadno}}
16124 command (@pxref{Threads}). It switches the context of debugging
16125 from the current task to the given task.
16131 (@value{GDBP}) info tasks
16132 ID TID P-ID Pri State Name
16133 1 8077870 0 15 Child Activation Wait main_task
16134 * 2 807c458 1 15 Runnable t
16135 (@value{GDBP}) task 1
16136 [Switching to task 1]
16137 #0 0x8067726 in pthread_cond_wait ()
16139 #0 0x8067726 in pthread_cond_wait ()
16140 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16141 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16142 #3 0x806153e in system.tasking.stages.activate_tasks ()
16143 #4 0x804aacc in un () at un.adb:5
16146 @item break @var{location} task @var{taskno}
16147 @itemx break @var{location} task @var{taskno} if @dots{}
16148 @cindex breakpoints and tasks, in Ada
16149 @cindex task breakpoints, in Ada
16150 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16151 These commands are like the @code{break @dots{} thread @dots{}}
16152 command (@pxref{Thread Stops}). The
16153 @var{location} argument specifies source lines, as described
16154 in @ref{Specify Location}.
16156 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16157 to specify that you only want @value{GDBN} to stop the program when a
16158 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16159 numeric task identifiers assigned by @value{GDBN}, shown in the first
16160 column of the @samp{info tasks} display.
16162 If you do not specify @samp{task @var{taskno}} when you set a
16163 breakpoint, the breakpoint applies to @emph{all} tasks of your
16166 You can use the @code{task} qualifier on conditional breakpoints as
16167 well; in this case, place @samp{task @var{taskno}} before the
16168 breakpoint condition (before the @code{if}).
16176 (@value{GDBP}) info tasks
16177 ID TID P-ID Pri State Name
16178 1 140022020 0 15 Child Activation Wait main_task
16179 2 140045060 1 15 Accept/Select Wait t2
16180 3 140044840 1 15 Runnable t1
16181 * 4 140056040 1 15 Runnable t3
16182 (@value{GDBP}) b 15 task 2
16183 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16184 (@value{GDBP}) cont
16189 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16191 (@value{GDBP}) info tasks
16192 ID TID P-ID Pri State Name
16193 1 140022020 0 15 Child Activation Wait main_task
16194 * 2 140045060 1 15 Runnable t2
16195 3 140044840 1 15 Runnable t1
16196 4 140056040 1 15 Delay Sleep t3
16200 @node Ada Tasks and Core Files
16201 @subsubsection Tasking Support when Debugging Core Files
16202 @cindex Ada tasking and core file debugging
16204 When inspecting a core file, as opposed to debugging a live program,
16205 tasking support may be limited or even unavailable, depending on
16206 the platform being used.
16207 For instance, on x86-linux, the list of tasks is available, but task
16208 switching is not supported.
16210 On certain platforms, the debugger needs to perform some
16211 memory writes in order to provide Ada tasking support. When inspecting
16212 a core file, this means that the core file must be opened with read-write
16213 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16214 Under these circumstances, you should make a backup copy of the core
16215 file before inspecting it with @value{GDBN}.
16217 @node Ravenscar Profile
16218 @subsubsection Tasking Support when using the Ravenscar Profile
16219 @cindex Ravenscar Profile
16221 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16222 specifically designed for systems with safety-critical real-time
16226 @kindex set ravenscar task-switching on
16227 @cindex task switching with program using Ravenscar Profile
16228 @item set ravenscar task-switching on
16229 Allows task switching when debugging a program that uses the Ravenscar
16230 Profile. This is the default.
16232 @kindex set ravenscar task-switching off
16233 @item set ravenscar task-switching off
16234 Turn off task switching when debugging a program that uses the Ravenscar
16235 Profile. This is mostly intended to disable the code that adds support
16236 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16237 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16238 To be effective, this command should be run before the program is started.
16240 @kindex show ravenscar task-switching
16241 @item show ravenscar task-switching
16242 Show whether it is possible to switch from task to task in a program
16243 using the Ravenscar Profile.
16248 @subsubsection Known Peculiarities of Ada Mode
16249 @cindex Ada, problems
16251 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16252 we know of several problems with and limitations of Ada mode in
16254 some of which will be fixed with planned future releases of the debugger
16255 and the GNU Ada compiler.
16259 Static constants that the compiler chooses not to materialize as objects in
16260 storage are invisible to the debugger.
16263 Named parameter associations in function argument lists are ignored (the
16264 argument lists are treated as positional).
16267 Many useful library packages are currently invisible to the debugger.
16270 Fixed-point arithmetic, conversions, input, and output is carried out using
16271 floating-point arithmetic, and may give results that only approximate those on
16275 The GNAT compiler never generates the prefix @code{Standard} for any of
16276 the standard symbols defined by the Ada language. @value{GDBN} knows about
16277 this: it will strip the prefix from names when you use it, and will never
16278 look for a name you have so qualified among local symbols, nor match against
16279 symbols in other packages or subprograms. If you have
16280 defined entities anywhere in your program other than parameters and
16281 local variables whose simple names match names in @code{Standard},
16282 GNAT's lack of qualification here can cause confusion. When this happens,
16283 you can usually resolve the confusion
16284 by qualifying the problematic names with package
16285 @code{Standard} explicitly.
16288 Older versions of the compiler sometimes generate erroneous debugging
16289 information, resulting in the debugger incorrectly printing the value
16290 of affected entities. In some cases, the debugger is able to work
16291 around an issue automatically. In other cases, the debugger is able
16292 to work around the issue, but the work-around has to be specifically
16295 @kindex set ada trust-PAD-over-XVS
16296 @kindex show ada trust-PAD-over-XVS
16299 @item set ada trust-PAD-over-XVS on
16300 Configure GDB to strictly follow the GNAT encoding when computing the
16301 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16302 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16303 a complete description of the encoding used by the GNAT compiler).
16304 This is the default.
16306 @item set ada trust-PAD-over-XVS off
16307 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16308 sometimes prints the wrong value for certain entities, changing @code{ada
16309 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16310 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16311 @code{off}, but this incurs a slight performance penalty, so it is
16312 recommended to leave this setting to @code{on} unless necessary.
16316 @cindex GNAT descriptive types
16317 @cindex GNAT encoding
16318 Internally, the debugger also relies on the compiler following a number
16319 of conventions known as the @samp{GNAT Encoding}, all documented in
16320 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16321 how the debugging information should be generated for certain types.
16322 In particular, this convention makes use of @dfn{descriptive types},
16323 which are artificial types generated purely to help the debugger.
16325 These encodings were defined at a time when the debugging information
16326 format used was not powerful enough to describe some of the more complex
16327 types available in Ada. Since DWARF allows us to express nearly all
16328 Ada features, the long-term goal is to slowly replace these descriptive
16329 types by their pure DWARF equivalent. To facilitate that transition,
16330 a new maintenance option is available to force the debugger to ignore
16331 those descriptive types. It allows the user to quickly evaluate how
16332 well @value{GDBN} works without them.
16336 @kindex maint ada set ignore-descriptive-types
16337 @item maintenance ada set ignore-descriptive-types [on|off]
16338 Control whether the debugger should ignore descriptive types.
16339 The default is not to ignore descriptives types (@code{off}).
16341 @kindex maint ada show ignore-descriptive-types
16342 @item maintenance ada show ignore-descriptive-types
16343 Show if descriptive types are ignored by @value{GDBN}.
16347 @node Unsupported Languages
16348 @section Unsupported Languages
16350 @cindex unsupported languages
16351 @cindex minimal language
16352 In addition to the other fully-supported programming languages,
16353 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16354 It does not represent a real programming language, but provides a set
16355 of capabilities close to what the C or assembly languages provide.
16356 This should allow most simple operations to be performed while debugging
16357 an application that uses a language currently not supported by @value{GDBN}.
16359 If the language is set to @code{auto}, @value{GDBN} will automatically
16360 select this language if the current frame corresponds to an unsupported
16364 @chapter Examining the Symbol Table
16366 The commands described in this chapter allow you to inquire about the
16367 symbols (names of variables, functions and types) defined in your
16368 program. This information is inherent in the text of your program and
16369 does not change as your program executes. @value{GDBN} finds it in your
16370 program's symbol table, in the file indicated when you started @value{GDBN}
16371 (@pxref{File Options, ,Choosing Files}), or by one of the
16372 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16374 @cindex symbol names
16375 @cindex names of symbols
16376 @cindex quoting names
16377 Occasionally, you may need to refer to symbols that contain unusual
16378 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16379 most frequent case is in referring to static variables in other
16380 source files (@pxref{Variables,,Program Variables}). File names
16381 are recorded in object files as debugging symbols, but @value{GDBN} would
16382 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16383 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16384 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16391 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16394 @cindex case-insensitive symbol names
16395 @cindex case sensitivity in symbol names
16396 @kindex set case-sensitive
16397 @item set case-sensitive on
16398 @itemx set case-sensitive off
16399 @itemx set case-sensitive auto
16400 Normally, when @value{GDBN} looks up symbols, it matches their names
16401 with case sensitivity determined by the current source language.
16402 Occasionally, you may wish to control that. The command @code{set
16403 case-sensitive} lets you do that by specifying @code{on} for
16404 case-sensitive matches or @code{off} for case-insensitive ones. If
16405 you specify @code{auto}, case sensitivity is reset to the default
16406 suitable for the source language. The default is case-sensitive
16407 matches for all languages except for Fortran, for which the default is
16408 case-insensitive matches.
16410 @kindex show case-sensitive
16411 @item show case-sensitive
16412 This command shows the current setting of case sensitivity for symbols
16415 @kindex set print type methods
16416 @item set print type methods
16417 @itemx set print type methods on
16418 @itemx set print type methods off
16419 Normally, when @value{GDBN} prints a class, it displays any methods
16420 declared in that class. You can control this behavior either by
16421 passing the appropriate flag to @code{ptype}, or using @command{set
16422 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16423 display the methods; this is the default. Specifying @code{off} will
16424 cause @value{GDBN} to omit the methods.
16426 @kindex show print type methods
16427 @item show print type methods
16428 This command shows the current setting of method display when printing
16431 @kindex set print type typedefs
16432 @item set print type typedefs
16433 @itemx set print type typedefs on
16434 @itemx set print type typedefs off
16436 Normally, when @value{GDBN} prints a class, it displays any typedefs
16437 defined in that class. You can control this behavior either by
16438 passing the appropriate flag to @code{ptype}, or using @command{set
16439 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16440 display the typedef definitions; this is the default. Specifying
16441 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16442 Note that this controls whether the typedef definition itself is
16443 printed, not whether typedef names are substituted when printing other
16446 @kindex show print type typedefs
16447 @item show print type typedefs
16448 This command shows the current setting of typedef display when
16451 @kindex info address
16452 @cindex address of a symbol
16453 @item info address @var{symbol}
16454 Describe where the data for @var{symbol} is stored. For a register
16455 variable, this says which register it is kept in. For a non-register
16456 local variable, this prints the stack-frame offset at which the variable
16459 Note the contrast with @samp{print &@var{symbol}}, which does not work
16460 at all for a register variable, and for a stack local variable prints
16461 the exact address of the current instantiation of the variable.
16463 @kindex info symbol
16464 @cindex symbol from address
16465 @cindex closest symbol and offset for an address
16466 @item info symbol @var{addr}
16467 Print the name of a symbol which is stored at the address @var{addr}.
16468 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16469 nearest symbol and an offset from it:
16472 (@value{GDBP}) info symbol 0x54320
16473 _initialize_vx + 396 in section .text
16477 This is the opposite of the @code{info address} command. You can use
16478 it to find out the name of a variable or a function given its address.
16480 For dynamically linked executables, the name of executable or shared
16481 library containing the symbol is also printed:
16484 (@value{GDBP}) info symbol 0x400225
16485 _start + 5 in section .text of /tmp/a.out
16486 (@value{GDBP}) info symbol 0x2aaaac2811cf
16487 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16492 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16493 Demangle @var{name}.
16494 If @var{language} is provided it is the name of the language to demangle
16495 @var{name} in. Otherwise @var{name} is demangled in the current language.
16497 The @samp{--} option specifies the end of options,
16498 and is useful when @var{name} begins with a dash.
16500 The parameter @code{demangle-style} specifies how to interpret the kind
16501 of mangling used. @xref{Print Settings}.
16504 @item whatis[/@var{flags}] [@var{arg}]
16505 Print the data type of @var{arg}, which can be either an expression
16506 or a name of a data type. With no argument, print the data type of
16507 @code{$}, the last value in the value history.
16509 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16510 is not actually evaluated, and any side-effecting operations (such as
16511 assignments or function calls) inside it do not take place.
16513 If @var{arg} is a variable or an expression, @code{whatis} prints its
16514 literal type as it is used in the source code. If the type was
16515 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16516 the data type underlying the @code{typedef}. If the type of the
16517 variable or the expression is a compound data type, such as
16518 @code{struct} or @code{class}, @code{whatis} never prints their
16519 fields or methods. It just prints the @code{struct}/@code{class}
16520 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16521 such a compound data type, use @code{ptype}.
16523 If @var{arg} is a type name that was defined using @code{typedef},
16524 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16525 Unrolling means that @code{whatis} will show the underlying type used
16526 in the @code{typedef} declaration of @var{arg}. However, if that
16527 underlying type is also a @code{typedef}, @code{whatis} will not
16530 For C code, the type names may also have the form @samp{class
16531 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16532 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16534 @var{flags} can be used to modify how the type is displayed.
16535 Available flags are:
16539 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16540 parameters and typedefs defined in a class when printing the class'
16541 members. The @code{/r} flag disables this.
16544 Do not print methods defined in the class.
16547 Print methods defined in the class. This is the default, but the flag
16548 exists in case you change the default with @command{set print type methods}.
16551 Do not print typedefs defined in the class. Note that this controls
16552 whether the typedef definition itself is printed, not whether typedef
16553 names are substituted when printing other types.
16556 Print typedefs defined in the class. This is the default, but the flag
16557 exists in case you change the default with @command{set print type typedefs}.
16561 @item ptype[/@var{flags}] [@var{arg}]
16562 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16563 detailed description of the type, instead of just the name of the type.
16564 @xref{Expressions, ,Expressions}.
16566 Contrary to @code{whatis}, @code{ptype} always unrolls any
16567 @code{typedef}s in its argument declaration, whether the argument is
16568 a variable, expression, or a data type. This means that @code{ptype}
16569 of a variable or an expression will not print literally its type as
16570 present in the source code---use @code{whatis} for that. @code{typedef}s at
16571 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16572 fields, methods and inner @code{class typedef}s of @code{struct}s,
16573 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16575 For example, for this variable declaration:
16578 typedef double real_t;
16579 struct complex @{ real_t real; double imag; @};
16580 typedef struct complex complex_t;
16582 real_t *real_pointer_var;
16586 the two commands give this output:
16590 (@value{GDBP}) whatis var
16592 (@value{GDBP}) ptype var
16593 type = struct complex @{
16597 (@value{GDBP}) whatis complex_t
16598 type = struct complex
16599 (@value{GDBP}) whatis struct complex
16600 type = struct complex
16601 (@value{GDBP}) ptype struct complex
16602 type = struct complex @{
16606 (@value{GDBP}) whatis real_pointer_var
16608 (@value{GDBP}) ptype real_pointer_var
16614 As with @code{whatis}, using @code{ptype} without an argument refers to
16615 the type of @code{$}, the last value in the value history.
16617 @cindex incomplete type
16618 Sometimes, programs use opaque data types or incomplete specifications
16619 of complex data structure. If the debug information included in the
16620 program does not allow @value{GDBN} to display a full declaration of
16621 the data type, it will say @samp{<incomplete type>}. For example,
16622 given these declarations:
16626 struct foo *fooptr;
16630 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16633 (@value{GDBP}) ptype foo
16634 $1 = <incomplete type>
16638 ``Incomplete type'' is C terminology for data types that are not
16639 completely specified.
16642 @item info types @var{regexp}
16644 Print a brief description of all types whose names match the regular
16645 expression @var{regexp} (or all types in your program, if you supply
16646 no argument). Each complete typename is matched as though it were a
16647 complete line; thus, @samp{i type value} gives information on all
16648 types in your program whose names include the string @code{value}, but
16649 @samp{i type ^value$} gives information only on types whose complete
16650 name is @code{value}.
16652 This command differs from @code{ptype} in two ways: first, like
16653 @code{whatis}, it does not print a detailed description; second, it
16654 lists all source files where a type is defined.
16656 @kindex info type-printers
16657 @item info type-printers
16658 Versions of @value{GDBN} that ship with Python scripting enabled may
16659 have ``type printers'' available. When using @command{ptype} or
16660 @command{whatis}, these printers are consulted when the name of a type
16661 is needed. @xref{Type Printing API}, for more information on writing
16664 @code{info type-printers} displays all the available type printers.
16666 @kindex enable type-printer
16667 @kindex disable type-printer
16668 @item enable type-printer @var{name}@dots{}
16669 @item disable type-printer @var{name}@dots{}
16670 These commands can be used to enable or disable type printers.
16673 @cindex local variables
16674 @item info scope @var{location}
16675 List all the variables local to a particular scope. This command
16676 accepts a @var{location} argument---a function name, a source line, or
16677 an address preceded by a @samp{*}, and prints all the variables local
16678 to the scope defined by that location. (@xref{Specify Location}, for
16679 details about supported forms of @var{location}.) For example:
16682 (@value{GDBP}) @b{info scope command_line_handler}
16683 Scope for command_line_handler:
16684 Symbol rl is an argument at stack/frame offset 8, length 4.
16685 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16686 Symbol linelength is in static storage at address 0x150a1c, length 4.
16687 Symbol p is a local variable in register $esi, length 4.
16688 Symbol p1 is a local variable in register $ebx, length 4.
16689 Symbol nline is a local variable in register $edx, length 4.
16690 Symbol repeat is a local variable at frame offset -8, length 4.
16694 This command is especially useful for determining what data to collect
16695 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16698 @kindex info source
16700 Show information about the current source file---that is, the source file for
16701 the function containing the current point of execution:
16704 the name of the source file, and the directory containing it,
16706 the directory it was compiled in,
16708 its length, in lines,
16710 which programming language it is written in,
16712 if the debug information provides it, the program that compiled the file
16713 (which may include, e.g., the compiler version and command line arguments),
16715 whether the executable includes debugging information for that file, and
16716 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16718 whether the debugging information includes information about
16719 preprocessor macros.
16723 @kindex info sources
16725 Print the names of all source files in your program for which there is
16726 debugging information, organized into two lists: files whose symbols
16727 have already been read, and files whose symbols will be read when needed.
16729 @kindex info functions
16730 @item info functions
16731 Print the names and data types of all defined functions.
16733 @item info functions @var{regexp}
16734 Print the names and data types of all defined functions
16735 whose names contain a match for regular expression @var{regexp}.
16736 Thus, @samp{info fun step} finds all functions whose names
16737 include @code{step}; @samp{info fun ^step} finds those whose names
16738 start with @code{step}. If a function name contains characters
16739 that conflict with the regular expression language (e.g.@:
16740 @samp{operator*()}), they may be quoted with a backslash.
16742 @kindex info variables
16743 @item info variables
16744 Print the names and data types of all variables that are defined
16745 outside of functions (i.e.@: excluding local variables).
16747 @item info variables @var{regexp}
16748 Print the names and data types of all variables (except for local
16749 variables) whose names contain a match for regular expression
16752 @kindex info classes
16753 @cindex Objective-C, classes and selectors
16755 @itemx info classes @var{regexp}
16756 Display all Objective-C classes in your program, or
16757 (with the @var{regexp} argument) all those matching a particular regular
16760 @kindex info selectors
16761 @item info selectors
16762 @itemx info selectors @var{regexp}
16763 Display all Objective-C selectors in your program, or
16764 (with the @var{regexp} argument) all those matching a particular regular
16768 This was never implemented.
16769 @kindex info methods
16771 @itemx info methods @var{regexp}
16772 The @code{info methods} command permits the user to examine all defined
16773 methods within C@t{++} program, or (with the @var{regexp} argument) a
16774 specific set of methods found in the various C@t{++} classes. Many
16775 C@t{++} classes provide a large number of methods. Thus, the output
16776 from the @code{ptype} command can be overwhelming and hard to use. The
16777 @code{info-methods} command filters the methods, printing only those
16778 which match the regular-expression @var{regexp}.
16781 @cindex opaque data types
16782 @kindex set opaque-type-resolution
16783 @item set opaque-type-resolution on
16784 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16785 declared as a pointer to a @code{struct}, @code{class}, or
16786 @code{union}---for example, @code{struct MyType *}---that is used in one
16787 source file although the full declaration of @code{struct MyType} is in
16788 another source file. The default is on.
16790 A change in the setting of this subcommand will not take effect until
16791 the next time symbols for a file are loaded.
16793 @item set opaque-type-resolution off
16794 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16795 is printed as follows:
16797 @{<no data fields>@}
16800 @kindex show opaque-type-resolution
16801 @item show opaque-type-resolution
16802 Show whether opaque types are resolved or not.
16804 @kindex set print symbol-loading
16805 @cindex print messages when symbols are loaded
16806 @item set print symbol-loading
16807 @itemx set print symbol-loading full
16808 @itemx set print symbol-loading brief
16809 @itemx set print symbol-loading off
16810 The @code{set print symbol-loading} command allows you to control the
16811 printing of messages when @value{GDBN} loads symbol information.
16812 By default a message is printed for the executable and one for each
16813 shared library, and normally this is what you want. However, when
16814 debugging apps with large numbers of shared libraries these messages
16816 When set to @code{brief} a message is printed for each executable,
16817 and when @value{GDBN} loads a collection of shared libraries at once
16818 it will only print one message regardless of the number of shared
16819 libraries. When set to @code{off} no messages are printed.
16821 @kindex show print symbol-loading
16822 @item show print symbol-loading
16823 Show whether messages will be printed when a @value{GDBN} command
16824 entered from the keyboard causes symbol information to be loaded.
16826 @kindex maint print symbols
16827 @cindex symbol dump
16828 @kindex maint print psymbols
16829 @cindex partial symbol dump
16830 @kindex maint print msymbols
16831 @cindex minimal symbol dump
16832 @item maint print symbols @var{filename}
16833 @itemx maint print psymbols @var{filename}
16834 @itemx maint print msymbols @var{filename}
16835 Write a dump of debugging symbol data into the file @var{filename}.
16836 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16837 symbols with debugging data are included. If you use @samp{maint print
16838 symbols}, @value{GDBN} includes all the symbols for which it has already
16839 collected full details: that is, @var{filename} reflects symbols for
16840 only those files whose symbols @value{GDBN} has read. You can use the
16841 command @code{info sources} to find out which files these are. If you
16842 use @samp{maint print psymbols} instead, the dump shows information about
16843 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16844 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16845 @samp{maint print msymbols} dumps just the minimal symbol information
16846 required for each object file from which @value{GDBN} has read some symbols.
16847 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16848 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16850 @kindex maint info symtabs
16851 @kindex maint info psymtabs
16852 @cindex listing @value{GDBN}'s internal symbol tables
16853 @cindex symbol tables, listing @value{GDBN}'s internal
16854 @cindex full symbol tables, listing @value{GDBN}'s internal
16855 @cindex partial symbol tables, listing @value{GDBN}'s internal
16856 @item maint info symtabs @r{[} @var{regexp} @r{]}
16857 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16859 List the @code{struct symtab} or @code{struct partial_symtab}
16860 structures whose names match @var{regexp}. If @var{regexp} is not
16861 given, list them all. The output includes expressions which you can
16862 copy into a @value{GDBN} debugging this one to examine a particular
16863 structure in more detail. For example:
16866 (@value{GDBP}) maint info psymtabs dwarf2read
16867 @{ objfile /home/gnu/build/gdb/gdb
16868 ((struct objfile *) 0x82e69d0)
16869 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16870 ((struct partial_symtab *) 0x8474b10)
16873 text addresses 0x814d3c8 -- 0x8158074
16874 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16875 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16876 dependencies (none)
16879 (@value{GDBP}) maint info symtabs
16883 We see that there is one partial symbol table whose filename contains
16884 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16885 and we see that @value{GDBN} has not read in any symtabs yet at all.
16886 If we set a breakpoint on a function, that will cause @value{GDBN} to
16887 read the symtab for the compilation unit containing that function:
16890 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16891 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16893 (@value{GDBP}) maint info symtabs
16894 @{ objfile /home/gnu/build/gdb/gdb
16895 ((struct objfile *) 0x82e69d0)
16896 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16897 ((struct symtab *) 0x86c1f38)
16900 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16901 linetable ((struct linetable *) 0x8370fa0)
16902 debugformat DWARF 2
16908 @kindex maint set symbol-cache-size
16909 @cindex symbol cache size
16910 @item maint set symbol-cache-size @var{size}
16911 Set the size of the symbol cache to @var{size}.
16912 The default size is intended to be good enough for debugging
16913 most applications. This option exists to allow for experimenting
16914 with different sizes.
16916 @kindex maint show symbol-cache-size
16917 @item maint show symbol-cache-size
16918 Show the size of the symbol cache.
16920 @kindex maint print symbol-cache
16921 @cindex symbol cache, printing its contents
16922 @item maint print symbol-cache
16923 Print the contents of the symbol cache.
16924 This is useful when debugging symbol cache issues.
16926 @kindex maint print symbol-cache-statistics
16927 @cindex symbol cache, printing usage statistics
16928 @item maint print symbol-cache-statistics
16929 Print symbol cache usage statistics.
16930 This helps determine how well the cache is being utilized.
16932 @kindex maint flush-symbol-cache
16933 @cindex symbol cache, flushing
16934 @item maint flush-symbol-cache
16935 Flush the contents of the symbol cache, all entries are removed.
16936 This command is useful when debugging the symbol cache.
16937 It is also useful when collecting performance data.
16942 @chapter Altering Execution
16944 Once you think you have found an error in your program, you might want to
16945 find out for certain whether correcting the apparent error would lead to
16946 correct results in the rest of the run. You can find the answer by
16947 experiment, using the @value{GDBN} features for altering execution of the
16950 For example, you can store new values into variables or memory
16951 locations, give your program a signal, restart it at a different
16952 address, or even return prematurely from a function.
16955 * Assignment:: Assignment to variables
16956 * Jumping:: Continuing at a different address
16957 * Signaling:: Giving your program a signal
16958 * Returning:: Returning from a function
16959 * Calling:: Calling your program's functions
16960 * Patching:: Patching your program
16961 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
16965 @section Assignment to Variables
16968 @cindex setting variables
16969 To alter the value of a variable, evaluate an assignment expression.
16970 @xref{Expressions, ,Expressions}. For example,
16977 stores the value 4 into the variable @code{x}, and then prints the
16978 value of the assignment expression (which is 4).
16979 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16980 information on operators in supported languages.
16982 @kindex set variable
16983 @cindex variables, setting
16984 If you are not interested in seeing the value of the assignment, use the
16985 @code{set} command instead of the @code{print} command. @code{set} is
16986 really the same as @code{print} except that the expression's value is
16987 not printed and is not put in the value history (@pxref{Value History,
16988 ,Value History}). The expression is evaluated only for its effects.
16990 If the beginning of the argument string of the @code{set} command
16991 appears identical to a @code{set} subcommand, use the @code{set
16992 variable} command instead of just @code{set}. This command is identical
16993 to @code{set} except for its lack of subcommands. For example, if your
16994 program has a variable @code{width}, you get an error if you try to set
16995 a new value with just @samp{set width=13}, because @value{GDBN} has the
16996 command @code{set width}:
16999 (@value{GDBP}) whatis width
17001 (@value{GDBP}) p width
17003 (@value{GDBP}) set width=47
17004 Invalid syntax in expression.
17008 The invalid expression, of course, is @samp{=47}. In
17009 order to actually set the program's variable @code{width}, use
17012 (@value{GDBP}) set var width=47
17015 Because the @code{set} command has many subcommands that can conflict
17016 with the names of program variables, it is a good idea to use the
17017 @code{set variable} command instead of just @code{set}. For example, if
17018 your program has a variable @code{g}, you run into problems if you try
17019 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17020 the command @code{set gnutarget}, abbreviated @code{set g}:
17024 (@value{GDBP}) whatis g
17028 (@value{GDBP}) set g=4
17032 The program being debugged has been started already.
17033 Start it from the beginning? (y or n) y
17034 Starting program: /home/smith/cc_progs/a.out
17035 "/home/smith/cc_progs/a.out": can't open to read symbols:
17036 Invalid bfd target.
17037 (@value{GDBP}) show g
17038 The current BFD target is "=4".
17043 The program variable @code{g} did not change, and you silently set the
17044 @code{gnutarget} to an invalid value. In order to set the variable
17048 (@value{GDBP}) set var g=4
17051 @value{GDBN} allows more implicit conversions in assignments than C; you can
17052 freely store an integer value into a pointer variable or vice versa,
17053 and you can convert any structure to any other structure that is the
17054 same length or shorter.
17055 @comment FIXME: how do structs align/pad in these conversions?
17056 @comment /doc@cygnus.com 18dec1990
17058 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17059 construct to generate a value of specified type at a specified address
17060 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17061 to memory location @code{0x83040} as an integer (which implies a certain size
17062 and representation in memory), and
17065 set @{int@}0x83040 = 4
17069 stores the value 4 into that memory location.
17072 @section Continuing at a Different Address
17074 Ordinarily, when you continue your program, you do so at the place where
17075 it stopped, with the @code{continue} command. You can instead continue at
17076 an address of your own choosing, with the following commands:
17080 @kindex j @r{(@code{jump})}
17081 @item jump @var{location}
17082 @itemx j @var{location}
17083 Resume execution at @var{location}. Execution stops again immediately
17084 if there is a breakpoint there. @xref{Specify Location}, for a description
17085 of the different forms of @var{location}. It is common
17086 practice to use the @code{tbreak} command in conjunction with
17087 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17089 The @code{jump} command does not change the current stack frame, or
17090 the stack pointer, or the contents of any memory location or any
17091 register other than the program counter. If @var{location} is in
17092 a different function from the one currently executing, the results may
17093 be bizarre if the two functions expect different patterns of arguments or
17094 of local variables. For this reason, the @code{jump} command requests
17095 confirmation if the specified line is not in the function currently
17096 executing. However, even bizarre results are predictable if you are
17097 well acquainted with the machine-language code of your program.
17100 On many systems, you can get much the same effect as the @code{jump}
17101 command by storing a new value into the register @code{$pc}. The
17102 difference is that this does not start your program running; it only
17103 changes the address of where it @emph{will} run when you continue. For
17111 makes the next @code{continue} command or stepping command execute at
17112 address @code{0x485}, rather than at the address where your program stopped.
17113 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17115 The most common occasion to use the @code{jump} command is to back
17116 up---perhaps with more breakpoints set---over a portion of a program
17117 that has already executed, in order to examine its execution in more
17122 @section Giving your Program a Signal
17123 @cindex deliver a signal to a program
17127 @item signal @var{signal}
17128 Resume execution where your program is stopped, but immediately give it the
17129 signal @var{signal}. The @var{signal} can be the name or the number of a
17130 signal. For example, on many systems @code{signal 2} and @code{signal
17131 SIGINT} are both ways of sending an interrupt signal.
17133 Alternatively, if @var{signal} is zero, continue execution without
17134 giving a signal. This is useful when your program stopped on account of
17135 a signal and would ordinarily see the signal when resumed with the
17136 @code{continue} command; @samp{signal 0} causes it to resume without a
17139 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17140 delivered to the currently selected thread, not the thread that last
17141 reported a stop. This includes the situation where a thread was
17142 stopped due to a signal. So if you want to continue execution
17143 suppressing the signal that stopped a thread, you should select that
17144 same thread before issuing the @samp{signal 0} command. If you issue
17145 the @samp{signal 0} command with another thread as the selected one,
17146 @value{GDBN} detects that and asks for confirmation.
17148 Invoking the @code{signal} command is not the same as invoking the
17149 @code{kill} utility from the shell. Sending a signal with @code{kill}
17150 causes @value{GDBN} to decide what to do with the signal depending on
17151 the signal handling tables (@pxref{Signals}). The @code{signal} command
17152 passes the signal directly to your program.
17154 @code{signal} does not repeat when you press @key{RET} a second time
17155 after executing the command.
17157 @kindex queue-signal
17158 @item queue-signal @var{signal}
17159 Queue @var{signal} to be delivered immediately to the current thread
17160 when execution of the thread resumes. The @var{signal} can be the name or
17161 the number of a signal. For example, on many systems @code{signal 2} and
17162 @code{signal SIGINT} are both ways of sending an interrupt signal.
17163 The handling of the signal must be set to pass the signal to the program,
17164 otherwise @value{GDBN} will report an error.
17165 You can control the handling of signals from @value{GDBN} with the
17166 @code{handle} command (@pxref{Signals}).
17168 Alternatively, if @var{signal} is zero, any currently queued signal
17169 for the current thread is discarded and when execution resumes no signal
17170 will be delivered. This is useful when your program stopped on account
17171 of a signal and would ordinarily see the signal when resumed with the
17172 @code{continue} command.
17174 This command differs from the @code{signal} command in that the signal
17175 is just queued, execution is not resumed. And @code{queue-signal} cannot
17176 be used to pass a signal whose handling state has been set to @code{nopass}
17181 @xref{stepping into signal handlers}, for information on how stepping
17182 commands behave when the thread has a signal queued.
17185 @section Returning from a Function
17188 @cindex returning from a function
17191 @itemx return @var{expression}
17192 You can cancel execution of a function call with the @code{return}
17193 command. If you give an
17194 @var{expression} argument, its value is used as the function's return
17198 When you use @code{return}, @value{GDBN} discards the selected stack frame
17199 (and all frames within it). You can think of this as making the
17200 discarded frame return prematurely. If you wish to specify a value to
17201 be returned, give that value as the argument to @code{return}.
17203 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17204 Frame}), and any other frames inside of it, leaving its caller as the
17205 innermost remaining frame. That frame becomes selected. The
17206 specified value is stored in the registers used for returning values
17209 The @code{return} command does not resume execution; it leaves the
17210 program stopped in the state that would exist if the function had just
17211 returned. In contrast, the @code{finish} command (@pxref{Continuing
17212 and Stepping, ,Continuing and Stepping}) resumes execution until the
17213 selected stack frame returns naturally.
17215 @value{GDBN} needs to know how the @var{expression} argument should be set for
17216 the inferior. The concrete registers assignment depends on the OS ABI and the
17217 type being returned by the selected stack frame. For example it is common for
17218 OS ABI to return floating point values in FPU registers while integer values in
17219 CPU registers. Still some ABIs return even floating point values in CPU
17220 registers. Larger integer widths (such as @code{long long int}) also have
17221 specific placement rules. @value{GDBN} already knows the OS ABI from its
17222 current target so it needs to find out also the type being returned to make the
17223 assignment into the right register(s).
17225 Normally, the selected stack frame has debug info. @value{GDBN} will always
17226 use the debug info instead of the implicit type of @var{expression} when the
17227 debug info is available. For example, if you type @kbd{return -1}, and the
17228 function in the current stack frame is declared to return a @code{long long
17229 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17230 into a @code{long long int}:
17233 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17235 (@value{GDBP}) return -1
17236 Make func return now? (y or n) y
17237 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17238 43 printf ("result=%lld\n", func ());
17242 However, if the selected stack frame does not have a debug info, e.g., if the
17243 function was compiled without debug info, @value{GDBN} has to find out the type
17244 to return from user. Specifying a different type by mistake may set the value
17245 in different inferior registers than the caller code expects. For example,
17246 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17247 of a @code{long long int} result for a debug info less function (on 32-bit
17248 architectures). Therefore the user is required to specify the return type by
17249 an appropriate cast explicitly:
17252 Breakpoint 2, 0x0040050b in func ()
17253 (@value{GDBP}) return -1
17254 Return value type not available for selected stack frame.
17255 Please use an explicit cast of the value to return.
17256 (@value{GDBP}) return (long long int) -1
17257 Make selected stack frame return now? (y or n) y
17258 #0 0x00400526 in main ()
17263 @section Calling Program Functions
17266 @cindex calling functions
17267 @cindex inferior functions, calling
17268 @item print @var{expr}
17269 Evaluate the expression @var{expr} and display the resulting value.
17270 The expression may include calls to functions in the program being
17274 @item call @var{expr}
17275 Evaluate the expression @var{expr} without displaying @code{void}
17278 You can use this variant of the @code{print} command if you want to
17279 execute a function from your program that does not return anything
17280 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17281 with @code{void} returned values that @value{GDBN} will otherwise
17282 print. If the result is not void, it is printed and saved in the
17286 It is possible for the function you call via the @code{print} or
17287 @code{call} command to generate a signal (e.g., if there's a bug in
17288 the function, or if you passed it incorrect arguments). What happens
17289 in that case is controlled by the @code{set unwindonsignal} command.
17291 Similarly, with a C@t{++} program it is possible for the function you
17292 call via the @code{print} or @code{call} command to generate an
17293 exception that is not handled due to the constraints of the dummy
17294 frame. In this case, any exception that is raised in the frame, but has
17295 an out-of-frame exception handler will not be found. GDB builds a
17296 dummy-frame for the inferior function call, and the unwinder cannot
17297 seek for exception handlers outside of this dummy-frame. What happens
17298 in that case is controlled by the
17299 @code{set unwind-on-terminating-exception} command.
17302 @item set unwindonsignal
17303 @kindex set unwindonsignal
17304 @cindex unwind stack in called functions
17305 @cindex call dummy stack unwinding
17306 Set unwinding of the stack if a signal is received while in a function
17307 that @value{GDBN} called in the program being debugged. If set to on,
17308 @value{GDBN} unwinds the stack it created for the call and restores
17309 the context to what it was before the call. If set to off (the
17310 default), @value{GDBN} stops in the frame where the signal was
17313 @item show unwindonsignal
17314 @kindex show unwindonsignal
17315 Show the current setting of stack unwinding in the functions called by
17318 @item set unwind-on-terminating-exception
17319 @kindex set unwind-on-terminating-exception
17320 @cindex unwind stack in called functions with unhandled exceptions
17321 @cindex call dummy stack unwinding on unhandled exception.
17322 Set unwinding of the stack if a C@t{++} exception is raised, but left
17323 unhandled while in a function that @value{GDBN} called in the program being
17324 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17325 it created for the call and restores the context to what it was before
17326 the call. If set to off, @value{GDBN} the exception is delivered to
17327 the default C@t{++} exception handler and the inferior terminated.
17329 @item show unwind-on-terminating-exception
17330 @kindex show unwind-on-terminating-exception
17331 Show the current setting of stack unwinding in the functions called by
17336 @cindex weak alias functions
17337 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17338 for another function. In such case, @value{GDBN} might not pick up
17339 the type information, including the types of the function arguments,
17340 which causes @value{GDBN} to call the inferior function incorrectly.
17341 As a result, the called function will function erroneously and may
17342 even crash. A solution to that is to use the name of the aliased
17346 @section Patching Programs
17348 @cindex patching binaries
17349 @cindex writing into executables
17350 @cindex writing into corefiles
17352 By default, @value{GDBN} opens the file containing your program's
17353 executable code (or the corefile) read-only. This prevents accidental
17354 alterations to machine code; but it also prevents you from intentionally
17355 patching your program's binary.
17357 If you'd like to be able to patch the binary, you can specify that
17358 explicitly with the @code{set write} command. For example, you might
17359 want to turn on internal debugging flags, or even to make emergency
17365 @itemx set write off
17366 If you specify @samp{set write on}, @value{GDBN} opens executable and
17367 core files for both reading and writing; if you specify @kbd{set write
17368 off} (the default), @value{GDBN} opens them read-only.
17370 If you have already loaded a file, you must load it again (using the
17371 @code{exec-file} or @code{core-file} command) after changing @code{set
17372 write}, for your new setting to take effect.
17376 Display whether executable files and core files are opened for writing
17377 as well as reading.
17380 @node Compiling and Injecting Code
17381 @section Compiling and injecting code in @value{GDBN}
17382 @cindex injecting code
17383 @cindex writing into executables
17384 @cindex compiling code
17386 @value{GDBN} supports on-demand compilation and code injection into
17387 programs running under @value{GDBN}. GCC 5.0 or higher built with
17388 @file{libcc1.so} must be installed for this functionality to be enabled.
17389 This functionality is implemented with the following commands.
17392 @kindex compile code
17393 @item compile code @var{source-code}
17394 @itemx compile code -raw @var{--} @var{source-code}
17395 Compile @var{source-code} with the compiler language found as the current
17396 language in @value{GDBN} (@pxref{Languages}). If compilation and
17397 injection is not supported with the current language specified in
17398 @value{GDBN}, or the compiler does not support this feature, an error
17399 message will be printed. If @var{source-code} compiles and links
17400 successfully, @value{GDBN} will load the object-code emitted,
17401 and execute it within the context of the currently selected inferior.
17402 It is important to note that the compiled code is executed immediately.
17403 After execution, the compiled code is removed from @value{GDBN} and any
17404 new types or variables you have defined will be deleted.
17406 The command allows you to specify @var{source-code} in two ways.
17407 The simplest method is to provide a single line of code to the command.
17411 compile code printf ("hello world\n");
17414 If you specify options on the command line as well as source code, they
17415 may conflict. The @samp{--} delimiter can be used to separate options
17416 from actual source code. E.g.:
17419 compile code -r -- printf ("hello world\n");
17422 Alternatively you can enter source code as multiple lines of text. To
17423 enter this mode, invoke the @samp{compile code} command without any text
17424 following the command. This will start the multiple-line editor and
17425 allow you to type as many lines of source code as required. When you
17426 have completed typing, enter @samp{end} on its own line to exit the
17431 >printf ("hello\n");
17432 >printf ("world\n");
17436 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17437 provided @var{source-code} in a callable scope. In this case, you must
17438 specify the entry point of the code by defining a function named
17439 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17440 inferior. Using @samp{-raw} option may be needed for example when
17441 @var{source-code} requires @samp{#include} lines which may conflict with
17442 inferior symbols otherwise.
17444 @kindex compile file
17445 @item compile file @var{filename}
17446 @itemx compile file -raw @var{filename}
17447 Like @code{compile code}, but take the source code from @var{filename}.
17450 compile file /home/user/example.c
17455 @item compile print @var{expr}
17456 @itemx compile print /@var{f} @var{expr}
17457 Compile and execute @var{expr} with the compiler language found as the
17458 current language in @value{GDBN} (@pxref{Languages}). By default the
17459 value of @var{expr} is printed in a format appropriate to its data type;
17460 you can choose a different format by specifying @samp{/@var{f}}, where
17461 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17464 @item compile print
17465 @itemx compile print /@var{f}
17466 @cindex reprint the last value
17467 Alternatively you can enter the expression (source code producing it) as
17468 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17469 command without any text following the command. This will start the
17470 multiple-line editor.
17474 The process of compiling and injecting the code can be inspected using:
17477 @anchor{set debug compile}
17478 @item set debug compile
17479 @cindex compile command debugging info
17480 Turns on or off display of @value{GDBN} process of compiling and
17481 injecting the code. The default is off.
17483 @item show debug compile
17484 Displays the current state of displaying @value{GDBN} process of
17485 compiling and injecting the code.
17488 @subsection Compilation options for the @code{compile} command
17490 @value{GDBN} needs to specify the right compilation options for the code
17491 to be injected, in part to make its ABI compatible with the inferior
17492 and in part to make the injected code compatible with @value{GDBN}'s
17496 The options used, in increasing precedence:
17499 @item target architecture and OS options (@code{gdbarch})
17500 These options depend on target processor type and target operating
17501 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17502 (@code{-m64}) compilation option.
17504 @item compilation options recorded in the target
17505 @value{NGCC} (since version 4.7) stores the options used for compilation
17506 into @code{DW_AT_producer} part of DWARF debugging information according
17507 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17508 explicitly specify @code{-g} during inferior compilation otherwise
17509 @value{NGCC} produces no DWARF. This feature is only relevant for
17510 platforms where @code{-g} produces DWARF by default, otherwise one may
17511 try to enforce DWARF by using @code{-gdwarf-4}.
17513 @item compilation options set by @code{set compile-args}
17517 You can override compilation options using the following command:
17520 @item set compile-args
17521 @cindex compile command options override
17522 Set compilation options used for compiling and injecting code with the
17523 @code{compile} commands. These options override any conflicting ones
17524 from the target architecture and/or options stored during inferior
17527 @item show compile-args
17528 Displays the current state of compilation options override.
17529 This does not show all the options actually used during compilation,
17530 use @ref{set debug compile} for that.
17533 @subsection Caveats when using the @code{compile} command
17535 There are a few caveats to keep in mind when using the @code{compile}
17536 command. As the caveats are different per language, the table below
17537 highlights specific issues on a per language basis.
17540 @item C code examples and caveats
17541 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17542 attempt to compile the source code with a @samp{C} compiler. The source
17543 code provided to the @code{compile} command will have much the same
17544 access to variables and types as it normally would if it were part of
17545 the program currently being debugged in @value{GDBN}.
17547 Below is a sample program that forms the basis of the examples that
17548 follow. This program has been compiled and loaded into @value{GDBN},
17549 much like any other normal debugging session.
17552 void function1 (void)
17555 printf ("function 1\n");
17558 void function2 (void)
17573 For the purposes of the examples in this section, the program above has
17574 been compiled, loaded into @value{GDBN}, stopped at the function
17575 @code{main}, and @value{GDBN} is awaiting input from the user.
17577 To access variables and types for any program in @value{GDBN}, the
17578 program must be compiled and packaged with debug information. The
17579 @code{compile} command is not an exception to this rule. Without debug
17580 information, you can still use the @code{compile} command, but you will
17581 be very limited in what variables and types you can access.
17583 So with that in mind, the example above has been compiled with debug
17584 information enabled. The @code{compile} command will have access to
17585 all variables and types (except those that may have been optimized
17586 out). Currently, as @value{GDBN} has stopped the program in the
17587 @code{main} function, the @code{compile} command would have access to
17588 the variable @code{k}. You could invoke the @code{compile} command
17589 and type some source code to set the value of @code{k}. You can also
17590 read it, or do anything with that variable you would normally do in
17591 @code{C}. Be aware that changes to inferior variables in the
17592 @code{compile} command are persistent. In the following example:
17595 compile code k = 3;
17599 the variable @code{k} is now 3. It will retain that value until
17600 something else in the example program changes it, or another
17601 @code{compile} command changes it.
17603 Normal scope and access rules apply to source code compiled and
17604 injected by the @code{compile} command. In the example, the variables
17605 @code{j} and @code{k} are not accessible yet, because the program is
17606 currently stopped in the @code{main} function, where these variables
17607 are not in scope. Therefore, the following command
17610 compile code j = 3;
17614 will result in a compilation error message.
17616 Once the program is continued, execution will bring these variables in
17617 scope, and they will become accessible; then the code you specify via
17618 the @code{compile} command will be able to access them.
17620 You can create variables and types with the @code{compile} command as
17621 part of your source code. Variables and types that are created as part
17622 of the @code{compile} command are not visible to the rest of the program for
17623 the duration of its run. This example is valid:
17626 compile code int ff = 5; printf ("ff is %d\n", ff);
17629 However, if you were to type the following into @value{GDBN} after that
17630 command has completed:
17633 compile code printf ("ff is %d\n'', ff);
17637 a compiler error would be raised as the variable @code{ff} no longer
17638 exists. Object code generated and injected by the @code{compile}
17639 command is removed when its execution ends. Caution is advised
17640 when assigning to program variables values of variables created by the
17641 code submitted to the @code{compile} command. This example is valid:
17644 compile code int ff = 5; k = ff;
17647 The value of the variable @code{ff} is assigned to @code{k}. The variable
17648 @code{k} does not require the existence of @code{ff} to maintain the value
17649 it has been assigned. However, pointers require particular care in
17650 assignment. If the source code compiled with the @code{compile} command
17651 changed the address of a pointer in the example program, perhaps to a
17652 variable created in the @code{compile} command, that pointer would point
17653 to an invalid location when the command exits. The following example
17654 would likely cause issues with your debugged program:
17657 compile code int ff = 5; p = &ff;
17660 In this example, @code{p} would point to @code{ff} when the
17661 @code{compile} command is executing the source code provided to it.
17662 However, as variables in the (example) program persist with their
17663 assigned values, the variable @code{p} would point to an invalid
17664 location when the command exists. A general rule should be followed
17665 in that you should either assign @code{NULL} to any assigned pointers,
17666 or restore a valid location to the pointer before the command exits.
17668 Similar caution must be exercised with any structs, unions, and typedefs
17669 defined in @code{compile} command. Types defined in the @code{compile}
17670 command will no longer be available in the next @code{compile} command.
17671 Therefore, if you cast a variable to a type defined in the
17672 @code{compile} command, care must be taken to ensure that any future
17673 need to resolve the type can be achieved.
17676 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17677 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17678 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17679 Compilation failed.
17680 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17684 Variables that have been optimized away by the compiler are not
17685 accessible to the code submitted to the @code{compile} command.
17686 Access to those variables will generate a compiler error which @value{GDBN}
17687 will print to the console.
17690 @subsection Compiler search for the @code{compile} command
17692 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
17693 may not be obvious for remote targets of different architecture than where
17694 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
17695 shell that executed @value{GDBN}, not the one set by @value{GDBN}
17696 command @code{set environment}). @xref{Environment}. @code{PATH} on
17697 @value{GDBN} host is searched for @value{NGCC} binary matching the
17698 target architecture and operating system.
17700 Specifically @code{PATH} is searched for binaries matching regular expression
17701 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
17702 debugged. @var{arch} is processor name --- multiarch is supported, so for
17703 example both @code{i386} and @code{x86_64} targets look for pattern
17704 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
17705 for pattern @code{s390x?}. @var{os} is currently supported only for
17706 pattern @code{linux(-gnu)?}.
17709 @chapter @value{GDBN} Files
17711 @value{GDBN} needs to know the file name of the program to be debugged,
17712 both in order to read its symbol table and in order to start your
17713 program. To debug a core dump of a previous run, you must also tell
17714 @value{GDBN} the name of the core dump file.
17717 * Files:: Commands to specify files
17718 * File Caching:: Information about @value{GDBN}'s file caching
17719 * Separate Debug Files:: Debugging information in separate files
17720 * MiniDebugInfo:: Debugging information in a special section
17721 * Index Files:: Index files speed up GDB
17722 * Symbol Errors:: Errors reading symbol files
17723 * Data Files:: GDB data files
17727 @section Commands to Specify Files
17729 @cindex symbol table
17730 @cindex core dump file
17732 You may want to specify executable and core dump file names. The usual
17733 way to do this is at start-up time, using the arguments to
17734 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17735 Out of @value{GDBN}}).
17737 Occasionally it is necessary to change to a different file during a
17738 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17739 specify a file you want to use. Or you are debugging a remote target
17740 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17741 Program}). In these situations the @value{GDBN} commands to specify
17742 new files are useful.
17745 @cindex executable file
17747 @item file @var{filename}
17748 Use @var{filename} as the program to be debugged. It is read for its
17749 symbols and for the contents of pure memory. It is also the program
17750 executed when you use the @code{run} command. If you do not specify a
17751 directory and the file is not found in the @value{GDBN} working directory,
17752 @value{GDBN} uses the environment variable @code{PATH} as a list of
17753 directories to search, just as the shell does when looking for a program
17754 to run. You can change the value of this variable, for both @value{GDBN}
17755 and your program, using the @code{path} command.
17757 @cindex unlinked object files
17758 @cindex patching object files
17759 You can load unlinked object @file{.o} files into @value{GDBN} using
17760 the @code{file} command. You will not be able to ``run'' an object
17761 file, but you can disassemble functions and inspect variables. Also,
17762 if the underlying BFD functionality supports it, you could use
17763 @kbd{gdb -write} to patch object files using this technique. Note
17764 that @value{GDBN} can neither interpret nor modify relocations in this
17765 case, so branches and some initialized variables will appear to go to
17766 the wrong place. But this feature is still handy from time to time.
17769 @code{file} with no argument makes @value{GDBN} discard any information it
17770 has on both executable file and the symbol table.
17773 @item exec-file @r{[} @var{filename} @r{]}
17774 Specify that the program to be run (but not the symbol table) is found
17775 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17776 if necessary to locate your program. Omitting @var{filename} means to
17777 discard information on the executable file.
17779 @kindex symbol-file
17780 @item symbol-file @r{[} @var{filename} @r{]}
17781 Read symbol table information from file @var{filename}. @code{PATH} is
17782 searched when necessary. Use the @code{file} command to get both symbol
17783 table and program to run from the same file.
17785 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17786 program's symbol table.
17788 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17789 some breakpoints and auto-display expressions. This is because they may
17790 contain pointers to the internal data recording symbols and data types,
17791 which are part of the old symbol table data being discarded inside
17794 @code{symbol-file} does not repeat if you press @key{RET} again after
17797 When @value{GDBN} is configured for a particular environment, it
17798 understands debugging information in whatever format is the standard
17799 generated for that environment; you may use either a @sc{gnu} compiler, or
17800 other compilers that adhere to the local conventions.
17801 Best results are usually obtained from @sc{gnu} compilers; for example,
17802 using @code{@value{NGCC}} you can generate debugging information for
17805 For most kinds of object files, with the exception of old SVR3 systems
17806 using COFF, the @code{symbol-file} command does not normally read the
17807 symbol table in full right away. Instead, it scans the symbol table
17808 quickly to find which source files and which symbols are present. The
17809 details are read later, one source file at a time, as they are needed.
17811 The purpose of this two-stage reading strategy is to make @value{GDBN}
17812 start up faster. For the most part, it is invisible except for
17813 occasional pauses while the symbol table details for a particular source
17814 file are being read. (The @code{set verbose} command can turn these
17815 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17816 Warnings and Messages}.)
17818 We have not implemented the two-stage strategy for COFF yet. When the
17819 symbol table is stored in COFF format, @code{symbol-file} reads the
17820 symbol table data in full right away. Note that ``stabs-in-COFF''
17821 still does the two-stage strategy, since the debug info is actually
17825 @cindex reading symbols immediately
17826 @cindex symbols, reading immediately
17827 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17828 @itemx file @r{[} -readnow @r{]} @var{filename}
17829 You can override the @value{GDBN} two-stage strategy for reading symbol
17830 tables by using the @samp{-readnow} option with any of the commands that
17831 load symbol table information, if you want to be sure @value{GDBN} has the
17832 entire symbol table available.
17834 @c FIXME: for now no mention of directories, since this seems to be in
17835 @c flux. 13mar1992 status is that in theory GDB would look either in
17836 @c current dir or in same dir as myprog; but issues like competing
17837 @c GDB's, or clutter in system dirs, mean that in practice right now
17838 @c only current dir is used. FFish says maybe a special GDB hierarchy
17839 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17843 @item core-file @r{[}@var{filename}@r{]}
17845 Specify the whereabouts of a core dump file to be used as the ``contents
17846 of memory''. Traditionally, core files contain only some parts of the
17847 address space of the process that generated them; @value{GDBN} can access the
17848 executable file itself for other parts.
17850 @code{core-file} with no argument specifies that no core file is
17853 Note that the core file is ignored when your program is actually running
17854 under @value{GDBN}. So, if you have been running your program and you
17855 wish to debug a core file instead, you must kill the subprocess in which
17856 the program is running. To do this, use the @code{kill} command
17857 (@pxref{Kill Process, ,Killing the Child Process}).
17859 @kindex add-symbol-file
17860 @cindex dynamic linking
17861 @item add-symbol-file @var{filename} @var{address}
17862 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17863 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17864 The @code{add-symbol-file} command reads additional symbol table
17865 information from the file @var{filename}. You would use this command
17866 when @var{filename} has been dynamically loaded (by some other means)
17867 into the program that is running. The @var{address} should give the memory
17868 address at which the file has been loaded; @value{GDBN} cannot figure
17869 this out for itself. You can additionally specify an arbitrary number
17870 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17871 section name and base address for that section. You can specify any
17872 @var{address} as an expression.
17874 The symbol table of the file @var{filename} is added to the symbol table
17875 originally read with the @code{symbol-file} command. You can use the
17876 @code{add-symbol-file} command any number of times; the new symbol data
17877 thus read is kept in addition to the old.
17879 Changes can be reverted using the command @code{remove-symbol-file}.
17881 @cindex relocatable object files, reading symbols from
17882 @cindex object files, relocatable, reading symbols from
17883 @cindex reading symbols from relocatable object files
17884 @cindex symbols, reading from relocatable object files
17885 @cindex @file{.o} files, reading symbols from
17886 Although @var{filename} is typically a shared library file, an
17887 executable file, or some other object file which has been fully
17888 relocated for loading into a process, you can also load symbolic
17889 information from relocatable @file{.o} files, as long as:
17893 the file's symbolic information refers only to linker symbols defined in
17894 that file, not to symbols defined by other object files,
17896 every section the file's symbolic information refers to has actually
17897 been loaded into the inferior, as it appears in the file, and
17899 you can determine the address at which every section was loaded, and
17900 provide these to the @code{add-symbol-file} command.
17904 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17905 relocatable files into an already running program; such systems
17906 typically make the requirements above easy to meet. However, it's
17907 important to recognize that many native systems use complex link
17908 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17909 assembly, for example) that make the requirements difficult to meet. In
17910 general, one cannot assume that using @code{add-symbol-file} to read a
17911 relocatable object file's symbolic information will have the same effect
17912 as linking the relocatable object file into the program in the normal
17915 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17917 @kindex remove-symbol-file
17918 @item remove-symbol-file @var{filename}
17919 @item remove-symbol-file -a @var{address}
17920 Remove a symbol file added via the @code{add-symbol-file} command. The
17921 file to remove can be identified by its @var{filename} or by an @var{address}
17922 that lies within the boundaries of this symbol file in memory. Example:
17925 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17926 add symbol table from file "/home/user/gdb/mylib.so" at
17927 .text_addr = 0x7ffff7ff9480
17929 Reading symbols from /home/user/gdb/mylib.so...done.
17930 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17931 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17936 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17938 @kindex add-symbol-file-from-memory
17939 @cindex @code{syscall DSO}
17940 @cindex load symbols from memory
17941 @item add-symbol-file-from-memory @var{address}
17942 Load symbols from the given @var{address} in a dynamically loaded
17943 object file whose image is mapped directly into the inferior's memory.
17944 For example, the Linux kernel maps a @code{syscall DSO} into each
17945 process's address space; this DSO provides kernel-specific code for
17946 some system calls. The argument can be any expression whose
17947 evaluation yields the address of the file's shared object file header.
17948 For this command to work, you must have used @code{symbol-file} or
17949 @code{exec-file} commands in advance.
17952 @item section @var{section} @var{addr}
17953 The @code{section} command changes the base address of the named
17954 @var{section} of the exec file to @var{addr}. This can be used if the
17955 exec file does not contain section addresses, (such as in the
17956 @code{a.out} format), or when the addresses specified in the file
17957 itself are wrong. Each section must be changed separately. The
17958 @code{info files} command, described below, lists all the sections and
17962 @kindex info target
17965 @code{info files} and @code{info target} are synonymous; both print the
17966 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17967 including the names of the executable and core dump files currently in
17968 use by @value{GDBN}, and the files from which symbols were loaded. The
17969 command @code{help target} lists all possible targets rather than
17972 @kindex maint info sections
17973 @item maint info sections
17974 Another command that can give you extra information about program sections
17975 is @code{maint info sections}. In addition to the section information
17976 displayed by @code{info files}, this command displays the flags and file
17977 offset of each section in the executable and core dump files. In addition,
17978 @code{maint info sections} provides the following command options (which
17979 may be arbitrarily combined):
17983 Display sections for all loaded object files, including shared libraries.
17984 @item @var{sections}
17985 Display info only for named @var{sections}.
17986 @item @var{section-flags}
17987 Display info only for sections for which @var{section-flags} are true.
17988 The section flags that @value{GDBN} currently knows about are:
17991 Section will have space allocated in the process when loaded.
17992 Set for all sections except those containing debug information.
17994 Section will be loaded from the file into the child process memory.
17995 Set for pre-initialized code and data, clear for @code{.bss} sections.
17997 Section needs to be relocated before loading.
17999 Section cannot be modified by the child process.
18001 Section contains executable code only.
18003 Section contains data only (no executable code).
18005 Section will reside in ROM.
18007 Section contains data for constructor/destructor lists.
18009 Section is not empty.
18011 An instruction to the linker to not output the section.
18012 @item COFF_SHARED_LIBRARY
18013 A notification to the linker that the section contains
18014 COFF shared library information.
18016 Section contains common symbols.
18019 @kindex set trust-readonly-sections
18020 @cindex read-only sections
18021 @item set trust-readonly-sections on
18022 Tell @value{GDBN} that readonly sections in your object file
18023 really are read-only (i.e.@: that their contents will not change).
18024 In that case, @value{GDBN} can fetch values from these sections
18025 out of the object file, rather than from the target program.
18026 For some targets (notably embedded ones), this can be a significant
18027 enhancement to debugging performance.
18029 The default is off.
18031 @item set trust-readonly-sections off
18032 Tell @value{GDBN} not to trust readonly sections. This means that
18033 the contents of the section might change while the program is running,
18034 and must therefore be fetched from the target when needed.
18036 @item show trust-readonly-sections
18037 Show the current setting of trusting readonly sections.
18040 All file-specifying commands allow both absolute and relative file names
18041 as arguments. @value{GDBN} always converts the file name to an absolute file
18042 name and remembers it that way.
18044 @cindex shared libraries
18045 @anchor{Shared Libraries}
18046 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18047 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18048 DSBT (TIC6X) shared libraries.
18050 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18051 shared libraries. @xref{Expat}.
18053 @value{GDBN} automatically loads symbol definitions from shared libraries
18054 when you use the @code{run} command, or when you examine a core file.
18055 (Before you issue the @code{run} command, @value{GDBN} does not understand
18056 references to a function in a shared library, however---unless you are
18057 debugging a core file).
18059 @c FIXME: some @value{GDBN} release may permit some refs to undef
18060 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18061 @c FIXME...lib; check this from time to time when updating manual
18063 There are times, however, when you may wish to not automatically load
18064 symbol definitions from shared libraries, such as when they are
18065 particularly large or there are many of them.
18067 To control the automatic loading of shared library symbols, use the
18071 @kindex set auto-solib-add
18072 @item set auto-solib-add @var{mode}
18073 If @var{mode} is @code{on}, symbols from all shared object libraries
18074 will be loaded automatically when the inferior begins execution, you
18075 attach to an independently started inferior, or when the dynamic linker
18076 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18077 is @code{off}, symbols must be loaded manually, using the
18078 @code{sharedlibrary} command. The default value is @code{on}.
18080 @cindex memory used for symbol tables
18081 If your program uses lots of shared libraries with debug info that
18082 takes large amounts of memory, you can decrease the @value{GDBN}
18083 memory footprint by preventing it from automatically loading the
18084 symbols from shared libraries. To that end, type @kbd{set
18085 auto-solib-add off} before running the inferior, then load each
18086 library whose debug symbols you do need with @kbd{sharedlibrary
18087 @var{regexp}}, where @var{regexp} is a regular expression that matches
18088 the libraries whose symbols you want to be loaded.
18090 @kindex show auto-solib-add
18091 @item show auto-solib-add
18092 Display the current autoloading mode.
18095 @cindex load shared library
18096 To explicitly load shared library symbols, use the @code{sharedlibrary}
18100 @kindex info sharedlibrary
18102 @item info share @var{regex}
18103 @itemx info sharedlibrary @var{regex}
18104 Print the names of the shared libraries which are currently loaded
18105 that match @var{regex}. If @var{regex} is omitted then print
18106 all shared libraries that are loaded.
18109 @item info dll @var{regex}
18110 This is an alias of @code{info sharedlibrary}.
18112 @kindex sharedlibrary
18114 @item sharedlibrary @var{regex}
18115 @itemx share @var{regex}
18116 Load shared object library symbols for files matching a
18117 Unix regular expression.
18118 As with files loaded automatically, it only loads shared libraries
18119 required by your program for a core file or after typing @code{run}. If
18120 @var{regex} is omitted all shared libraries required by your program are
18123 @item nosharedlibrary
18124 @kindex nosharedlibrary
18125 @cindex unload symbols from shared libraries
18126 Unload all shared object library symbols. This discards all symbols
18127 that have been loaded from all shared libraries. Symbols from shared
18128 libraries that were loaded by explicit user requests are not
18132 Sometimes you may wish that @value{GDBN} stops and gives you control
18133 when any of shared library events happen. The best way to do this is
18134 to use @code{catch load} and @code{catch unload} (@pxref{Set
18137 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18138 command for this. This command exists for historical reasons. It is
18139 less useful than setting a catchpoint, because it does not allow for
18140 conditions or commands as a catchpoint does.
18143 @item set stop-on-solib-events
18144 @kindex set stop-on-solib-events
18145 This command controls whether @value{GDBN} should give you control
18146 when the dynamic linker notifies it about some shared library event.
18147 The most common event of interest is loading or unloading of a new
18150 @item show stop-on-solib-events
18151 @kindex show stop-on-solib-events
18152 Show whether @value{GDBN} stops and gives you control when shared
18153 library events happen.
18156 Shared libraries are also supported in many cross or remote debugging
18157 configurations. @value{GDBN} needs to have access to the target's libraries;
18158 this can be accomplished either by providing copies of the libraries
18159 on the host system, or by asking @value{GDBN} to automatically retrieve the
18160 libraries from the target. If copies of the target libraries are
18161 provided, they need to be the same as the target libraries, although the
18162 copies on the target can be stripped as long as the copies on the host are
18165 @cindex where to look for shared libraries
18166 For remote debugging, you need to tell @value{GDBN} where the target
18167 libraries are, so that it can load the correct copies---otherwise, it
18168 may try to load the host's libraries. @value{GDBN} has two variables
18169 to specify the search directories for target libraries.
18172 @cindex prefix for executable and shared library file names
18173 @cindex system root, alternate
18174 @kindex set solib-absolute-prefix
18175 @kindex set sysroot
18176 @item set sysroot @var{path}
18177 Use @var{path} as the system root for the program being debugged. Any
18178 absolute shared library paths will be prefixed with @var{path}; many
18179 runtime loaders store the absolute paths to the shared library in the
18180 target program's memory. When starting processes remotely, and when
18181 attaching to already-running processes (local or remote), their
18182 executable filenames will be prefixed with @var{path} if reported to
18183 @value{GDBN} as absolute by the operating system. If you use
18184 @code{set sysroot} to find executables and shared libraries, they need
18185 to be laid out in the same way that they are on the target, with
18186 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18189 If @var{path} starts with the sequence @file{target:} and the target
18190 system is remote then @value{GDBN} will retrieve the target binaries
18191 from the remote system. This is only supported when using a remote
18192 target that supports the @code{remote get} command (@pxref{File
18193 Transfer,,Sending files to a remote system}). The part of @var{path}
18194 following the initial @file{target:} (if present) is used as system
18195 root prefix on the remote file system. If @var{path} starts with the
18196 sequence @file{remote:} this is converted to the sequence
18197 @file{target:} by @code{set sysroot}@footnote{Historically the
18198 functionality to retrieve binaries from the remote system was
18199 provided by prefixing @var{path} with @file{remote:}}. If you want
18200 to specify a local system root using a directory that happens to be
18201 named @file{target:} or @file{remote:}, you need to use some
18202 equivalent variant of the name like @file{./target:}.
18204 For targets with an MS-DOS based filesystem, such as MS-Windows and
18205 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18206 absolute file name with @var{path}. But first, on Unix hosts,
18207 @value{GDBN} converts all backslash directory separators into forward
18208 slashes, because the backslash is not a directory separator on Unix:
18211 c:\foo\bar.dll @result{} c:/foo/bar.dll
18214 Then, @value{GDBN} attempts prefixing the target file name with
18215 @var{path}, and looks for the resulting file name in the host file
18219 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18222 If that does not find the binary, @value{GDBN} tries removing
18223 the @samp{:} character from the drive spec, both for convenience, and,
18224 for the case of the host file system not supporting file names with
18228 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18231 This makes it possible to have a system root that mirrors a target
18232 with more than one drive. E.g., you may want to setup your local
18233 copies of the target system shared libraries like so (note @samp{c} vs
18237 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18238 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18239 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18243 and point the system root at @file{/path/to/sysroot}, so that
18244 @value{GDBN} can find the correct copies of both
18245 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18247 If that still does not find the binary, @value{GDBN} tries
18248 removing the whole drive spec from the target file name:
18251 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18254 This last lookup makes it possible to not care about the drive name,
18255 if you don't want or need to.
18257 The @code{set solib-absolute-prefix} command is an alias for @code{set
18260 @cindex default system root
18261 @cindex @samp{--with-sysroot}
18262 You can set the default system root by using the configure-time
18263 @samp{--with-sysroot} option. If the system root is inside
18264 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18265 @samp{--exec-prefix}), then the default system root will be updated
18266 automatically if the installed @value{GDBN} is moved to a new
18269 @kindex show sysroot
18271 Display the current executable and shared library prefix.
18273 @kindex set solib-search-path
18274 @item set solib-search-path @var{path}
18275 If this variable is set, @var{path} is a colon-separated list of
18276 directories to search for shared libraries. @samp{solib-search-path}
18277 is used after @samp{sysroot} fails to locate the library, or if the
18278 path to the library is relative instead of absolute. If you want to
18279 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18280 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18281 finding your host's libraries. @samp{sysroot} is preferred; setting
18282 it to a nonexistent directory may interfere with automatic loading
18283 of shared library symbols.
18285 @kindex show solib-search-path
18286 @item show solib-search-path
18287 Display the current shared library search path.
18289 @cindex DOS file-name semantics of file names.
18290 @kindex set target-file-system-kind (unix|dos-based|auto)
18291 @kindex show target-file-system-kind
18292 @item set target-file-system-kind @var{kind}
18293 Set assumed file system kind for target reported file names.
18295 Shared library file names as reported by the target system may not
18296 make sense as is on the system @value{GDBN} is running on. For
18297 example, when remote debugging a target that has MS-DOS based file
18298 system semantics, from a Unix host, the target may be reporting to
18299 @value{GDBN} a list of loaded shared libraries with file names such as
18300 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18301 drive letters, so the @samp{c:\} prefix is not normally understood as
18302 indicating an absolute file name, and neither is the backslash
18303 normally considered a directory separator character. In that case,
18304 the native file system would interpret this whole absolute file name
18305 as a relative file name with no directory components. This would make
18306 it impossible to point @value{GDBN} at a copy of the remote target's
18307 shared libraries on the host using @code{set sysroot}, and impractical
18308 with @code{set solib-search-path}. Setting
18309 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18310 to interpret such file names similarly to how the target would, and to
18311 map them to file names valid on @value{GDBN}'s native file system
18312 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18313 to one of the supported file system kinds. In that case, @value{GDBN}
18314 tries to determine the appropriate file system variant based on the
18315 current target's operating system (@pxref{ABI, ,Configuring the
18316 Current ABI}). The supported file system settings are:
18320 Instruct @value{GDBN} to assume the target file system is of Unix
18321 kind. Only file names starting the forward slash (@samp{/}) character
18322 are considered absolute, and the directory separator character is also
18326 Instruct @value{GDBN} to assume the target file system is DOS based.
18327 File names starting with either a forward slash, or a drive letter
18328 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18329 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18330 considered directory separators.
18333 Instruct @value{GDBN} to use the file system kind associated with the
18334 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18335 This is the default.
18339 @cindex file name canonicalization
18340 @cindex base name differences
18341 When processing file names provided by the user, @value{GDBN}
18342 frequently needs to compare them to the file names recorded in the
18343 program's debug info. Normally, @value{GDBN} compares just the
18344 @dfn{base names} of the files as strings, which is reasonably fast
18345 even for very large programs. (The base name of a file is the last
18346 portion of its name, after stripping all the leading directories.)
18347 This shortcut in comparison is based upon the assumption that files
18348 cannot have more than one base name. This is usually true, but
18349 references to files that use symlinks or similar filesystem
18350 facilities violate that assumption. If your program records files
18351 using such facilities, or if you provide file names to @value{GDBN}
18352 using symlinks etc., you can set @code{basenames-may-differ} to
18353 @code{true} to instruct @value{GDBN} to completely canonicalize each
18354 pair of file names it needs to compare. This will make file-name
18355 comparisons accurate, but at a price of a significant slowdown.
18358 @item set basenames-may-differ
18359 @kindex set basenames-may-differ
18360 Set whether a source file may have multiple base names.
18362 @item show basenames-may-differ
18363 @kindex show basenames-may-differ
18364 Show whether a source file may have multiple base names.
18368 @section File Caching
18369 @cindex caching of opened files
18370 @cindex caching of bfd objects
18372 To speed up file loading, and reduce memory usage, @value{GDBN} will
18373 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18374 BFD, bfd, The Binary File Descriptor Library}. The following commands
18375 allow visibility and control of the caching behavior.
18378 @kindex maint info bfds
18379 @item maint info bfds
18380 This prints information about each @code{bfd} object that is known to
18383 @kindex maint set bfd-sharing
18384 @kindex maint show bfd-sharing
18385 @kindex bfd caching
18386 @item maint set bfd-sharing
18387 @item maint show bfd-sharing
18388 Control whether @code{bfd} objects can be shared. When sharing is
18389 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18390 than reopening the same file. Turning sharing off does not cause
18391 already shared @code{bfd} objects to be unshared, but all future files
18392 that are opened will create a new @code{bfd} object. Similarly,
18393 re-enabling sharing does not cause multiple existing @code{bfd}
18394 objects to be collapsed into a single shared @code{bfd} object.
18396 @kindex set debug bfd-cache @var{level}
18397 @kindex bfd caching
18398 @item set debug bfd-cache @var{level}
18399 Turns on debugging of the bfd cache, setting the level to @var{level}.
18401 @kindex show debug bfd-cache
18402 @kindex bfd caching
18403 @item show debug bfd-cache
18404 Show the current debugging level of the bfd cache.
18407 @node Separate Debug Files
18408 @section Debugging Information in Separate Files
18409 @cindex separate debugging information files
18410 @cindex debugging information in separate files
18411 @cindex @file{.debug} subdirectories
18412 @cindex debugging information directory, global
18413 @cindex global debugging information directories
18414 @cindex build ID, and separate debugging files
18415 @cindex @file{.build-id} directory
18417 @value{GDBN} allows you to put a program's debugging information in a
18418 file separate from the executable itself, in a way that allows
18419 @value{GDBN} to find and load the debugging information automatically.
18420 Since debugging information can be very large---sometimes larger
18421 than the executable code itself---some systems distribute debugging
18422 information for their executables in separate files, which users can
18423 install only when they need to debug a problem.
18425 @value{GDBN} supports two ways of specifying the separate debug info
18430 The executable contains a @dfn{debug link} that specifies the name of
18431 the separate debug info file. The separate debug file's name is
18432 usually @file{@var{executable}.debug}, where @var{executable} is the
18433 name of the corresponding executable file without leading directories
18434 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18435 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18436 checksum for the debug file, which @value{GDBN} uses to validate that
18437 the executable and the debug file came from the same build.
18440 The executable contains a @dfn{build ID}, a unique bit string that is
18441 also present in the corresponding debug info file. (This is supported
18442 only on some operating systems, when using the ELF or PE file formats
18443 for binary files and the @sc{gnu} Binutils.) For more details about
18444 this feature, see the description of the @option{--build-id}
18445 command-line option in @ref{Options, , Command Line Options, ld.info,
18446 The GNU Linker}. The debug info file's name is not specified
18447 explicitly by the build ID, but can be computed from the build ID, see
18451 Depending on the way the debug info file is specified, @value{GDBN}
18452 uses two different methods of looking for the debug file:
18456 For the ``debug link'' method, @value{GDBN} looks up the named file in
18457 the directory of the executable file, then in a subdirectory of that
18458 directory named @file{.debug}, and finally under each one of the global debug
18459 directories, in a subdirectory whose name is identical to the leading
18460 directories of the executable's absolute file name.
18463 For the ``build ID'' method, @value{GDBN} looks in the
18464 @file{.build-id} subdirectory of each one of the global debug directories for
18465 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18466 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18467 are the rest of the bit string. (Real build ID strings are 32 or more
18468 hex characters, not 10.)
18471 So, for example, suppose you ask @value{GDBN} to debug
18472 @file{/usr/bin/ls}, which has a debug link that specifies the
18473 file @file{ls.debug}, and a build ID whose value in hex is
18474 @code{abcdef1234}. If the list of the global debug directories includes
18475 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18476 debug information files, in the indicated order:
18480 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18482 @file{/usr/bin/ls.debug}
18484 @file{/usr/bin/.debug/ls.debug}
18486 @file{/usr/lib/debug/usr/bin/ls.debug}.
18489 @anchor{debug-file-directory}
18490 Global debugging info directories default to what is set by @value{GDBN}
18491 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18492 you can also set the global debugging info directories, and view the list
18493 @value{GDBN} is currently using.
18497 @kindex set debug-file-directory
18498 @item set debug-file-directory @var{directories}
18499 Set the directories which @value{GDBN} searches for separate debugging
18500 information files to @var{directory}. Multiple path components can be set
18501 concatenating them by a path separator.
18503 @kindex show debug-file-directory
18504 @item show debug-file-directory
18505 Show the directories @value{GDBN} searches for separate debugging
18510 @cindex @code{.gnu_debuglink} sections
18511 @cindex debug link sections
18512 A debug link is a special section of the executable file named
18513 @code{.gnu_debuglink}. The section must contain:
18517 A filename, with any leading directory components removed, followed by
18520 zero to three bytes of padding, as needed to reach the next four-byte
18521 boundary within the section, and
18523 a four-byte CRC checksum, stored in the same endianness used for the
18524 executable file itself. The checksum is computed on the debugging
18525 information file's full contents by the function given below, passing
18526 zero as the @var{crc} argument.
18529 Any executable file format can carry a debug link, as long as it can
18530 contain a section named @code{.gnu_debuglink} with the contents
18533 @cindex @code{.note.gnu.build-id} sections
18534 @cindex build ID sections
18535 The build ID is a special section in the executable file (and in other
18536 ELF binary files that @value{GDBN} may consider). This section is
18537 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18538 It contains unique identification for the built files---the ID remains
18539 the same across multiple builds of the same build tree. The default
18540 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18541 content for the build ID string. The same section with an identical
18542 value is present in the original built binary with symbols, in its
18543 stripped variant, and in the separate debugging information file.
18545 The debugging information file itself should be an ordinary
18546 executable, containing a full set of linker symbols, sections, and
18547 debugging information. The sections of the debugging information file
18548 should have the same names, addresses, and sizes as the original file,
18549 but they need not contain any data---much like a @code{.bss} section
18550 in an ordinary executable.
18552 The @sc{gnu} binary utilities (Binutils) package includes the
18553 @samp{objcopy} utility that can produce
18554 the separated executable / debugging information file pairs using the
18555 following commands:
18558 @kbd{objcopy --only-keep-debug foo foo.debug}
18563 These commands remove the debugging
18564 information from the executable file @file{foo} and place it in the file
18565 @file{foo.debug}. You can use the first, second or both methods to link the
18570 The debug link method needs the following additional command to also leave
18571 behind a debug link in @file{foo}:
18574 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18577 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18578 a version of the @code{strip} command such that the command @kbd{strip foo -f
18579 foo.debug} has the same functionality as the two @code{objcopy} commands and
18580 the @code{ln -s} command above, together.
18583 Build ID gets embedded into the main executable using @code{ld --build-id} or
18584 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18585 compatibility fixes for debug files separation are present in @sc{gnu} binary
18586 utilities (Binutils) package since version 2.18.
18591 @cindex CRC algorithm definition
18592 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18593 IEEE 802.3 using the polynomial:
18595 @c TexInfo requires naked braces for multi-digit exponents for Tex
18596 @c output, but this causes HTML output to barf. HTML has to be set using
18597 @c raw commands. So we end up having to specify this equation in 2
18602 <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>
18603 + <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
18609 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18610 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18614 The function is computed byte at a time, taking the least
18615 significant bit of each byte first. The initial pattern
18616 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18617 the final result is inverted to ensure trailing zeros also affect the
18620 @emph{Note:} This is the same CRC polynomial as used in handling the
18621 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18622 However in the case of the Remote Serial Protocol, the CRC is computed
18623 @emph{most} significant bit first, and the result is not inverted, so
18624 trailing zeros have no effect on the CRC value.
18626 To complete the description, we show below the code of the function
18627 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18628 initially supplied @code{crc} argument means that an initial call to
18629 this function passing in zero will start computing the CRC using
18632 @kindex gnu_debuglink_crc32
18635 gnu_debuglink_crc32 (unsigned long crc,
18636 unsigned char *buf, size_t len)
18638 static const unsigned long crc32_table[256] =
18640 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18641 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18642 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18643 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18644 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18645 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18646 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18647 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18648 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18649 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18650 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18651 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18652 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18653 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18654 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18655 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18656 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18657 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18658 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18659 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18660 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18661 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18662 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18663 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18664 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18665 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18666 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18667 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18668 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18669 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18670 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18671 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18672 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18673 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18674 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18675 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18676 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18677 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18678 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18679 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18680 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18681 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18682 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18683 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18684 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18685 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18686 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18687 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18688 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18689 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18690 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18693 unsigned char *end;
18695 crc = ~crc & 0xffffffff;
18696 for (end = buf + len; buf < end; ++buf)
18697 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18698 return ~crc & 0xffffffff;
18703 This computation does not apply to the ``build ID'' method.
18705 @node MiniDebugInfo
18706 @section Debugging information in a special section
18707 @cindex separate debug sections
18708 @cindex @samp{.gnu_debugdata} section
18710 Some systems ship pre-built executables and libraries that have a
18711 special @samp{.gnu_debugdata} section. This feature is called
18712 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18713 is used to supply extra symbols for backtraces.
18715 The intent of this section is to provide extra minimal debugging
18716 information for use in simple backtraces. It is not intended to be a
18717 replacement for full separate debugging information (@pxref{Separate
18718 Debug Files}). The example below shows the intended use; however,
18719 @value{GDBN} does not currently put restrictions on what sort of
18720 debugging information might be included in the section.
18722 @value{GDBN} has support for this extension. If the section exists,
18723 then it is used provided that no other source of debugging information
18724 can be found, and that @value{GDBN} was configured with LZMA support.
18726 This section can be easily created using @command{objcopy} and other
18727 standard utilities:
18730 # Extract the dynamic symbols from the main binary, there is no need
18731 # to also have these in the normal symbol table.
18732 nm -D @var{binary} --format=posix --defined-only \
18733 | awk '@{ print $1 @}' | sort > dynsyms
18735 # Extract all the text (i.e. function) symbols from the debuginfo.
18736 # (Note that we actually also accept "D" symbols, for the benefit
18737 # of platforms like PowerPC64 that use function descriptors.)
18738 nm @var{binary} --format=posix --defined-only \
18739 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18742 # Keep all the function symbols not already in the dynamic symbol
18744 comm -13 dynsyms funcsyms > keep_symbols
18746 # Separate full debug info into debug binary.
18747 objcopy --only-keep-debug @var{binary} debug
18749 # Copy the full debuginfo, keeping only a minimal set of symbols and
18750 # removing some unnecessary sections.
18751 objcopy -S --remove-section .gdb_index --remove-section .comment \
18752 --keep-symbols=keep_symbols debug mini_debuginfo
18754 # Drop the full debug info from the original binary.
18755 strip --strip-all -R .comment @var{binary}
18757 # Inject the compressed data into the .gnu_debugdata section of the
18760 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18764 @section Index Files Speed Up @value{GDBN}
18765 @cindex index files
18766 @cindex @samp{.gdb_index} section
18768 When @value{GDBN} finds a symbol file, it scans the symbols in the
18769 file in order to construct an internal symbol table. This lets most
18770 @value{GDBN} operations work quickly---at the cost of a delay early
18771 on. For large programs, this delay can be quite lengthy, so
18772 @value{GDBN} provides a way to build an index, which speeds up
18775 The index is stored as a section in the symbol file. @value{GDBN} can
18776 write the index to a file, then you can put it into the symbol file
18777 using @command{objcopy}.
18779 To create an index file, use the @code{save gdb-index} command:
18782 @item save gdb-index @var{directory}
18783 @kindex save gdb-index
18784 Create an index file for each symbol file currently known by
18785 @value{GDBN}. Each file is named after its corresponding symbol file,
18786 with @samp{.gdb-index} appended, and is written into the given
18790 Once you have created an index file you can merge it into your symbol
18791 file, here named @file{symfile}, using @command{objcopy}:
18794 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18795 --set-section-flags .gdb_index=readonly symfile symfile
18798 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18799 sections that have been deprecated. Usually they are deprecated because
18800 they are missing a new feature or have performance issues.
18801 To tell @value{GDBN} to use a deprecated index section anyway
18802 specify @code{set use-deprecated-index-sections on}.
18803 The default is @code{off}.
18804 This can speed up startup, but may result in some functionality being lost.
18805 @xref{Index Section Format}.
18807 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18808 must be done before gdb reads the file. The following will not work:
18811 $ gdb -ex "set use-deprecated-index-sections on" <program>
18814 Instead you must do, for example,
18817 $ gdb -iex "set use-deprecated-index-sections on" <program>
18820 There are currently some limitation on indices. They only work when
18821 for DWARF debugging information, not stabs. And, they do not
18822 currently work for programs using Ada.
18824 @node Symbol Errors
18825 @section Errors Reading Symbol Files
18827 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18828 such as symbol types it does not recognize, or known bugs in compiler
18829 output. By default, @value{GDBN} does not notify you of such problems, since
18830 they are relatively common and primarily of interest to people
18831 debugging compilers. If you are interested in seeing information
18832 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18833 only one message about each such type of problem, no matter how many
18834 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18835 to see how many times the problems occur, with the @code{set
18836 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18839 The messages currently printed, and their meanings, include:
18842 @item inner block not inside outer block in @var{symbol}
18844 The symbol information shows where symbol scopes begin and end
18845 (such as at the start of a function or a block of statements). This
18846 error indicates that an inner scope block is not fully contained
18847 in its outer scope blocks.
18849 @value{GDBN} circumvents the problem by treating the inner block as if it had
18850 the same scope as the outer block. In the error message, @var{symbol}
18851 may be shown as ``@code{(don't know)}'' if the outer block is not a
18854 @item block at @var{address} out of order
18856 The symbol information for symbol scope blocks should occur in
18857 order of increasing addresses. This error indicates that it does not
18860 @value{GDBN} does not circumvent this problem, and has trouble
18861 locating symbols in the source file whose symbols it is reading. (You
18862 can often determine what source file is affected by specifying
18863 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18866 @item bad block start address patched
18868 The symbol information for a symbol scope block has a start address
18869 smaller than the address of the preceding source line. This is known
18870 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18872 @value{GDBN} circumvents the problem by treating the symbol scope block as
18873 starting on the previous source line.
18875 @item bad string table offset in symbol @var{n}
18878 Symbol number @var{n} contains a pointer into the string table which is
18879 larger than the size of the string table.
18881 @value{GDBN} circumvents the problem by considering the symbol to have the
18882 name @code{foo}, which may cause other problems if many symbols end up
18885 @item unknown symbol type @code{0x@var{nn}}
18887 The symbol information contains new data types that @value{GDBN} does
18888 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18889 uncomprehended information, in hexadecimal.
18891 @value{GDBN} circumvents the error by ignoring this symbol information.
18892 This usually allows you to debug your program, though certain symbols
18893 are not accessible. If you encounter such a problem and feel like
18894 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18895 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18896 and examine @code{*bufp} to see the symbol.
18898 @item stub type has NULL name
18900 @value{GDBN} could not find the full definition for a struct or class.
18902 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18903 The symbol information for a C@t{++} member function is missing some
18904 information that recent versions of the compiler should have output for
18907 @item info mismatch between compiler and debugger
18909 @value{GDBN} could not parse a type specification output by the compiler.
18914 @section GDB Data Files
18916 @cindex prefix for data files
18917 @value{GDBN} will sometimes read an auxiliary data file. These files
18918 are kept in a directory known as the @dfn{data directory}.
18920 You can set the data directory's name, and view the name @value{GDBN}
18921 is currently using.
18924 @kindex set data-directory
18925 @item set data-directory @var{directory}
18926 Set the directory which @value{GDBN} searches for auxiliary data files
18927 to @var{directory}.
18929 @kindex show data-directory
18930 @item show data-directory
18931 Show the directory @value{GDBN} searches for auxiliary data files.
18934 @cindex default data directory
18935 @cindex @samp{--with-gdb-datadir}
18936 You can set the default data directory by using the configure-time
18937 @samp{--with-gdb-datadir} option. If the data directory is inside
18938 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18939 @samp{--exec-prefix}), then the default data directory will be updated
18940 automatically if the installed @value{GDBN} is moved to a new
18943 The data directory may also be specified with the
18944 @code{--data-directory} command line option.
18945 @xref{Mode Options}.
18948 @chapter Specifying a Debugging Target
18950 @cindex debugging target
18951 A @dfn{target} is the execution environment occupied by your program.
18953 Often, @value{GDBN} runs in the same host environment as your program;
18954 in that case, the debugging target is specified as a side effect when
18955 you use the @code{file} or @code{core} commands. When you need more
18956 flexibility---for example, running @value{GDBN} on a physically separate
18957 host, or controlling a standalone system over a serial port or a
18958 realtime system over a TCP/IP connection---you can use the @code{target}
18959 command to specify one of the target types configured for @value{GDBN}
18960 (@pxref{Target Commands, ,Commands for Managing Targets}).
18962 @cindex target architecture
18963 It is possible to build @value{GDBN} for several different @dfn{target
18964 architectures}. When @value{GDBN} is built like that, you can choose
18965 one of the available architectures with the @kbd{set architecture}
18969 @kindex set architecture
18970 @kindex show architecture
18971 @item set architecture @var{arch}
18972 This command sets the current target architecture to @var{arch}. The
18973 value of @var{arch} can be @code{"auto"}, in addition to one of the
18974 supported architectures.
18976 @item show architecture
18977 Show the current target architecture.
18979 @item set processor
18981 @kindex set processor
18982 @kindex show processor
18983 These are alias commands for, respectively, @code{set architecture}
18984 and @code{show architecture}.
18988 * Active Targets:: Active targets
18989 * Target Commands:: Commands for managing targets
18990 * Byte Order:: Choosing target byte order
18993 @node Active Targets
18994 @section Active Targets
18996 @cindex stacking targets
18997 @cindex active targets
18998 @cindex multiple targets
19000 There are multiple classes of targets such as: processes, executable files or
19001 recording sessions. Core files belong to the process class, making core file
19002 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19003 on multiple active targets, one in each class. This allows you to (for
19004 example) start a process and inspect its activity, while still having access to
19005 the executable file after the process finishes. Or if you start process
19006 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19007 presented a virtual layer of the recording target, while the process target
19008 remains stopped at the chronologically last point of the process execution.
19010 Use the @code{core-file} and @code{exec-file} commands to select a new core
19011 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19012 specify as a target a process that is already running, use the @code{attach}
19013 command (@pxref{Attach, ,Debugging an Already-running Process}).
19015 @node Target Commands
19016 @section Commands for Managing Targets
19019 @item target @var{type} @var{parameters}
19020 Connects the @value{GDBN} host environment to a target machine or
19021 process. A target is typically a protocol for talking to debugging
19022 facilities. You use the argument @var{type} to specify the type or
19023 protocol of the target machine.
19025 Further @var{parameters} are interpreted by the target protocol, but
19026 typically include things like device names or host names to connect
19027 with, process numbers, and baud rates.
19029 The @code{target} command does not repeat if you press @key{RET} again
19030 after executing the command.
19032 @kindex help target
19034 Displays the names of all targets available. To display targets
19035 currently selected, use either @code{info target} or @code{info files}
19036 (@pxref{Files, ,Commands to Specify Files}).
19038 @item help target @var{name}
19039 Describe a particular target, including any parameters necessary to
19042 @kindex set gnutarget
19043 @item set gnutarget @var{args}
19044 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19045 knows whether it is reading an @dfn{executable},
19046 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19047 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19048 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19051 @emph{Warning:} To specify a file format with @code{set gnutarget},
19052 you must know the actual BFD name.
19056 @xref{Files, , Commands to Specify Files}.
19058 @kindex show gnutarget
19059 @item show gnutarget
19060 Use the @code{show gnutarget} command to display what file format
19061 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19062 @value{GDBN} will determine the file format for each file automatically,
19063 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19066 @cindex common targets
19067 Here are some common targets (available, or not, depending on the GDB
19072 @item target exec @var{program}
19073 @cindex executable file target
19074 An executable file. @samp{target exec @var{program}} is the same as
19075 @samp{exec-file @var{program}}.
19077 @item target core @var{filename}
19078 @cindex core dump file target
19079 A core dump file. @samp{target core @var{filename}} is the same as
19080 @samp{core-file @var{filename}}.
19082 @item target remote @var{medium}
19083 @cindex remote target
19084 A remote system connected to @value{GDBN} via a serial line or network
19085 connection. This command tells @value{GDBN} to use its own remote
19086 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19088 For example, if you have a board connected to @file{/dev/ttya} on the
19089 machine running @value{GDBN}, you could say:
19092 target remote /dev/ttya
19095 @code{target remote} supports the @code{load} command. This is only
19096 useful if you have some other way of getting the stub to the target
19097 system, and you can put it somewhere in memory where it won't get
19098 clobbered by the download.
19100 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19101 @cindex built-in simulator target
19102 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19110 works; however, you cannot assume that a specific memory map, device
19111 drivers, or even basic I/O is available, although some simulators do
19112 provide these. For info about any processor-specific simulator details,
19113 see the appropriate section in @ref{Embedded Processors, ,Embedded
19116 @item target native
19117 @cindex native target
19118 Setup for local/native process debugging. Useful to make the
19119 @code{run} command spawn native processes (likewise @code{attach},
19120 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19121 (@pxref{set auto-connect-native-target}).
19125 Different targets are available on different configurations of @value{GDBN};
19126 your configuration may have more or fewer targets.
19128 Many remote targets require you to download the executable's code once
19129 you've successfully established a connection. You may wish to control
19130 various aspects of this process.
19135 @kindex set hash@r{, for remote monitors}
19136 @cindex hash mark while downloading
19137 This command controls whether a hash mark @samp{#} is displayed while
19138 downloading a file to the remote monitor. If on, a hash mark is
19139 displayed after each S-record is successfully downloaded to the
19143 @kindex show hash@r{, for remote monitors}
19144 Show the current status of displaying the hash mark.
19146 @item set debug monitor
19147 @kindex set debug monitor
19148 @cindex display remote monitor communications
19149 Enable or disable display of communications messages between
19150 @value{GDBN} and the remote monitor.
19152 @item show debug monitor
19153 @kindex show debug monitor
19154 Show the current status of displaying communications between
19155 @value{GDBN} and the remote monitor.
19160 @kindex load @var{filename}
19161 @item load @var{filename}
19163 Depending on what remote debugging facilities are configured into
19164 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19165 is meant to make @var{filename} (an executable) available for debugging
19166 on the remote system---by downloading, or dynamic linking, for example.
19167 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19168 the @code{add-symbol-file} command.
19170 If your @value{GDBN} does not have a @code{load} command, attempting to
19171 execute it gets the error message ``@code{You can't do that when your
19172 target is @dots{}}''
19174 The file is loaded at whatever address is specified in the executable.
19175 For some object file formats, you can specify the load address when you
19176 link the program; for other formats, like a.out, the object file format
19177 specifies a fixed address.
19178 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19180 Depending on the remote side capabilities, @value{GDBN} may be able to
19181 load programs into flash memory.
19183 @code{load} does not repeat if you press @key{RET} again after using it.
19187 @section Choosing Target Byte Order
19189 @cindex choosing target byte order
19190 @cindex target byte order
19192 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19193 offer the ability to run either big-endian or little-endian byte
19194 orders. Usually the executable or symbol will include a bit to
19195 designate the endian-ness, and you will not need to worry about
19196 which to use. However, you may still find it useful to adjust
19197 @value{GDBN}'s idea of processor endian-ness manually.
19201 @item set endian big
19202 Instruct @value{GDBN} to assume the target is big-endian.
19204 @item set endian little
19205 Instruct @value{GDBN} to assume the target is little-endian.
19207 @item set endian auto
19208 Instruct @value{GDBN} to use the byte order associated with the
19212 Display @value{GDBN}'s current idea of the target byte order.
19216 Note that these commands merely adjust interpretation of symbolic
19217 data on the host, and that they have absolutely no effect on the
19221 @node Remote Debugging
19222 @chapter Debugging Remote Programs
19223 @cindex remote debugging
19225 If you are trying to debug a program running on a machine that cannot run
19226 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19227 For example, you might use remote debugging on an operating system kernel,
19228 or on a small system which does not have a general purpose operating system
19229 powerful enough to run a full-featured debugger.
19231 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19232 to make this work with particular debugging targets. In addition,
19233 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19234 but not specific to any particular target system) which you can use if you
19235 write the remote stubs---the code that runs on the remote system to
19236 communicate with @value{GDBN}.
19238 Other remote targets may be available in your
19239 configuration of @value{GDBN}; use @code{help target} to list them.
19242 * Connecting:: Connecting to a remote target
19243 * File Transfer:: Sending files to a remote system
19244 * Server:: Using the gdbserver program
19245 * Remote Configuration:: Remote configuration
19246 * Remote Stub:: Implementing a remote stub
19250 @section Connecting to a Remote Target
19252 @value{GDBN} needs an unstripped copy of your program to access symbol
19253 and debugging information. Some remote targets (@pxref{qXfer
19254 executable filename read}, and @pxref{Host I/O Packets}) allow
19255 @value{GDBN} to access program files over the same connection used to
19256 communicate with @value{GDBN}. With such a target, if the remote
19257 program is unstripped, the only command you need is @code{target
19258 remote}. Otherwise, start up @value{GDBN} using the name of the local
19259 unstripped copy of your program as the first argument, or use the
19260 @code{file} command.
19262 @cindex @code{target remote}
19263 @value{GDBN} can communicate with the target over a serial line, or
19264 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19265 each case, @value{GDBN} uses the same protocol for debugging your
19266 program; only the medium carrying the debugging packets varies. The
19267 @code{target remote} command establishes a connection to the target.
19268 Its arguments indicate which medium to use:
19272 @item target remote @var{serial-device}
19273 @cindex serial line, @code{target remote}
19274 Use @var{serial-device} to communicate with the target. For example,
19275 to use a serial line connected to the device named @file{/dev/ttyb}:
19278 target remote /dev/ttyb
19281 If you're using a serial line, you may want to give @value{GDBN} the
19282 @samp{--baud} option, or use the @code{set serial baud} command
19283 (@pxref{Remote Configuration, set serial baud}) before the
19284 @code{target} command.
19286 @item target remote @code{@var{host}:@var{port}}
19287 @itemx target remote @code{tcp:@var{host}:@var{port}}
19288 @cindex @acronym{TCP} port, @code{target remote}
19289 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19290 The @var{host} may be either a host name or a numeric @acronym{IP}
19291 address; @var{port} must be a decimal number. The @var{host} could be
19292 the target machine itself, if it is directly connected to the net, or
19293 it might be a terminal server which in turn has a serial line to the
19296 For example, to connect to port 2828 on a terminal server named
19300 target remote manyfarms:2828
19303 If your remote target is actually running on the same machine as your
19304 debugger session (e.g.@: a simulator for your target running on the
19305 same host), you can omit the hostname. For example, to connect to
19306 port 1234 on your local machine:
19309 target remote :1234
19313 Note that the colon is still required here.
19315 @item target remote @code{udp:@var{host}:@var{port}}
19316 @cindex @acronym{UDP} port, @code{target remote}
19317 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19318 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19321 target remote udp:manyfarms:2828
19324 When using a @acronym{UDP} connection for remote debugging, you should
19325 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19326 can silently drop packets on busy or unreliable networks, which will
19327 cause havoc with your debugging session.
19329 @item target remote | @var{command}
19330 @cindex pipe, @code{target remote} to
19331 Run @var{command} in the background and communicate with it using a
19332 pipe. The @var{command} is a shell command, to be parsed and expanded
19333 by the system's command shell, @code{/bin/sh}; it should expect remote
19334 protocol packets on its standard input, and send replies on its
19335 standard output. You could use this to run a stand-alone simulator
19336 that speaks the remote debugging protocol, to make net connections
19337 using programs like @code{ssh}, or for other similar tricks.
19339 If @var{command} closes its standard output (perhaps by exiting),
19340 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19341 program has already exited, this will have no effect.)
19345 Once the connection has been established, you can use all the usual
19346 commands to examine and change data. The remote program is already
19347 running; you can use @kbd{step} and @kbd{continue}, and you do not
19348 need to use @kbd{run}.
19350 @cindex interrupting remote programs
19351 @cindex remote programs, interrupting
19352 Whenever @value{GDBN} is waiting for the remote program, if you type the
19353 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19354 program. This may or may not succeed, depending in part on the hardware
19355 and the serial drivers the remote system uses. If you type the
19356 interrupt character once again, @value{GDBN} displays this prompt:
19359 Interrupted while waiting for the program.
19360 Give up (and stop debugging it)? (y or n)
19363 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
19364 (If you decide you want to try again later, you can use @samp{target
19365 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
19366 goes back to waiting.
19369 @kindex detach (remote)
19371 When you have finished debugging the remote program, you can use the
19372 @code{detach} command to release it from @value{GDBN} control.
19373 Detaching from the target normally resumes its execution, but the results
19374 will depend on your particular remote stub. After the @code{detach}
19375 command, @value{GDBN} is free to connect to another target.
19379 The @code{disconnect} command behaves like @code{detach}, except that
19380 the target is generally not resumed. It will wait for @value{GDBN}
19381 (this instance or another one) to connect and continue debugging. After
19382 the @code{disconnect} command, @value{GDBN} is again free to connect to
19385 @cindex send command to remote monitor
19386 @cindex extend @value{GDBN} for remote targets
19387 @cindex add new commands for external monitor
19389 @item monitor @var{cmd}
19390 This command allows you to send arbitrary commands directly to the
19391 remote monitor. Since @value{GDBN} doesn't care about the commands it
19392 sends like this, this command is the way to extend @value{GDBN}---you
19393 can add new commands that only the external monitor will understand
19397 @node File Transfer
19398 @section Sending files to a remote system
19399 @cindex remote target, file transfer
19400 @cindex file transfer
19401 @cindex sending files to remote systems
19403 Some remote targets offer the ability to transfer files over the same
19404 connection used to communicate with @value{GDBN}. This is convenient
19405 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19406 running @code{gdbserver} over a network interface. For other targets,
19407 e.g.@: embedded devices with only a single serial port, this may be
19408 the only way to upload or download files.
19410 Not all remote targets support these commands.
19414 @item remote put @var{hostfile} @var{targetfile}
19415 Copy file @var{hostfile} from the host system (the machine running
19416 @value{GDBN}) to @var{targetfile} on the target system.
19419 @item remote get @var{targetfile} @var{hostfile}
19420 Copy file @var{targetfile} from the target system to @var{hostfile}
19421 on the host system.
19423 @kindex remote delete
19424 @item remote delete @var{targetfile}
19425 Delete @var{targetfile} from the target system.
19430 @section Using the @code{gdbserver} Program
19433 @cindex remote connection without stubs
19434 @code{gdbserver} is a control program for Unix-like systems, which
19435 allows you to connect your program with a remote @value{GDBN} via
19436 @code{target remote}---but without linking in the usual debugging stub.
19438 @code{gdbserver} is not a complete replacement for the debugging stubs,
19439 because it requires essentially the same operating-system facilities
19440 that @value{GDBN} itself does. In fact, a system that can run
19441 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19442 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19443 because it is a much smaller program than @value{GDBN} itself. It is
19444 also easier to port than all of @value{GDBN}, so you may be able to get
19445 started more quickly on a new system by using @code{gdbserver}.
19446 Finally, if you develop code for real-time systems, you may find that
19447 the tradeoffs involved in real-time operation make it more convenient to
19448 do as much development work as possible on another system, for example
19449 by cross-compiling. You can use @code{gdbserver} to make a similar
19450 choice for debugging.
19452 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19453 or a TCP connection, using the standard @value{GDBN} remote serial
19457 @emph{Warning:} @code{gdbserver} does not have any built-in security.
19458 Do not run @code{gdbserver} connected to any public network; a
19459 @value{GDBN} connection to @code{gdbserver} provides access to the
19460 target system with the same privileges as the user running
19464 @subsection Running @code{gdbserver}
19465 @cindex arguments, to @code{gdbserver}
19466 @cindex @code{gdbserver}, command-line arguments
19468 Run @code{gdbserver} on the target system. You need a copy of the
19469 program you want to debug, including any libraries it requires.
19470 @code{gdbserver} does not need your program's symbol table, so you can
19471 strip the program if necessary to save space. @value{GDBN} on the host
19472 system does all the symbol handling.
19474 To use the server, you must tell it how to communicate with @value{GDBN};
19475 the name of your program; and the arguments for your program. The usual
19479 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
19482 @var{comm} is either a device name (to use a serial line), or a TCP
19483 hostname and portnumber, or @code{-} or @code{stdio} to use
19484 stdin/stdout of @code{gdbserver}.
19485 For example, to debug Emacs with the argument
19486 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
19490 target> gdbserver /dev/com1 emacs foo.txt
19493 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
19496 To use a TCP connection instead of a serial line:
19499 target> gdbserver host:2345 emacs foo.txt
19502 The only difference from the previous example is the first argument,
19503 specifying that you are communicating with the host @value{GDBN} via
19504 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
19505 expect a TCP connection from machine @samp{host} to local TCP port 2345.
19506 (Currently, the @samp{host} part is ignored.) You can choose any number
19507 you want for the port number as long as it does not conflict with any
19508 TCP ports already in use on the target system (for example, @code{23} is
19509 reserved for @code{telnet}).@footnote{If you choose a port number that
19510 conflicts with another service, @code{gdbserver} prints an error message
19511 and exits.} You must use the same port number with the host @value{GDBN}
19512 @code{target remote} command.
19514 The @code{stdio} connection is useful when starting @code{gdbserver}
19518 (gdb) target remote | ssh -T hostname gdbserver - hello
19521 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19522 and we don't want escape-character handling. Ssh does this by default when
19523 a command is provided, the flag is provided to make it explicit.
19524 You could elide it if you want to.
19526 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19527 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19528 display through a pipe connected to gdbserver.
19529 Both @code{stdout} and @code{stderr} use the same pipe.
19531 @subsubsection Attaching to a Running Program
19532 @cindex attach to a program, @code{gdbserver}
19533 @cindex @option{--attach}, @code{gdbserver} option
19535 On some targets, @code{gdbserver} can also attach to running programs.
19536 This is accomplished via the @code{--attach} argument. The syntax is:
19539 target> gdbserver --attach @var{comm} @var{pid}
19542 @var{pid} is the process ID of a currently running process. It isn't necessary
19543 to point @code{gdbserver} at a binary for the running process.
19546 You can debug processes by name instead of process ID if your target has the
19547 @code{pidof} utility:
19550 target> gdbserver --attach @var{comm} `pidof @var{program}`
19553 In case more than one copy of @var{program} is running, or @var{program}
19554 has multiple threads, most versions of @code{pidof} support the
19555 @code{-s} option to only return the first process ID.
19557 @subsubsection Multi-Process Mode for @code{gdbserver}
19558 @cindex @code{gdbserver}, multiple processes
19559 @cindex multiple processes with @code{gdbserver}
19561 When you connect to @code{gdbserver} using @code{target remote},
19562 @code{gdbserver} debugs the specified program only once. When the
19563 program exits, or you detach from it, @value{GDBN} closes the connection
19564 and @code{gdbserver} exits.
19566 If you connect using @kbd{target extended-remote}, @code{gdbserver}
19567 enters multi-process mode. When the debugged program exits, or you
19568 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
19569 though no program is running. The @code{run} and @code{attach}
19570 commands instruct @code{gdbserver} to run or attach to a new program.
19571 The @code{run} command uses @code{set remote exec-file} (@pxref{set
19572 remote exec-file}) to select the program to run. Command line
19573 arguments are supported, except for wildcard expansion and I/O
19574 redirection (@pxref{Arguments}).
19576 @cindex @option{--multi}, @code{gdbserver} option
19577 To start @code{gdbserver} without supplying an initial command to run
19578 or process ID to attach, use the @option{--multi} command line option.
19579 Then you can connect using @kbd{target extended-remote} and start
19580 the program you want to debug.
19582 In multi-process mode @code{gdbserver} does not automatically exit unless you
19583 use the option @option{--once}. You can terminate it by using
19584 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
19585 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
19586 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
19587 @option{--multi} option to @code{gdbserver} has no influence on that.
19589 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19591 This section applies only when @code{gdbserver} is run to listen on a TCP port.
19593 @code{gdbserver} normally terminates after all of its debugged processes have
19594 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19595 extended-remote}, @code{gdbserver} stays running even with no processes left.
19596 @value{GDBN} normally terminates the spawned debugged process on its exit,
19597 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19598 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19599 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19600 stays running even in the @kbd{target remote} mode.
19602 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19603 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19604 completeness, at most one @value{GDBN} can be connected at a time.
19606 @cindex @option{--once}, @code{gdbserver} option
19607 By default, @code{gdbserver} keeps the listening TCP port open, so that
19608 subsequent connections are possible. However, if you start @code{gdbserver}
19609 with the @option{--once} option, it will stop listening for any further
19610 connection attempts after connecting to the first @value{GDBN} session. This
19611 means no further connections to @code{gdbserver} will be possible after the
19612 first one. It also means @code{gdbserver} will terminate after the first
19613 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19614 connections and even in the @kbd{target extended-remote} mode. The
19615 @option{--once} option allows reusing the same port number for connecting to
19616 multiple instances of @code{gdbserver} running on the same host, since each
19617 instance closes its port after the first connection.
19619 @anchor{Other Command-Line Arguments for gdbserver}
19620 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19622 @cindex @option{--debug}, @code{gdbserver} option
19623 The @option{--debug} option tells @code{gdbserver} to display extra
19624 status information about the debugging process.
19625 @cindex @option{--remote-debug}, @code{gdbserver} option
19626 The @option{--remote-debug} option tells @code{gdbserver} to display
19627 remote protocol debug output. These options are intended for
19628 @code{gdbserver} development and for bug reports to the developers.
19630 @cindex @option{--debug-format}, @code{gdbserver} option
19631 The @option{--debug-format=option1[,option2,...]} option tells
19632 @code{gdbserver} to include additional information in each output.
19633 Possible options are:
19637 Turn off all extra information in debugging output.
19639 Turn on all extra information in debugging output.
19641 Include a timestamp in each line of debugging output.
19644 Options are processed in order. Thus, for example, if @option{none}
19645 appears last then no additional information is added to debugging output.
19647 @cindex @option{--wrapper}, @code{gdbserver} option
19648 The @option{--wrapper} option specifies a wrapper to launch programs
19649 for debugging. The option should be followed by the name of the
19650 wrapper, then any command-line arguments to pass to the wrapper, then
19651 @kbd{--} indicating the end of the wrapper arguments.
19653 @code{gdbserver} runs the specified wrapper program with a combined
19654 command line including the wrapper arguments, then the name of the
19655 program to debug, then any arguments to the program. The wrapper
19656 runs until it executes your program, and then @value{GDBN} gains control.
19658 You can use any program that eventually calls @code{execve} with
19659 its arguments as a wrapper. Several standard Unix utilities do
19660 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19661 with @code{exec "$@@"} will also work.
19663 For example, you can use @code{env} to pass an environment variable to
19664 the debugged program, without setting the variable in @code{gdbserver}'s
19668 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19671 @subsection Connecting to @code{gdbserver}
19673 Run @value{GDBN} on the host system.
19675 First make sure you have the necessary symbol files. Load symbols for
19676 your application using the @code{file} command before you connect. Use
19677 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
19678 was compiled with the correct sysroot using @code{--with-sysroot}).
19680 The symbol file and target libraries must exactly match the executable
19681 and libraries on the target, with one exception: the files on the host
19682 system should not be stripped, even if the files on the target system
19683 are. Mismatched or missing files will lead to confusing results
19684 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19685 files may also prevent @code{gdbserver} from debugging multi-threaded
19688 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19689 For TCP connections, you must start up @code{gdbserver} prior to using
19690 the @code{target remote} command. Otherwise you may get an error whose
19691 text depends on the host system, but which usually looks something like
19692 @samp{Connection refused}. Don't use the @code{load}
19693 command in @value{GDBN} when using @code{gdbserver}, since the program is
19694 already on the target.
19696 @subsection Monitor Commands for @code{gdbserver}
19697 @cindex monitor commands, for @code{gdbserver}
19698 @anchor{Monitor Commands for gdbserver}
19700 During a @value{GDBN} session using @code{gdbserver}, you can use the
19701 @code{monitor} command to send special requests to @code{gdbserver}.
19702 Here are the available commands.
19706 List the available monitor commands.
19708 @item monitor set debug 0
19709 @itemx monitor set debug 1
19710 Disable or enable general debugging messages.
19712 @item monitor set remote-debug 0
19713 @itemx monitor set remote-debug 1
19714 Disable or enable specific debugging messages associated with the remote
19715 protocol (@pxref{Remote Protocol}).
19717 @item monitor set debug-format option1@r{[},option2,...@r{]}
19718 Specify additional text to add to debugging messages.
19719 Possible options are:
19723 Turn off all extra information in debugging output.
19725 Turn on all extra information in debugging output.
19727 Include a timestamp in each line of debugging output.
19730 Options are processed in order. Thus, for example, if @option{none}
19731 appears last then no additional information is added to debugging output.
19733 @item monitor set libthread-db-search-path [PATH]
19734 @cindex gdbserver, search path for @code{libthread_db}
19735 When this command is issued, @var{path} is a colon-separated list of
19736 directories to search for @code{libthread_db} (@pxref{Threads,,set
19737 libthread-db-search-path}). If you omit @var{path},
19738 @samp{libthread-db-search-path} will be reset to its default value.
19740 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19741 not supported in @code{gdbserver}.
19744 Tell gdbserver to exit immediately. This command should be followed by
19745 @code{disconnect} to close the debugging session. @code{gdbserver} will
19746 detach from any attached processes and kill any processes it created.
19747 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19748 of a multi-process mode debug session.
19752 @subsection Tracepoints support in @code{gdbserver}
19753 @cindex tracepoints support in @code{gdbserver}
19755 On some targets, @code{gdbserver} supports tracepoints, fast
19756 tracepoints and static tracepoints.
19758 For fast or static tracepoints to work, a special library called the
19759 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19760 This library is built and distributed as an integral part of
19761 @code{gdbserver}. In addition, support for static tracepoints
19762 requires building the in-process agent library with static tracepoints
19763 support. At present, the UST (LTTng Userspace Tracer,
19764 @url{http://lttng.org/ust}) tracing engine is supported. This support
19765 is automatically available if UST development headers are found in the
19766 standard include path when @code{gdbserver} is built, or if
19767 @code{gdbserver} was explicitly configured using @option{--with-ust}
19768 to point at such headers. You can explicitly disable the support
19769 using @option{--with-ust=no}.
19771 There are several ways to load the in-process agent in your program:
19774 @item Specifying it as dependency at link time
19776 You can link your program dynamically with the in-process agent
19777 library. On most systems, this is accomplished by adding
19778 @code{-linproctrace} to the link command.
19780 @item Using the system's preloading mechanisms
19782 You can force loading the in-process agent at startup time by using
19783 your system's support for preloading shared libraries. Many Unixes
19784 support the concept of preloading user defined libraries. In most
19785 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19786 in the environment. See also the description of @code{gdbserver}'s
19787 @option{--wrapper} command line option.
19789 @item Using @value{GDBN} to force loading the agent at run time
19791 On some systems, you can force the inferior to load a shared library,
19792 by calling a dynamic loader function in the inferior that takes care
19793 of dynamically looking up and loading a shared library. On most Unix
19794 systems, the function is @code{dlopen}. You'll use the @code{call}
19795 command for that. For example:
19798 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19801 Note that on most Unix systems, for the @code{dlopen} function to be
19802 available, the program needs to be linked with @code{-ldl}.
19805 On systems that have a userspace dynamic loader, like most Unix
19806 systems, when you connect to @code{gdbserver} using @code{target
19807 remote}, you'll find that the program is stopped at the dynamic
19808 loader's entry point, and no shared library has been loaded in the
19809 program's address space yet, including the in-process agent. In that
19810 case, before being able to use any of the fast or static tracepoints
19811 features, you need to let the loader run and load the shared
19812 libraries. The simplest way to do that is to run the program to the
19813 main procedure. E.g., if debugging a C or C@t{++} program, start
19814 @code{gdbserver} like so:
19817 $ gdbserver :9999 myprogram
19820 Start GDB and connect to @code{gdbserver} like so, and run to main:
19824 (@value{GDBP}) target remote myhost:9999
19825 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
19826 (@value{GDBP}) b main
19827 (@value{GDBP}) continue
19830 The in-process tracing agent library should now be loaded into the
19831 process; you can confirm it with the @code{info sharedlibrary}
19832 command, which will list @file{libinproctrace.so} as loaded in the
19833 process. You are now ready to install fast tracepoints, list static
19834 tracepoint markers, probe static tracepoints markers, and start
19837 @node Remote Configuration
19838 @section Remote Configuration
19841 @kindex show remote
19842 This section documents the configuration options available when
19843 debugging remote programs. For the options related to the File I/O
19844 extensions of the remote protocol, see @ref{system,
19845 system-call-allowed}.
19848 @item set remoteaddresssize @var{bits}
19849 @cindex address size for remote targets
19850 @cindex bits in remote address
19851 Set the maximum size of address in a memory packet to the specified
19852 number of bits. @value{GDBN} will mask off the address bits above
19853 that number, when it passes addresses to the remote target. The
19854 default value is the number of bits in the target's address.
19856 @item show remoteaddresssize
19857 Show the current value of remote address size in bits.
19859 @item set serial baud @var{n}
19860 @cindex baud rate for remote targets
19861 Set the baud rate for the remote serial I/O to @var{n} baud. The
19862 value is used to set the speed of the serial port used for debugging
19865 @item show serial baud
19866 Show the current speed of the remote connection.
19868 @item set serial parity @var{parity}
19869 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
19870 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
19872 @item show serial parity
19873 Show the current parity of the serial port.
19875 @item set remotebreak
19876 @cindex interrupt remote programs
19877 @cindex BREAK signal instead of Ctrl-C
19878 @anchor{set remotebreak}
19879 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19880 when you type @kbd{Ctrl-c} to interrupt the program running
19881 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19882 character instead. The default is off, since most remote systems
19883 expect to see @samp{Ctrl-C} as the interrupt signal.
19885 @item show remotebreak
19886 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19887 interrupt the remote program.
19889 @item set remoteflow on
19890 @itemx set remoteflow off
19891 @kindex set remoteflow
19892 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
19893 on the serial port used to communicate to the remote target.
19895 @item show remoteflow
19896 @kindex show remoteflow
19897 Show the current setting of hardware flow control.
19899 @item set remotelogbase @var{base}
19900 Set the base (a.k.a.@: radix) of logging serial protocol
19901 communications to @var{base}. Supported values of @var{base} are:
19902 @code{ascii}, @code{octal}, and @code{hex}. The default is
19905 @item show remotelogbase
19906 Show the current setting of the radix for logging remote serial
19909 @item set remotelogfile @var{file}
19910 @cindex record serial communications on file
19911 Record remote serial communications on the named @var{file}. The
19912 default is not to record at all.
19914 @item show remotelogfile.
19915 Show the current setting of the file name on which to record the
19916 serial communications.
19918 @item set remotetimeout @var{num}
19919 @cindex timeout for serial communications
19920 @cindex remote timeout
19921 Set the timeout limit to wait for the remote target to respond to
19922 @var{num} seconds. The default is 2 seconds.
19924 @item show remotetimeout
19925 Show the current number of seconds to wait for the remote target
19928 @cindex limit hardware breakpoints and watchpoints
19929 @cindex remote target, limit break- and watchpoints
19930 @anchor{set remote hardware-watchpoint-limit}
19931 @anchor{set remote hardware-breakpoint-limit}
19932 @item set remote hardware-watchpoint-limit @var{limit}
19933 @itemx set remote hardware-breakpoint-limit @var{limit}
19934 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
19935 watchpoints. A limit of -1, the default, is treated as unlimited.
19937 @cindex limit hardware watchpoints length
19938 @cindex remote target, limit watchpoints length
19939 @anchor{set remote hardware-watchpoint-length-limit}
19940 @item set remote hardware-watchpoint-length-limit @var{limit}
19941 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
19942 a remote hardware watchpoint. A limit of -1, the default, is treated
19945 @item show remote hardware-watchpoint-length-limit
19946 Show the current limit (in bytes) of the maximum length of
19947 a remote hardware watchpoint.
19949 @item set remote exec-file @var{filename}
19950 @itemx show remote exec-file
19951 @anchor{set remote exec-file}
19952 @cindex executable file, for remote target
19953 Select the file used for @code{run} with @code{target
19954 extended-remote}. This should be set to a filename valid on the
19955 target system. If it is not set, the target will use a default
19956 filename (e.g.@: the last program run).
19958 @item set remote interrupt-sequence
19959 @cindex interrupt remote programs
19960 @cindex select Ctrl-C, BREAK or BREAK-g
19961 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
19962 @samp{BREAK-g} as the
19963 sequence to the remote target in order to interrupt the execution.
19964 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
19965 is high level of serial line for some certain time.
19966 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
19967 It is @code{BREAK} signal followed by character @code{g}.
19969 @item show interrupt-sequence
19970 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
19971 is sent by @value{GDBN} to interrupt the remote program.
19972 @code{BREAK-g} is BREAK signal followed by @code{g} and
19973 also known as Magic SysRq g.
19975 @item set remote interrupt-on-connect
19976 @cindex send interrupt-sequence on start
19977 Specify whether interrupt-sequence is sent to remote target when
19978 @value{GDBN} connects to it. This is mostly needed when you debug
19979 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
19980 which is known as Magic SysRq g in order to connect @value{GDBN}.
19982 @item show interrupt-on-connect
19983 Show whether interrupt-sequence is sent
19984 to remote target when @value{GDBN} connects to it.
19988 @item set tcp auto-retry on
19989 @cindex auto-retry, for remote TCP target
19990 Enable auto-retry for remote TCP connections. This is useful if the remote
19991 debugging agent is launched in parallel with @value{GDBN}; there is a race
19992 condition because the agent may not become ready to accept the connection
19993 before @value{GDBN} attempts to connect. When auto-retry is
19994 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
19995 to establish the connection using the timeout specified by
19996 @code{set tcp connect-timeout}.
19998 @item set tcp auto-retry off
19999 Do not auto-retry failed TCP connections.
20001 @item show tcp auto-retry
20002 Show the current auto-retry setting.
20004 @item set tcp connect-timeout @var{seconds}
20005 @itemx set tcp connect-timeout unlimited
20006 @cindex connection timeout, for remote TCP target
20007 @cindex timeout, for remote target connection
20008 Set the timeout for establishing a TCP connection to the remote target to
20009 @var{seconds}. The timeout affects both polling to retry failed connections
20010 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20011 that are merely slow to complete, and represents an approximate cumulative
20012 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20013 @value{GDBN} will keep attempting to establish a connection forever,
20014 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20016 @item show tcp connect-timeout
20017 Show the current connection timeout setting.
20020 @cindex remote packets, enabling and disabling
20021 The @value{GDBN} remote protocol autodetects the packets supported by
20022 your debugging stub. If you need to override the autodetection, you
20023 can use these commands to enable or disable individual packets. Each
20024 packet can be set to @samp{on} (the remote target supports this
20025 packet), @samp{off} (the remote target does not support this packet),
20026 or @samp{auto} (detect remote target support for this packet). They
20027 all default to @samp{auto}. For more information about each packet,
20028 see @ref{Remote Protocol}.
20030 During normal use, you should not have to use any of these commands.
20031 If you do, that may be a bug in your remote debugging stub, or a bug
20032 in @value{GDBN}. You may want to report the problem to the
20033 @value{GDBN} developers.
20035 For each packet @var{name}, the command to enable or disable the
20036 packet is @code{set remote @var{name}-packet}. The available settings
20039 @multitable @columnfractions 0.28 0.32 0.25
20042 @tab Related Features
20044 @item @code{fetch-register}
20046 @tab @code{info registers}
20048 @item @code{set-register}
20052 @item @code{binary-download}
20054 @tab @code{load}, @code{set}
20056 @item @code{read-aux-vector}
20057 @tab @code{qXfer:auxv:read}
20058 @tab @code{info auxv}
20060 @item @code{symbol-lookup}
20061 @tab @code{qSymbol}
20062 @tab Detecting multiple threads
20064 @item @code{attach}
20065 @tab @code{vAttach}
20068 @item @code{verbose-resume}
20070 @tab Stepping or resuming multiple threads
20076 @item @code{software-breakpoint}
20080 @item @code{hardware-breakpoint}
20084 @item @code{write-watchpoint}
20088 @item @code{read-watchpoint}
20092 @item @code{access-watchpoint}
20096 @item @code{pid-to-exec-file}
20097 @tab @code{qXfer:exec-file:read}
20098 @tab @code{attach}, @code{run}
20100 @item @code{target-features}
20101 @tab @code{qXfer:features:read}
20102 @tab @code{set architecture}
20104 @item @code{library-info}
20105 @tab @code{qXfer:libraries:read}
20106 @tab @code{info sharedlibrary}
20108 @item @code{memory-map}
20109 @tab @code{qXfer:memory-map:read}
20110 @tab @code{info mem}
20112 @item @code{read-sdata-object}
20113 @tab @code{qXfer:sdata:read}
20114 @tab @code{print $_sdata}
20116 @item @code{read-spu-object}
20117 @tab @code{qXfer:spu:read}
20118 @tab @code{info spu}
20120 @item @code{write-spu-object}
20121 @tab @code{qXfer:spu:write}
20122 @tab @code{info spu}
20124 @item @code{read-siginfo-object}
20125 @tab @code{qXfer:siginfo:read}
20126 @tab @code{print $_siginfo}
20128 @item @code{write-siginfo-object}
20129 @tab @code{qXfer:siginfo:write}
20130 @tab @code{set $_siginfo}
20132 @item @code{threads}
20133 @tab @code{qXfer:threads:read}
20134 @tab @code{info threads}
20136 @item @code{get-thread-local-@*storage-address}
20137 @tab @code{qGetTLSAddr}
20138 @tab Displaying @code{__thread} variables
20140 @item @code{get-thread-information-block-address}
20141 @tab @code{qGetTIBAddr}
20142 @tab Display MS-Windows Thread Information Block.
20144 @item @code{search-memory}
20145 @tab @code{qSearch:memory}
20148 @item @code{supported-packets}
20149 @tab @code{qSupported}
20150 @tab Remote communications parameters
20152 @item @code{pass-signals}
20153 @tab @code{QPassSignals}
20154 @tab @code{handle @var{signal}}
20156 @item @code{program-signals}
20157 @tab @code{QProgramSignals}
20158 @tab @code{handle @var{signal}}
20160 @item @code{hostio-close-packet}
20161 @tab @code{vFile:close}
20162 @tab @code{remote get}, @code{remote put}
20164 @item @code{hostio-open-packet}
20165 @tab @code{vFile:open}
20166 @tab @code{remote get}, @code{remote put}
20168 @item @code{hostio-pread-packet}
20169 @tab @code{vFile:pread}
20170 @tab @code{remote get}, @code{remote put}
20172 @item @code{hostio-pwrite-packet}
20173 @tab @code{vFile:pwrite}
20174 @tab @code{remote get}, @code{remote put}
20176 @item @code{hostio-unlink-packet}
20177 @tab @code{vFile:unlink}
20178 @tab @code{remote delete}
20180 @item @code{hostio-readlink-packet}
20181 @tab @code{vFile:readlink}
20184 @item @code{hostio-fstat-packet}
20185 @tab @code{vFile:fstat}
20188 @item @code{hostio-setfs-packet}
20189 @tab @code{vFile:setfs}
20192 @item @code{noack-packet}
20193 @tab @code{QStartNoAckMode}
20194 @tab Packet acknowledgment
20196 @item @code{osdata}
20197 @tab @code{qXfer:osdata:read}
20198 @tab @code{info os}
20200 @item @code{query-attached}
20201 @tab @code{qAttached}
20202 @tab Querying remote process attach state.
20204 @item @code{trace-buffer-size}
20205 @tab @code{QTBuffer:size}
20206 @tab @code{set trace-buffer-size}
20208 @item @code{trace-status}
20209 @tab @code{qTStatus}
20210 @tab @code{tstatus}
20212 @item @code{traceframe-info}
20213 @tab @code{qXfer:traceframe-info:read}
20214 @tab Traceframe info
20216 @item @code{install-in-trace}
20217 @tab @code{InstallInTrace}
20218 @tab Install tracepoint in tracing
20220 @item @code{disable-randomization}
20221 @tab @code{QDisableRandomization}
20222 @tab @code{set disable-randomization}
20224 @item @code{conditional-breakpoints-packet}
20225 @tab @code{Z0 and Z1}
20226 @tab @code{Support for target-side breakpoint condition evaluation}
20228 @item @code{multiprocess-extensions}
20229 @tab @code{multiprocess extensions}
20230 @tab Debug multiple processes and remote process PID awareness
20232 @item @code{swbreak-feature}
20233 @tab @code{swbreak stop reason}
20236 @item @code{hwbreak-feature}
20237 @tab @code{hwbreak stop reason}
20240 @item @code{fork-event-feature}
20241 @tab @code{fork stop reason}
20244 @item @code{vfork-event-feature}
20245 @tab @code{vfork stop reason}
20248 @item @code{exec-event-feature}
20249 @tab @code{exec stop reason}
20252 @item @code{thread-events}
20253 @tab @code{QThreadEvents}
20254 @tab Tracking thread lifetime.
20256 @item @code{no-resumed-stop-reply}
20257 @tab @code{no resumed thread left stop reply}
20258 @tab Tracking thread lifetime.
20263 @section Implementing a Remote Stub
20265 @cindex debugging stub, example
20266 @cindex remote stub, example
20267 @cindex stub example, remote debugging
20268 The stub files provided with @value{GDBN} implement the target side of the
20269 communication protocol, and the @value{GDBN} side is implemented in the
20270 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20271 these subroutines to communicate, and ignore the details. (If you're
20272 implementing your own stub file, you can still ignore the details: start
20273 with one of the existing stub files. @file{sparc-stub.c} is the best
20274 organized, and therefore the easiest to read.)
20276 @cindex remote serial debugging, overview
20277 To debug a program running on another machine (the debugging
20278 @dfn{target} machine), you must first arrange for all the usual
20279 prerequisites for the program to run by itself. For example, for a C
20284 A startup routine to set up the C runtime environment; these usually
20285 have a name like @file{crt0}. The startup routine may be supplied by
20286 your hardware supplier, or you may have to write your own.
20289 A C subroutine library to support your program's
20290 subroutine calls, notably managing input and output.
20293 A way of getting your program to the other machine---for example, a
20294 download program. These are often supplied by the hardware
20295 manufacturer, but you may have to write your own from hardware
20299 The next step is to arrange for your program to use a serial port to
20300 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20301 machine). In general terms, the scheme looks like this:
20305 @value{GDBN} already understands how to use this protocol; when everything
20306 else is set up, you can simply use the @samp{target remote} command
20307 (@pxref{Targets,,Specifying a Debugging Target}).
20309 @item On the target,
20310 you must link with your program a few special-purpose subroutines that
20311 implement the @value{GDBN} remote serial protocol. The file containing these
20312 subroutines is called a @dfn{debugging stub}.
20314 On certain remote targets, you can use an auxiliary program
20315 @code{gdbserver} instead of linking a stub into your program.
20316 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20319 The debugging stub is specific to the architecture of the remote
20320 machine; for example, use @file{sparc-stub.c} to debug programs on
20323 @cindex remote serial stub list
20324 These working remote stubs are distributed with @value{GDBN}:
20329 @cindex @file{i386-stub.c}
20332 For Intel 386 and compatible architectures.
20335 @cindex @file{m68k-stub.c}
20336 @cindex Motorola 680x0
20338 For Motorola 680x0 architectures.
20341 @cindex @file{sh-stub.c}
20344 For Renesas SH architectures.
20347 @cindex @file{sparc-stub.c}
20349 For @sc{sparc} architectures.
20351 @item sparcl-stub.c
20352 @cindex @file{sparcl-stub.c}
20355 For Fujitsu @sc{sparclite} architectures.
20359 The @file{README} file in the @value{GDBN} distribution may list other
20360 recently added stubs.
20363 * Stub Contents:: What the stub can do for you
20364 * Bootstrapping:: What you must do for the stub
20365 * Debug Session:: Putting it all together
20368 @node Stub Contents
20369 @subsection What the Stub Can Do for You
20371 @cindex remote serial stub
20372 The debugging stub for your architecture supplies these three
20376 @item set_debug_traps
20377 @findex set_debug_traps
20378 @cindex remote serial stub, initialization
20379 This routine arranges for @code{handle_exception} to run when your
20380 program stops. You must call this subroutine explicitly in your
20381 program's startup code.
20383 @item handle_exception
20384 @findex handle_exception
20385 @cindex remote serial stub, main routine
20386 This is the central workhorse, but your program never calls it
20387 explicitly---the setup code arranges for @code{handle_exception} to
20388 run when a trap is triggered.
20390 @code{handle_exception} takes control when your program stops during
20391 execution (for example, on a breakpoint), and mediates communications
20392 with @value{GDBN} on the host machine. This is where the communications
20393 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20394 representative on the target machine. It begins by sending summary
20395 information on the state of your program, then continues to execute,
20396 retrieving and transmitting any information @value{GDBN} needs, until you
20397 execute a @value{GDBN} command that makes your program resume; at that point,
20398 @code{handle_exception} returns control to your own code on the target
20402 @cindex @code{breakpoint} subroutine, remote
20403 Use this auxiliary subroutine to make your program contain a
20404 breakpoint. Depending on the particular situation, this may be the only
20405 way for @value{GDBN} to get control. For instance, if your target
20406 machine has some sort of interrupt button, you won't need to call this;
20407 pressing the interrupt button transfers control to
20408 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20409 simply receiving characters on the serial port may also trigger a trap;
20410 again, in that situation, you don't need to call @code{breakpoint} from
20411 your own program---simply running @samp{target remote} from the host
20412 @value{GDBN} session gets control.
20414 Call @code{breakpoint} if none of these is true, or if you simply want
20415 to make certain your program stops at a predetermined point for the
20416 start of your debugging session.
20419 @node Bootstrapping
20420 @subsection What You Must Do for the Stub
20422 @cindex remote stub, support routines
20423 The debugging stubs that come with @value{GDBN} are set up for a particular
20424 chip architecture, but they have no information about the rest of your
20425 debugging target machine.
20427 First of all you need to tell the stub how to communicate with the
20431 @item int getDebugChar()
20432 @findex getDebugChar
20433 Write this subroutine to read a single character from the serial port.
20434 It may be identical to @code{getchar} for your target system; a
20435 different name is used to allow you to distinguish the two if you wish.
20437 @item void putDebugChar(int)
20438 @findex putDebugChar
20439 Write this subroutine to write a single character to the serial port.
20440 It may be identical to @code{putchar} for your target system; a
20441 different name is used to allow you to distinguish the two if you wish.
20444 @cindex control C, and remote debugging
20445 @cindex interrupting remote targets
20446 If you want @value{GDBN} to be able to stop your program while it is
20447 running, you need to use an interrupt-driven serial driver, and arrange
20448 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20449 character). That is the character which @value{GDBN} uses to tell the
20450 remote system to stop.
20452 Getting the debugging target to return the proper status to @value{GDBN}
20453 probably requires changes to the standard stub; one quick and dirty way
20454 is to just execute a breakpoint instruction (the ``dirty'' part is that
20455 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20457 Other routines you need to supply are:
20460 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20461 @findex exceptionHandler
20462 Write this function to install @var{exception_address} in the exception
20463 handling tables. You need to do this because the stub does not have any
20464 way of knowing what the exception handling tables on your target system
20465 are like (for example, the processor's table might be in @sc{rom},
20466 containing entries which point to a table in @sc{ram}).
20467 The @var{exception_number} specifies the exception which should be changed;
20468 its meaning is architecture-dependent (for example, different numbers
20469 might represent divide by zero, misaligned access, etc). When this
20470 exception occurs, control should be transferred directly to
20471 @var{exception_address}, and the processor state (stack, registers,
20472 and so on) should be just as it is when a processor exception occurs. So if
20473 you want to use a jump instruction to reach @var{exception_address}, it
20474 should be a simple jump, not a jump to subroutine.
20476 For the 386, @var{exception_address} should be installed as an interrupt
20477 gate so that interrupts are masked while the handler runs. The gate
20478 should be at privilege level 0 (the most privileged level). The
20479 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
20480 help from @code{exceptionHandler}.
20482 @item void flush_i_cache()
20483 @findex flush_i_cache
20484 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
20485 instruction cache, if any, on your target machine. If there is no
20486 instruction cache, this subroutine may be a no-op.
20488 On target machines that have instruction caches, @value{GDBN} requires this
20489 function to make certain that the state of your program is stable.
20493 You must also make sure this library routine is available:
20496 @item void *memset(void *, int, int)
20498 This is the standard library function @code{memset} that sets an area of
20499 memory to a known value. If you have one of the free versions of
20500 @code{libc.a}, @code{memset} can be found there; otherwise, you must
20501 either obtain it from your hardware manufacturer, or write your own.
20504 If you do not use the GNU C compiler, you may need other standard
20505 library subroutines as well; this varies from one stub to another,
20506 but in general the stubs are likely to use any of the common library
20507 subroutines which @code{@value{NGCC}} generates as inline code.
20510 @node Debug Session
20511 @subsection Putting it All Together
20513 @cindex remote serial debugging summary
20514 In summary, when your program is ready to debug, you must follow these
20519 Make sure you have defined the supporting low-level routines
20520 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
20522 @code{getDebugChar}, @code{putDebugChar},
20523 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
20527 Insert these lines in your program's startup code, before the main
20528 procedure is called:
20535 On some machines, when a breakpoint trap is raised, the hardware
20536 automatically makes the PC point to the instruction after the
20537 breakpoint. If your machine doesn't do that, you may need to adjust
20538 @code{handle_exception} to arrange for it to return to the instruction
20539 after the breakpoint on this first invocation, so that your program
20540 doesn't keep hitting the initial breakpoint instead of making
20544 For the 680x0 stub only, you need to provide a variable called
20545 @code{exceptionHook}. Normally you just use:
20548 void (*exceptionHook)() = 0;
20552 but if before calling @code{set_debug_traps}, you set it to point to a
20553 function in your program, that function is called when
20554 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
20555 error). The function indicated by @code{exceptionHook} is called with
20556 one parameter: an @code{int} which is the exception number.
20559 Compile and link together: your program, the @value{GDBN} debugging stub for
20560 your target architecture, and the supporting subroutines.
20563 Make sure you have a serial connection between your target machine and
20564 the @value{GDBN} host, and identify the serial port on the host.
20567 @c The "remote" target now provides a `load' command, so we should
20568 @c document that. FIXME.
20569 Download your program to your target machine (or get it there by
20570 whatever means the manufacturer provides), and start it.
20573 Start @value{GDBN} on the host, and connect to the target
20574 (@pxref{Connecting,,Connecting to a Remote Target}).
20578 @node Configurations
20579 @chapter Configuration-Specific Information
20581 While nearly all @value{GDBN} commands are available for all native and
20582 cross versions of the debugger, there are some exceptions. This chapter
20583 describes things that are only available in certain configurations.
20585 There are three major categories of configurations: native
20586 configurations, where the host and target are the same, embedded
20587 operating system configurations, which are usually the same for several
20588 different processor architectures, and bare embedded processors, which
20589 are quite different from each other.
20594 * Embedded Processors::
20601 This section describes details specific to particular native
20605 * BSD libkvm Interface:: Debugging BSD kernel memory images
20606 * SVR4 Process Information:: SVR4 process information
20607 * DJGPP Native:: Features specific to the DJGPP port
20608 * Cygwin Native:: Features specific to the Cygwin port
20609 * Hurd Native:: Features specific to @sc{gnu} Hurd
20610 * Darwin:: Features specific to Darwin
20613 @node BSD libkvm Interface
20614 @subsection BSD libkvm Interface
20617 @cindex kernel memory image
20618 @cindex kernel crash dump
20620 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
20621 interface that provides a uniform interface for accessing kernel virtual
20622 memory images, including live systems and crash dumps. @value{GDBN}
20623 uses this interface to allow you to debug live kernels and kernel crash
20624 dumps on many native BSD configurations. This is implemented as a
20625 special @code{kvm} debugging target. For debugging a live system, load
20626 the currently running kernel into @value{GDBN} and connect to the
20630 (@value{GDBP}) @b{target kvm}
20633 For debugging crash dumps, provide the file name of the crash dump as an
20637 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20640 Once connected to the @code{kvm} target, the following commands are
20646 Set current context from the @dfn{Process Control Block} (PCB) address.
20649 Set current context from proc address. This command isn't available on
20650 modern FreeBSD systems.
20653 @node SVR4 Process Information
20654 @subsection SVR4 Process Information
20656 @cindex examine process image
20657 @cindex process info via @file{/proc}
20659 Many versions of SVR4 and compatible systems provide a facility called
20660 @samp{/proc} that can be used to examine the image of a running
20661 process using file-system subroutines.
20663 If @value{GDBN} is configured for an operating system with this
20664 facility, the command @code{info proc} is available to report
20665 information about the process running your program, or about any
20666 process running on your system. This includes, as of this writing,
20667 @sc{gnu}/Linux and Solaris, for example.
20669 This command may also work on core files that were created on a system
20670 that has the @samp{/proc} facility.
20676 @itemx info proc @var{process-id}
20677 Summarize available information about any running process. If a
20678 process ID is specified by @var{process-id}, display information about
20679 that process; otherwise display information about the program being
20680 debugged. The summary includes the debugged process ID, the command
20681 line used to invoke it, its current working directory, and its
20682 executable file's absolute file name.
20684 On some systems, @var{process-id} can be of the form
20685 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20686 within a process. If the optional @var{pid} part is missing, it means
20687 a thread from the process being debugged (the leading @samp{/} still
20688 needs to be present, or else @value{GDBN} will interpret the number as
20689 a process ID rather than a thread ID).
20691 @item info proc cmdline
20692 @cindex info proc cmdline
20693 Show the original command line of the process. This command is
20694 specific to @sc{gnu}/Linux.
20696 @item info proc cwd
20697 @cindex info proc cwd
20698 Show the current working directory of the process. This command is
20699 specific to @sc{gnu}/Linux.
20701 @item info proc exe
20702 @cindex info proc exe
20703 Show the name of executable of the process. This command is specific
20706 @item info proc mappings
20707 @cindex memory address space mappings
20708 Report the memory address space ranges accessible in the program, with
20709 information on whether the process has read, write, or execute access
20710 rights to each range. On @sc{gnu}/Linux systems, each memory range
20711 includes the object file which is mapped to that range, instead of the
20712 memory access rights to that range.
20714 @item info proc stat
20715 @itemx info proc status
20716 @cindex process detailed status information
20717 These subcommands are specific to @sc{gnu}/Linux systems. They show
20718 the process-related information, including the user ID and group ID;
20719 how many threads are there in the process; its virtual memory usage;
20720 the signals that are pending, blocked, and ignored; its TTY; its
20721 consumption of system and user time; its stack size; its @samp{nice}
20722 value; etc. For more information, see the @samp{proc} man page
20723 (type @kbd{man 5 proc} from your shell prompt).
20725 @item info proc all
20726 Show all the information about the process described under all of the
20727 above @code{info proc} subcommands.
20730 @comment These sub-options of 'info proc' were not included when
20731 @comment procfs.c was re-written. Keep their descriptions around
20732 @comment against the day when someone finds the time to put them back in.
20733 @kindex info proc times
20734 @item info proc times
20735 Starting time, user CPU time, and system CPU time for your program and
20738 @kindex info proc id
20740 Report on the process IDs related to your program: its own process ID,
20741 the ID of its parent, the process group ID, and the session ID.
20744 @item set procfs-trace
20745 @kindex set procfs-trace
20746 @cindex @code{procfs} API calls
20747 This command enables and disables tracing of @code{procfs} API calls.
20749 @item show procfs-trace
20750 @kindex show procfs-trace
20751 Show the current state of @code{procfs} API call tracing.
20753 @item set procfs-file @var{file}
20754 @kindex set procfs-file
20755 Tell @value{GDBN} to write @code{procfs} API trace to the named
20756 @var{file}. @value{GDBN} appends the trace info to the previous
20757 contents of the file. The default is to display the trace on the
20760 @item show procfs-file
20761 @kindex show procfs-file
20762 Show the file to which @code{procfs} API trace is written.
20764 @item proc-trace-entry
20765 @itemx proc-trace-exit
20766 @itemx proc-untrace-entry
20767 @itemx proc-untrace-exit
20768 @kindex proc-trace-entry
20769 @kindex proc-trace-exit
20770 @kindex proc-untrace-entry
20771 @kindex proc-untrace-exit
20772 These commands enable and disable tracing of entries into and exits
20773 from the @code{syscall} interface.
20776 @kindex info pidlist
20777 @cindex process list, QNX Neutrino
20778 For QNX Neutrino only, this command displays the list of all the
20779 processes and all the threads within each process.
20782 @kindex info meminfo
20783 @cindex mapinfo list, QNX Neutrino
20784 For QNX Neutrino only, this command displays the list of all mapinfos.
20788 @subsection Features for Debugging @sc{djgpp} Programs
20789 @cindex @sc{djgpp} debugging
20790 @cindex native @sc{djgpp} debugging
20791 @cindex MS-DOS-specific commands
20794 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20795 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20796 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20797 top of real-mode DOS systems and their emulations.
20799 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20800 defines a few commands specific to the @sc{djgpp} port. This
20801 subsection describes those commands.
20806 This is a prefix of @sc{djgpp}-specific commands which print
20807 information about the target system and important OS structures.
20810 @cindex MS-DOS system info
20811 @cindex free memory information (MS-DOS)
20812 @item info dos sysinfo
20813 This command displays assorted information about the underlying
20814 platform: the CPU type and features, the OS version and flavor, the
20815 DPMI version, and the available conventional and DPMI memory.
20820 @cindex segment descriptor tables
20821 @cindex descriptor tables display
20823 @itemx info dos ldt
20824 @itemx info dos idt
20825 These 3 commands display entries from, respectively, Global, Local,
20826 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
20827 tables are data structures which store a descriptor for each segment
20828 that is currently in use. The segment's selector is an index into a
20829 descriptor table; the table entry for that index holds the
20830 descriptor's base address and limit, and its attributes and access
20833 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
20834 segment (used for both data and the stack), and a DOS segment (which
20835 allows access to DOS/BIOS data structures and absolute addresses in
20836 conventional memory). However, the DPMI host will usually define
20837 additional segments in order to support the DPMI environment.
20839 @cindex garbled pointers
20840 These commands allow to display entries from the descriptor tables.
20841 Without an argument, all entries from the specified table are
20842 displayed. An argument, which should be an integer expression, means
20843 display a single entry whose index is given by the argument. For
20844 example, here's a convenient way to display information about the
20845 debugged program's data segment:
20848 @exdent @code{(@value{GDBP}) info dos ldt $ds}
20849 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
20853 This comes in handy when you want to see whether a pointer is outside
20854 the data segment's limit (i.e.@: @dfn{garbled}).
20856 @cindex page tables display (MS-DOS)
20858 @itemx info dos pte
20859 These two commands display entries from, respectively, the Page
20860 Directory and the Page Tables. Page Directories and Page Tables are
20861 data structures which control how virtual memory addresses are mapped
20862 into physical addresses. A Page Table includes an entry for every
20863 page of memory that is mapped into the program's address space; there
20864 may be several Page Tables, each one holding up to 4096 entries. A
20865 Page Directory has up to 4096 entries, one each for every Page Table
20866 that is currently in use.
20868 Without an argument, @kbd{info dos pde} displays the entire Page
20869 Directory, and @kbd{info dos pte} displays all the entries in all of
20870 the Page Tables. An argument, an integer expression, given to the
20871 @kbd{info dos pde} command means display only that entry from the Page
20872 Directory table. An argument given to the @kbd{info dos pte} command
20873 means display entries from a single Page Table, the one pointed to by
20874 the specified entry in the Page Directory.
20876 @cindex direct memory access (DMA) on MS-DOS
20877 These commands are useful when your program uses @dfn{DMA} (Direct
20878 Memory Access), which needs physical addresses to program the DMA
20881 These commands are supported only with some DPMI servers.
20883 @cindex physical address from linear address
20884 @item info dos address-pte @var{addr}
20885 This command displays the Page Table entry for a specified linear
20886 address. The argument @var{addr} is a linear address which should
20887 already have the appropriate segment's base address added to it,
20888 because this command accepts addresses which may belong to @emph{any}
20889 segment. For example, here's how to display the Page Table entry for
20890 the page where a variable @code{i} is stored:
20893 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
20894 @exdent @code{Page Table entry for address 0x11a00d30:}
20895 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
20899 This says that @code{i} is stored at offset @code{0xd30} from the page
20900 whose physical base address is @code{0x02698000}, and shows all the
20901 attributes of that page.
20903 Note that you must cast the addresses of variables to a @code{char *},
20904 since otherwise the value of @code{__djgpp_base_address}, the base
20905 address of all variables and functions in a @sc{djgpp} program, will
20906 be added using the rules of C pointer arithmetics: if @code{i} is
20907 declared an @code{int}, @value{GDBN} will add 4 times the value of
20908 @code{__djgpp_base_address} to the address of @code{i}.
20910 Here's another example, it displays the Page Table entry for the
20914 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
20915 @exdent @code{Page Table entry for address 0x29110:}
20916 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
20920 (The @code{+ 3} offset is because the transfer buffer's address is the
20921 3rd member of the @code{_go32_info_block} structure.) The output
20922 clearly shows that this DPMI server maps the addresses in conventional
20923 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
20924 linear (@code{0x29110}) addresses are identical.
20926 This command is supported only with some DPMI servers.
20929 @cindex DOS serial data link, remote debugging
20930 In addition to native debugging, the DJGPP port supports remote
20931 debugging via a serial data link. The following commands are specific
20932 to remote serial debugging in the DJGPP port of @value{GDBN}.
20935 @kindex set com1base
20936 @kindex set com1irq
20937 @kindex set com2base
20938 @kindex set com2irq
20939 @kindex set com3base
20940 @kindex set com3irq
20941 @kindex set com4base
20942 @kindex set com4irq
20943 @item set com1base @var{addr}
20944 This command sets the base I/O port address of the @file{COM1} serial
20947 @item set com1irq @var{irq}
20948 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
20949 for the @file{COM1} serial port.
20951 There are similar commands @samp{set com2base}, @samp{set com3irq},
20952 etc.@: for setting the port address and the @code{IRQ} lines for the
20955 @kindex show com1base
20956 @kindex show com1irq
20957 @kindex show com2base
20958 @kindex show com2irq
20959 @kindex show com3base
20960 @kindex show com3irq
20961 @kindex show com4base
20962 @kindex show com4irq
20963 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
20964 display the current settings of the base address and the @code{IRQ}
20965 lines used by the COM ports.
20968 @kindex info serial
20969 @cindex DOS serial port status
20970 This command prints the status of the 4 DOS serial ports. For each
20971 port, it prints whether it's active or not, its I/O base address and
20972 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
20973 counts of various errors encountered so far.
20977 @node Cygwin Native
20978 @subsection Features for Debugging MS Windows PE Executables
20979 @cindex MS Windows debugging
20980 @cindex native Cygwin debugging
20981 @cindex Cygwin-specific commands
20983 @value{GDBN} supports native debugging of MS Windows programs, including
20984 DLLs with and without symbolic debugging information.
20986 @cindex Ctrl-BREAK, MS-Windows
20987 @cindex interrupt debuggee on MS-Windows
20988 MS-Windows programs that call @code{SetConsoleMode} to switch off the
20989 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
20990 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
20991 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
20992 sequence, which can be used to interrupt the debuggee even if it
20995 There are various additional Cygwin-specific commands, described in
20996 this section. Working with DLLs that have no debugging symbols is
20997 described in @ref{Non-debug DLL Symbols}.
21002 This is a prefix of MS Windows-specific commands which print
21003 information about the target system and important OS structures.
21005 @item info w32 selector
21006 This command displays information returned by
21007 the Win32 API @code{GetThreadSelectorEntry} function.
21008 It takes an optional argument that is evaluated to
21009 a long value to give the information about this given selector.
21010 Without argument, this command displays information
21011 about the six segment registers.
21013 @item info w32 thread-information-block
21014 This command displays thread specific information stored in the
21015 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21016 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21018 @kindex set cygwin-exceptions
21019 @cindex debugging the Cygwin DLL
21020 @cindex Cygwin DLL, debugging
21021 @item set cygwin-exceptions @var{mode}
21022 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21023 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21024 @value{GDBN} will delay recognition of exceptions, and may ignore some
21025 exceptions which seem to be caused by internal Cygwin DLL
21026 ``bookkeeping''. This option is meant primarily for debugging the
21027 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21028 @value{GDBN} users with false @code{SIGSEGV} signals.
21030 @kindex show cygwin-exceptions
21031 @item show cygwin-exceptions
21032 Displays whether @value{GDBN} will break on exceptions that happen
21033 inside the Cygwin DLL itself.
21035 @kindex set new-console
21036 @item set new-console @var{mode}
21037 If @var{mode} is @code{on} the debuggee will
21038 be started in a new console on next start.
21039 If @var{mode} is @code{off}, the debuggee will
21040 be started in the same console as the debugger.
21042 @kindex show new-console
21043 @item show new-console
21044 Displays whether a new console is used
21045 when the debuggee is started.
21047 @kindex set new-group
21048 @item set new-group @var{mode}
21049 This boolean value controls whether the debuggee should
21050 start a new group or stay in the same group as the debugger.
21051 This affects the way the Windows OS handles
21054 @kindex show new-group
21055 @item show new-group
21056 Displays current value of new-group boolean.
21058 @kindex set debugevents
21059 @item set debugevents
21060 This boolean value adds debug output concerning kernel events related
21061 to the debuggee seen by the debugger. This includes events that
21062 signal thread and process creation and exit, DLL loading and
21063 unloading, console interrupts, and debugging messages produced by the
21064 Windows @code{OutputDebugString} API call.
21066 @kindex set debugexec
21067 @item set debugexec
21068 This boolean value adds debug output concerning execute events
21069 (such as resume thread) seen by the debugger.
21071 @kindex set debugexceptions
21072 @item set debugexceptions
21073 This boolean value adds debug output concerning exceptions in the
21074 debuggee seen by the debugger.
21076 @kindex set debugmemory
21077 @item set debugmemory
21078 This boolean value adds debug output concerning debuggee memory reads
21079 and writes by the debugger.
21083 This boolean values specifies whether the debuggee is called
21084 via a shell or directly (default value is on).
21088 Displays if the debuggee will be started with a shell.
21093 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21096 @node Non-debug DLL Symbols
21097 @subsubsection Support for DLLs without Debugging Symbols
21098 @cindex DLLs with no debugging symbols
21099 @cindex Minimal symbols and DLLs
21101 Very often on windows, some of the DLLs that your program relies on do
21102 not include symbolic debugging information (for example,
21103 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21104 symbols in a DLL, it relies on the minimal amount of symbolic
21105 information contained in the DLL's export table. This section
21106 describes working with such symbols, known internally to @value{GDBN} as
21107 ``minimal symbols''.
21109 Note that before the debugged program has started execution, no DLLs
21110 will have been loaded. The easiest way around this problem is simply to
21111 start the program --- either by setting a breakpoint or letting the
21112 program run once to completion.
21114 @subsubsection DLL Name Prefixes
21116 In keeping with the naming conventions used by the Microsoft debugging
21117 tools, DLL export symbols are made available with a prefix based on the
21118 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21119 also entered into the symbol table, so @code{CreateFileA} is often
21120 sufficient. In some cases there will be name clashes within a program
21121 (particularly if the executable itself includes full debugging symbols)
21122 necessitating the use of the fully qualified name when referring to the
21123 contents of the DLL. Use single-quotes around the name to avoid the
21124 exclamation mark (``!'') being interpreted as a language operator.
21126 Note that the internal name of the DLL may be all upper-case, even
21127 though the file name of the DLL is lower-case, or vice-versa. Since
21128 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21129 some confusion. If in doubt, try the @code{info functions} and
21130 @code{info variables} commands or even @code{maint print msymbols}
21131 (@pxref{Symbols}). Here's an example:
21134 (@value{GDBP}) info function CreateFileA
21135 All functions matching regular expression "CreateFileA":
21137 Non-debugging symbols:
21138 0x77e885f4 CreateFileA
21139 0x77e885f4 KERNEL32!CreateFileA
21143 (@value{GDBP}) info function !
21144 All functions matching regular expression "!":
21146 Non-debugging symbols:
21147 0x6100114c cygwin1!__assert
21148 0x61004034 cygwin1!_dll_crt0@@0
21149 0x61004240 cygwin1!dll_crt0(per_process *)
21153 @subsubsection Working with Minimal Symbols
21155 Symbols extracted from a DLL's export table do not contain very much
21156 type information. All that @value{GDBN} can do is guess whether a symbol
21157 refers to a function or variable depending on the linker section that
21158 contains the symbol. Also note that the actual contents of the memory
21159 contained in a DLL are not available unless the program is running. This
21160 means that you cannot examine the contents of a variable or disassemble
21161 a function within a DLL without a running program.
21163 Variables are generally treated as pointers and dereferenced
21164 automatically. For this reason, it is often necessary to prefix a
21165 variable name with the address-of operator (``&'') and provide explicit
21166 type information in the command. Here's an example of the type of
21170 (@value{GDBP}) print 'cygwin1!__argv'
21175 (@value{GDBP}) x 'cygwin1!__argv'
21176 0x10021610: "\230y\""
21179 And two possible solutions:
21182 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21183 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21187 (@value{GDBP}) x/2x &'cygwin1!__argv'
21188 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21189 (@value{GDBP}) x/x 0x10021608
21190 0x10021608: 0x0022fd98
21191 (@value{GDBP}) x/s 0x0022fd98
21192 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21195 Setting a break point within a DLL is possible even before the program
21196 starts execution. However, under these circumstances, @value{GDBN} can't
21197 examine the initial instructions of the function in order to skip the
21198 function's frame set-up code. You can work around this by using ``*&''
21199 to set the breakpoint at a raw memory address:
21202 (@value{GDBP}) break *&'python22!PyOS_Readline'
21203 Breakpoint 1 at 0x1e04eff0
21206 The author of these extensions is not entirely convinced that setting a
21207 break point within a shared DLL like @file{kernel32.dll} is completely
21211 @subsection Commands Specific to @sc{gnu} Hurd Systems
21212 @cindex @sc{gnu} Hurd debugging
21214 This subsection describes @value{GDBN} commands specific to the
21215 @sc{gnu} Hurd native debugging.
21220 @kindex set signals@r{, Hurd command}
21221 @kindex set sigs@r{, Hurd command}
21222 This command toggles the state of inferior signal interception by
21223 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21224 affected by this command. @code{sigs} is a shorthand alias for
21229 @kindex show signals@r{, Hurd command}
21230 @kindex show sigs@r{, Hurd command}
21231 Show the current state of intercepting inferior's signals.
21233 @item set signal-thread
21234 @itemx set sigthread
21235 @kindex set signal-thread
21236 @kindex set sigthread
21237 This command tells @value{GDBN} which thread is the @code{libc} signal
21238 thread. That thread is run when a signal is delivered to a running
21239 process. @code{set sigthread} is the shorthand alias of @code{set
21242 @item show signal-thread
21243 @itemx show sigthread
21244 @kindex show signal-thread
21245 @kindex show sigthread
21246 These two commands show which thread will run when the inferior is
21247 delivered a signal.
21250 @kindex set stopped@r{, Hurd command}
21251 This commands tells @value{GDBN} that the inferior process is stopped,
21252 as with the @code{SIGSTOP} signal. The stopped process can be
21253 continued by delivering a signal to it.
21256 @kindex show stopped@r{, Hurd command}
21257 This command shows whether @value{GDBN} thinks the debuggee is
21260 @item set exceptions
21261 @kindex set exceptions@r{, Hurd command}
21262 Use this command to turn off trapping of exceptions in the inferior.
21263 When exception trapping is off, neither breakpoints nor
21264 single-stepping will work. To restore the default, set exception
21267 @item show exceptions
21268 @kindex show exceptions@r{, Hurd command}
21269 Show the current state of trapping exceptions in the inferior.
21271 @item set task pause
21272 @kindex set task@r{, Hurd commands}
21273 @cindex task attributes (@sc{gnu} Hurd)
21274 @cindex pause current task (@sc{gnu} Hurd)
21275 This command toggles task suspension when @value{GDBN} has control.
21276 Setting it to on takes effect immediately, and the task is suspended
21277 whenever @value{GDBN} gets control. Setting it to off will take
21278 effect the next time the inferior is continued. If this option is set
21279 to off, you can use @code{set thread default pause on} or @code{set
21280 thread pause on} (see below) to pause individual threads.
21282 @item show task pause
21283 @kindex show task@r{, Hurd commands}
21284 Show the current state of task suspension.
21286 @item set task detach-suspend-count
21287 @cindex task suspend count
21288 @cindex detach from task, @sc{gnu} Hurd
21289 This command sets the suspend count the task will be left with when
21290 @value{GDBN} detaches from it.
21292 @item show task detach-suspend-count
21293 Show the suspend count the task will be left with when detaching.
21295 @item set task exception-port
21296 @itemx set task excp
21297 @cindex task exception port, @sc{gnu} Hurd
21298 This command sets the task exception port to which @value{GDBN} will
21299 forward exceptions. The argument should be the value of the @dfn{send
21300 rights} of the task. @code{set task excp} is a shorthand alias.
21302 @item set noninvasive
21303 @cindex noninvasive task options
21304 This command switches @value{GDBN} to a mode that is the least
21305 invasive as far as interfering with the inferior is concerned. This
21306 is the same as using @code{set task pause}, @code{set exceptions}, and
21307 @code{set signals} to values opposite to the defaults.
21309 @item info send-rights
21310 @itemx info receive-rights
21311 @itemx info port-rights
21312 @itemx info port-sets
21313 @itemx info dead-names
21316 @cindex send rights, @sc{gnu} Hurd
21317 @cindex receive rights, @sc{gnu} Hurd
21318 @cindex port rights, @sc{gnu} Hurd
21319 @cindex port sets, @sc{gnu} Hurd
21320 @cindex dead names, @sc{gnu} Hurd
21321 These commands display information about, respectively, send rights,
21322 receive rights, port rights, port sets, and dead names of a task.
21323 There are also shorthand aliases: @code{info ports} for @code{info
21324 port-rights} and @code{info psets} for @code{info port-sets}.
21326 @item set thread pause
21327 @kindex set thread@r{, Hurd command}
21328 @cindex thread properties, @sc{gnu} Hurd
21329 @cindex pause current thread (@sc{gnu} Hurd)
21330 This command toggles current thread suspension when @value{GDBN} has
21331 control. Setting it to on takes effect immediately, and the current
21332 thread is suspended whenever @value{GDBN} gets control. Setting it to
21333 off will take effect the next time the inferior is continued.
21334 Normally, this command has no effect, since when @value{GDBN} has
21335 control, the whole task is suspended. However, if you used @code{set
21336 task pause off} (see above), this command comes in handy to suspend
21337 only the current thread.
21339 @item show thread pause
21340 @kindex show thread@r{, Hurd command}
21341 This command shows the state of current thread suspension.
21343 @item set thread run
21344 This command sets whether the current thread is allowed to run.
21346 @item show thread run
21347 Show whether the current thread is allowed to run.
21349 @item set thread detach-suspend-count
21350 @cindex thread suspend count, @sc{gnu} Hurd
21351 @cindex detach from thread, @sc{gnu} Hurd
21352 This command sets the suspend count @value{GDBN} will leave on a
21353 thread when detaching. This number is relative to the suspend count
21354 found by @value{GDBN} when it notices the thread; use @code{set thread
21355 takeover-suspend-count} to force it to an absolute value.
21357 @item show thread detach-suspend-count
21358 Show the suspend count @value{GDBN} will leave on the thread when
21361 @item set thread exception-port
21362 @itemx set thread excp
21363 Set the thread exception port to which to forward exceptions. This
21364 overrides the port set by @code{set task exception-port} (see above).
21365 @code{set thread excp} is the shorthand alias.
21367 @item set thread takeover-suspend-count
21368 Normally, @value{GDBN}'s thread suspend counts are relative to the
21369 value @value{GDBN} finds when it notices each thread. This command
21370 changes the suspend counts to be absolute instead.
21372 @item set thread default
21373 @itemx show thread default
21374 @cindex thread default settings, @sc{gnu} Hurd
21375 Each of the above @code{set thread} commands has a @code{set thread
21376 default} counterpart (e.g., @code{set thread default pause}, @code{set
21377 thread default exception-port}, etc.). The @code{thread default}
21378 variety of commands sets the default thread properties for all
21379 threads; you can then change the properties of individual threads with
21380 the non-default commands.
21387 @value{GDBN} provides the following commands specific to the Darwin target:
21390 @item set debug darwin @var{num}
21391 @kindex set debug darwin
21392 When set to a non zero value, enables debugging messages specific to
21393 the Darwin support. Higher values produce more verbose output.
21395 @item show debug darwin
21396 @kindex show debug darwin
21397 Show the current state of Darwin messages.
21399 @item set debug mach-o @var{num}
21400 @kindex set debug mach-o
21401 When set to a non zero value, enables debugging messages while
21402 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21403 file format used on Darwin for object and executable files.) Higher
21404 values produce more verbose output. This is a command to diagnose
21405 problems internal to @value{GDBN} and should not be needed in normal
21408 @item show debug mach-o
21409 @kindex show debug mach-o
21410 Show the current state of Mach-O file messages.
21412 @item set mach-exceptions on
21413 @itemx set mach-exceptions off
21414 @kindex set mach-exceptions
21415 On Darwin, faults are first reported as a Mach exception and are then
21416 mapped to a Posix signal. Use this command to turn on trapping of
21417 Mach exceptions in the inferior. This might be sometimes useful to
21418 better understand the cause of a fault. The default is off.
21420 @item show mach-exceptions
21421 @kindex show mach-exceptions
21422 Show the current state of exceptions trapping.
21427 @section Embedded Operating Systems
21429 This section describes configurations involving the debugging of
21430 embedded operating systems that are available for several different
21433 @value{GDBN} includes the ability to debug programs running on
21434 various real-time operating systems.
21436 @node Embedded Processors
21437 @section Embedded Processors
21439 This section goes into details specific to particular embedded
21442 @cindex send command to simulator
21443 Whenever a specific embedded processor has a simulator, @value{GDBN}
21444 allows to send an arbitrary command to the simulator.
21447 @item sim @var{command}
21448 @kindex sim@r{, a command}
21449 Send an arbitrary @var{command} string to the simulator. Consult the
21450 documentation for the specific simulator in use for information about
21451 acceptable commands.
21457 * M32R/SDI:: Renesas M32R/SDI
21458 * M68K:: Motorola M68K
21459 * MicroBlaze:: Xilinx MicroBlaze
21460 * MIPS Embedded:: MIPS Embedded
21461 * PowerPC Embedded:: PowerPC Embedded
21464 * Super-H:: Renesas Super-H
21470 @value{GDBN} provides the following ARM-specific commands:
21473 @item set arm disassembler
21475 This commands selects from a list of disassembly styles. The
21476 @code{"std"} style is the standard style.
21478 @item show arm disassembler
21480 Show the current disassembly style.
21482 @item set arm apcs32
21483 @cindex ARM 32-bit mode
21484 This command toggles ARM operation mode between 32-bit and 26-bit.
21486 @item show arm apcs32
21487 Display the current usage of the ARM 32-bit mode.
21489 @item set arm fpu @var{fputype}
21490 This command sets the ARM floating-point unit (FPU) type. The
21491 argument @var{fputype} can be one of these:
21495 Determine the FPU type by querying the OS ABI.
21497 Software FPU, with mixed-endian doubles on little-endian ARM
21500 GCC-compiled FPA co-processor.
21502 Software FPU with pure-endian doubles.
21508 Show the current type of the FPU.
21511 This command forces @value{GDBN} to use the specified ABI.
21514 Show the currently used ABI.
21516 @item set arm fallback-mode (arm|thumb|auto)
21517 @value{GDBN} uses the symbol table, when available, to determine
21518 whether instructions are ARM or Thumb. This command controls
21519 @value{GDBN}'s default behavior when the symbol table is not
21520 available. The default is @samp{auto}, which causes @value{GDBN} to
21521 use the current execution mode (from the @code{T} bit in the @code{CPSR}
21524 @item show arm fallback-mode
21525 Show the current fallback instruction mode.
21527 @item set arm force-mode (arm|thumb|auto)
21528 This command overrides use of the symbol table to determine whether
21529 instructions are ARM or Thumb. The default is @samp{auto}, which
21530 causes @value{GDBN} to use the symbol table and then the setting
21531 of @samp{set arm fallback-mode}.
21533 @item show arm force-mode
21534 Show the current forced instruction mode.
21536 @item set debug arm
21537 Toggle whether to display ARM-specific debugging messages from the ARM
21538 target support subsystem.
21540 @item show debug arm
21541 Show whether ARM-specific debugging messages are enabled.
21545 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21546 The @value{GDBN} ARM simulator accepts the following optional arguments.
21549 @item --swi-support=@var{type}
21550 Tell the simulator which SWI interfaces to support. The argument
21551 @var{type} may be a comma separated list of the following values.
21552 The default value is @code{all}.
21565 @subsection Renesas M32R/SDI
21567 The following commands are available for M32R/SDI:
21572 @cindex reset SDI connection, M32R
21573 This command resets the SDI connection.
21577 This command shows the SDI connection status.
21580 @kindex debug_chaos
21581 @cindex M32R/Chaos debugging
21582 Instructs the remote that M32R/Chaos debugging is to be used.
21584 @item use_debug_dma
21585 @kindex use_debug_dma
21586 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21589 @kindex use_mon_code
21590 Instructs the remote to use the MON_CODE method of accessing memory.
21593 @kindex use_ib_break
21594 Instructs the remote to set breakpoints by IB break.
21596 @item use_dbt_break
21597 @kindex use_dbt_break
21598 Instructs the remote to set breakpoints by DBT.
21604 The Motorola m68k configuration includes ColdFire support.
21607 @subsection MicroBlaze
21608 @cindex Xilinx MicroBlaze
21609 @cindex XMD, Xilinx Microprocessor Debugger
21611 The MicroBlaze is a soft-core processor supported on various Xilinx
21612 FPGAs, such as Spartan or Virtex series. Boards with these processors
21613 usually have JTAG ports which connect to a host system running the Xilinx
21614 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21615 This host system is used to download the configuration bitstream to
21616 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21617 communicates with the target board using the JTAG interface and
21618 presents a @code{gdbserver} interface to the board. By default
21619 @code{xmd} uses port @code{1234}. (While it is possible to change
21620 this default port, it requires the use of undocumented @code{xmd}
21621 commands. Contact Xilinx support if you need to do this.)
21623 Use these GDB commands to connect to the MicroBlaze target processor.
21626 @item target remote :1234
21627 Use this command to connect to the target if you are running @value{GDBN}
21628 on the same system as @code{xmd}.
21630 @item target remote @var{xmd-host}:1234
21631 Use this command to connect to the target if it is connected to @code{xmd}
21632 running on a different system named @var{xmd-host}.
21635 Use this command to download a program to the MicroBlaze target.
21637 @item set debug microblaze @var{n}
21638 Enable MicroBlaze-specific debugging messages if non-zero.
21640 @item show debug microblaze @var{n}
21641 Show MicroBlaze-specific debugging level.
21644 @node MIPS Embedded
21645 @subsection @acronym{MIPS} Embedded
21647 @cindex @acronym{MIPS} boards
21648 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21649 @acronym{MIPS} board attached to a serial line. This is available when
21650 you configure @value{GDBN} with @samp{--target=mips-elf}.
21653 Use these @value{GDBN} commands to specify the connection to your target board:
21656 @item target mips @var{port}
21657 @kindex target mips @var{port}
21658 To run a program on the board, start up @code{@value{GDBP}} with the
21659 name of your program as the argument. To connect to the board, use the
21660 command @samp{target mips @var{port}}, where @var{port} is the name of
21661 the serial port connected to the board. If the program has not already
21662 been downloaded to the board, you may use the @code{load} command to
21663 download it. You can then use all the usual @value{GDBN} commands.
21665 For example, this sequence connects to the target board through a serial
21666 port, and loads and runs a program called @var{prog} through the
21670 host$ @value{GDBP} @var{prog}
21671 @value{GDBN} is free software and @dots{}
21672 (@value{GDBP}) target mips /dev/ttyb
21673 (@value{GDBP}) load @var{prog}
21677 @item target mips @var{hostname}:@var{portnumber}
21678 On some @value{GDBN} host configurations, you can specify a TCP
21679 connection (for instance, to a serial line managed by a terminal
21680 concentrator) instead of a serial port, using the syntax
21681 @samp{@var{hostname}:@var{portnumber}}.
21683 @item target pmon @var{port}
21684 @kindex target pmon @var{port}
21687 @item target ddb @var{port}
21688 @kindex target ddb @var{port}
21689 NEC's DDB variant of PMON for Vr4300.
21691 @item target lsi @var{port}
21692 @kindex target lsi @var{port}
21693 LSI variant of PMON.
21699 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21702 @item set mipsfpu double
21703 @itemx set mipsfpu single
21704 @itemx set mipsfpu none
21705 @itemx set mipsfpu auto
21706 @itemx show mipsfpu
21707 @kindex set mipsfpu
21708 @kindex show mipsfpu
21709 @cindex @acronym{MIPS} remote floating point
21710 @cindex floating point, @acronym{MIPS} remote
21711 If your target board does not support the @acronym{MIPS} floating point
21712 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21713 need this, you may wish to put the command in your @value{GDBN} init
21714 file). This tells @value{GDBN} how to find the return value of
21715 functions which return floating point values. It also allows
21716 @value{GDBN} to avoid saving the floating point registers when calling
21717 functions on the board. If you are using a floating point coprocessor
21718 with only single precision floating point support, as on the @sc{r4650}
21719 processor, use the command @samp{set mipsfpu single}. The default
21720 double precision floating point coprocessor may be selected using
21721 @samp{set mipsfpu double}.
21723 In previous versions the only choices were double precision or no
21724 floating point, so @samp{set mipsfpu on} will select double precision
21725 and @samp{set mipsfpu off} will select no floating point.
21727 As usual, you can inquire about the @code{mipsfpu} variable with
21728 @samp{show mipsfpu}.
21730 @item set timeout @var{seconds}
21731 @itemx set retransmit-timeout @var{seconds}
21732 @itemx show timeout
21733 @itemx show retransmit-timeout
21734 @cindex @code{timeout}, @acronym{MIPS} protocol
21735 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21736 @kindex set timeout
21737 @kindex show timeout
21738 @kindex set retransmit-timeout
21739 @kindex show retransmit-timeout
21740 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21741 remote protocol, with the @code{set timeout @var{seconds}} command. The
21742 default is 5 seconds. Similarly, you can control the timeout used while
21743 waiting for an acknowledgment of a packet with the @code{set
21744 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21745 You can inspect both values with @code{show timeout} and @code{show
21746 retransmit-timeout}. (These commands are @emph{only} available when
21747 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21749 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21750 is waiting for your program to stop. In that case, @value{GDBN} waits
21751 forever because it has no way of knowing how long the program is going
21752 to run before stopping.
21754 @item set syn-garbage-limit @var{num}
21755 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21756 @cindex synchronize with remote @acronym{MIPS} target
21757 Limit the maximum number of characters @value{GDBN} should ignore when
21758 it tries to synchronize with the remote target. The default is 10
21759 characters. Setting the limit to -1 means there's no limit.
21761 @item show syn-garbage-limit
21762 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21763 Show the current limit on the number of characters to ignore when
21764 trying to synchronize with the remote system.
21766 @item set monitor-prompt @var{prompt}
21767 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21768 @cindex remote monitor prompt
21769 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21770 remote monitor. The default depends on the target:
21780 @item show monitor-prompt
21781 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21782 Show the current strings @value{GDBN} expects as the prompt from the
21785 @item set monitor-warnings
21786 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21787 Enable or disable monitor warnings about hardware breakpoints. This
21788 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21789 display warning messages whose codes are returned by the @code{lsi}
21790 PMON monitor for breakpoint commands.
21792 @item show monitor-warnings
21793 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21794 Show the current setting of printing monitor warnings.
21796 @item pmon @var{command}
21797 @kindex pmon@r{, @acronym{MIPS} remote}
21798 @cindex send PMON command
21799 This command allows sending an arbitrary @var{command} string to the
21800 monitor. The monitor must be in debug mode for this to work.
21803 @node PowerPC Embedded
21804 @subsection PowerPC Embedded
21806 @cindex DVC register
21807 @value{GDBN} supports using the DVC (Data Value Compare) register to
21808 implement in hardware simple hardware watchpoint conditions of the form:
21811 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21812 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21815 The DVC register will be automatically used when @value{GDBN} detects
21816 such pattern in a condition expression, and the created watchpoint uses one
21817 debug register (either the @code{exact-watchpoints} option is on and the
21818 variable is scalar, or the variable has a length of one byte). This feature
21819 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21822 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21823 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21824 in which case watchpoints using only one debug register are created when
21825 watching variables of scalar types.
21827 You can create an artificial array to watch an arbitrary memory
21828 region using one of the following commands (@pxref{Expressions}):
21831 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21832 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21835 PowerPC embedded processors support masked watchpoints. See the discussion
21836 about the @code{mask} argument in @ref{Set Watchpoints}.
21838 @cindex ranged breakpoint
21839 PowerPC embedded processors support hardware accelerated
21840 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21841 the inferior whenever it executes an instruction at any address within
21842 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21843 use the @code{break-range} command.
21845 @value{GDBN} provides the following PowerPC-specific commands:
21848 @kindex break-range
21849 @item break-range @var{start-location}, @var{end-location}
21850 Set a breakpoint for an address range given by
21851 @var{start-location} and @var{end-location}, which can specify a function name,
21852 a line number, an offset of lines from the current line or from the start
21853 location, or an address of an instruction (see @ref{Specify Location},
21854 for a list of all the possible ways to specify a @var{location}.)
21855 The breakpoint will stop execution of the inferior whenever it
21856 executes an instruction at any address within the specified range,
21857 (including @var{start-location} and @var{end-location}.)
21859 @kindex set powerpc
21860 @item set powerpc soft-float
21861 @itemx show powerpc soft-float
21862 Force @value{GDBN} to use (or not use) a software floating point calling
21863 convention. By default, @value{GDBN} selects the calling convention based
21864 on the selected architecture and the provided executable file.
21866 @item set powerpc vector-abi
21867 @itemx show powerpc vector-abi
21868 Force @value{GDBN} to use the specified calling convention for vector
21869 arguments and return values. The valid options are @samp{auto};
21870 @samp{generic}, to avoid vector registers even if they are present;
21871 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21872 registers. By default, @value{GDBN} selects the calling convention
21873 based on the selected architecture and the provided executable file.
21875 @item set powerpc exact-watchpoints
21876 @itemx show powerpc exact-watchpoints
21877 Allow @value{GDBN} to use only one debug register when watching a variable
21878 of scalar type, thus assuming that the variable is accessed through the
21879 address of its first byte.
21884 @subsection Atmel AVR
21887 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21888 following AVR-specific commands:
21891 @item info io_registers
21892 @kindex info io_registers@r{, AVR}
21893 @cindex I/O registers (Atmel AVR)
21894 This command displays information about the AVR I/O registers. For
21895 each register, @value{GDBN} prints its number and value.
21902 When configured for debugging CRIS, @value{GDBN} provides the
21903 following CRIS-specific commands:
21906 @item set cris-version @var{ver}
21907 @cindex CRIS version
21908 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21909 The CRIS version affects register names and sizes. This command is useful in
21910 case autodetection of the CRIS version fails.
21912 @item show cris-version
21913 Show the current CRIS version.
21915 @item set cris-dwarf2-cfi
21916 @cindex DWARF-2 CFI and CRIS
21917 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21918 Change to @samp{off} when using @code{gcc-cris} whose version is below
21921 @item show cris-dwarf2-cfi
21922 Show the current state of using DWARF-2 CFI.
21924 @item set cris-mode @var{mode}
21926 Set the current CRIS mode to @var{mode}. It should only be changed when
21927 debugging in guru mode, in which case it should be set to
21928 @samp{guru} (the default is @samp{normal}).
21930 @item show cris-mode
21931 Show the current CRIS mode.
21935 @subsection Renesas Super-H
21938 For the Renesas Super-H processor, @value{GDBN} provides these
21942 @item set sh calling-convention @var{convention}
21943 @kindex set sh calling-convention
21944 Set the calling-convention used when calling functions from @value{GDBN}.
21945 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21946 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21947 convention. If the DWARF-2 information of the called function specifies
21948 that the function follows the Renesas calling convention, the function
21949 is called using the Renesas calling convention. If the calling convention
21950 is set to @samp{renesas}, the Renesas calling convention is always used,
21951 regardless of the DWARF-2 information. This can be used to override the
21952 default of @samp{gcc} if debug information is missing, or the compiler
21953 does not emit the DWARF-2 calling convention entry for a function.
21955 @item show sh calling-convention
21956 @kindex show sh calling-convention
21957 Show the current calling convention setting.
21962 @node Architectures
21963 @section Architectures
21965 This section describes characteristics of architectures that affect
21966 all uses of @value{GDBN} with the architecture, both native and cross.
21973 * HPPA:: HP PA architecture
21974 * SPU:: Cell Broadband Engine SPU architecture
21980 @subsection AArch64
21981 @cindex AArch64 support
21983 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21984 following special commands:
21987 @item set debug aarch64
21988 @kindex set debug aarch64
21989 This command determines whether AArch64 architecture-specific debugging
21990 messages are to be displayed.
21992 @item show debug aarch64
21993 Show whether AArch64 debugging messages are displayed.
21998 @subsection x86 Architecture-specific Issues
22001 @item set struct-convention @var{mode}
22002 @kindex set struct-convention
22003 @cindex struct return convention
22004 @cindex struct/union returned in registers
22005 Set the convention used by the inferior to return @code{struct}s and
22006 @code{union}s from functions to @var{mode}. Possible values of
22007 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22008 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22009 are returned on the stack, while @code{"reg"} means that a
22010 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22011 be returned in a register.
22013 @item show struct-convention
22014 @kindex show struct-convention
22015 Show the current setting of the convention to return @code{struct}s
22020 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
22021 @cindex Intel(R) Memory Protection Extensions (MPX).
22023 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22024 @footnote{The register named with capital letters represent the architecture
22025 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22026 which are the lower bound and upper bound. Bounds are effective addresses or
22027 memory locations. The upper bounds are architecturally represented in 1's
22028 complement form. A bound having lower bound = 0, and upper bound = 0
22029 (1's complement of all bits set) will allow access to the entire address space.
22031 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22032 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22033 display the upper bound performing the complement of one operation on the
22034 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22035 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22036 can also be noted that the upper bounds are inclusive.
22038 As an example, assume that the register BND0 holds bounds for a pointer having
22039 access allowed for the range between 0x32 and 0x71. The values present on
22040 bnd0raw and bnd registers are presented as follows:
22043 bnd0raw = @{0x32, 0xffffffff8e@}
22044 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22047 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22048 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22049 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22050 Python, the display includes the memory size, in bits, accessible to
22053 Bounds can also be stored in bounds tables, which are stored in
22054 application memory. These tables store bounds for pointers by specifying
22055 the bounds pointer's value along with its bounds. Evaluating and changing
22056 bounds located in bound tables is therefore interesting while investigating
22057 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22060 @item show mpx bound @var{pointer}
22061 @kindex show mpx bound
22062 Display bounds of the given @var{pointer}.
22064 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22065 @kindex set mpx bound
22066 Set the bounds of a pointer in the bound table.
22067 This command takes three parameters: @var{pointer} is the pointers
22068 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22069 for lower and upper bounds respectively.
22075 See the following section.
22078 @subsection @acronym{MIPS}
22080 @cindex stack on Alpha
22081 @cindex stack on @acronym{MIPS}
22082 @cindex Alpha stack
22083 @cindex @acronym{MIPS} stack
22084 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22085 sometimes requires @value{GDBN} to search backward in the object code to
22086 find the beginning of a function.
22088 @cindex response time, @acronym{MIPS} debugging
22089 To improve response time (especially for embedded applications, where
22090 @value{GDBN} may be restricted to a slow serial line for this search)
22091 you may want to limit the size of this search, using one of these
22095 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22096 @item set heuristic-fence-post @var{limit}
22097 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22098 search for the beginning of a function. A value of @var{0} (the
22099 default) means there is no limit. However, except for @var{0}, the
22100 larger the limit the more bytes @code{heuristic-fence-post} must search
22101 and therefore the longer it takes to run. You should only need to use
22102 this command when debugging a stripped executable.
22104 @item show heuristic-fence-post
22105 Display the current limit.
22109 These commands are available @emph{only} when @value{GDBN} is configured
22110 for debugging programs on Alpha or @acronym{MIPS} processors.
22112 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22116 @item set mips abi @var{arg}
22117 @kindex set mips abi
22118 @cindex set ABI for @acronym{MIPS}
22119 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22120 values of @var{arg} are:
22124 The default ABI associated with the current binary (this is the
22134 @item show mips abi
22135 @kindex show mips abi
22136 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22138 @item set mips compression @var{arg}
22139 @kindex set mips compression
22140 @cindex code compression, @acronym{MIPS}
22141 Tell @value{GDBN} which @acronym{MIPS} compressed
22142 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22143 inferior. @value{GDBN} uses this for code disassembly and other
22144 internal interpretation purposes. This setting is only referred to
22145 when no executable has been associated with the debugging session or
22146 the executable does not provide information about the encoding it uses.
22147 Otherwise this setting is automatically updated from information
22148 provided by the executable.
22150 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22151 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22152 executables containing @acronym{MIPS16} code frequently are not
22153 identified as such.
22155 This setting is ``sticky''; that is, it retains its value across
22156 debugging sessions until reset either explicitly with this command or
22157 implicitly from an executable.
22159 The compiler and/or assembler typically add symbol table annotations to
22160 identify functions compiled for the @acronym{MIPS16} or
22161 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22162 are present, @value{GDBN} uses them in preference to the global
22163 compressed @acronym{ISA} encoding setting.
22165 @item show mips compression
22166 @kindex show mips compression
22167 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22168 @value{GDBN} to debug the inferior.
22171 @itemx show mipsfpu
22172 @xref{MIPS Embedded, set mipsfpu}.
22174 @item set mips mask-address @var{arg}
22175 @kindex set mips mask-address
22176 @cindex @acronym{MIPS} addresses, masking
22177 This command determines whether the most-significant 32 bits of 64-bit
22178 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22179 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22180 setting, which lets @value{GDBN} determine the correct value.
22182 @item show mips mask-address
22183 @kindex show mips mask-address
22184 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22187 @item set remote-mips64-transfers-32bit-regs
22188 @kindex set remote-mips64-transfers-32bit-regs
22189 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22190 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22191 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22192 and 64 bits for other registers, set this option to @samp{on}.
22194 @item show remote-mips64-transfers-32bit-regs
22195 @kindex show remote-mips64-transfers-32bit-regs
22196 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22198 @item set debug mips
22199 @kindex set debug mips
22200 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22201 target code in @value{GDBN}.
22203 @item show debug mips
22204 @kindex show debug mips
22205 Show the current setting of @acronym{MIPS} debugging messages.
22211 @cindex HPPA support
22213 When @value{GDBN} is debugging the HP PA architecture, it provides the
22214 following special commands:
22217 @item set debug hppa
22218 @kindex set debug hppa
22219 This command determines whether HPPA architecture-specific debugging
22220 messages are to be displayed.
22222 @item show debug hppa
22223 Show whether HPPA debugging messages are displayed.
22225 @item maint print unwind @var{address}
22226 @kindex maint print unwind@r{, HPPA}
22227 This command displays the contents of the unwind table entry at the
22228 given @var{address}.
22234 @subsection Cell Broadband Engine SPU architecture
22235 @cindex Cell Broadband Engine
22238 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22239 it provides the following special commands:
22242 @item info spu event
22244 Display SPU event facility status. Shows current event mask
22245 and pending event status.
22247 @item info spu signal
22248 Display SPU signal notification facility status. Shows pending
22249 signal-control word and signal notification mode of both signal
22250 notification channels.
22252 @item info spu mailbox
22253 Display SPU mailbox facility status. Shows all pending entries,
22254 in order of processing, in each of the SPU Write Outbound,
22255 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22258 Display MFC DMA status. Shows all pending commands in the MFC
22259 DMA queue. For each entry, opcode, tag, class IDs, effective
22260 and local store addresses and transfer size are shown.
22262 @item info spu proxydma
22263 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22264 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22265 and local store addresses and transfer size are shown.
22269 When @value{GDBN} is debugging a combined PowerPC/SPU application
22270 on the Cell Broadband Engine, it provides in addition the following
22274 @item set spu stop-on-load @var{arg}
22276 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22277 will give control to the user when a new SPE thread enters its @code{main}
22278 function. The default is @code{off}.
22280 @item show spu stop-on-load
22282 Show whether to stop for new SPE threads.
22284 @item set spu auto-flush-cache @var{arg}
22285 Set whether to automatically flush the software-managed cache. When set to
22286 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22287 cache to be flushed whenever SPE execution stops. This provides a consistent
22288 view of PowerPC memory that is accessed via the cache. If an application
22289 does not use the software-managed cache, this option has no effect.
22291 @item show spu auto-flush-cache
22292 Show whether to automatically flush the software-managed cache.
22297 @subsection PowerPC
22298 @cindex PowerPC architecture
22300 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22301 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22302 numbers stored in the floating point registers. These values must be stored
22303 in two consecutive registers, always starting at an even register like
22304 @code{f0} or @code{f2}.
22306 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22307 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22308 @code{f2} and @code{f3} for @code{$dl1} and so on.
22310 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22311 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22314 @subsection Nios II
22315 @cindex Nios II architecture
22317 When @value{GDBN} is debugging the Nios II architecture,
22318 it provides the following special commands:
22322 @item set debug nios2
22323 @kindex set debug nios2
22324 This command turns on and off debugging messages for the Nios II
22325 target code in @value{GDBN}.
22327 @item show debug nios2
22328 @kindex show debug nios2
22329 Show the current setting of Nios II debugging messages.
22332 @node Controlling GDB
22333 @chapter Controlling @value{GDBN}
22335 You can alter the way @value{GDBN} interacts with you by using the
22336 @code{set} command. For commands controlling how @value{GDBN} displays
22337 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22342 * Editing:: Command editing
22343 * Command History:: Command history
22344 * Screen Size:: Screen size
22345 * Numbers:: Numbers
22346 * ABI:: Configuring the current ABI
22347 * Auto-loading:: Automatically loading associated files
22348 * Messages/Warnings:: Optional warnings and messages
22349 * Debugging Output:: Optional messages about internal happenings
22350 * Other Misc Settings:: Other Miscellaneous Settings
22358 @value{GDBN} indicates its readiness to read a command by printing a string
22359 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22360 can change the prompt string with the @code{set prompt} command. For
22361 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22362 the prompt in one of the @value{GDBN} sessions so that you can always tell
22363 which one you are talking to.
22365 @emph{Note:} @code{set prompt} does not add a space for you after the
22366 prompt you set. This allows you to set a prompt which ends in a space
22367 or a prompt that does not.
22371 @item set prompt @var{newprompt}
22372 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22374 @kindex show prompt
22376 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22379 Versions of @value{GDBN} that ship with Python scripting enabled have
22380 prompt extensions. The commands for interacting with these extensions
22384 @kindex set extended-prompt
22385 @item set extended-prompt @var{prompt}
22386 Set an extended prompt that allows for substitutions.
22387 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22388 substitution. Any escape sequences specified as part of the prompt
22389 string are replaced with the corresponding strings each time the prompt
22395 set extended-prompt Current working directory: \w (gdb)
22398 Note that when an extended-prompt is set, it takes control of the
22399 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22401 @kindex show extended-prompt
22402 @item show extended-prompt
22403 Prints the extended prompt. Any escape sequences specified as part of
22404 the prompt string with @code{set extended-prompt}, are replaced with the
22405 corresponding strings each time the prompt is displayed.
22409 @section Command Editing
22411 @cindex command line editing
22413 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22414 @sc{gnu} library provides consistent behavior for programs which provide a
22415 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22416 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22417 substitution, and a storage and recall of command history across
22418 debugging sessions.
22420 You may control the behavior of command line editing in @value{GDBN} with the
22421 command @code{set}.
22424 @kindex set editing
22427 @itemx set editing on
22428 Enable command line editing (enabled by default).
22430 @item set editing off
22431 Disable command line editing.
22433 @kindex show editing
22435 Show whether command line editing is enabled.
22438 @ifset SYSTEM_READLINE
22439 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22441 @ifclear SYSTEM_READLINE
22442 @xref{Command Line Editing},
22444 for more details about the Readline
22445 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22446 encouraged to read that chapter.
22448 @node Command History
22449 @section Command History
22450 @cindex command history
22452 @value{GDBN} can keep track of the commands you type during your
22453 debugging sessions, so that you can be certain of precisely what
22454 happened. Use these commands to manage the @value{GDBN} command
22457 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22458 package, to provide the history facility.
22459 @ifset SYSTEM_READLINE
22460 @xref{Using History Interactively, , , history, GNU History Library},
22462 @ifclear SYSTEM_READLINE
22463 @xref{Using History Interactively},
22465 for the detailed description of the History library.
22467 To issue a command to @value{GDBN} without affecting certain aspects of
22468 the state which is seen by users, prefix it with @samp{server }
22469 (@pxref{Server Prefix}). This
22470 means that this command will not affect the command history, nor will it
22471 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22472 pressed on a line by itself.
22474 @cindex @code{server}, command prefix
22475 The server prefix does not affect the recording of values into the value
22476 history; to print a value without recording it into the value history,
22477 use the @code{output} command instead of the @code{print} command.
22479 Here is the description of @value{GDBN} commands related to command
22483 @cindex history substitution
22484 @cindex history file
22485 @kindex set history filename
22486 @cindex @env{GDBHISTFILE}, environment variable
22487 @item set history filename @var{fname}
22488 Set the name of the @value{GDBN} command history file to @var{fname}.
22489 This is the file where @value{GDBN} reads an initial command history
22490 list, and where it writes the command history from this session when it
22491 exits. You can access this list through history expansion or through
22492 the history command editing characters listed below. This file defaults
22493 to the value of the environment variable @code{GDBHISTFILE}, or to
22494 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22497 @cindex save command history
22498 @kindex set history save
22499 @item set history save
22500 @itemx set history save on
22501 Record command history in a file, whose name may be specified with the
22502 @code{set history filename} command. By default, this option is disabled.
22504 @item set history save off
22505 Stop recording command history in a file.
22507 @cindex history size
22508 @kindex set history size
22509 @cindex @env{GDBHISTSIZE}, environment variable
22510 @item set history size @var{size}
22511 @itemx set history size unlimited
22512 Set the number of commands which @value{GDBN} keeps in its history list.
22513 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
22514 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
22515 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
22516 either a negative number or the empty string, then the number of commands
22517 @value{GDBN} keeps in the history list is unlimited.
22519 @cindex remove duplicate history
22520 @kindex set history remove-duplicates
22521 @item set history remove-duplicates @var{count}
22522 @itemx set history remove-duplicates unlimited
22523 Control the removal of duplicate history entries in the command history list.
22524 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
22525 history entries and remove the first entry that is a duplicate of the current
22526 entry being added to the command history list. If @var{count} is
22527 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
22528 removal of duplicate history entries is disabled.
22530 Only history entries added during the current session are considered for
22531 removal. This option is set to 0 by default.
22535 History expansion assigns special meaning to the character @kbd{!}.
22536 @ifset SYSTEM_READLINE
22537 @xref{Event Designators, , , history, GNU History Library},
22539 @ifclear SYSTEM_READLINE
22540 @xref{Event Designators},
22544 @cindex history expansion, turn on/off
22545 Since @kbd{!} is also the logical not operator in C, history expansion
22546 is off by default. If you decide to enable history expansion with the
22547 @code{set history expansion on} command, you may sometimes need to
22548 follow @kbd{!} (when it is used as logical not, in an expression) with
22549 a space or a tab to prevent it from being expanded. The readline
22550 history facilities do not attempt substitution on the strings
22551 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22553 The commands to control history expansion are:
22556 @item set history expansion on
22557 @itemx set history expansion
22558 @kindex set history expansion
22559 Enable history expansion. History expansion is off by default.
22561 @item set history expansion off
22562 Disable history expansion.
22565 @kindex show history
22567 @itemx show history filename
22568 @itemx show history save
22569 @itemx show history size
22570 @itemx show history expansion
22571 These commands display the state of the @value{GDBN} history parameters.
22572 @code{show history} by itself displays all four states.
22577 @kindex show commands
22578 @cindex show last commands
22579 @cindex display command history
22580 @item show commands
22581 Display the last ten commands in the command history.
22583 @item show commands @var{n}
22584 Print ten commands centered on command number @var{n}.
22586 @item show commands +
22587 Print ten commands just after the commands last printed.
22591 @section Screen Size
22592 @cindex size of screen
22593 @cindex screen size
22596 @cindex pauses in output
22598 Certain commands to @value{GDBN} may produce large amounts of
22599 information output to the screen. To help you read all of it,
22600 @value{GDBN} pauses and asks you for input at the end of each page of
22601 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22602 to discard the remaining output. Also, the screen width setting
22603 determines when to wrap lines of output. Depending on what is being
22604 printed, @value{GDBN} tries to break the line at a readable place,
22605 rather than simply letting it overflow onto the following line.
22607 Normally @value{GDBN} knows the size of the screen from the terminal
22608 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22609 together with the value of the @code{TERM} environment variable and the
22610 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22611 you can override it with the @code{set height} and @code{set
22618 @kindex show height
22619 @item set height @var{lpp}
22620 @itemx set height unlimited
22622 @itemx set width @var{cpl}
22623 @itemx set width unlimited
22625 These @code{set} commands specify a screen height of @var{lpp} lines and
22626 a screen width of @var{cpl} characters. The associated @code{show}
22627 commands display the current settings.
22629 If you specify a height of either @code{unlimited} or zero lines,
22630 @value{GDBN} does not pause during output no matter how long the
22631 output is. This is useful if output is to a file or to an editor
22634 Likewise, you can specify @samp{set width unlimited} or @samp{set
22635 width 0} to prevent @value{GDBN} from wrapping its output.
22637 @item set pagination on
22638 @itemx set pagination off
22639 @kindex set pagination
22640 Turn the output pagination on or off; the default is on. Turning
22641 pagination off is the alternative to @code{set height unlimited}. Note that
22642 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22643 Options, -batch}) also automatically disables pagination.
22645 @item show pagination
22646 @kindex show pagination
22647 Show the current pagination mode.
22652 @cindex number representation
22653 @cindex entering numbers
22655 You can always enter numbers in octal, decimal, or hexadecimal in
22656 @value{GDBN} by the usual conventions: octal numbers begin with
22657 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22658 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22659 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22660 10; likewise, the default display for numbers---when no particular
22661 format is specified---is base 10. You can change the default base for
22662 both input and output with the commands described below.
22665 @kindex set input-radix
22666 @item set input-radix @var{base}
22667 Set the default base for numeric input. Supported choices
22668 for @var{base} are decimal 8, 10, or 16. The base must itself be
22669 specified either unambiguously or using the current input radix; for
22673 set input-radix 012
22674 set input-radix 10.
22675 set input-radix 0xa
22679 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22680 leaves the input radix unchanged, no matter what it was, since
22681 @samp{10}, being without any leading or trailing signs of its base, is
22682 interpreted in the current radix. Thus, if the current radix is 16,
22683 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22686 @kindex set output-radix
22687 @item set output-radix @var{base}
22688 Set the default base for numeric display. Supported choices
22689 for @var{base} are decimal 8, 10, or 16. The base must itself be
22690 specified either unambiguously or using the current input radix.
22692 @kindex show input-radix
22693 @item show input-radix
22694 Display the current default base for numeric input.
22696 @kindex show output-radix
22697 @item show output-radix
22698 Display the current default base for numeric display.
22700 @item set radix @r{[}@var{base}@r{]}
22704 These commands set and show the default base for both input and output
22705 of numbers. @code{set radix} sets the radix of input and output to
22706 the same base; without an argument, it resets the radix back to its
22707 default value of 10.
22712 @section Configuring the Current ABI
22714 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22715 application automatically. However, sometimes you need to override its
22716 conclusions. Use these commands to manage @value{GDBN}'s view of the
22722 @cindex Newlib OS ABI and its influence on the longjmp handling
22724 One @value{GDBN} configuration can debug binaries for multiple operating
22725 system targets, either via remote debugging or native emulation.
22726 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22727 but you can override its conclusion using the @code{set osabi} command.
22728 One example where this is useful is in debugging of binaries which use
22729 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22730 not have the same identifying marks that the standard C library for your
22733 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22734 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22735 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22736 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22740 Show the OS ABI currently in use.
22743 With no argument, show the list of registered available OS ABI's.
22745 @item set osabi @var{abi}
22746 Set the current OS ABI to @var{abi}.
22749 @cindex float promotion
22751 Generally, the way that an argument of type @code{float} is passed to a
22752 function depends on whether the function is prototyped. For a prototyped
22753 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22754 according to the architecture's convention for @code{float}. For unprototyped
22755 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22756 @code{double} and then passed.
22758 Unfortunately, some forms of debug information do not reliably indicate whether
22759 a function is prototyped. If @value{GDBN} calls a function that is not marked
22760 as prototyped, it consults @kbd{set coerce-float-to-double}.
22763 @kindex set coerce-float-to-double
22764 @item set coerce-float-to-double
22765 @itemx set coerce-float-to-double on
22766 Arguments of type @code{float} will be promoted to @code{double} when passed
22767 to an unprototyped function. This is the default setting.
22769 @item set coerce-float-to-double off
22770 Arguments of type @code{float} will be passed directly to unprototyped
22773 @kindex show coerce-float-to-double
22774 @item show coerce-float-to-double
22775 Show the current setting of promoting @code{float} to @code{double}.
22779 @kindex show cp-abi
22780 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22781 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22782 used to build your application. @value{GDBN} only fully supports
22783 programs with a single C@t{++} ABI; if your program contains code using
22784 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22785 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22786 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22787 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22788 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22789 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22794 Show the C@t{++} ABI currently in use.
22797 With no argument, show the list of supported C@t{++} ABI's.
22799 @item set cp-abi @var{abi}
22800 @itemx set cp-abi auto
22801 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22805 @section Automatically loading associated files
22806 @cindex auto-loading
22808 @value{GDBN} sometimes reads files with commands and settings automatically,
22809 without being explicitly told so by the user. We call this feature
22810 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22811 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22812 results or introduce security risks (e.g., if the file comes from untrusted
22816 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22817 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22819 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22820 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22823 There are various kinds of files @value{GDBN} can automatically load.
22824 In addition to these files, @value{GDBN} supports auto-loading code written
22825 in various extension languages. @xref{Auto-loading extensions}.
22827 Note that loading of these associated files (including the local @file{.gdbinit}
22828 file) requires accordingly configured @code{auto-load safe-path}
22829 (@pxref{Auto-loading safe path}).
22831 For these reasons, @value{GDBN} includes commands and options to let you
22832 control when to auto-load files and which files should be auto-loaded.
22835 @anchor{set auto-load off}
22836 @kindex set auto-load off
22837 @item set auto-load off
22838 Globally disable loading of all auto-loaded files.
22839 You may want to use this command with the @samp{-iex} option
22840 (@pxref{Option -init-eval-command}) such as:
22842 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22845 Be aware that system init file (@pxref{System-wide configuration})
22846 and init files from your home directory (@pxref{Home Directory Init File})
22847 still get read (as they come from generally trusted directories).
22848 To prevent @value{GDBN} from auto-loading even those init files, use the
22849 @option{-nx} option (@pxref{Mode Options}), in addition to
22850 @code{set auto-load no}.
22852 @anchor{show auto-load}
22853 @kindex show auto-load
22854 @item show auto-load
22855 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22859 (gdb) show auto-load
22860 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22861 libthread-db: Auto-loading of inferior specific libthread_db is on.
22862 local-gdbinit: Auto-loading of .gdbinit script from current directory
22864 python-scripts: Auto-loading of Python scripts is on.
22865 safe-path: List of directories from which it is safe to auto-load files
22866 is $debugdir:$datadir/auto-load.
22867 scripts-directory: List of directories from which to load auto-loaded scripts
22868 is $debugdir:$datadir/auto-load.
22871 @anchor{info auto-load}
22872 @kindex info auto-load
22873 @item info auto-load
22874 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22878 (gdb) info auto-load
22881 Yes /home/user/gdb/gdb-gdb.gdb
22882 libthread-db: No auto-loaded libthread-db.
22883 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22887 Yes /home/user/gdb/gdb-gdb.py
22891 These are @value{GDBN} control commands for the auto-loading:
22893 @multitable @columnfractions .5 .5
22894 @item @xref{set auto-load off}.
22895 @tab Disable auto-loading globally.
22896 @item @xref{show auto-load}.
22897 @tab Show setting of all kinds of files.
22898 @item @xref{info auto-load}.
22899 @tab Show state of all kinds of files.
22900 @item @xref{set auto-load gdb-scripts}.
22901 @tab Control for @value{GDBN} command scripts.
22902 @item @xref{show auto-load gdb-scripts}.
22903 @tab Show setting of @value{GDBN} command scripts.
22904 @item @xref{info auto-load gdb-scripts}.
22905 @tab Show state of @value{GDBN} command scripts.
22906 @item @xref{set auto-load python-scripts}.
22907 @tab Control for @value{GDBN} Python scripts.
22908 @item @xref{show auto-load python-scripts}.
22909 @tab Show setting of @value{GDBN} Python scripts.
22910 @item @xref{info auto-load python-scripts}.
22911 @tab Show state of @value{GDBN} Python scripts.
22912 @item @xref{set auto-load guile-scripts}.
22913 @tab Control for @value{GDBN} Guile scripts.
22914 @item @xref{show auto-load guile-scripts}.
22915 @tab Show setting of @value{GDBN} Guile scripts.
22916 @item @xref{info auto-load guile-scripts}.
22917 @tab Show state of @value{GDBN} Guile scripts.
22918 @item @xref{set auto-load scripts-directory}.
22919 @tab Control for @value{GDBN} auto-loaded scripts location.
22920 @item @xref{show auto-load scripts-directory}.
22921 @tab Show @value{GDBN} auto-loaded scripts location.
22922 @item @xref{add-auto-load-scripts-directory}.
22923 @tab Add directory for auto-loaded scripts location list.
22924 @item @xref{set auto-load local-gdbinit}.
22925 @tab Control for init file in the current directory.
22926 @item @xref{show auto-load local-gdbinit}.
22927 @tab Show setting of init file in the current directory.
22928 @item @xref{info auto-load local-gdbinit}.
22929 @tab Show state of init file in the current directory.
22930 @item @xref{set auto-load libthread-db}.
22931 @tab Control for thread debugging library.
22932 @item @xref{show auto-load libthread-db}.
22933 @tab Show setting of thread debugging library.
22934 @item @xref{info auto-load libthread-db}.
22935 @tab Show state of thread debugging library.
22936 @item @xref{set auto-load safe-path}.
22937 @tab Control directories trusted for automatic loading.
22938 @item @xref{show auto-load safe-path}.
22939 @tab Show directories trusted for automatic loading.
22940 @item @xref{add-auto-load-safe-path}.
22941 @tab Add directory trusted for automatic loading.
22944 @node Init File in the Current Directory
22945 @subsection Automatically loading init file in the current directory
22946 @cindex auto-loading init file in the current directory
22948 By default, @value{GDBN} reads and executes the canned sequences of commands
22949 from init file (if any) in the current working directory,
22950 see @ref{Init File in the Current Directory during Startup}.
22952 Note that loading of this local @file{.gdbinit} file also requires accordingly
22953 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22956 @anchor{set auto-load local-gdbinit}
22957 @kindex set auto-load local-gdbinit
22958 @item set auto-load local-gdbinit [on|off]
22959 Enable or disable the auto-loading of canned sequences of commands
22960 (@pxref{Sequences}) found in init file in the current directory.
22962 @anchor{show auto-load local-gdbinit}
22963 @kindex show auto-load local-gdbinit
22964 @item show auto-load local-gdbinit
22965 Show whether auto-loading of canned sequences of commands from init file in the
22966 current directory is enabled or disabled.
22968 @anchor{info auto-load local-gdbinit}
22969 @kindex info auto-load local-gdbinit
22970 @item info auto-load local-gdbinit
22971 Print whether canned sequences of commands from init file in the
22972 current directory have been auto-loaded.
22975 @node libthread_db.so.1 file
22976 @subsection Automatically loading thread debugging library
22977 @cindex auto-loading libthread_db.so.1
22979 This feature is currently present only on @sc{gnu}/Linux native hosts.
22981 @value{GDBN} reads in some cases thread debugging library from places specific
22982 to the inferior (@pxref{set libthread-db-search-path}).
22984 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22985 without checking this @samp{set auto-load libthread-db} switch as system
22986 libraries have to be trusted in general. In all other cases of
22987 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22988 auto-load libthread-db} is enabled before trying to open such thread debugging
22991 Note that loading of this debugging library also requires accordingly configured
22992 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22995 @anchor{set auto-load libthread-db}
22996 @kindex set auto-load libthread-db
22997 @item set auto-load libthread-db [on|off]
22998 Enable or disable the auto-loading of inferior specific thread debugging library.
23000 @anchor{show auto-load libthread-db}
23001 @kindex show auto-load libthread-db
23002 @item show auto-load libthread-db
23003 Show whether auto-loading of inferior specific thread debugging library is
23004 enabled or disabled.
23006 @anchor{info auto-load libthread-db}
23007 @kindex info auto-load libthread-db
23008 @item info auto-load libthread-db
23009 Print the list of all loaded inferior specific thread debugging libraries and
23010 for each such library print list of inferior @var{pid}s using it.
23013 @node Auto-loading safe path
23014 @subsection Security restriction for auto-loading
23015 @cindex auto-loading safe-path
23017 As the files of inferior can come from untrusted source (such as submitted by
23018 an application user) @value{GDBN} does not always load any files automatically.
23019 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23020 directories trusted for loading files not explicitly requested by user.
23021 Each directory can also be a shell wildcard pattern.
23023 If the path is not set properly you will see a warning and the file will not
23028 Reading symbols from /home/user/gdb/gdb...done.
23029 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23030 declined by your `auto-load safe-path' set
23031 to "$debugdir:$datadir/auto-load".
23032 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23033 declined by your `auto-load safe-path' set
23034 to "$debugdir:$datadir/auto-load".
23038 To instruct @value{GDBN} to go ahead and use the init files anyway,
23039 invoke @value{GDBN} like this:
23042 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23045 The list of trusted directories is controlled by the following commands:
23048 @anchor{set auto-load safe-path}
23049 @kindex set auto-load safe-path
23050 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23051 Set the list of directories (and their subdirectories) trusted for automatic
23052 loading and execution of scripts. You can also enter a specific trusted file.
23053 Each directory can also be a shell wildcard pattern; wildcards do not match
23054 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23055 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23056 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23057 its default value as specified during @value{GDBN} compilation.
23059 The list of directories uses path separator (@samp{:} on GNU and Unix
23060 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23061 to the @env{PATH} environment variable.
23063 @anchor{show auto-load safe-path}
23064 @kindex show auto-load safe-path
23065 @item show auto-load safe-path
23066 Show the list of directories trusted for automatic loading and execution of
23069 @anchor{add-auto-load-safe-path}
23070 @kindex add-auto-load-safe-path
23071 @item add-auto-load-safe-path
23072 Add an entry (or list of entries) to the list of directories trusted for
23073 automatic loading and execution of scripts. Multiple entries may be delimited
23074 by the host platform path separator in use.
23077 This variable defaults to what @code{--with-auto-load-dir} has been configured
23078 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23079 substitution applies the same as for @ref{set auto-load scripts-directory}.
23080 The default @code{set auto-load safe-path} value can be also overriden by
23081 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23083 Setting this variable to @file{/} disables this security protection,
23084 corresponding @value{GDBN} configuration option is
23085 @option{--without-auto-load-safe-path}.
23086 This variable is supposed to be set to the system directories writable by the
23087 system superuser only. Users can add their source directories in init files in
23088 their home directories (@pxref{Home Directory Init File}). See also deprecated
23089 init file in the current directory
23090 (@pxref{Init File in the Current Directory during Startup}).
23092 To force @value{GDBN} to load the files it declined to load in the previous
23093 example, you could use one of the following ways:
23096 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23097 Specify this trusted directory (or a file) as additional component of the list.
23098 You have to specify also any existing directories displayed by
23099 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23101 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23102 Specify this directory as in the previous case but just for a single
23103 @value{GDBN} session.
23105 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23106 Disable auto-loading safety for a single @value{GDBN} session.
23107 This assumes all the files you debug during this @value{GDBN} session will come
23108 from trusted sources.
23110 @item @kbd{./configure --without-auto-load-safe-path}
23111 During compilation of @value{GDBN} you may disable any auto-loading safety.
23112 This assumes all the files you will ever debug with this @value{GDBN} come from
23116 On the other hand you can also explicitly forbid automatic files loading which
23117 also suppresses any such warning messages:
23120 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23121 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23123 @item @file{~/.gdbinit}: @samp{set auto-load no}
23124 Disable auto-loading globally for the user
23125 (@pxref{Home Directory Init File}). While it is improbable, you could also
23126 use system init file instead (@pxref{System-wide configuration}).
23129 This setting applies to the file names as entered by user. If no entry matches
23130 @value{GDBN} tries as a last resort to also resolve all the file names into
23131 their canonical form (typically resolving symbolic links) and compare the
23132 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23133 own before starting the comparison so a canonical form of directories is
23134 recommended to be entered.
23136 @node Auto-loading verbose mode
23137 @subsection Displaying files tried for auto-load
23138 @cindex auto-loading verbose mode
23140 For better visibility of all the file locations where you can place scripts to
23141 be auto-loaded with inferior --- or to protect yourself against accidental
23142 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23143 all the files attempted to be loaded. Both existing and non-existing files may
23146 For example the list of directories from which it is safe to auto-load files
23147 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23148 may not be too obvious while setting it up.
23151 (gdb) set debug auto-load on
23152 (gdb) file ~/src/t/true
23153 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23154 for objfile "/tmp/true".
23155 auto-load: Updating directories of "/usr:/opt".
23156 auto-load: Using directory "/usr".
23157 auto-load: Using directory "/opt".
23158 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23159 by your `auto-load safe-path' set to "/usr:/opt".
23163 @anchor{set debug auto-load}
23164 @kindex set debug auto-load
23165 @item set debug auto-load [on|off]
23166 Set whether to print the filenames attempted to be auto-loaded.
23168 @anchor{show debug auto-load}
23169 @kindex show debug auto-load
23170 @item show debug auto-load
23171 Show whether printing of the filenames attempted to be auto-loaded is turned
23175 @node Messages/Warnings
23176 @section Optional Warnings and Messages
23178 @cindex verbose operation
23179 @cindex optional warnings
23180 By default, @value{GDBN} is silent about its inner workings. If you are
23181 running on a slow machine, you may want to use the @code{set verbose}
23182 command. This makes @value{GDBN} tell you when it does a lengthy
23183 internal operation, so you will not think it has crashed.
23185 Currently, the messages controlled by @code{set verbose} are those
23186 which announce that the symbol table for a source file is being read;
23187 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23190 @kindex set verbose
23191 @item set verbose on
23192 Enables @value{GDBN} output of certain informational messages.
23194 @item set verbose off
23195 Disables @value{GDBN} output of certain informational messages.
23197 @kindex show verbose
23199 Displays whether @code{set verbose} is on or off.
23202 By default, if @value{GDBN} encounters bugs in the symbol table of an
23203 object file, it is silent; but if you are debugging a compiler, you may
23204 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23209 @kindex set complaints
23210 @item set complaints @var{limit}
23211 Permits @value{GDBN} to output @var{limit} complaints about each type of
23212 unusual symbols before becoming silent about the problem. Set
23213 @var{limit} to zero to suppress all complaints; set it to a large number
23214 to prevent complaints from being suppressed.
23216 @kindex show complaints
23217 @item show complaints
23218 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23222 @anchor{confirmation requests}
23223 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23224 lot of stupid questions to confirm certain commands. For example, if
23225 you try to run a program which is already running:
23229 The program being debugged has been started already.
23230 Start it from the beginning? (y or n)
23233 If you are willing to unflinchingly face the consequences of your own
23234 commands, you can disable this ``feature'':
23238 @kindex set confirm
23240 @cindex confirmation
23241 @cindex stupid questions
23242 @item set confirm off
23243 Disables confirmation requests. Note that running @value{GDBN} with
23244 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23245 automatically disables confirmation requests.
23247 @item set confirm on
23248 Enables confirmation requests (the default).
23250 @kindex show confirm
23252 Displays state of confirmation requests.
23256 @cindex command tracing
23257 If you need to debug user-defined commands or sourced files you may find it
23258 useful to enable @dfn{command tracing}. In this mode each command will be
23259 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23260 quantity denoting the call depth of each command.
23263 @kindex set trace-commands
23264 @cindex command scripts, debugging
23265 @item set trace-commands on
23266 Enable command tracing.
23267 @item set trace-commands off
23268 Disable command tracing.
23269 @item show trace-commands
23270 Display the current state of command tracing.
23273 @node Debugging Output
23274 @section Optional Messages about Internal Happenings
23275 @cindex optional debugging messages
23277 @value{GDBN} has commands that enable optional debugging messages from
23278 various @value{GDBN} subsystems; normally these commands are of
23279 interest to @value{GDBN} maintainers, or when reporting a bug. This
23280 section documents those commands.
23283 @kindex set exec-done-display
23284 @item set exec-done-display
23285 Turns on or off the notification of asynchronous commands'
23286 completion. When on, @value{GDBN} will print a message when an
23287 asynchronous command finishes its execution. The default is off.
23288 @kindex show exec-done-display
23289 @item show exec-done-display
23290 Displays the current setting of asynchronous command completion
23293 @cindex ARM AArch64
23294 @item set debug aarch64
23295 Turns on or off display of debugging messages related to ARM AArch64.
23296 The default is off.
23298 @item show debug aarch64
23299 Displays the current state of displaying debugging messages related to
23301 @cindex gdbarch debugging info
23302 @cindex architecture debugging info
23303 @item set debug arch
23304 Turns on or off display of gdbarch debugging info. The default is off
23305 @item show debug arch
23306 Displays the current state of displaying gdbarch debugging info.
23307 @item set debug aix-solib
23308 @cindex AIX shared library debugging
23309 Control display of debugging messages from the AIX shared library
23310 support module. The default is off.
23311 @item show debug aix-thread
23312 Show the current state of displaying AIX shared library debugging messages.
23313 @item set debug aix-thread
23314 @cindex AIX threads
23315 Display debugging messages about inner workings of the AIX thread
23317 @item show debug aix-thread
23318 Show the current state of AIX thread debugging info display.
23319 @item set debug check-physname
23321 Check the results of the ``physname'' computation. When reading DWARF
23322 debugging information for C@t{++}, @value{GDBN} attempts to compute
23323 each entity's name. @value{GDBN} can do this computation in two
23324 different ways, depending on exactly what information is present.
23325 When enabled, this setting causes @value{GDBN} to compute the names
23326 both ways and display any discrepancies.
23327 @item show debug check-physname
23328 Show the current state of ``physname'' checking.
23329 @item set debug coff-pe-read
23330 @cindex COFF/PE exported symbols
23331 Control display of debugging messages related to reading of COFF/PE
23332 exported symbols. The default is off.
23333 @item show debug coff-pe-read
23334 Displays the current state of displaying debugging messages related to
23335 reading of COFF/PE exported symbols.
23336 @item set debug dwarf-die
23338 Dump DWARF DIEs after they are read in.
23339 The value is the number of nesting levels to print.
23340 A value of zero turns off the display.
23341 @item show debug dwarf-die
23342 Show the current state of DWARF DIE debugging.
23343 @item set debug dwarf-line
23344 @cindex DWARF Line Tables
23345 Turns on or off display of debugging messages related to reading
23346 DWARF line tables. The default is 0 (off).
23347 A value of 1 provides basic information.
23348 A value greater than 1 provides more verbose information.
23349 @item show debug dwarf-line
23350 Show the current state of DWARF line table debugging.
23351 @item set debug dwarf-read
23352 @cindex DWARF Reading
23353 Turns on or off display of debugging messages related to reading
23354 DWARF debug info. The default is 0 (off).
23355 A value of 1 provides basic information.
23356 A value greater than 1 provides more verbose information.
23357 @item show debug dwarf-read
23358 Show the current state of DWARF reader debugging.
23359 @item set debug displaced
23360 @cindex displaced stepping debugging info
23361 Turns on or off display of @value{GDBN} debugging info for the
23362 displaced stepping support. The default is off.
23363 @item show debug displaced
23364 Displays the current state of displaying @value{GDBN} debugging info
23365 related to displaced stepping.
23366 @item set debug event
23367 @cindex event debugging info
23368 Turns on or off display of @value{GDBN} event debugging info. The
23370 @item show debug event
23371 Displays the current state of displaying @value{GDBN} event debugging
23373 @item set debug expression
23374 @cindex expression debugging info
23375 Turns on or off display of debugging info about @value{GDBN}
23376 expression parsing. The default is off.
23377 @item show debug expression
23378 Displays the current state of displaying debugging info about
23379 @value{GDBN} expression parsing.
23380 @item set debug frame
23381 @cindex frame debugging info
23382 Turns on or off display of @value{GDBN} frame debugging info. The
23384 @item show debug frame
23385 Displays the current state of displaying @value{GDBN} frame debugging
23387 @item set debug gnu-nat
23388 @cindex @sc{gnu}/Hurd debug messages
23389 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23390 @item show debug gnu-nat
23391 Show the current state of @sc{gnu}/Hurd debugging messages.
23392 @item set debug infrun
23393 @cindex inferior debugging info
23394 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23395 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23396 for implementing operations such as single-stepping the inferior.
23397 @item show debug infrun
23398 Displays the current state of @value{GDBN} inferior debugging.
23399 @item set debug jit
23400 @cindex just-in-time compilation, debugging messages
23401 Turns on or off debugging messages from JIT debug support.
23402 @item show debug jit
23403 Displays the current state of @value{GDBN} JIT debugging.
23404 @item set debug lin-lwp
23405 @cindex @sc{gnu}/Linux LWP debug messages
23406 @cindex Linux lightweight processes
23407 Turns on or off debugging messages from the Linux LWP debug support.
23408 @item show debug lin-lwp
23409 Show the current state of Linux LWP debugging messages.
23410 @item set debug linux-namespaces
23411 @cindex @sc{gnu}/Linux namespaces debug messages
23412 Turns on or off debugging messages from the Linux namespaces debug support.
23413 @item show debug linux-namespaces
23414 Show the current state of Linux namespaces debugging messages.
23415 @item set debug mach-o
23416 @cindex Mach-O symbols processing
23417 Control display of debugging messages related to Mach-O symbols
23418 processing. The default is off.
23419 @item show debug mach-o
23420 Displays the current state of displaying debugging messages related to
23421 reading of COFF/PE exported symbols.
23422 @item set debug notification
23423 @cindex remote async notification debugging info
23424 Turns on or off debugging messages about remote async notification.
23425 The default is off.
23426 @item show debug notification
23427 Displays the current state of remote async notification debugging messages.
23428 @item set debug observer
23429 @cindex observer debugging info
23430 Turns on or off display of @value{GDBN} observer debugging. This
23431 includes info such as the notification of observable events.
23432 @item show debug observer
23433 Displays the current state of observer debugging.
23434 @item set debug overload
23435 @cindex C@t{++} overload debugging info
23436 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23437 info. This includes info such as ranking of functions, etc. The default
23439 @item show debug overload
23440 Displays the current state of displaying @value{GDBN} C@t{++} overload
23442 @cindex expression parser, debugging info
23443 @cindex debug expression parser
23444 @item set debug parser
23445 Turns on or off the display of expression parser debugging output.
23446 Internally, this sets the @code{yydebug} variable in the expression
23447 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23448 details. The default is off.
23449 @item show debug parser
23450 Show the current state of expression parser debugging.
23451 @cindex packets, reporting on stdout
23452 @cindex serial connections, debugging
23453 @cindex debug remote protocol
23454 @cindex remote protocol debugging
23455 @cindex display remote packets
23456 @item set debug remote
23457 Turns on or off display of reports on all packets sent back and forth across
23458 the serial line to the remote machine. The info is printed on the
23459 @value{GDBN} standard output stream. The default is off.
23460 @item show debug remote
23461 Displays the state of display of remote packets.
23462 @item set debug serial
23463 Turns on or off display of @value{GDBN} serial debugging info. The
23465 @item show debug serial
23466 Displays the current state of displaying @value{GDBN} serial debugging
23468 @item set debug solib-frv
23469 @cindex FR-V shared-library debugging
23470 Turns on or off debugging messages for FR-V shared-library code.
23471 @item show debug solib-frv
23472 Display the current state of FR-V shared-library code debugging
23474 @item set debug symbol-lookup
23475 @cindex symbol lookup
23476 Turns on or off display of debugging messages related to symbol lookup.
23477 The default is 0 (off).
23478 A value of 1 provides basic information.
23479 A value greater than 1 provides more verbose information.
23480 @item show debug symbol-lookup
23481 Show the current state of symbol lookup debugging messages.
23482 @item set debug symfile
23483 @cindex symbol file functions
23484 Turns on or off display of debugging messages related to symbol file functions.
23485 The default is off. @xref{Files}.
23486 @item show debug symfile
23487 Show the current state of symbol file debugging messages.
23488 @item set debug symtab-create
23489 @cindex symbol table creation
23490 Turns on or off display of debugging messages related to symbol table creation.
23491 The default is 0 (off).
23492 A value of 1 provides basic information.
23493 A value greater than 1 provides more verbose information.
23494 @item show debug symtab-create
23495 Show the current state of symbol table creation debugging.
23496 @item set debug target
23497 @cindex target debugging info
23498 Turns on or off display of @value{GDBN} target debugging info. This info
23499 includes what is going on at the target level of GDB, as it happens. The
23500 default is 0. Set it to 1 to track events, and to 2 to also track the
23501 value of large memory transfers.
23502 @item show debug target
23503 Displays the current state of displaying @value{GDBN} target debugging
23505 @item set debug timestamp
23506 @cindex timestampping debugging info
23507 Turns on or off display of timestamps with @value{GDBN} debugging info.
23508 When enabled, seconds and microseconds are displayed before each debugging
23510 @item show debug timestamp
23511 Displays the current state of displaying timestamps with @value{GDBN}
23513 @item set debug varobj
23514 @cindex variable object debugging info
23515 Turns on or off display of @value{GDBN} variable object debugging
23516 info. The default is off.
23517 @item show debug varobj
23518 Displays the current state of displaying @value{GDBN} variable object
23520 @item set debug xml
23521 @cindex XML parser debugging
23522 Turns on or off debugging messages for built-in XML parsers.
23523 @item show debug xml
23524 Displays the current state of XML debugging messages.
23527 @node Other Misc Settings
23528 @section Other Miscellaneous Settings
23529 @cindex miscellaneous settings
23532 @kindex set interactive-mode
23533 @item set interactive-mode
23534 If @code{on}, forces @value{GDBN} to assume that GDB was started
23535 in a terminal. In practice, this means that @value{GDBN} should wait
23536 for the user to answer queries generated by commands entered at
23537 the command prompt. If @code{off}, forces @value{GDBN} to operate
23538 in the opposite mode, and it uses the default answers to all queries.
23539 If @code{auto} (the default), @value{GDBN} tries to determine whether
23540 its standard input is a terminal, and works in interactive-mode if it
23541 is, non-interactively otherwise.
23543 In the vast majority of cases, the debugger should be able to guess
23544 correctly which mode should be used. But this setting can be useful
23545 in certain specific cases, such as running a MinGW @value{GDBN}
23546 inside a cygwin window.
23548 @kindex show interactive-mode
23549 @item show interactive-mode
23550 Displays whether the debugger is operating in interactive mode or not.
23553 @node Extending GDB
23554 @chapter Extending @value{GDBN}
23555 @cindex extending GDB
23557 @value{GDBN} provides several mechanisms for extension.
23558 @value{GDBN} also provides the ability to automatically load
23559 extensions when it reads a file for debugging. This allows the
23560 user to automatically customize @value{GDBN} for the program
23564 * Sequences:: Canned Sequences of @value{GDBN} Commands
23565 * Python:: Extending @value{GDBN} using Python
23566 * Guile:: Extending @value{GDBN} using Guile
23567 * Auto-loading extensions:: Automatically loading extensions
23568 * Multiple Extension Languages:: Working with multiple extension languages
23569 * Aliases:: Creating new spellings of existing commands
23572 To facilitate the use of extension languages, @value{GDBN} is capable
23573 of evaluating the contents of a file. When doing so, @value{GDBN}
23574 can recognize which extension language is being used by looking at
23575 the filename extension. Files with an unrecognized filename extension
23576 are always treated as a @value{GDBN} Command Files.
23577 @xref{Command Files,, Command files}.
23579 You can control how @value{GDBN} evaluates these files with the following
23583 @kindex set script-extension
23584 @kindex show script-extension
23585 @item set script-extension off
23586 All scripts are always evaluated as @value{GDBN} Command Files.
23588 @item set script-extension soft
23589 The debugger determines the scripting language based on filename
23590 extension. If this scripting language is supported, @value{GDBN}
23591 evaluates the script using that language. Otherwise, it evaluates
23592 the file as a @value{GDBN} Command File.
23594 @item set script-extension strict
23595 The debugger determines the scripting language based on filename
23596 extension, and evaluates the script using that language. If the
23597 language is not supported, then the evaluation fails.
23599 @item show script-extension
23600 Display the current value of the @code{script-extension} option.
23605 @section Canned Sequences of Commands
23607 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23608 Command Lists}), @value{GDBN} provides two ways to store sequences of
23609 commands for execution as a unit: user-defined commands and command
23613 * Define:: How to define your own commands
23614 * Hooks:: Hooks for user-defined commands
23615 * Command Files:: How to write scripts of commands to be stored in a file
23616 * Output:: Commands for controlled output
23617 * Auto-loading sequences:: Controlling auto-loaded command files
23621 @subsection User-defined Commands
23623 @cindex user-defined command
23624 @cindex arguments, to user-defined commands
23625 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23626 which you assign a new name as a command. This is done with the
23627 @code{define} command. User commands may accept up to 10 arguments
23628 separated by whitespace. Arguments are accessed within the user command
23629 via @code{$arg0@dots{}$arg9}. A trivial example:
23633 print $arg0 + $arg1 + $arg2
23638 To execute the command use:
23645 This defines the command @code{adder}, which prints the sum of
23646 its three arguments. Note the arguments are text substitutions, so they may
23647 reference variables, use complex expressions, or even perform inferior
23650 @cindex argument count in user-defined commands
23651 @cindex how many arguments (user-defined commands)
23652 In addition, @code{$argc} may be used to find out how many arguments have
23653 been passed. This expands to a number in the range 0@dots{}10.
23658 print $arg0 + $arg1
23661 print $arg0 + $arg1 + $arg2
23669 @item define @var{commandname}
23670 Define a command named @var{commandname}. If there is already a command
23671 by that name, you are asked to confirm that you want to redefine it.
23672 The argument @var{commandname} may be a bare command name consisting of letters,
23673 numbers, dashes, and underscores. It may also start with any predefined
23674 prefix command. For example, @samp{define target my-target} creates
23675 a user-defined @samp{target my-target} command.
23677 The definition of the command is made up of other @value{GDBN} command lines,
23678 which are given following the @code{define} command. The end of these
23679 commands is marked by a line containing @code{end}.
23682 @kindex end@r{ (user-defined commands)}
23683 @item document @var{commandname}
23684 Document the user-defined command @var{commandname}, so that it can be
23685 accessed by @code{help}. The command @var{commandname} must already be
23686 defined. This command reads lines of documentation just as @code{define}
23687 reads the lines of the command definition, ending with @code{end}.
23688 After the @code{document} command is finished, @code{help} on command
23689 @var{commandname} displays the documentation you have written.
23691 You may use the @code{document} command again to change the
23692 documentation of a command. Redefining the command with @code{define}
23693 does not change the documentation.
23695 @kindex dont-repeat
23696 @cindex don't repeat command
23698 Used inside a user-defined command, this tells @value{GDBN} that this
23699 command should not be repeated when the user hits @key{RET}
23700 (@pxref{Command Syntax, repeat last command}).
23702 @kindex help user-defined
23703 @item help user-defined
23704 List all user-defined commands and all python commands defined in class
23705 COMAND_USER. The first line of the documentation or docstring is
23710 @itemx show user @var{commandname}
23711 Display the @value{GDBN} commands used to define @var{commandname} (but
23712 not its documentation). If no @var{commandname} is given, display the
23713 definitions for all user-defined commands.
23714 This does not work for user-defined python commands.
23716 @cindex infinite recursion in user-defined commands
23717 @kindex show max-user-call-depth
23718 @kindex set max-user-call-depth
23719 @item show max-user-call-depth
23720 @itemx set max-user-call-depth
23721 The value of @code{max-user-call-depth} controls how many recursion
23722 levels are allowed in user-defined commands before @value{GDBN} suspects an
23723 infinite recursion and aborts the command.
23724 This does not apply to user-defined python commands.
23727 In addition to the above commands, user-defined commands frequently
23728 use control flow commands, described in @ref{Command Files}.
23730 When user-defined commands are executed, the
23731 commands of the definition are not printed. An error in any command
23732 stops execution of the user-defined command.
23734 If used interactively, commands that would ask for confirmation proceed
23735 without asking when used inside a user-defined command. Many @value{GDBN}
23736 commands that normally print messages to say what they are doing omit the
23737 messages when used in a user-defined command.
23740 @subsection User-defined Command Hooks
23741 @cindex command hooks
23742 @cindex hooks, for commands
23743 @cindex hooks, pre-command
23746 You may define @dfn{hooks}, which are a special kind of user-defined
23747 command. Whenever you run the command @samp{foo}, if the user-defined
23748 command @samp{hook-foo} exists, it is executed (with no arguments)
23749 before that command.
23751 @cindex hooks, post-command
23753 A hook may also be defined which is run after the command you executed.
23754 Whenever you run the command @samp{foo}, if the user-defined command
23755 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23756 that command. Post-execution hooks may exist simultaneously with
23757 pre-execution hooks, for the same command.
23759 It is valid for a hook to call the command which it hooks. If this
23760 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23762 @c It would be nice if hookpost could be passed a parameter indicating
23763 @c if the command it hooks executed properly or not. FIXME!
23765 @kindex stop@r{, a pseudo-command}
23766 In addition, a pseudo-command, @samp{stop} exists. Defining
23767 (@samp{hook-stop}) makes the associated commands execute every time
23768 execution stops in your program: before breakpoint commands are run,
23769 displays are printed, or the stack frame is printed.
23771 For example, to ignore @code{SIGALRM} signals while
23772 single-stepping, but treat them normally during normal execution,
23777 handle SIGALRM nopass
23781 handle SIGALRM pass
23784 define hook-continue
23785 handle SIGALRM pass
23789 As a further example, to hook at the beginning and end of the @code{echo}
23790 command, and to add extra text to the beginning and end of the message,
23798 define hookpost-echo
23802 (@value{GDBP}) echo Hello World
23803 <<<---Hello World--->>>
23808 You can define a hook for any single-word command in @value{GDBN}, but
23809 not for command aliases; you should define a hook for the basic command
23810 name, e.g.@: @code{backtrace} rather than @code{bt}.
23811 @c FIXME! So how does Joe User discover whether a command is an alias
23813 You can hook a multi-word command by adding @code{hook-} or
23814 @code{hookpost-} to the last word of the command, e.g.@:
23815 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23817 If an error occurs during the execution of your hook, execution of
23818 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23819 (before the command that you actually typed had a chance to run).
23821 If you try to define a hook which does not match any known command, you
23822 get a warning from the @code{define} command.
23824 @node Command Files
23825 @subsection Command Files
23827 @cindex command files
23828 @cindex scripting commands
23829 A command file for @value{GDBN} is a text file made of lines that are
23830 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23831 also be included. An empty line in a command file does nothing; it
23832 does not mean to repeat the last command, as it would from the
23835 You can request the execution of a command file with the @code{source}
23836 command. Note that the @code{source} command is also used to evaluate
23837 scripts that are not Command Files. The exact behavior can be configured
23838 using the @code{script-extension} setting.
23839 @xref{Extending GDB,, Extending GDB}.
23843 @cindex execute commands from a file
23844 @item source [-s] [-v] @var{filename}
23845 Execute the command file @var{filename}.
23848 The lines in a command file are generally executed sequentially,
23849 unless the order of execution is changed by one of the
23850 @emph{flow-control commands} described below. The commands are not
23851 printed as they are executed. An error in any command terminates
23852 execution of the command file and control is returned to the console.
23854 @value{GDBN} first searches for @var{filename} in the current directory.
23855 If the file is not found there, and @var{filename} does not specify a
23856 directory, then @value{GDBN} also looks for the file on the source search path
23857 (specified with the @samp{directory} command);
23858 except that @file{$cdir} is not searched because the compilation directory
23859 is not relevant to scripts.
23861 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23862 on the search path even if @var{filename} specifies a directory.
23863 The search is done by appending @var{filename} to each element of the
23864 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23865 and the search path contains @file{/home/user} then @value{GDBN} will
23866 look for the script @file{/home/user/mylib/myscript}.
23867 The search is also done if @var{filename} is an absolute path.
23868 For example, if @var{filename} is @file{/tmp/myscript} and
23869 the search path contains @file{/home/user} then @value{GDBN} will
23870 look for the script @file{/home/user/tmp/myscript}.
23871 For DOS-like systems, if @var{filename} contains a drive specification,
23872 it is stripped before concatenation. For example, if @var{filename} is
23873 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23874 will look for the script @file{c:/tmp/myscript}.
23876 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23877 each command as it is executed. The option must be given before
23878 @var{filename}, and is interpreted as part of the filename anywhere else.
23880 Commands that would ask for confirmation if used interactively proceed
23881 without asking when used in a command file. Many @value{GDBN} commands that
23882 normally print messages to say what they are doing omit the messages
23883 when called from command files.
23885 @value{GDBN} also accepts command input from standard input. In this
23886 mode, normal output goes to standard output and error output goes to
23887 standard error. Errors in a command file supplied on standard input do
23888 not terminate execution of the command file---execution continues with
23892 gdb < cmds > log 2>&1
23895 (The syntax above will vary depending on the shell used.) This example
23896 will execute commands from the file @file{cmds}. All output and errors
23897 would be directed to @file{log}.
23899 Since commands stored on command files tend to be more general than
23900 commands typed interactively, they frequently need to deal with
23901 complicated situations, such as different or unexpected values of
23902 variables and symbols, changes in how the program being debugged is
23903 built, etc. @value{GDBN} provides a set of flow-control commands to
23904 deal with these complexities. Using these commands, you can write
23905 complex scripts that loop over data structures, execute commands
23906 conditionally, etc.
23913 This command allows to include in your script conditionally executed
23914 commands. The @code{if} command takes a single argument, which is an
23915 expression to evaluate. It is followed by a series of commands that
23916 are executed only if the expression is true (its value is nonzero).
23917 There can then optionally be an @code{else} line, followed by a series
23918 of commands that are only executed if the expression was false. The
23919 end of the list is marked by a line containing @code{end}.
23923 This command allows to write loops. Its syntax is similar to
23924 @code{if}: the command takes a single argument, which is an expression
23925 to evaluate, and must be followed by the commands to execute, one per
23926 line, terminated by an @code{end}. These commands are called the
23927 @dfn{body} of the loop. The commands in the body of @code{while} are
23928 executed repeatedly as long as the expression evaluates to true.
23932 This command exits the @code{while} loop in whose body it is included.
23933 Execution of the script continues after that @code{while}s @code{end}
23936 @kindex loop_continue
23937 @item loop_continue
23938 This command skips the execution of the rest of the body of commands
23939 in the @code{while} loop in whose body it is included. Execution
23940 branches to the beginning of the @code{while} loop, where it evaluates
23941 the controlling expression.
23943 @kindex end@r{ (if/else/while commands)}
23945 Terminate the block of commands that are the body of @code{if},
23946 @code{else}, or @code{while} flow-control commands.
23951 @subsection Commands for Controlled Output
23953 During the execution of a command file or a user-defined command, normal
23954 @value{GDBN} output is suppressed; the only output that appears is what is
23955 explicitly printed by the commands in the definition. This section
23956 describes three commands useful for generating exactly the output you
23961 @item echo @var{text}
23962 @c I do not consider backslash-space a standard C escape sequence
23963 @c because it is not in ANSI.
23964 Print @var{text}. Nonprinting characters can be included in
23965 @var{text} using C escape sequences, such as @samp{\n} to print a
23966 newline. @strong{No newline is printed unless you specify one.}
23967 In addition to the standard C escape sequences, a backslash followed
23968 by a space stands for a space. This is useful for displaying a
23969 string with spaces at the beginning or the end, since leading and
23970 trailing spaces are otherwise trimmed from all arguments.
23971 To print @samp{@w{ }and foo =@w{ }}, use the command
23972 @samp{echo \@w{ }and foo = \@w{ }}.
23974 A backslash at the end of @var{text} can be used, as in C, to continue
23975 the command onto subsequent lines. For example,
23978 echo This is some text\n\
23979 which is continued\n\
23980 onto several lines.\n
23983 produces the same output as
23986 echo This is some text\n
23987 echo which is continued\n
23988 echo onto several lines.\n
23992 @item output @var{expression}
23993 Print the value of @var{expression} and nothing but that value: no
23994 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23995 value history either. @xref{Expressions, ,Expressions}, for more information
23998 @item output/@var{fmt} @var{expression}
23999 Print the value of @var{expression} in format @var{fmt}. You can use
24000 the same formats as for @code{print}. @xref{Output Formats,,Output
24001 Formats}, for more information.
24004 @item printf @var{template}, @var{expressions}@dots{}
24005 Print the values of one or more @var{expressions} under the control of
24006 the string @var{template}. To print several values, make
24007 @var{expressions} be a comma-separated list of individual expressions,
24008 which may be either numbers or pointers. Their values are printed as
24009 specified by @var{template}, exactly as a C program would do by
24010 executing the code below:
24013 printf (@var{template}, @var{expressions}@dots{});
24016 As in @code{C} @code{printf}, ordinary characters in @var{template}
24017 are printed verbatim, while @dfn{conversion specification} introduced
24018 by the @samp{%} character cause subsequent @var{expressions} to be
24019 evaluated, their values converted and formatted according to type and
24020 style information encoded in the conversion specifications, and then
24023 For example, you can print two values in hex like this:
24026 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24029 @code{printf} supports all the standard @code{C} conversion
24030 specifications, including the flags and modifiers between the @samp{%}
24031 character and the conversion letter, with the following exceptions:
24035 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24038 The modifier @samp{*} is not supported for specifying precision or
24042 The @samp{'} flag (for separation of digits into groups according to
24043 @code{LC_NUMERIC'}) is not supported.
24046 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24050 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24053 The conversion letters @samp{a} and @samp{A} are not supported.
24057 Note that the @samp{ll} type modifier is supported only if the
24058 underlying @code{C} implementation used to build @value{GDBN} supports
24059 the @code{long long int} type, and the @samp{L} type modifier is
24060 supported only if @code{long double} type is available.
24062 As in @code{C}, @code{printf} supports simple backslash-escape
24063 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24064 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24065 single character. Octal and hexadecimal escape sequences are not
24068 Additionally, @code{printf} supports conversion specifications for DFP
24069 (@dfn{Decimal Floating Point}) types using the following length modifiers
24070 together with a floating point specifier.
24075 @samp{H} for printing @code{Decimal32} types.
24078 @samp{D} for printing @code{Decimal64} types.
24081 @samp{DD} for printing @code{Decimal128} types.
24084 If the underlying @code{C} implementation used to build @value{GDBN} has
24085 support for the three length modifiers for DFP types, other modifiers
24086 such as width and precision will also be available for @value{GDBN} to use.
24088 In case there is no such @code{C} support, no additional modifiers will be
24089 available and the value will be printed in the standard way.
24091 Here's an example of printing DFP types using the above conversion letters:
24093 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24097 @item eval @var{template}, @var{expressions}@dots{}
24098 Convert the values of one or more @var{expressions} under the control of
24099 the string @var{template} to a command line, and call it.
24103 @node Auto-loading sequences
24104 @subsection Controlling auto-loading native @value{GDBN} scripts
24105 @cindex native script auto-loading
24107 When a new object file is read (for example, due to the @code{file}
24108 command, or because the inferior has loaded a shared library),
24109 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24110 @xref{Auto-loading extensions}.
24112 Auto-loading can be enabled or disabled,
24113 and the list of auto-loaded scripts can be printed.
24116 @anchor{set auto-load gdb-scripts}
24117 @kindex set auto-load gdb-scripts
24118 @item set auto-load gdb-scripts [on|off]
24119 Enable or disable the auto-loading of canned sequences of commands scripts.
24121 @anchor{show auto-load gdb-scripts}
24122 @kindex show auto-load gdb-scripts
24123 @item show auto-load gdb-scripts
24124 Show whether auto-loading of canned sequences of commands scripts is enabled or
24127 @anchor{info auto-load gdb-scripts}
24128 @kindex info auto-load gdb-scripts
24129 @cindex print list of auto-loaded canned sequences of commands scripts
24130 @item info auto-load gdb-scripts [@var{regexp}]
24131 Print the list of all canned sequences of commands scripts that @value{GDBN}
24135 If @var{regexp} is supplied only canned sequences of commands scripts with
24136 matching names are printed.
24138 @c Python docs live in a separate file.
24139 @include python.texi
24141 @c Guile docs live in a separate file.
24142 @include guile.texi
24144 @node Auto-loading extensions
24145 @section Auto-loading extensions
24146 @cindex auto-loading extensions
24148 @value{GDBN} provides two mechanisms for automatically loading extensions
24149 when a new object file is read (for example, due to the @code{file}
24150 command, or because the inferior has loaded a shared library):
24151 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24152 section of modern file formats like ELF.
24155 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24156 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24157 * Which flavor to choose?::
24160 The auto-loading feature is useful for supplying application-specific
24161 debugging commands and features.
24163 Auto-loading can be enabled or disabled,
24164 and the list of auto-loaded scripts can be printed.
24165 See the @samp{auto-loading} section of each extension language
24166 for more information.
24167 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24168 For Python files see @ref{Python Auto-loading}.
24170 Note that loading of this script file also requires accordingly configured
24171 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24173 @node objfile-gdbdotext file
24174 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24175 @cindex @file{@var{objfile}-gdb.gdb}
24176 @cindex @file{@var{objfile}-gdb.py}
24177 @cindex @file{@var{objfile}-gdb.scm}
24179 When a new object file is read, @value{GDBN} looks for a file named
24180 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24181 where @var{objfile} is the object file's name and
24182 where @var{ext} is the file extension for the extension language:
24185 @item @file{@var{objfile}-gdb.gdb}
24186 GDB's own command language
24187 @item @file{@var{objfile}-gdb.py}
24189 @item @file{@var{objfile}-gdb.scm}
24193 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24194 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24195 components, and appending the @file{-gdb.@var{ext}} suffix.
24196 If this file exists and is readable, @value{GDBN} will evaluate it as a
24197 script in the specified extension language.
24199 If this file does not exist, then @value{GDBN} will look for
24200 @var{script-name} file in all of the directories as specified below.
24202 Note that loading of these files requires an accordingly configured
24203 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24205 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24206 scripts normally according to its @file{.exe} filename. But if no scripts are
24207 found @value{GDBN} also tries script filenames matching the object file without
24208 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24209 is attempted on any platform. This makes the script filenames compatible
24210 between Unix and MS-Windows hosts.
24213 @anchor{set auto-load scripts-directory}
24214 @kindex set auto-load scripts-directory
24215 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24216 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24217 may be delimited by the host platform path separator in use
24218 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24220 Each entry here needs to be covered also by the security setting
24221 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24223 @anchor{with-auto-load-dir}
24224 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24225 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24226 configuration option @option{--with-auto-load-dir}.
24228 Any reference to @file{$debugdir} will get replaced by
24229 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24230 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24231 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24232 @file{$datadir} must be placed as a directory component --- either alone or
24233 delimited by @file{/} or @file{\} directory separators, depending on the host
24236 The list of directories uses path separator (@samp{:} on GNU and Unix
24237 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24238 to the @env{PATH} environment variable.
24240 @anchor{show auto-load scripts-directory}
24241 @kindex show auto-load scripts-directory
24242 @item show auto-load scripts-directory
24243 Show @value{GDBN} auto-loaded scripts location.
24245 @anchor{add-auto-load-scripts-directory}
24246 @kindex add-auto-load-scripts-directory
24247 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24248 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24249 Multiple entries may be delimited by the host platform path separator in use.
24252 @value{GDBN} does not track which files it has already auto-loaded this way.
24253 @value{GDBN} will load the associated script every time the corresponding
24254 @var{objfile} is opened.
24255 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24256 is evaluated more than once.
24258 @node dotdebug_gdb_scripts section
24259 @subsection The @code{.debug_gdb_scripts} section
24260 @cindex @code{.debug_gdb_scripts} section
24262 For systems using file formats like ELF and COFF,
24263 when @value{GDBN} loads a new object file
24264 it will look for a special section named @code{.debug_gdb_scripts}.
24265 If this section exists, its contents is a list of null-terminated entries
24266 specifying scripts to load. Each entry begins with a non-null prefix byte that
24267 specifies the kind of entry, typically the extension language and whether the
24268 script is in a file or inlined in @code{.debug_gdb_scripts}.
24270 The following entries are supported:
24273 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24274 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24275 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24276 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24279 @subsubsection Script File Entries
24281 If the entry specifies a file, @value{GDBN} will look for the file first
24282 in the current directory and then along the source search path
24283 (@pxref{Source Path, ,Specifying Source Directories}),
24284 except that @file{$cdir} is not searched, since the compilation
24285 directory is not relevant to scripts.
24287 File entries can be placed in section @code{.debug_gdb_scripts} with,
24288 for example, this GCC macro for Python scripts.
24291 /* Note: The "MS" section flags are to remove duplicates. */
24292 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24294 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24295 .byte 1 /* Python */\n\
24296 .asciz \"" script_name "\"\n\
24302 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24303 Then one can reference the macro in a header or source file like this:
24306 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24309 The script name may include directories if desired.
24311 Note that loading of this script file also requires accordingly configured
24312 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24314 If the macro invocation is put in a header, any application or library
24315 using this header will get a reference to the specified script,
24316 and with the use of @code{"MS"} attributes on the section, the linker
24317 will remove duplicates.
24319 @subsubsection Script Text Entries
24321 Script text entries allow to put the executable script in the entry
24322 itself instead of loading it from a file.
24323 The first line of the entry, everything after the prefix byte and up to
24324 the first newline (@code{0xa}) character, is the script name, and must not
24325 contain any kind of space character, e.g., spaces or tabs.
24326 The rest of the entry, up to the trailing null byte, is the script to
24327 execute in the specified language. The name needs to be unique among
24328 all script names, as @value{GDBN} executes each script only once based
24331 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24335 #include "symcat.h"
24336 #include "gdb/section-scripts.h"
24338 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24339 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24340 ".ascii \"gdb.inlined-script\\n\"\n"
24341 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24342 ".ascii \" def __init__ (self):\\n\"\n"
24343 ".ascii \" super (test_cmd, self).__init__ ("
24344 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24345 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24346 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24347 ".ascii \"test_cmd ()\\n\"\n"
24353 Loading of inlined scripts requires a properly configured
24354 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24355 The path to specify in @code{auto-load safe-path} is the path of the file
24356 containing the @code{.debug_gdb_scripts} section.
24358 @node Which flavor to choose?
24359 @subsection Which flavor to choose?
24361 Given the multiple ways of auto-loading extensions, it might not always
24362 be clear which one to choose. This section provides some guidance.
24365 Benefits of the @file{-gdb.@var{ext}} way:
24369 Can be used with file formats that don't support multiple sections.
24372 Ease of finding scripts for public libraries.
24374 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24375 in the source search path.
24376 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24377 isn't a source directory in which to find the script.
24380 Doesn't require source code additions.
24384 Benefits of the @code{.debug_gdb_scripts} way:
24388 Works with static linking.
24390 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24391 trigger their loading. When an application is statically linked the only
24392 objfile available is the executable, and it is cumbersome to attach all the
24393 scripts from all the input libraries to the executable's
24394 @file{-gdb.@var{ext}} script.
24397 Works with classes that are entirely inlined.
24399 Some classes can be entirely inlined, and thus there may not be an associated
24400 shared library to attach a @file{-gdb.@var{ext}} script to.
24403 Scripts needn't be copied out of the source tree.
24405 In some circumstances, apps can be built out of large collections of internal
24406 libraries, and the build infrastructure necessary to install the
24407 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24408 cumbersome. It may be easier to specify the scripts in the
24409 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24410 top of the source tree to the source search path.
24413 @node Multiple Extension Languages
24414 @section Multiple Extension Languages
24416 The Guile and Python extension languages do not share any state,
24417 and generally do not interfere with each other.
24418 There are some things to be aware of, however.
24420 @subsection Python comes first
24422 Python was @value{GDBN}'s first extension language, and to avoid breaking
24423 existing behaviour Python comes first. This is generally solved by the
24424 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24425 extension languages, and when it makes a call to an extension language,
24426 (say to pretty-print a value), it tries each in turn until an extension
24427 language indicates it has performed the request (e.g., has returned the
24428 pretty-printed form of a value).
24429 This extends to errors while performing such requests: If an error happens
24430 while, for example, trying to pretty-print an object then the error is
24431 reported and any following extension languages are not tried.
24434 @section Creating new spellings of existing commands
24435 @cindex aliases for commands
24437 It is often useful to define alternate spellings of existing commands.
24438 For example, if a new @value{GDBN} command defined in Python has
24439 a long name to type, it is handy to have an abbreviated version of it
24440 that involves less typing.
24442 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24443 of the @samp{step} command even though it is otherwise an ambiguous
24444 abbreviation of other commands like @samp{set} and @samp{show}.
24446 Aliases are also used to provide shortened or more common versions
24447 of multi-word commands. For example, @value{GDBN} provides the
24448 @samp{tty} alias of the @samp{set inferior-tty} command.
24450 You can define a new alias with the @samp{alias} command.
24455 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24459 @var{ALIAS} specifies the name of the new alias.
24460 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24463 @var{COMMAND} specifies the name of an existing command
24464 that is being aliased.
24466 The @samp{-a} option specifies that the new alias is an abbreviation
24467 of the command. Abbreviations are not shown in command
24468 lists displayed by the @samp{help} command.
24470 The @samp{--} option specifies the end of options,
24471 and is useful when @var{ALIAS} begins with a dash.
24473 Here is a simple example showing how to make an abbreviation
24474 of a command so that there is less to type.
24475 Suppose you were tired of typing @samp{disas}, the current
24476 shortest unambiguous abbreviation of the @samp{disassemble} command
24477 and you wanted an even shorter version named @samp{di}.
24478 The following will accomplish this.
24481 (gdb) alias -a di = disas
24484 Note that aliases are different from user-defined commands.
24485 With a user-defined command, you also need to write documentation
24486 for it with the @samp{document} command.
24487 An alias automatically picks up the documentation of the existing command.
24489 Here is an example where we make @samp{elms} an abbreviation of
24490 @samp{elements} in the @samp{set print elements} command.
24491 This is to show that you can make an abbreviation of any part
24495 (gdb) alias -a set print elms = set print elements
24496 (gdb) alias -a show print elms = show print elements
24497 (gdb) set p elms 20
24499 Limit on string chars or array elements to print is 200.
24502 Note that if you are defining an alias of a @samp{set} command,
24503 and you want to have an alias for the corresponding @samp{show}
24504 command, then you need to define the latter separately.
24506 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24507 @var{ALIAS}, just as they are normally.
24510 (gdb) alias -a set pr elms = set p ele
24513 Finally, here is an example showing the creation of a one word
24514 alias for a more complex command.
24515 This creates alias @samp{spe} of the command @samp{set print elements}.
24518 (gdb) alias spe = set print elements
24523 @chapter Command Interpreters
24524 @cindex command interpreters
24526 @value{GDBN} supports multiple command interpreters, and some command
24527 infrastructure to allow users or user interface writers to switch
24528 between interpreters or run commands in other interpreters.
24530 @value{GDBN} currently supports two command interpreters, the console
24531 interpreter (sometimes called the command-line interpreter or @sc{cli})
24532 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24533 describes both of these interfaces in great detail.
24535 By default, @value{GDBN} will start with the console interpreter.
24536 However, the user may choose to start @value{GDBN} with another
24537 interpreter by specifying the @option{-i} or @option{--interpreter}
24538 startup options. Defined interpreters include:
24542 @cindex console interpreter
24543 The traditional console or command-line interpreter. This is the most often
24544 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24545 @value{GDBN} will use this interpreter.
24548 @cindex mi interpreter
24549 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24550 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24551 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24555 @cindex mi2 interpreter
24556 The current @sc{gdb/mi} interface.
24559 @cindex mi1 interpreter
24560 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24564 @cindex invoke another interpreter
24565 The interpreter being used by @value{GDBN} may not be dynamically
24566 switched at runtime. Although possible, this could lead to a very
24567 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24568 enters the command "interpreter-set console" in a console view,
24569 @value{GDBN} would switch to using the console interpreter, rendering
24570 the IDE inoperable!
24572 @kindex interpreter-exec
24573 Although you may only choose a single interpreter at startup, you may execute
24574 commands in any interpreter from the current interpreter using the appropriate
24575 command. If you are running the console interpreter, simply use the
24576 @code{interpreter-exec} command:
24579 interpreter-exec mi "-data-list-register-names"
24582 @sc{gdb/mi} has a similar command, although it is only available in versions of
24583 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24586 @chapter @value{GDBN} Text User Interface
24588 @cindex Text User Interface
24591 * TUI Overview:: TUI overview
24592 * TUI Keys:: TUI key bindings
24593 * TUI Single Key Mode:: TUI single key mode
24594 * TUI Commands:: TUI-specific commands
24595 * TUI Configuration:: TUI configuration variables
24598 The @value{GDBN} Text User Interface (TUI) is a terminal
24599 interface which uses the @code{curses} library to show the source
24600 file, the assembly output, the program registers and @value{GDBN}
24601 commands in separate text windows. The TUI mode is supported only
24602 on platforms where a suitable version of the @code{curses} library
24605 The TUI mode is enabled by default when you invoke @value{GDBN} as
24606 @samp{@value{GDBP} -tui}.
24607 You can also switch in and out of TUI mode while @value{GDBN} runs by
24608 using various TUI commands and key bindings, such as @command{tui
24609 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
24610 @ref{TUI Keys, ,TUI Key Bindings}.
24613 @section TUI Overview
24615 In TUI mode, @value{GDBN} can display several text windows:
24619 This window is the @value{GDBN} command window with the @value{GDBN}
24620 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24621 managed using readline.
24624 The source window shows the source file of the program. The current
24625 line and active breakpoints are displayed in this window.
24628 The assembly window shows the disassembly output of the program.
24631 This window shows the processor registers. Registers are highlighted
24632 when their values change.
24635 The source and assembly windows show the current program position
24636 by highlighting the current line and marking it with a @samp{>} marker.
24637 Breakpoints are indicated with two markers. The first marker
24638 indicates the breakpoint type:
24642 Breakpoint which was hit at least once.
24645 Breakpoint which was never hit.
24648 Hardware breakpoint which was hit at least once.
24651 Hardware breakpoint which was never hit.
24654 The second marker indicates whether the breakpoint is enabled or not:
24658 Breakpoint is enabled.
24661 Breakpoint is disabled.
24664 The source, assembly and register windows are updated when the current
24665 thread changes, when the frame changes, or when the program counter
24668 These windows are not all visible at the same time. The command
24669 window is always visible. The others can be arranged in several
24680 source and assembly,
24683 source and registers, or
24686 assembly and registers.
24689 A status line above the command window shows the following information:
24693 Indicates the current @value{GDBN} target.
24694 (@pxref{Targets, ,Specifying a Debugging Target}).
24697 Gives the current process or thread number.
24698 When no process is being debugged, this field is set to @code{No process}.
24701 Gives the current function name for the selected frame.
24702 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24703 When there is no symbol corresponding to the current program counter,
24704 the string @code{??} is displayed.
24707 Indicates the current line number for the selected frame.
24708 When the current line number is not known, the string @code{??} is displayed.
24711 Indicates the current program counter address.
24715 @section TUI Key Bindings
24716 @cindex TUI key bindings
24718 The TUI installs several key bindings in the readline keymaps
24719 @ifset SYSTEM_READLINE
24720 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24722 @ifclear SYSTEM_READLINE
24723 (@pxref{Command Line Editing}).
24725 The following key bindings are installed for both TUI mode and the
24726 @value{GDBN} standard mode.
24735 Enter or leave the TUI mode. When leaving the TUI mode,
24736 the curses window management stops and @value{GDBN} operates using
24737 its standard mode, writing on the terminal directly. When reentering
24738 the TUI mode, control is given back to the curses windows.
24739 The screen is then refreshed.
24743 Use a TUI layout with only one window. The layout will
24744 either be @samp{source} or @samp{assembly}. When the TUI mode
24745 is not active, it will switch to the TUI mode.
24747 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24751 Use a TUI layout with at least two windows. When the current
24752 layout already has two windows, the next layout with two windows is used.
24753 When a new layout is chosen, one window will always be common to the
24754 previous layout and the new one.
24756 Think of it as the Emacs @kbd{C-x 2} binding.
24760 Change the active window. The TUI associates several key bindings
24761 (like scrolling and arrow keys) with the active window. This command
24762 gives the focus to the next TUI window.
24764 Think of it as the Emacs @kbd{C-x o} binding.
24768 Switch in and out of the TUI SingleKey mode that binds single
24769 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24772 The following key bindings only work in the TUI mode:
24777 Scroll the active window one page up.
24781 Scroll the active window one page down.
24785 Scroll the active window one line up.
24789 Scroll the active window one line down.
24793 Scroll the active window one column left.
24797 Scroll the active window one column right.
24801 Refresh the screen.
24804 Because the arrow keys scroll the active window in the TUI mode, they
24805 are not available for their normal use by readline unless the command
24806 window has the focus. When another window is active, you must use
24807 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24808 and @kbd{C-f} to control the command window.
24810 @node TUI Single Key Mode
24811 @section TUI Single Key Mode
24812 @cindex TUI single key mode
24814 The TUI also provides a @dfn{SingleKey} mode, which binds several
24815 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24816 switch into this mode, where the following key bindings are used:
24819 @kindex c @r{(SingleKey TUI key)}
24823 @kindex d @r{(SingleKey TUI key)}
24827 @kindex f @r{(SingleKey TUI key)}
24831 @kindex n @r{(SingleKey TUI key)}
24835 @kindex q @r{(SingleKey TUI key)}
24837 exit the SingleKey mode.
24839 @kindex r @r{(SingleKey TUI key)}
24843 @kindex s @r{(SingleKey TUI key)}
24847 @kindex u @r{(SingleKey TUI key)}
24851 @kindex v @r{(SingleKey TUI key)}
24855 @kindex w @r{(SingleKey TUI key)}
24860 Other keys temporarily switch to the @value{GDBN} command prompt.
24861 The key that was pressed is inserted in the editing buffer so that
24862 it is possible to type most @value{GDBN} commands without interaction
24863 with the TUI SingleKey mode. Once the command is entered the TUI
24864 SingleKey mode is restored. The only way to permanently leave
24865 this mode is by typing @kbd{q} or @kbd{C-x s}.
24869 @section TUI-specific Commands
24870 @cindex TUI commands
24872 The TUI has specific commands to control the text windows.
24873 These commands are always available, even when @value{GDBN} is not in
24874 the TUI mode. When @value{GDBN} is in the standard mode, most
24875 of these commands will automatically switch to the TUI mode.
24877 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24878 terminal, or @value{GDBN} has been started with the machine interface
24879 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24880 these commands will fail with an error, because it would not be
24881 possible or desirable to enable curses window management.
24886 Activate TUI mode. The last active TUI window layout will be used if
24887 TUI mode has prevsiouly been used in the current debugging session,
24888 otherwise a default layout is used.
24891 @kindex tui disable
24892 Disable TUI mode, returning to the console interpreter.
24896 List and give the size of all displayed windows.
24898 @item layout @var{name}
24900 Changes which TUI windows are displayed. In each layout the command
24901 window is always displayed, the @var{name} parameter controls which
24902 additional windows are displayed, and can be any of the following:
24906 Display the next layout.
24909 Display the previous layout.
24912 Display the source and command windows.
24915 Display the assembly and command windows.
24918 Display the source, assembly, and command windows.
24921 When in @code{src} layout display the register, source, and command
24922 windows. When in @code{asm} or @code{split} layout display the
24923 register, assembler, and command windows.
24926 @item focus @var{name}
24928 Changes which TUI window is currently active for scrolling. The
24929 @var{name} parameter can be any of the following:
24933 Make the next window active for scrolling.
24936 Make the previous window active for scrolling.
24939 Make the source window active for scrolling.
24942 Make the assembly window active for scrolling.
24945 Make the register window active for scrolling.
24948 Make the command window active for scrolling.
24953 Refresh the screen. This is similar to typing @kbd{C-L}.
24955 @item tui reg @var{group}
24957 Changes the register group displayed in the tui register window to
24958 @var{group}. If the register window is not currently displayed this
24959 command will cause the register window to be displayed. The list of
24960 register groups, as well as their order is target specific. The
24961 following groups are available on most targets:
24964 Repeatedly selecting this group will cause the display to cycle
24965 through all of the available register groups.
24968 Repeatedly selecting this group will cause the display to cycle
24969 through all of the available register groups in the reverse order to
24973 Display the general registers.
24975 Display the floating point registers.
24977 Display the system registers.
24979 Display the vector registers.
24981 Display all registers.
24986 Update the source window and the current execution point.
24988 @item winheight @var{name} +@var{count}
24989 @itemx winheight @var{name} -@var{count}
24991 Change the height of the window @var{name} by @var{count}
24992 lines. Positive counts increase the height, while negative counts
24993 decrease it. The @var{name} parameter can be one of @code{src} (the
24994 source window), @code{cmd} (the command window), @code{asm} (the
24995 disassembly window), or @code{regs} (the register display window).
24997 @item tabset @var{nchars}
24999 Set the width of tab stops to be @var{nchars} characters. This
25000 setting affects the display of TAB characters in the source and
25004 @node TUI Configuration
25005 @section TUI Configuration Variables
25006 @cindex TUI configuration variables
25008 Several configuration variables control the appearance of TUI windows.
25011 @item set tui border-kind @var{kind}
25012 @kindex set tui border-kind
25013 Select the border appearance for the source, assembly and register windows.
25014 The possible values are the following:
25017 Use a space character to draw the border.
25020 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25023 Use the Alternate Character Set to draw the border. The border is
25024 drawn using character line graphics if the terminal supports them.
25027 @item set tui border-mode @var{mode}
25028 @kindex set tui border-mode
25029 @itemx set tui active-border-mode @var{mode}
25030 @kindex set tui active-border-mode
25031 Select the display attributes for the borders of the inactive windows
25032 or the active window. The @var{mode} can be one of the following:
25035 Use normal attributes to display the border.
25041 Use reverse video mode.
25044 Use half bright mode.
25046 @item half-standout
25047 Use half bright and standout mode.
25050 Use extra bright or bold mode.
25052 @item bold-standout
25053 Use extra bright or bold and standout mode.
25058 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25061 @cindex @sc{gnu} Emacs
25062 A special interface allows you to use @sc{gnu} Emacs to view (and
25063 edit) the source files for the program you are debugging with
25066 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25067 executable file you want to debug as an argument. This command starts
25068 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25069 created Emacs buffer.
25070 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25072 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25077 All ``terminal'' input and output goes through an Emacs buffer, called
25080 This applies both to @value{GDBN} commands and their output, and to the input
25081 and output done by the program you are debugging.
25083 This is useful because it means that you can copy the text of previous
25084 commands and input them again; you can even use parts of the output
25087 All the facilities of Emacs' Shell mode are available for interacting
25088 with your program. In particular, you can send signals the usual
25089 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25093 @value{GDBN} displays source code through Emacs.
25095 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25096 source file for that frame and puts an arrow (@samp{=>}) at the
25097 left margin of the current line. Emacs uses a separate buffer for
25098 source display, and splits the screen to show both your @value{GDBN} session
25101 Explicit @value{GDBN} @code{list} or search commands still produce output as
25102 usual, but you probably have no reason to use them from Emacs.
25105 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25106 a graphical mode, enabled by default, which provides further buffers
25107 that can control the execution and describe the state of your program.
25108 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25110 If you specify an absolute file name when prompted for the @kbd{M-x
25111 gdb} argument, then Emacs sets your current working directory to where
25112 your program resides. If you only specify the file name, then Emacs
25113 sets your current working directory to the directory associated
25114 with the previous buffer. In this case, @value{GDBN} may find your
25115 program by searching your environment's @code{PATH} variable, but on
25116 some operating systems it might not find the source. So, although the
25117 @value{GDBN} input and output session proceeds normally, the auxiliary
25118 buffer does not display the current source and line of execution.
25120 The initial working directory of @value{GDBN} is printed on the top
25121 line of the GUD buffer and this serves as a default for the commands
25122 that specify files for @value{GDBN} to operate on. @xref{Files,
25123 ,Commands to Specify Files}.
25125 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25126 need to call @value{GDBN} by a different name (for example, if you
25127 keep several configurations around, with different names) you can
25128 customize the Emacs variable @code{gud-gdb-command-name} to run the
25131 In the GUD buffer, you can use these special Emacs commands in
25132 addition to the standard Shell mode commands:
25136 Describe the features of Emacs' GUD Mode.
25139 Execute to another source line, like the @value{GDBN} @code{step} command; also
25140 update the display window to show the current file and location.
25143 Execute to next source line in this function, skipping all function
25144 calls, like the @value{GDBN} @code{next} command. Then update the display window
25145 to show the current file and location.
25148 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25149 display window accordingly.
25152 Execute until exit from the selected stack frame, like the @value{GDBN}
25153 @code{finish} command.
25156 Continue execution of your program, like the @value{GDBN} @code{continue}
25160 Go up the number of frames indicated by the numeric argument
25161 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25162 like the @value{GDBN} @code{up} command.
25165 Go down the number of frames indicated by the numeric argument, like the
25166 @value{GDBN} @code{down} command.
25169 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25170 tells @value{GDBN} to set a breakpoint on the source line point is on.
25172 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25173 separate frame which shows a backtrace when the GUD buffer is current.
25174 Move point to any frame in the stack and type @key{RET} to make it
25175 become the current frame and display the associated source in the
25176 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25177 selected frame become the current one. In graphical mode, the
25178 speedbar displays watch expressions.
25180 If you accidentally delete the source-display buffer, an easy way to get
25181 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25182 request a frame display; when you run under Emacs, this recreates
25183 the source buffer if necessary to show you the context of the current
25186 The source files displayed in Emacs are in ordinary Emacs buffers
25187 which are visiting the source files in the usual way. You can edit
25188 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25189 communicates with Emacs in terms of line numbers. If you add or
25190 delete lines from the text, the line numbers that @value{GDBN} knows cease
25191 to correspond properly with the code.
25193 A more detailed description of Emacs' interaction with @value{GDBN} is
25194 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25198 @chapter The @sc{gdb/mi} Interface
25200 @unnumberedsec Function and Purpose
25202 @cindex @sc{gdb/mi}, its purpose
25203 @sc{gdb/mi} is a line based machine oriented text interface to
25204 @value{GDBN} and is activated by specifying using the
25205 @option{--interpreter} command line option (@pxref{Mode Options}). It
25206 is specifically intended to support the development of systems which
25207 use the debugger as just one small component of a larger system.
25209 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25210 in the form of a reference manual.
25212 Note that @sc{gdb/mi} is still under construction, so some of the
25213 features described below are incomplete and subject to change
25214 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25216 @unnumberedsec Notation and Terminology
25218 @cindex notational conventions, for @sc{gdb/mi}
25219 This chapter uses the following notation:
25223 @code{|} separates two alternatives.
25226 @code{[ @var{something} ]} indicates that @var{something} is optional:
25227 it may or may not be given.
25230 @code{( @var{group} )*} means that @var{group} inside the parentheses
25231 may repeat zero or more times.
25234 @code{( @var{group} )+} means that @var{group} inside the parentheses
25235 may repeat one or more times.
25238 @code{"@var{string}"} means a literal @var{string}.
25242 @heading Dependencies
25246 * GDB/MI General Design::
25247 * GDB/MI Command Syntax::
25248 * GDB/MI Compatibility with CLI::
25249 * GDB/MI Development and Front Ends::
25250 * GDB/MI Output Records::
25251 * GDB/MI Simple Examples::
25252 * GDB/MI Command Description Format::
25253 * GDB/MI Breakpoint Commands::
25254 * GDB/MI Catchpoint Commands::
25255 * GDB/MI Program Context::
25256 * GDB/MI Thread Commands::
25257 * GDB/MI Ada Tasking Commands::
25258 * GDB/MI Program Execution::
25259 * GDB/MI Stack Manipulation::
25260 * GDB/MI Variable Objects::
25261 * GDB/MI Data Manipulation::
25262 * GDB/MI Tracepoint Commands::
25263 * GDB/MI Symbol Query::
25264 * GDB/MI File Commands::
25266 * GDB/MI Kod Commands::
25267 * GDB/MI Memory Overlay Commands::
25268 * GDB/MI Signal Handling Commands::
25270 * GDB/MI Target Manipulation::
25271 * GDB/MI File Transfer Commands::
25272 * GDB/MI Ada Exceptions Commands::
25273 * GDB/MI Support Commands::
25274 * GDB/MI Miscellaneous Commands::
25277 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25278 @node GDB/MI General Design
25279 @section @sc{gdb/mi} General Design
25280 @cindex GDB/MI General Design
25282 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25283 parts---commands sent to @value{GDBN}, responses to those commands
25284 and notifications. Each command results in exactly one response,
25285 indicating either successful completion of the command, or an error.
25286 For the commands that do not resume the target, the response contains the
25287 requested information. For the commands that resume the target, the
25288 response only indicates whether the target was successfully resumed.
25289 Notifications is the mechanism for reporting changes in the state of the
25290 target, or in @value{GDBN} state, that cannot conveniently be associated with
25291 a command and reported as part of that command response.
25293 The important examples of notifications are:
25297 Exec notifications. These are used to report changes in
25298 target state---when a target is resumed, or stopped. It would not
25299 be feasible to include this information in response of resuming
25300 commands, because one resume commands can result in multiple events in
25301 different threads. Also, quite some time may pass before any event
25302 happens in the target, while a frontend needs to know whether the resuming
25303 command itself was successfully executed.
25306 Console output, and status notifications. Console output
25307 notifications are used to report output of CLI commands, as well as
25308 diagnostics for other commands. Status notifications are used to
25309 report the progress of a long-running operation. Naturally, including
25310 this information in command response would mean no output is produced
25311 until the command is finished, which is undesirable.
25314 General notifications. Commands may have various side effects on
25315 the @value{GDBN} or target state beyond their official purpose. For example,
25316 a command may change the selected thread. Although such changes can
25317 be included in command response, using notification allows for more
25318 orthogonal frontend design.
25322 There's no guarantee that whenever an MI command reports an error,
25323 @value{GDBN} or the target are in any specific state, and especially,
25324 the state is not reverted to the state before the MI command was
25325 processed. Therefore, whenever an MI command results in an error,
25326 we recommend that the frontend refreshes all the information shown in
25327 the user interface.
25331 * Context management::
25332 * Asynchronous and non-stop modes::
25336 @node Context management
25337 @subsection Context management
25339 @subsubsection Threads and Frames
25341 In most cases when @value{GDBN} accesses the target, this access is
25342 done in context of a specific thread and frame (@pxref{Frames}).
25343 Often, even when accessing global data, the target requires that a thread
25344 be specified. The CLI interface maintains the selected thread and frame,
25345 and supplies them to target on each command. This is convenient,
25346 because a command line user would not want to specify that information
25347 explicitly on each command, and because user interacts with
25348 @value{GDBN} via a single terminal, so no confusion is possible as
25349 to what thread and frame are the current ones.
25351 In the case of MI, the concept of selected thread and frame is less
25352 useful. First, a frontend can easily remember this information
25353 itself. Second, a graphical frontend can have more than one window,
25354 each one used for debugging a different thread, and the frontend might
25355 want to access additional threads for internal purposes. This
25356 increases the risk that by relying on implicitly selected thread, the
25357 frontend may be operating on a wrong one. Therefore, each MI command
25358 should explicitly specify which thread and frame to operate on. To
25359 make it possible, each MI command accepts the @samp{--thread} and
25360 @samp{--frame} options, the value to each is @value{GDBN} identifier
25361 for thread and frame to operate on.
25363 Usually, each top-level window in a frontend allows the user to select
25364 a thread and a frame, and remembers the user selection for further
25365 operations. However, in some cases @value{GDBN} may suggest that the
25366 current thread be changed. For example, when stopping on a breakpoint
25367 it is reasonable to switch to the thread where breakpoint is hit. For
25368 another example, if the user issues the CLI @samp{thread} command via
25369 the frontend, it is desirable to change the frontend's selected thread to the
25370 one specified by user. @value{GDBN} communicates the suggestion to
25371 change current thread using the @samp{=thread-selected} notification.
25372 No such notification is available for the selected frame at the moment.
25374 Note that historically, MI shares the selected thread with CLI, so
25375 frontends used the @code{-thread-select} to execute commands in the
25376 right context. However, getting this to work right is cumbersome. The
25377 simplest way is for frontend to emit @code{-thread-select} command
25378 before every command. This doubles the number of commands that need
25379 to be sent. The alternative approach is to suppress @code{-thread-select}
25380 if the selected thread in @value{GDBN} is supposed to be identical to the
25381 thread the frontend wants to operate on. However, getting this
25382 optimization right can be tricky. In particular, if the frontend
25383 sends several commands to @value{GDBN}, and one of the commands changes the
25384 selected thread, then the behaviour of subsequent commands will
25385 change. So, a frontend should either wait for response from such
25386 problematic commands, or explicitly add @code{-thread-select} for
25387 all subsequent commands. No frontend is known to do this exactly
25388 right, so it is suggested to just always pass the @samp{--thread} and
25389 @samp{--frame} options.
25391 @subsubsection Language
25393 The execution of several commands depends on which language is selected.
25394 By default, the current language (@pxref{show language}) is used.
25395 But for commands known to be language-sensitive, it is recommended
25396 to use the @samp{--language} option. This option takes one argument,
25397 which is the name of the language to use while executing the command.
25401 -data-evaluate-expression --language c "sizeof (void*)"
25406 The valid language names are the same names accepted by the
25407 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25408 @samp{local} or @samp{unknown}.
25410 @node Asynchronous and non-stop modes
25411 @subsection Asynchronous command execution and non-stop mode
25413 On some targets, @value{GDBN} is capable of processing MI commands
25414 even while the target is running. This is called @dfn{asynchronous
25415 command execution} (@pxref{Background Execution}). The frontend may
25416 specify a preferrence for asynchronous execution using the
25417 @code{-gdb-set mi-async 1} command, which should be emitted before
25418 either running the executable or attaching to the target. After the
25419 frontend has started the executable or attached to the target, it can
25420 find if asynchronous execution is enabled using the
25421 @code{-list-target-features} command.
25424 @item -gdb-set mi-async on
25425 @item -gdb-set mi-async off
25426 Set whether MI is in asynchronous mode.
25428 When @code{off}, which is the default, MI execution commands (e.g.,
25429 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25430 for the program to stop before processing further commands.
25432 When @code{on}, MI execution commands are background execution
25433 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25434 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25435 MI commands even while the target is running.
25437 @item -gdb-show mi-async
25438 Show whether MI asynchronous mode is enabled.
25441 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25442 @code{target-async} instead of @code{mi-async}, and it had the effect
25443 of both putting MI in asynchronous mode and making CLI background
25444 commands possible. CLI background commands are now always possible
25445 ``out of the box'' if the target supports them. The old spelling is
25446 kept as a deprecated alias for backwards compatibility.
25448 Even if @value{GDBN} can accept a command while target is running,
25449 many commands that access the target do not work when the target is
25450 running. Therefore, asynchronous command execution is most useful
25451 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25452 it is possible to examine the state of one thread, while other threads
25455 When a given thread is running, MI commands that try to access the
25456 target in the context of that thread may not work, or may work only on
25457 some targets. In particular, commands that try to operate on thread's
25458 stack will not work, on any target. Commands that read memory, or
25459 modify breakpoints, may work or not work, depending on the target. Note
25460 that even commands that operate on global state, such as @code{print},
25461 @code{set}, and breakpoint commands, still access the target in the
25462 context of a specific thread, so frontend should try to find a
25463 stopped thread and perform the operation on that thread (using the
25464 @samp{--thread} option).
25466 Which commands will work in the context of a running thread is
25467 highly target dependent. However, the two commands
25468 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25469 to find the state of a thread, will always work.
25471 @node Thread groups
25472 @subsection Thread groups
25473 @value{GDBN} may be used to debug several processes at the same time.
25474 On some platfroms, @value{GDBN} may support debugging of several
25475 hardware systems, each one having several cores with several different
25476 processes running on each core. This section describes the MI
25477 mechanism to support such debugging scenarios.
25479 The key observation is that regardless of the structure of the
25480 target, MI can have a global list of threads, because most commands that
25481 accept the @samp{--thread} option do not need to know what process that
25482 thread belongs to. Therefore, it is not necessary to introduce
25483 neither additional @samp{--process} option, nor an notion of the
25484 current process in the MI interface. The only strictly new feature
25485 that is required is the ability to find how the threads are grouped
25488 To allow the user to discover such grouping, and to support arbitrary
25489 hierarchy of machines/cores/processes, MI introduces the concept of a
25490 @dfn{thread group}. Thread group is a collection of threads and other
25491 thread groups. A thread group always has a string identifier, a type,
25492 and may have additional attributes specific to the type. A new
25493 command, @code{-list-thread-groups}, returns the list of top-level
25494 thread groups, which correspond to processes that @value{GDBN} is
25495 debugging at the moment. By passing an identifier of a thread group
25496 to the @code{-list-thread-groups} command, it is possible to obtain
25497 the members of specific thread group.
25499 To allow the user to easily discover processes, and other objects, he
25500 wishes to debug, a concept of @dfn{available thread group} is
25501 introduced. Available thread group is an thread group that
25502 @value{GDBN} is not debugging, but that can be attached to, using the
25503 @code{-target-attach} command. The list of available top-level thread
25504 groups can be obtained using @samp{-list-thread-groups --available}.
25505 In general, the content of a thread group may be only retrieved only
25506 after attaching to that thread group.
25508 Thread groups are related to inferiors (@pxref{Inferiors and
25509 Programs}). Each inferior corresponds to a thread group of a special
25510 type @samp{process}, and some additional operations are permitted on
25511 such thread groups.
25513 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25514 @node GDB/MI Command Syntax
25515 @section @sc{gdb/mi} Command Syntax
25518 * GDB/MI Input Syntax::
25519 * GDB/MI Output Syntax::
25522 @node GDB/MI Input Syntax
25523 @subsection @sc{gdb/mi} Input Syntax
25525 @cindex input syntax for @sc{gdb/mi}
25526 @cindex @sc{gdb/mi}, input syntax
25528 @item @var{command} @expansion{}
25529 @code{@var{cli-command} | @var{mi-command}}
25531 @item @var{cli-command} @expansion{}
25532 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25533 @var{cli-command} is any existing @value{GDBN} CLI command.
25535 @item @var{mi-command} @expansion{}
25536 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25537 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25539 @item @var{token} @expansion{}
25540 "any sequence of digits"
25542 @item @var{option} @expansion{}
25543 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25545 @item @var{parameter} @expansion{}
25546 @code{@var{non-blank-sequence} | @var{c-string}}
25548 @item @var{operation} @expansion{}
25549 @emph{any of the operations described in this chapter}
25551 @item @var{non-blank-sequence} @expansion{}
25552 @emph{anything, provided it doesn't contain special characters such as
25553 "-", @var{nl}, """ and of course " "}
25555 @item @var{c-string} @expansion{}
25556 @code{""" @var{seven-bit-iso-c-string-content} """}
25558 @item @var{nl} @expansion{}
25567 The CLI commands are still handled by the @sc{mi} interpreter; their
25568 output is described below.
25571 The @code{@var{token}}, when present, is passed back when the command
25575 Some @sc{mi} commands accept optional arguments as part of the parameter
25576 list. Each option is identified by a leading @samp{-} (dash) and may be
25577 followed by an optional argument parameter. Options occur first in the
25578 parameter list and can be delimited from normal parameters using
25579 @samp{--} (this is useful when some parameters begin with a dash).
25586 We want easy access to the existing CLI syntax (for debugging).
25589 We want it to be easy to spot a @sc{mi} operation.
25592 @node GDB/MI Output Syntax
25593 @subsection @sc{gdb/mi} Output Syntax
25595 @cindex output syntax of @sc{gdb/mi}
25596 @cindex @sc{gdb/mi}, output syntax
25597 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25598 followed, optionally, by a single result record. This result record
25599 is for the most recent command. The sequence of output records is
25600 terminated by @samp{(gdb)}.
25602 If an input command was prefixed with a @code{@var{token}} then the
25603 corresponding output for that command will also be prefixed by that same
25607 @item @var{output} @expansion{}
25608 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25610 @item @var{result-record} @expansion{}
25611 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25613 @item @var{out-of-band-record} @expansion{}
25614 @code{@var{async-record} | @var{stream-record}}
25616 @item @var{async-record} @expansion{}
25617 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25619 @item @var{exec-async-output} @expansion{}
25620 @code{[ @var{token} ] "*" @var{async-output nl}}
25622 @item @var{status-async-output} @expansion{}
25623 @code{[ @var{token} ] "+" @var{async-output nl}}
25625 @item @var{notify-async-output} @expansion{}
25626 @code{[ @var{token} ] "=" @var{async-output nl}}
25628 @item @var{async-output} @expansion{}
25629 @code{@var{async-class} ( "," @var{result} )*}
25631 @item @var{result-class} @expansion{}
25632 @code{"done" | "running" | "connected" | "error" | "exit"}
25634 @item @var{async-class} @expansion{}
25635 @code{"stopped" | @var{others}} (where @var{others} will be added
25636 depending on the needs---this is still in development).
25638 @item @var{result} @expansion{}
25639 @code{ @var{variable} "=" @var{value}}
25641 @item @var{variable} @expansion{}
25642 @code{ @var{string} }
25644 @item @var{value} @expansion{}
25645 @code{ @var{const} | @var{tuple} | @var{list} }
25647 @item @var{const} @expansion{}
25648 @code{@var{c-string}}
25650 @item @var{tuple} @expansion{}
25651 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25653 @item @var{list} @expansion{}
25654 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25655 @var{result} ( "," @var{result} )* "]" }
25657 @item @var{stream-record} @expansion{}
25658 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25660 @item @var{console-stream-output} @expansion{}
25661 @code{"~" @var{c-string nl}}
25663 @item @var{target-stream-output} @expansion{}
25664 @code{"@@" @var{c-string nl}}
25666 @item @var{log-stream-output} @expansion{}
25667 @code{"&" @var{c-string nl}}
25669 @item @var{nl} @expansion{}
25672 @item @var{token} @expansion{}
25673 @emph{any sequence of digits}.
25681 All output sequences end in a single line containing a period.
25684 The @code{@var{token}} is from the corresponding request. Note that
25685 for all async output, while the token is allowed by the grammar and
25686 may be output by future versions of @value{GDBN} for select async
25687 output messages, it is generally omitted. Frontends should treat
25688 all async output as reporting general changes in the state of the
25689 target and there should be no need to associate async output to any
25693 @cindex status output in @sc{gdb/mi}
25694 @var{status-async-output} contains on-going status information about the
25695 progress of a slow operation. It can be discarded. All status output is
25696 prefixed by @samp{+}.
25699 @cindex async output in @sc{gdb/mi}
25700 @var{exec-async-output} contains asynchronous state change on the target
25701 (stopped, started, disappeared). All async output is prefixed by
25705 @cindex notify output in @sc{gdb/mi}
25706 @var{notify-async-output} contains supplementary information that the
25707 client should handle (e.g., a new breakpoint information). All notify
25708 output is prefixed by @samp{=}.
25711 @cindex console output in @sc{gdb/mi}
25712 @var{console-stream-output} is output that should be displayed as is in the
25713 console. It is the textual response to a CLI command. All the console
25714 output is prefixed by @samp{~}.
25717 @cindex target output in @sc{gdb/mi}
25718 @var{target-stream-output} is the output produced by the target program.
25719 All the target output is prefixed by @samp{@@}.
25722 @cindex log output in @sc{gdb/mi}
25723 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25724 instance messages that should be displayed as part of an error log. All
25725 the log output is prefixed by @samp{&}.
25728 @cindex list output in @sc{gdb/mi}
25729 New @sc{gdb/mi} commands should only output @var{lists} containing
25735 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25736 details about the various output records.
25738 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25739 @node GDB/MI Compatibility with CLI
25740 @section @sc{gdb/mi} Compatibility with CLI
25742 @cindex compatibility, @sc{gdb/mi} and CLI
25743 @cindex @sc{gdb/mi}, compatibility with CLI
25745 For the developers convenience CLI commands can be entered directly,
25746 but there may be some unexpected behaviour. For example, commands
25747 that query the user will behave as if the user replied yes, breakpoint
25748 command lists are not executed and some CLI commands, such as
25749 @code{if}, @code{when} and @code{define}, prompt for further input with
25750 @samp{>}, which is not valid MI output.
25752 This feature may be removed at some stage in the future and it is
25753 recommended that front ends use the @code{-interpreter-exec} command
25754 (@pxref{-interpreter-exec}).
25756 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25757 @node GDB/MI Development and Front Ends
25758 @section @sc{gdb/mi} Development and Front Ends
25759 @cindex @sc{gdb/mi} development
25761 The application which takes the MI output and presents the state of the
25762 program being debugged to the user is called a @dfn{front end}.
25764 Although @sc{gdb/mi} is still incomplete, it is currently being used
25765 by a variety of front ends to @value{GDBN}. This makes it difficult
25766 to introduce new functionality without breaking existing usage. This
25767 section tries to minimize the problems by describing how the protocol
25770 Some changes in MI need not break a carefully designed front end, and
25771 for these the MI version will remain unchanged. The following is a
25772 list of changes that may occur within one level, so front ends should
25773 parse MI output in a way that can handle them:
25777 New MI commands may be added.
25780 New fields may be added to the output of any MI command.
25783 The range of values for fields with specified values, e.g.,
25784 @code{in_scope} (@pxref{-var-update}) may be extended.
25786 @c The format of field's content e.g type prefix, may change so parse it
25787 @c at your own risk. Yes, in general?
25789 @c The order of fields may change? Shouldn't really matter but it might
25790 @c resolve inconsistencies.
25793 If the changes are likely to break front ends, the MI version level
25794 will be increased by one. This will allow the front end to parse the
25795 output according to the MI version. Apart from mi0, new versions of
25796 @value{GDBN} will not support old versions of MI and it will be the
25797 responsibility of the front end to work with the new one.
25799 @c Starting with mi3, add a new command -mi-version that prints the MI
25802 The best way to avoid unexpected changes in MI that might break your front
25803 end is to make your project known to @value{GDBN} developers and
25804 follow development on @email{gdb@@sourceware.org} and
25805 @email{gdb-patches@@sourceware.org}.
25806 @cindex mailing lists
25808 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25809 @node GDB/MI Output Records
25810 @section @sc{gdb/mi} Output Records
25813 * GDB/MI Result Records::
25814 * GDB/MI Stream Records::
25815 * GDB/MI Async Records::
25816 * GDB/MI Breakpoint Information::
25817 * GDB/MI Frame Information::
25818 * GDB/MI Thread Information::
25819 * GDB/MI Ada Exception Information::
25822 @node GDB/MI Result Records
25823 @subsection @sc{gdb/mi} Result Records
25825 @cindex result records in @sc{gdb/mi}
25826 @cindex @sc{gdb/mi}, result records
25827 In addition to a number of out-of-band notifications, the response to a
25828 @sc{gdb/mi} command includes one of the following result indications:
25832 @item "^done" [ "," @var{results} ]
25833 The synchronous operation was successful, @code{@var{results}} are the return
25838 This result record is equivalent to @samp{^done}. Historically, it
25839 was output instead of @samp{^done} if the command has resumed the
25840 target. This behaviour is maintained for backward compatibility, but
25841 all frontends should treat @samp{^done} and @samp{^running}
25842 identically and rely on the @samp{*running} output record to determine
25843 which threads are resumed.
25847 @value{GDBN} has connected to a remote target.
25849 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25851 The operation failed. The @code{msg=@var{c-string}} variable contains
25852 the corresponding error message.
25854 If present, the @code{code=@var{c-string}} variable provides an error
25855 code on which consumers can rely on to detect the corresponding
25856 error condition. At present, only one error code is defined:
25859 @item "undefined-command"
25860 Indicates that the command causing the error does not exist.
25865 @value{GDBN} has terminated.
25869 @node GDB/MI Stream Records
25870 @subsection @sc{gdb/mi} Stream Records
25872 @cindex @sc{gdb/mi}, stream records
25873 @cindex stream records in @sc{gdb/mi}
25874 @value{GDBN} internally maintains a number of output streams: the console, the
25875 target, and the log. The output intended for each of these streams is
25876 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25878 Each stream record begins with a unique @dfn{prefix character} which
25879 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25880 Syntax}). In addition to the prefix, each stream record contains a
25881 @code{@var{string-output}}. This is either raw text (with an implicit new
25882 line) or a quoted C string (which does not contain an implicit newline).
25885 @item "~" @var{string-output}
25886 The console output stream contains text that should be displayed in the
25887 CLI console window. It contains the textual responses to CLI commands.
25889 @item "@@" @var{string-output}
25890 The target output stream contains any textual output from the running
25891 target. This is only present when GDB's event loop is truly
25892 asynchronous, which is currently only the case for remote targets.
25894 @item "&" @var{string-output}
25895 The log stream contains debugging messages being produced by @value{GDBN}'s
25899 @node GDB/MI Async Records
25900 @subsection @sc{gdb/mi} Async Records
25902 @cindex async records in @sc{gdb/mi}
25903 @cindex @sc{gdb/mi}, async records
25904 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25905 additional changes that have occurred. Those changes can either be a
25906 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25907 target activity (e.g., target stopped).
25909 The following is the list of possible async records:
25913 @item *running,thread-id="@var{thread}"
25914 The target is now running. The @var{thread} field tells which
25915 specific thread is now running, and can be @samp{all} if all threads
25916 are running. The frontend should assume that no interaction with a
25917 running thread is possible after this notification is produced.
25918 The frontend should not assume that this notification is output
25919 only once for any command. @value{GDBN} may emit this notification
25920 several times, either for different threads, because it cannot resume
25921 all threads together, or even for a single thread, if the thread must
25922 be stepped though some code before letting it run freely.
25924 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25925 The target has stopped. The @var{reason} field can have one of the
25929 @item breakpoint-hit
25930 A breakpoint was reached.
25931 @item watchpoint-trigger
25932 A watchpoint was triggered.
25933 @item read-watchpoint-trigger
25934 A read watchpoint was triggered.
25935 @item access-watchpoint-trigger
25936 An access watchpoint was triggered.
25937 @item function-finished
25938 An -exec-finish or similar CLI command was accomplished.
25939 @item location-reached
25940 An -exec-until or similar CLI command was accomplished.
25941 @item watchpoint-scope
25942 A watchpoint has gone out of scope.
25943 @item end-stepping-range
25944 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25945 similar CLI command was accomplished.
25946 @item exited-signalled
25947 The inferior exited because of a signal.
25949 The inferior exited.
25950 @item exited-normally
25951 The inferior exited normally.
25952 @item signal-received
25953 A signal was received by the inferior.
25955 The inferior has stopped due to a library being loaded or unloaded.
25956 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25957 set or when a @code{catch load} or @code{catch unload} catchpoint is
25958 in use (@pxref{Set Catchpoints}).
25960 The inferior has forked. This is reported when @code{catch fork}
25961 (@pxref{Set Catchpoints}) has been used.
25963 The inferior has vforked. This is reported in when @code{catch vfork}
25964 (@pxref{Set Catchpoints}) has been used.
25965 @item syscall-entry
25966 The inferior entered a system call. This is reported when @code{catch
25967 syscall} (@pxref{Set Catchpoints}) has been used.
25968 @item syscall-return
25969 The inferior returned from a system call. This is reported when
25970 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
25972 The inferior called @code{exec}. This is reported when @code{catch exec}
25973 (@pxref{Set Catchpoints}) has been used.
25976 The @var{id} field identifies the thread that directly caused the stop
25977 -- for example by hitting a breakpoint. Depending on whether all-stop
25978 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25979 stop all threads, or only the thread that directly triggered the stop.
25980 If all threads are stopped, the @var{stopped} field will have the
25981 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25982 field will be a list of thread identifiers. Presently, this list will
25983 always include a single thread, but frontend should be prepared to see
25984 several threads in the list. The @var{core} field reports the
25985 processor core on which the stop event has happened. This field may be absent
25986 if such information is not available.
25988 @item =thread-group-added,id="@var{id}"
25989 @itemx =thread-group-removed,id="@var{id}"
25990 A thread group was either added or removed. The @var{id} field
25991 contains the @value{GDBN} identifier of the thread group. When a thread
25992 group is added, it generally might not be associated with a running
25993 process. When a thread group is removed, its id becomes invalid and
25994 cannot be used in any way.
25996 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25997 A thread group became associated with a running program,
25998 either because the program was just started or the thread group
25999 was attached to a program. The @var{id} field contains the
26000 @value{GDBN} identifier of the thread group. The @var{pid} field
26001 contains process identifier, specific to the operating system.
26003 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26004 A thread group is no longer associated with a running program,
26005 either because the program has exited, or because it was detached
26006 from. The @var{id} field contains the @value{GDBN} identifier of the
26007 thread group. The @var{code} field is the exit code of the inferior; it exists
26008 only when the inferior exited with some code.
26010 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26011 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26012 A thread either was created, or has exited. The @var{id} field
26013 contains the @value{GDBN} identifier of the thread. The @var{gid}
26014 field identifies the thread group this thread belongs to.
26016 @item =thread-selected,id="@var{id}"
26017 Informs that the selected thread was changed as result of the last
26018 command. This notification is not emitted as result of @code{-thread-select}
26019 command but is emitted whenever an MI command that is not documented
26020 to change the selected thread actually changes it. In particular,
26021 invoking, directly or indirectly (via user-defined command), the CLI
26022 @code{thread} command, will generate this notification.
26024 We suggest that in response to this notification, front ends
26025 highlight the selected thread and cause subsequent commands to apply to
26028 @item =library-loaded,...
26029 Reports that a new library file was loaded by the program. This
26030 notification has 4 fields---@var{id}, @var{target-name},
26031 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26032 opaque identifier of the library. For remote debugging case,
26033 @var{target-name} and @var{host-name} fields give the name of the
26034 library file on the target, and on the host respectively. For native
26035 debugging, both those fields have the same value. The
26036 @var{symbols-loaded} field is emitted only for backward compatibility
26037 and should not be relied on to convey any useful information. The
26038 @var{thread-group} field, if present, specifies the id of the thread
26039 group in whose context the library was loaded. If the field is
26040 absent, it means the library was loaded in the context of all present
26043 @item =library-unloaded,...
26044 Reports that a library was unloaded by the program. This notification
26045 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26046 the same meaning as for the @code{=library-loaded} notification.
26047 The @var{thread-group} field, if present, specifies the id of the
26048 thread group in whose context the library was unloaded. If the field is
26049 absent, it means the library was unloaded in the context of all present
26052 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26053 @itemx =traceframe-changed,end
26054 Reports that the trace frame was changed and its new number is
26055 @var{tfnum}. The number of the tracepoint associated with this trace
26056 frame is @var{tpnum}.
26058 @item =tsv-created,name=@var{name},initial=@var{initial}
26059 Reports that the new trace state variable @var{name} is created with
26060 initial value @var{initial}.
26062 @item =tsv-deleted,name=@var{name}
26063 @itemx =tsv-deleted
26064 Reports that the trace state variable @var{name} is deleted or all
26065 trace state variables are deleted.
26067 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26068 Reports that the trace state variable @var{name} is modified with
26069 the initial value @var{initial}. The current value @var{current} of
26070 trace state variable is optional and is reported if the current
26071 value of trace state variable is known.
26073 @item =breakpoint-created,bkpt=@{...@}
26074 @itemx =breakpoint-modified,bkpt=@{...@}
26075 @itemx =breakpoint-deleted,id=@var{number}
26076 Reports that a breakpoint was created, modified, or deleted,
26077 respectively. Only user-visible breakpoints are reported to the MI
26080 The @var{bkpt} argument is of the same form as returned by the various
26081 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26082 @var{number} is the ordinal number of the breakpoint.
26084 Note that if a breakpoint is emitted in the result record of a
26085 command, then it will not also be emitted in an async record.
26087 @item =record-started,thread-group="@var{id}"
26088 @itemx =record-stopped,thread-group="@var{id}"
26089 Execution log recording was either started or stopped on an
26090 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26091 group corresponding to the affected inferior.
26093 @item =cmd-param-changed,param=@var{param},value=@var{value}
26094 Reports that a parameter of the command @code{set @var{param}} is
26095 changed to @var{value}. In the multi-word @code{set} command,
26096 the @var{param} is the whole parameter list to @code{set} command.
26097 For example, In command @code{set check type on}, @var{param}
26098 is @code{check type} and @var{value} is @code{on}.
26100 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26101 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26102 written in an inferior. The @var{id} is the identifier of the
26103 thread group corresponding to the affected inferior. The optional
26104 @code{type="code"} part is reported if the memory written to holds
26108 @node GDB/MI Breakpoint Information
26109 @subsection @sc{gdb/mi} Breakpoint Information
26111 When @value{GDBN} reports information about a breakpoint, a
26112 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26117 The breakpoint number. For a breakpoint that represents one location
26118 of a multi-location breakpoint, this will be a dotted pair, like
26122 The type of the breakpoint. For ordinary breakpoints this will be
26123 @samp{breakpoint}, but many values are possible.
26126 If the type of the breakpoint is @samp{catchpoint}, then this
26127 indicates the exact type of catchpoint.
26130 This is the breakpoint disposition---either @samp{del}, meaning that
26131 the breakpoint will be deleted at the next stop, or @samp{keep},
26132 meaning that the breakpoint will not be deleted.
26135 This indicates whether the breakpoint is enabled, in which case the
26136 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26137 Note that this is not the same as the field @code{enable}.
26140 The address of the breakpoint. This may be a hexidecimal number,
26141 giving the address; or the string @samp{<PENDING>}, for a pending
26142 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26143 multiple locations. This field will not be present if no address can
26144 be determined. For example, a watchpoint does not have an address.
26147 If known, the function in which the breakpoint appears.
26148 If not known, this field is not present.
26151 The name of the source file which contains this function, if known.
26152 If not known, this field is not present.
26155 The full file name of the source file which contains this function, if
26156 known. If not known, this field is not present.
26159 The line number at which this breakpoint appears, if known.
26160 If not known, this field is not present.
26163 If the source file is not known, this field may be provided. If
26164 provided, this holds the address of the breakpoint, possibly followed
26168 If this breakpoint is pending, this field is present and holds the
26169 text used to set the breakpoint, as entered by the user.
26172 Where this breakpoint's condition is evaluated, either @samp{host} or
26176 If this is a thread-specific breakpoint, then this identifies the
26177 thread in which the breakpoint can trigger.
26180 If this breakpoint is restricted to a particular Ada task, then this
26181 field will hold the task identifier.
26184 If the breakpoint is conditional, this is the condition expression.
26187 The ignore count of the breakpoint.
26190 The enable count of the breakpoint.
26192 @item traceframe-usage
26195 @item static-tracepoint-marker-string-id
26196 For a static tracepoint, the name of the static tracepoint marker.
26199 For a masked watchpoint, this is the mask.
26202 A tracepoint's pass count.
26204 @item original-location
26205 The location of the breakpoint as originally specified by the user.
26206 This field is optional.
26209 The number of times the breakpoint has been hit.
26212 This field is only given for tracepoints. This is either @samp{y},
26213 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26217 Some extra data, the exact contents of which are type-dependent.
26221 For example, here is what the output of @code{-break-insert}
26222 (@pxref{GDB/MI Breakpoint Commands}) might be:
26225 -> -break-insert main
26226 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26227 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26228 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26233 @node GDB/MI Frame Information
26234 @subsection @sc{gdb/mi} Frame Information
26236 Response from many MI commands includes an information about stack
26237 frame. This information is a tuple that may have the following
26242 The level of the stack frame. The innermost frame has the level of
26243 zero. This field is always present.
26246 The name of the function corresponding to the frame. This field may
26247 be absent if @value{GDBN} is unable to determine the function name.
26250 The code address for the frame. This field is always present.
26253 The name of the source files that correspond to the frame's code
26254 address. This field may be absent.
26257 The source line corresponding to the frames' code address. This field
26261 The name of the binary file (either executable or shared library) the
26262 corresponds to the frame's code address. This field may be absent.
26266 @node GDB/MI Thread Information
26267 @subsection @sc{gdb/mi} Thread Information
26269 Whenever @value{GDBN} has to report an information about a thread, it
26270 uses a tuple with the following fields:
26274 The numeric id assigned to the thread by @value{GDBN}. This field is
26278 Target-specific string identifying the thread. This field is always present.
26281 Additional information about the thread provided by the target.
26282 It is supposed to be human-readable and not interpreted by the
26283 frontend. This field is optional.
26286 Either @samp{stopped} or @samp{running}, depending on whether the
26287 thread is presently running. This field is always present.
26290 The value of this field is an integer number of the processor core the
26291 thread was last seen on. This field is optional.
26294 @node GDB/MI Ada Exception Information
26295 @subsection @sc{gdb/mi} Ada Exception Information
26297 Whenever a @code{*stopped} record is emitted because the program
26298 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26299 @value{GDBN} provides the name of the exception that was raised via
26300 the @code{exception-name} field.
26302 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26303 @node GDB/MI Simple Examples
26304 @section Simple Examples of @sc{gdb/mi} Interaction
26305 @cindex @sc{gdb/mi}, simple examples
26307 This subsection presents several simple examples of interaction using
26308 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26309 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26310 the output received from @sc{gdb/mi}.
26312 Note the line breaks shown in the examples are here only for
26313 readability, they don't appear in the real output.
26315 @subheading Setting a Breakpoint
26317 Setting a breakpoint generates synchronous output which contains detailed
26318 information of the breakpoint.
26321 -> -break-insert main
26322 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26323 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26324 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26329 @subheading Program Execution
26331 Program execution generates asynchronous records and MI gives the
26332 reason that execution stopped.
26338 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26339 frame=@{addr="0x08048564",func="main",
26340 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26341 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26346 <- *stopped,reason="exited-normally"
26350 @subheading Quitting @value{GDBN}
26352 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26360 Please note that @samp{^exit} is printed immediately, but it might
26361 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26362 performs necessary cleanups, including killing programs being debugged
26363 or disconnecting from debug hardware, so the frontend should wait till
26364 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26365 fails to exit in reasonable time.
26367 @subheading A Bad Command
26369 Here's what happens if you pass a non-existent command:
26373 <- ^error,msg="Undefined MI command: rubbish"
26378 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26379 @node GDB/MI Command Description Format
26380 @section @sc{gdb/mi} Command Description Format
26382 The remaining sections describe blocks of commands. Each block of
26383 commands is laid out in a fashion similar to this section.
26385 @subheading Motivation
26387 The motivation for this collection of commands.
26389 @subheading Introduction
26391 A brief introduction to this collection of commands as a whole.
26393 @subheading Commands
26395 For each command in the block, the following is described:
26397 @subsubheading Synopsis
26400 -command @var{args}@dots{}
26403 @subsubheading Result
26405 @subsubheading @value{GDBN} Command
26407 The corresponding @value{GDBN} CLI command(s), if any.
26409 @subsubheading Example
26411 Example(s) formatted for readability. Some of the described commands have
26412 not been implemented yet and these are labeled N.A.@: (not available).
26415 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26416 @node GDB/MI Breakpoint Commands
26417 @section @sc{gdb/mi} Breakpoint Commands
26419 @cindex breakpoint commands for @sc{gdb/mi}
26420 @cindex @sc{gdb/mi}, breakpoint commands
26421 This section documents @sc{gdb/mi} commands for manipulating
26424 @subheading The @code{-break-after} Command
26425 @findex -break-after
26427 @subsubheading Synopsis
26430 -break-after @var{number} @var{count}
26433 The breakpoint number @var{number} is not in effect until it has been
26434 hit @var{count} times. To see how this is reflected in the output of
26435 the @samp{-break-list} command, see the description of the
26436 @samp{-break-list} command below.
26438 @subsubheading @value{GDBN} Command
26440 The corresponding @value{GDBN} command is @samp{ignore}.
26442 @subsubheading Example
26447 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26448 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26449 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26457 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26458 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26459 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26460 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26461 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26462 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26463 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26464 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26465 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26466 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26471 @subheading The @code{-break-catch} Command
26472 @findex -break-catch
26475 @subheading The @code{-break-commands} Command
26476 @findex -break-commands
26478 @subsubheading Synopsis
26481 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26484 Specifies the CLI commands that should be executed when breakpoint
26485 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26486 are the commands. If no command is specified, any previously-set
26487 commands are cleared. @xref{Break Commands}. Typical use of this
26488 functionality is tracing a program, that is, printing of values of
26489 some variables whenever breakpoint is hit and then continuing.
26491 @subsubheading @value{GDBN} Command
26493 The corresponding @value{GDBN} command is @samp{commands}.
26495 @subsubheading Example
26500 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26501 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26502 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26505 -break-commands 1 "print v" "continue"
26510 @subheading The @code{-break-condition} Command
26511 @findex -break-condition
26513 @subsubheading Synopsis
26516 -break-condition @var{number} @var{expr}
26519 Breakpoint @var{number} will stop the program only if the condition in
26520 @var{expr} is true. The condition becomes part of the
26521 @samp{-break-list} output (see the description of the @samp{-break-list}
26524 @subsubheading @value{GDBN} Command
26526 The corresponding @value{GDBN} command is @samp{condition}.
26528 @subsubheading Example
26532 -break-condition 1 1
26536 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26537 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26538 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26539 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26540 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26541 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26542 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26543 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26544 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26545 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26549 @subheading The @code{-break-delete} Command
26550 @findex -break-delete
26552 @subsubheading Synopsis
26555 -break-delete ( @var{breakpoint} )+
26558 Delete the breakpoint(s) whose number(s) are specified in the argument
26559 list. This is obviously reflected in the breakpoint list.
26561 @subsubheading @value{GDBN} Command
26563 The corresponding @value{GDBN} command is @samp{delete}.
26565 @subsubheading Example
26573 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26574 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26575 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26576 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26577 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26578 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26579 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26584 @subheading The @code{-break-disable} Command
26585 @findex -break-disable
26587 @subsubheading Synopsis
26590 -break-disable ( @var{breakpoint} )+
26593 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26594 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26596 @subsubheading @value{GDBN} Command
26598 The corresponding @value{GDBN} command is @samp{disable}.
26600 @subsubheading Example
26608 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26609 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26610 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26611 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26612 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26613 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26614 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26615 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26616 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26617 line="5",thread-groups=["i1"],times="0"@}]@}
26621 @subheading The @code{-break-enable} Command
26622 @findex -break-enable
26624 @subsubheading Synopsis
26627 -break-enable ( @var{breakpoint} )+
26630 Enable (previously disabled) @var{breakpoint}(s).
26632 @subsubheading @value{GDBN} Command
26634 The corresponding @value{GDBN} command is @samp{enable}.
26636 @subsubheading Example
26644 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26645 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26646 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26647 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26648 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26649 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26650 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26651 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26652 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26653 line="5",thread-groups=["i1"],times="0"@}]@}
26657 @subheading The @code{-break-info} Command
26658 @findex -break-info
26660 @subsubheading Synopsis
26663 -break-info @var{breakpoint}
26667 Get information about a single breakpoint.
26669 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26670 Information}, for details on the format of each breakpoint in the
26673 @subsubheading @value{GDBN} Command
26675 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26677 @subsubheading Example
26680 @subheading The @code{-break-insert} Command
26681 @findex -break-insert
26682 @anchor{-break-insert}
26684 @subsubheading Synopsis
26687 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26688 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26689 [ -p @var{thread-id} ] [ @var{location} ]
26693 If specified, @var{location}, can be one of:
26696 @item linespec location
26697 A linespec location. @xref{Linespec Locations}.
26699 @item explicit location
26700 An explicit location. @sc{gdb/mi} explicit locations are
26701 analogous to the CLI's explicit locations using the option names
26702 listed below. @xref{Explicit Locations}.
26705 @item --source @var{filename}
26706 The source file name of the location. This option requires the use
26707 of either @samp{--function} or @samp{--line}.
26709 @item --function @var{function}
26710 The name of a function or method.
26712 @item --label @var{label}
26713 The name of a label.
26715 @item --line @var{lineoffset}
26716 An absolute or relative line offset from the start of the location.
26719 @item address location
26720 An address location, *@var{address}. @xref{Address Locations}.
26724 The possible optional parameters of this command are:
26728 Insert a temporary breakpoint.
26730 Insert a hardware breakpoint.
26732 If @var{location} cannot be parsed (for example if it
26733 refers to unknown files or functions), create a pending
26734 breakpoint. Without this flag, @value{GDBN} will report
26735 an error, and won't create a breakpoint, if @var{location}
26738 Create a disabled breakpoint.
26740 Create a tracepoint. @xref{Tracepoints}. When this parameter
26741 is used together with @samp{-h}, a fast tracepoint is created.
26742 @item -c @var{condition}
26743 Make the breakpoint conditional on @var{condition}.
26744 @item -i @var{ignore-count}
26745 Initialize the @var{ignore-count}.
26746 @item -p @var{thread-id}
26747 Restrict the breakpoint to the specified @var{thread-id}.
26750 @subsubheading Result
26752 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26753 resulting breakpoint.
26755 Note: this format is open to change.
26756 @c An out-of-band breakpoint instead of part of the result?
26758 @subsubheading @value{GDBN} Command
26760 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26761 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26763 @subsubheading Example
26768 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26769 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26772 -break-insert -t foo
26773 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26774 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26778 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26779 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26780 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26781 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26782 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26783 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26784 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26785 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26786 addr="0x0001072c", func="main",file="recursive2.c",
26787 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26789 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26790 addr="0x00010774",func="foo",file="recursive2.c",
26791 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26794 @c -break-insert -r foo.*
26795 @c ~int foo(int, int);
26796 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26797 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26802 @subheading The @code{-dprintf-insert} Command
26803 @findex -dprintf-insert
26805 @subsubheading Synopsis
26808 -dprintf-insert [ -t ] [ -f ] [ -d ]
26809 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26810 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26815 If supplied, @var{location} may be specified the same way as for
26816 the @code{-break-insert} command. @xref{-break-insert}.
26818 The possible optional parameters of this command are:
26822 Insert a temporary breakpoint.
26824 If @var{location} cannot be parsed (for example, if it
26825 refers to unknown files or functions), create a pending
26826 breakpoint. Without this flag, @value{GDBN} will report
26827 an error, and won't create a breakpoint, if @var{location}
26830 Create a disabled breakpoint.
26831 @item -c @var{condition}
26832 Make the breakpoint conditional on @var{condition}.
26833 @item -i @var{ignore-count}
26834 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26835 to @var{ignore-count}.
26836 @item -p @var{thread-id}
26837 Restrict the breakpoint to the specified @var{thread-id}.
26840 @subsubheading Result
26842 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26843 resulting breakpoint.
26845 @c An out-of-band breakpoint instead of part of the result?
26847 @subsubheading @value{GDBN} Command
26849 The corresponding @value{GDBN} command is @samp{dprintf}.
26851 @subsubheading Example
26855 4-dprintf-insert foo "At foo entry\n"
26856 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26857 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26858 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26859 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26860 original-location="foo"@}
26862 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26863 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26864 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26865 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26866 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26867 original-location="mi-dprintf.c:26"@}
26871 @subheading The @code{-break-list} Command
26872 @findex -break-list
26874 @subsubheading Synopsis
26880 Displays the list of inserted breakpoints, showing the following fields:
26884 number of the breakpoint
26886 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26888 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26891 is the breakpoint enabled or no: @samp{y} or @samp{n}
26893 memory location at which the breakpoint is set
26895 logical location of the breakpoint, expressed by function name, file
26897 @item Thread-groups
26898 list of thread groups to which this breakpoint applies
26900 number of times the breakpoint has been hit
26903 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26904 @code{body} field is an empty list.
26906 @subsubheading @value{GDBN} Command
26908 The corresponding @value{GDBN} command is @samp{info break}.
26910 @subsubheading Example
26915 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26916 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26917 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26918 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26919 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26920 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26921 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26922 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26923 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26925 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26926 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26927 line="13",thread-groups=["i1"],times="0"@}]@}
26931 Here's an example of the result when there are no breakpoints:
26936 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26937 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26938 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26939 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26940 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26941 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26942 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26947 @subheading The @code{-break-passcount} Command
26948 @findex -break-passcount
26950 @subsubheading Synopsis
26953 -break-passcount @var{tracepoint-number} @var{passcount}
26956 Set the passcount for tracepoint @var{tracepoint-number} to
26957 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26958 is not a tracepoint, error is emitted. This corresponds to CLI
26959 command @samp{passcount}.
26961 @subheading The @code{-break-watch} Command
26962 @findex -break-watch
26964 @subsubheading Synopsis
26967 -break-watch [ -a | -r ]
26970 Create a watchpoint. With the @samp{-a} option it will create an
26971 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26972 read from or on a write to the memory location. With the @samp{-r}
26973 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26974 trigger only when the memory location is accessed for reading. Without
26975 either of the options, the watchpoint created is a regular watchpoint,
26976 i.e., it will trigger when the memory location is accessed for writing.
26977 @xref{Set Watchpoints, , Setting Watchpoints}.
26979 Note that @samp{-break-list} will report a single list of watchpoints and
26980 breakpoints inserted.
26982 @subsubheading @value{GDBN} Command
26984 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26987 @subsubheading Example
26989 Setting a watchpoint on a variable in the @code{main} function:
26994 ^done,wpt=@{number="2",exp="x"@}
26999 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27000 value=@{old="-268439212",new="55"@},
27001 frame=@{func="main",args=[],file="recursive2.c",
27002 fullname="/home/foo/bar/recursive2.c",line="5"@}
27006 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27007 the program execution twice: first for the variable changing value, then
27008 for the watchpoint going out of scope.
27013 ^done,wpt=@{number="5",exp="C"@}
27018 *stopped,reason="watchpoint-trigger",
27019 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27020 frame=@{func="callee4",args=[],
27021 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27022 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27027 *stopped,reason="watchpoint-scope",wpnum="5",
27028 frame=@{func="callee3",args=[@{name="strarg",
27029 value="0x11940 \"A string argument.\""@}],
27030 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27031 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27035 Listing breakpoints and watchpoints, at different points in the program
27036 execution. Note that once the watchpoint goes out of scope, it is
27042 ^done,wpt=@{number="2",exp="C"@}
27045 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27046 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27047 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27048 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27049 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27050 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27051 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27052 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27053 addr="0x00010734",func="callee4",
27054 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27055 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27057 bkpt=@{number="2",type="watchpoint",disp="keep",
27058 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27063 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27064 value=@{old="-276895068",new="3"@},
27065 frame=@{func="callee4",args=[],
27066 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27067 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27070 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27071 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27072 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27073 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27074 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27075 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27076 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27077 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27078 addr="0x00010734",func="callee4",
27079 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27080 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27082 bkpt=@{number="2",type="watchpoint",disp="keep",
27083 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27087 ^done,reason="watchpoint-scope",wpnum="2",
27088 frame=@{func="callee3",args=[@{name="strarg",
27089 value="0x11940 \"A string argument.\""@}],
27090 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27091 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27094 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27095 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27096 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27097 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27098 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27099 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27100 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27101 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27102 addr="0x00010734",func="callee4",
27103 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27104 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27105 thread-groups=["i1"],times="1"@}]@}
27110 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27111 @node GDB/MI Catchpoint Commands
27112 @section @sc{gdb/mi} Catchpoint Commands
27114 This section documents @sc{gdb/mi} commands for manipulating
27118 * Shared Library GDB/MI Catchpoint Commands::
27119 * Ada Exception GDB/MI Catchpoint Commands::
27122 @node Shared Library GDB/MI Catchpoint Commands
27123 @subsection Shared Library @sc{gdb/mi} Catchpoints
27125 @subheading The @code{-catch-load} Command
27126 @findex -catch-load
27128 @subsubheading Synopsis
27131 -catch-load [ -t ] [ -d ] @var{regexp}
27134 Add a catchpoint for library load events. If the @samp{-t} option is used,
27135 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27136 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27137 in a disabled state. The @samp{regexp} argument is a regular
27138 expression used to match the name of the loaded library.
27141 @subsubheading @value{GDBN} Command
27143 The corresponding @value{GDBN} command is @samp{catch load}.
27145 @subsubheading Example
27148 -catch-load -t foo.so
27149 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27150 what="load of library matching foo.so",catch-type="load",times="0"@}
27155 @subheading The @code{-catch-unload} Command
27156 @findex -catch-unload
27158 @subsubheading Synopsis
27161 -catch-unload [ -t ] [ -d ] @var{regexp}
27164 Add a catchpoint for library unload events. If the @samp{-t} option is
27165 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27166 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27167 created in a disabled state. The @samp{regexp} argument is a regular
27168 expression used to match the name of the unloaded library.
27170 @subsubheading @value{GDBN} Command
27172 The corresponding @value{GDBN} command is @samp{catch unload}.
27174 @subsubheading Example
27177 -catch-unload -d bar.so
27178 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27179 what="load of library matching bar.so",catch-type="unload",times="0"@}
27183 @node Ada Exception GDB/MI Catchpoint Commands
27184 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27186 The following @sc{gdb/mi} commands can be used to create catchpoints
27187 that stop the execution when Ada exceptions are being raised.
27189 @subheading The @code{-catch-assert} Command
27190 @findex -catch-assert
27192 @subsubheading Synopsis
27195 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27198 Add a catchpoint for failed Ada assertions.
27200 The possible optional parameters for this command are:
27203 @item -c @var{condition}
27204 Make the catchpoint conditional on @var{condition}.
27206 Create a disabled catchpoint.
27208 Create a temporary catchpoint.
27211 @subsubheading @value{GDBN} Command
27213 The corresponding @value{GDBN} command is @samp{catch assert}.
27215 @subsubheading Example
27219 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27220 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27221 thread-groups=["i1"],times="0",
27222 original-location="__gnat_debug_raise_assert_failure"@}
27226 @subheading The @code{-catch-exception} Command
27227 @findex -catch-exception
27229 @subsubheading Synopsis
27232 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27236 Add a catchpoint stopping when Ada exceptions are raised.
27237 By default, the command stops the program when any Ada exception
27238 gets raised. But it is also possible, by using some of the
27239 optional parameters described below, to create more selective
27242 The possible optional parameters for this command are:
27245 @item -c @var{condition}
27246 Make the catchpoint conditional on @var{condition}.
27248 Create a disabled catchpoint.
27249 @item -e @var{exception-name}
27250 Only stop when @var{exception-name} is raised. This option cannot
27251 be used combined with @samp{-u}.
27253 Create a temporary catchpoint.
27255 Stop only when an unhandled exception gets raised. This option
27256 cannot be used combined with @samp{-e}.
27259 @subsubheading @value{GDBN} Command
27261 The corresponding @value{GDBN} commands are @samp{catch exception}
27262 and @samp{catch exception unhandled}.
27264 @subsubheading Example
27267 -catch-exception -e Program_Error
27268 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27269 enabled="y",addr="0x0000000000404874",
27270 what="`Program_Error' Ada exception", thread-groups=["i1"],
27271 times="0",original-location="__gnat_debug_raise_exception"@}
27275 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27276 @node GDB/MI Program Context
27277 @section @sc{gdb/mi} Program Context
27279 @subheading The @code{-exec-arguments} Command
27280 @findex -exec-arguments
27283 @subsubheading Synopsis
27286 -exec-arguments @var{args}
27289 Set the inferior program arguments, to be used in the next
27292 @subsubheading @value{GDBN} Command
27294 The corresponding @value{GDBN} command is @samp{set args}.
27296 @subsubheading Example
27300 -exec-arguments -v word
27307 @subheading The @code{-exec-show-arguments} Command
27308 @findex -exec-show-arguments
27310 @subsubheading Synopsis
27313 -exec-show-arguments
27316 Print the arguments of the program.
27318 @subsubheading @value{GDBN} Command
27320 The corresponding @value{GDBN} command is @samp{show args}.
27322 @subsubheading Example
27327 @subheading The @code{-environment-cd} Command
27328 @findex -environment-cd
27330 @subsubheading Synopsis
27333 -environment-cd @var{pathdir}
27336 Set @value{GDBN}'s working directory.
27338 @subsubheading @value{GDBN} Command
27340 The corresponding @value{GDBN} command is @samp{cd}.
27342 @subsubheading Example
27346 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27352 @subheading The @code{-environment-directory} Command
27353 @findex -environment-directory
27355 @subsubheading Synopsis
27358 -environment-directory [ -r ] [ @var{pathdir} ]+
27361 Add directories @var{pathdir} to beginning of search path for source files.
27362 If the @samp{-r} option is used, the search path is reset to the default
27363 search path. If directories @var{pathdir} are supplied in addition to the
27364 @samp{-r} option, the search path is first reset and then addition
27366 Multiple directories may be specified, separated by blanks. Specifying
27367 multiple directories in a single command
27368 results in the directories added to the beginning of the
27369 search path in the same order they were presented in the command.
27370 If blanks are needed as
27371 part of a directory name, double-quotes should be used around
27372 the name. In the command output, the path will show up separated
27373 by the system directory-separator character. The directory-separator
27374 character must not be used
27375 in any directory name.
27376 If no directories are specified, the current search path is displayed.
27378 @subsubheading @value{GDBN} Command
27380 The corresponding @value{GDBN} command is @samp{dir}.
27382 @subsubheading Example
27386 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27387 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27389 -environment-directory ""
27390 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27392 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27393 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27395 -environment-directory -r
27396 ^done,source-path="$cdir:$cwd"
27401 @subheading The @code{-environment-path} Command
27402 @findex -environment-path
27404 @subsubheading Synopsis
27407 -environment-path [ -r ] [ @var{pathdir} ]+
27410 Add directories @var{pathdir} to beginning of search path for object files.
27411 If the @samp{-r} option is used, the search path is reset to the original
27412 search path that existed at gdb start-up. If directories @var{pathdir} are
27413 supplied in addition to the
27414 @samp{-r} option, the search path is first reset and then addition
27416 Multiple directories may be specified, separated by blanks. Specifying
27417 multiple directories in a single command
27418 results in the directories added to the beginning of the
27419 search path in the same order they were presented in the command.
27420 If blanks are needed as
27421 part of a directory name, double-quotes should be used around
27422 the name. In the command output, the path will show up separated
27423 by the system directory-separator character. The directory-separator
27424 character must not be used
27425 in any directory name.
27426 If no directories are specified, the current path is displayed.
27429 @subsubheading @value{GDBN} Command
27431 The corresponding @value{GDBN} command is @samp{path}.
27433 @subsubheading Example
27438 ^done,path="/usr/bin"
27440 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27441 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27443 -environment-path -r /usr/local/bin
27444 ^done,path="/usr/local/bin:/usr/bin"
27449 @subheading The @code{-environment-pwd} Command
27450 @findex -environment-pwd
27452 @subsubheading Synopsis
27458 Show the current working directory.
27460 @subsubheading @value{GDBN} Command
27462 The corresponding @value{GDBN} command is @samp{pwd}.
27464 @subsubheading Example
27469 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27473 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27474 @node GDB/MI Thread Commands
27475 @section @sc{gdb/mi} Thread Commands
27478 @subheading The @code{-thread-info} Command
27479 @findex -thread-info
27481 @subsubheading Synopsis
27484 -thread-info [ @var{thread-id} ]
27487 Reports information about either a specific thread, if
27488 the @var{thread-id} parameter is present, or about all
27489 threads. When printing information about all threads,
27490 also reports the current thread.
27492 @subsubheading @value{GDBN} Command
27494 The @samp{info thread} command prints the same information
27497 @subsubheading Result
27499 The result is a list of threads. The following attributes are
27500 defined for a given thread:
27504 This field exists only for the current thread. It has the value @samp{*}.
27507 The identifier that @value{GDBN} uses to refer to the thread.
27510 The identifier that the target uses to refer to the thread.
27513 Extra information about the thread, in a target-specific format. This
27517 The name of the thread. If the user specified a name using the
27518 @code{thread name} command, then this name is given. Otherwise, if
27519 @value{GDBN} can extract the thread name from the target, then that
27520 name is given. If @value{GDBN} cannot find the thread name, then this
27524 The stack frame currently executing in the thread.
27527 The thread's state. The @samp{state} field may have the following
27532 The thread is stopped. Frame information is available for stopped
27536 The thread is running. There's no frame information for running
27542 If @value{GDBN} can find the CPU core on which this thread is running,
27543 then this field is the core identifier. This field is optional.
27547 @subsubheading Example
27552 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27553 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27554 args=[]@},state="running"@},
27555 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27556 frame=@{level="0",addr="0x0804891f",func="foo",
27557 args=[@{name="i",value="10"@}],
27558 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27559 state="running"@}],
27560 current-thread-id="1"
27564 @subheading The @code{-thread-list-ids} Command
27565 @findex -thread-list-ids
27567 @subsubheading Synopsis
27573 Produces a list of the currently known @value{GDBN} thread ids. At the
27574 end of the list it also prints the total number of such threads.
27576 This command is retained for historical reasons, the
27577 @code{-thread-info} command should be used instead.
27579 @subsubheading @value{GDBN} Command
27581 Part of @samp{info threads} supplies the same information.
27583 @subsubheading Example
27588 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27589 current-thread-id="1",number-of-threads="3"
27594 @subheading The @code{-thread-select} Command
27595 @findex -thread-select
27597 @subsubheading Synopsis
27600 -thread-select @var{threadnum}
27603 Make @var{threadnum} the current thread. It prints the number of the new
27604 current thread, and the topmost frame for that thread.
27606 This command is deprecated in favor of explicitly using the
27607 @samp{--thread} option to each command.
27609 @subsubheading @value{GDBN} Command
27611 The corresponding @value{GDBN} command is @samp{thread}.
27613 @subsubheading Example
27620 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27621 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27625 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27626 number-of-threads="3"
27629 ^done,new-thread-id="3",
27630 frame=@{level="0",func="vprintf",
27631 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27632 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27636 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27637 @node GDB/MI Ada Tasking Commands
27638 @section @sc{gdb/mi} Ada Tasking Commands
27640 @subheading The @code{-ada-task-info} Command
27641 @findex -ada-task-info
27643 @subsubheading Synopsis
27646 -ada-task-info [ @var{task-id} ]
27649 Reports information about either a specific Ada task, if the
27650 @var{task-id} parameter is present, or about all Ada tasks.
27652 @subsubheading @value{GDBN} Command
27654 The @samp{info tasks} command prints the same information
27655 about all Ada tasks (@pxref{Ada Tasks}).
27657 @subsubheading Result
27659 The result is a table of Ada tasks. The following columns are
27660 defined for each Ada task:
27664 This field exists only for the current thread. It has the value @samp{*}.
27667 The identifier that @value{GDBN} uses to refer to the Ada task.
27670 The identifier that the target uses to refer to the Ada task.
27673 The identifier of the thread corresponding to the Ada task.
27675 This field should always exist, as Ada tasks are always implemented
27676 on top of a thread. But if @value{GDBN} cannot find this corresponding
27677 thread for any reason, the field is omitted.
27680 This field exists only when the task was created by another task.
27681 In this case, it provides the ID of the parent task.
27684 The base priority of the task.
27687 The current state of the task. For a detailed description of the
27688 possible states, see @ref{Ada Tasks}.
27691 The name of the task.
27695 @subsubheading Example
27699 ^done,tasks=@{nr_rows="3",nr_cols="8",
27700 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27701 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27702 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27703 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27704 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27705 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27706 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27707 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27708 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27709 state="Child Termination Wait",name="main_task"@}]@}
27713 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27714 @node GDB/MI Program Execution
27715 @section @sc{gdb/mi} Program Execution
27717 These are the asynchronous commands which generate the out-of-band
27718 record @samp{*stopped}. Currently @value{GDBN} only really executes
27719 asynchronously with remote targets and this interaction is mimicked in
27722 @subheading The @code{-exec-continue} Command
27723 @findex -exec-continue
27725 @subsubheading Synopsis
27728 -exec-continue [--reverse] [--all|--thread-group N]
27731 Resumes the execution of the inferior program, which will continue
27732 to execute until it reaches a debugger stop event. If the
27733 @samp{--reverse} option is specified, execution resumes in reverse until
27734 it reaches a stop event. Stop events may include
27737 breakpoints or watchpoints
27739 signals or exceptions
27741 the end of the process (or its beginning under @samp{--reverse})
27743 the end or beginning of a replay log if one is being used.
27745 In all-stop mode (@pxref{All-Stop
27746 Mode}), may resume only one thread, or all threads, depending on the
27747 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27748 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27749 ignored in all-stop mode. If the @samp{--thread-group} options is
27750 specified, then all threads in that thread group are resumed.
27752 @subsubheading @value{GDBN} Command
27754 The corresponding @value{GDBN} corresponding is @samp{continue}.
27756 @subsubheading Example
27763 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27764 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27770 @subheading The @code{-exec-finish} Command
27771 @findex -exec-finish
27773 @subsubheading Synopsis
27776 -exec-finish [--reverse]
27779 Resumes the execution of the inferior program until the current
27780 function is exited. Displays the results returned by the function.
27781 If the @samp{--reverse} option is specified, resumes the reverse
27782 execution of the inferior program until the point where current
27783 function was called.
27785 @subsubheading @value{GDBN} Command
27787 The corresponding @value{GDBN} command is @samp{finish}.
27789 @subsubheading Example
27791 Function returning @code{void}.
27798 *stopped,reason="function-finished",frame=@{func="main",args=[],
27799 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27803 Function returning other than @code{void}. The name of the internal
27804 @value{GDBN} variable storing the result is printed, together with the
27811 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27812 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27813 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27814 gdb-result-var="$1",return-value="0"
27819 @subheading The @code{-exec-interrupt} Command
27820 @findex -exec-interrupt
27822 @subsubheading Synopsis
27825 -exec-interrupt [--all|--thread-group N]
27828 Interrupts the background execution of the target. Note how the token
27829 associated with the stop message is the one for the execution command
27830 that has been interrupted. The token for the interrupt itself only
27831 appears in the @samp{^done} output. If the user is trying to
27832 interrupt a non-running program, an error message will be printed.
27834 Note that when asynchronous execution is enabled, this command is
27835 asynchronous just like other execution commands. That is, first the
27836 @samp{^done} response will be printed, and the target stop will be
27837 reported after that using the @samp{*stopped} notification.
27839 In non-stop mode, only the context thread is interrupted by default.
27840 All threads (in all inferiors) will be interrupted if the
27841 @samp{--all} option is specified. If the @samp{--thread-group}
27842 option is specified, all threads in that group will be interrupted.
27844 @subsubheading @value{GDBN} Command
27846 The corresponding @value{GDBN} command is @samp{interrupt}.
27848 @subsubheading Example
27859 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27860 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27861 fullname="/home/foo/bar/try.c",line="13"@}
27866 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27870 @subheading The @code{-exec-jump} Command
27873 @subsubheading Synopsis
27876 -exec-jump @var{location}
27879 Resumes execution of the inferior program at the location specified by
27880 parameter. @xref{Specify Location}, for a description of the
27881 different forms of @var{location}.
27883 @subsubheading @value{GDBN} Command
27885 The corresponding @value{GDBN} command is @samp{jump}.
27887 @subsubheading Example
27890 -exec-jump foo.c:10
27891 *running,thread-id="all"
27896 @subheading The @code{-exec-next} Command
27899 @subsubheading Synopsis
27902 -exec-next [--reverse]
27905 Resumes execution of the inferior program, stopping when the beginning
27906 of the next source line is reached.
27908 If the @samp{--reverse} option is specified, resumes reverse execution
27909 of the inferior program, stopping at the beginning of the previous
27910 source line. If you issue this command on the first line of a
27911 function, it will take you back to the caller of that function, to the
27912 source line where the function was called.
27915 @subsubheading @value{GDBN} Command
27917 The corresponding @value{GDBN} command is @samp{next}.
27919 @subsubheading Example
27925 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27930 @subheading The @code{-exec-next-instruction} Command
27931 @findex -exec-next-instruction
27933 @subsubheading Synopsis
27936 -exec-next-instruction [--reverse]
27939 Executes one machine instruction. If the instruction is a function
27940 call, continues until the function returns. If the program stops at an
27941 instruction in the middle of a source line, the address will be
27944 If the @samp{--reverse} option is specified, resumes reverse execution
27945 of the inferior program, stopping at the previous instruction. If the
27946 previously executed instruction was a return from another function,
27947 it will continue to execute in reverse until the call to that function
27948 (from the current stack frame) is reached.
27950 @subsubheading @value{GDBN} Command
27952 The corresponding @value{GDBN} command is @samp{nexti}.
27954 @subsubheading Example
27958 -exec-next-instruction
27962 *stopped,reason="end-stepping-range",
27963 addr="0x000100d4",line="5",file="hello.c"
27968 @subheading The @code{-exec-return} Command
27969 @findex -exec-return
27971 @subsubheading Synopsis
27977 Makes current function return immediately. Doesn't execute the inferior.
27978 Displays the new current frame.
27980 @subsubheading @value{GDBN} Command
27982 The corresponding @value{GDBN} command is @samp{return}.
27984 @subsubheading Example
27988 200-break-insert callee4
27989 200^done,bkpt=@{number="1",addr="0x00010734",
27990 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27995 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27996 frame=@{func="callee4",args=[],
27997 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27998 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28004 111^done,frame=@{level="0",func="callee3",
28005 args=[@{name="strarg",
28006 value="0x11940 \"A string argument.\""@}],
28007 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28008 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28013 @subheading The @code{-exec-run} Command
28016 @subsubheading Synopsis
28019 -exec-run [ --all | --thread-group N ] [ --start ]
28022 Starts execution of the inferior from the beginning. The inferior
28023 executes until either a breakpoint is encountered or the program
28024 exits. In the latter case the output will include an exit code, if
28025 the program has exited exceptionally.
28027 When neither the @samp{--all} nor the @samp{--thread-group} option
28028 is specified, the current inferior is started. If the
28029 @samp{--thread-group} option is specified, it should refer to a thread
28030 group of type @samp{process}, and that thread group will be started.
28031 If the @samp{--all} option is specified, then all inferiors will be started.
28033 Using the @samp{--start} option instructs the debugger to stop
28034 the execution at the start of the inferior's main subprogram,
28035 following the same behavior as the @code{start} command
28036 (@pxref{Starting}).
28038 @subsubheading @value{GDBN} Command
28040 The corresponding @value{GDBN} command is @samp{run}.
28042 @subsubheading Examples
28047 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28052 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28053 frame=@{func="main",args=[],file="recursive2.c",
28054 fullname="/home/foo/bar/recursive2.c",line="4"@}
28059 Program exited normally:
28067 *stopped,reason="exited-normally"
28072 Program exited exceptionally:
28080 *stopped,reason="exited",exit-code="01"
28084 Another way the program can terminate is if it receives a signal such as
28085 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28089 *stopped,reason="exited-signalled",signal-name="SIGINT",
28090 signal-meaning="Interrupt"
28094 @c @subheading -exec-signal
28097 @subheading The @code{-exec-step} Command
28100 @subsubheading Synopsis
28103 -exec-step [--reverse]
28106 Resumes execution of the inferior program, stopping when the beginning
28107 of the next source line is reached, if the next source line is not a
28108 function call. If it is, stop at the first instruction of the called
28109 function. If the @samp{--reverse} option is specified, resumes reverse
28110 execution of the inferior program, stopping at the beginning of the
28111 previously executed source line.
28113 @subsubheading @value{GDBN} Command
28115 The corresponding @value{GDBN} command is @samp{step}.
28117 @subsubheading Example
28119 Stepping into a function:
28125 *stopped,reason="end-stepping-range",
28126 frame=@{func="foo",args=[@{name="a",value="10"@},
28127 @{name="b",value="0"@}],file="recursive2.c",
28128 fullname="/home/foo/bar/recursive2.c",line="11"@}
28138 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28143 @subheading The @code{-exec-step-instruction} Command
28144 @findex -exec-step-instruction
28146 @subsubheading Synopsis
28149 -exec-step-instruction [--reverse]
28152 Resumes the inferior which executes one machine instruction. If the
28153 @samp{--reverse} option is specified, resumes reverse execution of the
28154 inferior program, stopping at the previously executed instruction.
28155 The output, once @value{GDBN} has stopped, will vary depending on
28156 whether we have stopped in the middle of a source line or not. In the
28157 former case, the address at which the program stopped will be printed
28160 @subsubheading @value{GDBN} Command
28162 The corresponding @value{GDBN} command is @samp{stepi}.
28164 @subsubheading Example
28168 -exec-step-instruction
28172 *stopped,reason="end-stepping-range",
28173 frame=@{func="foo",args=[],file="try.c",
28174 fullname="/home/foo/bar/try.c",line="10"@}
28176 -exec-step-instruction
28180 *stopped,reason="end-stepping-range",
28181 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28182 fullname="/home/foo/bar/try.c",line="10"@}
28187 @subheading The @code{-exec-until} Command
28188 @findex -exec-until
28190 @subsubheading Synopsis
28193 -exec-until [ @var{location} ]
28196 Executes the inferior until the @var{location} specified in the
28197 argument is reached. If there is no argument, the inferior executes
28198 until a source line greater than the current one is reached. The
28199 reason for stopping in this case will be @samp{location-reached}.
28201 @subsubheading @value{GDBN} Command
28203 The corresponding @value{GDBN} command is @samp{until}.
28205 @subsubheading Example
28209 -exec-until recursive2.c:6
28213 *stopped,reason="location-reached",frame=@{func="main",args=[],
28214 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28219 @subheading -file-clear
28220 Is this going away????
28223 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28224 @node GDB/MI Stack Manipulation
28225 @section @sc{gdb/mi} Stack Manipulation Commands
28227 @subheading The @code{-enable-frame-filters} Command
28228 @findex -enable-frame-filters
28231 -enable-frame-filters
28234 @value{GDBN} allows Python-based frame filters to affect the output of
28235 the MI commands relating to stack traces. As there is no way to
28236 implement this in a fully backward-compatible way, a front end must
28237 request that this functionality be enabled.
28239 Once enabled, this feature cannot be disabled.
28241 Note that if Python support has not been compiled into @value{GDBN},
28242 this command will still succeed (and do nothing).
28244 @subheading The @code{-stack-info-frame} Command
28245 @findex -stack-info-frame
28247 @subsubheading Synopsis
28253 Get info on the selected frame.
28255 @subsubheading @value{GDBN} Command
28257 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28258 (without arguments).
28260 @subsubheading Example
28265 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28266 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28267 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28271 @subheading The @code{-stack-info-depth} Command
28272 @findex -stack-info-depth
28274 @subsubheading Synopsis
28277 -stack-info-depth [ @var{max-depth} ]
28280 Return the depth of the stack. If the integer argument @var{max-depth}
28281 is specified, do not count beyond @var{max-depth} frames.
28283 @subsubheading @value{GDBN} Command
28285 There's no equivalent @value{GDBN} command.
28287 @subsubheading Example
28289 For a stack with frame levels 0 through 11:
28296 -stack-info-depth 4
28299 -stack-info-depth 12
28302 -stack-info-depth 11
28305 -stack-info-depth 13
28310 @anchor{-stack-list-arguments}
28311 @subheading The @code{-stack-list-arguments} Command
28312 @findex -stack-list-arguments
28314 @subsubheading Synopsis
28317 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28318 [ @var{low-frame} @var{high-frame} ]
28321 Display a list of the arguments for the frames between @var{low-frame}
28322 and @var{high-frame} (inclusive). If @var{low-frame} and
28323 @var{high-frame} are not provided, list the arguments for the whole
28324 call stack. If the two arguments are equal, show the single frame
28325 at the corresponding level. It is an error if @var{low-frame} is
28326 larger than the actual number of frames. On the other hand,
28327 @var{high-frame} may be larger than the actual number of frames, in
28328 which case only existing frames will be returned.
28330 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28331 the variables; if it is 1 or @code{--all-values}, print also their
28332 values; and if it is 2 or @code{--simple-values}, print the name,
28333 type and value for simple data types, and the name and type for arrays,
28334 structures and unions. If the option @code{--no-frame-filters} is
28335 supplied, then Python frame filters will not be executed.
28337 If the @code{--skip-unavailable} option is specified, arguments that
28338 are not available are not listed. Partially available arguments
28339 are still displayed, however.
28341 Use of this command to obtain arguments in a single frame is
28342 deprecated in favor of the @samp{-stack-list-variables} command.
28344 @subsubheading @value{GDBN} Command
28346 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28347 @samp{gdb_get_args} command which partially overlaps with the
28348 functionality of @samp{-stack-list-arguments}.
28350 @subsubheading Example
28357 frame=@{level="0",addr="0x00010734",func="callee4",
28358 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28359 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28360 frame=@{level="1",addr="0x0001076c",func="callee3",
28361 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28362 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28363 frame=@{level="2",addr="0x0001078c",func="callee2",
28364 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28365 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28366 frame=@{level="3",addr="0x000107b4",func="callee1",
28367 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28368 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28369 frame=@{level="4",addr="0x000107e0",func="main",
28370 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28371 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28373 -stack-list-arguments 0
28376 frame=@{level="0",args=[]@},
28377 frame=@{level="1",args=[name="strarg"]@},
28378 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28379 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28380 frame=@{level="4",args=[]@}]
28382 -stack-list-arguments 1
28385 frame=@{level="0",args=[]@},
28387 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28388 frame=@{level="2",args=[
28389 @{name="intarg",value="2"@},
28390 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28391 @{frame=@{level="3",args=[
28392 @{name="intarg",value="2"@},
28393 @{name="strarg",value="0x11940 \"A string argument.\""@},
28394 @{name="fltarg",value="3.5"@}]@},
28395 frame=@{level="4",args=[]@}]
28397 -stack-list-arguments 0 2 2
28398 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28400 -stack-list-arguments 1 2 2
28401 ^done,stack-args=[frame=@{level="2",
28402 args=[@{name="intarg",value="2"@},
28403 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28407 @c @subheading -stack-list-exception-handlers
28410 @anchor{-stack-list-frames}
28411 @subheading The @code{-stack-list-frames} Command
28412 @findex -stack-list-frames
28414 @subsubheading Synopsis
28417 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28420 List the frames currently on the stack. For each frame it displays the
28425 The frame number, 0 being the topmost frame, i.e., the innermost function.
28427 The @code{$pc} value for that frame.
28431 File name of the source file where the function lives.
28432 @item @var{fullname}
28433 The full file name of the source file where the function lives.
28435 Line number corresponding to the @code{$pc}.
28437 The shared library where this function is defined. This is only given
28438 if the frame's function is not known.
28441 If invoked without arguments, this command prints a backtrace for the
28442 whole stack. If given two integer arguments, it shows the frames whose
28443 levels are between the two arguments (inclusive). If the two arguments
28444 are equal, it shows the single frame at the corresponding level. It is
28445 an error if @var{low-frame} is larger than the actual number of
28446 frames. On the other hand, @var{high-frame} may be larger than the
28447 actual number of frames, in which case only existing frames will be
28448 returned. If the option @code{--no-frame-filters} is supplied, then
28449 Python frame filters will not be executed.
28451 @subsubheading @value{GDBN} Command
28453 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28455 @subsubheading Example
28457 Full stack backtrace:
28463 [frame=@{level="0",addr="0x0001076c",func="foo",
28464 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28465 frame=@{level="1",addr="0x000107a4",func="foo",
28466 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28467 frame=@{level="2",addr="0x000107a4",func="foo",
28468 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28469 frame=@{level="3",addr="0x000107a4",func="foo",
28470 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28471 frame=@{level="4",addr="0x000107a4",func="foo",
28472 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28473 frame=@{level="5",addr="0x000107a4",func="foo",
28474 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28475 frame=@{level="6",addr="0x000107a4",func="foo",
28476 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28477 frame=@{level="7",addr="0x000107a4",func="foo",
28478 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28479 frame=@{level="8",addr="0x000107a4",func="foo",
28480 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28481 frame=@{level="9",addr="0x000107a4",func="foo",
28482 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28483 frame=@{level="10",addr="0x000107a4",func="foo",
28484 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28485 frame=@{level="11",addr="0x00010738",func="main",
28486 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28490 Show frames between @var{low_frame} and @var{high_frame}:
28494 -stack-list-frames 3 5
28496 [frame=@{level="3",addr="0x000107a4",func="foo",
28497 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28498 frame=@{level="4",addr="0x000107a4",func="foo",
28499 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28500 frame=@{level="5",addr="0x000107a4",func="foo",
28501 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28505 Show a single frame:
28509 -stack-list-frames 3 3
28511 [frame=@{level="3",addr="0x000107a4",func="foo",
28512 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28517 @subheading The @code{-stack-list-locals} Command
28518 @findex -stack-list-locals
28519 @anchor{-stack-list-locals}
28521 @subsubheading Synopsis
28524 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28527 Display the local variable names for the selected frame. If
28528 @var{print-values} is 0 or @code{--no-values}, print only the names of
28529 the variables; if it is 1 or @code{--all-values}, print also their
28530 values; and if it is 2 or @code{--simple-values}, print the name,
28531 type and value for simple data types, and the name and type for arrays,
28532 structures and unions. In this last case, a frontend can immediately
28533 display the value of simple data types and create variable objects for
28534 other data types when the user wishes to explore their values in
28535 more detail. If the option @code{--no-frame-filters} is supplied, then
28536 Python frame filters will not be executed.
28538 If the @code{--skip-unavailable} option is specified, local variables
28539 that are not available are not listed. Partially available local
28540 variables are still displayed, however.
28542 This command is deprecated in favor of the
28543 @samp{-stack-list-variables} command.
28545 @subsubheading @value{GDBN} Command
28547 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28549 @subsubheading Example
28553 -stack-list-locals 0
28554 ^done,locals=[name="A",name="B",name="C"]
28556 -stack-list-locals --all-values
28557 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28558 @{name="C",value="@{1, 2, 3@}"@}]
28559 -stack-list-locals --simple-values
28560 ^done,locals=[@{name="A",type="int",value="1"@},
28561 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28565 @anchor{-stack-list-variables}
28566 @subheading The @code{-stack-list-variables} Command
28567 @findex -stack-list-variables
28569 @subsubheading Synopsis
28572 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28575 Display the names of local variables and function arguments for the selected frame. If
28576 @var{print-values} is 0 or @code{--no-values}, print only the names of
28577 the variables; if it is 1 or @code{--all-values}, print also their
28578 values; and if it is 2 or @code{--simple-values}, print the name,
28579 type and value for simple data types, and the name and type for arrays,
28580 structures and unions. If the option @code{--no-frame-filters} is
28581 supplied, then Python frame filters will not be executed.
28583 If the @code{--skip-unavailable} option is specified, local variables
28584 and arguments that are not available are not listed. Partially
28585 available arguments and local variables are still displayed, however.
28587 @subsubheading Example
28591 -stack-list-variables --thread 1 --frame 0 --all-values
28592 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28597 @subheading The @code{-stack-select-frame} Command
28598 @findex -stack-select-frame
28600 @subsubheading Synopsis
28603 -stack-select-frame @var{framenum}
28606 Change the selected frame. Select a different frame @var{framenum} on
28609 This command in deprecated in favor of passing the @samp{--frame}
28610 option to every command.
28612 @subsubheading @value{GDBN} Command
28614 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28615 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28617 @subsubheading Example
28621 -stack-select-frame 2
28626 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28627 @node GDB/MI Variable Objects
28628 @section @sc{gdb/mi} Variable Objects
28632 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28634 For the implementation of a variable debugger window (locals, watched
28635 expressions, etc.), we are proposing the adaptation of the existing code
28636 used by @code{Insight}.
28638 The two main reasons for that are:
28642 It has been proven in practice (it is already on its second generation).
28645 It will shorten development time (needless to say how important it is
28649 The original interface was designed to be used by Tcl code, so it was
28650 slightly changed so it could be used through @sc{gdb/mi}. This section
28651 describes the @sc{gdb/mi} operations that will be available and gives some
28652 hints about their use.
28654 @emph{Note}: In addition to the set of operations described here, we
28655 expect the @sc{gui} implementation of a variable window to require, at
28656 least, the following operations:
28659 @item @code{-gdb-show} @code{output-radix}
28660 @item @code{-stack-list-arguments}
28661 @item @code{-stack-list-locals}
28662 @item @code{-stack-select-frame}
28667 @subheading Introduction to Variable Objects
28669 @cindex variable objects in @sc{gdb/mi}
28671 Variable objects are "object-oriented" MI interface for examining and
28672 changing values of expressions. Unlike some other MI interfaces that
28673 work with expressions, variable objects are specifically designed for
28674 simple and efficient presentation in the frontend. A variable object
28675 is identified by string name. When a variable object is created, the
28676 frontend specifies the expression for that variable object. The
28677 expression can be a simple variable, or it can be an arbitrary complex
28678 expression, and can even involve CPU registers. After creating a
28679 variable object, the frontend can invoke other variable object
28680 operations---for example to obtain or change the value of a variable
28681 object, or to change display format.
28683 Variable objects have hierarchical tree structure. Any variable object
28684 that corresponds to a composite type, such as structure in C, has
28685 a number of child variable objects, for example corresponding to each
28686 element of a structure. A child variable object can itself have
28687 children, recursively. Recursion ends when we reach
28688 leaf variable objects, which always have built-in types. Child variable
28689 objects are created only by explicit request, so if a frontend
28690 is not interested in the children of a particular variable object, no
28691 child will be created.
28693 For a leaf variable object it is possible to obtain its value as a
28694 string, or set the value from a string. String value can be also
28695 obtained for a non-leaf variable object, but it's generally a string
28696 that only indicates the type of the object, and does not list its
28697 contents. Assignment to a non-leaf variable object is not allowed.
28699 A frontend does not need to read the values of all variable objects each time
28700 the program stops. Instead, MI provides an update command that lists all
28701 variable objects whose values has changed since the last update
28702 operation. This considerably reduces the amount of data that must
28703 be transferred to the frontend. As noted above, children variable
28704 objects are created on demand, and only leaf variable objects have a
28705 real value. As result, gdb will read target memory only for leaf
28706 variables that frontend has created.
28708 The automatic update is not always desirable. For example, a frontend
28709 might want to keep a value of some expression for future reference,
28710 and never update it. For another example, fetching memory is
28711 relatively slow for embedded targets, so a frontend might want
28712 to disable automatic update for the variables that are either not
28713 visible on the screen, or ``closed''. This is possible using so
28714 called ``frozen variable objects''. Such variable objects are never
28715 implicitly updated.
28717 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28718 fixed variable object, the expression is parsed when the variable
28719 object is created, including associating identifiers to specific
28720 variables. The meaning of expression never changes. For a floating
28721 variable object the values of variables whose names appear in the
28722 expressions are re-evaluated every time in the context of the current
28723 frame. Consider this example:
28728 struct work_state state;
28735 If a fixed variable object for the @code{state} variable is created in
28736 this function, and we enter the recursive call, the variable
28737 object will report the value of @code{state} in the top-level
28738 @code{do_work} invocation. On the other hand, a floating variable
28739 object will report the value of @code{state} in the current frame.
28741 If an expression specified when creating a fixed variable object
28742 refers to a local variable, the variable object becomes bound to the
28743 thread and frame in which the variable object is created. When such
28744 variable object is updated, @value{GDBN} makes sure that the
28745 thread/frame combination the variable object is bound to still exists,
28746 and re-evaluates the variable object in context of that thread/frame.
28748 The following is the complete set of @sc{gdb/mi} operations defined to
28749 access this functionality:
28751 @multitable @columnfractions .4 .6
28752 @item @strong{Operation}
28753 @tab @strong{Description}
28755 @item @code{-enable-pretty-printing}
28756 @tab enable Python-based pretty-printing
28757 @item @code{-var-create}
28758 @tab create a variable object
28759 @item @code{-var-delete}
28760 @tab delete the variable object and/or its children
28761 @item @code{-var-set-format}
28762 @tab set the display format of this variable
28763 @item @code{-var-show-format}
28764 @tab show the display format of this variable
28765 @item @code{-var-info-num-children}
28766 @tab tells how many children this object has
28767 @item @code{-var-list-children}
28768 @tab return a list of the object's children
28769 @item @code{-var-info-type}
28770 @tab show the type of this variable object
28771 @item @code{-var-info-expression}
28772 @tab print parent-relative expression that this variable object represents
28773 @item @code{-var-info-path-expression}
28774 @tab print full expression that this variable object represents
28775 @item @code{-var-show-attributes}
28776 @tab is this variable editable? does it exist here?
28777 @item @code{-var-evaluate-expression}
28778 @tab get the value of this variable
28779 @item @code{-var-assign}
28780 @tab set the value of this variable
28781 @item @code{-var-update}
28782 @tab update the variable and its children
28783 @item @code{-var-set-frozen}
28784 @tab set frozeness attribute
28785 @item @code{-var-set-update-range}
28786 @tab set range of children to display on update
28789 In the next subsection we describe each operation in detail and suggest
28790 how it can be used.
28792 @subheading Description And Use of Operations on Variable Objects
28794 @subheading The @code{-enable-pretty-printing} Command
28795 @findex -enable-pretty-printing
28798 -enable-pretty-printing
28801 @value{GDBN} allows Python-based visualizers to affect the output of the
28802 MI variable object commands. However, because there was no way to
28803 implement this in a fully backward-compatible way, a front end must
28804 request that this functionality be enabled.
28806 Once enabled, this feature cannot be disabled.
28808 Note that if Python support has not been compiled into @value{GDBN},
28809 this command will still succeed (and do nothing).
28811 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28812 may work differently in future versions of @value{GDBN}.
28814 @subheading The @code{-var-create} Command
28815 @findex -var-create
28817 @subsubheading Synopsis
28820 -var-create @{@var{name} | "-"@}
28821 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28824 This operation creates a variable object, which allows the monitoring of
28825 a variable, the result of an expression, a memory cell or a CPU
28828 The @var{name} parameter is the string by which the object can be
28829 referenced. It must be unique. If @samp{-} is specified, the varobj
28830 system will generate a string ``varNNNNNN'' automatically. It will be
28831 unique provided that one does not specify @var{name} of that format.
28832 The command fails if a duplicate name is found.
28834 The frame under which the expression should be evaluated can be
28835 specified by @var{frame-addr}. A @samp{*} indicates that the current
28836 frame should be used. A @samp{@@} indicates that a floating variable
28837 object must be created.
28839 @var{expression} is any expression valid on the current language set (must not
28840 begin with a @samp{*}), or one of the following:
28844 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28847 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28850 @samp{$@var{regname}} --- a CPU register name
28853 @cindex dynamic varobj
28854 A varobj's contents may be provided by a Python-based pretty-printer. In this
28855 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28856 have slightly different semantics in some cases. If the
28857 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28858 will never create a dynamic varobj. This ensures backward
28859 compatibility for existing clients.
28861 @subsubheading Result
28863 This operation returns attributes of the newly-created varobj. These
28868 The name of the varobj.
28871 The number of children of the varobj. This number is not necessarily
28872 reliable for a dynamic varobj. Instead, you must examine the
28873 @samp{has_more} attribute.
28876 The varobj's scalar value. For a varobj whose type is some sort of
28877 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28878 will not be interesting.
28881 The varobj's type. This is a string representation of the type, as
28882 would be printed by the @value{GDBN} CLI. If @samp{print object}
28883 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28884 @emph{actual} (derived) type of the object is shown rather than the
28885 @emph{declared} one.
28888 If a variable object is bound to a specific thread, then this is the
28889 thread's identifier.
28892 For a dynamic varobj, this indicates whether there appear to be any
28893 children available. For a non-dynamic varobj, this will be 0.
28896 This attribute will be present and have the value @samp{1} if the
28897 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28898 then this attribute will not be present.
28901 A dynamic varobj can supply a display hint to the front end. The
28902 value comes directly from the Python pretty-printer object's
28903 @code{display_hint} method. @xref{Pretty Printing API}.
28906 Typical output will look like this:
28909 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28910 has_more="@var{has_more}"
28914 @subheading The @code{-var-delete} Command
28915 @findex -var-delete
28917 @subsubheading Synopsis
28920 -var-delete [ -c ] @var{name}
28923 Deletes a previously created variable object and all of its children.
28924 With the @samp{-c} option, just deletes the children.
28926 Returns an error if the object @var{name} is not found.
28929 @subheading The @code{-var-set-format} Command
28930 @findex -var-set-format
28932 @subsubheading Synopsis
28935 -var-set-format @var{name} @var{format-spec}
28938 Sets the output format for the value of the object @var{name} to be
28941 @anchor{-var-set-format}
28942 The syntax for the @var{format-spec} is as follows:
28945 @var{format-spec} @expansion{}
28946 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
28949 The natural format is the default format choosen automatically
28950 based on the variable type (like decimal for an @code{int}, hex
28951 for pointers, etc.).
28953 The zero-hexadecimal format has a representation similar to hexadecimal
28954 but with padding zeroes to the left of the value. For example, a 32-bit
28955 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
28956 zero-hexadecimal format.
28958 For a variable with children, the format is set only on the
28959 variable itself, and the children are not affected.
28961 @subheading The @code{-var-show-format} Command
28962 @findex -var-show-format
28964 @subsubheading Synopsis
28967 -var-show-format @var{name}
28970 Returns the format used to display the value of the object @var{name}.
28973 @var{format} @expansion{}
28978 @subheading The @code{-var-info-num-children} Command
28979 @findex -var-info-num-children
28981 @subsubheading Synopsis
28984 -var-info-num-children @var{name}
28987 Returns the number of children of a variable object @var{name}:
28993 Note that this number is not completely reliable for a dynamic varobj.
28994 It will return the current number of children, but more children may
28998 @subheading The @code{-var-list-children} Command
28999 @findex -var-list-children
29001 @subsubheading Synopsis
29004 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29006 @anchor{-var-list-children}
29008 Return a list of the children of the specified variable object and
29009 create variable objects for them, if they do not already exist. With
29010 a single argument or if @var{print-values} has a value of 0 or
29011 @code{--no-values}, print only the names of the variables; if
29012 @var{print-values} is 1 or @code{--all-values}, also print their
29013 values; and if it is 2 or @code{--simple-values} print the name and
29014 value for simple data types and just the name for arrays, structures
29017 @var{from} and @var{to}, if specified, indicate the range of children
29018 to report. If @var{from} or @var{to} is less than zero, the range is
29019 reset and all children will be reported. Otherwise, children starting
29020 at @var{from} (zero-based) and up to and excluding @var{to} will be
29023 If a child range is requested, it will only affect the current call to
29024 @code{-var-list-children}, but not future calls to @code{-var-update}.
29025 For this, you must instead use @code{-var-set-update-range}. The
29026 intent of this approach is to enable a front end to implement any
29027 update approach it likes; for example, scrolling a view may cause the
29028 front end to request more children with @code{-var-list-children}, and
29029 then the front end could call @code{-var-set-update-range} with a
29030 different range to ensure that future updates are restricted to just
29033 For each child the following results are returned:
29038 Name of the variable object created for this child.
29041 The expression to be shown to the user by the front end to designate this child.
29042 For example this may be the name of a structure member.
29044 For a dynamic varobj, this value cannot be used to form an
29045 expression. There is no way to do this at all with a dynamic varobj.
29047 For C/C@t{++} structures there are several pseudo children returned to
29048 designate access qualifiers. For these pseudo children @var{exp} is
29049 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29050 type and value are not present.
29052 A dynamic varobj will not report the access qualifying
29053 pseudo-children, regardless of the language. This information is not
29054 available at all with a dynamic varobj.
29057 Number of children this child has. For a dynamic varobj, this will be
29061 The type of the child. If @samp{print object}
29062 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29063 @emph{actual} (derived) type of the object is shown rather than the
29064 @emph{declared} one.
29067 If values were requested, this is the value.
29070 If this variable object is associated with a thread, this is the thread id.
29071 Otherwise this result is not present.
29074 If the variable object is frozen, this variable will be present with a value of 1.
29077 A dynamic varobj can supply a display hint to the front end. The
29078 value comes directly from the Python pretty-printer object's
29079 @code{display_hint} method. @xref{Pretty Printing API}.
29082 This attribute will be present and have the value @samp{1} if the
29083 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29084 then this attribute will not be present.
29088 The result may have its own attributes:
29092 A dynamic varobj can supply a display hint to the front end. The
29093 value comes directly from the Python pretty-printer object's
29094 @code{display_hint} method. @xref{Pretty Printing API}.
29097 This is an integer attribute which is nonzero if there are children
29098 remaining after the end of the selected range.
29101 @subsubheading Example
29105 -var-list-children n
29106 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29107 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29109 -var-list-children --all-values n
29110 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29111 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29115 @subheading The @code{-var-info-type} Command
29116 @findex -var-info-type
29118 @subsubheading Synopsis
29121 -var-info-type @var{name}
29124 Returns the type of the specified variable @var{name}. The type is
29125 returned as a string in the same format as it is output by the
29129 type=@var{typename}
29133 @subheading The @code{-var-info-expression} Command
29134 @findex -var-info-expression
29136 @subsubheading Synopsis
29139 -var-info-expression @var{name}
29142 Returns a string that is suitable for presenting this
29143 variable object in user interface. The string is generally
29144 not valid expression in the current language, and cannot be evaluated.
29146 For example, if @code{a} is an array, and variable object
29147 @code{A} was created for @code{a}, then we'll get this output:
29150 (gdb) -var-info-expression A.1
29151 ^done,lang="C",exp="1"
29155 Here, the value of @code{lang} is the language name, which can be
29156 found in @ref{Supported Languages}.
29158 Note that the output of the @code{-var-list-children} command also
29159 includes those expressions, so the @code{-var-info-expression} command
29162 @subheading The @code{-var-info-path-expression} Command
29163 @findex -var-info-path-expression
29165 @subsubheading Synopsis
29168 -var-info-path-expression @var{name}
29171 Returns an expression that can be evaluated in the current
29172 context and will yield the same value that a variable object has.
29173 Compare this with the @code{-var-info-expression} command, which
29174 result can be used only for UI presentation. Typical use of
29175 the @code{-var-info-path-expression} command is creating a
29176 watchpoint from a variable object.
29178 This command is currently not valid for children of a dynamic varobj,
29179 and will give an error when invoked on one.
29181 For example, suppose @code{C} is a C@t{++} class, derived from class
29182 @code{Base}, and that the @code{Base} class has a member called
29183 @code{m_size}. Assume a variable @code{c} is has the type of
29184 @code{C} and a variable object @code{C} was created for variable
29185 @code{c}. Then, we'll get this output:
29187 (gdb) -var-info-path-expression C.Base.public.m_size
29188 ^done,path_expr=((Base)c).m_size)
29191 @subheading The @code{-var-show-attributes} Command
29192 @findex -var-show-attributes
29194 @subsubheading Synopsis
29197 -var-show-attributes @var{name}
29200 List attributes of the specified variable object @var{name}:
29203 status=@var{attr} [ ( ,@var{attr} )* ]
29207 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29209 @subheading The @code{-var-evaluate-expression} Command
29210 @findex -var-evaluate-expression
29212 @subsubheading Synopsis
29215 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29218 Evaluates the expression that is represented by the specified variable
29219 object and returns its value as a string. The format of the string
29220 can be specified with the @samp{-f} option. The possible values of
29221 this option are the same as for @code{-var-set-format}
29222 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29223 the current display format will be used. The current display format
29224 can be changed using the @code{-var-set-format} command.
29230 Note that one must invoke @code{-var-list-children} for a variable
29231 before the value of a child variable can be evaluated.
29233 @subheading The @code{-var-assign} Command
29234 @findex -var-assign
29236 @subsubheading Synopsis
29239 -var-assign @var{name} @var{expression}
29242 Assigns the value of @var{expression} to the variable object specified
29243 by @var{name}. The object must be @samp{editable}. If the variable's
29244 value is altered by the assign, the variable will show up in any
29245 subsequent @code{-var-update} list.
29247 @subsubheading Example
29255 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29259 @subheading The @code{-var-update} Command
29260 @findex -var-update
29262 @subsubheading Synopsis
29265 -var-update [@var{print-values}] @{@var{name} | "*"@}
29268 Reevaluate the expressions corresponding to the variable object
29269 @var{name} and all its direct and indirect children, and return the
29270 list of variable objects whose values have changed; @var{name} must
29271 be a root variable object. Here, ``changed'' means that the result of
29272 @code{-var-evaluate-expression} before and after the
29273 @code{-var-update} is different. If @samp{*} is used as the variable
29274 object names, all existing variable objects are updated, except
29275 for frozen ones (@pxref{-var-set-frozen}). The option
29276 @var{print-values} determines whether both names and values, or just
29277 names are printed. The possible values of this option are the same
29278 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29279 recommended to use the @samp{--all-values} option, to reduce the
29280 number of MI commands needed on each program stop.
29282 With the @samp{*} parameter, if a variable object is bound to a
29283 currently running thread, it will not be updated, without any
29286 If @code{-var-set-update-range} was previously used on a varobj, then
29287 only the selected range of children will be reported.
29289 @code{-var-update} reports all the changed varobjs in a tuple named
29292 Each item in the change list is itself a tuple holding:
29296 The name of the varobj.
29299 If values were requested for this update, then this field will be
29300 present and will hold the value of the varobj.
29303 @anchor{-var-update}
29304 This field is a string which may take one of three values:
29308 The variable object's current value is valid.
29311 The variable object does not currently hold a valid value but it may
29312 hold one in the future if its associated expression comes back into
29316 The variable object no longer holds a valid value.
29317 This can occur when the executable file being debugged has changed,
29318 either through recompilation or by using the @value{GDBN} @code{file}
29319 command. The front end should normally choose to delete these variable
29323 In the future new values may be added to this list so the front should
29324 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29327 This is only present if the varobj is still valid. If the type
29328 changed, then this will be the string @samp{true}; otherwise it will
29331 When a varobj's type changes, its children are also likely to have
29332 become incorrect. Therefore, the varobj's children are automatically
29333 deleted when this attribute is @samp{true}. Also, the varobj's update
29334 range, when set using the @code{-var-set-update-range} command, is
29338 If the varobj's type changed, then this field will be present and will
29341 @item new_num_children
29342 For a dynamic varobj, if the number of children changed, or if the
29343 type changed, this will be the new number of children.
29345 The @samp{numchild} field in other varobj responses is generally not
29346 valid for a dynamic varobj -- it will show the number of children that
29347 @value{GDBN} knows about, but because dynamic varobjs lazily
29348 instantiate their children, this will not reflect the number of
29349 children which may be available.
29351 The @samp{new_num_children} attribute only reports changes to the
29352 number of children known by @value{GDBN}. This is the only way to
29353 detect whether an update has removed children (which necessarily can
29354 only happen at the end of the update range).
29357 The display hint, if any.
29360 This is an integer value, which will be 1 if there are more children
29361 available outside the varobj's update range.
29364 This attribute will be present and have the value @samp{1} if the
29365 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29366 then this attribute will not be present.
29369 If new children were added to a dynamic varobj within the selected
29370 update range (as set by @code{-var-set-update-range}), then they will
29371 be listed in this attribute.
29374 @subsubheading Example
29381 -var-update --all-values var1
29382 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29383 type_changed="false"@}]
29387 @subheading The @code{-var-set-frozen} Command
29388 @findex -var-set-frozen
29389 @anchor{-var-set-frozen}
29391 @subsubheading Synopsis
29394 -var-set-frozen @var{name} @var{flag}
29397 Set the frozenness flag on the variable object @var{name}. The
29398 @var{flag} parameter should be either @samp{1} to make the variable
29399 frozen or @samp{0} to make it unfrozen. If a variable object is
29400 frozen, then neither itself, nor any of its children, are
29401 implicitly updated by @code{-var-update} of
29402 a parent variable or by @code{-var-update *}. Only
29403 @code{-var-update} of the variable itself will update its value and
29404 values of its children. After a variable object is unfrozen, it is
29405 implicitly updated by all subsequent @code{-var-update} operations.
29406 Unfreezing a variable does not update it, only subsequent
29407 @code{-var-update} does.
29409 @subsubheading Example
29413 -var-set-frozen V 1
29418 @subheading The @code{-var-set-update-range} command
29419 @findex -var-set-update-range
29420 @anchor{-var-set-update-range}
29422 @subsubheading Synopsis
29425 -var-set-update-range @var{name} @var{from} @var{to}
29428 Set the range of children to be returned by future invocations of
29429 @code{-var-update}.
29431 @var{from} and @var{to} indicate the range of children to report. If
29432 @var{from} or @var{to} is less than zero, the range is reset and all
29433 children will be reported. Otherwise, children starting at @var{from}
29434 (zero-based) and up to and excluding @var{to} will be reported.
29436 @subsubheading Example
29440 -var-set-update-range V 1 2
29444 @subheading The @code{-var-set-visualizer} command
29445 @findex -var-set-visualizer
29446 @anchor{-var-set-visualizer}
29448 @subsubheading Synopsis
29451 -var-set-visualizer @var{name} @var{visualizer}
29454 Set a visualizer for the variable object @var{name}.
29456 @var{visualizer} is the visualizer to use. The special value
29457 @samp{None} means to disable any visualizer in use.
29459 If not @samp{None}, @var{visualizer} must be a Python expression.
29460 This expression must evaluate to a callable object which accepts a
29461 single argument. @value{GDBN} will call this object with the value of
29462 the varobj @var{name} as an argument (this is done so that the same
29463 Python pretty-printing code can be used for both the CLI and MI).
29464 When called, this object must return an object which conforms to the
29465 pretty-printing interface (@pxref{Pretty Printing API}).
29467 The pre-defined function @code{gdb.default_visualizer} may be used to
29468 select a visualizer by following the built-in process
29469 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29470 a varobj is created, and so ordinarily is not needed.
29472 This feature is only available if Python support is enabled. The MI
29473 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29474 can be used to check this.
29476 @subsubheading Example
29478 Resetting the visualizer:
29482 -var-set-visualizer V None
29486 Reselecting the default (type-based) visualizer:
29490 -var-set-visualizer V gdb.default_visualizer
29494 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29495 can be used to instantiate this class for a varobj:
29499 -var-set-visualizer V "lambda val: SomeClass()"
29503 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29504 @node GDB/MI Data Manipulation
29505 @section @sc{gdb/mi} Data Manipulation
29507 @cindex data manipulation, in @sc{gdb/mi}
29508 @cindex @sc{gdb/mi}, data manipulation
29509 This section describes the @sc{gdb/mi} commands that manipulate data:
29510 examine memory and registers, evaluate expressions, etc.
29512 For details about what an addressable memory unit is,
29513 @pxref{addressable memory unit}.
29515 @c REMOVED FROM THE INTERFACE.
29516 @c @subheading -data-assign
29517 @c Change the value of a program variable. Plenty of side effects.
29518 @c @subsubheading GDB Command
29520 @c @subsubheading Example
29523 @subheading The @code{-data-disassemble} Command
29524 @findex -data-disassemble
29526 @subsubheading Synopsis
29530 [ -s @var{start-addr} -e @var{end-addr} ]
29531 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29539 @item @var{start-addr}
29540 is the beginning address (or @code{$pc})
29541 @item @var{end-addr}
29543 @item @var{filename}
29544 is the name of the file to disassemble
29545 @item @var{linenum}
29546 is the line number to disassemble around
29548 is the number of disassembly lines to be produced. If it is -1,
29549 the whole function will be disassembled, in case no @var{end-addr} is
29550 specified. If @var{end-addr} is specified as a non-zero value, and
29551 @var{lines} is lower than the number of disassembly lines between
29552 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29553 displayed; if @var{lines} is higher than the number of lines between
29554 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29559 @item 0 disassembly only
29560 @item 1 mixed source and disassembly (deprecated)
29561 @item 2 disassembly with raw opcodes
29562 @item 3 mixed source and disassembly with raw opcodes (deprecated)
29563 @item 4 mixed source and disassembly
29564 @item 5 mixed source and disassembly with raw opcodes
29567 Modes 1 and 3 are deprecated. The output is ``source centric''
29568 which hasn't proved useful in practice.
29569 @xref{Machine Code}, for a discussion of the difference between
29570 @code{/m} and @code{/s} output of the @code{disassemble} command.
29573 @subsubheading Result
29575 The result of the @code{-data-disassemble} command will be a list named
29576 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29577 used with the @code{-data-disassemble} command.
29579 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29584 The address at which this instruction was disassembled.
29587 The name of the function this instruction is within.
29590 The decimal offset in bytes from the start of @samp{func-name}.
29593 The text disassembly for this @samp{address}.
29596 This field is only present for modes 2, 3 and 5. This contains the raw opcode
29597 bytes for the @samp{inst} field.
29601 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
29602 @samp{src_and_asm_line}, each of which has the following fields:
29606 The line number within @samp{file}.
29609 The file name from the compilation unit. This might be an absolute
29610 file name or a relative file name depending on the compile command
29614 Absolute file name of @samp{file}. It is converted to a canonical form
29615 using the source file search path
29616 (@pxref{Source Path, ,Specifying Source Directories})
29617 and after resolving all the symbolic links.
29619 If the source file is not found this field will contain the path as
29620 present in the debug information.
29622 @item line_asm_insn
29623 This is a list of tuples containing the disassembly for @samp{line} in
29624 @samp{file}. The fields of each tuple are the same as for
29625 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29626 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29631 Note that whatever included in the @samp{inst} field, is not
29632 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29635 @subsubheading @value{GDBN} Command
29637 The corresponding @value{GDBN} command is @samp{disassemble}.
29639 @subsubheading Example
29641 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29645 -data-disassemble -s $pc -e "$pc + 20" -- 0
29648 @{address="0x000107c0",func-name="main",offset="4",
29649 inst="mov 2, %o0"@},
29650 @{address="0x000107c4",func-name="main",offset="8",
29651 inst="sethi %hi(0x11800), %o2"@},
29652 @{address="0x000107c8",func-name="main",offset="12",
29653 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29654 @{address="0x000107cc",func-name="main",offset="16",
29655 inst="sethi %hi(0x11800), %o2"@},
29656 @{address="0x000107d0",func-name="main",offset="20",
29657 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29661 Disassemble the whole @code{main} function. Line 32 is part of
29665 -data-disassemble -f basics.c -l 32 -- 0
29667 @{address="0x000107bc",func-name="main",offset="0",
29668 inst="save %sp, -112, %sp"@},
29669 @{address="0x000107c0",func-name="main",offset="4",
29670 inst="mov 2, %o0"@},
29671 @{address="0x000107c4",func-name="main",offset="8",
29672 inst="sethi %hi(0x11800), %o2"@},
29674 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29675 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29679 Disassemble 3 instructions from the start of @code{main}:
29683 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29685 @{address="0x000107bc",func-name="main",offset="0",
29686 inst="save %sp, -112, %sp"@},
29687 @{address="0x000107c0",func-name="main",offset="4",
29688 inst="mov 2, %o0"@},
29689 @{address="0x000107c4",func-name="main",offset="8",
29690 inst="sethi %hi(0x11800), %o2"@}]
29694 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29698 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29700 src_and_asm_line=@{line="31",
29701 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29702 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29703 line_asm_insn=[@{address="0x000107bc",
29704 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29705 src_and_asm_line=@{line="32",
29706 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29707 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29708 line_asm_insn=[@{address="0x000107c0",
29709 func-name="main",offset="4",inst="mov 2, %o0"@},
29710 @{address="0x000107c4",func-name="main",offset="8",
29711 inst="sethi %hi(0x11800), %o2"@}]@}]
29716 @subheading The @code{-data-evaluate-expression} Command
29717 @findex -data-evaluate-expression
29719 @subsubheading Synopsis
29722 -data-evaluate-expression @var{expr}
29725 Evaluate @var{expr} as an expression. The expression could contain an
29726 inferior function call. The function call will execute synchronously.
29727 If the expression contains spaces, it must be enclosed in double quotes.
29729 @subsubheading @value{GDBN} Command
29731 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29732 @samp{call}. In @code{gdbtk} only, there's a corresponding
29733 @samp{gdb_eval} command.
29735 @subsubheading Example
29737 In the following example, the numbers that precede the commands are the
29738 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29739 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29743 211-data-evaluate-expression A
29746 311-data-evaluate-expression &A
29747 311^done,value="0xefffeb7c"
29749 411-data-evaluate-expression A+3
29752 511-data-evaluate-expression "A + 3"
29758 @subheading The @code{-data-list-changed-registers} Command
29759 @findex -data-list-changed-registers
29761 @subsubheading Synopsis
29764 -data-list-changed-registers
29767 Display a list of the registers that have changed.
29769 @subsubheading @value{GDBN} Command
29771 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29772 has the corresponding command @samp{gdb_changed_register_list}.
29774 @subsubheading Example
29776 On a PPC MBX board:
29784 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29785 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29788 -data-list-changed-registers
29789 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29790 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29791 "24","25","26","27","28","30","31","64","65","66","67","69"]
29796 @subheading The @code{-data-list-register-names} Command
29797 @findex -data-list-register-names
29799 @subsubheading Synopsis
29802 -data-list-register-names [ ( @var{regno} )+ ]
29805 Show a list of register names for the current target. If no arguments
29806 are given, it shows a list of the names of all the registers. If
29807 integer numbers are given as arguments, it will print a list of the
29808 names of the registers corresponding to the arguments. To ensure
29809 consistency between a register name and its number, the output list may
29810 include empty register names.
29812 @subsubheading @value{GDBN} Command
29814 @value{GDBN} does not have a command which corresponds to
29815 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29816 corresponding command @samp{gdb_regnames}.
29818 @subsubheading Example
29820 For the PPC MBX board:
29823 -data-list-register-names
29824 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29825 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29826 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29827 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29828 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29829 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29830 "", "pc","ps","cr","lr","ctr","xer"]
29832 -data-list-register-names 1 2 3
29833 ^done,register-names=["r1","r2","r3"]
29837 @subheading The @code{-data-list-register-values} Command
29838 @findex -data-list-register-values
29840 @subsubheading Synopsis
29843 -data-list-register-values
29844 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29847 Display the registers' contents. The format according to which the
29848 registers' contents are to be returned is given by @var{fmt}, followed
29849 by an optional list of numbers specifying the registers to display. A
29850 missing list of numbers indicates that the contents of all the
29851 registers must be returned. The @code{--skip-unavailable} option
29852 indicates that only the available registers are to be returned.
29854 Allowed formats for @var{fmt} are:
29871 @subsubheading @value{GDBN} Command
29873 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29874 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29876 @subsubheading Example
29878 For a PPC MBX board (note: line breaks are for readability only, they
29879 don't appear in the actual output):
29883 -data-list-register-values r 64 65
29884 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29885 @{number="65",value="0x00029002"@}]
29887 -data-list-register-values x
29888 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29889 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29890 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29891 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29892 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29893 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29894 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29895 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29896 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29897 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29898 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29899 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29900 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29901 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29902 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29903 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29904 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29905 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29906 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29907 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29908 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29909 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29910 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29911 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29912 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29913 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29914 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29915 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29916 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29917 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29918 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29919 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29920 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29921 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29922 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29923 @{number="69",value="0x20002b03"@}]
29928 @subheading The @code{-data-read-memory} Command
29929 @findex -data-read-memory
29931 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29933 @subsubheading Synopsis
29936 -data-read-memory [ -o @var{byte-offset} ]
29937 @var{address} @var{word-format} @var{word-size}
29938 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29945 @item @var{address}
29946 An expression specifying the address of the first memory word to be
29947 read. Complex expressions containing embedded white space should be
29948 quoted using the C convention.
29950 @item @var{word-format}
29951 The format to be used to print the memory words. The notation is the
29952 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29955 @item @var{word-size}
29956 The size of each memory word in bytes.
29958 @item @var{nr-rows}
29959 The number of rows in the output table.
29961 @item @var{nr-cols}
29962 The number of columns in the output table.
29965 If present, indicates that each row should include an @sc{ascii} dump. The
29966 value of @var{aschar} is used as a padding character when a byte is not a
29967 member of the printable @sc{ascii} character set (printable @sc{ascii}
29968 characters are those whose code is between 32 and 126, inclusively).
29970 @item @var{byte-offset}
29971 An offset to add to the @var{address} before fetching memory.
29974 This command displays memory contents as a table of @var{nr-rows} by
29975 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29976 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29977 (returned as @samp{total-bytes}). Should less than the requested number
29978 of bytes be returned by the target, the missing words are identified
29979 using @samp{N/A}. The number of bytes read from the target is returned
29980 in @samp{nr-bytes} and the starting address used to read memory in
29983 The address of the next/previous row or page is available in
29984 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29987 @subsubheading @value{GDBN} Command
29989 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29990 @samp{gdb_get_mem} memory read command.
29992 @subsubheading Example
29994 Read six bytes of memory starting at @code{bytes+6} but then offset by
29995 @code{-6} bytes. Format as three rows of two columns. One byte per
29996 word. Display each word in hex.
30000 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30001 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30002 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30003 prev-page="0x0000138a",memory=[
30004 @{addr="0x00001390",data=["0x00","0x01"]@},
30005 @{addr="0x00001392",data=["0x02","0x03"]@},
30006 @{addr="0x00001394",data=["0x04","0x05"]@}]
30010 Read two bytes of memory starting at address @code{shorts + 64} and
30011 display as a single word formatted in decimal.
30015 5-data-read-memory shorts+64 d 2 1 1
30016 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30017 next-row="0x00001512",prev-row="0x0000150e",
30018 next-page="0x00001512",prev-page="0x0000150e",memory=[
30019 @{addr="0x00001510",data=["128"]@}]
30023 Read thirty two bytes of memory starting at @code{bytes+16} and format
30024 as eight rows of four columns. Include a string encoding with @samp{x}
30025 used as the non-printable character.
30029 4-data-read-memory bytes+16 x 1 8 4 x
30030 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30031 next-row="0x000013c0",prev-row="0x0000139c",
30032 next-page="0x000013c0",prev-page="0x00001380",memory=[
30033 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30034 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30035 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30036 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30037 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30038 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30039 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30040 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30044 @subheading The @code{-data-read-memory-bytes} Command
30045 @findex -data-read-memory-bytes
30047 @subsubheading Synopsis
30050 -data-read-memory-bytes [ -o @var{offset} ]
30051 @var{address} @var{count}
30058 @item @var{address}
30059 An expression specifying the address of the first addressable memory unit
30060 to be read. Complex expressions containing embedded white space should be
30061 quoted using the C convention.
30064 The number of addressable memory units to read. This should be an integer
30068 The offset relative to @var{address} at which to start reading. This
30069 should be an integer literal. This option is provided so that a frontend
30070 is not required to first evaluate address and then perform address
30071 arithmetics itself.
30075 This command attempts to read all accessible memory regions in the
30076 specified range. First, all regions marked as unreadable in the memory
30077 map (if one is defined) will be skipped. @xref{Memory Region
30078 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30079 regions. For each one, if reading full region results in an errors,
30080 @value{GDBN} will try to read a subset of the region.
30082 In general, every single memory unit in the region may be readable or not,
30083 and the only way to read every readable unit is to try a read at
30084 every address, which is not practical. Therefore, @value{GDBN} will
30085 attempt to read all accessible memory units at either beginning or the end
30086 of the region, using a binary division scheme. This heuristic works
30087 well for reading accross a memory map boundary. Note that if a region
30088 has a readable range that is neither at the beginning or the end,
30089 @value{GDBN} will not read it.
30091 The result record (@pxref{GDB/MI Result Records}) that is output of
30092 the command includes a field named @samp{memory} whose content is a
30093 list of tuples. Each tuple represent a successfully read memory block
30094 and has the following fields:
30098 The start address of the memory block, as hexadecimal literal.
30101 The end address of the memory block, as hexadecimal literal.
30104 The offset of the memory block, as hexadecimal literal, relative to
30105 the start address passed to @code{-data-read-memory-bytes}.
30108 The contents of the memory block, in hex.
30114 @subsubheading @value{GDBN} Command
30116 The corresponding @value{GDBN} command is @samp{x}.
30118 @subsubheading Example
30122 -data-read-memory-bytes &a 10
30123 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30125 contents="01000000020000000300"@}]
30130 @subheading The @code{-data-write-memory-bytes} Command
30131 @findex -data-write-memory-bytes
30133 @subsubheading Synopsis
30136 -data-write-memory-bytes @var{address} @var{contents}
30137 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30144 @item @var{address}
30145 An expression specifying the address of the first addressable memory unit
30146 to be written. Complex expressions containing embedded white space should
30147 be quoted using the C convention.
30149 @item @var{contents}
30150 The hex-encoded data to write. It is an error if @var{contents} does
30151 not represent an integral number of addressable memory units.
30154 Optional argument indicating the number of addressable memory units to be
30155 written. If @var{count} is greater than @var{contents}' length,
30156 @value{GDBN} will repeatedly write @var{contents} until it fills
30157 @var{count} memory units.
30161 @subsubheading @value{GDBN} Command
30163 There's no corresponding @value{GDBN} command.
30165 @subsubheading Example
30169 -data-write-memory-bytes &a "aabbccdd"
30176 -data-write-memory-bytes &a "aabbccdd" 16e
30181 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30182 @node GDB/MI Tracepoint Commands
30183 @section @sc{gdb/mi} Tracepoint Commands
30185 The commands defined in this section implement MI support for
30186 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30188 @subheading The @code{-trace-find} Command
30189 @findex -trace-find
30191 @subsubheading Synopsis
30194 -trace-find @var{mode} [@var{parameters}@dots{}]
30197 Find a trace frame using criteria defined by @var{mode} and
30198 @var{parameters}. The following table lists permissible
30199 modes and their parameters. For details of operation, see @ref{tfind}.
30204 No parameters are required. Stops examining trace frames.
30207 An integer is required as parameter. Selects tracepoint frame with
30210 @item tracepoint-number
30211 An integer is required as parameter. Finds next
30212 trace frame that corresponds to tracepoint with the specified number.
30215 An address is required as parameter. Finds
30216 next trace frame that corresponds to any tracepoint at the specified
30219 @item pc-inside-range
30220 Two addresses are required as parameters. Finds next trace
30221 frame that corresponds to a tracepoint at an address inside the
30222 specified range. Both bounds are considered to be inside the range.
30224 @item pc-outside-range
30225 Two addresses are required as parameters. Finds
30226 next trace frame that corresponds to a tracepoint at an address outside
30227 the specified range. Both bounds are considered to be inside the range.
30230 Line specification is required as parameter. @xref{Specify Location}.
30231 Finds next trace frame that corresponds to a tracepoint at
30232 the specified location.
30236 If @samp{none} was passed as @var{mode}, the response does not
30237 have fields. Otherwise, the response may have the following fields:
30241 This field has either @samp{0} or @samp{1} as the value, depending
30242 on whether a matching tracepoint was found.
30245 The index of the found traceframe. This field is present iff
30246 the @samp{found} field has value of @samp{1}.
30249 The index of the found tracepoint. This field is present iff
30250 the @samp{found} field has value of @samp{1}.
30253 The information about the frame corresponding to the found trace
30254 frame. This field is present only if a trace frame was found.
30255 @xref{GDB/MI Frame Information}, for description of this field.
30259 @subsubheading @value{GDBN} Command
30261 The corresponding @value{GDBN} command is @samp{tfind}.
30263 @subheading -trace-define-variable
30264 @findex -trace-define-variable
30266 @subsubheading Synopsis
30269 -trace-define-variable @var{name} [ @var{value} ]
30272 Create trace variable @var{name} if it does not exist. If
30273 @var{value} is specified, sets the initial value of the specified
30274 trace variable to that value. Note that the @var{name} should start
30275 with the @samp{$} character.
30277 @subsubheading @value{GDBN} Command
30279 The corresponding @value{GDBN} command is @samp{tvariable}.
30281 @subheading The @code{-trace-frame-collected} Command
30282 @findex -trace-frame-collected
30284 @subsubheading Synopsis
30287 -trace-frame-collected
30288 [--var-print-values @var{var_pval}]
30289 [--comp-print-values @var{comp_pval}]
30290 [--registers-format @var{regformat}]
30291 [--memory-contents]
30294 This command returns the set of collected objects, register names,
30295 trace state variable names, memory ranges and computed expressions
30296 that have been collected at a particular trace frame. The optional
30297 parameters to the command affect the output format in different ways.
30298 See the output description table below for more details.
30300 The reported names can be used in the normal manner to create
30301 varobjs and inspect the objects themselves. The items returned by
30302 this command are categorized so that it is clear which is a variable,
30303 which is a register, which is a trace state variable, which is a
30304 memory range and which is a computed expression.
30306 For instance, if the actions were
30308 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30309 collect *(int*)0xaf02bef0@@40
30313 the object collected in its entirety would be @code{myVar}. The
30314 object @code{myArray} would be partially collected, because only the
30315 element at index @code{myIndex} would be collected. The remaining
30316 objects would be computed expressions.
30318 An example output would be:
30322 -trace-frame-collected
30324 explicit-variables=[@{name="myVar",value="1"@}],
30325 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30326 @{name="myObj.field",value="0"@},
30327 @{name="myPtr->field",value="1"@},
30328 @{name="myCount + 2",value="3"@},
30329 @{name="$tvar1 + 1",value="43970027"@}],
30330 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30331 @{number="1",value="0x0"@},
30332 @{number="2",value="0x4"@},
30334 @{number="125",value="0x0"@}],
30335 tvars=[@{name="$tvar1",current="43970026"@}],
30336 memory=[@{address="0x0000000000602264",length="4"@},
30337 @{address="0x0000000000615bc0",length="4"@}]
30344 @item explicit-variables
30345 The set of objects that have been collected in their entirety (as
30346 opposed to collecting just a few elements of an array or a few struct
30347 members). For each object, its name and value are printed.
30348 The @code{--var-print-values} option affects how or whether the value
30349 field is output. If @var{var_pval} is 0, then print only the names;
30350 if it is 1, print also their values; and if it is 2, print the name,
30351 type and value for simple data types, and the name and type for
30352 arrays, structures and unions.
30354 @item computed-expressions
30355 The set of computed expressions that have been collected at the
30356 current trace frame. The @code{--comp-print-values} option affects
30357 this set like the @code{--var-print-values} option affects the
30358 @code{explicit-variables} set. See above.
30361 The registers that have been collected at the current trace frame.
30362 For each register collected, the name and current value are returned.
30363 The value is formatted according to the @code{--registers-format}
30364 option. See the @command{-data-list-register-values} command for a
30365 list of the allowed formats. The default is @samp{x}.
30368 The trace state variables that have been collected at the current
30369 trace frame. For each trace state variable collected, the name and
30370 current value are returned.
30373 The set of memory ranges that have been collected at the current trace
30374 frame. Its content is a list of tuples. Each tuple represents a
30375 collected memory range and has the following fields:
30379 The start address of the memory range, as hexadecimal literal.
30382 The length of the memory range, as decimal literal.
30385 The contents of the memory block, in hex. This field is only present
30386 if the @code{--memory-contents} option is specified.
30392 @subsubheading @value{GDBN} Command
30394 There is no corresponding @value{GDBN} command.
30396 @subsubheading Example
30398 @subheading -trace-list-variables
30399 @findex -trace-list-variables
30401 @subsubheading Synopsis
30404 -trace-list-variables
30407 Return a table of all defined trace variables. Each element of the
30408 table has the following fields:
30412 The name of the trace variable. This field is always present.
30415 The initial value. This is a 64-bit signed integer. This
30416 field is always present.
30419 The value the trace variable has at the moment. This is a 64-bit
30420 signed integer. This field is absent iff current value is
30421 not defined, for example if the trace was never run, or is
30426 @subsubheading @value{GDBN} Command
30428 The corresponding @value{GDBN} command is @samp{tvariables}.
30430 @subsubheading Example
30434 -trace-list-variables
30435 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30436 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30437 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30438 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30439 body=[variable=@{name="$trace_timestamp",initial="0"@}
30440 variable=@{name="$foo",initial="10",current="15"@}]@}
30444 @subheading -trace-save
30445 @findex -trace-save
30447 @subsubheading Synopsis
30450 -trace-save [-r ] @var{filename}
30453 Saves the collected trace data to @var{filename}. Without the
30454 @samp{-r} option, the data is downloaded from the target and saved
30455 in a local file. With the @samp{-r} option the target is asked
30456 to perform the save.
30458 @subsubheading @value{GDBN} Command
30460 The corresponding @value{GDBN} command is @samp{tsave}.
30463 @subheading -trace-start
30464 @findex -trace-start
30466 @subsubheading Synopsis
30472 Starts a tracing experiments. The result of this command does not
30475 @subsubheading @value{GDBN} Command
30477 The corresponding @value{GDBN} command is @samp{tstart}.
30479 @subheading -trace-status
30480 @findex -trace-status
30482 @subsubheading Synopsis
30488 Obtains the status of a tracing experiment. The result may include
30489 the following fields:
30494 May have a value of either @samp{0}, when no tracing operations are
30495 supported, @samp{1}, when all tracing operations are supported, or
30496 @samp{file} when examining trace file. In the latter case, examining
30497 of trace frame is possible but new tracing experiement cannot be
30498 started. This field is always present.
30501 May have a value of either @samp{0} or @samp{1} depending on whether
30502 tracing experiement is in progress on target. This field is present
30503 if @samp{supported} field is not @samp{0}.
30506 Report the reason why the tracing was stopped last time. This field
30507 may be absent iff tracing was never stopped on target yet. The
30508 value of @samp{request} means the tracing was stopped as result of
30509 the @code{-trace-stop} command. The value of @samp{overflow} means
30510 the tracing buffer is full. The value of @samp{disconnection} means
30511 tracing was automatically stopped when @value{GDBN} has disconnected.
30512 The value of @samp{passcount} means tracing was stopped when a
30513 tracepoint was passed a maximal number of times for that tracepoint.
30514 This field is present if @samp{supported} field is not @samp{0}.
30516 @item stopping-tracepoint
30517 The number of tracepoint whose passcount as exceeded. This field is
30518 present iff the @samp{stop-reason} field has the value of
30522 @itemx frames-created
30523 The @samp{frames} field is a count of the total number of trace frames
30524 in the trace buffer, while @samp{frames-created} is the total created
30525 during the run, including ones that were discarded, such as when a
30526 circular trace buffer filled up. Both fields are optional.
30530 These fields tell the current size of the tracing buffer and the
30531 remaining space. These fields are optional.
30534 The value of the circular trace buffer flag. @code{1} means that the
30535 trace buffer is circular and old trace frames will be discarded if
30536 necessary to make room, @code{0} means that the trace buffer is linear
30540 The value of the disconnected tracing flag. @code{1} means that
30541 tracing will continue after @value{GDBN} disconnects, @code{0} means
30542 that the trace run will stop.
30545 The filename of the trace file being examined. This field is
30546 optional, and only present when examining a trace file.
30550 @subsubheading @value{GDBN} Command
30552 The corresponding @value{GDBN} command is @samp{tstatus}.
30554 @subheading -trace-stop
30555 @findex -trace-stop
30557 @subsubheading Synopsis
30563 Stops a tracing experiment. The result of this command has the same
30564 fields as @code{-trace-status}, except that the @samp{supported} and
30565 @samp{running} fields are not output.
30567 @subsubheading @value{GDBN} Command
30569 The corresponding @value{GDBN} command is @samp{tstop}.
30572 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30573 @node GDB/MI Symbol Query
30574 @section @sc{gdb/mi} Symbol Query Commands
30578 @subheading The @code{-symbol-info-address} Command
30579 @findex -symbol-info-address
30581 @subsubheading Synopsis
30584 -symbol-info-address @var{symbol}
30587 Describe where @var{symbol} is stored.
30589 @subsubheading @value{GDBN} Command
30591 The corresponding @value{GDBN} command is @samp{info address}.
30593 @subsubheading Example
30597 @subheading The @code{-symbol-info-file} Command
30598 @findex -symbol-info-file
30600 @subsubheading Synopsis
30606 Show the file for the symbol.
30608 @subsubheading @value{GDBN} Command
30610 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30611 @samp{gdb_find_file}.
30613 @subsubheading Example
30617 @subheading The @code{-symbol-info-function} Command
30618 @findex -symbol-info-function
30620 @subsubheading Synopsis
30623 -symbol-info-function
30626 Show which function the symbol lives in.
30628 @subsubheading @value{GDBN} Command
30630 @samp{gdb_get_function} in @code{gdbtk}.
30632 @subsubheading Example
30636 @subheading The @code{-symbol-info-line} Command
30637 @findex -symbol-info-line
30639 @subsubheading Synopsis
30645 Show the core addresses of the code for a source line.
30647 @subsubheading @value{GDBN} Command
30649 The corresponding @value{GDBN} command is @samp{info line}.
30650 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30652 @subsubheading Example
30656 @subheading The @code{-symbol-info-symbol} Command
30657 @findex -symbol-info-symbol
30659 @subsubheading Synopsis
30662 -symbol-info-symbol @var{addr}
30665 Describe what symbol is at location @var{addr}.
30667 @subsubheading @value{GDBN} Command
30669 The corresponding @value{GDBN} command is @samp{info symbol}.
30671 @subsubheading Example
30675 @subheading The @code{-symbol-list-functions} Command
30676 @findex -symbol-list-functions
30678 @subsubheading Synopsis
30681 -symbol-list-functions
30684 List the functions in the executable.
30686 @subsubheading @value{GDBN} Command
30688 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30689 @samp{gdb_search} in @code{gdbtk}.
30691 @subsubheading Example
30696 @subheading The @code{-symbol-list-lines} Command
30697 @findex -symbol-list-lines
30699 @subsubheading Synopsis
30702 -symbol-list-lines @var{filename}
30705 Print the list of lines that contain code and their associated program
30706 addresses for the given source filename. The entries are sorted in
30707 ascending PC order.
30709 @subsubheading @value{GDBN} Command
30711 There is no corresponding @value{GDBN} command.
30713 @subsubheading Example
30716 -symbol-list-lines basics.c
30717 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30723 @subheading The @code{-symbol-list-types} Command
30724 @findex -symbol-list-types
30726 @subsubheading Synopsis
30732 List all the type names.
30734 @subsubheading @value{GDBN} Command
30736 The corresponding commands are @samp{info types} in @value{GDBN},
30737 @samp{gdb_search} in @code{gdbtk}.
30739 @subsubheading Example
30743 @subheading The @code{-symbol-list-variables} Command
30744 @findex -symbol-list-variables
30746 @subsubheading Synopsis
30749 -symbol-list-variables
30752 List all the global and static variable names.
30754 @subsubheading @value{GDBN} Command
30756 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30758 @subsubheading Example
30762 @subheading The @code{-symbol-locate} Command
30763 @findex -symbol-locate
30765 @subsubheading Synopsis
30771 @subsubheading @value{GDBN} Command
30773 @samp{gdb_loc} in @code{gdbtk}.
30775 @subsubheading Example
30779 @subheading The @code{-symbol-type} Command
30780 @findex -symbol-type
30782 @subsubheading Synopsis
30785 -symbol-type @var{variable}
30788 Show type of @var{variable}.
30790 @subsubheading @value{GDBN} Command
30792 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30793 @samp{gdb_obj_variable}.
30795 @subsubheading Example
30800 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30801 @node GDB/MI File Commands
30802 @section @sc{gdb/mi} File Commands
30804 This section describes the GDB/MI commands to specify executable file names
30805 and to read in and obtain symbol table information.
30807 @subheading The @code{-file-exec-and-symbols} Command
30808 @findex -file-exec-and-symbols
30810 @subsubheading Synopsis
30813 -file-exec-and-symbols @var{file}
30816 Specify the executable file to be debugged. This file is the one from
30817 which the symbol table is also read. If no file is specified, the
30818 command clears the executable and symbol information. If breakpoints
30819 are set when using this command with no arguments, @value{GDBN} will produce
30820 error messages. Otherwise, no output is produced, except a completion
30823 @subsubheading @value{GDBN} Command
30825 The corresponding @value{GDBN} command is @samp{file}.
30827 @subsubheading Example
30831 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30837 @subheading The @code{-file-exec-file} Command
30838 @findex -file-exec-file
30840 @subsubheading Synopsis
30843 -file-exec-file @var{file}
30846 Specify the executable file to be debugged. Unlike
30847 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30848 from this file. If used without argument, @value{GDBN} clears the information
30849 about the executable file. No output is produced, except a completion
30852 @subsubheading @value{GDBN} Command
30854 The corresponding @value{GDBN} command is @samp{exec-file}.
30856 @subsubheading Example
30860 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30867 @subheading The @code{-file-list-exec-sections} Command
30868 @findex -file-list-exec-sections
30870 @subsubheading Synopsis
30873 -file-list-exec-sections
30876 List the sections of the current executable file.
30878 @subsubheading @value{GDBN} Command
30880 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30881 information as this command. @code{gdbtk} has a corresponding command
30882 @samp{gdb_load_info}.
30884 @subsubheading Example
30889 @subheading The @code{-file-list-exec-source-file} Command
30890 @findex -file-list-exec-source-file
30892 @subsubheading Synopsis
30895 -file-list-exec-source-file
30898 List the line number, the current source file, and the absolute path
30899 to the current source file for the current executable. The macro
30900 information field has a value of @samp{1} or @samp{0} depending on
30901 whether or not the file includes preprocessor macro information.
30903 @subsubheading @value{GDBN} Command
30905 The @value{GDBN} equivalent is @samp{info source}
30907 @subsubheading Example
30911 123-file-list-exec-source-file
30912 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30917 @subheading The @code{-file-list-exec-source-files} Command
30918 @findex -file-list-exec-source-files
30920 @subsubheading Synopsis
30923 -file-list-exec-source-files
30926 List the source files for the current executable.
30928 It will always output both the filename and fullname (absolute file
30929 name) of a source file.
30931 @subsubheading @value{GDBN} Command
30933 The @value{GDBN} equivalent is @samp{info sources}.
30934 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30936 @subsubheading Example
30939 -file-list-exec-source-files
30941 @{file=foo.c,fullname=/home/foo.c@},
30942 @{file=/home/bar.c,fullname=/home/bar.c@},
30943 @{file=gdb_could_not_find_fullpath.c@}]
30948 @subheading The @code{-file-list-shared-libraries} Command
30949 @findex -file-list-shared-libraries
30951 @subsubheading Synopsis
30954 -file-list-shared-libraries
30957 List the shared libraries in the program.
30959 @subsubheading @value{GDBN} Command
30961 The corresponding @value{GDBN} command is @samp{info shared}.
30963 @subsubheading Example
30967 @subheading The @code{-file-list-symbol-files} Command
30968 @findex -file-list-symbol-files
30970 @subsubheading Synopsis
30973 -file-list-symbol-files
30978 @subsubheading @value{GDBN} Command
30980 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30982 @subsubheading Example
30987 @subheading The @code{-file-symbol-file} Command
30988 @findex -file-symbol-file
30990 @subsubheading Synopsis
30993 -file-symbol-file @var{file}
30996 Read symbol table info from the specified @var{file} argument. When
30997 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30998 produced, except for a completion notification.
31000 @subsubheading @value{GDBN} Command
31002 The corresponding @value{GDBN} command is @samp{symbol-file}.
31004 @subsubheading Example
31008 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31014 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31015 @node GDB/MI Memory Overlay Commands
31016 @section @sc{gdb/mi} Memory Overlay Commands
31018 The memory overlay commands are not implemented.
31020 @c @subheading -overlay-auto
31022 @c @subheading -overlay-list-mapping-state
31024 @c @subheading -overlay-list-overlays
31026 @c @subheading -overlay-map
31028 @c @subheading -overlay-off
31030 @c @subheading -overlay-on
31032 @c @subheading -overlay-unmap
31034 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31035 @node GDB/MI Signal Handling Commands
31036 @section @sc{gdb/mi} Signal Handling Commands
31038 Signal handling commands are not implemented.
31040 @c @subheading -signal-handle
31042 @c @subheading -signal-list-handle-actions
31044 @c @subheading -signal-list-signal-types
31048 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31049 @node GDB/MI Target Manipulation
31050 @section @sc{gdb/mi} Target Manipulation Commands
31053 @subheading The @code{-target-attach} Command
31054 @findex -target-attach
31056 @subsubheading Synopsis
31059 -target-attach @var{pid} | @var{gid} | @var{file}
31062 Attach to a process @var{pid} or a file @var{file} outside of
31063 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31064 group, the id previously returned by
31065 @samp{-list-thread-groups --available} must be used.
31067 @subsubheading @value{GDBN} Command
31069 The corresponding @value{GDBN} command is @samp{attach}.
31071 @subsubheading Example
31075 =thread-created,id="1"
31076 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31082 @subheading The @code{-target-compare-sections} Command
31083 @findex -target-compare-sections
31085 @subsubheading Synopsis
31088 -target-compare-sections [ @var{section} ]
31091 Compare data of section @var{section} on target to the exec file.
31092 Without the argument, all sections are compared.
31094 @subsubheading @value{GDBN} Command
31096 The @value{GDBN} equivalent is @samp{compare-sections}.
31098 @subsubheading Example
31103 @subheading The @code{-target-detach} Command
31104 @findex -target-detach
31106 @subsubheading Synopsis
31109 -target-detach [ @var{pid} | @var{gid} ]
31112 Detach from the remote target which normally resumes its execution.
31113 If either @var{pid} or @var{gid} is specified, detaches from either
31114 the specified process, or specified thread group. There's no output.
31116 @subsubheading @value{GDBN} Command
31118 The corresponding @value{GDBN} command is @samp{detach}.
31120 @subsubheading Example
31130 @subheading The @code{-target-disconnect} Command
31131 @findex -target-disconnect
31133 @subsubheading Synopsis
31139 Disconnect from the remote target. There's no output and the target is
31140 generally not resumed.
31142 @subsubheading @value{GDBN} Command
31144 The corresponding @value{GDBN} command is @samp{disconnect}.
31146 @subsubheading Example
31156 @subheading The @code{-target-download} Command
31157 @findex -target-download
31159 @subsubheading Synopsis
31165 Loads the executable onto the remote target.
31166 It prints out an update message every half second, which includes the fields:
31170 The name of the section.
31172 The size of what has been sent so far for that section.
31174 The size of the section.
31176 The total size of what was sent so far (the current and the previous sections).
31178 The size of the overall executable to download.
31182 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31183 @sc{gdb/mi} Output Syntax}).
31185 In addition, it prints the name and size of the sections, as they are
31186 downloaded. These messages include the following fields:
31190 The name of the section.
31192 The size of the section.
31194 The size of the overall executable to download.
31198 At the end, a summary is printed.
31200 @subsubheading @value{GDBN} Command
31202 The corresponding @value{GDBN} command is @samp{load}.
31204 @subsubheading Example
31206 Note: each status message appears on a single line. Here the messages
31207 have been broken down so that they can fit onto a page.
31212 +download,@{section=".text",section-size="6668",total-size="9880"@}
31213 +download,@{section=".text",section-sent="512",section-size="6668",
31214 total-sent="512",total-size="9880"@}
31215 +download,@{section=".text",section-sent="1024",section-size="6668",
31216 total-sent="1024",total-size="9880"@}
31217 +download,@{section=".text",section-sent="1536",section-size="6668",
31218 total-sent="1536",total-size="9880"@}
31219 +download,@{section=".text",section-sent="2048",section-size="6668",
31220 total-sent="2048",total-size="9880"@}
31221 +download,@{section=".text",section-sent="2560",section-size="6668",
31222 total-sent="2560",total-size="9880"@}
31223 +download,@{section=".text",section-sent="3072",section-size="6668",
31224 total-sent="3072",total-size="9880"@}
31225 +download,@{section=".text",section-sent="3584",section-size="6668",
31226 total-sent="3584",total-size="9880"@}
31227 +download,@{section=".text",section-sent="4096",section-size="6668",
31228 total-sent="4096",total-size="9880"@}
31229 +download,@{section=".text",section-sent="4608",section-size="6668",
31230 total-sent="4608",total-size="9880"@}
31231 +download,@{section=".text",section-sent="5120",section-size="6668",
31232 total-sent="5120",total-size="9880"@}
31233 +download,@{section=".text",section-sent="5632",section-size="6668",
31234 total-sent="5632",total-size="9880"@}
31235 +download,@{section=".text",section-sent="6144",section-size="6668",
31236 total-sent="6144",total-size="9880"@}
31237 +download,@{section=".text",section-sent="6656",section-size="6668",
31238 total-sent="6656",total-size="9880"@}
31239 +download,@{section=".init",section-size="28",total-size="9880"@}
31240 +download,@{section=".fini",section-size="28",total-size="9880"@}
31241 +download,@{section=".data",section-size="3156",total-size="9880"@}
31242 +download,@{section=".data",section-sent="512",section-size="3156",
31243 total-sent="7236",total-size="9880"@}
31244 +download,@{section=".data",section-sent="1024",section-size="3156",
31245 total-sent="7748",total-size="9880"@}
31246 +download,@{section=".data",section-sent="1536",section-size="3156",
31247 total-sent="8260",total-size="9880"@}
31248 +download,@{section=".data",section-sent="2048",section-size="3156",
31249 total-sent="8772",total-size="9880"@}
31250 +download,@{section=".data",section-sent="2560",section-size="3156",
31251 total-sent="9284",total-size="9880"@}
31252 +download,@{section=".data",section-sent="3072",section-size="3156",
31253 total-sent="9796",total-size="9880"@}
31254 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31261 @subheading The @code{-target-exec-status} Command
31262 @findex -target-exec-status
31264 @subsubheading Synopsis
31267 -target-exec-status
31270 Provide information on the state of the target (whether it is running or
31271 not, for instance).
31273 @subsubheading @value{GDBN} Command
31275 There's no equivalent @value{GDBN} command.
31277 @subsubheading Example
31281 @subheading The @code{-target-list-available-targets} Command
31282 @findex -target-list-available-targets
31284 @subsubheading Synopsis
31287 -target-list-available-targets
31290 List the possible targets to connect to.
31292 @subsubheading @value{GDBN} Command
31294 The corresponding @value{GDBN} command is @samp{help target}.
31296 @subsubheading Example
31300 @subheading The @code{-target-list-current-targets} Command
31301 @findex -target-list-current-targets
31303 @subsubheading Synopsis
31306 -target-list-current-targets
31309 Describe the current target.
31311 @subsubheading @value{GDBN} Command
31313 The corresponding information is printed by @samp{info file} (among
31316 @subsubheading Example
31320 @subheading The @code{-target-list-parameters} Command
31321 @findex -target-list-parameters
31323 @subsubheading Synopsis
31326 -target-list-parameters
31332 @subsubheading @value{GDBN} Command
31336 @subsubheading Example
31340 @subheading The @code{-target-select} Command
31341 @findex -target-select
31343 @subsubheading Synopsis
31346 -target-select @var{type} @var{parameters @dots{}}
31349 Connect @value{GDBN} to the remote target. This command takes two args:
31353 The type of target, for instance @samp{remote}, etc.
31354 @item @var{parameters}
31355 Device names, host names and the like. @xref{Target Commands, ,
31356 Commands for Managing Targets}, for more details.
31359 The output is a connection notification, followed by the address at
31360 which the target program is, in the following form:
31363 ^connected,addr="@var{address}",func="@var{function name}",
31364 args=[@var{arg list}]
31367 @subsubheading @value{GDBN} Command
31369 The corresponding @value{GDBN} command is @samp{target}.
31371 @subsubheading Example
31375 -target-select remote /dev/ttya
31376 ^connected,addr="0xfe00a300",func="??",args=[]
31380 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31381 @node GDB/MI File Transfer Commands
31382 @section @sc{gdb/mi} File Transfer Commands
31385 @subheading The @code{-target-file-put} Command
31386 @findex -target-file-put
31388 @subsubheading Synopsis
31391 -target-file-put @var{hostfile} @var{targetfile}
31394 Copy file @var{hostfile} from the host system (the machine running
31395 @value{GDBN}) to @var{targetfile} on the target system.
31397 @subsubheading @value{GDBN} Command
31399 The corresponding @value{GDBN} command is @samp{remote put}.
31401 @subsubheading Example
31405 -target-file-put localfile remotefile
31411 @subheading The @code{-target-file-get} Command
31412 @findex -target-file-get
31414 @subsubheading Synopsis
31417 -target-file-get @var{targetfile} @var{hostfile}
31420 Copy file @var{targetfile} from the target system to @var{hostfile}
31421 on the host system.
31423 @subsubheading @value{GDBN} Command
31425 The corresponding @value{GDBN} command is @samp{remote get}.
31427 @subsubheading Example
31431 -target-file-get remotefile localfile
31437 @subheading The @code{-target-file-delete} Command
31438 @findex -target-file-delete
31440 @subsubheading Synopsis
31443 -target-file-delete @var{targetfile}
31446 Delete @var{targetfile} from the target system.
31448 @subsubheading @value{GDBN} Command
31450 The corresponding @value{GDBN} command is @samp{remote delete}.
31452 @subsubheading Example
31456 -target-file-delete remotefile
31462 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31463 @node GDB/MI Ada Exceptions Commands
31464 @section Ada Exceptions @sc{gdb/mi} Commands
31466 @subheading The @code{-info-ada-exceptions} Command
31467 @findex -info-ada-exceptions
31469 @subsubheading Synopsis
31472 -info-ada-exceptions [ @var{regexp}]
31475 List all Ada exceptions defined within the program being debugged.
31476 With a regular expression @var{regexp}, only those exceptions whose
31477 names match @var{regexp} are listed.
31479 @subsubheading @value{GDBN} Command
31481 The corresponding @value{GDBN} command is @samp{info exceptions}.
31483 @subsubheading Result
31485 The result is a table of Ada exceptions. The following columns are
31486 defined for each exception:
31490 The name of the exception.
31493 The address of the exception.
31497 @subsubheading Example
31500 -info-ada-exceptions aint
31501 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31502 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31503 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31504 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31505 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31508 @subheading Catching Ada Exceptions
31510 The commands describing how to ask @value{GDBN} to stop when a program
31511 raises an exception are described at @ref{Ada Exception GDB/MI
31512 Catchpoint Commands}.
31515 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31516 @node GDB/MI Support Commands
31517 @section @sc{gdb/mi} Support Commands
31519 Since new commands and features get regularly added to @sc{gdb/mi},
31520 some commands are available to help front-ends query the debugger
31521 about support for these capabilities. Similarly, it is also possible
31522 to query @value{GDBN} about target support of certain features.
31524 @subheading The @code{-info-gdb-mi-command} Command
31525 @cindex @code{-info-gdb-mi-command}
31526 @findex -info-gdb-mi-command
31528 @subsubheading Synopsis
31531 -info-gdb-mi-command @var{cmd_name}
31534 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31536 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31537 is technically not part of the command name (@pxref{GDB/MI Input
31538 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31539 for ease of use, this command also accepts the form with the leading
31542 @subsubheading @value{GDBN} Command
31544 There is no corresponding @value{GDBN} command.
31546 @subsubheading Result
31548 The result is a tuple. There is currently only one field:
31552 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31553 @code{"false"} otherwise.
31557 @subsubheading Example
31559 Here is an example where the @sc{gdb/mi} command does not exist:
31562 -info-gdb-mi-command unsupported-command
31563 ^done,command=@{exists="false"@}
31567 And here is an example where the @sc{gdb/mi} command is known
31571 -info-gdb-mi-command symbol-list-lines
31572 ^done,command=@{exists="true"@}
31575 @subheading The @code{-list-features} Command
31576 @findex -list-features
31577 @cindex supported @sc{gdb/mi} features, list
31579 Returns a list of particular features of the MI protocol that
31580 this version of gdb implements. A feature can be a command,
31581 or a new field in an output of some command, or even an
31582 important bugfix. While a frontend can sometimes detect presence
31583 of a feature at runtime, it is easier to perform detection at debugger
31586 The command returns a list of strings, with each string naming an
31587 available feature. Each returned string is just a name, it does not
31588 have any internal structure. The list of possible feature names
31594 (gdb) -list-features
31595 ^done,result=["feature1","feature2"]
31598 The current list of features is:
31601 @item frozen-varobjs
31602 Indicates support for the @code{-var-set-frozen} command, as well
31603 as possible presense of the @code{frozen} field in the output
31604 of @code{-varobj-create}.
31605 @item pending-breakpoints
31606 Indicates support for the @option{-f} option to the @code{-break-insert}
31609 Indicates Python scripting support, Python-based
31610 pretty-printing commands, and possible presence of the
31611 @samp{display_hint} field in the output of @code{-var-list-children}
31613 Indicates support for the @code{-thread-info} command.
31614 @item data-read-memory-bytes
31615 Indicates support for the @code{-data-read-memory-bytes} and the
31616 @code{-data-write-memory-bytes} commands.
31617 @item breakpoint-notifications
31618 Indicates that changes to breakpoints and breakpoints created via the
31619 CLI will be announced via async records.
31620 @item ada-task-info
31621 Indicates support for the @code{-ada-task-info} command.
31622 @item language-option
31623 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31624 option (@pxref{Context management}).
31625 @item info-gdb-mi-command
31626 Indicates support for the @code{-info-gdb-mi-command} command.
31627 @item undefined-command-error-code
31628 Indicates support for the "undefined-command" error code in error result
31629 records, produced when trying to execute an undefined @sc{gdb/mi} command
31630 (@pxref{GDB/MI Result Records}).
31631 @item exec-run-start-option
31632 Indicates that the @code{-exec-run} command supports the @option{--start}
31633 option (@pxref{GDB/MI Program Execution}).
31636 @subheading The @code{-list-target-features} Command
31637 @findex -list-target-features
31639 Returns a list of particular features that are supported by the
31640 target. Those features affect the permitted MI commands, but
31641 unlike the features reported by the @code{-list-features} command, the
31642 features depend on which target GDB is using at the moment. Whenever
31643 a target can change, due to commands such as @code{-target-select},
31644 @code{-target-attach} or @code{-exec-run}, the list of target features
31645 may change, and the frontend should obtain it again.
31649 (gdb) -list-target-features
31650 ^done,result=["async"]
31653 The current list of features is:
31657 Indicates that the target is capable of asynchronous command
31658 execution, which means that @value{GDBN} will accept further commands
31659 while the target is running.
31662 Indicates that the target is capable of reverse execution.
31663 @xref{Reverse Execution}, for more information.
31667 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31668 @node GDB/MI Miscellaneous Commands
31669 @section Miscellaneous @sc{gdb/mi} Commands
31671 @c @subheading -gdb-complete
31673 @subheading The @code{-gdb-exit} Command
31676 @subsubheading Synopsis
31682 Exit @value{GDBN} immediately.
31684 @subsubheading @value{GDBN} Command
31686 Approximately corresponds to @samp{quit}.
31688 @subsubheading Example
31698 @subheading The @code{-exec-abort} Command
31699 @findex -exec-abort
31701 @subsubheading Synopsis
31707 Kill the inferior running program.
31709 @subsubheading @value{GDBN} Command
31711 The corresponding @value{GDBN} command is @samp{kill}.
31713 @subsubheading Example
31718 @subheading The @code{-gdb-set} Command
31721 @subsubheading Synopsis
31727 Set an internal @value{GDBN} variable.
31728 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31730 @subsubheading @value{GDBN} Command
31732 The corresponding @value{GDBN} command is @samp{set}.
31734 @subsubheading Example
31744 @subheading The @code{-gdb-show} Command
31747 @subsubheading Synopsis
31753 Show the current value of a @value{GDBN} variable.
31755 @subsubheading @value{GDBN} Command
31757 The corresponding @value{GDBN} command is @samp{show}.
31759 @subsubheading Example
31768 @c @subheading -gdb-source
31771 @subheading The @code{-gdb-version} Command
31772 @findex -gdb-version
31774 @subsubheading Synopsis
31780 Show version information for @value{GDBN}. Used mostly in testing.
31782 @subsubheading @value{GDBN} Command
31784 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31785 default shows this information when you start an interactive session.
31787 @subsubheading Example
31789 @c This example modifies the actual output from GDB to avoid overfull
31795 ~Copyright 2000 Free Software Foundation, Inc.
31796 ~GDB is free software, covered by the GNU General Public License, and
31797 ~you are welcome to change it and/or distribute copies of it under
31798 ~ certain conditions.
31799 ~Type "show copying" to see the conditions.
31800 ~There is absolutely no warranty for GDB. Type "show warranty" for
31802 ~This GDB was configured as
31803 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31808 @subheading The @code{-list-thread-groups} Command
31809 @findex -list-thread-groups
31811 @subheading Synopsis
31814 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31817 Lists thread groups (@pxref{Thread groups}). When a single thread
31818 group is passed as the argument, lists the children of that group.
31819 When several thread group are passed, lists information about those
31820 thread groups. Without any parameters, lists information about all
31821 top-level thread groups.
31823 Normally, thread groups that are being debugged are reported.
31824 With the @samp{--available} option, @value{GDBN} reports thread groups
31825 available on the target.
31827 The output of this command may have either a @samp{threads} result or
31828 a @samp{groups} result. The @samp{thread} result has a list of tuples
31829 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31830 Information}). The @samp{groups} result has a list of tuples as value,
31831 each tuple describing a thread group. If top-level groups are
31832 requested (that is, no parameter is passed), or when several groups
31833 are passed, the output always has a @samp{groups} result. The format
31834 of the @samp{group} result is described below.
31836 To reduce the number of roundtrips it's possible to list thread groups
31837 together with their children, by passing the @samp{--recurse} option
31838 and the recursion depth. Presently, only recursion depth of 1 is
31839 permitted. If this option is present, then every reported thread group
31840 will also include its children, either as @samp{group} or
31841 @samp{threads} field.
31843 In general, any combination of option and parameters is permitted, with
31844 the following caveats:
31848 When a single thread group is passed, the output will typically
31849 be the @samp{threads} result. Because threads may not contain
31850 anything, the @samp{recurse} option will be ignored.
31853 When the @samp{--available} option is passed, limited information may
31854 be available. In particular, the list of threads of a process might
31855 be inaccessible. Further, specifying specific thread groups might
31856 not give any performance advantage over listing all thread groups.
31857 The frontend should assume that @samp{-list-thread-groups --available}
31858 is always an expensive operation and cache the results.
31862 The @samp{groups} result is a list of tuples, where each tuple may
31863 have the following fields:
31867 Identifier of the thread group. This field is always present.
31868 The identifier is an opaque string; frontends should not try to
31869 convert it to an integer, even though it might look like one.
31872 The type of the thread group. At present, only @samp{process} is a
31876 The target-specific process identifier. This field is only present
31877 for thread groups of type @samp{process} and only if the process exists.
31880 The exit code of this group's last exited thread, formatted in octal.
31881 This field is only present for thread groups of type @samp{process} and
31882 only if the process is not running.
31885 The number of children this thread group has. This field may be
31886 absent for an available thread group.
31889 This field has a list of tuples as value, each tuple describing a
31890 thread. It may be present if the @samp{--recurse} option is
31891 specified, and it's actually possible to obtain the threads.
31894 This field is a list of integers, each identifying a core that one
31895 thread of the group is running on. This field may be absent if
31896 such information is not available.
31899 The name of the executable file that corresponds to this thread group.
31900 The field is only present for thread groups of type @samp{process},
31901 and only if there is a corresponding executable file.
31905 @subheading Example
31909 -list-thread-groups
31910 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31911 -list-thread-groups 17
31912 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31913 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31914 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31915 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31916 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31917 -list-thread-groups --available
31918 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31919 -list-thread-groups --available --recurse 1
31920 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31921 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31922 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31923 -list-thread-groups --available --recurse 1 17 18
31924 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31925 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31926 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31929 @subheading The @code{-info-os} Command
31932 @subsubheading Synopsis
31935 -info-os [ @var{type} ]
31938 If no argument is supplied, the command returns a table of available
31939 operating-system-specific information types. If one of these types is
31940 supplied as an argument @var{type}, then the command returns a table
31941 of data of that type.
31943 The types of information available depend on the target operating
31946 @subsubheading @value{GDBN} Command
31948 The corresponding @value{GDBN} command is @samp{info os}.
31950 @subsubheading Example
31952 When run on a @sc{gnu}/Linux system, the output will look something
31958 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
31959 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31960 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31961 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31962 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
31964 item=@{col0="files",col1="Listing of all file descriptors",
31965 col2="File descriptors"@},
31966 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31967 col2="Kernel modules"@},
31968 item=@{col0="msg",col1="Listing of all message queues",
31969 col2="Message queues"@},
31970 item=@{col0="processes",col1="Listing of all processes",
31971 col2="Processes"@},
31972 item=@{col0="procgroups",col1="Listing of all process groups",
31973 col2="Process groups"@},
31974 item=@{col0="semaphores",col1="Listing of all semaphores",
31975 col2="Semaphores"@},
31976 item=@{col0="shm",col1="Listing of all shared-memory regions",
31977 col2="Shared-memory regions"@},
31978 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
31980 item=@{col0="threads",col1="Listing of all threads",
31984 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
31985 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
31986 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
31987 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
31988 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
31989 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
31990 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
31991 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
31993 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
31994 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
31998 (Note that the MI output here includes a @code{"Title"} column that
31999 does not appear in command-line @code{info os}; this column is useful
32000 for MI clients that want to enumerate the types of data, such as in a
32001 popup menu, but is needless clutter on the command line, and
32002 @code{info os} omits it.)
32004 @subheading The @code{-add-inferior} Command
32005 @findex -add-inferior
32007 @subheading Synopsis
32013 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32014 inferior is not associated with any executable. Such association may
32015 be established with the @samp{-file-exec-and-symbols} command
32016 (@pxref{GDB/MI File Commands}). The command response has a single
32017 field, @samp{inferior}, whose value is the identifier of the
32018 thread group corresponding to the new inferior.
32020 @subheading Example
32025 ^done,inferior="i3"
32028 @subheading The @code{-interpreter-exec} Command
32029 @findex -interpreter-exec
32031 @subheading Synopsis
32034 -interpreter-exec @var{interpreter} @var{command}
32036 @anchor{-interpreter-exec}
32038 Execute the specified @var{command} in the given @var{interpreter}.
32040 @subheading @value{GDBN} Command
32042 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32044 @subheading Example
32048 -interpreter-exec console "break main"
32049 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32050 &"During symbol reading, bad structure-type format.\n"
32051 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32056 @subheading The @code{-inferior-tty-set} Command
32057 @findex -inferior-tty-set
32059 @subheading Synopsis
32062 -inferior-tty-set /dev/pts/1
32065 Set terminal for future runs of the program being debugged.
32067 @subheading @value{GDBN} Command
32069 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32071 @subheading Example
32075 -inferior-tty-set /dev/pts/1
32080 @subheading The @code{-inferior-tty-show} Command
32081 @findex -inferior-tty-show
32083 @subheading Synopsis
32089 Show terminal for future runs of program being debugged.
32091 @subheading @value{GDBN} Command
32093 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32095 @subheading Example
32099 -inferior-tty-set /dev/pts/1
32103 ^done,inferior_tty_terminal="/dev/pts/1"
32107 @subheading The @code{-enable-timings} Command
32108 @findex -enable-timings
32110 @subheading Synopsis
32113 -enable-timings [yes | no]
32116 Toggle the printing of the wallclock, user and system times for an MI
32117 command as a field in its output. This command is to help frontend
32118 developers optimize the performance of their code. No argument is
32119 equivalent to @samp{yes}.
32121 @subheading @value{GDBN} Command
32125 @subheading Example
32133 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32134 addr="0x080484ed",func="main",file="myprog.c",
32135 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32137 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32145 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32146 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32147 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32148 fullname="/home/nickrob/myprog.c",line="73"@}
32153 @chapter @value{GDBN} Annotations
32155 This chapter describes annotations in @value{GDBN}. Annotations were
32156 designed to interface @value{GDBN} to graphical user interfaces or other
32157 similar programs which want to interact with @value{GDBN} at a
32158 relatively high level.
32160 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32164 This is Edition @value{EDITION}, @value{DATE}.
32168 * Annotations Overview:: What annotations are; the general syntax.
32169 * Server Prefix:: Issuing a command without affecting user state.
32170 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32171 * Errors:: Annotations for error messages.
32172 * Invalidation:: Some annotations describe things now invalid.
32173 * Annotations for Running::
32174 Whether the program is running, how it stopped, etc.
32175 * Source Annotations:: Annotations describing source code.
32178 @node Annotations Overview
32179 @section What is an Annotation?
32180 @cindex annotations
32182 Annotations start with a newline character, two @samp{control-z}
32183 characters, and the name of the annotation. If there is no additional
32184 information associated with this annotation, the name of the annotation
32185 is followed immediately by a newline. If there is additional
32186 information, the name of the annotation is followed by a space, the
32187 additional information, and a newline. The additional information
32188 cannot contain newline characters.
32190 Any output not beginning with a newline and two @samp{control-z}
32191 characters denotes literal output from @value{GDBN}. Currently there is
32192 no need for @value{GDBN} to output a newline followed by two
32193 @samp{control-z} characters, but if there was such a need, the
32194 annotations could be extended with an @samp{escape} annotation which
32195 means those three characters as output.
32197 The annotation @var{level}, which is specified using the
32198 @option{--annotate} command line option (@pxref{Mode Options}), controls
32199 how much information @value{GDBN} prints together with its prompt,
32200 values of expressions, source lines, and other types of output. Level 0
32201 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32202 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32203 for programs that control @value{GDBN}, and level 2 annotations have
32204 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32205 Interface, annotate, GDB's Obsolete Annotations}).
32208 @kindex set annotate
32209 @item set annotate @var{level}
32210 The @value{GDBN} command @code{set annotate} sets the level of
32211 annotations to the specified @var{level}.
32213 @item show annotate
32214 @kindex show annotate
32215 Show the current annotation level.
32218 This chapter describes level 3 annotations.
32220 A simple example of starting up @value{GDBN} with annotations is:
32223 $ @kbd{gdb --annotate=3}
32225 Copyright 2003 Free Software Foundation, Inc.
32226 GDB is free software, covered by the GNU General Public License,
32227 and you are welcome to change it and/or distribute copies of it
32228 under certain conditions.
32229 Type "show copying" to see the conditions.
32230 There is absolutely no warranty for GDB. Type "show warranty"
32232 This GDB was configured as "i386-pc-linux-gnu"
32243 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32244 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32245 denotes a @samp{control-z} character) are annotations; the rest is
32246 output from @value{GDBN}.
32248 @node Server Prefix
32249 @section The Server Prefix
32250 @cindex server prefix
32252 If you prefix a command with @samp{server } then it will not affect
32253 the command history, nor will it affect @value{GDBN}'s notion of which
32254 command to repeat if @key{RET} is pressed on a line by itself. This
32255 means that commands can be run behind a user's back by a front-end in
32256 a transparent manner.
32258 The @code{server } prefix does not affect the recording of values into
32259 the value history; to print a value without recording it into the
32260 value history, use the @code{output} command instead of the
32261 @code{print} command.
32263 Using this prefix also disables confirmation requests
32264 (@pxref{confirmation requests}).
32267 @section Annotation for @value{GDBN} Input
32269 @cindex annotations for prompts
32270 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32271 to know when to send output, when the output from a given command is
32274 Different kinds of input each have a different @dfn{input type}. Each
32275 input type has three annotations: a @code{pre-} annotation, which
32276 denotes the beginning of any prompt which is being output, a plain
32277 annotation, which denotes the end of the prompt, and then a @code{post-}
32278 annotation which denotes the end of any echo which may (or may not) be
32279 associated with the input. For example, the @code{prompt} input type
32280 features the following annotations:
32288 The input types are
32291 @findex pre-prompt annotation
32292 @findex prompt annotation
32293 @findex post-prompt annotation
32295 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32297 @findex pre-commands annotation
32298 @findex commands annotation
32299 @findex post-commands annotation
32301 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32302 command. The annotations are repeated for each command which is input.
32304 @findex pre-overload-choice annotation
32305 @findex overload-choice annotation
32306 @findex post-overload-choice annotation
32307 @item overload-choice
32308 When @value{GDBN} wants the user to select between various overloaded functions.
32310 @findex pre-query annotation
32311 @findex query annotation
32312 @findex post-query annotation
32314 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32316 @findex pre-prompt-for-continue annotation
32317 @findex prompt-for-continue annotation
32318 @findex post-prompt-for-continue annotation
32319 @item prompt-for-continue
32320 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32321 expect this to work well; instead use @code{set height 0} to disable
32322 prompting. This is because the counting of lines is buggy in the
32323 presence of annotations.
32328 @cindex annotations for errors, warnings and interrupts
32330 @findex quit annotation
32335 This annotation occurs right before @value{GDBN} responds to an interrupt.
32337 @findex error annotation
32342 This annotation occurs right before @value{GDBN} responds to an error.
32344 Quit and error annotations indicate that any annotations which @value{GDBN} was
32345 in the middle of may end abruptly. For example, if a
32346 @code{value-history-begin} annotation is followed by a @code{error}, one
32347 cannot expect to receive the matching @code{value-history-end}. One
32348 cannot expect not to receive it either, however; an error annotation
32349 does not necessarily mean that @value{GDBN} is immediately returning all the way
32352 @findex error-begin annotation
32353 A quit or error annotation may be preceded by
32359 Any output between that and the quit or error annotation is the error
32362 Warning messages are not yet annotated.
32363 @c If we want to change that, need to fix warning(), type_error(),
32364 @c range_error(), and possibly other places.
32367 @section Invalidation Notices
32369 @cindex annotations for invalidation messages
32370 The following annotations say that certain pieces of state may have
32374 @findex frames-invalid annotation
32375 @item ^Z^Zframes-invalid
32377 The frames (for example, output from the @code{backtrace} command) may
32380 @findex breakpoints-invalid annotation
32381 @item ^Z^Zbreakpoints-invalid
32383 The breakpoints may have changed. For example, the user just added or
32384 deleted a breakpoint.
32387 @node Annotations for Running
32388 @section Running the Program
32389 @cindex annotations for running programs
32391 @findex starting annotation
32392 @findex stopping annotation
32393 When the program starts executing due to a @value{GDBN} command such as
32394 @code{step} or @code{continue},
32400 is output. When the program stops,
32406 is output. Before the @code{stopped} annotation, a variety of
32407 annotations describe how the program stopped.
32410 @findex exited annotation
32411 @item ^Z^Zexited @var{exit-status}
32412 The program exited, and @var{exit-status} is the exit status (zero for
32413 successful exit, otherwise nonzero).
32415 @findex signalled annotation
32416 @findex signal-name annotation
32417 @findex signal-name-end annotation
32418 @findex signal-string annotation
32419 @findex signal-string-end annotation
32420 @item ^Z^Zsignalled
32421 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32422 annotation continues:
32428 ^Z^Zsignal-name-end
32432 ^Z^Zsignal-string-end
32437 where @var{name} is the name of the signal, such as @code{SIGILL} or
32438 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32439 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32440 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32441 user's benefit and have no particular format.
32443 @findex signal annotation
32445 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32446 just saying that the program received the signal, not that it was
32447 terminated with it.
32449 @findex breakpoint annotation
32450 @item ^Z^Zbreakpoint @var{number}
32451 The program hit breakpoint number @var{number}.
32453 @findex watchpoint annotation
32454 @item ^Z^Zwatchpoint @var{number}
32455 The program hit watchpoint number @var{number}.
32458 @node Source Annotations
32459 @section Displaying Source
32460 @cindex annotations for source display
32462 @findex source annotation
32463 The following annotation is used instead of displaying source code:
32466 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32469 where @var{filename} is an absolute file name indicating which source
32470 file, @var{line} is the line number within that file (where 1 is the
32471 first line in the file), @var{character} is the character position
32472 within the file (where 0 is the first character in the file) (for most
32473 debug formats this will necessarily point to the beginning of a line),
32474 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32475 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32476 @var{addr} is the address in the target program associated with the
32477 source which is being displayed. The @var{addr} is in the form @samp{0x}
32478 followed by one or more lowercase hex digits (note that this does not
32479 depend on the language).
32481 @node JIT Interface
32482 @chapter JIT Compilation Interface
32483 @cindex just-in-time compilation
32484 @cindex JIT compilation interface
32486 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32487 interface. A JIT compiler is a program or library that generates native
32488 executable code at runtime and executes it, usually in order to achieve good
32489 performance while maintaining platform independence.
32491 Programs that use JIT compilation are normally difficult to debug because
32492 portions of their code are generated at runtime, instead of being loaded from
32493 object files, which is where @value{GDBN} normally finds the program's symbols
32494 and debug information. In order to debug programs that use JIT compilation,
32495 @value{GDBN} has an interface that allows the program to register in-memory
32496 symbol files with @value{GDBN} at runtime.
32498 If you are using @value{GDBN} to debug a program that uses this interface, then
32499 it should work transparently so long as you have not stripped the binary. If
32500 you are developing a JIT compiler, then the interface is documented in the rest
32501 of this chapter. At this time, the only known client of this interface is the
32504 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32505 JIT compiler communicates with @value{GDBN} by writing data into a global
32506 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32507 attaches, it reads a linked list of symbol files from the global variable to
32508 find existing code, and puts a breakpoint in the function so that it can find
32509 out about additional code.
32512 * Declarations:: Relevant C struct declarations
32513 * Registering Code:: Steps to register code
32514 * Unregistering Code:: Steps to unregister code
32515 * Custom Debug Info:: Emit debug information in a custom format
32519 @section JIT Declarations
32521 These are the relevant struct declarations that a C program should include to
32522 implement the interface:
32532 struct jit_code_entry
32534 struct jit_code_entry *next_entry;
32535 struct jit_code_entry *prev_entry;
32536 const char *symfile_addr;
32537 uint64_t symfile_size;
32540 struct jit_descriptor
32543 /* This type should be jit_actions_t, but we use uint32_t
32544 to be explicit about the bitwidth. */
32545 uint32_t action_flag;
32546 struct jit_code_entry *relevant_entry;
32547 struct jit_code_entry *first_entry;
32550 /* GDB puts a breakpoint in this function. */
32551 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32553 /* Make sure to specify the version statically, because the
32554 debugger may check the version before we can set it. */
32555 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32558 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32559 modifications to this global data properly, which can easily be done by putting
32560 a global mutex around modifications to these structures.
32562 @node Registering Code
32563 @section Registering Code
32565 To register code with @value{GDBN}, the JIT should follow this protocol:
32569 Generate an object file in memory with symbols and other desired debug
32570 information. The file must include the virtual addresses of the sections.
32573 Create a code entry for the file, which gives the start and size of the symbol
32577 Add it to the linked list in the JIT descriptor.
32580 Point the relevant_entry field of the descriptor at the entry.
32583 Set @code{action_flag} to @code{JIT_REGISTER} and call
32584 @code{__jit_debug_register_code}.
32587 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32588 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32589 new code. However, the linked list must still be maintained in order to allow
32590 @value{GDBN} to attach to a running process and still find the symbol files.
32592 @node Unregistering Code
32593 @section Unregistering Code
32595 If code is freed, then the JIT should use the following protocol:
32599 Remove the code entry corresponding to the code from the linked list.
32602 Point the @code{relevant_entry} field of the descriptor at the code entry.
32605 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32606 @code{__jit_debug_register_code}.
32609 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32610 and the JIT will leak the memory used for the associated symbol files.
32612 @node Custom Debug Info
32613 @section Custom Debug Info
32614 @cindex custom JIT debug info
32615 @cindex JIT debug info reader
32617 Generating debug information in platform-native file formats (like ELF
32618 or COFF) may be an overkill for JIT compilers; especially if all the
32619 debug info is used for is displaying a meaningful backtrace. The
32620 issue can be resolved by having the JIT writers decide on a debug info
32621 format and also provide a reader that parses the debug info generated
32622 by the JIT compiler. This section gives a brief overview on writing
32623 such a parser. More specific details can be found in the source file
32624 @file{gdb/jit-reader.in}, which is also installed as a header at
32625 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32627 The reader is implemented as a shared object (so this functionality is
32628 not available on platforms which don't allow loading shared objects at
32629 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32630 @code{jit-reader-unload} are provided, to be used to load and unload
32631 the readers from a preconfigured directory. Once loaded, the shared
32632 object is used the parse the debug information emitted by the JIT
32636 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32637 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32640 @node Using JIT Debug Info Readers
32641 @subsection Using JIT Debug Info Readers
32642 @kindex jit-reader-load
32643 @kindex jit-reader-unload
32645 Readers can be loaded and unloaded using the @code{jit-reader-load}
32646 and @code{jit-reader-unload} commands.
32649 @item jit-reader-load @var{reader}
32650 Load the JIT reader named @var{reader}, which is a shared
32651 object specified as either an absolute or a relative file name. In
32652 the latter case, @value{GDBN} will try to load the reader from a
32653 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32654 system (here @var{libdir} is the system library directory, often
32655 @file{/usr/local/lib}).
32657 Only one reader can be active at a time; trying to load a second
32658 reader when one is already loaded will result in @value{GDBN}
32659 reporting an error. A new JIT reader can be loaded by first unloading
32660 the current one using @code{jit-reader-unload} and then invoking
32661 @code{jit-reader-load}.
32663 @item jit-reader-unload
32664 Unload the currently loaded JIT reader.
32668 @node Writing JIT Debug Info Readers
32669 @subsection Writing JIT Debug Info Readers
32670 @cindex writing JIT debug info readers
32672 As mentioned, a reader is essentially a shared object conforming to a
32673 certain ABI. This ABI is described in @file{jit-reader.h}.
32675 @file{jit-reader.h} defines the structures, macros and functions
32676 required to write a reader. It is installed (along with
32677 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32678 the system include directory.
32680 Readers need to be released under a GPL compatible license. A reader
32681 can be declared as released under such a license by placing the macro
32682 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32684 The entry point for readers is the symbol @code{gdb_init_reader},
32685 which is expected to be a function with the prototype
32687 @findex gdb_init_reader
32689 extern struct gdb_reader_funcs *gdb_init_reader (void);
32692 @cindex @code{struct gdb_reader_funcs}
32694 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32695 functions. These functions are executed to read the debug info
32696 generated by the JIT compiler (@code{read}), to unwind stack frames
32697 (@code{unwind}) and to create canonical frame IDs
32698 (@code{get_Frame_id}). It also has a callback that is called when the
32699 reader is being unloaded (@code{destroy}). The struct looks like this
32702 struct gdb_reader_funcs
32704 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32705 int reader_version;
32707 /* For use by the reader. */
32710 gdb_read_debug_info *read;
32711 gdb_unwind_frame *unwind;
32712 gdb_get_frame_id *get_frame_id;
32713 gdb_destroy_reader *destroy;
32717 @cindex @code{struct gdb_symbol_callbacks}
32718 @cindex @code{struct gdb_unwind_callbacks}
32720 The callbacks are provided with another set of callbacks by
32721 @value{GDBN} to do their job. For @code{read}, these callbacks are
32722 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32723 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32724 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32725 files and new symbol tables inside those object files. @code{struct
32726 gdb_unwind_callbacks} has callbacks to read registers off the current
32727 frame and to write out the values of the registers in the previous
32728 frame. Both have a callback (@code{target_read}) to read bytes off the
32729 target's address space.
32731 @node In-Process Agent
32732 @chapter In-Process Agent
32733 @cindex debugging agent
32734 The traditional debugging model is conceptually low-speed, but works fine,
32735 because most bugs can be reproduced in debugging-mode execution. However,
32736 as multi-core or many-core processors are becoming mainstream, and
32737 multi-threaded programs become more and more popular, there should be more
32738 and more bugs that only manifest themselves at normal-mode execution, for
32739 example, thread races, because debugger's interference with the program's
32740 timing may conceal the bugs. On the other hand, in some applications,
32741 it is not feasible for the debugger to interrupt the program's execution
32742 long enough for the developer to learn anything helpful about its behavior.
32743 If the program's correctness depends on its real-time behavior, delays
32744 introduced by a debugger might cause the program to fail, even when the
32745 code itself is correct. It is useful to be able to observe the program's
32746 behavior without interrupting it.
32748 Therefore, traditional debugging model is too intrusive to reproduce
32749 some bugs. In order to reduce the interference with the program, we can
32750 reduce the number of operations performed by debugger. The
32751 @dfn{In-Process Agent}, a shared library, is running within the same
32752 process with inferior, and is able to perform some debugging operations
32753 itself. As a result, debugger is only involved when necessary, and
32754 performance of debugging can be improved accordingly. Note that
32755 interference with program can be reduced but can't be removed completely,
32756 because the in-process agent will still stop or slow down the program.
32758 The in-process agent can interpret and execute Agent Expressions
32759 (@pxref{Agent Expressions}) during performing debugging operations. The
32760 agent expressions can be used for different purposes, such as collecting
32761 data in tracepoints, and condition evaluation in breakpoints.
32763 @anchor{Control Agent}
32764 You can control whether the in-process agent is used as an aid for
32765 debugging with the following commands:
32768 @kindex set agent on
32770 Causes the in-process agent to perform some operations on behalf of the
32771 debugger. Just which operations requested by the user will be done
32772 by the in-process agent depends on the its capabilities. For example,
32773 if you request to evaluate breakpoint conditions in the in-process agent,
32774 and the in-process agent has such capability as well, then breakpoint
32775 conditions will be evaluated in the in-process agent.
32777 @kindex set agent off
32778 @item set agent off
32779 Disables execution of debugging operations by the in-process agent. All
32780 of the operations will be performed by @value{GDBN}.
32784 Display the current setting of execution of debugging operations by
32785 the in-process agent.
32789 * In-Process Agent Protocol::
32792 @node In-Process Agent Protocol
32793 @section In-Process Agent Protocol
32794 @cindex in-process agent protocol
32796 The in-process agent is able to communicate with both @value{GDBN} and
32797 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32798 used for communications between @value{GDBN} or GDBserver and the IPA.
32799 In general, @value{GDBN} or GDBserver sends commands
32800 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32801 in-process agent replies back with the return result of the command, or
32802 some other information. The data sent to in-process agent is composed
32803 of primitive data types, such as 4-byte or 8-byte type, and composite
32804 types, which are called objects (@pxref{IPA Protocol Objects}).
32807 * IPA Protocol Objects::
32808 * IPA Protocol Commands::
32811 @node IPA Protocol Objects
32812 @subsection IPA Protocol Objects
32813 @cindex ipa protocol objects
32815 The commands sent to and results received from agent may contain some
32816 complex data types called @dfn{objects}.
32818 The in-process agent is running on the same machine with @value{GDBN}
32819 or GDBserver, so it doesn't have to handle as much differences between
32820 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32821 However, there are still some differences of two ends in two processes:
32825 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32826 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32828 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32829 GDBserver is compiled with one, and in-process agent is compiled with
32833 Here are the IPA Protocol Objects:
32837 agent expression object. It represents an agent expression
32838 (@pxref{Agent Expressions}).
32839 @anchor{agent expression object}
32841 tracepoint action object. It represents a tracepoint action
32842 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32843 memory, static trace data and to evaluate expression.
32844 @anchor{tracepoint action object}
32846 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32847 @anchor{tracepoint object}
32851 The following table describes important attributes of each IPA protocol
32854 @multitable @columnfractions .30 .20 .50
32855 @headitem Name @tab Size @tab Description
32856 @item @emph{agent expression object} @tab @tab
32857 @item length @tab 4 @tab length of bytes code
32858 @item byte code @tab @var{length} @tab contents of byte code
32859 @item @emph{tracepoint action for collecting memory} @tab @tab
32860 @item 'M' @tab 1 @tab type of tracepoint action
32861 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32862 address of the lowest byte to collect, otherwise @var{addr} is the offset
32863 of @var{basereg} for memory collecting.
32864 @item len @tab 8 @tab length of memory for collecting
32865 @item basereg @tab 4 @tab the register number containing the starting
32866 memory address for collecting.
32867 @item @emph{tracepoint action for collecting registers} @tab @tab
32868 @item 'R' @tab 1 @tab type of tracepoint action
32869 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32870 @item 'L' @tab 1 @tab type of tracepoint action
32871 @item @emph{tracepoint action for expression evaluation} @tab @tab
32872 @item 'X' @tab 1 @tab type of tracepoint action
32873 @item agent expression @tab length of @tab @ref{agent expression object}
32874 @item @emph{tracepoint object} @tab @tab
32875 @item number @tab 4 @tab number of tracepoint
32876 @item address @tab 8 @tab address of tracepoint inserted on
32877 @item type @tab 4 @tab type of tracepoint
32878 @item enabled @tab 1 @tab enable or disable of tracepoint
32879 @item step_count @tab 8 @tab step
32880 @item pass_count @tab 8 @tab pass
32881 @item numactions @tab 4 @tab number of tracepoint actions
32882 @item hit count @tab 8 @tab hit count
32883 @item trace frame usage @tab 8 @tab trace frame usage
32884 @item compiled_cond @tab 8 @tab compiled condition
32885 @item orig_size @tab 8 @tab orig size
32886 @item condition @tab 4 if condition is NULL otherwise length of
32887 @ref{agent expression object}
32888 @tab zero if condition is NULL, otherwise is
32889 @ref{agent expression object}
32890 @item actions @tab variable
32891 @tab numactions number of @ref{tracepoint action object}
32894 @node IPA Protocol Commands
32895 @subsection IPA Protocol Commands
32896 @cindex ipa protocol commands
32898 The spaces in each command are delimiters to ease reading this commands
32899 specification. They don't exist in real commands.
32903 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32904 Installs a new fast tracepoint described by @var{tracepoint_object}
32905 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
32906 head of @dfn{jumppad}, which is used to jump to data collection routine
32911 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32912 @var{target_address} is address of tracepoint in the inferior.
32913 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32914 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32915 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
32916 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32923 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32924 is about to kill inferiors.
32932 @item probe_marker_at:@var{address}
32933 Asks in-process agent to probe the marker at @var{address}.
32940 @item unprobe_marker_at:@var{address}
32941 Asks in-process agent to unprobe the marker at @var{address}.
32945 @chapter Reporting Bugs in @value{GDBN}
32946 @cindex bugs in @value{GDBN}
32947 @cindex reporting bugs in @value{GDBN}
32949 Your bug reports play an essential role in making @value{GDBN} reliable.
32951 Reporting a bug may help you by bringing a solution to your problem, or it
32952 may not. But in any case the principal function of a bug report is to help
32953 the entire community by making the next version of @value{GDBN} work better. Bug
32954 reports are your contribution to the maintenance of @value{GDBN}.
32956 In order for a bug report to serve its purpose, you must include the
32957 information that enables us to fix the bug.
32960 * Bug Criteria:: Have you found a bug?
32961 * Bug Reporting:: How to report bugs
32965 @section Have You Found a Bug?
32966 @cindex bug criteria
32968 If you are not sure whether you have found a bug, here are some guidelines:
32971 @cindex fatal signal
32972 @cindex debugger crash
32973 @cindex crash of debugger
32975 If the debugger gets a fatal signal, for any input whatever, that is a
32976 @value{GDBN} bug. Reliable debuggers never crash.
32978 @cindex error on valid input
32980 If @value{GDBN} produces an error message for valid input, that is a
32981 bug. (Note that if you're cross debugging, the problem may also be
32982 somewhere in the connection to the target.)
32984 @cindex invalid input
32986 If @value{GDBN} does not produce an error message for invalid input,
32987 that is a bug. However, you should note that your idea of
32988 ``invalid input'' might be our idea of ``an extension'' or ``support
32989 for traditional practice''.
32992 If you are an experienced user of debugging tools, your suggestions
32993 for improvement of @value{GDBN} are welcome in any case.
32996 @node Bug Reporting
32997 @section How to Report Bugs
32998 @cindex bug reports
32999 @cindex @value{GDBN} bugs, reporting
33001 A number of companies and individuals offer support for @sc{gnu} products.
33002 If you obtained @value{GDBN} from a support organization, we recommend you
33003 contact that organization first.
33005 You can find contact information for many support companies and
33006 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33008 @c should add a web page ref...
33011 @ifset BUGURL_DEFAULT
33012 In any event, we also recommend that you submit bug reports for
33013 @value{GDBN}. The preferred method is to submit them directly using
33014 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33015 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33018 @strong{Do not send bug reports to @samp{info-gdb}, or to
33019 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33020 not want to receive bug reports. Those that do have arranged to receive
33023 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33024 serves as a repeater. The mailing list and the newsgroup carry exactly
33025 the same messages. Often people think of posting bug reports to the
33026 newsgroup instead of mailing them. This appears to work, but it has one
33027 problem which can be crucial: a newsgroup posting often lacks a mail
33028 path back to the sender. Thus, if we need to ask for more information,
33029 we may be unable to reach you. For this reason, it is better to send
33030 bug reports to the mailing list.
33032 @ifclear BUGURL_DEFAULT
33033 In any event, we also recommend that you submit bug reports for
33034 @value{GDBN} to @value{BUGURL}.
33038 The fundamental principle of reporting bugs usefully is this:
33039 @strong{report all the facts}. If you are not sure whether to state a
33040 fact or leave it out, state it!
33042 Often people omit facts because they think they know what causes the
33043 problem and assume that some details do not matter. Thus, you might
33044 assume that the name of the variable you use in an example does not matter.
33045 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33046 stray memory reference which happens to fetch from the location where that
33047 name is stored in memory; perhaps, if the name were different, the contents
33048 of that location would fool the debugger into doing the right thing despite
33049 the bug. Play it safe and give a specific, complete example. That is the
33050 easiest thing for you to do, and the most helpful.
33052 Keep in mind that the purpose of a bug report is to enable us to fix the
33053 bug. It may be that the bug has been reported previously, but neither
33054 you nor we can know that unless your bug report is complete and
33057 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33058 bell?'' Those bug reports are useless, and we urge everyone to
33059 @emph{refuse to respond to them} except to chide the sender to report
33062 To enable us to fix the bug, you should include all these things:
33066 The version of @value{GDBN}. @value{GDBN} announces it if you start
33067 with no arguments; you can also print it at any time using @code{show
33070 Without this, we will not know whether there is any point in looking for
33071 the bug in the current version of @value{GDBN}.
33074 The type of machine you are using, and the operating system name and
33078 The details of the @value{GDBN} build-time configuration.
33079 @value{GDBN} shows these details if you invoke it with the
33080 @option{--configuration} command-line option, or if you type
33081 @code{show configuration} at @value{GDBN}'s prompt.
33084 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33085 ``@value{GCC}--2.8.1''.
33088 What compiler (and its version) was used to compile the program you are
33089 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33090 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33091 to get this information; for other compilers, see the documentation for
33095 The command arguments you gave the compiler to compile your example and
33096 observe the bug. For example, did you use @samp{-O}? To guarantee
33097 you will not omit something important, list them all. A copy of the
33098 Makefile (or the output from make) is sufficient.
33100 If we were to try to guess the arguments, we would probably guess wrong
33101 and then we might not encounter the bug.
33104 A complete input script, and all necessary source files, that will
33108 A description of what behavior you observe that you believe is
33109 incorrect. For example, ``It gets a fatal signal.''
33111 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33112 will certainly notice it. But if the bug is incorrect output, we might
33113 not notice unless it is glaringly wrong. You might as well not give us
33114 a chance to make a mistake.
33116 Even if the problem you experience is a fatal signal, you should still
33117 say so explicitly. Suppose something strange is going on, such as, your
33118 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33119 the C library on your system. (This has happened!) Your copy might
33120 crash and ours would not. If you told us to expect a crash, then when
33121 ours fails to crash, we would know that the bug was not happening for
33122 us. If you had not told us to expect a crash, then we would not be able
33123 to draw any conclusion from our observations.
33126 @cindex recording a session script
33127 To collect all this information, you can use a session recording program
33128 such as @command{script}, which is available on many Unix systems.
33129 Just run your @value{GDBN} session inside @command{script} and then
33130 include the @file{typescript} file with your bug report.
33132 Another way to record a @value{GDBN} session is to run @value{GDBN}
33133 inside Emacs and then save the entire buffer to a file.
33136 If you wish to suggest changes to the @value{GDBN} source, send us context
33137 diffs. If you even discuss something in the @value{GDBN} source, refer to
33138 it by context, not by line number.
33140 The line numbers in our development sources will not match those in your
33141 sources. Your line numbers would convey no useful information to us.
33145 Here are some things that are not necessary:
33149 A description of the envelope of the bug.
33151 Often people who encounter a bug spend a lot of time investigating
33152 which changes to the input file will make the bug go away and which
33153 changes will not affect it.
33155 This is often time consuming and not very useful, because the way we
33156 will find the bug is by running a single example under the debugger
33157 with breakpoints, not by pure deduction from a series of examples.
33158 We recommend that you save your time for something else.
33160 Of course, if you can find a simpler example to report @emph{instead}
33161 of the original one, that is a convenience for us. Errors in the
33162 output will be easier to spot, running under the debugger will take
33163 less time, and so on.
33165 However, simplification is not vital; if you do not want to do this,
33166 report the bug anyway and send us the entire test case you used.
33169 A patch for the bug.
33171 A patch for the bug does help us if it is a good one. But do not omit
33172 the necessary information, such as the test case, on the assumption that
33173 a patch is all we need. We might see problems with your patch and decide
33174 to fix the problem another way, or we might not understand it at all.
33176 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33177 construct an example that will make the program follow a certain path
33178 through the code. If you do not send us the example, we will not be able
33179 to construct one, so we will not be able to verify that the bug is fixed.
33181 And if we cannot understand what bug you are trying to fix, or why your
33182 patch should be an improvement, we will not install it. A test case will
33183 help us to understand.
33186 A guess about what the bug is or what it depends on.
33188 Such guesses are usually wrong. Even we cannot guess right about such
33189 things without first using the debugger to find the facts.
33192 @c The readline documentation is distributed with the readline code
33193 @c and consists of the two following files:
33196 @c Use -I with makeinfo to point to the appropriate directory,
33197 @c environment var TEXINPUTS with TeX.
33198 @ifclear SYSTEM_READLINE
33199 @include rluser.texi
33200 @include hsuser.texi
33204 @appendix In Memoriam
33206 The @value{GDBN} project mourns the loss of the following long-time
33211 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33212 to Free Software in general. Outside of @value{GDBN}, he was known in
33213 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33215 @item Michael Snyder
33216 Michael was one of the Global Maintainers of the @value{GDBN} project,
33217 with contributions recorded as early as 1996, until 2011. In addition
33218 to his day to day participation, he was a large driving force behind
33219 adding Reverse Debugging to @value{GDBN}.
33222 Beyond their technical contributions to the project, they were also
33223 enjoyable members of the Free Software Community. We will miss them.
33225 @node Formatting Documentation
33226 @appendix Formatting Documentation
33228 @cindex @value{GDBN} reference card
33229 @cindex reference card
33230 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33231 for printing with PostScript or Ghostscript, in the @file{gdb}
33232 subdirectory of the main source directory@footnote{In
33233 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33234 release.}. If you can use PostScript or Ghostscript with your printer,
33235 you can print the reference card immediately with @file{refcard.ps}.
33237 The release also includes the source for the reference card. You
33238 can format it, using @TeX{}, by typing:
33244 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33245 mode on US ``letter'' size paper;
33246 that is, on a sheet 11 inches wide by 8.5 inches
33247 high. You will need to specify this form of printing as an option to
33248 your @sc{dvi} output program.
33250 @cindex documentation
33252 All the documentation for @value{GDBN} comes as part of the machine-readable
33253 distribution. The documentation is written in Texinfo format, which is
33254 a documentation system that uses a single source file to produce both
33255 on-line information and a printed manual. You can use one of the Info
33256 formatting commands to create the on-line version of the documentation
33257 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33259 @value{GDBN} includes an already formatted copy of the on-line Info
33260 version of this manual in the @file{gdb} subdirectory. The main Info
33261 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33262 subordinate files matching @samp{gdb.info*} in the same directory. If
33263 necessary, you can print out these files, or read them with any editor;
33264 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33265 Emacs or the standalone @code{info} program, available as part of the
33266 @sc{gnu} Texinfo distribution.
33268 If you want to format these Info files yourself, you need one of the
33269 Info formatting programs, such as @code{texinfo-format-buffer} or
33272 If you have @code{makeinfo} installed, and are in the top level
33273 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33274 version @value{GDBVN}), you can make the Info file by typing:
33281 If you want to typeset and print copies of this manual, you need @TeX{},
33282 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33283 Texinfo definitions file.
33285 @TeX{} is a typesetting program; it does not print files directly, but
33286 produces output files called @sc{dvi} files. To print a typeset
33287 document, you need a program to print @sc{dvi} files. If your system
33288 has @TeX{} installed, chances are it has such a program. The precise
33289 command to use depends on your system; @kbd{lpr -d} is common; another
33290 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33291 require a file name without any extension or a @samp{.dvi} extension.
33293 @TeX{} also requires a macro definitions file called
33294 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33295 written in Texinfo format. On its own, @TeX{} cannot either read or
33296 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33297 and is located in the @file{gdb-@var{version-number}/texinfo}
33300 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33301 typeset and print this manual. First switch to the @file{gdb}
33302 subdirectory of the main source directory (for example, to
33303 @file{gdb-@value{GDBVN}/gdb}) and type:
33309 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33311 @node Installing GDB
33312 @appendix Installing @value{GDBN}
33313 @cindex installation
33316 * Requirements:: Requirements for building @value{GDBN}
33317 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33318 * Separate Objdir:: Compiling @value{GDBN} in another directory
33319 * Config Names:: Specifying names for hosts and targets
33320 * Configure Options:: Summary of options for configure
33321 * System-wide configuration:: Having a system-wide init file
33325 @section Requirements for Building @value{GDBN}
33326 @cindex building @value{GDBN}, requirements for
33328 Building @value{GDBN} requires various tools and packages to be available.
33329 Other packages will be used only if they are found.
33331 @heading Tools/Packages Necessary for Building @value{GDBN}
33333 @item ISO C90 compiler
33334 @value{GDBN} is written in ISO C90. It should be buildable with any
33335 working C90 compiler, e.g.@: GCC.
33339 @heading Tools/Packages Optional for Building @value{GDBN}
33343 @value{GDBN} can use the Expat XML parsing library. This library may be
33344 included with your operating system distribution; if it is not, you
33345 can get the latest version from @url{http://expat.sourceforge.net}.
33346 The @file{configure} script will search for this library in several
33347 standard locations; if it is installed in an unusual path, you can
33348 use the @option{--with-libexpat-prefix} option to specify its location.
33354 Remote protocol memory maps (@pxref{Memory Map Format})
33356 Target descriptions (@pxref{Target Descriptions})
33358 Remote shared library lists (@xref{Library List Format},
33359 or alternatively @pxref{Library List Format for SVR4 Targets})
33361 MS-Windows shared libraries (@pxref{Shared Libraries})
33363 Traceframe info (@pxref{Traceframe Info Format})
33365 Branch trace (@pxref{Branch Trace Format},
33366 @pxref{Branch Trace Configuration Format})
33370 @cindex compressed debug sections
33371 @value{GDBN} will use the @samp{zlib} library, if available, to read
33372 compressed debug sections. Some linkers, such as GNU gold, are capable
33373 of producing binaries with compressed debug sections. If @value{GDBN}
33374 is compiled with @samp{zlib}, it will be able to read the debug
33375 information in such binaries.
33377 The @samp{zlib} library is likely included with your operating system
33378 distribution; if it is not, you can get the latest version from
33379 @url{http://zlib.net}.
33382 @value{GDBN}'s features related to character sets (@pxref{Character
33383 Sets}) require a functioning @code{iconv} implementation. If you are
33384 on a GNU system, then this is provided by the GNU C Library. Some
33385 other systems also provide a working @code{iconv}.
33387 If @value{GDBN} is using the @code{iconv} program which is installed
33388 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33389 This is done with @option{--with-iconv-bin} which specifies the
33390 directory that contains the @code{iconv} program.
33392 On systems without @code{iconv}, you can install GNU Libiconv. If you
33393 have previously installed Libiconv, you can use the
33394 @option{--with-libiconv-prefix} option to configure.
33396 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33397 arrange to build Libiconv if a directory named @file{libiconv} appears
33398 in the top-most source directory. If Libiconv is built this way, and
33399 if the operating system does not provide a suitable @code{iconv}
33400 implementation, then the just-built library will automatically be used
33401 by @value{GDBN}. One easy way to set this up is to download GNU
33402 Libiconv, unpack it, and then rename the directory holding the
33403 Libiconv source code to @samp{libiconv}.
33406 @node Running Configure
33407 @section Invoking the @value{GDBN} @file{configure} Script
33408 @cindex configuring @value{GDBN}
33409 @value{GDBN} comes with a @file{configure} script that automates the process
33410 of preparing @value{GDBN} for installation; you can then use @code{make} to
33411 build the @code{gdb} program.
33413 @c irrelevant in info file; it's as current as the code it lives with.
33414 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33415 look at the @file{README} file in the sources; we may have improved the
33416 installation procedures since publishing this manual.}
33419 The @value{GDBN} distribution includes all the source code you need for
33420 @value{GDBN} in a single directory, whose name is usually composed by
33421 appending the version number to @samp{gdb}.
33423 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33424 @file{gdb-@value{GDBVN}} directory. That directory contains:
33427 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33428 script for configuring @value{GDBN} and all its supporting libraries
33430 @item gdb-@value{GDBVN}/gdb
33431 the source specific to @value{GDBN} itself
33433 @item gdb-@value{GDBVN}/bfd
33434 source for the Binary File Descriptor library
33436 @item gdb-@value{GDBVN}/include
33437 @sc{gnu} include files
33439 @item gdb-@value{GDBVN}/libiberty
33440 source for the @samp{-liberty} free software library
33442 @item gdb-@value{GDBVN}/opcodes
33443 source for the library of opcode tables and disassemblers
33445 @item gdb-@value{GDBVN}/readline
33446 source for the @sc{gnu} command-line interface
33448 @item gdb-@value{GDBVN}/glob
33449 source for the @sc{gnu} filename pattern-matching subroutine
33451 @item gdb-@value{GDBVN}/mmalloc
33452 source for the @sc{gnu} memory-mapped malloc package
33455 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33456 from the @file{gdb-@var{version-number}} source directory, which in
33457 this example is the @file{gdb-@value{GDBVN}} directory.
33459 First switch to the @file{gdb-@var{version-number}} source directory
33460 if you are not already in it; then run @file{configure}. Pass the
33461 identifier for the platform on which @value{GDBN} will run as an
33467 cd gdb-@value{GDBVN}
33468 ./configure @var{host}
33473 where @var{host} is an identifier such as @samp{sun4} or
33474 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33475 (You can often leave off @var{host}; @file{configure} tries to guess the
33476 correct value by examining your system.)
33478 Running @samp{configure @var{host}} and then running @code{make} builds the
33479 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33480 libraries, then @code{gdb} itself. The configured source files, and the
33481 binaries, are left in the corresponding source directories.
33484 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33485 system does not recognize this automatically when you run a different
33486 shell, you may need to run @code{sh} on it explicitly:
33489 sh configure @var{host}
33492 If you run @file{configure} from a directory that contains source
33493 directories for multiple libraries or programs, such as the
33494 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33496 creates configuration files for every directory level underneath (unless
33497 you tell it not to, with the @samp{--norecursion} option).
33499 You should run the @file{configure} script from the top directory in the
33500 source tree, the @file{gdb-@var{version-number}} directory. If you run
33501 @file{configure} from one of the subdirectories, you will configure only
33502 that subdirectory. That is usually not what you want. In particular,
33503 if you run the first @file{configure} from the @file{gdb} subdirectory
33504 of the @file{gdb-@var{version-number}} directory, you will omit the
33505 configuration of @file{bfd}, @file{readline}, and other sibling
33506 directories of the @file{gdb} subdirectory. This leads to build errors
33507 about missing include files such as @file{bfd/bfd.h}.
33509 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33510 However, you should make sure that the shell on your path (named by
33511 the @samp{SHELL} environment variable) is publicly readable. Remember
33512 that @value{GDBN} uses the shell to start your program---some systems refuse to
33513 let @value{GDBN} debug child processes whose programs are not readable.
33515 @node Separate Objdir
33516 @section Compiling @value{GDBN} in Another Directory
33518 If you want to run @value{GDBN} versions for several host or target machines,
33519 you need a different @code{gdb} compiled for each combination of
33520 host and target. @file{configure} is designed to make this easy by
33521 allowing you to generate each configuration in a separate subdirectory,
33522 rather than in the source directory. If your @code{make} program
33523 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33524 @code{make} in each of these directories builds the @code{gdb}
33525 program specified there.
33527 To build @code{gdb} in a separate directory, run @file{configure}
33528 with the @samp{--srcdir} option to specify where to find the source.
33529 (You also need to specify a path to find @file{configure}
33530 itself from your working directory. If the path to @file{configure}
33531 would be the same as the argument to @samp{--srcdir}, you can leave out
33532 the @samp{--srcdir} option; it is assumed.)
33534 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33535 separate directory for a Sun 4 like this:
33539 cd gdb-@value{GDBVN}
33542 ../gdb-@value{GDBVN}/configure sun4
33547 When @file{configure} builds a configuration using a remote source
33548 directory, it creates a tree for the binaries with the same structure
33549 (and using the same names) as the tree under the source directory. In
33550 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33551 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33552 @file{gdb-sun4/gdb}.
33554 Make sure that your path to the @file{configure} script has just one
33555 instance of @file{gdb} in it. If your path to @file{configure} looks
33556 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33557 one subdirectory of @value{GDBN}, not the whole package. This leads to
33558 build errors about missing include files such as @file{bfd/bfd.h}.
33560 One popular reason to build several @value{GDBN} configurations in separate
33561 directories is to configure @value{GDBN} for cross-compiling (where
33562 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33563 programs that run on another machine---the @dfn{target}).
33564 You specify a cross-debugging target by
33565 giving the @samp{--target=@var{target}} option to @file{configure}.
33567 When you run @code{make} to build a program or library, you must run
33568 it in a configured directory---whatever directory you were in when you
33569 called @file{configure} (or one of its subdirectories).
33571 The @code{Makefile} that @file{configure} generates in each source
33572 directory also runs recursively. If you type @code{make} in a source
33573 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33574 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33575 will build all the required libraries, and then build GDB.
33577 When you have multiple hosts or targets configured in separate
33578 directories, you can run @code{make} on them in parallel (for example,
33579 if they are NFS-mounted on each of the hosts); they will not interfere
33583 @section Specifying Names for Hosts and Targets
33585 The specifications used for hosts and targets in the @file{configure}
33586 script are based on a three-part naming scheme, but some short predefined
33587 aliases are also supported. The full naming scheme encodes three pieces
33588 of information in the following pattern:
33591 @var{architecture}-@var{vendor}-@var{os}
33594 For example, you can use the alias @code{sun4} as a @var{host} argument,
33595 or as the value for @var{target} in a @code{--target=@var{target}}
33596 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33598 The @file{configure} script accompanying @value{GDBN} does not provide
33599 any query facility to list all supported host and target names or
33600 aliases. @file{configure} calls the Bourne shell script
33601 @code{config.sub} to map abbreviations to full names; you can read the
33602 script, if you wish, or you can use it to test your guesses on
33603 abbreviations---for example:
33606 % sh config.sub i386-linux
33608 % sh config.sub alpha-linux
33609 alpha-unknown-linux-gnu
33610 % sh config.sub hp9k700
33612 % sh config.sub sun4
33613 sparc-sun-sunos4.1.1
33614 % sh config.sub sun3
33615 m68k-sun-sunos4.1.1
33616 % sh config.sub i986v
33617 Invalid configuration `i986v': machine `i986v' not recognized
33621 @code{config.sub} is also distributed in the @value{GDBN} source
33622 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33624 @node Configure Options
33625 @section @file{configure} Options
33627 Here is a summary of the @file{configure} options and arguments that
33628 are most often useful for building @value{GDBN}. @file{configure} also has
33629 several other options not listed here. @inforef{What Configure
33630 Does,,configure.info}, for a full explanation of @file{configure}.
33633 configure @r{[}--help@r{]}
33634 @r{[}--prefix=@var{dir}@r{]}
33635 @r{[}--exec-prefix=@var{dir}@r{]}
33636 @r{[}--srcdir=@var{dirname}@r{]}
33637 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33638 @r{[}--target=@var{target}@r{]}
33643 You may introduce options with a single @samp{-} rather than
33644 @samp{--} if you prefer; but you may abbreviate option names if you use
33649 Display a quick summary of how to invoke @file{configure}.
33651 @item --prefix=@var{dir}
33652 Configure the source to install programs and files under directory
33655 @item --exec-prefix=@var{dir}
33656 Configure the source to install programs under directory
33659 @c avoid splitting the warning from the explanation:
33661 @item --srcdir=@var{dirname}
33662 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33663 @code{make} that implements the @code{VPATH} feature.}@*
33664 Use this option to make configurations in directories separate from the
33665 @value{GDBN} source directories. Among other things, you can use this to
33666 build (or maintain) several configurations simultaneously, in separate
33667 directories. @file{configure} writes configuration-specific files in
33668 the current directory, but arranges for them to use the source in the
33669 directory @var{dirname}. @file{configure} creates directories under
33670 the working directory in parallel to the source directories below
33673 @item --norecursion
33674 Configure only the directory level where @file{configure} is executed; do not
33675 propagate configuration to subdirectories.
33677 @item --target=@var{target}
33678 Configure @value{GDBN} for cross-debugging programs running on the specified
33679 @var{target}. Without this option, @value{GDBN} is configured to debug
33680 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33682 There is no convenient way to generate a list of all available targets.
33684 @item @var{host} @dots{}
33685 Configure @value{GDBN} to run on the specified @var{host}.
33687 There is no convenient way to generate a list of all available hosts.
33690 There are many other options available as well, but they are generally
33691 needed for special purposes only.
33693 @node System-wide configuration
33694 @section System-wide configuration and settings
33695 @cindex system-wide init file
33697 @value{GDBN} can be configured to have a system-wide init file;
33698 this file will be read and executed at startup (@pxref{Startup, , What
33699 @value{GDBN} does during startup}).
33701 Here is the corresponding configure option:
33704 @item --with-system-gdbinit=@var{file}
33705 Specify that the default location of the system-wide init file is
33709 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33710 it may be subject to relocation. Two possible cases:
33714 If the default location of this init file contains @file{$prefix},
33715 it will be subject to relocation. Suppose that the configure options
33716 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33717 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33718 init file is looked for as @file{$install/etc/gdbinit} instead of
33719 @file{$prefix/etc/gdbinit}.
33722 By contrast, if the default location does not contain the prefix,
33723 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33724 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33725 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33726 wherever @value{GDBN} is installed.
33729 If the configured location of the system-wide init file (as given by the
33730 @option{--with-system-gdbinit} option at configure time) is in the
33731 data-directory (as specified by @option{--with-gdb-datadir} at configure
33732 time) or in one of its subdirectories, then @value{GDBN} will look for the
33733 system-wide init file in the directory specified by the
33734 @option{--data-directory} command-line option.
33735 Note that the system-wide init file is only read once, during @value{GDBN}
33736 initialization. If the data-directory is changed after @value{GDBN} has
33737 started with the @code{set data-directory} command, the file will not be
33741 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33744 @node System-wide Configuration Scripts
33745 @subsection Installed System-wide Configuration Scripts
33746 @cindex system-wide configuration scripts
33748 The @file{system-gdbinit} directory, located inside the data-directory
33749 (as specified by @option{--with-gdb-datadir} at configure time) contains
33750 a number of scripts which can be used as system-wide init files. To
33751 automatically source those scripts at startup, @value{GDBN} should be
33752 configured with @option{--with-system-gdbinit}. Otherwise, any user
33753 should be able to source them by hand as needed.
33755 The following scripts are currently available:
33758 @item @file{elinos.py}
33760 @cindex ELinOS system-wide configuration script
33761 This script is useful when debugging a program on an ELinOS target.
33762 It takes advantage of the environment variables defined in a standard
33763 ELinOS environment in order to determine the location of the system
33764 shared libraries, and then sets the @samp{solib-absolute-prefix}
33765 and @samp{solib-search-path} variables appropriately.
33767 @item @file{wrs-linux.py}
33768 @pindex wrs-linux.py
33769 @cindex Wind River Linux system-wide configuration script
33770 This script is useful when debugging a program on a target running
33771 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33772 the host-side sysroot used by the target system.
33776 @node Maintenance Commands
33777 @appendix Maintenance Commands
33778 @cindex maintenance commands
33779 @cindex internal commands
33781 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33782 includes a number of commands intended for @value{GDBN} developers,
33783 that are not documented elsewhere in this manual. These commands are
33784 provided here for reference. (For commands that turn on debugging
33785 messages, see @ref{Debugging Output}.)
33788 @kindex maint agent
33789 @kindex maint agent-eval
33790 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33791 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33792 Translate the given @var{expression} into remote agent bytecodes.
33793 This command is useful for debugging the Agent Expression mechanism
33794 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33795 expression useful for data collection, such as by tracepoints, while
33796 @samp{maint agent-eval} produces an expression that evaluates directly
33797 to a result. For instance, a collection expression for @code{globa +
33798 globb} will include bytecodes to record four bytes of memory at each
33799 of the addresses of @code{globa} and @code{globb}, while discarding
33800 the result of the addition, while an evaluation expression will do the
33801 addition and return the sum.
33802 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33803 If not, generate remote agent bytecode for current frame PC address.
33805 @kindex maint agent-printf
33806 @item maint agent-printf @var{format},@var{expr},...
33807 Translate the given format string and list of argument expressions
33808 into remote agent bytecodes and display them as a disassembled list.
33809 This command is useful for debugging the agent version of dynamic
33810 printf (@pxref{Dynamic Printf}).
33812 @kindex maint info breakpoints
33813 @item @anchor{maint info breakpoints}maint info breakpoints
33814 Using the same format as @samp{info breakpoints}, display both the
33815 breakpoints you've set explicitly, and those @value{GDBN} is using for
33816 internal purposes. Internal breakpoints are shown with negative
33817 breakpoint numbers. The type column identifies what kind of breakpoint
33822 Normal, explicitly set breakpoint.
33825 Normal, explicitly set watchpoint.
33828 Internal breakpoint, used to handle correctly stepping through
33829 @code{longjmp} calls.
33831 @item longjmp resume
33832 Internal breakpoint at the target of a @code{longjmp}.
33835 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33838 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33841 Shared library events.
33845 @kindex maint info btrace
33846 @item maint info btrace
33847 Pint information about raw branch tracing data.
33849 @kindex maint btrace packet-history
33850 @item maint btrace packet-history
33851 Print the raw branch trace packets that are used to compute the
33852 execution history for the @samp{record btrace} command. Both the
33853 information and the format in which it is printed depend on the btrace
33858 For the BTS recording format, print a list of blocks of sequential
33859 code. For each block, the following information is printed:
33863 Newer blocks have higher numbers. The oldest block has number zero.
33864 @item Lowest @samp{PC}
33865 @item Highest @samp{PC}
33869 For the Intel(R) Processor Trace recording format, print a list of
33870 Intel(R) Processor Trace packets. For each packet, the following
33871 information is printed:
33874 @item Packet number
33875 Newer packets have higher numbers. The oldest packet has number zero.
33877 The packet's offset in the trace stream.
33878 @item Packet opcode and payload
33882 @kindex maint btrace clear-packet-history
33883 @item maint btrace clear-packet-history
33884 Discards the cached packet history printed by the @samp{maint btrace
33885 packet-history} command. The history will be computed again when
33888 @kindex maint btrace clear
33889 @item maint btrace clear
33890 Discard the branch trace data. The data will be fetched anew and the
33891 branch trace will be recomputed when needed.
33893 This implicitly truncates the branch trace to a single branch trace
33894 buffer. When updating branch trace incrementally, the branch trace
33895 available to @value{GDBN} may be bigger than a single branch trace
33898 @kindex maint set btrace pt skip-pad
33899 @item maint set btrace pt skip-pad
33900 @kindex maint show btrace pt skip-pad
33901 @item maint show btrace pt skip-pad
33902 Control whether @value{GDBN} will skip PAD packets when computing the
33905 @kindex set displaced-stepping
33906 @kindex show displaced-stepping
33907 @cindex displaced stepping support
33908 @cindex out-of-line single-stepping
33909 @item set displaced-stepping
33910 @itemx show displaced-stepping
33911 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33912 if the target supports it. Displaced stepping is a way to single-step
33913 over breakpoints without removing them from the inferior, by executing
33914 an out-of-line copy of the instruction that was originally at the
33915 breakpoint location. It is also known as out-of-line single-stepping.
33918 @item set displaced-stepping on
33919 If the target architecture supports it, @value{GDBN} will use
33920 displaced stepping to step over breakpoints.
33922 @item set displaced-stepping off
33923 @value{GDBN} will not use displaced stepping to step over breakpoints,
33924 even if such is supported by the target architecture.
33926 @cindex non-stop mode, and @samp{set displaced-stepping}
33927 @item set displaced-stepping auto
33928 This is the default mode. @value{GDBN} will use displaced stepping
33929 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33930 architecture supports displaced stepping.
33933 @kindex maint check-psymtabs
33934 @item maint check-psymtabs
33935 Check the consistency of currently expanded psymtabs versus symtabs.
33936 Use this to check, for example, whether a symbol is in one but not the other.
33938 @kindex maint check-symtabs
33939 @item maint check-symtabs
33940 Check the consistency of currently expanded symtabs.
33942 @kindex maint expand-symtabs
33943 @item maint expand-symtabs [@var{regexp}]
33944 Expand symbol tables.
33945 If @var{regexp} is specified, only expand symbol tables for file
33946 names matching @var{regexp}.
33948 @kindex maint set catch-demangler-crashes
33949 @kindex maint show catch-demangler-crashes
33950 @cindex demangler crashes
33951 @item maint set catch-demangler-crashes [on|off]
33952 @itemx maint show catch-demangler-crashes
33953 Control whether @value{GDBN} should attempt to catch crashes in the
33954 symbol name demangler. The default is to attempt to catch crashes.
33955 If enabled, the first time a crash is caught, a core file is created,
33956 the offending symbol is displayed and the user is presented with the
33957 option to terminate the current session.
33959 @kindex maint cplus first_component
33960 @item maint cplus first_component @var{name}
33961 Print the first C@t{++} class/namespace component of @var{name}.
33963 @kindex maint cplus namespace
33964 @item maint cplus namespace
33965 Print the list of possible C@t{++} namespaces.
33967 @kindex maint deprecate
33968 @kindex maint undeprecate
33969 @cindex deprecated commands
33970 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33971 @itemx maint undeprecate @var{command}
33972 Deprecate or undeprecate the named @var{command}. Deprecated commands
33973 cause @value{GDBN} to issue a warning when you use them. The optional
33974 argument @var{replacement} says which newer command should be used in
33975 favor of the deprecated one; if it is given, @value{GDBN} will mention
33976 the replacement as part of the warning.
33978 @kindex maint dump-me
33979 @item maint dump-me
33980 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33981 Cause a fatal signal in the debugger and force it to dump its core.
33982 This is supported only on systems which support aborting a program
33983 with the @code{SIGQUIT} signal.
33985 @kindex maint internal-error
33986 @kindex maint internal-warning
33987 @kindex maint demangler-warning
33988 @cindex demangler crashes
33989 @item maint internal-error @r{[}@var{message-text}@r{]}
33990 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33991 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
33993 Cause @value{GDBN} to call the internal function @code{internal_error},
33994 @code{internal_warning} or @code{demangler_warning} and hence behave
33995 as though an internal problem has been detected. In addition to
33996 reporting the internal problem, these functions give the user the
33997 opportunity to either quit @value{GDBN} or (for @code{internal_error}
33998 and @code{internal_warning}) create a core file of the current
33999 @value{GDBN} session.
34001 These commands take an optional parameter @var{message-text} that is
34002 used as the text of the error or warning message.
34004 Here's an example of using @code{internal-error}:
34007 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34008 @dots{}/maint.c:121: internal-error: testing, 1, 2
34009 A problem internal to GDB has been detected. Further
34010 debugging may prove unreliable.
34011 Quit this debugging session? (y or n) @kbd{n}
34012 Create a core file? (y or n) @kbd{n}
34016 @cindex @value{GDBN} internal error
34017 @cindex internal errors, control of @value{GDBN} behavior
34018 @cindex demangler crashes
34020 @kindex maint set internal-error
34021 @kindex maint show internal-error
34022 @kindex maint set internal-warning
34023 @kindex maint show internal-warning
34024 @kindex maint set demangler-warning
34025 @kindex maint show demangler-warning
34026 @item maint set internal-error @var{action} [ask|yes|no]
34027 @itemx maint show internal-error @var{action}
34028 @itemx maint set internal-warning @var{action} [ask|yes|no]
34029 @itemx maint show internal-warning @var{action}
34030 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34031 @itemx maint show demangler-warning @var{action}
34032 When @value{GDBN} reports an internal problem (error or warning) it
34033 gives the user the opportunity to both quit @value{GDBN} and create a
34034 core file of the current @value{GDBN} session. These commands let you
34035 override the default behaviour for each particular @var{action},
34036 described in the table below.
34040 You can specify that @value{GDBN} should always (yes) or never (no)
34041 quit. The default is to ask the user what to do.
34044 You can specify that @value{GDBN} should always (yes) or never (no)
34045 create a core file. The default is to ask the user what to do. Note
34046 that there is no @code{corefile} option for @code{demangler-warning}:
34047 demangler warnings always create a core file and this cannot be
34051 @kindex maint packet
34052 @item maint packet @var{text}
34053 If @value{GDBN} is talking to an inferior via the serial protocol,
34054 then this command sends the string @var{text} to the inferior, and
34055 displays the response packet. @value{GDBN} supplies the initial
34056 @samp{$} character, the terminating @samp{#} character, and the
34059 @kindex maint print architecture
34060 @item maint print architecture @r{[}@var{file}@r{]}
34061 Print the entire architecture configuration. The optional argument
34062 @var{file} names the file where the output goes.
34064 @kindex maint print c-tdesc
34065 @item maint print c-tdesc
34066 Print the current target description (@pxref{Target Descriptions}) as
34067 a C source file. The created source file can be used in @value{GDBN}
34068 when an XML parser is not available to parse the description.
34070 @kindex maint print dummy-frames
34071 @item maint print dummy-frames
34072 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34075 (@value{GDBP}) @kbd{b add}
34077 (@value{GDBP}) @kbd{print add(2,3)}
34078 Breakpoint 2, add (a=2, b=3) at @dots{}
34080 The program being debugged stopped while in a function called from GDB.
34082 (@value{GDBP}) @kbd{maint print dummy-frames}
34083 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34087 Takes an optional file parameter.
34089 @kindex maint print registers
34090 @kindex maint print raw-registers
34091 @kindex maint print cooked-registers
34092 @kindex maint print register-groups
34093 @kindex maint print remote-registers
34094 @item maint print registers @r{[}@var{file}@r{]}
34095 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34096 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34097 @itemx maint print register-groups @r{[}@var{file}@r{]}
34098 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34099 Print @value{GDBN}'s internal register data structures.
34101 The command @code{maint print raw-registers} includes the contents of
34102 the raw register cache; the command @code{maint print
34103 cooked-registers} includes the (cooked) value of all registers,
34104 including registers which aren't available on the target nor visible
34105 to user; the command @code{maint print register-groups} includes the
34106 groups that each register is a member of; and the command @code{maint
34107 print remote-registers} includes the remote target's register numbers
34108 and offsets in the `G' packets.
34110 These commands take an optional parameter, a file name to which to
34111 write the information.
34113 @kindex maint print reggroups
34114 @item maint print reggroups @r{[}@var{file}@r{]}
34115 Print @value{GDBN}'s internal register group data structures. The
34116 optional argument @var{file} tells to what file to write the
34119 The register groups info looks like this:
34122 (@value{GDBP}) @kbd{maint print reggroups}
34135 This command forces @value{GDBN} to flush its internal register cache.
34137 @kindex maint print objfiles
34138 @cindex info for known object files
34139 @item maint print objfiles @r{[}@var{regexp}@r{]}
34140 Print a dump of all known object files.
34141 If @var{regexp} is specified, only print object files whose names
34142 match @var{regexp}. For each object file, this command prints its name,
34143 address in memory, and all of its psymtabs and symtabs.
34145 @kindex maint print user-registers
34146 @cindex user registers
34147 @item maint print user-registers
34148 List all currently available @dfn{user registers}. User registers
34149 typically provide alternate names for actual hardware registers. They
34150 include the four ``standard'' registers @code{$fp}, @code{$pc},
34151 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34152 registers can be used in expressions in the same way as the canonical
34153 register names, but only the latter are listed by the @code{info
34154 registers} and @code{maint print registers} commands.
34156 @kindex maint print section-scripts
34157 @cindex info for known .debug_gdb_scripts-loaded scripts
34158 @item maint print section-scripts [@var{regexp}]
34159 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34160 If @var{regexp} is specified, only print scripts loaded by object files
34161 matching @var{regexp}.
34162 For each script, this command prints its name as specified in the objfile,
34163 and the full path if known.
34164 @xref{dotdebug_gdb_scripts section}.
34166 @kindex maint print statistics
34167 @cindex bcache statistics
34168 @item maint print statistics
34169 This command prints, for each object file in the program, various data
34170 about that object file followed by the byte cache (@dfn{bcache})
34171 statistics for the object file. The objfile data includes the number
34172 of minimal, partial, full, and stabs symbols, the number of types
34173 defined by the objfile, the number of as yet unexpanded psym tables,
34174 the number of line tables and string tables, and the amount of memory
34175 used by the various tables. The bcache statistics include the counts,
34176 sizes, and counts of duplicates of all and unique objects, max,
34177 average, and median entry size, total memory used and its overhead and
34178 savings, and various measures of the hash table size and chain
34181 @kindex maint print target-stack
34182 @cindex target stack description
34183 @item maint print target-stack
34184 A @dfn{target} is an interface between the debugger and a particular
34185 kind of file or process. Targets can be stacked in @dfn{strata},
34186 so that more than one target can potentially respond to a request.
34187 In particular, memory accesses will walk down the stack of targets
34188 until they find a target that is interested in handling that particular
34191 This command prints a short description of each layer that was pushed on
34192 the @dfn{target stack}, starting from the top layer down to the bottom one.
34194 @kindex maint print type
34195 @cindex type chain of a data type
34196 @item maint print type @var{expr}
34197 Print the type chain for a type specified by @var{expr}. The argument
34198 can be either a type name or a symbol. If it is a symbol, the type of
34199 that symbol is described. The type chain produced by this command is
34200 a recursive definition of the data type as stored in @value{GDBN}'s
34201 data structures, including its flags and contained types.
34203 @kindex maint set dwarf always-disassemble
34204 @kindex maint show dwarf always-disassemble
34205 @item maint set dwarf always-disassemble
34206 @item maint show dwarf always-disassemble
34207 Control the behavior of @code{info address} when using DWARF debugging
34210 The default is @code{off}, which means that @value{GDBN} should try to
34211 describe a variable's location in an easily readable format. When
34212 @code{on}, @value{GDBN} will instead display the DWARF location
34213 expression in an assembly-like format. Note that some locations are
34214 too complex for @value{GDBN} to describe simply; in this case you will
34215 always see the disassembly form.
34217 Here is an example of the resulting disassembly:
34220 (gdb) info addr argc
34221 Symbol "argc" is a complex DWARF expression:
34225 For more information on these expressions, see
34226 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34228 @kindex maint set dwarf max-cache-age
34229 @kindex maint show dwarf max-cache-age
34230 @item maint set dwarf max-cache-age
34231 @itemx maint show dwarf max-cache-age
34232 Control the DWARF compilation unit cache.
34234 @cindex DWARF compilation units cache
34235 In object files with inter-compilation-unit references, such as those
34236 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34237 reader needs to frequently refer to previously read compilation units.
34238 This setting controls how long a compilation unit will remain in the
34239 cache if it is not referenced. A higher limit means that cached
34240 compilation units will be stored in memory longer, and more total
34241 memory will be used. Setting it to zero disables caching, which will
34242 slow down @value{GDBN} startup, but reduce memory consumption.
34244 @kindex maint set profile
34245 @kindex maint show profile
34246 @cindex profiling GDB
34247 @item maint set profile
34248 @itemx maint show profile
34249 Control profiling of @value{GDBN}.
34251 Profiling will be disabled until you use the @samp{maint set profile}
34252 command to enable it. When you enable profiling, the system will begin
34253 collecting timing and execution count data; when you disable profiling or
34254 exit @value{GDBN}, the results will be written to a log file. Remember that
34255 if you use profiling, @value{GDBN} will overwrite the profiling log file
34256 (often called @file{gmon.out}). If you have a record of important profiling
34257 data in a @file{gmon.out} file, be sure to move it to a safe location.
34259 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34260 compiled with the @samp{-pg} compiler option.
34262 @kindex maint set show-debug-regs
34263 @kindex maint show show-debug-regs
34264 @cindex hardware debug registers
34265 @item maint set show-debug-regs
34266 @itemx maint show show-debug-regs
34267 Control whether to show variables that mirror the hardware debug
34268 registers. Use @code{on} to enable, @code{off} to disable. If
34269 enabled, the debug registers values are shown when @value{GDBN} inserts or
34270 removes a hardware breakpoint or watchpoint, and when the inferior
34271 triggers a hardware-assisted breakpoint or watchpoint.
34273 @kindex maint set show-all-tib
34274 @kindex maint show show-all-tib
34275 @item maint set show-all-tib
34276 @itemx maint show show-all-tib
34277 Control whether to show all non zero areas within a 1k block starting
34278 at thread local base, when using the @samp{info w32 thread-information-block}
34281 @kindex maint set target-async
34282 @kindex maint show target-async
34283 @item maint set target-async
34284 @itemx maint show target-async
34285 This controls whether @value{GDBN} targets operate in synchronous or
34286 asynchronous mode (@pxref{Background Execution}). Normally the
34287 default is asynchronous, if it is available; but this can be changed
34288 to more easily debug problems occurring only in synchronous mode.
34290 @kindex maint set target-non-stop @var{mode} [on|off|auto]
34291 @kindex maint show target-non-stop
34292 @item maint set target-non-stop
34293 @itemx maint show target-non-stop
34295 This controls whether @value{GDBN} targets always operate in non-stop
34296 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
34297 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
34298 if supported by the target.
34301 @item maint set target-non-stop auto
34302 This is the default mode. @value{GDBN} controls the target in
34303 non-stop mode if the target supports it.
34305 @item maint set target-non-stop on
34306 @value{GDBN} controls the target in non-stop mode even if the target
34307 does not indicate support.
34309 @item maint set target-non-stop off
34310 @value{GDBN} does not control the target in non-stop mode even if the
34311 target supports it.
34314 @kindex maint set per-command
34315 @kindex maint show per-command
34316 @item maint set per-command
34317 @itemx maint show per-command
34318 @cindex resources used by commands
34320 @value{GDBN} can display the resources used by each command.
34321 This is useful in debugging performance problems.
34324 @item maint set per-command space [on|off]
34325 @itemx maint show per-command space
34326 Enable or disable the printing of the memory used by GDB for each command.
34327 If enabled, @value{GDBN} will display how much memory each command
34328 took, following the command's own output.
34329 This can also be requested by invoking @value{GDBN} with the
34330 @option{--statistics} command-line switch (@pxref{Mode Options}).
34332 @item maint set per-command time [on|off]
34333 @itemx maint show per-command time
34334 Enable or disable the printing of the execution time of @value{GDBN}
34336 If enabled, @value{GDBN} will display how much time it
34337 took to execute each command, following the command's own output.
34338 Both CPU time and wallclock time are printed.
34339 Printing both is useful when trying to determine whether the cost is
34340 CPU or, e.g., disk/network latency.
34341 Note that the CPU time printed is for @value{GDBN} only, it does not include
34342 the execution time of the inferior because there's no mechanism currently
34343 to compute how much time was spent by @value{GDBN} and how much time was
34344 spent by the program been debugged.
34345 This can also be requested by invoking @value{GDBN} with the
34346 @option{--statistics} command-line switch (@pxref{Mode Options}).
34348 @item maint set per-command symtab [on|off]
34349 @itemx maint show per-command symtab
34350 Enable or disable the printing of basic symbol table statistics
34352 If enabled, @value{GDBN} will display the following information:
34356 number of symbol tables
34358 number of primary symbol tables
34360 number of blocks in the blockvector
34364 @kindex maint space
34365 @cindex memory used by commands
34366 @item maint space @var{value}
34367 An alias for @code{maint set per-command space}.
34368 A non-zero value enables it, zero disables it.
34371 @cindex time of command execution
34372 @item maint time @var{value}
34373 An alias for @code{maint set per-command time}.
34374 A non-zero value enables it, zero disables it.
34376 @kindex maint translate-address
34377 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34378 Find the symbol stored at the location specified by the address
34379 @var{addr} and an optional section name @var{section}. If found,
34380 @value{GDBN} prints the name of the closest symbol and an offset from
34381 the symbol's location to the specified address. This is similar to
34382 the @code{info address} command (@pxref{Symbols}), except that this
34383 command also allows to find symbols in other sections.
34385 If section was not specified, the section in which the symbol was found
34386 is also printed. For dynamically linked executables, the name of
34387 executable or shared library containing the symbol is printed as well.
34391 The following command is useful for non-interactive invocations of
34392 @value{GDBN}, such as in the test suite.
34395 @item set watchdog @var{nsec}
34396 @kindex set watchdog
34397 @cindex watchdog timer
34398 @cindex timeout for commands
34399 Set the maximum number of seconds @value{GDBN} will wait for the
34400 target operation to finish. If this time expires, @value{GDBN}
34401 reports and error and the command is aborted.
34403 @item show watchdog
34404 Show the current setting of the target wait timeout.
34407 @node Remote Protocol
34408 @appendix @value{GDBN} Remote Serial Protocol
34413 * Stop Reply Packets::
34414 * General Query Packets::
34415 * Architecture-Specific Protocol Details::
34416 * Tracepoint Packets::
34417 * Host I/O Packets::
34419 * Notification Packets::
34420 * Remote Non-Stop::
34421 * Packet Acknowledgment::
34423 * File-I/O Remote Protocol Extension::
34424 * Library List Format::
34425 * Library List Format for SVR4 Targets::
34426 * Memory Map Format::
34427 * Thread List Format::
34428 * Traceframe Info Format::
34429 * Branch Trace Format::
34430 * Branch Trace Configuration Format::
34436 There may be occasions when you need to know something about the
34437 protocol---for example, if there is only one serial port to your target
34438 machine, you might want your program to do something special if it
34439 recognizes a packet meant for @value{GDBN}.
34441 In the examples below, @samp{->} and @samp{<-} are used to indicate
34442 transmitted and received data, respectively.
34444 @cindex protocol, @value{GDBN} remote serial
34445 @cindex serial protocol, @value{GDBN} remote
34446 @cindex remote serial protocol
34447 All @value{GDBN} commands and responses (other than acknowledgments
34448 and notifications, see @ref{Notification Packets}) are sent as a
34449 @var{packet}. A @var{packet} is introduced with the character
34450 @samp{$}, the actual @var{packet-data}, and the terminating character
34451 @samp{#} followed by a two-digit @var{checksum}:
34454 @code{$}@var{packet-data}@code{#}@var{checksum}
34458 @cindex checksum, for @value{GDBN} remote
34460 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34461 characters between the leading @samp{$} and the trailing @samp{#} (an
34462 eight bit unsigned checksum).
34464 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34465 specification also included an optional two-digit @var{sequence-id}:
34468 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34471 @cindex sequence-id, for @value{GDBN} remote
34473 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34474 has never output @var{sequence-id}s. Stubs that handle packets added
34475 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34477 When either the host or the target machine receives a packet, the first
34478 response expected is an acknowledgment: either @samp{+} (to indicate
34479 the package was received correctly) or @samp{-} (to request
34483 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34488 The @samp{+}/@samp{-} acknowledgments can be disabled
34489 once a connection is established.
34490 @xref{Packet Acknowledgment}, for details.
34492 The host (@value{GDBN}) sends @var{command}s, and the target (the
34493 debugging stub incorporated in your program) sends a @var{response}. In
34494 the case of step and continue @var{command}s, the response is only sent
34495 when the operation has completed, and the target has again stopped all
34496 threads in all attached processes. This is the default all-stop mode
34497 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34498 execution mode; see @ref{Remote Non-Stop}, for details.
34500 @var{packet-data} consists of a sequence of characters with the
34501 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34504 @cindex remote protocol, field separator
34505 Fields within the packet should be separated using @samp{,} @samp{;} or
34506 @samp{:}. Except where otherwise noted all numbers are represented in
34507 @sc{hex} with leading zeros suppressed.
34509 Implementors should note that prior to @value{GDBN} 5.0, the character
34510 @samp{:} could not appear as the third character in a packet (as it
34511 would potentially conflict with the @var{sequence-id}).
34513 @cindex remote protocol, binary data
34514 @anchor{Binary Data}
34515 Binary data in most packets is encoded either as two hexadecimal
34516 digits per byte of binary data. This allowed the traditional remote
34517 protocol to work over connections which were only seven-bit clean.
34518 Some packets designed more recently assume an eight-bit clean
34519 connection, and use a more efficient encoding to send and receive
34522 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34523 as an escape character. Any escaped byte is transmitted as the escape
34524 character followed by the original character XORed with @code{0x20}.
34525 For example, the byte @code{0x7d} would be transmitted as the two
34526 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34527 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34528 @samp{@}}) must always be escaped. Responses sent by the stub
34529 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34530 is not interpreted as the start of a run-length encoded sequence
34533 Response @var{data} can be run-length encoded to save space.
34534 Run-length encoding replaces runs of identical characters with one
34535 instance of the repeated character, followed by a @samp{*} and a
34536 repeat count. The repeat count is itself sent encoded, to avoid
34537 binary characters in @var{data}: a value of @var{n} is sent as
34538 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34539 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34540 code 32) for a repeat count of 3. (This is because run-length
34541 encoding starts to win for counts 3 or more.) Thus, for example,
34542 @samp{0* } is a run-length encoding of ``0000'': the space character
34543 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34546 The printable characters @samp{#} and @samp{$} or with a numeric value
34547 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34548 seven repeats (@samp{$}) can be expanded using a repeat count of only
34549 five (@samp{"}). For example, @samp{00000000} can be encoded as
34552 The error response returned for some packets includes a two character
34553 error number. That number is not well defined.
34555 @cindex empty response, for unsupported packets
34556 For any @var{command} not supported by the stub, an empty response
34557 (@samp{$#00}) should be returned. That way it is possible to extend the
34558 protocol. A newer @value{GDBN} can tell if a packet is supported based
34561 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34562 commands for register access, and the @samp{m} and @samp{M} commands
34563 for memory access. Stubs that only control single-threaded targets
34564 can implement run control with the @samp{c} (continue), and @samp{s}
34565 (step) commands. Stubs that support multi-threading targets should
34566 support the @samp{vCont} command. All other commands are optional.
34571 The following table provides a complete list of all currently defined
34572 @var{command}s and their corresponding response @var{data}.
34573 @xref{File-I/O Remote Protocol Extension}, for details about the File
34574 I/O extension of the remote protocol.
34576 Each packet's description has a template showing the packet's overall
34577 syntax, followed by an explanation of the packet's meaning. We
34578 include spaces in some of the templates for clarity; these are not
34579 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34580 separate its components. For example, a template like @samp{foo
34581 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34582 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34583 @var{baz}. @value{GDBN} does not transmit a space character between the
34584 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34587 @cindex @var{thread-id}, in remote protocol
34588 @anchor{thread-id syntax}
34589 Several packets and replies include a @var{thread-id} field to identify
34590 a thread. Normally these are positive numbers with a target-specific
34591 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34592 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34595 In addition, the remote protocol supports a multiprocess feature in
34596 which the @var{thread-id} syntax is extended to optionally include both
34597 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34598 The @var{pid} (process) and @var{tid} (thread) components each have the
34599 format described above: a positive number with target-specific
34600 interpretation formatted as a big-endian hex string, literal @samp{-1}
34601 to indicate all processes or threads (respectively), or @samp{0} to
34602 indicate an arbitrary process or thread. Specifying just a process, as
34603 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34604 error to specify all processes but a specific thread, such as
34605 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34606 for those packets and replies explicitly documented to include a process
34607 ID, rather than a @var{thread-id}.
34609 The multiprocess @var{thread-id} syntax extensions are only used if both
34610 @value{GDBN} and the stub report support for the @samp{multiprocess}
34611 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34614 Note that all packet forms beginning with an upper- or lower-case
34615 letter, other than those described here, are reserved for future use.
34617 Here are the packet descriptions.
34622 @cindex @samp{!} packet
34623 @anchor{extended mode}
34624 Enable extended mode. In extended mode, the remote server is made
34625 persistent. The @samp{R} packet is used to restart the program being
34631 The remote target both supports and has enabled extended mode.
34635 @cindex @samp{?} packet
34637 Indicate the reason the target halted. The reply is the same as for
34638 step and continue. This packet has a special interpretation when the
34639 target is in non-stop mode; see @ref{Remote Non-Stop}.
34642 @xref{Stop Reply Packets}, for the reply specifications.
34644 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34645 @cindex @samp{A} packet
34646 Initialized @code{argv[]} array passed into program. @var{arglen}
34647 specifies the number of bytes in the hex encoded byte stream
34648 @var{arg}. See @code{gdbserver} for more details.
34653 The arguments were set.
34659 @cindex @samp{b} packet
34660 (Don't use this packet; its behavior is not well-defined.)
34661 Change the serial line speed to @var{baud}.
34663 JTC: @emph{When does the transport layer state change? When it's
34664 received, or after the ACK is transmitted. In either case, there are
34665 problems if the command or the acknowledgment packet is dropped.}
34667 Stan: @emph{If people really wanted to add something like this, and get
34668 it working for the first time, they ought to modify ser-unix.c to send
34669 some kind of out-of-band message to a specially-setup stub and have the
34670 switch happen "in between" packets, so that from remote protocol's point
34671 of view, nothing actually happened.}
34673 @item B @var{addr},@var{mode}
34674 @cindex @samp{B} packet
34675 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34676 breakpoint at @var{addr}.
34678 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34679 (@pxref{insert breakpoint or watchpoint packet}).
34681 @cindex @samp{bc} packet
34684 Backward continue. Execute the target system in reverse. No parameter.
34685 @xref{Reverse Execution}, for more information.
34688 @xref{Stop Reply Packets}, for the reply specifications.
34690 @cindex @samp{bs} packet
34693 Backward single step. Execute one instruction in reverse. No parameter.
34694 @xref{Reverse Execution}, for more information.
34697 @xref{Stop Reply Packets}, for the reply specifications.
34699 @item c @r{[}@var{addr}@r{]}
34700 @cindex @samp{c} packet
34701 Continue at @var{addr}, which is the address to resume. If @var{addr}
34702 is omitted, resume at current address.
34704 This packet is deprecated for multi-threading support. @xref{vCont
34708 @xref{Stop Reply Packets}, for the reply specifications.
34710 @item C @var{sig}@r{[};@var{addr}@r{]}
34711 @cindex @samp{C} packet
34712 Continue with signal @var{sig} (hex signal number). If
34713 @samp{;@var{addr}} is omitted, resume at same address.
34715 This packet is deprecated for multi-threading support. @xref{vCont
34719 @xref{Stop Reply Packets}, for the reply specifications.
34722 @cindex @samp{d} packet
34725 Don't use this packet; instead, define a general set packet
34726 (@pxref{General Query Packets}).
34730 @cindex @samp{D} packet
34731 The first form of the packet is used to detach @value{GDBN} from the
34732 remote system. It is sent to the remote target
34733 before @value{GDBN} disconnects via the @code{detach} command.
34735 The second form, including a process ID, is used when multiprocess
34736 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34737 detach only a specific process. The @var{pid} is specified as a
34738 big-endian hex string.
34748 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34749 @cindex @samp{F} packet
34750 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34751 This is part of the File-I/O protocol extension. @xref{File-I/O
34752 Remote Protocol Extension}, for the specification.
34755 @anchor{read registers packet}
34756 @cindex @samp{g} packet
34757 Read general registers.
34761 @item @var{XX@dots{}}
34762 Each byte of register data is described by two hex digits. The bytes
34763 with the register are transmitted in target byte order. The size of
34764 each register and their position within the @samp{g} packet are
34765 determined by the @value{GDBN} internal gdbarch functions
34766 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34767 specification of several standard @samp{g} packets is specified below.
34769 When reading registers from a trace frame (@pxref{Analyze Collected
34770 Data,,Using the Collected Data}), the stub may also return a string of
34771 literal @samp{x}'s in place of the register data digits, to indicate
34772 that the corresponding register has not been collected, thus its value
34773 is unavailable. For example, for an architecture with 4 registers of
34774 4 bytes each, the following reply indicates to @value{GDBN} that
34775 registers 0 and 2 have not been collected, while registers 1 and 3
34776 have been collected, and both have zero value:
34780 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34787 @item G @var{XX@dots{}}
34788 @cindex @samp{G} packet
34789 Write general registers. @xref{read registers packet}, for a
34790 description of the @var{XX@dots{}} data.
34800 @item H @var{op} @var{thread-id}
34801 @cindex @samp{H} packet
34802 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34803 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34804 should be @samp{c} for step and continue operations (note that this
34805 is deprecated, supporting the @samp{vCont} command is a better
34806 option), and @samp{g} for other operations. The thread designator
34807 @var{thread-id} has the format and interpretation described in
34808 @ref{thread-id syntax}.
34819 @c 'H': How restrictive (or permissive) is the thread model. If a
34820 @c thread is selected and stopped, are other threads allowed
34821 @c to continue to execute? As I mentioned above, I think the
34822 @c semantics of each command when a thread is selected must be
34823 @c described. For example:
34825 @c 'g': If the stub supports threads and a specific thread is
34826 @c selected, returns the register block from that thread;
34827 @c otherwise returns current registers.
34829 @c 'G' If the stub supports threads and a specific thread is
34830 @c selected, sets the registers of the register block of
34831 @c that thread; otherwise sets current registers.
34833 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34834 @anchor{cycle step packet}
34835 @cindex @samp{i} packet
34836 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34837 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34838 step starting at that address.
34841 @cindex @samp{I} packet
34842 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34846 @cindex @samp{k} packet
34849 The exact effect of this packet is not specified.
34851 For a bare-metal target, it may power cycle or reset the target
34852 system. For that reason, the @samp{k} packet has no reply.
34854 For a single-process target, it may kill that process if possible.
34856 A multiple-process target may choose to kill just one process, or all
34857 that are under @value{GDBN}'s control. For more precise control, use
34858 the vKill packet (@pxref{vKill packet}).
34860 If the target system immediately closes the connection in response to
34861 @samp{k}, @value{GDBN} does not consider the lack of packet
34862 acknowledgment to be an error, and assumes the kill was successful.
34864 If connected using @kbd{target extended-remote}, and the target does
34865 not close the connection in response to a kill request, @value{GDBN}
34866 probes the target state as if a new connection was opened
34867 (@pxref{? packet}).
34869 @item m @var{addr},@var{length}
34870 @cindex @samp{m} packet
34871 Read @var{length} addressable memory units starting at address @var{addr}
34872 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
34873 any particular boundary.
34875 The stub need not use any particular size or alignment when gathering
34876 data from memory for the response; even if @var{addr} is word-aligned
34877 and @var{length} is a multiple of the word size, the stub is free to
34878 use byte accesses, or not. For this reason, this packet may not be
34879 suitable for accessing memory-mapped I/O devices.
34880 @cindex alignment of remote memory accesses
34881 @cindex size of remote memory accesses
34882 @cindex memory, alignment and size of remote accesses
34886 @item @var{XX@dots{}}
34887 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
34888 The reply may contain fewer addressable memory units than requested if the
34889 server was able to read only part of the region of memory.
34894 @item M @var{addr},@var{length}:@var{XX@dots{}}
34895 @cindex @samp{M} packet
34896 Write @var{length} addressable memory units starting at address @var{addr}
34897 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
34898 byte is transmitted as a two-digit hexadecimal number.
34905 for an error (this includes the case where only part of the data was
34910 @cindex @samp{p} packet
34911 Read the value of register @var{n}; @var{n} is in hex.
34912 @xref{read registers packet}, for a description of how the returned
34913 register value is encoded.
34917 @item @var{XX@dots{}}
34918 the register's value
34922 Indicating an unrecognized @var{query}.
34925 @item P @var{n@dots{}}=@var{r@dots{}}
34926 @anchor{write register packet}
34927 @cindex @samp{P} packet
34928 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34929 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34930 digits for each byte in the register (target byte order).
34940 @item q @var{name} @var{params}@dots{}
34941 @itemx Q @var{name} @var{params}@dots{}
34942 @cindex @samp{q} packet
34943 @cindex @samp{Q} packet
34944 General query (@samp{q}) and set (@samp{Q}). These packets are
34945 described fully in @ref{General Query Packets}.
34948 @cindex @samp{r} packet
34949 Reset the entire system.
34951 Don't use this packet; use the @samp{R} packet instead.
34954 @cindex @samp{R} packet
34955 Restart the program being debugged. The @var{XX}, while needed, is ignored.
34956 This packet is only available in extended mode (@pxref{extended mode}).
34958 The @samp{R} packet has no reply.
34960 @item s @r{[}@var{addr}@r{]}
34961 @cindex @samp{s} packet
34962 Single step, resuming at @var{addr}. If
34963 @var{addr} is omitted, resume at same address.
34965 This packet is deprecated for multi-threading support. @xref{vCont
34969 @xref{Stop Reply Packets}, for the reply specifications.
34971 @item S @var{sig}@r{[};@var{addr}@r{]}
34972 @anchor{step with signal packet}
34973 @cindex @samp{S} packet
34974 Step with signal. This is analogous to the @samp{C} packet, but
34975 requests a single-step, rather than a normal resumption of execution.
34977 This packet is deprecated for multi-threading support. @xref{vCont
34981 @xref{Stop Reply Packets}, for the reply specifications.
34983 @item t @var{addr}:@var{PP},@var{MM}
34984 @cindex @samp{t} packet
34985 Search backwards starting at address @var{addr} for a match with pattern
34986 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
34987 There must be at least 3 digits in @var{addr}.
34989 @item T @var{thread-id}
34990 @cindex @samp{T} packet
34991 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34996 thread is still alive
35002 Packets starting with @samp{v} are identified by a multi-letter name,
35003 up to the first @samp{;} or @samp{?} (or the end of the packet).
35005 @item vAttach;@var{pid}
35006 @cindex @samp{vAttach} packet
35007 Attach to a new process with the specified process ID @var{pid}.
35008 The process ID is a
35009 hexadecimal integer identifying the process. In all-stop mode, all
35010 threads in the attached process are stopped; in non-stop mode, it may be
35011 attached without being stopped if that is supported by the target.
35013 @c In non-stop mode, on a successful vAttach, the stub should set the
35014 @c current thread to a thread of the newly-attached process. After
35015 @c attaching, GDB queries for the attached process's thread ID with qC.
35016 @c Also note that, from a user perspective, whether or not the
35017 @c target is stopped on attach in non-stop mode depends on whether you
35018 @c use the foreground or background version of the attach command, not
35019 @c on what vAttach does; GDB does the right thing with respect to either
35020 @c stopping or restarting threads.
35022 This packet is only available in extended mode (@pxref{extended mode}).
35028 @item @r{Any stop packet}
35029 for success in all-stop mode (@pxref{Stop Reply Packets})
35031 for success in non-stop mode (@pxref{Remote Non-Stop})
35034 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35035 @cindex @samp{vCont} packet
35036 @anchor{vCont packet}
35037 Resume the inferior, specifying different actions for each thread.
35038 If an action is specified with no @var{thread-id}, then it is applied to any
35039 threads that don't have a specific action specified; if no default action is
35040 specified then other threads should remain stopped in all-stop mode and
35041 in their current state in non-stop mode.
35042 Specifying multiple
35043 default actions is an error; specifying no actions is also an error.
35044 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
35046 Currently supported actions are:
35052 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35056 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35059 @item r @var{start},@var{end}
35060 Step once, and then keep stepping as long as the thread stops at
35061 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35062 The remote stub reports a stop reply when either the thread goes out
35063 of the range or is stopped due to an unrelated reason, such as hitting
35064 a breakpoint. @xref{range stepping}.
35066 If the range is empty (@var{start} == @var{end}), then the action
35067 becomes equivalent to the @samp{s} action. In other words,
35068 single-step once, and report the stop (even if the stepped instruction
35069 jumps to @var{start}).
35071 (A stop reply may be sent at any point even if the PC is still within
35072 the stepping range; for example, it is valid to implement this packet
35073 in a degenerate way as a single instruction step operation.)
35077 The optional argument @var{addr} normally associated with the
35078 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35079 not supported in @samp{vCont}.
35081 The @samp{t} action is only relevant in non-stop mode
35082 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35083 A stop reply should be generated for any affected thread not already stopped.
35084 When a thread is stopped by means of a @samp{t} action,
35085 the corresponding stop reply should indicate that the thread has stopped with
35086 signal @samp{0}, regardless of whether the target uses some other signal
35087 as an implementation detail.
35089 The stub must support @samp{vCont} if it reports support for
35090 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
35091 this case @samp{vCont} actions can be specified to apply to all threads
35092 in a process by using the @samp{p@var{pid}.-1} form of the
35096 @xref{Stop Reply Packets}, for the reply specifications.
35099 @cindex @samp{vCont?} packet
35100 Request a list of actions supported by the @samp{vCont} packet.
35104 @item vCont@r{[};@var{action}@dots{}@r{]}
35105 The @samp{vCont} packet is supported. Each @var{action} is a supported
35106 command in the @samp{vCont} packet.
35108 The @samp{vCont} packet is not supported.
35111 @anchor{vCtrlC packet}
35113 @cindex @samp{vCtrlC} packet
35114 Interrupt remote target as if a control-C was pressed on the remote
35115 terminal. This is the equivalent to reacting to the @code{^C}
35116 (@samp{\003}, the control-C character) character in all-stop mode
35117 while the target is running, except this works in non-stop mode.
35118 @xref{interrupting remote targets}, for more info on the all-stop
35129 @item vFile:@var{operation}:@var{parameter}@dots{}
35130 @cindex @samp{vFile} packet
35131 Perform a file operation on the target system. For details,
35132 see @ref{Host I/O Packets}.
35134 @item vFlashErase:@var{addr},@var{length}
35135 @cindex @samp{vFlashErase} packet
35136 Direct the stub to erase @var{length} bytes of flash starting at
35137 @var{addr}. The region may enclose any number of flash blocks, but
35138 its start and end must fall on block boundaries, as indicated by the
35139 flash block size appearing in the memory map (@pxref{Memory Map
35140 Format}). @value{GDBN} groups flash memory programming operations
35141 together, and sends a @samp{vFlashDone} request after each group; the
35142 stub is allowed to delay erase operation until the @samp{vFlashDone}
35143 packet is received.
35153 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35154 @cindex @samp{vFlashWrite} packet
35155 Direct the stub to write data to flash address @var{addr}. The data
35156 is passed in binary form using the same encoding as for the @samp{X}
35157 packet (@pxref{Binary Data}). The memory ranges specified by
35158 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35159 not overlap, and must appear in order of increasing addresses
35160 (although @samp{vFlashErase} packets for higher addresses may already
35161 have been received; the ordering is guaranteed only between
35162 @samp{vFlashWrite} packets). If a packet writes to an address that was
35163 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35164 target-specific method, the results are unpredictable.
35172 for vFlashWrite addressing non-flash memory
35178 @cindex @samp{vFlashDone} packet
35179 Indicate to the stub that flash programming operation is finished.
35180 The stub is permitted to delay or batch the effects of a group of
35181 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35182 @samp{vFlashDone} packet is received. The contents of the affected
35183 regions of flash memory are unpredictable until the @samp{vFlashDone}
35184 request is completed.
35186 @item vKill;@var{pid}
35187 @cindex @samp{vKill} packet
35188 @anchor{vKill packet}
35189 Kill the process with the specified process ID @var{pid}, which is a
35190 hexadecimal integer identifying the process. This packet is used in
35191 preference to @samp{k} when multiprocess protocol extensions are
35192 supported; see @ref{multiprocess extensions}.
35202 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35203 @cindex @samp{vRun} packet
35204 Run the program @var{filename}, passing it each @var{argument} on its
35205 command line. The file and arguments are hex-encoded strings. If
35206 @var{filename} is an empty string, the stub may use a default program
35207 (e.g.@: the last program run). The program is created in the stopped
35210 @c FIXME: What about non-stop mode?
35212 This packet is only available in extended mode (@pxref{extended mode}).
35218 @item @r{Any stop packet}
35219 for success (@pxref{Stop Reply Packets})
35223 @cindex @samp{vStopped} packet
35224 @xref{Notification Packets}.
35226 @item X @var{addr},@var{length}:@var{XX@dots{}}
35228 @cindex @samp{X} packet
35229 Write data to memory, where the data is transmitted in binary.
35230 Memory is specified by its address @var{addr} and number of addressable memory
35231 units @var{length} (@pxref{addressable memory unit});
35232 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35242 @item z @var{type},@var{addr},@var{kind}
35243 @itemx Z @var{type},@var{addr},@var{kind}
35244 @anchor{insert breakpoint or watchpoint packet}
35245 @cindex @samp{z} packet
35246 @cindex @samp{Z} packets
35247 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35248 watchpoint starting at address @var{address} of kind @var{kind}.
35250 Each breakpoint and watchpoint packet @var{type} is documented
35253 @emph{Implementation notes: A remote target shall return an empty string
35254 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35255 remote target shall support either both or neither of a given
35256 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35257 avoid potential problems with duplicate packets, the operations should
35258 be implemented in an idempotent way.}
35260 @item z0,@var{addr},@var{kind}
35261 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35262 @cindex @samp{z0} packet
35263 @cindex @samp{Z0} packet
35264 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35265 @var{addr} of type @var{kind}.
35267 A memory breakpoint is implemented by replacing the instruction at
35268 @var{addr} with a software breakpoint or trap instruction. The
35269 @var{kind} is target-specific and typically indicates the size of
35270 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35271 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35272 architectures have additional meanings for @var{kind};
35273 @var{cond_list} is an optional list of conditional expressions in bytecode
35274 form that should be evaluated on the target's side. These are the
35275 conditions that should be taken into consideration when deciding if
35276 the breakpoint trigger should be reported back to @var{GDBN}.
35278 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35279 for how to best report a memory breakpoint event to @value{GDBN}.
35281 The @var{cond_list} parameter is comprised of a series of expressions,
35282 concatenated without separators. Each expression has the following form:
35286 @item X @var{len},@var{expr}
35287 @var{len} is the length of the bytecode expression and @var{expr} is the
35288 actual conditional expression in bytecode form.
35292 The optional @var{cmd_list} parameter introduces commands that may be
35293 run on the target, rather than being reported back to @value{GDBN}.
35294 The parameter starts with a numeric flag @var{persist}; if the flag is
35295 nonzero, then the breakpoint may remain active and the commands
35296 continue to be run even when @value{GDBN} disconnects from the target.
35297 Following this flag is a series of expressions concatenated with no
35298 separators. Each expression has the following form:
35302 @item X @var{len},@var{expr}
35303 @var{len} is the length of the bytecode expression and @var{expr} is the
35304 actual conditional expression in bytecode form.
35308 see @ref{Architecture-Specific Protocol Details}.
35310 @emph{Implementation note: It is possible for a target to copy or move
35311 code that contains memory breakpoints (e.g., when implementing
35312 overlays). The behavior of this packet, in the presence of such a
35313 target, is not defined.}
35325 @item z1,@var{addr},@var{kind}
35326 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35327 @cindex @samp{z1} packet
35328 @cindex @samp{Z1} packet
35329 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35330 address @var{addr}.
35332 A hardware breakpoint is implemented using a mechanism that is not
35333 dependant on being able to modify the target's memory. The @var{kind}
35334 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35336 @emph{Implementation note: A hardware breakpoint is not affected by code
35349 @item z2,@var{addr},@var{kind}
35350 @itemx Z2,@var{addr},@var{kind}
35351 @cindex @samp{z2} packet
35352 @cindex @samp{Z2} packet
35353 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35354 The number of bytes to watch is specified by @var{kind}.
35366 @item z3,@var{addr},@var{kind}
35367 @itemx Z3,@var{addr},@var{kind}
35368 @cindex @samp{z3} packet
35369 @cindex @samp{Z3} packet
35370 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35371 The number of bytes to watch is specified by @var{kind}.
35383 @item z4,@var{addr},@var{kind}
35384 @itemx Z4,@var{addr},@var{kind}
35385 @cindex @samp{z4} packet
35386 @cindex @samp{Z4} packet
35387 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35388 The number of bytes to watch is specified by @var{kind}.
35402 @node Stop Reply Packets
35403 @section Stop Reply Packets
35404 @cindex stop reply packets
35406 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35407 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35408 receive any of the below as a reply. Except for @samp{?}
35409 and @samp{vStopped}, that reply is only returned
35410 when the target halts. In the below the exact meaning of @dfn{signal
35411 number} is defined by the header @file{include/gdb/signals.h} in the
35412 @value{GDBN} source code.
35414 As in the description of request packets, we include spaces in the
35415 reply templates for clarity; these are not part of the reply packet's
35416 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35422 The program received signal number @var{AA} (a two-digit hexadecimal
35423 number). This is equivalent to a @samp{T} response with no
35424 @var{n}:@var{r} pairs.
35426 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35427 @cindex @samp{T} packet reply
35428 The program received signal number @var{AA} (a two-digit hexadecimal
35429 number). This is equivalent to an @samp{S} response, except that the
35430 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35431 and other information directly in the stop reply packet, reducing
35432 round-trip latency. Single-step and breakpoint traps are reported
35433 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35437 If @var{n} is a hexadecimal number, it is a register number, and the
35438 corresponding @var{r} gives that register's value. The data @var{r} is a
35439 series of bytes in target byte order, with each byte given by a
35440 two-digit hex number.
35443 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35444 the stopped thread, as specified in @ref{thread-id syntax}.
35447 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35448 the core on which the stop event was detected.
35451 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35452 specific event that stopped the target. The currently defined stop
35453 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35454 signal. At most one stop reason should be present.
35457 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35458 and go on to the next; this allows us to extend the protocol in the
35462 The currently defined stop reasons are:
35468 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35471 @cindex shared library events, remote reply
35473 The packet indicates that the loaded libraries have changed.
35474 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35475 list of loaded libraries. The @var{r} part is ignored.
35477 @cindex replay log events, remote reply
35479 The packet indicates that the target cannot continue replaying
35480 logged execution events, because it has reached the end (or the
35481 beginning when executing backward) of the log. The value of @var{r}
35482 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35483 for more information.
35486 @anchor{swbreak stop reason}
35487 The packet indicates a memory breakpoint instruction was executed,
35488 irrespective of whether it was @value{GDBN} that planted the
35489 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35490 part must be left empty.
35492 On some architectures, such as x86, at the architecture level, when a
35493 breakpoint instruction executes the program counter points at the
35494 breakpoint address plus an offset. On such targets, the stub is
35495 responsible for adjusting the PC to point back at the breakpoint
35498 This packet should not be sent by default; older @value{GDBN} versions
35499 did not support it. @value{GDBN} requests it, by supplying an
35500 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35501 remote stub must also supply the appropriate @samp{qSupported} feature
35502 indicating support.
35504 This packet is required for correct non-stop mode operation.
35507 The packet indicates the target stopped for a hardware breakpoint.
35508 The @var{r} part must be left empty.
35510 The same remarks about @samp{qSupported} and non-stop mode above
35513 @cindex fork events, remote reply
35515 The packet indicates that @code{fork} was called, and @var{r}
35516 is the thread ID of the new child process. Refer to
35517 @ref{thread-id syntax} for the format of the @var{thread-id}
35518 field. This packet is only applicable to targets that support
35521 This packet should not be sent by default; older @value{GDBN} versions
35522 did not support it. @value{GDBN} requests it, by supplying an
35523 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35524 remote stub must also supply the appropriate @samp{qSupported} feature
35525 indicating support.
35527 @cindex vfork events, remote reply
35529 The packet indicates that @code{vfork} was called, and @var{r}
35530 is the thread ID of the new child process. Refer to
35531 @ref{thread-id syntax} for the format of the @var{thread-id}
35532 field. This packet is only applicable to targets that support
35535 This packet should not be sent by default; older @value{GDBN} versions
35536 did not support it. @value{GDBN} requests it, by supplying an
35537 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35538 remote stub must also supply the appropriate @samp{qSupported} feature
35539 indicating support.
35541 @cindex vforkdone events, remote reply
35543 The packet indicates that a child process created by a vfork
35544 has either called @code{exec} or terminated, so that the
35545 address spaces of the parent and child process are no longer
35546 shared. The @var{r} part is ignored. This packet is only
35547 applicable to targets that support vforkdone events.
35549 This packet should not be sent by default; older @value{GDBN} versions
35550 did not support it. @value{GDBN} requests it, by supplying an
35551 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35552 remote stub must also supply the appropriate @samp{qSupported} feature
35553 indicating support.
35555 @cindex exec events, remote reply
35557 The packet indicates that @code{execve} was called, and @var{r}
35558 is the absolute pathname of the file that was executed, in hex.
35559 This packet is only applicable to targets that support exec events.
35561 This packet should not be sent by default; older @value{GDBN} versions
35562 did not support it. @value{GDBN} requests it, by supplying an
35563 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35564 remote stub must also supply the appropriate @samp{qSupported} feature
35565 indicating support.
35567 @cindex thread create event, remote reply
35568 @anchor{thread create event}
35570 The packet indicates that the thread was just created. The new thread
35571 is stopped until @value{GDBN} sets it running with a resumption packet
35572 (@pxref{vCont packet}). This packet should not be sent by default;
35573 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
35574 also the @samp{w} (@ref{thread exit event}) remote reply below.
35579 @itemx W @var{AA} ; process:@var{pid}
35580 The process exited, and @var{AA} is the exit status. This is only
35581 applicable to certain targets.
35583 The second form of the response, including the process ID of the exited
35584 process, can be used only when @value{GDBN} has reported support for
35585 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35586 The @var{pid} is formatted as a big-endian hex string.
35589 @itemx X @var{AA} ; process:@var{pid}
35590 The process terminated with signal @var{AA}.
35592 The second form of the response, including the process ID of the
35593 terminated process, can be used only when @value{GDBN} has reported
35594 support for multiprocess protocol extensions; see @ref{multiprocess
35595 extensions}. The @var{pid} is formatted as a big-endian hex string.
35597 @anchor{thread exit event}
35598 @cindex thread exit event, remote reply
35599 @item w @var{AA} ; @var{tid}
35601 The thread exited, and @var{AA} is the exit status. This response
35602 should not be sent by default; @value{GDBN} requests it with the
35603 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
35606 There are no resumed threads left in the target. In other words, even
35607 though the process is alive, the last resumed thread has exited. For
35608 example, say the target process has two threads: thread 1 and thread
35609 2. The client leaves thread 1 stopped, and resumes thread 2, which
35610 subsequently exits. At this point, even though the process is still
35611 alive, and thus no @samp{W} stop reply is sent, no thread is actually
35612 executing either. The @samp{N} stop reply thus informs the client
35613 that it can stop waiting for stop replies. This packet should not be
35614 sent by default; older @value{GDBN} versions did not support it.
35615 @value{GDBN} requests it, by supplying an appropriate
35616 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
35617 also supply the appropriate @samp{qSupported} feature indicating
35620 @item O @var{XX}@dots{}
35621 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35622 written as the program's console output. This can happen at any time
35623 while the program is running and the debugger should continue to wait
35624 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35626 @item F @var{call-id},@var{parameter}@dots{}
35627 @var{call-id} is the identifier which says which host system call should
35628 be called. This is just the name of the function. Translation into the
35629 correct system call is only applicable as it's defined in @value{GDBN}.
35630 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35633 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35634 this very system call.
35636 The target replies with this packet when it expects @value{GDBN} to
35637 call a host system call on behalf of the target. @value{GDBN} replies
35638 with an appropriate @samp{F} packet and keeps up waiting for the next
35639 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35640 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35641 Protocol Extension}, for more details.
35645 @node General Query Packets
35646 @section General Query Packets
35647 @cindex remote query requests
35649 Packets starting with @samp{q} are @dfn{general query packets};
35650 packets starting with @samp{Q} are @dfn{general set packets}. General
35651 query and set packets are a semi-unified form for retrieving and
35652 sending information to and from the stub.
35654 The initial letter of a query or set packet is followed by a name
35655 indicating what sort of thing the packet applies to. For example,
35656 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35657 definitions with the stub. These packet names follow some
35662 The name must not contain commas, colons or semicolons.
35664 Most @value{GDBN} query and set packets have a leading upper case
35667 The names of custom vendor packets should use a company prefix, in
35668 lower case, followed by a period. For example, packets designed at
35669 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35670 foos) or @samp{Qacme.bar} (for setting bars).
35673 The name of a query or set packet should be separated from any
35674 parameters by a @samp{:}; the parameters themselves should be
35675 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35676 full packet name, and check for a separator or the end of the packet,
35677 in case two packet names share a common prefix. New packets should not begin
35678 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35679 packets predate these conventions, and have arguments without any terminator
35680 for the packet name; we suspect they are in widespread use in places that
35681 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35682 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35685 Like the descriptions of the other packets, each description here
35686 has a template showing the packet's overall syntax, followed by an
35687 explanation of the packet's meaning. We include spaces in some of the
35688 templates for clarity; these are not part of the packet's syntax. No
35689 @value{GDBN} packet uses spaces to separate its components.
35691 Here are the currently defined query and set packets:
35697 Turn on or off the agent as a helper to perform some debugging operations
35698 delegated from @value{GDBN} (@pxref{Control Agent}).
35700 @item QAllow:@var{op}:@var{val}@dots{}
35701 @cindex @samp{QAllow} packet
35702 Specify which operations @value{GDBN} expects to request of the
35703 target, as a semicolon-separated list of operation name and value
35704 pairs. Possible values for @var{op} include @samp{WriteReg},
35705 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35706 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35707 indicating that @value{GDBN} will not request the operation, or 1,
35708 indicating that it may. (The target can then use this to set up its
35709 own internals optimally, for instance if the debugger never expects to
35710 insert breakpoints, it may not need to install its own trap handler.)
35713 @cindex current thread, remote request
35714 @cindex @samp{qC} packet
35715 Return the current thread ID.
35719 @item QC @var{thread-id}
35720 Where @var{thread-id} is a thread ID as documented in
35721 @ref{thread-id syntax}.
35722 @item @r{(anything else)}
35723 Any other reply implies the old thread ID.
35726 @item qCRC:@var{addr},@var{length}
35727 @cindex CRC of memory block, remote request
35728 @cindex @samp{qCRC} packet
35729 @anchor{qCRC packet}
35730 Compute the CRC checksum of a block of memory using CRC-32 defined in
35731 IEEE 802.3. The CRC is computed byte at a time, taking the most
35732 significant bit of each byte first. The initial pattern code
35733 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35735 @emph{Note:} This is the same CRC used in validating separate debug
35736 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35737 Files}). However the algorithm is slightly different. When validating
35738 separate debug files, the CRC is computed taking the @emph{least}
35739 significant bit of each byte first, and the final result is inverted to
35740 detect trailing zeros.
35745 An error (such as memory fault)
35746 @item C @var{crc32}
35747 The specified memory region's checksum is @var{crc32}.
35750 @item QDisableRandomization:@var{value}
35751 @cindex disable address space randomization, remote request
35752 @cindex @samp{QDisableRandomization} packet
35753 Some target operating systems will randomize the virtual address space
35754 of the inferior process as a security feature, but provide a feature
35755 to disable such randomization, e.g.@: to allow for a more deterministic
35756 debugging experience. On such systems, this packet with a @var{value}
35757 of 1 directs the target to disable address space randomization for
35758 processes subsequently started via @samp{vRun} packets, while a packet
35759 with a @var{value} of 0 tells the target to enable address space
35762 This packet is only available in extended mode (@pxref{extended mode}).
35767 The request succeeded.
35770 An error occurred. The error number @var{nn} is given as hex digits.
35773 An empty reply indicates that @samp{QDisableRandomization} is not supported
35777 This packet is not probed by default; the remote stub must request it,
35778 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35779 This should only be done on targets that actually support disabling
35780 address space randomization.
35783 @itemx qsThreadInfo
35784 @cindex list active threads, remote request
35785 @cindex @samp{qfThreadInfo} packet
35786 @cindex @samp{qsThreadInfo} packet
35787 Obtain a list of all active thread IDs from the target (OS). Since there
35788 may be too many active threads to fit into one reply packet, this query
35789 works iteratively: it may require more than one query/reply sequence to
35790 obtain the entire list of threads. The first query of the sequence will
35791 be the @samp{qfThreadInfo} query; subsequent queries in the
35792 sequence will be the @samp{qsThreadInfo} query.
35794 NOTE: This packet replaces the @samp{qL} query (see below).
35798 @item m @var{thread-id}
35800 @item m @var{thread-id},@var{thread-id}@dots{}
35801 a comma-separated list of thread IDs
35803 (lower case letter @samp{L}) denotes end of list.
35806 In response to each query, the target will reply with a list of one or
35807 more thread IDs, separated by commas.
35808 @value{GDBN} will respond to each reply with a request for more thread
35809 ids (using the @samp{qs} form of the query), until the target responds
35810 with @samp{l} (lower-case ell, for @dfn{last}).
35811 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35814 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
35815 initial connection with the remote target, and the very first thread ID
35816 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
35817 message. Therefore, the stub should ensure that the first thread ID in
35818 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
35820 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35821 @cindex get thread-local storage address, remote request
35822 @cindex @samp{qGetTLSAddr} packet
35823 Fetch the address associated with thread local storage specified
35824 by @var{thread-id}, @var{offset}, and @var{lm}.
35826 @var{thread-id} is the thread ID associated with the
35827 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35829 @var{offset} is the (big endian, hex encoded) offset associated with the
35830 thread local variable. (This offset is obtained from the debug
35831 information associated with the variable.)
35833 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35834 load module associated with the thread local storage. For example,
35835 a @sc{gnu}/Linux system will pass the link map address of the shared
35836 object associated with the thread local storage under consideration.
35837 Other operating environments may choose to represent the load module
35838 differently, so the precise meaning of this parameter will vary.
35842 @item @var{XX}@dots{}
35843 Hex encoded (big endian) bytes representing the address of the thread
35844 local storage requested.
35847 An error occurred. The error number @var{nn} is given as hex digits.
35850 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35853 @item qGetTIBAddr:@var{thread-id}
35854 @cindex get thread information block address
35855 @cindex @samp{qGetTIBAddr} packet
35856 Fetch address of the Windows OS specific Thread Information Block.
35858 @var{thread-id} is the thread ID associated with the thread.
35862 @item @var{XX}@dots{}
35863 Hex encoded (big endian) bytes representing the linear address of the
35864 thread information block.
35867 An error occured. This means that either the thread was not found, or the
35868 address could not be retrieved.
35871 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35874 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35875 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35876 digit) is one to indicate the first query and zero to indicate a
35877 subsequent query; @var{threadcount} (two hex digits) is the maximum
35878 number of threads the response packet can contain; and @var{nextthread}
35879 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35880 returned in the response as @var{argthread}.
35882 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35886 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35887 Where: @var{count} (two hex digits) is the number of threads being
35888 returned; @var{done} (one hex digit) is zero to indicate more threads
35889 and one indicates no further threads; @var{argthreadid} (eight hex
35890 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35891 is a sequence of thread IDs, @var{threadid} (eight hex
35892 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
35896 @cindex section offsets, remote request
35897 @cindex @samp{qOffsets} packet
35898 Get section offsets that the target used when relocating the downloaded
35903 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35904 Relocate the @code{Text} section by @var{xxx} from its original address.
35905 Relocate the @code{Data} section by @var{yyy} from its original address.
35906 If the object file format provides segment information (e.g.@: @sc{elf}
35907 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35908 segments by the supplied offsets.
35910 @emph{Note: while a @code{Bss} offset may be included in the response,
35911 @value{GDBN} ignores this and instead applies the @code{Data} offset
35912 to the @code{Bss} section.}
35914 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35915 Relocate the first segment of the object file, which conventionally
35916 contains program code, to a starting address of @var{xxx}. If
35917 @samp{DataSeg} is specified, relocate the second segment, which
35918 conventionally contains modifiable data, to a starting address of
35919 @var{yyy}. @value{GDBN} will report an error if the object file
35920 does not contain segment information, or does not contain at least
35921 as many segments as mentioned in the reply. Extra segments are
35922 kept at fixed offsets relative to the last relocated segment.
35925 @item qP @var{mode} @var{thread-id}
35926 @cindex thread information, remote request
35927 @cindex @samp{qP} packet
35928 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35929 encoded 32 bit mode; @var{thread-id} is a thread ID
35930 (@pxref{thread-id syntax}).
35932 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35935 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35939 @cindex non-stop mode, remote request
35940 @cindex @samp{QNonStop} packet
35942 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35943 @xref{Remote Non-Stop}, for more information.
35948 The request succeeded.
35951 An error occurred. The error number @var{nn} is given as hex digits.
35954 An empty reply indicates that @samp{QNonStop} is not supported by
35958 This packet is not probed by default; the remote stub must request it,
35959 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35960 Use of this packet is controlled by the @code{set non-stop} command;
35961 @pxref{Non-Stop Mode}.
35963 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35964 @cindex pass signals to inferior, remote request
35965 @cindex @samp{QPassSignals} packet
35966 @anchor{QPassSignals}
35967 Each listed @var{signal} should be passed directly to the inferior process.
35968 Signals are numbered identically to continue packets and stop replies
35969 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35970 strictly greater than the previous item. These signals do not need to stop
35971 the inferior, or be reported to @value{GDBN}. All other signals should be
35972 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35973 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35974 new list. This packet improves performance when using @samp{handle
35975 @var{signal} nostop noprint pass}.
35980 The request succeeded.
35983 An error occurred. The error number @var{nn} is given as hex digits.
35986 An empty reply indicates that @samp{QPassSignals} is not supported by
35990 Use of this packet is controlled by the @code{set remote pass-signals}
35991 command (@pxref{Remote Configuration, set remote pass-signals}).
35992 This packet is not probed by default; the remote stub must request it,
35993 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35995 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35996 @cindex signals the inferior may see, remote request
35997 @cindex @samp{QProgramSignals} packet
35998 @anchor{QProgramSignals}
35999 Each listed @var{signal} may be delivered to the inferior process.
36000 Others should be silently discarded.
36002 In some cases, the remote stub may need to decide whether to deliver a
36003 signal to the program or not without @value{GDBN} involvement. One
36004 example of that is while detaching --- the program's threads may have
36005 stopped for signals that haven't yet had a chance of being reported to
36006 @value{GDBN}, and so the remote stub can use the signal list specified
36007 by this packet to know whether to deliver or ignore those pending
36010 This does not influence whether to deliver a signal as requested by a
36011 resumption packet (@pxref{vCont packet}).
36013 Signals are numbered identically to continue packets and stop replies
36014 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36015 strictly greater than the previous item. Multiple
36016 @samp{QProgramSignals} packets do not combine; any earlier
36017 @samp{QProgramSignals} list is completely replaced by the new list.
36022 The request succeeded.
36025 An error occurred. The error number @var{nn} is given as hex digits.
36028 An empty reply indicates that @samp{QProgramSignals} is not supported
36032 Use of this packet is controlled by the @code{set remote program-signals}
36033 command (@pxref{Remote Configuration, set remote program-signals}).
36034 This packet is not probed by default; the remote stub must request it,
36035 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36037 @anchor{QThreadEvents}
36038 @item QThreadEvents:1
36039 @itemx QThreadEvents:0
36040 @cindex thread create/exit events, remote request
36041 @cindex @samp{QThreadEvents} packet
36043 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
36044 reporting of thread create and exit events. @xref{thread create
36045 event}, for the reply specifications. For example, this is used in
36046 non-stop mode when @value{GDBN} stops a set of threads and
36047 synchronously waits for the their corresponding stop replies. Without
36048 exit events, if one of the threads exits, @value{GDBN} would hang
36049 forever not knowing that it should no longer expect a stop for that
36050 same thread. @value{GDBN} does not enable this feature unless the
36051 stub reports that it supports it by including @samp{QThreadEvents+} in
36052 its @samp{qSupported} reply.
36057 The request succeeded.
36060 An error occurred. The error number @var{nn} is given as hex digits.
36063 An empty reply indicates that @samp{QThreadEvents} is not supported by
36067 Use of this packet is controlled by the @code{set remote thread-events}
36068 command (@pxref{Remote Configuration, set remote thread-events}).
36070 @item qRcmd,@var{command}
36071 @cindex execute remote command, remote request
36072 @cindex @samp{qRcmd} packet
36073 @var{command} (hex encoded) is passed to the local interpreter for
36074 execution. Invalid commands should be reported using the output
36075 string. Before the final result packet, the target may also respond
36076 with a number of intermediate @samp{O@var{output}} console output
36077 packets. @emph{Implementors should note that providing access to a
36078 stubs's interpreter may have security implications}.
36083 A command response with no output.
36085 A command response with the hex encoded output string @var{OUTPUT}.
36087 Indicate a badly formed request.
36089 An empty reply indicates that @samp{qRcmd} is not recognized.
36092 (Note that the @code{qRcmd} packet's name is separated from the
36093 command by a @samp{,}, not a @samp{:}, contrary to the naming
36094 conventions above. Please don't use this packet as a model for new
36097 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36098 @cindex searching memory, in remote debugging
36100 @cindex @samp{qSearch:memory} packet
36102 @cindex @samp{qSearch memory} packet
36103 @anchor{qSearch memory}
36104 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36105 Both @var{address} and @var{length} are encoded in hex;
36106 @var{search-pattern} is a sequence of bytes, also hex encoded.
36111 The pattern was not found.
36113 The pattern was found at @var{address}.
36115 A badly formed request or an error was encountered while searching memory.
36117 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36120 @item QStartNoAckMode
36121 @cindex @samp{QStartNoAckMode} packet
36122 @anchor{QStartNoAckMode}
36123 Request that the remote stub disable the normal @samp{+}/@samp{-}
36124 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36129 The stub has switched to no-acknowledgment mode.
36130 @value{GDBN} acknowledges this reponse,
36131 but neither the stub nor @value{GDBN} shall send or expect further
36132 @samp{+}/@samp{-} acknowledgments in the current connection.
36134 An empty reply indicates that the stub does not support no-acknowledgment mode.
36137 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36138 @cindex supported packets, remote query
36139 @cindex features of the remote protocol
36140 @cindex @samp{qSupported} packet
36141 @anchor{qSupported}
36142 Tell the remote stub about features supported by @value{GDBN}, and
36143 query the stub for features it supports. This packet allows
36144 @value{GDBN} and the remote stub to take advantage of each others'
36145 features. @samp{qSupported} also consolidates multiple feature probes
36146 at startup, to improve @value{GDBN} performance---a single larger
36147 packet performs better than multiple smaller probe packets on
36148 high-latency links. Some features may enable behavior which must not
36149 be on by default, e.g.@: because it would confuse older clients or
36150 stubs. Other features may describe packets which could be
36151 automatically probed for, but are not. These features must be
36152 reported before @value{GDBN} will use them. This ``default
36153 unsupported'' behavior is not appropriate for all packets, but it
36154 helps to keep the initial connection time under control with new
36155 versions of @value{GDBN} which support increasing numbers of packets.
36159 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36160 The stub supports or does not support each returned @var{stubfeature},
36161 depending on the form of each @var{stubfeature} (see below for the
36164 An empty reply indicates that @samp{qSupported} is not recognized,
36165 or that no features needed to be reported to @value{GDBN}.
36168 The allowed forms for each feature (either a @var{gdbfeature} in the
36169 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36173 @item @var{name}=@var{value}
36174 The remote protocol feature @var{name} is supported, and associated
36175 with the specified @var{value}. The format of @var{value} depends
36176 on the feature, but it must not include a semicolon.
36178 The remote protocol feature @var{name} is supported, and does not
36179 need an associated value.
36181 The remote protocol feature @var{name} is not supported.
36183 The remote protocol feature @var{name} may be supported, and
36184 @value{GDBN} should auto-detect support in some other way when it is
36185 needed. This form will not be used for @var{gdbfeature} notifications,
36186 but may be used for @var{stubfeature} responses.
36189 Whenever the stub receives a @samp{qSupported} request, the
36190 supplied set of @value{GDBN} features should override any previous
36191 request. This allows @value{GDBN} to put the stub in a known
36192 state, even if the stub had previously been communicating with
36193 a different version of @value{GDBN}.
36195 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36200 This feature indicates whether @value{GDBN} supports multiprocess
36201 extensions to the remote protocol. @value{GDBN} does not use such
36202 extensions unless the stub also reports that it supports them by
36203 including @samp{multiprocess+} in its @samp{qSupported} reply.
36204 @xref{multiprocess extensions}, for details.
36207 This feature indicates that @value{GDBN} supports the XML target
36208 description. If the stub sees @samp{xmlRegisters=} with target
36209 specific strings separated by a comma, it will report register
36213 This feature indicates whether @value{GDBN} supports the
36214 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36215 instruction reply packet}).
36218 This feature indicates whether @value{GDBN} supports the swbreak stop
36219 reason in stop replies. @xref{swbreak stop reason}, for details.
36222 This feature indicates whether @value{GDBN} supports the hwbreak stop
36223 reason in stop replies. @xref{swbreak stop reason}, for details.
36226 This feature indicates whether @value{GDBN} supports fork event
36227 extensions to the remote protocol. @value{GDBN} does not use such
36228 extensions unless the stub also reports that it supports them by
36229 including @samp{fork-events+} in its @samp{qSupported} reply.
36232 This feature indicates whether @value{GDBN} supports vfork event
36233 extensions to the remote protocol. @value{GDBN} does not use such
36234 extensions unless the stub also reports that it supports them by
36235 including @samp{vfork-events+} in its @samp{qSupported} reply.
36238 This feature indicates whether @value{GDBN} supports exec event
36239 extensions to the remote protocol. @value{GDBN} does not use such
36240 extensions unless the stub also reports that it supports them by
36241 including @samp{exec-events+} in its @samp{qSupported} reply.
36243 @item vContSupported
36244 This feature indicates whether @value{GDBN} wants to know the
36245 supported actions in the reply to @samp{vCont?} packet.
36248 Stubs should ignore any unknown values for
36249 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36250 packet supports receiving packets of unlimited length (earlier
36251 versions of @value{GDBN} may reject overly long responses). Additional values
36252 for @var{gdbfeature} may be defined in the future to let the stub take
36253 advantage of new features in @value{GDBN}, e.g.@: incompatible
36254 improvements in the remote protocol---the @samp{multiprocess} feature is
36255 an example of such a feature. The stub's reply should be independent
36256 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36257 describes all the features it supports, and then the stub replies with
36258 all the features it supports.
36260 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36261 responses, as long as each response uses one of the standard forms.
36263 Some features are flags. A stub which supports a flag feature
36264 should respond with a @samp{+} form response. Other features
36265 require values, and the stub should respond with an @samp{=}
36268 Each feature has a default value, which @value{GDBN} will use if
36269 @samp{qSupported} is not available or if the feature is not mentioned
36270 in the @samp{qSupported} response. The default values are fixed; a
36271 stub is free to omit any feature responses that match the defaults.
36273 Not all features can be probed, but for those which can, the probing
36274 mechanism is useful: in some cases, a stub's internal
36275 architecture may not allow the protocol layer to know some information
36276 about the underlying target in advance. This is especially common in
36277 stubs which may be configured for multiple targets.
36279 These are the currently defined stub features and their properties:
36281 @multitable @columnfractions 0.35 0.2 0.12 0.2
36282 @c NOTE: The first row should be @headitem, but we do not yet require
36283 @c a new enough version of Texinfo (4.7) to use @headitem.
36285 @tab Value Required
36289 @item @samp{PacketSize}
36294 @item @samp{qXfer:auxv:read}
36299 @item @samp{qXfer:btrace:read}
36304 @item @samp{qXfer:btrace-conf:read}
36309 @item @samp{qXfer:exec-file:read}
36314 @item @samp{qXfer:features:read}
36319 @item @samp{qXfer:libraries:read}
36324 @item @samp{qXfer:libraries-svr4:read}
36329 @item @samp{augmented-libraries-svr4-read}
36334 @item @samp{qXfer:memory-map:read}
36339 @item @samp{qXfer:sdata:read}
36344 @item @samp{qXfer:spu:read}
36349 @item @samp{qXfer:spu:write}
36354 @item @samp{qXfer:siginfo:read}
36359 @item @samp{qXfer:siginfo:write}
36364 @item @samp{qXfer:threads:read}
36369 @item @samp{qXfer:traceframe-info:read}
36374 @item @samp{qXfer:uib:read}
36379 @item @samp{qXfer:fdpic:read}
36384 @item @samp{Qbtrace:off}
36389 @item @samp{Qbtrace:bts}
36394 @item @samp{Qbtrace:pt}
36399 @item @samp{Qbtrace-conf:bts:size}
36404 @item @samp{Qbtrace-conf:pt:size}
36409 @item @samp{QNonStop}
36414 @item @samp{QPassSignals}
36419 @item @samp{QStartNoAckMode}
36424 @item @samp{multiprocess}
36429 @item @samp{ConditionalBreakpoints}
36434 @item @samp{ConditionalTracepoints}
36439 @item @samp{ReverseContinue}
36444 @item @samp{ReverseStep}
36449 @item @samp{TracepointSource}
36454 @item @samp{QAgent}
36459 @item @samp{QAllow}
36464 @item @samp{QDisableRandomization}
36469 @item @samp{EnableDisableTracepoints}
36474 @item @samp{QTBuffer:size}
36479 @item @samp{tracenz}
36484 @item @samp{BreakpointCommands}
36489 @item @samp{swbreak}
36494 @item @samp{hwbreak}
36499 @item @samp{fork-events}
36504 @item @samp{vfork-events}
36509 @item @samp{exec-events}
36514 @item @samp{QThreadEvents}
36519 @item @samp{no-resumed}
36526 These are the currently defined stub features, in more detail:
36529 @cindex packet size, remote protocol
36530 @item PacketSize=@var{bytes}
36531 The remote stub can accept packets up to at least @var{bytes} in
36532 length. @value{GDBN} will send packets up to this size for bulk
36533 transfers, and will never send larger packets. This is a limit on the
36534 data characters in the packet, including the frame and checksum.
36535 There is no trailing NUL byte in a remote protocol packet; if the stub
36536 stores packets in a NUL-terminated format, it should allow an extra
36537 byte in its buffer for the NUL. If this stub feature is not supported,
36538 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36540 @item qXfer:auxv:read
36541 The remote stub understands the @samp{qXfer:auxv:read} packet
36542 (@pxref{qXfer auxiliary vector read}).
36544 @item qXfer:btrace:read
36545 The remote stub understands the @samp{qXfer:btrace:read}
36546 packet (@pxref{qXfer btrace read}).
36548 @item qXfer:btrace-conf:read
36549 The remote stub understands the @samp{qXfer:btrace-conf:read}
36550 packet (@pxref{qXfer btrace-conf read}).
36552 @item qXfer:exec-file:read
36553 The remote stub understands the @samp{qXfer:exec-file:read} packet
36554 (@pxref{qXfer executable filename read}).
36556 @item qXfer:features:read
36557 The remote stub understands the @samp{qXfer:features:read} packet
36558 (@pxref{qXfer target description read}).
36560 @item qXfer:libraries:read
36561 The remote stub understands the @samp{qXfer:libraries:read} packet
36562 (@pxref{qXfer library list read}).
36564 @item qXfer:libraries-svr4:read
36565 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36566 (@pxref{qXfer svr4 library list read}).
36568 @item augmented-libraries-svr4-read
36569 The remote stub understands the augmented form of the
36570 @samp{qXfer:libraries-svr4:read} packet
36571 (@pxref{qXfer svr4 library list read}).
36573 @item qXfer:memory-map:read
36574 The remote stub understands the @samp{qXfer:memory-map:read} packet
36575 (@pxref{qXfer memory map read}).
36577 @item qXfer:sdata:read
36578 The remote stub understands the @samp{qXfer:sdata:read} packet
36579 (@pxref{qXfer sdata read}).
36581 @item qXfer:spu:read
36582 The remote stub understands the @samp{qXfer:spu:read} packet
36583 (@pxref{qXfer spu read}).
36585 @item qXfer:spu:write
36586 The remote stub understands the @samp{qXfer:spu:write} packet
36587 (@pxref{qXfer spu write}).
36589 @item qXfer:siginfo:read
36590 The remote stub understands the @samp{qXfer:siginfo:read} packet
36591 (@pxref{qXfer siginfo read}).
36593 @item qXfer:siginfo:write
36594 The remote stub understands the @samp{qXfer:siginfo:write} packet
36595 (@pxref{qXfer siginfo write}).
36597 @item qXfer:threads:read
36598 The remote stub understands the @samp{qXfer:threads:read} packet
36599 (@pxref{qXfer threads read}).
36601 @item qXfer:traceframe-info:read
36602 The remote stub understands the @samp{qXfer:traceframe-info:read}
36603 packet (@pxref{qXfer traceframe info read}).
36605 @item qXfer:uib:read
36606 The remote stub understands the @samp{qXfer:uib:read}
36607 packet (@pxref{qXfer unwind info block}).
36609 @item qXfer:fdpic:read
36610 The remote stub understands the @samp{qXfer:fdpic:read}
36611 packet (@pxref{qXfer fdpic loadmap read}).
36614 The remote stub understands the @samp{QNonStop} packet
36615 (@pxref{QNonStop}).
36618 The remote stub understands the @samp{QPassSignals} packet
36619 (@pxref{QPassSignals}).
36621 @item QStartNoAckMode
36622 The remote stub understands the @samp{QStartNoAckMode} packet and
36623 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36626 @anchor{multiprocess extensions}
36627 @cindex multiprocess extensions, in remote protocol
36628 The remote stub understands the multiprocess extensions to the remote
36629 protocol syntax. The multiprocess extensions affect the syntax of
36630 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36631 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36632 replies. Note that reporting this feature indicates support for the
36633 syntactic extensions only, not that the stub necessarily supports
36634 debugging of more than one process at a time. The stub must not use
36635 multiprocess extensions in packet replies unless @value{GDBN} has also
36636 indicated it supports them in its @samp{qSupported} request.
36638 @item qXfer:osdata:read
36639 The remote stub understands the @samp{qXfer:osdata:read} packet
36640 ((@pxref{qXfer osdata read}).
36642 @item ConditionalBreakpoints
36643 The target accepts and implements evaluation of conditional expressions
36644 defined for breakpoints. The target will only report breakpoint triggers
36645 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36647 @item ConditionalTracepoints
36648 The remote stub accepts and implements conditional expressions defined
36649 for tracepoints (@pxref{Tracepoint Conditions}).
36651 @item ReverseContinue
36652 The remote stub accepts and implements the reverse continue packet
36656 The remote stub accepts and implements the reverse step packet
36659 @item TracepointSource
36660 The remote stub understands the @samp{QTDPsrc} packet that supplies
36661 the source form of tracepoint definitions.
36664 The remote stub understands the @samp{QAgent} packet.
36667 The remote stub understands the @samp{QAllow} packet.
36669 @item QDisableRandomization
36670 The remote stub understands the @samp{QDisableRandomization} packet.
36672 @item StaticTracepoint
36673 @cindex static tracepoints, in remote protocol
36674 The remote stub supports static tracepoints.
36676 @item InstallInTrace
36677 @anchor{install tracepoint in tracing}
36678 The remote stub supports installing tracepoint in tracing.
36680 @item EnableDisableTracepoints
36681 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36682 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36683 to be enabled and disabled while a trace experiment is running.
36685 @item QTBuffer:size
36686 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
36687 packet that allows to change the size of the trace buffer.
36690 @cindex string tracing, in remote protocol
36691 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36692 See @ref{Bytecode Descriptions} for details about the bytecode.
36694 @item BreakpointCommands
36695 @cindex breakpoint commands, in remote protocol
36696 The remote stub supports running a breakpoint's command list itself,
36697 rather than reporting the hit to @value{GDBN}.
36700 The remote stub understands the @samp{Qbtrace:off} packet.
36703 The remote stub understands the @samp{Qbtrace:bts} packet.
36706 The remote stub understands the @samp{Qbtrace:pt} packet.
36708 @item Qbtrace-conf:bts:size
36709 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
36711 @item Qbtrace-conf:pt:size
36712 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
36715 The remote stub reports the @samp{swbreak} stop reason for memory
36719 The remote stub reports the @samp{hwbreak} stop reason for hardware
36723 The remote stub reports the @samp{fork} stop reason for fork events.
36726 The remote stub reports the @samp{vfork} stop reason for vfork events
36727 and vforkdone events.
36730 The remote stub reports the @samp{exec} stop reason for exec events.
36732 @item vContSupported
36733 The remote stub reports the supported actions in the reply to
36734 @samp{vCont?} packet.
36736 @item QThreadEvents
36737 The remote stub understands the @samp{QThreadEvents} packet.
36740 The remote stub reports the @samp{N} stop reply.
36745 @cindex symbol lookup, remote request
36746 @cindex @samp{qSymbol} packet
36747 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36748 requests. Accept requests from the target for the values of symbols.
36753 The target does not need to look up any (more) symbols.
36754 @item qSymbol:@var{sym_name}
36755 The target requests the value of symbol @var{sym_name} (hex encoded).
36756 @value{GDBN} may provide the value by using the
36757 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36761 @item qSymbol:@var{sym_value}:@var{sym_name}
36762 Set the value of @var{sym_name} to @var{sym_value}.
36764 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36765 target has previously requested.
36767 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36768 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36774 The target does not need to look up any (more) symbols.
36775 @item qSymbol:@var{sym_name}
36776 The target requests the value of a new symbol @var{sym_name} (hex
36777 encoded). @value{GDBN} will continue to supply the values of symbols
36778 (if available), until the target ceases to request them.
36783 @itemx QTDisconnected
36790 @itemx qTMinFTPILen
36792 @xref{Tracepoint Packets}.
36794 @item qThreadExtraInfo,@var{thread-id}
36795 @cindex thread attributes info, remote request
36796 @cindex @samp{qThreadExtraInfo} packet
36797 Obtain from the target OS a printable string description of thread
36798 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
36799 for the forms of @var{thread-id}. This
36800 string may contain anything that the target OS thinks is interesting
36801 for @value{GDBN} to tell the user about the thread. The string is
36802 displayed in @value{GDBN}'s @code{info threads} display. Some
36803 examples of possible thread extra info strings are @samp{Runnable}, or
36804 @samp{Blocked on Mutex}.
36808 @item @var{XX}@dots{}
36809 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36810 comprising the printable string containing the extra information about
36811 the thread's attributes.
36814 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36815 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36816 conventions above. Please don't use this packet as a model for new
36835 @xref{Tracepoint Packets}.
36837 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36838 @cindex read special object, remote request
36839 @cindex @samp{qXfer} packet
36840 @anchor{qXfer read}
36841 Read uninterpreted bytes from the target's special data area
36842 identified by the keyword @var{object}. Request @var{length} bytes
36843 starting at @var{offset} bytes into the data. The content and
36844 encoding of @var{annex} is specific to @var{object}; it can supply
36845 additional details about what data to access.
36847 Here are the specific requests of this form defined so far. All
36848 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36849 formats, listed below.
36852 @item qXfer:auxv:read::@var{offset},@var{length}
36853 @anchor{qXfer auxiliary vector read}
36854 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36855 auxiliary vector}. Note @var{annex} must be empty.
36857 This packet is not probed by default; the remote stub must request it,
36858 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36860 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
36861 @anchor{qXfer btrace read}
36863 Return a description of the current branch trace.
36864 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
36865 packet may have one of the following values:
36869 Returns all available branch trace.
36872 Returns all available branch trace if the branch trace changed since
36873 the last read request.
36876 Returns the new branch trace since the last read request. Adds a new
36877 block to the end of the trace that begins at zero and ends at the source
36878 location of the first branch in the trace buffer. This extra block is
36879 used to stitch traces together.
36881 If the trace buffer overflowed, returns an error indicating the overflow.
36884 This packet is not probed by default; the remote stub must request it
36885 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36887 @item qXfer:btrace-conf:read::@var{offset},@var{length}
36888 @anchor{qXfer btrace-conf read}
36890 Return a description of the current branch trace configuration.
36891 @xref{Branch Trace Configuration Format}.
36893 This packet is not probed by default; the remote stub must request it
36894 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36896 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
36897 @anchor{qXfer executable filename read}
36898 Return the full absolute name of the file that was executed to create
36899 a process running on the remote system. The annex specifies the
36900 numeric process ID of the process to query, encoded as a hexadecimal
36901 number. If the annex part is empty the remote stub should return the
36902 filename corresponding to the currently executing process.
36904 This packet is not probed by default; the remote stub must request it,
36905 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36907 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36908 @anchor{qXfer target description read}
36909 Access the @dfn{target description}. @xref{Target Descriptions}. The
36910 annex specifies which XML document to access. The main description is
36911 always loaded from the @samp{target.xml} annex.
36913 This packet is not probed by default; the remote stub must request it,
36914 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36916 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36917 @anchor{qXfer library list read}
36918 Access the target's list of loaded libraries. @xref{Library List Format}.
36919 The annex part of the generic @samp{qXfer} packet must be empty
36920 (@pxref{qXfer read}).
36922 Targets which maintain a list of libraries in the program's memory do
36923 not need to implement this packet; it is designed for platforms where
36924 the operating system manages the list of loaded libraries.
36926 This packet is not probed by default; the remote stub must request it,
36927 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36929 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36930 @anchor{qXfer svr4 library list read}
36931 Access the target's list of loaded libraries when the target is an SVR4
36932 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36933 of the generic @samp{qXfer} packet must be empty unless the remote
36934 stub indicated it supports the augmented form of this packet
36935 by supplying an appropriate @samp{qSupported} response
36936 (@pxref{qXfer read}, @ref{qSupported}).
36938 This packet is optional for better performance on SVR4 targets.
36939 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36941 This packet is not probed by default; the remote stub must request it,
36942 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36944 If the remote stub indicates it supports the augmented form of this
36945 packet then the annex part of the generic @samp{qXfer} packet may
36946 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
36947 arguments. The currently supported arguments are:
36950 @item start=@var{address}
36951 A hexadecimal number specifying the address of the @samp{struct
36952 link_map} to start reading the library list from. If unset or zero
36953 then the first @samp{struct link_map} in the library list will be
36954 chosen as the starting point.
36956 @item prev=@var{address}
36957 A hexadecimal number specifying the address of the @samp{struct
36958 link_map} immediately preceding the @samp{struct link_map}
36959 specified by the @samp{start} argument. If unset or zero then
36960 the remote stub will expect that no @samp{struct link_map}
36961 exists prior to the starting point.
36965 Arguments that are not understood by the remote stub will be silently
36968 @item qXfer:memory-map:read::@var{offset},@var{length}
36969 @anchor{qXfer memory map read}
36970 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
36971 annex part of the generic @samp{qXfer} packet must be empty
36972 (@pxref{qXfer read}).
36974 This packet is not probed by default; the remote stub must request it,
36975 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36977 @item qXfer:sdata:read::@var{offset},@var{length}
36978 @anchor{qXfer sdata read}
36980 Read contents of the extra collected static tracepoint marker
36981 information. The annex part of the generic @samp{qXfer} packet must
36982 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
36985 This packet is not probed by default; the remote stub must request it,
36986 by supplying an appropriate @samp{qSupported} response
36987 (@pxref{qSupported}).
36989 @item qXfer:siginfo:read::@var{offset},@var{length}
36990 @anchor{qXfer siginfo read}
36991 Read contents of the extra signal information on the target
36992 system. The annex part of the generic @samp{qXfer} packet must be
36993 empty (@pxref{qXfer read}).
36995 This packet is not probed by default; the remote stub must request it,
36996 by supplying an appropriate @samp{qSupported} response
36997 (@pxref{qSupported}).
36999 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37000 @anchor{qXfer spu read}
37001 Read contents of an @code{spufs} file on the target system. The
37002 annex specifies which file to read; it must be of the form
37003 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37004 in the target process, and @var{name} identifes the @code{spufs} file
37005 in that context to be accessed.
37007 This packet is not probed by default; the remote stub must request it,
37008 by supplying an appropriate @samp{qSupported} response
37009 (@pxref{qSupported}).
37011 @item qXfer:threads:read::@var{offset},@var{length}
37012 @anchor{qXfer threads read}
37013 Access the list of threads on target. @xref{Thread List Format}. The
37014 annex part of the generic @samp{qXfer} packet must be empty
37015 (@pxref{qXfer read}).
37017 This packet is not probed by default; the remote stub must request it,
37018 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37020 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37021 @anchor{qXfer traceframe info read}
37023 Return a description of the current traceframe's contents.
37024 @xref{Traceframe Info Format}. The annex part of the generic
37025 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37027 This packet is not probed by default; the remote stub must request it,
37028 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37030 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37031 @anchor{qXfer unwind info block}
37033 Return the unwind information block for @var{pc}. This packet is used
37034 on OpenVMS/ia64 to ask the kernel unwind information.
37036 This packet is not probed by default.
37038 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37039 @anchor{qXfer fdpic loadmap read}
37040 Read contents of @code{loadmap}s on the target system. The
37041 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37042 executable @code{loadmap} or interpreter @code{loadmap} to read.
37044 This packet is not probed by default; the remote stub must request it,
37045 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37047 @item qXfer:osdata:read::@var{offset},@var{length}
37048 @anchor{qXfer osdata read}
37049 Access the target's @dfn{operating system information}.
37050 @xref{Operating System Information}.
37057 Data @var{data} (@pxref{Binary Data}) has been read from the
37058 target. There may be more data at a higher address (although
37059 it is permitted to return @samp{m} even for the last valid
37060 block of data, as long as at least one byte of data was read).
37061 It is possible for @var{data} to have fewer bytes than the @var{length} in the
37065 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37066 There is no more data to be read. It is possible for @var{data} to
37067 have fewer bytes than the @var{length} in the request.
37070 The @var{offset} in the request is at the end of the data.
37071 There is no more data to be read.
37074 The request was malformed, or @var{annex} was invalid.
37077 The offset was invalid, or there was an error encountered reading the data.
37078 The @var{nn} part is a hex-encoded @code{errno} value.
37081 An empty reply indicates the @var{object} string was not recognized by
37082 the stub, or that the object does not support reading.
37085 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37086 @cindex write data into object, remote request
37087 @anchor{qXfer write}
37088 Write uninterpreted bytes into the target's special data area
37089 identified by the keyword @var{object}, starting at @var{offset} bytes
37090 into the data. The binary-encoded data (@pxref{Binary Data}) to be
37091 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
37092 is specific to @var{object}; it can supply additional details about what data
37095 Here are the specific requests of this form defined so far. All
37096 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37097 formats, listed below.
37100 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37101 @anchor{qXfer siginfo write}
37102 Write @var{data} to the extra signal information on the target system.
37103 The annex part of the generic @samp{qXfer} packet must be
37104 empty (@pxref{qXfer write}).
37106 This packet is not probed by default; the remote stub must request it,
37107 by supplying an appropriate @samp{qSupported} response
37108 (@pxref{qSupported}).
37110 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37111 @anchor{qXfer spu write}
37112 Write @var{data} to an @code{spufs} file on the target system. The
37113 annex specifies which file to write; it must be of the form
37114 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37115 in the target process, and @var{name} identifes the @code{spufs} file
37116 in that context to be accessed.
37118 This packet is not probed by default; the remote stub must request it,
37119 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37125 @var{nn} (hex encoded) is the number of bytes written.
37126 This may be fewer bytes than supplied in the request.
37129 The request was malformed, or @var{annex} was invalid.
37132 The offset was invalid, or there was an error encountered writing the data.
37133 The @var{nn} part is a hex-encoded @code{errno} value.
37136 An empty reply indicates the @var{object} string was not
37137 recognized by the stub, or that the object does not support writing.
37140 @item qXfer:@var{object}:@var{operation}:@dots{}
37141 Requests of this form may be added in the future. When a stub does
37142 not recognize the @var{object} keyword, or its support for
37143 @var{object} does not recognize the @var{operation} keyword, the stub
37144 must respond with an empty packet.
37146 @item qAttached:@var{pid}
37147 @cindex query attached, remote request
37148 @cindex @samp{qAttached} packet
37149 Return an indication of whether the remote server attached to an
37150 existing process or created a new process. When the multiprocess
37151 protocol extensions are supported (@pxref{multiprocess extensions}),
37152 @var{pid} is an integer in hexadecimal format identifying the target
37153 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37154 the query packet will be simplified as @samp{qAttached}.
37156 This query is used, for example, to know whether the remote process
37157 should be detached or killed when a @value{GDBN} session is ended with
37158 the @code{quit} command.
37163 The remote server attached to an existing process.
37165 The remote server created a new process.
37167 A badly formed request or an error was encountered.
37171 Enable branch tracing for the current thread using Branch Trace Store.
37176 Branch tracing has been enabled.
37178 A badly formed request or an error was encountered.
37182 Enable branch tracing for the current thread using Intel(R) Processor Trace.
37187 Branch tracing has been enabled.
37189 A badly formed request or an error was encountered.
37193 Disable branch tracing for the current thread.
37198 Branch tracing has been disabled.
37200 A badly formed request or an error was encountered.
37203 @item Qbtrace-conf:bts:size=@var{value}
37204 Set the requested ring buffer size for new threads that use the
37205 btrace recording method in bts format.
37210 The ring buffer size has been set.
37212 A badly formed request or an error was encountered.
37215 @item Qbtrace-conf:pt:size=@var{value}
37216 Set the requested ring buffer size for new threads that use the
37217 btrace recording method in pt format.
37222 The ring buffer size has been set.
37224 A badly formed request or an error was encountered.
37229 @node Architecture-Specific Protocol Details
37230 @section Architecture-Specific Protocol Details
37232 This section describes how the remote protocol is applied to specific
37233 target architectures. Also see @ref{Standard Target Features}, for
37234 details of XML target descriptions for each architecture.
37237 * ARM-Specific Protocol Details::
37238 * MIPS-Specific Protocol Details::
37241 @node ARM-Specific Protocol Details
37242 @subsection @acronym{ARM}-specific Protocol Details
37245 * ARM Breakpoint Kinds::
37248 @node ARM Breakpoint Kinds
37249 @subsubsection @acronym{ARM} Breakpoint Kinds
37250 @cindex breakpoint kinds, @acronym{ARM}
37252 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37257 16-bit Thumb mode breakpoint.
37260 32-bit Thumb mode (Thumb-2) breakpoint.
37263 32-bit @acronym{ARM} mode breakpoint.
37267 @node MIPS-Specific Protocol Details
37268 @subsection @acronym{MIPS}-specific Protocol Details
37271 * MIPS Register packet Format::
37272 * MIPS Breakpoint Kinds::
37275 @node MIPS Register packet Format
37276 @subsubsection @acronym{MIPS} Register Packet Format
37277 @cindex register packet format, @acronym{MIPS}
37279 The following @code{g}/@code{G} packets have previously been defined.
37280 In the below, some thirty-two bit registers are transferred as
37281 sixty-four bits. Those registers should be zero/sign extended (which?)
37282 to fill the space allocated. Register bytes are transferred in target
37283 byte order. The two nibbles within a register byte are transferred
37284 most-significant -- least-significant.
37289 All registers are transferred as thirty-two bit quantities in the order:
37290 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37291 registers; fsr; fir; fp.
37294 All registers are transferred as sixty-four bit quantities (including
37295 thirty-two bit registers such as @code{sr}). The ordering is the same
37300 @node MIPS Breakpoint Kinds
37301 @subsubsection @acronym{MIPS} Breakpoint Kinds
37302 @cindex breakpoint kinds, @acronym{MIPS}
37304 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37309 16-bit @acronym{MIPS16} mode breakpoint.
37312 16-bit @acronym{microMIPS} mode breakpoint.
37315 32-bit standard @acronym{MIPS} mode breakpoint.
37318 32-bit @acronym{microMIPS} mode breakpoint.
37322 @node Tracepoint Packets
37323 @section Tracepoint Packets
37324 @cindex tracepoint packets
37325 @cindex packets, tracepoint
37327 Here we describe the packets @value{GDBN} uses to implement
37328 tracepoints (@pxref{Tracepoints}).
37332 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37333 @cindex @samp{QTDP} packet
37334 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37335 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37336 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37337 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37338 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37339 the number of bytes that the target should copy elsewhere to make room
37340 for the tracepoint. If an @samp{X} is present, it introduces a
37341 tracepoint condition, which consists of a hexadecimal length, followed
37342 by a comma and hex-encoded bytes, in a manner similar to action
37343 encodings as described below. If the trailing @samp{-} is present,
37344 further @samp{QTDP} packets will follow to specify this tracepoint's
37350 The packet was understood and carried out.
37352 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37354 The packet was not recognized.
37357 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37358 Define actions to be taken when a tracepoint is hit. The @var{n} and
37359 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37360 this tracepoint. This packet may only be sent immediately after
37361 another @samp{QTDP} packet that ended with a @samp{-}. If the
37362 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37363 specifying more actions for this tracepoint.
37365 In the series of action packets for a given tracepoint, at most one
37366 can have an @samp{S} before its first @var{action}. If such a packet
37367 is sent, it and the following packets define ``while-stepping''
37368 actions. Any prior packets define ordinary actions --- that is, those
37369 taken when the tracepoint is first hit. If no action packet has an
37370 @samp{S}, then all the packets in the series specify ordinary
37371 tracepoint actions.
37373 The @samp{@var{action}@dots{}} portion of the packet is a series of
37374 actions, concatenated without separators. Each action has one of the
37380 Collect the registers whose bits are set in @var{mask},
37381 a hexadecimal number whose @var{i}'th bit is set if register number
37382 @var{i} should be collected. (The least significant bit is numbered
37383 zero.) Note that @var{mask} may be any number of digits long; it may
37384 not fit in a 32-bit word.
37386 @item M @var{basereg},@var{offset},@var{len}
37387 Collect @var{len} bytes of memory starting at the address in register
37388 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37389 @samp{-1}, then the range has a fixed address: @var{offset} is the
37390 address of the lowest byte to collect. The @var{basereg},
37391 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37392 values (the @samp{-1} value for @var{basereg} is a special case).
37394 @item X @var{len},@var{expr}
37395 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37396 it directs. The agent expression @var{expr} is as described in
37397 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37398 two-digit hex number in the packet; @var{len} is the number of bytes
37399 in the expression (and thus one-half the number of hex digits in the
37404 Any number of actions may be packed together in a single @samp{QTDP}
37405 packet, as long as the packet does not exceed the maximum packet
37406 length (400 bytes, for many stubs). There may be only one @samp{R}
37407 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37408 actions. Any registers referred to by @samp{M} and @samp{X} actions
37409 must be collected by a preceding @samp{R} action. (The
37410 ``while-stepping'' actions are treated as if they were attached to a
37411 separate tracepoint, as far as these restrictions are concerned.)
37416 The packet was understood and carried out.
37418 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37420 The packet was not recognized.
37423 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37424 @cindex @samp{QTDPsrc} packet
37425 Specify a source string of tracepoint @var{n} at address @var{addr}.
37426 This is useful to get accurate reproduction of the tracepoints
37427 originally downloaded at the beginning of the trace run. The @var{type}
37428 is the name of the tracepoint part, such as @samp{cond} for the
37429 tracepoint's conditional expression (see below for a list of types), while
37430 @var{bytes} is the string, encoded in hexadecimal.
37432 @var{start} is the offset of the @var{bytes} within the overall source
37433 string, while @var{slen} is the total length of the source string.
37434 This is intended for handling source strings that are longer than will
37435 fit in a single packet.
37436 @c Add detailed example when this info is moved into a dedicated
37437 @c tracepoint descriptions section.
37439 The available string types are @samp{at} for the location,
37440 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37441 @value{GDBN} sends a separate packet for each command in the action
37442 list, in the same order in which the commands are stored in the list.
37444 The target does not need to do anything with source strings except
37445 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37448 Although this packet is optional, and @value{GDBN} will only send it
37449 if the target replies with @samp{TracepointSource} @xref{General
37450 Query Packets}, it makes both disconnected tracing and trace files
37451 much easier to use. Otherwise the user must be careful that the
37452 tracepoints in effect while looking at trace frames are identical to
37453 the ones in effect during the trace run; even a small discrepancy
37454 could cause @samp{tdump} not to work, or a particular trace frame not
37457 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
37458 @cindex define trace state variable, remote request
37459 @cindex @samp{QTDV} packet
37460 Create a new trace state variable, number @var{n}, with an initial
37461 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37462 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37463 the option of not using this packet for initial values of zero; the
37464 target should simply create the trace state variables as they are
37465 mentioned in expressions. The value @var{builtin} should be 1 (one)
37466 if the trace state variable is builtin and 0 (zero) if it is not builtin.
37467 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
37468 @samp{qTsV} packet had it set. The contents of @var{name} is the
37469 hex-encoded name (without the leading @samp{$}) of the trace state
37472 @item QTFrame:@var{n}
37473 @cindex @samp{QTFrame} packet
37474 Select the @var{n}'th tracepoint frame from the buffer, and use the
37475 register and memory contents recorded there to answer subsequent
37476 request packets from @value{GDBN}.
37478 A successful reply from the stub indicates that the stub has found the
37479 requested frame. The response is a series of parts, concatenated
37480 without separators, describing the frame we selected. Each part has
37481 one of the following forms:
37485 The selected frame is number @var{n} in the trace frame buffer;
37486 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37487 was no frame matching the criteria in the request packet.
37490 The selected trace frame records a hit of tracepoint number @var{t};
37491 @var{t} is a hexadecimal number.
37495 @item QTFrame:pc:@var{addr}
37496 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37497 currently selected frame whose PC is @var{addr};
37498 @var{addr} is a hexadecimal number.
37500 @item QTFrame:tdp:@var{t}
37501 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37502 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37503 is a hexadecimal number.
37505 @item QTFrame:range:@var{start}:@var{end}
37506 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37507 currently selected frame whose PC is between @var{start} (inclusive)
37508 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37511 @item QTFrame:outside:@var{start}:@var{end}
37512 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37513 frame @emph{outside} the given range of addresses (exclusive).
37516 @cindex @samp{qTMinFTPILen} packet
37517 This packet requests the minimum length of instruction at which a fast
37518 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37519 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37520 it depends on the target system being able to create trampolines in
37521 the first 64K of memory, which might or might not be possible for that
37522 system. So the reply to this packet will be 4 if it is able to
37529 The minimum instruction length is currently unknown.
37531 The minimum instruction length is @var{length}, where @var{length}
37532 is a hexadecimal number greater or equal to 1. A reply
37533 of 1 means that a fast tracepoint may be placed on any instruction
37534 regardless of size.
37536 An error has occurred.
37538 An empty reply indicates that the request is not supported by the stub.
37542 @cindex @samp{QTStart} packet
37543 Begin the tracepoint experiment. Begin collecting data from
37544 tracepoint hits in the trace frame buffer. This packet supports the
37545 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37546 instruction reply packet}).
37549 @cindex @samp{QTStop} packet
37550 End the tracepoint experiment. Stop collecting trace frames.
37552 @item QTEnable:@var{n}:@var{addr}
37554 @cindex @samp{QTEnable} packet
37555 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37556 experiment. If the tracepoint was previously disabled, then collection
37557 of data from it will resume.
37559 @item QTDisable:@var{n}:@var{addr}
37561 @cindex @samp{QTDisable} packet
37562 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37563 experiment. No more data will be collected from the tracepoint unless
37564 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37567 @cindex @samp{QTinit} packet
37568 Clear the table of tracepoints, and empty the trace frame buffer.
37570 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37571 @cindex @samp{QTro} packet
37572 Establish the given ranges of memory as ``transparent''. The stub
37573 will answer requests for these ranges from memory's current contents,
37574 if they were not collected as part of the tracepoint hit.
37576 @value{GDBN} uses this to mark read-only regions of memory, like those
37577 containing program code. Since these areas never change, they should
37578 still have the same contents they did when the tracepoint was hit, so
37579 there's no reason for the stub to refuse to provide their contents.
37581 @item QTDisconnected:@var{value}
37582 @cindex @samp{QTDisconnected} packet
37583 Set the choice to what to do with the tracing run when @value{GDBN}
37584 disconnects from the target. A @var{value} of 1 directs the target to
37585 continue the tracing run, while 0 tells the target to stop tracing if
37586 @value{GDBN} is no longer in the picture.
37589 @cindex @samp{qTStatus} packet
37590 Ask the stub if there is a trace experiment running right now.
37592 The reply has the form:
37596 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37597 @var{running} is a single digit @code{1} if the trace is presently
37598 running, or @code{0} if not. It is followed by semicolon-separated
37599 optional fields that an agent may use to report additional status.
37603 If the trace is not running, the agent may report any of several
37604 explanations as one of the optional fields:
37609 No trace has been run yet.
37611 @item tstop[:@var{text}]:0
37612 The trace was stopped by a user-originated stop command. The optional
37613 @var{text} field is a user-supplied string supplied as part of the
37614 stop command (for instance, an explanation of why the trace was
37615 stopped manually). It is hex-encoded.
37618 The trace stopped because the trace buffer filled up.
37620 @item tdisconnected:0
37621 The trace stopped because @value{GDBN} disconnected from the target.
37623 @item tpasscount:@var{tpnum}
37624 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37626 @item terror:@var{text}:@var{tpnum}
37627 The trace stopped because tracepoint @var{tpnum} had an error. The
37628 string @var{text} is available to describe the nature of the error
37629 (for instance, a divide by zero in the condition expression); it
37633 The trace stopped for some other reason.
37637 Additional optional fields supply statistical and other information.
37638 Although not required, they are extremely useful for users monitoring
37639 the progress of a trace run. If a trace has stopped, and these
37640 numbers are reported, they must reflect the state of the just-stopped
37645 @item tframes:@var{n}
37646 The number of trace frames in the buffer.
37648 @item tcreated:@var{n}
37649 The total number of trace frames created during the run. This may
37650 be larger than the trace frame count, if the buffer is circular.
37652 @item tsize:@var{n}
37653 The total size of the trace buffer, in bytes.
37655 @item tfree:@var{n}
37656 The number of bytes still unused in the buffer.
37658 @item circular:@var{n}
37659 The value of the circular trace buffer flag. @code{1} means that the
37660 trace buffer is circular and old trace frames will be discarded if
37661 necessary to make room, @code{0} means that the trace buffer is linear
37664 @item disconn:@var{n}
37665 The value of the disconnected tracing flag. @code{1} means that
37666 tracing will continue after @value{GDBN} disconnects, @code{0} means
37667 that the trace run will stop.
37671 @item qTP:@var{tp}:@var{addr}
37672 @cindex tracepoint status, remote request
37673 @cindex @samp{qTP} packet
37674 Ask the stub for the current state of tracepoint number @var{tp} at
37675 address @var{addr}.
37679 @item V@var{hits}:@var{usage}
37680 The tracepoint has been hit @var{hits} times so far during the trace
37681 run, and accounts for @var{usage} in the trace buffer. Note that
37682 @code{while-stepping} steps are not counted as separate hits, but the
37683 steps' space consumption is added into the usage number.
37687 @item qTV:@var{var}
37688 @cindex trace state variable value, remote request
37689 @cindex @samp{qTV} packet
37690 Ask the stub for the value of the trace state variable number @var{var}.
37695 The value of the variable is @var{value}. This will be the current
37696 value of the variable if the user is examining a running target, or a
37697 saved value if the variable was collected in the trace frame that the
37698 user is looking at. Note that multiple requests may result in
37699 different reply values, such as when requesting values while the
37700 program is running.
37703 The value of the variable is unknown. This would occur, for example,
37704 if the user is examining a trace frame in which the requested variable
37709 @cindex @samp{qTfP} packet
37711 @cindex @samp{qTsP} packet
37712 These packets request data about tracepoints that are being used by
37713 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37714 of data, and multiple @code{qTsP} to get additional pieces. Replies
37715 to these packets generally take the form of the @code{QTDP} packets
37716 that define tracepoints. (FIXME add detailed syntax)
37719 @cindex @samp{qTfV} packet
37721 @cindex @samp{qTsV} packet
37722 These packets request data about trace state variables that are on the
37723 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37724 and multiple @code{qTsV} to get additional variables. Replies to
37725 these packets follow the syntax of the @code{QTDV} packets that define
37726 trace state variables.
37732 @cindex @samp{qTfSTM} packet
37733 @cindex @samp{qTsSTM} packet
37734 These packets request data about static tracepoint markers that exist
37735 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37736 first piece of data, and multiple @code{qTsSTM} to get additional
37737 pieces. Replies to these packets take the following form:
37741 @item m @var{address}:@var{id}:@var{extra}
37743 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37744 a comma-separated list of markers
37746 (lower case letter @samp{L}) denotes end of list.
37748 An error occurred. The error number @var{nn} is given as hex digits.
37750 An empty reply indicates that the request is not supported by the
37754 The @var{address} is encoded in hex;
37755 @var{id} and @var{extra} are strings encoded in hex.
37757 In response to each query, the target will reply with a list of one or
37758 more markers, separated by commas. @value{GDBN} will respond to each
37759 reply with a request for more markers (using the @samp{qs} form of the
37760 query), until the target responds with @samp{l} (lower-case ell, for
37763 @item qTSTMat:@var{address}
37765 @cindex @samp{qTSTMat} packet
37766 This packets requests data about static tracepoint markers in the
37767 target program at @var{address}. Replies to this packet follow the
37768 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37769 tracepoint markers.
37771 @item QTSave:@var{filename}
37772 @cindex @samp{QTSave} packet
37773 This packet directs the target to save trace data to the file name
37774 @var{filename} in the target's filesystem. The @var{filename} is encoded
37775 as a hex string; the interpretation of the file name (relative vs
37776 absolute, wild cards, etc) is up to the target.
37778 @item qTBuffer:@var{offset},@var{len}
37779 @cindex @samp{qTBuffer} packet
37780 Return up to @var{len} bytes of the current contents of trace buffer,
37781 starting at @var{offset}. The trace buffer is treated as if it were
37782 a contiguous collection of traceframes, as per the trace file format.
37783 The reply consists as many hex-encoded bytes as the target can deliver
37784 in a packet; it is not an error to return fewer than were asked for.
37785 A reply consisting of just @code{l} indicates that no bytes are
37788 @item QTBuffer:circular:@var{value}
37789 This packet directs the target to use a circular trace buffer if
37790 @var{value} is 1, or a linear buffer if the value is 0.
37792 @item QTBuffer:size:@var{size}
37793 @anchor{QTBuffer-size}
37794 @cindex @samp{QTBuffer size} packet
37795 This packet directs the target to make the trace buffer be of size
37796 @var{size} if possible. A value of @code{-1} tells the target to
37797 use whatever size it prefers.
37799 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37800 @cindex @samp{QTNotes} packet
37801 This packet adds optional textual notes to the trace run. Allowable
37802 types include @code{user}, @code{notes}, and @code{tstop}, the
37803 @var{text} fields are arbitrary strings, hex-encoded.
37807 @subsection Relocate instruction reply packet
37808 When installing fast tracepoints in memory, the target may need to
37809 relocate the instruction currently at the tracepoint address to a
37810 different address in memory. For most instructions, a simple copy is
37811 enough, but, for example, call instructions that implicitly push the
37812 return address on the stack, and relative branches or other
37813 PC-relative instructions require offset adjustment, so that the effect
37814 of executing the instruction at a different address is the same as if
37815 it had executed in the original location.
37817 In response to several of the tracepoint packets, the target may also
37818 respond with a number of intermediate @samp{qRelocInsn} request
37819 packets before the final result packet, to have @value{GDBN} handle
37820 this relocation operation. If a packet supports this mechanism, its
37821 documentation will explicitly say so. See for example the above
37822 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37823 format of the request is:
37826 @item qRelocInsn:@var{from};@var{to}
37828 This requests @value{GDBN} to copy instruction at address @var{from}
37829 to address @var{to}, possibly adjusted so that executing the
37830 instruction at @var{to} has the same effect as executing it at
37831 @var{from}. @value{GDBN} writes the adjusted instruction to target
37832 memory starting at @var{to}.
37837 @item qRelocInsn:@var{adjusted_size}
37838 Informs the stub the relocation is complete. The @var{adjusted_size} is
37839 the length in bytes of resulting relocated instruction sequence.
37841 A badly formed request was detected, or an error was encountered while
37842 relocating the instruction.
37845 @node Host I/O Packets
37846 @section Host I/O Packets
37847 @cindex Host I/O, remote protocol
37848 @cindex file transfer, remote protocol
37850 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37851 operations on the far side of a remote link. For example, Host I/O is
37852 used to upload and download files to a remote target with its own
37853 filesystem. Host I/O uses the same constant values and data structure
37854 layout as the target-initiated File-I/O protocol. However, the
37855 Host I/O packets are structured differently. The target-initiated
37856 protocol relies on target memory to store parameters and buffers.
37857 Host I/O requests are initiated by @value{GDBN}, and the
37858 target's memory is not involved. @xref{File-I/O Remote Protocol
37859 Extension}, for more details on the target-initiated protocol.
37861 The Host I/O request packets all encode a single operation along with
37862 its arguments. They have this format:
37866 @item vFile:@var{operation}: @var{parameter}@dots{}
37867 @var{operation} is the name of the particular request; the target
37868 should compare the entire packet name up to the second colon when checking
37869 for a supported operation. The format of @var{parameter} depends on
37870 the operation. Numbers are always passed in hexadecimal. Negative
37871 numbers have an explicit minus sign (i.e.@: two's complement is not
37872 used). Strings (e.g.@: filenames) are encoded as a series of
37873 hexadecimal bytes. The last argument to a system call may be a
37874 buffer of escaped binary data (@pxref{Binary Data}).
37878 The valid responses to Host I/O packets are:
37882 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37883 @var{result} is the integer value returned by this operation, usually
37884 non-negative for success and -1 for errors. If an error has occured,
37885 @var{errno} will be included in the result specifying a
37886 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37887 operations which return data, @var{attachment} supplies the data as a
37888 binary buffer. Binary buffers in response packets are escaped in the
37889 normal way (@pxref{Binary Data}). See the individual packet
37890 documentation for the interpretation of @var{result} and
37894 An empty response indicates that this operation is not recognized.
37898 These are the supported Host I/O operations:
37901 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
37902 Open a file at @var{filename} and return a file descriptor for it, or
37903 return -1 if an error occurs. The @var{filename} is a string,
37904 @var{flags} is an integer indicating a mask of open flags
37905 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37906 of mode bits to use if the file is created (@pxref{mode_t Values}).
37907 @xref{open}, for details of the open flags and mode values.
37909 @item vFile:close: @var{fd}
37910 Close the open file corresponding to @var{fd} and return 0, or
37911 -1 if an error occurs.
37913 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37914 Read data from the open file corresponding to @var{fd}. Up to
37915 @var{count} bytes will be read from the file, starting at @var{offset}
37916 relative to the start of the file. The target may read fewer bytes;
37917 common reasons include packet size limits and an end-of-file
37918 condition. The number of bytes read is returned. Zero should only be
37919 returned for a successful read at the end of the file, or if
37920 @var{count} was zero.
37922 The data read should be returned as a binary attachment on success.
37923 If zero bytes were read, the response should include an empty binary
37924 attachment (i.e.@: a trailing semicolon). The return value is the
37925 number of target bytes read; the binary attachment may be longer if
37926 some characters were escaped.
37928 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37929 Write @var{data} (a binary buffer) to the open file corresponding
37930 to @var{fd}. Start the write at @var{offset} from the start of the
37931 file. Unlike many @code{write} system calls, there is no
37932 separate @var{count} argument; the length of @var{data} in the
37933 packet is used. @samp{vFile:write} returns the number of bytes written,
37934 which may be shorter than the length of @var{data}, or -1 if an
37937 @item vFile:fstat: @var{fd}
37938 Get information about the open file corresponding to @var{fd}.
37939 On success the information is returned as a binary attachment
37940 and the return value is the size of this attachment in bytes.
37941 If an error occurs the return value is -1. The format of the
37942 returned binary attachment is as described in @ref{struct stat}.
37944 @item vFile:unlink: @var{filename}
37945 Delete the file at @var{filename} on the target. Return 0,
37946 or -1 if an error occurs. The @var{filename} is a string.
37948 @item vFile:readlink: @var{filename}
37949 Read value of symbolic link @var{filename} on the target. Return
37950 the number of bytes read, or -1 if an error occurs.
37952 The data read should be returned as a binary attachment on success.
37953 If zero bytes were read, the response should include an empty binary
37954 attachment (i.e.@: a trailing semicolon). The return value is the
37955 number of target bytes read; the binary attachment may be longer if
37956 some characters were escaped.
37958 @item vFile:setfs: @var{pid}
37959 Select the filesystem on which @code{vFile} operations with
37960 @var{filename} arguments will operate. This is required for
37961 @value{GDBN} to be able to access files on remote targets where
37962 the remote stub does not share a common filesystem with the
37965 If @var{pid} is nonzero, select the filesystem as seen by process
37966 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
37967 the remote stub. Return 0 on success, or -1 if an error occurs.
37968 If @code{vFile:setfs:} indicates success, the selected filesystem
37969 remains selected until the next successful @code{vFile:setfs:}
37975 @section Interrupts
37976 @cindex interrupts (remote protocol)
37977 @anchor{interrupting remote targets}
37979 In all-stop mode, when a program on the remote target is running,
37980 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
37981 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
37982 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37984 The precise meaning of @code{BREAK} is defined by the transport
37985 mechanism and may, in fact, be undefined. @value{GDBN} does not
37986 currently define a @code{BREAK} mechanism for any of the network
37987 interfaces except for TCP, in which case @value{GDBN} sends the
37988 @code{telnet} BREAK sequence.
37990 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
37991 transport mechanisms. It is represented by sending the single byte
37992 @code{0x03} without any of the usual packet overhead described in
37993 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
37994 transmitted as part of a packet, it is considered to be packet data
37995 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
37996 (@pxref{X packet}), used for binary downloads, may include an unescaped
37997 @code{0x03} as part of its packet.
37999 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38000 When Linux kernel receives this sequence from serial port,
38001 it stops execution and connects to gdb.
38003 In non-stop mode, because packet resumptions are asynchronous
38004 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
38005 command to the remote stub, even when the target is running. For that
38006 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
38007 packet}) with the usual packet framing instead of the single byte
38010 Stubs are not required to recognize these interrupt mechanisms and the
38011 precise meaning associated with receipt of the interrupt is
38012 implementation defined. If the target supports debugging of multiple
38013 threads and/or processes, it should attempt to interrupt all
38014 currently-executing threads and processes.
38015 If the stub is successful at interrupting the
38016 running program, it should send one of the stop
38017 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38018 of successfully stopping the program in all-stop mode, and a stop reply
38019 for each stopped thread in non-stop mode.
38020 Interrupts received while the
38021 program is stopped are discarded.
38023 @node Notification Packets
38024 @section Notification Packets
38025 @cindex notification packets
38026 @cindex packets, notification
38028 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38029 packets that require no acknowledgment. Both the GDB and the stub
38030 may send notifications (although the only notifications defined at
38031 present are sent by the stub). Notifications carry information
38032 without incurring the round-trip latency of an acknowledgment, and so
38033 are useful for low-impact communications where occasional packet loss
38036 A notification packet has the form @samp{% @var{data} #
38037 @var{checksum}}, where @var{data} is the content of the notification,
38038 and @var{checksum} is a checksum of @var{data}, computed and formatted
38039 as for ordinary @value{GDBN} packets. A notification's @var{data}
38040 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38041 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38042 to acknowledge the notification's receipt or to report its corruption.
38044 Every notification's @var{data} begins with a name, which contains no
38045 colon characters, followed by a colon character.
38047 Recipients should silently ignore corrupted notifications and
38048 notifications they do not understand. Recipients should restart
38049 timeout periods on receipt of a well-formed notification, whether or
38050 not they understand it.
38052 Senders should only send the notifications described here when this
38053 protocol description specifies that they are permitted. In the
38054 future, we may extend the protocol to permit existing notifications in
38055 new contexts; this rule helps older senders avoid confusing newer
38058 (Older versions of @value{GDBN} ignore bytes received until they see
38059 the @samp{$} byte that begins an ordinary packet, so new stubs may
38060 transmit notifications without fear of confusing older clients. There
38061 are no notifications defined for @value{GDBN} to send at the moment, but we
38062 assume that most older stubs would ignore them, as well.)
38064 Each notification is comprised of three parts:
38066 @item @var{name}:@var{event}
38067 The notification packet is sent by the side that initiates the
38068 exchange (currently, only the stub does that), with @var{event}
38069 carrying the specific information about the notification, and
38070 @var{name} specifying the name of the notification.
38072 The acknowledge sent by the other side, usually @value{GDBN}, to
38073 acknowledge the exchange and request the event.
38076 The purpose of an asynchronous notification mechanism is to report to
38077 @value{GDBN} that something interesting happened in the remote stub.
38079 The remote stub may send notification @var{name}:@var{event}
38080 at any time, but @value{GDBN} acknowledges the notification when
38081 appropriate. The notification event is pending before @value{GDBN}
38082 acknowledges. Only one notification at a time may be pending; if
38083 additional events occur before @value{GDBN} has acknowledged the
38084 previous notification, they must be queued by the stub for later
38085 synchronous transmission in response to @var{ack} packets from
38086 @value{GDBN}. Because the notification mechanism is unreliable,
38087 the stub is permitted to resend a notification if it believes
38088 @value{GDBN} may not have received it.
38090 Specifically, notifications may appear when @value{GDBN} is not
38091 otherwise reading input from the stub, or when @value{GDBN} is
38092 expecting to read a normal synchronous response or a
38093 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38094 Notification packets are distinct from any other communication from
38095 the stub so there is no ambiguity.
38097 After receiving a notification, @value{GDBN} shall acknowledge it by
38098 sending a @var{ack} packet as a regular, synchronous request to the
38099 stub. Such acknowledgment is not required to happen immediately, as
38100 @value{GDBN} is permitted to send other, unrelated packets to the
38101 stub first, which the stub should process normally.
38103 Upon receiving a @var{ack} packet, if the stub has other queued
38104 events to report to @value{GDBN}, it shall respond by sending a
38105 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38106 packet to solicit further responses; again, it is permitted to send
38107 other, unrelated packets as well which the stub should process
38110 If the stub receives a @var{ack} packet and there are no additional
38111 @var{event} to report, the stub shall return an @samp{OK} response.
38112 At this point, @value{GDBN} has finished processing a notification
38113 and the stub has completed sending any queued events. @value{GDBN}
38114 won't accept any new notifications until the final @samp{OK} is
38115 received . If further notification events occur, the stub shall send
38116 a new notification, @value{GDBN} shall accept the notification, and
38117 the process shall be repeated.
38119 The process of asynchronous notification can be illustrated by the
38122 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38125 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38127 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38132 The following notifications are defined:
38133 @multitable @columnfractions 0.12 0.12 0.38 0.38
38142 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38143 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38144 for information on how these notifications are acknowledged by
38146 @tab Report an asynchronous stop event in non-stop mode.
38150 @node Remote Non-Stop
38151 @section Remote Protocol Support for Non-Stop Mode
38153 @value{GDBN}'s remote protocol supports non-stop debugging of
38154 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38155 supports non-stop mode, it should report that to @value{GDBN} by including
38156 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38158 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38159 establishing a new connection with the stub. Entering non-stop mode
38160 does not alter the state of any currently-running threads, but targets
38161 must stop all threads in any already-attached processes when entering
38162 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38163 probe the target state after a mode change.
38165 In non-stop mode, when an attached process encounters an event that
38166 would otherwise be reported with a stop reply, it uses the
38167 asynchronous notification mechanism (@pxref{Notification Packets}) to
38168 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38169 in all processes are stopped when a stop reply is sent, in non-stop
38170 mode only the thread reporting the stop event is stopped. That is,
38171 when reporting a @samp{S} or @samp{T} response to indicate completion
38172 of a step operation, hitting a breakpoint, or a fault, only the
38173 affected thread is stopped; any other still-running threads continue
38174 to run. When reporting a @samp{W} or @samp{X} response, all running
38175 threads belonging to other attached processes continue to run.
38177 In non-stop mode, the target shall respond to the @samp{?} packet as
38178 follows. First, any incomplete stop reply notification/@samp{vStopped}
38179 sequence in progress is abandoned. The target must begin a new
38180 sequence reporting stop events for all stopped threads, whether or not
38181 it has previously reported those events to @value{GDBN}. The first
38182 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38183 subsequent stop replies are sent as responses to @samp{vStopped} packets
38184 using the mechanism described above. The target must not send
38185 asynchronous stop reply notifications until the sequence is complete.
38186 If all threads are running when the target receives the @samp{?} packet,
38187 or if the target is not attached to any process, it shall respond
38190 If the stub supports non-stop mode, it should also support the
38191 @samp{swbreak} stop reason if software breakpoints are supported, and
38192 the @samp{hwbreak} stop reason if hardware breakpoints are supported
38193 (@pxref{swbreak stop reason}). This is because given the asynchronous
38194 nature of non-stop mode, between the time a thread hits a breakpoint
38195 and the time the event is finally processed by @value{GDBN}, the
38196 breakpoint may have already been removed from the target. Due to
38197 this, @value{GDBN} needs to be able to tell whether a trap stop was
38198 caused by a delayed breakpoint event, which should be ignored, as
38199 opposed to a random trap signal, which should be reported to the user.
38200 Note the @samp{swbreak} feature implies that the target is responsible
38201 for adjusting the PC when a software breakpoint triggers, if
38202 necessary, such as on the x86 architecture.
38204 @node Packet Acknowledgment
38205 @section Packet Acknowledgment
38207 @cindex acknowledgment, for @value{GDBN} remote
38208 @cindex packet acknowledgment, for @value{GDBN} remote
38209 By default, when either the host or the target machine receives a packet,
38210 the first response expected is an acknowledgment: either @samp{+} (to indicate
38211 the package was received correctly) or @samp{-} (to request retransmission).
38212 This mechanism allows the @value{GDBN} remote protocol to operate over
38213 unreliable transport mechanisms, such as a serial line.
38215 In cases where the transport mechanism is itself reliable (such as a pipe or
38216 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38217 It may be desirable to disable them in that case to reduce communication
38218 overhead, or for other reasons. This can be accomplished by means of the
38219 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38221 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38222 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38223 and response format still includes the normal checksum, as described in
38224 @ref{Overview}, but the checksum may be ignored by the receiver.
38226 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38227 no-acknowledgment mode, it should report that to @value{GDBN}
38228 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38229 @pxref{qSupported}.
38230 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38231 disabled via the @code{set remote noack-packet off} command
38232 (@pxref{Remote Configuration}),
38233 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38234 Only then may the stub actually turn off packet acknowledgments.
38235 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38236 response, which can be safely ignored by the stub.
38238 Note that @code{set remote noack-packet} command only affects negotiation
38239 between @value{GDBN} and the stub when subsequent connections are made;
38240 it does not affect the protocol acknowledgment state for any current
38242 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38243 new connection is established,
38244 there is also no protocol request to re-enable the acknowledgments
38245 for the current connection, once disabled.
38250 Example sequence of a target being re-started. Notice how the restart
38251 does not get any direct output:
38256 @emph{target restarts}
38259 <- @code{T001:1234123412341234}
38263 Example sequence of a target being stepped by a single instruction:
38266 -> @code{G1445@dots{}}
38271 <- @code{T001:1234123412341234}
38275 <- @code{1455@dots{}}
38279 @node File-I/O Remote Protocol Extension
38280 @section File-I/O Remote Protocol Extension
38281 @cindex File-I/O remote protocol extension
38284 * File-I/O Overview::
38285 * Protocol Basics::
38286 * The F Request Packet::
38287 * The F Reply Packet::
38288 * The Ctrl-C Message::
38290 * List of Supported Calls::
38291 * Protocol-specific Representation of Datatypes::
38293 * File-I/O Examples::
38296 @node File-I/O Overview
38297 @subsection File-I/O Overview
38298 @cindex file-i/o overview
38300 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38301 target to use the host's file system and console I/O to perform various
38302 system calls. System calls on the target system are translated into a
38303 remote protocol packet to the host system, which then performs the needed
38304 actions and returns a response packet to the target system.
38305 This simulates file system operations even on targets that lack file systems.
38307 The protocol is defined to be independent of both the host and target systems.
38308 It uses its own internal representation of datatypes and values. Both
38309 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38310 translating the system-dependent value representations into the internal
38311 protocol representations when data is transmitted.
38313 The communication is synchronous. A system call is possible only when
38314 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38315 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38316 the target is stopped to allow deterministic access to the target's
38317 memory. Therefore File-I/O is not interruptible by target signals. On
38318 the other hand, it is possible to interrupt File-I/O by a user interrupt
38319 (@samp{Ctrl-C}) within @value{GDBN}.
38321 The target's request to perform a host system call does not finish
38322 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38323 after finishing the system call, the target returns to continuing the
38324 previous activity (continue, step). No additional continue or step
38325 request from @value{GDBN} is required.
38328 (@value{GDBP}) continue
38329 <- target requests 'system call X'
38330 target is stopped, @value{GDBN} executes system call
38331 -> @value{GDBN} returns result
38332 ... target continues, @value{GDBN} returns to wait for the target
38333 <- target hits breakpoint and sends a Txx packet
38336 The protocol only supports I/O on the console and to regular files on
38337 the host file system. Character or block special devices, pipes,
38338 named pipes, sockets or any other communication method on the host
38339 system are not supported by this protocol.
38341 File I/O is not supported in non-stop mode.
38343 @node Protocol Basics
38344 @subsection Protocol Basics
38345 @cindex protocol basics, file-i/o
38347 The File-I/O protocol uses the @code{F} packet as the request as well
38348 as reply packet. Since a File-I/O system call can only occur when
38349 @value{GDBN} is waiting for a response from the continuing or stepping target,
38350 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38351 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38352 This @code{F} packet contains all information needed to allow @value{GDBN}
38353 to call the appropriate host system call:
38357 A unique identifier for the requested system call.
38360 All parameters to the system call. Pointers are given as addresses
38361 in the target memory address space. Pointers to strings are given as
38362 pointer/length pair. Numerical values are given as they are.
38363 Numerical control flags are given in a protocol-specific representation.
38367 At this point, @value{GDBN} has to perform the following actions.
38371 If the parameters include pointer values to data needed as input to a
38372 system call, @value{GDBN} requests this data from the target with a
38373 standard @code{m} packet request. This additional communication has to be
38374 expected by the target implementation and is handled as any other @code{m}
38378 @value{GDBN} translates all value from protocol representation to host
38379 representation as needed. Datatypes are coerced into the host types.
38382 @value{GDBN} calls the system call.
38385 It then coerces datatypes back to protocol representation.
38388 If the system call is expected to return data in buffer space specified
38389 by pointer parameters to the call, the data is transmitted to the
38390 target using a @code{M} or @code{X} packet. This packet has to be expected
38391 by the target implementation and is handled as any other @code{M} or @code{X}
38396 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38397 necessary information for the target to continue. This at least contains
38404 @code{errno}, if has been changed by the system call.
38411 After having done the needed type and value coercion, the target continues
38412 the latest continue or step action.
38414 @node The F Request Packet
38415 @subsection The @code{F} Request Packet
38416 @cindex file-i/o request packet
38417 @cindex @code{F} request packet
38419 The @code{F} request packet has the following format:
38422 @item F@var{call-id},@var{parameter@dots{}}
38424 @var{call-id} is the identifier to indicate the host system call to be called.
38425 This is just the name of the function.
38427 @var{parameter@dots{}} are the parameters to the system call.
38428 Parameters are hexadecimal integer values, either the actual values in case
38429 of scalar datatypes, pointers to target buffer space in case of compound
38430 datatypes and unspecified memory areas, or pointer/length pairs in case
38431 of string parameters. These are appended to the @var{call-id} as a
38432 comma-delimited list. All values are transmitted in ASCII
38433 string representation, pointer/length pairs separated by a slash.
38439 @node The F Reply Packet
38440 @subsection The @code{F} Reply Packet
38441 @cindex file-i/o reply packet
38442 @cindex @code{F} reply packet
38444 The @code{F} reply packet has the following format:
38448 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38450 @var{retcode} is the return code of the system call as hexadecimal value.
38452 @var{errno} is the @code{errno} set by the call, in protocol-specific
38454 This parameter can be omitted if the call was successful.
38456 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38457 case, @var{errno} must be sent as well, even if the call was successful.
38458 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38465 or, if the call was interrupted before the host call has been performed:
38472 assuming 4 is the protocol-specific representation of @code{EINTR}.
38477 @node The Ctrl-C Message
38478 @subsection The @samp{Ctrl-C} Message
38479 @cindex ctrl-c message, in file-i/o protocol
38481 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38482 reply packet (@pxref{The F Reply Packet}),
38483 the target should behave as if it had
38484 gotten a break message. The meaning for the target is ``system call
38485 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38486 (as with a break message) and return to @value{GDBN} with a @code{T02}
38489 It's important for the target to know in which
38490 state the system call was interrupted. There are two possible cases:
38494 The system call hasn't been performed on the host yet.
38497 The system call on the host has been finished.
38501 These two states can be distinguished by the target by the value of the
38502 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38503 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38504 on POSIX systems. In any other case, the target may presume that the
38505 system call has been finished --- successfully or not --- and should behave
38506 as if the break message arrived right after the system call.
38508 @value{GDBN} must behave reliably. If the system call has not been called
38509 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38510 @code{errno} in the packet. If the system call on the host has been finished
38511 before the user requests a break, the full action must be finished by
38512 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38513 The @code{F} packet may only be sent when either nothing has happened
38514 or the full action has been completed.
38517 @subsection Console I/O
38518 @cindex console i/o as part of file-i/o
38520 By default and if not explicitly closed by the target system, the file
38521 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38522 on the @value{GDBN} console is handled as any other file output operation
38523 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38524 by @value{GDBN} so that after the target read request from file descriptor
38525 0 all following typing is buffered until either one of the following
38530 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38532 system call is treated as finished.
38535 The user presses @key{RET}. This is treated as end of input with a trailing
38539 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38540 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38544 If the user has typed more characters than fit in the buffer given to
38545 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38546 either another @code{read(0, @dots{})} is requested by the target, or debugging
38547 is stopped at the user's request.
38550 @node List of Supported Calls
38551 @subsection List of Supported Calls
38552 @cindex list of supported file-i/o calls
38569 @unnumberedsubsubsec open
38570 @cindex open, file-i/o system call
38575 int open(const char *pathname, int flags);
38576 int open(const char *pathname, int flags, mode_t mode);
38580 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38583 @var{flags} is the bitwise @code{OR} of the following values:
38587 If the file does not exist it will be created. The host
38588 rules apply as far as file ownership and time stamps
38592 When used with @code{O_CREAT}, if the file already exists it is
38593 an error and open() fails.
38596 If the file already exists and the open mode allows
38597 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38598 truncated to zero length.
38601 The file is opened in append mode.
38604 The file is opened for reading only.
38607 The file is opened for writing only.
38610 The file is opened for reading and writing.
38614 Other bits are silently ignored.
38618 @var{mode} is the bitwise @code{OR} of the following values:
38622 User has read permission.
38625 User has write permission.
38628 Group has read permission.
38631 Group has write permission.
38634 Others have read permission.
38637 Others have write permission.
38641 Other bits are silently ignored.
38644 @item Return value:
38645 @code{open} returns the new file descriptor or -1 if an error
38652 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38655 @var{pathname} refers to a directory.
38658 The requested access is not allowed.
38661 @var{pathname} was too long.
38664 A directory component in @var{pathname} does not exist.
38667 @var{pathname} refers to a device, pipe, named pipe or socket.
38670 @var{pathname} refers to a file on a read-only filesystem and
38671 write access was requested.
38674 @var{pathname} is an invalid pointer value.
38677 No space on device to create the file.
38680 The process already has the maximum number of files open.
38683 The limit on the total number of files open on the system
38687 The call was interrupted by the user.
38693 @unnumberedsubsubsec close
38694 @cindex close, file-i/o system call
38703 @samp{Fclose,@var{fd}}
38705 @item Return value:
38706 @code{close} returns zero on success, or -1 if an error occurred.
38712 @var{fd} isn't a valid open file descriptor.
38715 The call was interrupted by the user.
38721 @unnumberedsubsubsec read
38722 @cindex read, file-i/o system call
38727 int read(int fd, void *buf, unsigned int count);
38731 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38733 @item Return value:
38734 On success, the number of bytes read is returned.
38735 Zero indicates end of file. If count is zero, read
38736 returns zero as well. On error, -1 is returned.
38742 @var{fd} is not a valid file descriptor or is not open for
38746 @var{bufptr} is an invalid pointer value.
38749 The call was interrupted by the user.
38755 @unnumberedsubsubsec write
38756 @cindex write, file-i/o system call
38761 int write(int fd, const void *buf, unsigned int count);
38765 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38767 @item Return value:
38768 On success, the number of bytes written are returned.
38769 Zero indicates nothing was written. On error, -1
38776 @var{fd} is not a valid file descriptor or is not open for
38780 @var{bufptr} is an invalid pointer value.
38783 An attempt was made to write a file that exceeds the
38784 host-specific maximum file size allowed.
38787 No space on device to write the data.
38790 The call was interrupted by the user.
38796 @unnumberedsubsubsec lseek
38797 @cindex lseek, file-i/o system call
38802 long lseek (int fd, long offset, int flag);
38806 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
38808 @var{flag} is one of:
38812 The offset is set to @var{offset} bytes.
38815 The offset is set to its current location plus @var{offset}
38819 The offset is set to the size of the file plus @var{offset}
38823 @item Return value:
38824 On success, the resulting unsigned offset in bytes from
38825 the beginning of the file is returned. Otherwise, a
38826 value of -1 is returned.
38832 @var{fd} is not a valid open file descriptor.
38835 @var{fd} is associated with the @value{GDBN} console.
38838 @var{flag} is not a proper value.
38841 The call was interrupted by the user.
38847 @unnumberedsubsubsec rename
38848 @cindex rename, file-i/o system call
38853 int rename(const char *oldpath, const char *newpath);
38857 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
38859 @item Return value:
38860 On success, zero is returned. On error, -1 is returned.
38866 @var{newpath} is an existing directory, but @var{oldpath} is not a
38870 @var{newpath} is a non-empty directory.
38873 @var{oldpath} or @var{newpath} is a directory that is in use by some
38877 An attempt was made to make a directory a subdirectory
38881 A component used as a directory in @var{oldpath} or new
38882 path is not a directory. Or @var{oldpath} is a directory
38883 and @var{newpath} exists but is not a directory.
38886 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
38889 No access to the file or the path of the file.
38893 @var{oldpath} or @var{newpath} was too long.
38896 A directory component in @var{oldpath} or @var{newpath} does not exist.
38899 The file is on a read-only filesystem.
38902 The device containing the file has no room for the new
38906 The call was interrupted by the user.
38912 @unnumberedsubsubsec unlink
38913 @cindex unlink, file-i/o system call
38918 int unlink(const char *pathname);
38922 @samp{Funlink,@var{pathnameptr}/@var{len}}
38924 @item Return value:
38925 On success, zero is returned. On error, -1 is returned.
38931 No access to the file or the path of the file.
38934 The system does not allow unlinking of directories.
38937 The file @var{pathname} cannot be unlinked because it's
38938 being used by another process.
38941 @var{pathnameptr} is an invalid pointer value.
38944 @var{pathname} was too long.
38947 A directory component in @var{pathname} does not exist.
38950 A component of the path is not a directory.
38953 The file is on a read-only filesystem.
38956 The call was interrupted by the user.
38962 @unnumberedsubsubsec stat/fstat
38963 @cindex fstat, file-i/o system call
38964 @cindex stat, file-i/o system call
38969 int stat(const char *pathname, struct stat *buf);
38970 int fstat(int fd, struct stat *buf);
38974 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38975 @samp{Ffstat,@var{fd},@var{bufptr}}
38977 @item Return value:
38978 On success, zero is returned. On error, -1 is returned.
38984 @var{fd} is not a valid open file.
38987 A directory component in @var{pathname} does not exist or the
38988 path is an empty string.
38991 A component of the path is not a directory.
38994 @var{pathnameptr} is an invalid pointer value.
38997 No access to the file or the path of the file.
39000 @var{pathname} was too long.
39003 The call was interrupted by the user.
39009 @unnumberedsubsubsec gettimeofday
39010 @cindex gettimeofday, file-i/o system call
39015 int gettimeofday(struct timeval *tv, void *tz);
39019 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39021 @item Return value:
39022 On success, 0 is returned, -1 otherwise.
39028 @var{tz} is a non-NULL pointer.
39031 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39037 @unnumberedsubsubsec isatty
39038 @cindex isatty, file-i/o system call
39043 int isatty(int fd);
39047 @samp{Fisatty,@var{fd}}
39049 @item Return value:
39050 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39056 The call was interrupted by the user.
39061 Note that the @code{isatty} call is treated as a special case: it returns
39062 1 to the target if the file descriptor is attached
39063 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39064 would require implementing @code{ioctl} and would be more complex than
39069 @unnumberedsubsubsec system
39070 @cindex system, file-i/o system call
39075 int system(const char *command);
39079 @samp{Fsystem,@var{commandptr}/@var{len}}
39081 @item Return value:
39082 If @var{len} is zero, the return value indicates whether a shell is
39083 available. A zero return value indicates a shell is not available.
39084 For non-zero @var{len}, the value returned is -1 on error and the
39085 return status of the command otherwise. Only the exit status of the
39086 command is returned, which is extracted from the host's @code{system}
39087 return value by calling @code{WEXITSTATUS(retval)}. In case
39088 @file{/bin/sh} could not be executed, 127 is returned.
39094 The call was interrupted by the user.
39099 @value{GDBN} takes over the full task of calling the necessary host calls
39100 to perform the @code{system} call. The return value of @code{system} on
39101 the host is simplified before it's returned
39102 to the target. Any termination signal information from the child process
39103 is discarded, and the return value consists
39104 entirely of the exit status of the called command.
39106 Due to security concerns, the @code{system} call is by default refused
39107 by @value{GDBN}. The user has to allow this call explicitly with the
39108 @code{set remote system-call-allowed 1} command.
39111 @item set remote system-call-allowed
39112 @kindex set remote system-call-allowed
39113 Control whether to allow the @code{system} calls in the File I/O
39114 protocol for the remote target. The default is zero (disabled).
39116 @item show remote system-call-allowed
39117 @kindex show remote system-call-allowed
39118 Show whether the @code{system} calls are allowed in the File I/O
39122 @node Protocol-specific Representation of Datatypes
39123 @subsection Protocol-specific Representation of Datatypes
39124 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39127 * Integral Datatypes::
39129 * Memory Transfer::
39134 @node Integral Datatypes
39135 @unnumberedsubsubsec Integral Datatypes
39136 @cindex integral datatypes, in file-i/o protocol
39138 The integral datatypes used in the system calls are @code{int},
39139 @code{unsigned int}, @code{long}, @code{unsigned long},
39140 @code{mode_t}, and @code{time_t}.
39142 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39143 implemented as 32 bit values in this protocol.
39145 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39147 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39148 in @file{limits.h}) to allow range checking on host and target.
39150 @code{time_t} datatypes are defined as seconds since the Epoch.
39152 All integral datatypes transferred as part of a memory read or write of a
39153 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39156 @node Pointer Values
39157 @unnumberedsubsubsec Pointer Values
39158 @cindex pointer values, in file-i/o protocol
39160 Pointers to target data are transmitted as they are. An exception
39161 is made for pointers to buffers for which the length isn't
39162 transmitted as part of the function call, namely strings. Strings
39163 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39170 which is a pointer to data of length 18 bytes at position 0x1aaf.
39171 The length is defined as the full string length in bytes, including
39172 the trailing null byte. For example, the string @code{"hello world"}
39173 at address 0x123456 is transmitted as
39179 @node Memory Transfer
39180 @unnumberedsubsubsec Memory Transfer
39181 @cindex memory transfer, in file-i/o protocol
39183 Structured data which is transferred using a memory read or write (for
39184 example, a @code{struct stat}) is expected to be in a protocol-specific format
39185 with all scalar multibyte datatypes being big endian. Translation to
39186 this representation needs to be done both by the target before the @code{F}
39187 packet is sent, and by @value{GDBN} before
39188 it transfers memory to the target. Transferred pointers to structured
39189 data should point to the already-coerced data at any time.
39193 @unnumberedsubsubsec struct stat
39194 @cindex struct stat, in file-i/o protocol
39196 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39197 is defined as follows:
39201 unsigned int st_dev; /* device */
39202 unsigned int st_ino; /* inode */
39203 mode_t st_mode; /* protection */
39204 unsigned int st_nlink; /* number of hard links */
39205 unsigned int st_uid; /* user ID of owner */
39206 unsigned int st_gid; /* group ID of owner */
39207 unsigned int st_rdev; /* device type (if inode device) */
39208 unsigned long st_size; /* total size, in bytes */
39209 unsigned long st_blksize; /* blocksize for filesystem I/O */
39210 unsigned long st_blocks; /* number of blocks allocated */
39211 time_t st_atime; /* time of last access */
39212 time_t st_mtime; /* time of last modification */
39213 time_t st_ctime; /* time of last change */
39217 The integral datatypes conform to the definitions given in the
39218 appropriate section (see @ref{Integral Datatypes}, for details) so this
39219 structure is of size 64 bytes.
39221 The values of several fields have a restricted meaning and/or
39227 A value of 0 represents a file, 1 the console.
39230 No valid meaning for the target. Transmitted unchanged.
39233 Valid mode bits are described in @ref{Constants}. Any other
39234 bits have currently no meaning for the target.
39239 No valid meaning for the target. Transmitted unchanged.
39244 These values have a host and file system dependent
39245 accuracy. Especially on Windows hosts, the file system may not
39246 support exact timing values.
39249 The target gets a @code{struct stat} of the above representation and is
39250 responsible for coercing it to the target representation before
39253 Note that due to size differences between the host, target, and protocol
39254 representations of @code{struct stat} members, these members could eventually
39255 get truncated on the target.
39257 @node struct timeval
39258 @unnumberedsubsubsec struct timeval
39259 @cindex struct timeval, in file-i/o protocol
39261 The buffer of type @code{struct timeval} used by the File-I/O protocol
39262 is defined as follows:
39266 time_t tv_sec; /* second */
39267 long tv_usec; /* microsecond */
39271 The integral datatypes conform to the definitions given in the
39272 appropriate section (see @ref{Integral Datatypes}, for details) so this
39273 structure is of size 8 bytes.
39276 @subsection Constants
39277 @cindex constants, in file-i/o protocol
39279 The following values are used for the constants inside of the
39280 protocol. @value{GDBN} and target are responsible for translating these
39281 values before and after the call as needed.
39292 @unnumberedsubsubsec Open Flags
39293 @cindex open flags, in file-i/o protocol
39295 All values are given in hexadecimal representation.
39307 @node mode_t Values
39308 @unnumberedsubsubsec mode_t Values
39309 @cindex mode_t values, in file-i/o protocol
39311 All values are given in octal representation.
39328 @unnumberedsubsubsec Errno Values
39329 @cindex errno values, in file-i/o protocol
39331 All values are given in decimal representation.
39356 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39357 any error value not in the list of supported error numbers.
39360 @unnumberedsubsubsec Lseek Flags
39361 @cindex lseek flags, in file-i/o protocol
39370 @unnumberedsubsubsec Limits
39371 @cindex limits, in file-i/o protocol
39373 All values are given in decimal representation.
39376 INT_MIN -2147483648
39378 UINT_MAX 4294967295
39379 LONG_MIN -9223372036854775808
39380 LONG_MAX 9223372036854775807
39381 ULONG_MAX 18446744073709551615
39384 @node File-I/O Examples
39385 @subsection File-I/O Examples
39386 @cindex file-i/o examples
39388 Example sequence of a write call, file descriptor 3, buffer is at target
39389 address 0x1234, 6 bytes should be written:
39392 <- @code{Fwrite,3,1234,6}
39393 @emph{request memory read from target}
39396 @emph{return "6 bytes written"}
39400 Example sequence of a read call, file descriptor 3, buffer is at target
39401 address 0x1234, 6 bytes should be read:
39404 <- @code{Fread,3,1234,6}
39405 @emph{request memory write to target}
39406 -> @code{X1234,6:XXXXXX}
39407 @emph{return "6 bytes read"}
39411 Example sequence of a read call, call fails on the host due to invalid
39412 file descriptor (@code{EBADF}):
39415 <- @code{Fread,3,1234,6}
39419 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39423 <- @code{Fread,3,1234,6}
39428 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39432 <- @code{Fread,3,1234,6}
39433 -> @code{X1234,6:XXXXXX}
39437 @node Library List Format
39438 @section Library List Format
39439 @cindex library list format, remote protocol
39441 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39442 same process as your application to manage libraries. In this case,
39443 @value{GDBN} can use the loader's symbol table and normal memory
39444 operations to maintain a list of shared libraries. On other
39445 platforms, the operating system manages loaded libraries.
39446 @value{GDBN} can not retrieve the list of currently loaded libraries
39447 through memory operations, so it uses the @samp{qXfer:libraries:read}
39448 packet (@pxref{qXfer library list read}) instead. The remote stub
39449 queries the target's operating system and reports which libraries
39452 The @samp{qXfer:libraries:read} packet returns an XML document which
39453 lists loaded libraries and their offsets. Each library has an
39454 associated name and one or more segment or section base addresses,
39455 which report where the library was loaded in memory.
39457 For the common case of libraries that are fully linked binaries, the
39458 library should have a list of segments. If the target supports
39459 dynamic linking of a relocatable object file, its library XML element
39460 should instead include a list of allocated sections. The segment or
39461 section bases are start addresses, not relocation offsets; they do not
39462 depend on the library's link-time base addresses.
39464 @value{GDBN} must be linked with the Expat library to support XML
39465 library lists. @xref{Expat}.
39467 A simple memory map, with one loaded library relocated by a single
39468 offset, looks like this:
39472 <library name="/lib/libc.so.6">
39473 <segment address="0x10000000"/>
39478 Another simple memory map, with one loaded library with three
39479 allocated sections (.text, .data, .bss), looks like this:
39483 <library name="sharedlib.o">
39484 <section address="0x10000000"/>
39485 <section address="0x20000000"/>
39486 <section address="0x30000000"/>
39491 The format of a library list is described by this DTD:
39494 <!-- library-list: Root element with versioning -->
39495 <!ELEMENT library-list (library)*>
39496 <!ATTLIST library-list version CDATA #FIXED "1.0">
39497 <!ELEMENT library (segment*, section*)>
39498 <!ATTLIST library name CDATA #REQUIRED>
39499 <!ELEMENT segment EMPTY>
39500 <!ATTLIST segment address CDATA #REQUIRED>
39501 <!ELEMENT section EMPTY>
39502 <!ATTLIST section address CDATA #REQUIRED>
39505 In addition, segments and section descriptors cannot be mixed within a
39506 single library element, and you must supply at least one segment or
39507 section for each library.
39509 @node Library List Format for SVR4 Targets
39510 @section Library List Format for SVR4 Targets
39511 @cindex library list format, remote protocol
39513 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39514 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39515 shared libraries. Still a special library list provided by this packet is
39516 more efficient for the @value{GDBN} remote protocol.
39518 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39519 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39520 target, the following parameters are reported:
39524 @code{name}, the absolute file name from the @code{l_name} field of
39525 @code{struct link_map}.
39527 @code{lm} with address of @code{struct link_map} used for TLS
39528 (Thread Local Storage) access.
39530 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39531 @code{struct link_map}. For prelinked libraries this is not an absolute
39532 memory address. It is a displacement of absolute memory address against
39533 address the file was prelinked to during the library load.
39535 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39538 Additionally the single @code{main-lm} attribute specifies address of
39539 @code{struct link_map} used for the main executable. This parameter is used
39540 for TLS access and its presence is optional.
39542 @value{GDBN} must be linked with the Expat library to support XML
39543 SVR4 library lists. @xref{Expat}.
39545 A simple memory map, with two loaded libraries (which do not use prelink),
39549 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39550 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39552 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39554 </library-list-svr>
39557 The format of an SVR4 library list is described by this DTD:
39560 <!-- library-list-svr4: Root element with versioning -->
39561 <!ELEMENT library-list-svr4 (library)*>
39562 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39563 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39564 <!ELEMENT library EMPTY>
39565 <!ATTLIST library name CDATA #REQUIRED>
39566 <!ATTLIST library lm CDATA #REQUIRED>
39567 <!ATTLIST library l_addr CDATA #REQUIRED>
39568 <!ATTLIST library l_ld CDATA #REQUIRED>
39571 @node Memory Map Format
39572 @section Memory Map Format
39573 @cindex memory map format
39575 To be able to write into flash memory, @value{GDBN} needs to obtain a
39576 memory map from the target. This section describes the format of the
39579 The memory map is obtained using the @samp{qXfer:memory-map:read}
39580 (@pxref{qXfer memory map read}) packet and is an XML document that
39581 lists memory regions.
39583 @value{GDBN} must be linked with the Expat library to support XML
39584 memory maps. @xref{Expat}.
39586 The top-level structure of the document is shown below:
39589 <?xml version="1.0"?>
39590 <!DOCTYPE memory-map
39591 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39592 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39598 Each region can be either:
39603 A region of RAM starting at @var{addr} and extending for @var{length}
39607 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39612 A region of read-only memory:
39615 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39620 A region of flash memory, with erasure blocks @var{blocksize}
39624 <memory type="flash" start="@var{addr}" length="@var{length}">
39625 <property name="blocksize">@var{blocksize}</property>
39631 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39632 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39633 packets to write to addresses in such ranges.
39635 The formal DTD for memory map format is given below:
39638 <!-- ................................................... -->
39639 <!-- Memory Map XML DTD ................................ -->
39640 <!-- File: memory-map.dtd .............................. -->
39641 <!-- .................................... .............. -->
39642 <!-- memory-map.dtd -->
39643 <!-- memory-map: Root element with versioning -->
39644 <!ELEMENT memory-map (memory | property)>
39645 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39646 <!ELEMENT memory (property)>
39647 <!-- memory: Specifies a memory region,
39648 and its type, or device. -->
39649 <!ATTLIST memory type CDATA #REQUIRED
39650 start CDATA #REQUIRED
39651 length CDATA #REQUIRED
39652 device CDATA #IMPLIED>
39653 <!-- property: Generic attribute tag -->
39654 <!ELEMENT property (#PCDATA | property)*>
39655 <!ATTLIST property name CDATA #REQUIRED>
39658 @node Thread List Format
39659 @section Thread List Format
39660 @cindex thread list format
39662 To efficiently update the list of threads and their attributes,
39663 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39664 (@pxref{qXfer threads read}) and obtains the XML document with
39665 the following structure:
39668 <?xml version="1.0"?>
39670 <thread id="id" core="0" name="name">
39671 ... description ...
39676 Each @samp{thread} element must have the @samp{id} attribute that
39677 identifies the thread (@pxref{thread-id syntax}). The
39678 @samp{core} attribute, if present, specifies which processor core
39679 the thread was last executing on. The @samp{name} attribute, if
39680 present, specifies the human-readable name of the thread. The content
39681 of the of @samp{thread} element is interpreted as human-readable
39682 auxiliary information.
39684 @node Traceframe Info Format
39685 @section Traceframe Info Format
39686 @cindex traceframe info format
39688 To be able to know which objects in the inferior can be examined when
39689 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39690 memory ranges, registers and trace state variables that have been
39691 collected in a traceframe.
39693 This list is obtained using the @samp{qXfer:traceframe-info:read}
39694 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39696 @value{GDBN} must be linked with the Expat library to support XML
39697 traceframe info discovery. @xref{Expat}.
39699 The top-level structure of the document is shown below:
39702 <?xml version="1.0"?>
39703 <!DOCTYPE traceframe-info
39704 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39705 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39711 Each traceframe block can be either:
39716 A region of collected memory starting at @var{addr} and extending for
39717 @var{length} bytes from there:
39720 <memory start="@var{addr}" length="@var{length}"/>
39724 A block indicating trace state variable numbered @var{number} has been
39728 <tvar id="@var{number}"/>
39733 The formal DTD for the traceframe info format is given below:
39736 <!ELEMENT traceframe-info (memory | tvar)* >
39737 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39739 <!ELEMENT memory EMPTY>
39740 <!ATTLIST memory start CDATA #REQUIRED
39741 length CDATA #REQUIRED>
39743 <!ATTLIST tvar id CDATA #REQUIRED>
39746 @node Branch Trace Format
39747 @section Branch Trace Format
39748 @cindex branch trace format
39750 In order to display the branch trace of an inferior thread,
39751 @value{GDBN} needs to obtain the list of branches. This list is
39752 represented as list of sequential code blocks that are connected via
39753 branches. The code in each block has been executed sequentially.
39755 This list is obtained using the @samp{qXfer:btrace:read}
39756 (@pxref{qXfer btrace read}) packet and is an XML document.
39758 @value{GDBN} must be linked with the Expat library to support XML
39759 traceframe info discovery. @xref{Expat}.
39761 The top-level structure of the document is shown below:
39764 <?xml version="1.0"?>
39766 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
39767 "http://sourceware.org/gdb/gdb-btrace.dtd">
39776 A block of sequentially executed instructions starting at @var{begin}
39777 and ending at @var{end}:
39780 <block begin="@var{begin}" end="@var{end}"/>
39785 The formal DTD for the branch trace format is given below:
39788 <!ELEMENT btrace (block* | pt) >
39789 <!ATTLIST btrace version CDATA #FIXED "1.0">
39791 <!ELEMENT block EMPTY>
39792 <!ATTLIST block begin CDATA #REQUIRED
39793 end CDATA #REQUIRED>
39795 <!ELEMENT pt (pt-config?, raw?)>
39797 <!ELEMENT pt-config (cpu?)>
39799 <!ELEMENT cpu EMPTY>
39800 <!ATTLIST cpu vendor CDATA #REQUIRED
39801 family CDATA #REQUIRED
39802 model CDATA #REQUIRED
39803 stepping CDATA #REQUIRED>
39805 <!ELEMENT raw (#PCDATA)>
39808 @node Branch Trace Configuration Format
39809 @section Branch Trace Configuration Format
39810 @cindex branch trace configuration format
39812 For each inferior thread, @value{GDBN} can obtain the branch trace
39813 configuration using the @samp{qXfer:btrace-conf:read}
39814 (@pxref{qXfer btrace-conf read}) packet.
39816 The configuration describes the branch trace format and configuration
39817 settings for that format. The following information is described:
39821 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
39824 The size of the @acronym{BTS} ring buffer in bytes.
39827 This thread uses the @dfn{Intel(R) Processor Trace} (@acronym{Intel(R)
39831 The size of the @acronym{Intel(R) PT} ring buffer in bytes.
39835 @value{GDBN} must be linked with the Expat library to support XML
39836 branch trace configuration discovery. @xref{Expat}.
39838 The formal DTD for the branch trace configuration format is given below:
39841 <!ELEMENT btrace-conf (bts?, pt?)>
39842 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
39844 <!ELEMENT bts EMPTY>
39845 <!ATTLIST bts size CDATA #IMPLIED>
39847 <!ELEMENT pt EMPTY>
39848 <!ATTLIST pt size CDATA #IMPLIED>
39851 @include agentexpr.texi
39853 @node Target Descriptions
39854 @appendix Target Descriptions
39855 @cindex target descriptions
39857 One of the challenges of using @value{GDBN} to debug embedded systems
39858 is that there are so many minor variants of each processor
39859 architecture in use. It is common practice for vendors to start with
39860 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
39861 and then make changes to adapt it to a particular market niche. Some
39862 architectures have hundreds of variants, available from dozens of
39863 vendors. This leads to a number of problems:
39867 With so many different customized processors, it is difficult for
39868 the @value{GDBN} maintainers to keep up with the changes.
39870 Since individual variants may have short lifetimes or limited
39871 audiences, it may not be worthwhile to carry information about every
39872 variant in the @value{GDBN} source tree.
39874 When @value{GDBN} does support the architecture of the embedded system
39875 at hand, the task of finding the correct architecture name to give the
39876 @command{set architecture} command can be error-prone.
39879 To address these problems, the @value{GDBN} remote protocol allows a
39880 target system to not only identify itself to @value{GDBN}, but to
39881 actually describe its own features. This lets @value{GDBN} support
39882 processor variants it has never seen before --- to the extent that the
39883 descriptions are accurate, and that @value{GDBN} understands them.
39885 @value{GDBN} must be linked with the Expat library to support XML
39886 target descriptions. @xref{Expat}.
39889 * Retrieving Descriptions:: How descriptions are fetched from a target.
39890 * Target Description Format:: The contents of a target description.
39891 * Predefined Target Types:: Standard types available for target
39893 * Standard Target Features:: Features @value{GDBN} knows about.
39896 @node Retrieving Descriptions
39897 @section Retrieving Descriptions
39899 Target descriptions can be read from the target automatically, or
39900 specified by the user manually. The default behavior is to read the
39901 description from the target. @value{GDBN} retrieves it via the remote
39902 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
39903 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
39904 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
39905 XML document, of the form described in @ref{Target Description
39908 Alternatively, you can specify a file to read for the target description.
39909 If a file is set, the target will not be queried. The commands to
39910 specify a file are:
39913 @cindex set tdesc filename
39914 @item set tdesc filename @var{path}
39915 Read the target description from @var{path}.
39917 @cindex unset tdesc filename
39918 @item unset tdesc filename
39919 Do not read the XML target description from a file. @value{GDBN}
39920 will use the description supplied by the current target.
39922 @cindex show tdesc filename
39923 @item show tdesc filename
39924 Show the filename to read for a target description, if any.
39928 @node Target Description Format
39929 @section Target Description Format
39930 @cindex target descriptions, XML format
39932 A target description annex is an @uref{http://www.w3.org/XML/, XML}
39933 document which complies with the Document Type Definition provided in
39934 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
39935 means you can use generally available tools like @command{xmllint} to
39936 check that your feature descriptions are well-formed and valid.
39937 However, to help people unfamiliar with XML write descriptions for
39938 their targets, we also describe the grammar here.
39940 Target descriptions can identify the architecture of the remote target
39941 and (for some architectures) provide information about custom register
39942 sets. They can also identify the OS ABI of the remote target.
39943 @value{GDBN} can use this information to autoconfigure for your
39944 target, or to warn you if you connect to an unsupported target.
39946 Here is a simple target description:
39949 <target version="1.0">
39950 <architecture>i386:x86-64</architecture>
39955 This minimal description only says that the target uses
39956 the x86-64 architecture.
39958 A target description has the following overall form, with [ ] marking
39959 optional elements and @dots{} marking repeatable elements. The elements
39960 are explained further below.
39963 <?xml version="1.0"?>
39964 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39965 <target version="1.0">
39966 @r{[}@var{architecture}@r{]}
39967 @r{[}@var{osabi}@r{]}
39968 @r{[}@var{compatible}@r{]}
39969 @r{[}@var{feature}@dots{}@r{]}
39974 The description is generally insensitive to whitespace and line
39975 breaks, under the usual common-sense rules. The XML version
39976 declaration and document type declaration can generally be omitted
39977 (@value{GDBN} does not require them), but specifying them may be
39978 useful for XML validation tools. The @samp{version} attribute for
39979 @samp{<target>} may also be omitted, but we recommend
39980 including it; if future versions of @value{GDBN} use an incompatible
39981 revision of @file{gdb-target.dtd}, they will detect and report
39982 the version mismatch.
39984 @subsection Inclusion
39985 @cindex target descriptions, inclusion
39988 @cindex <xi:include>
39991 It can sometimes be valuable to split a target description up into
39992 several different annexes, either for organizational purposes, or to
39993 share files between different possible target descriptions. You can
39994 divide a description into multiple files by replacing any element of
39995 the target description with an inclusion directive of the form:
39998 <xi:include href="@var{document}"/>
40002 When @value{GDBN} encounters an element of this form, it will retrieve
40003 the named XML @var{document}, and replace the inclusion directive with
40004 the contents of that document. If the current description was read
40005 using @samp{qXfer}, then so will be the included document;
40006 @var{document} will be interpreted as the name of an annex. If the
40007 current description was read from a file, @value{GDBN} will look for
40008 @var{document} as a file in the same directory where it found the
40009 original description.
40011 @subsection Architecture
40012 @cindex <architecture>
40014 An @samp{<architecture>} element has this form:
40017 <architecture>@var{arch}</architecture>
40020 @var{arch} is one of the architectures from the set accepted by
40021 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40024 @cindex @code{<osabi>}
40026 This optional field was introduced in @value{GDBN} version 7.0.
40027 Previous versions of @value{GDBN} ignore it.
40029 An @samp{<osabi>} element has this form:
40032 <osabi>@var{abi-name}</osabi>
40035 @var{abi-name} is an OS ABI name from the same selection accepted by
40036 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40038 @subsection Compatible Architecture
40039 @cindex @code{<compatible>}
40041 This optional field was introduced in @value{GDBN} version 7.0.
40042 Previous versions of @value{GDBN} ignore it.
40044 A @samp{<compatible>} element has this form:
40047 <compatible>@var{arch}</compatible>
40050 @var{arch} is one of the architectures from the set accepted by
40051 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40053 A @samp{<compatible>} element is used to specify that the target
40054 is able to run binaries in some other than the main target architecture
40055 given by the @samp{<architecture>} element. For example, on the
40056 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40057 or @code{powerpc:common64}, but the system is able to run binaries
40058 in the @code{spu} architecture as well. The way to describe this
40059 capability with @samp{<compatible>} is as follows:
40062 <architecture>powerpc:common</architecture>
40063 <compatible>spu</compatible>
40066 @subsection Features
40069 Each @samp{<feature>} describes some logical portion of the target
40070 system. Features are currently used to describe available CPU
40071 registers and the types of their contents. A @samp{<feature>} element
40075 <feature name="@var{name}">
40076 @r{[}@var{type}@dots{}@r{]}
40082 Each feature's name should be unique within the description. The name
40083 of a feature does not matter unless @value{GDBN} has some special
40084 knowledge of the contents of that feature; if it does, the feature
40085 should have its standard name. @xref{Standard Target Features}.
40089 Any register's value is a collection of bits which @value{GDBN} must
40090 interpret. The default interpretation is a two's complement integer,
40091 but other types can be requested by name in the register description.
40092 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40093 Target Types}), and the description can define additional composite types.
40095 Each type element must have an @samp{id} attribute, which gives
40096 a unique (within the containing @samp{<feature>}) name to the type.
40097 Types must be defined before they are used.
40100 Some targets offer vector registers, which can be treated as arrays
40101 of scalar elements. These types are written as @samp{<vector>} elements,
40102 specifying the array element type, @var{type}, and the number of elements,
40106 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40110 If a register's value is usefully viewed in multiple ways, define it
40111 with a union type containing the useful representations. The
40112 @samp{<union>} element contains one or more @samp{<field>} elements,
40113 each of which has a @var{name} and a @var{type}:
40116 <union id="@var{id}">
40117 <field name="@var{name}" type="@var{type}"/>
40123 If a register's value is composed from several separate values, define
40124 it with a structure type. There are two forms of the @samp{<struct>}
40125 element; a @samp{<struct>} element must either contain only bitfields
40126 or contain no bitfields. If the structure contains only bitfields,
40127 its total size in bytes must be specified, each bitfield must have an
40128 explicit start and end, and bitfields are automatically assigned an
40129 integer type. The field's @var{start} should be less than or
40130 equal to its @var{end}, and zero represents the least significant bit.
40133 <struct id="@var{id}" size="@var{size}">
40134 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40139 If the structure contains no bitfields, then each field has an
40140 explicit type, and no implicit padding is added.
40143 <struct id="@var{id}">
40144 <field name="@var{name}" type="@var{type}"/>
40150 If a register's value is a series of single-bit flags, define it with
40151 a flags type. The @samp{<flags>} element has an explicit @var{size}
40152 and contains one or more @samp{<field>} elements. Each field has a
40153 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40157 <flags id="@var{id}" size="@var{size}">
40158 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40163 @subsection Registers
40166 Each register is represented as an element with this form:
40169 <reg name="@var{name}"
40170 bitsize="@var{size}"
40171 @r{[}regnum="@var{num}"@r{]}
40172 @r{[}save-restore="@var{save-restore}"@r{]}
40173 @r{[}type="@var{type}"@r{]}
40174 @r{[}group="@var{group}"@r{]}/>
40178 The components are as follows:
40183 The register's name; it must be unique within the target description.
40186 The register's size, in bits.
40189 The register's number. If omitted, a register's number is one greater
40190 than that of the previous register (either in the current feature or in
40191 a preceding feature); the first register in the target description
40192 defaults to zero. This register number is used to read or write
40193 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40194 packets, and registers appear in the @code{g} and @code{G} packets
40195 in order of increasing register number.
40198 Whether the register should be preserved across inferior function
40199 calls; this must be either @code{yes} or @code{no}. The default is
40200 @code{yes}, which is appropriate for most registers except for
40201 some system control registers; this is not related to the target's
40205 The type of the register. It may be a predefined type, a type
40206 defined in the current feature, or one of the special types @code{int}
40207 and @code{float}. @code{int} is an integer type of the correct size
40208 for @var{bitsize}, and @code{float} is a floating point type (in the
40209 architecture's normal floating point format) of the correct size for
40210 @var{bitsize}. The default is @code{int}.
40213 The register group to which this register belongs. It must
40214 be either @code{general}, @code{float}, or @code{vector}. If no
40215 @var{group} is specified, @value{GDBN} will not display the register
40216 in @code{info registers}.
40220 @node Predefined Target Types
40221 @section Predefined Target Types
40222 @cindex target descriptions, predefined types
40224 Type definitions in the self-description can build up composite types
40225 from basic building blocks, but can not define fundamental types. Instead,
40226 standard identifiers are provided by @value{GDBN} for the fundamental
40227 types. The currently supported types are:
40236 Signed integer types holding the specified number of bits.
40243 Unsigned integer types holding the specified number of bits.
40247 Pointers to unspecified code and data. The program counter and
40248 any dedicated return address register may be marked as code
40249 pointers; printing a code pointer converts it into a symbolic
40250 address. The stack pointer and any dedicated address registers
40251 may be marked as data pointers.
40254 Single precision IEEE floating point.
40257 Double precision IEEE floating point.
40260 The 12-byte extended precision format used by ARM FPA registers.
40263 The 10-byte extended precision format used by x87 registers.
40266 32bit @sc{eflags} register used by x86.
40269 32bit @sc{mxcsr} register used by x86.
40273 @node Standard Target Features
40274 @section Standard Target Features
40275 @cindex target descriptions, standard features
40277 A target description must contain either no registers or all the
40278 target's registers. If the description contains no registers, then
40279 @value{GDBN} will assume a default register layout, selected based on
40280 the architecture. If the description contains any registers, the
40281 default layout will not be used; the standard registers must be
40282 described in the target description, in such a way that @value{GDBN}
40283 can recognize them.
40285 This is accomplished by giving specific names to feature elements
40286 which contain standard registers. @value{GDBN} will look for features
40287 with those names and verify that they contain the expected registers;
40288 if any known feature is missing required registers, or if any required
40289 feature is missing, @value{GDBN} will reject the target
40290 description. You can add additional registers to any of the
40291 standard features --- @value{GDBN} will display them just as if
40292 they were added to an unrecognized feature.
40294 This section lists the known features and their expected contents.
40295 Sample XML documents for these features are included in the
40296 @value{GDBN} source tree, in the directory @file{gdb/features}.
40298 Names recognized by @value{GDBN} should include the name of the
40299 company or organization which selected the name, and the overall
40300 architecture to which the feature applies; so e.g.@: the feature
40301 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40303 The names of registers are not case sensitive for the purpose
40304 of recognizing standard features, but @value{GDBN} will only display
40305 registers using the capitalization used in the description.
40308 * AArch64 Features::
40311 * MicroBlaze Features::
40314 * Nios II Features::
40315 * PowerPC Features::
40316 * S/390 and System z Features::
40321 @node AArch64 Features
40322 @subsection AArch64 Features
40323 @cindex target descriptions, AArch64 features
40325 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
40326 targets. It should contain registers @samp{x0} through @samp{x30},
40327 @samp{sp}, @samp{pc}, and @samp{cpsr}.
40329 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
40330 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
40334 @subsection ARM Features
40335 @cindex target descriptions, ARM features
40337 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40339 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40340 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40342 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40343 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40344 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40347 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40348 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40350 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40351 it should contain at least registers @samp{wR0} through @samp{wR15} and
40352 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40353 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40355 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40356 should contain at least registers @samp{d0} through @samp{d15}. If
40357 they are present, @samp{d16} through @samp{d31} should also be included.
40358 @value{GDBN} will synthesize the single-precision registers from
40359 halves of the double-precision registers.
40361 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40362 need to contain registers; it instructs @value{GDBN} to display the
40363 VFP double-precision registers as vectors and to synthesize the
40364 quad-precision registers from pairs of double-precision registers.
40365 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40366 be present and include 32 double-precision registers.
40368 @node i386 Features
40369 @subsection i386 Features
40370 @cindex target descriptions, i386 features
40372 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40373 targets. It should describe the following registers:
40377 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40379 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40381 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40382 @samp{fs}, @samp{gs}
40384 @samp{st0} through @samp{st7}
40386 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40387 @samp{foseg}, @samp{fooff} and @samp{fop}
40390 The register sets may be different, depending on the target.
40392 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40393 describe registers:
40397 @samp{xmm0} through @samp{xmm7} for i386
40399 @samp{xmm0} through @samp{xmm15} for amd64
40404 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40405 @samp{org.gnu.gdb.i386.sse} feature. It should
40406 describe the upper 128 bits of @sc{ymm} registers:
40410 @samp{ymm0h} through @samp{ymm7h} for i386
40412 @samp{ymm0h} through @samp{ymm15h} for amd64
40415 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
40416 Memory Protection Extension (MPX). It should describe the following registers:
40420 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
40422 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
40425 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40426 describe a single register, @samp{orig_eax}.
40428 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
40429 @samp{org.gnu.gdb.i386.avx} feature. It should
40430 describe additional @sc{xmm} registers:
40434 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
40437 It should describe the upper 128 bits of additional @sc{ymm} registers:
40441 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
40445 describe the upper 256 bits of @sc{zmm} registers:
40449 @samp{zmm0h} through @samp{zmm7h} for i386.
40451 @samp{zmm0h} through @samp{zmm15h} for amd64.
40455 describe the additional @sc{zmm} registers:
40459 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
40462 @node MicroBlaze Features
40463 @subsection MicroBlaze Features
40464 @cindex target descriptions, MicroBlaze features
40466 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
40467 targets. It should contain registers @samp{r0} through @samp{r31},
40468 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
40469 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
40470 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
40472 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
40473 If present, it should contain registers @samp{rshr} and @samp{rslr}
40475 @node MIPS Features
40476 @subsection @acronym{MIPS} Features
40477 @cindex target descriptions, @acronym{MIPS} features
40479 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40480 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40481 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40484 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40485 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40486 registers. They may be 32-bit or 64-bit depending on the target.
40488 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40489 it may be optional in a future version of @value{GDBN}. It should
40490 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40491 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40493 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40494 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40495 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40496 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40498 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40499 contain a single register, @samp{restart}, which is used by the
40500 Linux kernel to control restartable syscalls.
40502 @node M68K Features
40503 @subsection M68K Features
40504 @cindex target descriptions, M68K features
40507 @item @samp{org.gnu.gdb.m68k.core}
40508 @itemx @samp{org.gnu.gdb.coldfire.core}
40509 @itemx @samp{org.gnu.gdb.fido.core}
40510 One of those features must be always present.
40511 The feature that is present determines which flavor of m68k is
40512 used. The feature that is present should contain registers
40513 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40514 @samp{sp}, @samp{ps} and @samp{pc}.
40516 @item @samp{org.gnu.gdb.coldfire.fp}
40517 This feature is optional. If present, it should contain registers
40518 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40522 @node Nios II Features
40523 @subsection Nios II Features
40524 @cindex target descriptions, Nios II features
40526 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
40527 targets. It should contain the 32 core registers (@samp{zero},
40528 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
40529 @samp{pc}, and the 16 control registers (@samp{status} through
40532 @node PowerPC Features
40533 @subsection PowerPC Features
40534 @cindex target descriptions, PowerPC features
40536 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40537 targets. It should contain registers @samp{r0} through @samp{r31},
40538 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40539 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40541 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40542 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40544 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40545 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40548 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40549 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40550 will combine these registers with the floating point registers
40551 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40552 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40553 through @samp{vs63}, the set of vector registers for POWER7.
40555 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40556 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40557 @samp{spefscr}. SPE targets should provide 32-bit registers in
40558 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40559 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40560 these to present registers @samp{ev0} through @samp{ev31} to the
40563 @node S/390 and System z Features
40564 @subsection S/390 and System z Features
40565 @cindex target descriptions, S/390 features
40566 @cindex target descriptions, System z features
40568 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
40569 System z targets. It should contain the PSW and the 16 general
40570 registers. In particular, System z targets should provide the 64-bit
40571 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
40572 S/390 targets should provide the 32-bit versions of these registers.
40573 A System z target that runs in 31-bit addressing mode should provide
40574 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
40575 register's upper halves @samp{r0h} through @samp{r15h}, and their
40576 lower halves @samp{r0l} through @samp{r15l}.
40578 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
40579 contain the 64-bit registers @samp{f0} through @samp{f15}, and
40582 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
40583 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
40585 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
40586 contain the register @samp{orig_r2}, which is 64-bit wide on System z
40587 targets and 32-bit otherwise. In addition, the feature may contain
40588 the @samp{last_break} register, whose width depends on the addressing
40589 mode, as well as the @samp{system_call} register, which is always
40592 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
40593 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
40594 @samp{atia}, and @samp{tr0} through @samp{tr15}.
40596 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
40597 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
40598 combined by @value{GDBN} with the floating point registers @samp{f0}
40599 through @samp{f15} to present the 128-bit wide vector registers
40600 @samp{v0} through @samp{v15}. In addition, this feature should
40601 contain the 128-bit wide vector registers @samp{v16} through
40604 @node TIC6x Features
40605 @subsection TMS320C6x Features
40606 @cindex target descriptions, TIC6x features
40607 @cindex target descriptions, TMS320C6x features
40608 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40609 targets. It should contain registers @samp{A0} through @samp{A15},
40610 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40612 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40613 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40614 through @samp{B31}.
40616 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40617 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40619 @node Operating System Information
40620 @appendix Operating System Information
40621 @cindex operating system information
40627 Users of @value{GDBN} often wish to obtain information about the state of
40628 the operating system running on the target---for example the list of
40629 processes, or the list of open files. This section describes the
40630 mechanism that makes it possible. This mechanism is similar to the
40631 target features mechanism (@pxref{Target Descriptions}), but focuses
40632 on a different aspect of target.
40634 Operating system information is retrived from the target via the
40635 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40636 read}). The object name in the request should be @samp{osdata}, and
40637 the @var{annex} identifies the data to be fetched.
40640 @appendixsection Process list
40641 @cindex operating system information, process list
40643 When requesting the process list, the @var{annex} field in the
40644 @samp{qXfer} request should be @samp{processes}. The returned data is
40645 an XML document. The formal syntax of this document is defined in
40646 @file{gdb/features/osdata.dtd}.
40648 An example document is:
40651 <?xml version="1.0"?>
40652 <!DOCTYPE target SYSTEM "osdata.dtd">
40653 <osdata type="processes">
40655 <column name="pid">1</column>
40656 <column name="user">root</column>
40657 <column name="command">/sbin/init</column>
40658 <column name="cores">1,2,3</column>
40663 Each item should include a column whose name is @samp{pid}. The value
40664 of that column should identify the process on the target. The
40665 @samp{user} and @samp{command} columns are optional, and will be
40666 displayed by @value{GDBN}. The @samp{cores} column, if present,
40667 should contain a comma-separated list of cores that this process
40668 is running on. Target may provide additional columns,
40669 which @value{GDBN} currently ignores.
40671 @node Trace File Format
40672 @appendix Trace File Format
40673 @cindex trace file format
40675 The trace file comes in three parts: a header, a textual description
40676 section, and a trace frame section with binary data.
40678 The header has the form @code{\x7fTRACE0\n}. The first byte is
40679 @code{0x7f} so as to indicate that the file contains binary data,
40680 while the @code{0} is a version number that may have different values
40683 The description section consists of multiple lines of @sc{ascii} text
40684 separated by newline characters (@code{0xa}). The lines may include a
40685 variety of optional descriptive or context-setting information, such
40686 as tracepoint definitions or register set size. @value{GDBN} will
40687 ignore any line that it does not recognize. An empty line marks the end
40690 @c FIXME add some specific types of data
40692 The trace frame section consists of a number of consecutive frames.
40693 Each frame begins with a two-byte tracepoint number, followed by a
40694 four-byte size giving the amount of data in the frame. The data in
40695 the frame consists of a number of blocks, each introduced by a
40696 character indicating its type (at least register, memory, and trace
40697 state variable). The data in this section is raw binary, not a
40698 hexadecimal or other encoding; its endianness matches the target's
40701 @c FIXME bi-arch may require endianness/arch info in description section
40704 @item R @var{bytes}
40705 Register block. The number and ordering of bytes matches that of a
40706 @code{g} packet in the remote protocol. Note that these are the
40707 actual bytes, in target order and @value{GDBN} register order, not a
40708 hexadecimal encoding.
40710 @item M @var{address} @var{length} @var{bytes}...
40711 Memory block. This is a contiguous block of memory, at the 8-byte
40712 address @var{address}, with a 2-byte length @var{length}, followed by
40713 @var{length} bytes.
40715 @item V @var{number} @var{value}
40716 Trace state variable block. This records the 8-byte signed value
40717 @var{value} of trace state variable numbered @var{number}.
40721 Future enhancements of the trace file format may include additional types
40724 @node Index Section Format
40725 @appendix @code{.gdb_index} section format
40726 @cindex .gdb_index section format
40727 @cindex index section format
40729 This section documents the index section that is created by @code{save
40730 gdb-index} (@pxref{Index Files}). The index section is
40731 DWARF-specific; some knowledge of DWARF is assumed in this
40734 The mapped index file format is designed to be directly
40735 @code{mmap}able on any architecture. In most cases, a datum is
40736 represented using a little-endian 32-bit integer value, called an
40737 @code{offset_type}. Big endian machines must byte-swap the values
40738 before using them. Exceptions to this rule are noted. The data is
40739 laid out such that alignment is always respected.
40741 A mapped index consists of several areas, laid out in order.
40745 The file header. This is a sequence of values, of @code{offset_type}
40746 unless otherwise noted:
40750 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
40751 Version 4 uses a different hashing function from versions 5 and 6.
40752 Version 6 includes symbols for inlined functions, whereas versions 4
40753 and 5 do not. Version 7 adds attributes to the CU indices in the
40754 symbol table. Version 8 specifies that symbols from DWARF type units
40755 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
40756 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
40758 @value{GDBN} will only read version 4, 5, or 6 indices
40759 by specifying @code{set use-deprecated-index-sections on}.
40760 GDB has a workaround for potentially broken version 7 indices so it is
40761 currently not flagged as deprecated.
40764 The offset, from the start of the file, of the CU list.
40767 The offset, from the start of the file, of the types CU list. Note
40768 that this area can be empty, in which case this offset will be equal
40769 to the next offset.
40772 The offset, from the start of the file, of the address area.
40775 The offset, from the start of the file, of the symbol table.
40778 The offset, from the start of the file, of the constant pool.
40782 The CU list. This is a sequence of pairs of 64-bit little-endian
40783 values, sorted by the CU offset. The first element in each pair is
40784 the offset of a CU in the @code{.debug_info} section. The second
40785 element in each pair is the length of that CU. References to a CU
40786 elsewhere in the map are done using a CU index, which is just the
40787 0-based index into this table. Note that if there are type CUs, then
40788 conceptually CUs and type CUs form a single list for the purposes of
40792 The types CU list. This is a sequence of triplets of 64-bit
40793 little-endian values. In a triplet, the first value is the CU offset,
40794 the second value is the type offset in the CU, and the third value is
40795 the type signature. The types CU list is not sorted.
40798 The address area. The address area consists of a sequence of address
40799 entries. Each address entry has three elements:
40803 The low address. This is a 64-bit little-endian value.
40806 The high address. This is a 64-bit little-endian value. Like
40807 @code{DW_AT_high_pc}, the value is one byte beyond the end.
40810 The CU index. This is an @code{offset_type} value.
40814 The symbol table. This is an open-addressed hash table. The size of
40815 the hash table is always a power of 2.
40817 Each slot in the hash table consists of a pair of @code{offset_type}
40818 values. The first value is the offset of the symbol's name in the
40819 constant pool. The second value is the offset of the CU vector in the
40822 If both values are 0, then this slot in the hash table is empty. This
40823 is ok because while 0 is a valid constant pool index, it cannot be a
40824 valid index for both a string and a CU vector.
40826 The hash value for a table entry is computed by applying an
40827 iterative hash function to the symbol's name. Starting with an
40828 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
40829 the string is incorporated into the hash using the formula depending on the
40834 The formula is @code{r = r * 67 + c - 113}.
40836 @item Versions 5 to 7
40837 The formula is @code{r = r * 67 + tolower (c) - 113}.
40840 The terminating @samp{\0} is not incorporated into the hash.
40842 The step size used in the hash table is computed via
40843 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
40844 value, and @samp{size} is the size of the hash table. The step size
40845 is used to find the next candidate slot when handling a hash
40848 The names of C@t{++} symbols in the hash table are canonicalized. We
40849 don't currently have a simple description of the canonicalization
40850 algorithm; if you intend to create new index sections, you must read
40854 The constant pool. This is simply a bunch of bytes. It is organized
40855 so that alignment is correct: CU vectors are stored first, followed by
40858 A CU vector in the constant pool is a sequence of @code{offset_type}
40859 values. The first value is the number of CU indices in the vector.
40860 Each subsequent value is the index and symbol attributes of a CU in
40861 the CU list. This element in the hash table is used to indicate which
40862 CUs define the symbol and how the symbol is used.
40863 See below for the format of each CU index+attributes entry.
40865 A string in the constant pool is zero-terminated.
40868 Attributes were added to CU index values in @code{.gdb_index} version 7.
40869 If a symbol has multiple uses within a CU then there is one
40870 CU index+attributes value for each use.
40872 The format of each CU index+attributes entry is as follows
40878 This is the index of the CU in the CU list.
40880 These bits are reserved for future purposes and must be zero.
40882 The kind of the symbol in the CU.
40886 This value is reserved and should not be used.
40887 By reserving zero the full @code{offset_type} value is backwards compatible
40888 with previous versions of the index.
40890 The symbol is a type.
40892 The symbol is a variable or an enum value.
40894 The symbol is a function.
40896 Any other kind of symbol.
40898 These values are reserved.
40902 This bit is zero if the value is global and one if it is static.
40904 The determination of whether a symbol is global or static is complicated.
40905 The authorative reference is the file @file{dwarf2read.c} in
40906 @value{GDBN} sources.
40910 This pseudo-code describes the computation of a symbol's kind and
40911 global/static attributes in the index.
40914 is_external = get_attribute (die, DW_AT_external);
40915 language = get_attribute (cu_die, DW_AT_language);
40918 case DW_TAG_typedef:
40919 case DW_TAG_base_type:
40920 case DW_TAG_subrange_type:
40924 case DW_TAG_enumerator:
40926 is_static = (language != CPLUS && language != JAVA);
40928 case DW_TAG_subprogram:
40930 is_static = ! (is_external || language == ADA);
40932 case DW_TAG_constant:
40934 is_static = ! is_external;
40936 case DW_TAG_variable:
40938 is_static = ! is_external;
40940 case DW_TAG_namespace:
40944 case DW_TAG_class_type:
40945 case DW_TAG_interface_type:
40946 case DW_TAG_structure_type:
40947 case DW_TAG_union_type:
40948 case DW_TAG_enumeration_type:
40950 is_static = (language != CPLUS && language != JAVA);
40958 @appendix Manual pages
40962 * gdb man:: The GNU Debugger man page
40963 * gdbserver man:: Remote Server for the GNU Debugger man page
40964 * gcore man:: Generate a core file of a running program
40965 * gdbinit man:: gdbinit scripts
40971 @c man title gdb The GNU Debugger
40973 @c man begin SYNOPSIS gdb
40974 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
40975 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
40976 [@option{-b}@w{ }@var{bps}]
40977 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
40978 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
40979 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
40980 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
40981 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
40984 @c man begin DESCRIPTION gdb
40985 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
40986 going on ``inside'' another program while it executes -- or what another
40987 program was doing at the moment it crashed.
40989 @value{GDBN} can do four main kinds of things (plus other things in support of
40990 these) to help you catch bugs in the act:
40994 Start your program, specifying anything that might affect its behavior.
40997 Make your program stop on specified conditions.
41000 Examine what has happened, when your program has stopped.
41003 Change things in your program, so you can experiment with correcting the
41004 effects of one bug and go on to learn about another.
41007 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41010 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41011 commands from the terminal until you tell it to exit with the @value{GDBN}
41012 command @code{quit}. You can get online help from @value{GDBN} itself
41013 by using the command @code{help}.
41015 You can run @code{gdb} with no arguments or options; but the most
41016 usual way to start @value{GDBN} is with one argument or two, specifying an
41017 executable program as the argument:
41023 You can also start with both an executable program and a core file specified:
41029 You can, instead, specify a process ID as a second argument, if you want
41030 to debug a running process:
41038 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41039 named @file{1234}; @value{GDBN} does check for a core file first).
41040 With option @option{-p} you can omit the @var{program} filename.
41042 Here are some of the most frequently needed @value{GDBN} commands:
41044 @c pod2man highlights the right hand side of the @item lines.
41046 @item break [@var{file}:]@var{functiop}
41047 Set a breakpoint at @var{function} (in @var{file}).
41049 @item run [@var{arglist}]
41050 Start your program (with @var{arglist}, if specified).
41053 Backtrace: display the program stack.
41055 @item print @var{expr}
41056 Display the value of an expression.
41059 Continue running your program (after stopping, e.g. at a breakpoint).
41062 Execute next program line (after stopping); step @emph{over} any
41063 function calls in the line.
41065 @item edit [@var{file}:]@var{function}
41066 look at the program line where it is presently stopped.
41068 @item list [@var{file}:]@var{function}
41069 type the text of the program in the vicinity of where it is presently stopped.
41072 Execute next program line (after stopping); step @emph{into} any
41073 function calls in the line.
41075 @item help [@var{name}]
41076 Show information about @value{GDBN} command @var{name}, or general information
41077 about using @value{GDBN}.
41080 Exit from @value{GDBN}.
41084 For full details on @value{GDBN},
41085 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41086 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41087 as the @code{gdb} entry in the @code{info} program.
41091 @c man begin OPTIONS gdb
41092 Any arguments other than options specify an executable
41093 file and core file (or process ID); that is, the first argument
41094 encountered with no
41095 associated option flag is equivalent to a @option{-se} option, and the second,
41096 if any, is equivalent to a @option{-c} option if it's the name of a file.
41098 both long and short forms; both are shown here. The long forms are also
41099 recognized if you truncate them, so long as enough of the option is
41100 present to be unambiguous. (If you prefer, you can flag option
41101 arguments with @option{+} rather than @option{-}, though we illustrate the
41102 more usual convention.)
41104 All the options and command line arguments you give are processed
41105 in sequential order. The order makes a difference when the @option{-x}
41111 List all options, with brief explanations.
41113 @item -symbols=@var{file}
41114 @itemx -s @var{file}
41115 Read symbol table from file @var{file}.
41118 Enable writing into executable and core files.
41120 @item -exec=@var{file}
41121 @itemx -e @var{file}
41122 Use file @var{file} as the executable file to execute when
41123 appropriate, and for examining pure data in conjunction with a core
41126 @item -se=@var{file}
41127 Read symbol table from file @var{file} and use it as the executable
41130 @item -core=@var{file}
41131 @itemx -c @var{file}
41132 Use file @var{file} as a core dump to examine.
41134 @item -command=@var{file}
41135 @itemx -x @var{file}
41136 Execute @value{GDBN} commands from file @var{file}.
41138 @item -ex @var{command}
41139 Execute given @value{GDBN} @var{command}.
41141 @item -directory=@var{directory}
41142 @itemx -d @var{directory}
41143 Add @var{directory} to the path to search for source files.
41146 Do not execute commands from @file{~/.gdbinit}.
41150 Do not execute commands from any @file{.gdbinit} initialization files.
41154 ``Quiet''. Do not print the introductory and copyright messages. These
41155 messages are also suppressed in batch mode.
41158 Run in batch mode. Exit with status @code{0} after processing all the command
41159 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41160 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41161 commands in the command files.
41163 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41164 download and run a program on another computer; in order to make this
41165 more useful, the message
41168 Program exited normally.
41172 (which is ordinarily issued whenever a program running under @value{GDBN} control
41173 terminates) is not issued when running in batch mode.
41175 @item -cd=@var{directory}
41176 Run @value{GDBN} using @var{directory} as its working directory,
41177 instead of the current directory.
41181 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41182 @value{GDBN} to output the full file name and line number in a standard,
41183 recognizable fashion each time a stack frame is displayed (which
41184 includes each time the program stops). This recognizable format looks
41185 like two @samp{\032} characters, followed by the file name, line number
41186 and character position separated by colons, and a newline. The
41187 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41188 characters as a signal to display the source code for the frame.
41191 Set the line speed (baud rate or bits per second) of any serial
41192 interface used by @value{GDBN} for remote debugging.
41194 @item -tty=@var{device}
41195 Run using @var{device} for your program's standard input and output.
41199 @c man begin SEEALSO gdb
41201 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41202 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41203 documentation are properly installed at your site, the command
41210 should give you access to the complete manual.
41212 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41213 Richard M. Stallman and Roland H. Pesch, July 1991.
41217 @node gdbserver man
41218 @heading gdbserver man
41220 @c man title gdbserver Remote Server for the GNU Debugger
41222 @c man begin SYNOPSIS gdbserver
41223 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41225 gdbserver --attach @var{comm} @var{pid}
41227 gdbserver --multi @var{comm}
41231 @c man begin DESCRIPTION gdbserver
41232 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41233 than the one which is running the program being debugged.
41236 @subheading Usage (server (target) side)
41239 Usage (server (target) side):
41242 First, you need to have a copy of the program you want to debug put onto
41243 the target system. The program can be stripped to save space if needed, as
41244 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41245 the @value{GDBN} running on the host system.
41247 To use the server, you log on to the target system, and run the @command{gdbserver}
41248 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41249 your program, and (c) its arguments. The general syntax is:
41252 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41255 For example, using a serial port, you might say:
41259 @c @file would wrap it as F</dev/com1>.
41260 target> gdbserver /dev/com1 emacs foo.txt
41263 target> gdbserver @file{/dev/com1} emacs foo.txt
41267 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41268 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41269 waits patiently for the host @value{GDBN} to communicate with it.
41271 To use a TCP connection, you could say:
41274 target> gdbserver host:2345 emacs foo.txt
41277 This says pretty much the same thing as the last example, except that we are
41278 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
41279 that we are expecting to see a TCP connection from @code{host} to local TCP port
41280 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
41281 want for the port number as long as it does not conflict with any existing TCP
41282 ports on the target system. This same port number must be used in the host
41283 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
41284 you chose a port number that conflicts with another service, @command{gdbserver} will
41285 print an error message and exit.
41287 @command{gdbserver} can also attach to running programs.
41288 This is accomplished via the @option{--attach} argument. The syntax is:
41291 target> gdbserver --attach @var{comm} @var{pid}
41294 @var{pid} is the process ID of a currently running process. It isn't
41295 necessary to point @command{gdbserver} at a binary for the running process.
41297 To start @code{gdbserver} without supplying an initial command to run
41298 or process ID to attach, use the @option{--multi} command line option.
41299 In such case you should connect using @kbd{target extended-remote} to start
41300 the program you want to debug.
41303 target> gdbserver --multi @var{comm}
41307 @subheading Usage (host side)
41313 You need an unstripped copy of the target program on your host system, since
41314 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
41315 would, with the target program as the first argument. (You may need to use the
41316 @option{--baud} option if the serial line is running at anything except 9600 baud.)
41317 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
41318 new command you need to know about is @code{target remote}
41319 (or @code{target extended-remote}). Its argument is either
41320 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
41321 descriptor. For example:
41325 @c @file would wrap it as F</dev/ttyb>.
41326 (gdb) target remote /dev/ttyb
41329 (gdb) target remote @file{/dev/ttyb}
41334 communicates with the server via serial line @file{/dev/ttyb}, and:
41337 (gdb) target remote the-target:2345
41341 communicates via a TCP connection to port 2345 on host `the-target', where
41342 you previously started up @command{gdbserver} with the same port number. Note that for
41343 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
41344 command, otherwise you may get an error that looks something like
41345 `Connection refused'.
41347 @command{gdbserver} can also debug multiple inferiors at once,
41350 the @value{GDBN} manual in node @code{Inferiors and Programs}
41351 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
41354 @ref{Inferiors and Programs}.
41356 In such case use the @code{extended-remote} @value{GDBN} command variant:
41359 (gdb) target extended-remote the-target:2345
41362 The @command{gdbserver} option @option{--multi} may or may not be used in such
41366 @c man begin OPTIONS gdbserver
41367 There are three different modes for invoking @command{gdbserver}:
41372 Debug a specific program specified by its program name:
41375 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41378 The @var{comm} parameter specifies how should the server communicate
41379 with @value{GDBN}; it is either a device name (to use a serial line),
41380 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
41381 stdin/stdout of @code{gdbserver}. Specify the name of the program to
41382 debug in @var{prog}. Any remaining arguments will be passed to the
41383 program verbatim. When the program exits, @value{GDBN} will close the
41384 connection, and @code{gdbserver} will exit.
41387 Debug a specific program by specifying the process ID of a running
41391 gdbserver --attach @var{comm} @var{pid}
41394 The @var{comm} parameter is as described above. Supply the process ID
41395 of a running program in @var{pid}; @value{GDBN} will do everything
41396 else. Like with the previous mode, when the process @var{pid} exits,
41397 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
41400 Multi-process mode -- debug more than one program/process:
41403 gdbserver --multi @var{comm}
41406 In this mode, @value{GDBN} can instruct @command{gdbserver} which
41407 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
41408 close the connection when a process being debugged exits, so you can
41409 debug several processes in the same session.
41412 In each of the modes you may specify these options:
41417 List all options, with brief explanations.
41420 This option causes @command{gdbserver} to print its version number and exit.
41423 @command{gdbserver} will attach to a running program. The syntax is:
41426 target> gdbserver --attach @var{comm} @var{pid}
41429 @var{pid} is the process ID of a currently running process. It isn't
41430 necessary to point @command{gdbserver} at a binary for the running process.
41433 To start @code{gdbserver} without supplying an initial command to run
41434 or process ID to attach, use this command line option.
41435 Then you can connect using @kbd{target extended-remote} and start
41436 the program you want to debug. The syntax is:
41439 target> gdbserver --multi @var{comm}
41443 Instruct @code{gdbserver} to display extra status information about the debugging
41445 This option is intended for @code{gdbserver} development and for bug reports to
41448 @item --remote-debug
41449 Instruct @code{gdbserver} to display remote protocol debug output.
41450 This option is intended for @code{gdbserver} development and for bug reports to
41453 @item --debug-format=option1@r{[},option2,...@r{]}
41454 Instruct @code{gdbserver} to include extra information in each line
41455 of debugging output.
41456 @xref{Other Command-Line Arguments for gdbserver}.
41459 Specify a wrapper to launch programs
41460 for debugging. The option should be followed by the name of the
41461 wrapper, then any command-line arguments to pass to the wrapper, then
41462 @kbd{--} indicating the end of the wrapper arguments.
41465 By default, @command{gdbserver} keeps the listening TCP port open, so that
41466 additional connections are possible. However, if you start @code{gdbserver}
41467 with the @option{--once} option, it will stop listening for any further
41468 connection attempts after connecting to the first @value{GDBN} session.
41470 @c --disable-packet is not documented for users.
41472 @c --disable-randomization and --no-disable-randomization are superseded by
41473 @c QDisableRandomization.
41478 @c man begin SEEALSO gdbserver
41480 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41481 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41482 documentation are properly installed at your site, the command
41488 should give you access to the complete manual.
41490 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41491 Richard M. Stallman and Roland H. Pesch, July 1991.
41498 @c man title gcore Generate a core file of a running program
41501 @c man begin SYNOPSIS gcore
41502 gcore [-o @var{filename}] @var{pid}
41506 @c man begin DESCRIPTION gcore
41507 Generate a core dump of a running program with process ID @var{pid}.
41508 Produced file is equivalent to a kernel produced core file as if the process
41509 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
41510 limit). Unlike after a crash, after @command{gcore} the program remains
41511 running without any change.
41514 @c man begin OPTIONS gcore
41516 @item -o @var{filename}
41517 The optional argument
41518 @var{filename} specifies the file name where to put the core dump.
41519 If not specified, the file name defaults to @file{core.@var{pid}},
41520 where @var{pid} is the running program process ID.
41524 @c man begin SEEALSO gcore
41526 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41527 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41528 documentation are properly installed at your site, the command
41535 should give you access to the complete manual.
41537 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41538 Richard M. Stallman and Roland H. Pesch, July 1991.
41545 @c man title gdbinit GDB initialization scripts
41548 @c man begin SYNOPSIS gdbinit
41549 @ifset SYSTEM_GDBINIT
41550 @value{SYSTEM_GDBINIT}
41559 @c man begin DESCRIPTION gdbinit
41560 These files contain @value{GDBN} commands to automatically execute during
41561 @value{GDBN} startup. The lines of contents are canned sequences of commands,
41564 the @value{GDBN} manual in node @code{Sequences}
41565 -- shell command @code{info -f gdb -n Sequences}.
41571 Please read more in
41573 the @value{GDBN} manual in node @code{Startup}
41574 -- shell command @code{info -f gdb -n Startup}.
41581 @ifset SYSTEM_GDBINIT
41582 @item @value{SYSTEM_GDBINIT}
41584 @ifclear SYSTEM_GDBINIT
41585 @item (not enabled with @code{--with-system-gdbinit} during compilation)
41587 System-wide initialization file. It is executed unless user specified
41588 @value{GDBN} option @code{-nx} or @code{-n}.
41591 the @value{GDBN} manual in node @code{System-wide configuration}
41592 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
41595 @ref{System-wide configuration}.
41599 User initialization file. It is executed unless user specified
41600 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
41603 Initialization file for current directory. It may need to be enabled with
41604 @value{GDBN} security command @code{set auto-load local-gdbinit}.
41607 the @value{GDBN} manual in node @code{Init File in the Current Directory}
41608 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
41611 @ref{Init File in the Current Directory}.
41616 @c man begin SEEALSO gdbinit
41618 gdb(1), @code{info -f gdb -n Startup}
41620 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41621 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41622 documentation are properly installed at your site, the command
41628 should give you access to the complete manual.
41630 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41631 Richard M. Stallman and Roland H. Pesch, July 1991.
41637 @node GNU Free Documentation License
41638 @appendix GNU Free Documentation License
41641 @node Concept Index
41642 @unnumbered Concept Index
41646 @node Command and Variable Index
41647 @unnumbered Command, Variable, and Function Index
41652 % I think something like @@colophon should be in texinfo. In the
41654 \long\def\colophon{\hbox to0pt{}\vfill
41655 \centerline{The body of this manual is set in}
41656 \centerline{\fontname\tenrm,}
41657 \centerline{with headings in {\bf\fontname\tenbf}}
41658 \centerline{and examples in {\tt\fontname\tentt}.}
41659 \centerline{{\it\fontname\tenit\/},}
41660 \centerline{{\bf\fontname\tenbf}, and}
41661 \centerline{{\sl\fontname\tensl\/}}
41662 \centerline{are used for emphasis.}\vfill}
41664 % Blame: doc@@cygnus.com, 1991.