1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2015 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2015 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2015 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
545 @chapter A Sample @value{GDBN} Session
547 You can use this manual at your leisure to read all about @value{GDBN}.
548 However, a handful of commands are enough to get started using the
549 debugger. This chapter illustrates those commands.
552 In this sample session, we emphasize user input like this: @b{input},
553 to make it easier to pick out from the surrounding output.
556 @c FIXME: this example may not be appropriate for some configs, where
557 @c FIXME...primary interest is in remote use.
559 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
560 processor) exhibits the following bug: sometimes, when we change its
561 quote strings from the default, the commands used to capture one macro
562 definition within another stop working. In the following short @code{m4}
563 session, we define a macro @code{foo} which expands to @code{0000}; we
564 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
565 same thing. However, when we change the open quote string to
566 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
567 procedure fails to define a new synonym @code{baz}:
576 @b{define(bar,defn(`foo'))}
580 @b{changequote(<QUOTE>,<UNQUOTE>)}
582 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
585 m4: End of input: 0: fatal error: EOF in string
589 Let us use @value{GDBN} to try to see what is going on.
592 $ @b{@value{GDBP} m4}
593 @c FIXME: this falsifies the exact text played out, to permit smallbook
594 @c FIXME... format to come out better.
595 @value{GDBN} is free software and you are welcome to distribute copies
596 of it under certain conditions; type "show copying" to see
598 There is absolutely no warranty for @value{GDBN}; type "show warranty"
601 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
606 @value{GDBN} reads only enough symbol data to know where to find the
607 rest when needed; as a result, the first prompt comes up very quickly.
608 We now tell @value{GDBN} to use a narrower display width than usual, so
609 that examples fit in this manual.
612 (@value{GDBP}) @b{set width 70}
616 We need to see how the @code{m4} built-in @code{changequote} works.
617 Having looked at the source, we know the relevant subroutine is
618 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
619 @code{break} command.
622 (@value{GDBP}) @b{break m4_changequote}
623 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
627 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
628 control; as long as control does not reach the @code{m4_changequote}
629 subroutine, the program runs as usual:
632 (@value{GDBP}) @b{run}
633 Starting program: /work/Editorial/gdb/gnu/m4/m4
641 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
642 suspends execution of @code{m4}, displaying information about the
643 context where it stops.
646 @b{changequote(<QUOTE>,<UNQUOTE>)}
648 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
650 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
654 Now we use the command @code{n} (@code{next}) to advance execution to
655 the next line of the current function.
659 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
664 @code{set_quotes} looks like a promising subroutine. We can go into it
665 by using the command @code{s} (@code{step}) instead of @code{next}.
666 @code{step} goes to the next line to be executed in @emph{any}
667 subroutine, so it steps into @code{set_quotes}.
671 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
673 530 if (lquote != def_lquote)
677 The display that shows the subroutine where @code{m4} is now
678 suspended (and its arguments) is called a stack frame display. It
679 shows a summary of the stack. We can use the @code{backtrace}
680 command (which can also be spelled @code{bt}), to see where we are
681 in the stack as a whole: the @code{backtrace} command displays a
682 stack frame for each active subroutine.
685 (@value{GDBP}) @b{bt}
686 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
688 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
690 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
691 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
693 #4 0x79dc in expand_input () at macro.c:40
694 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
698 We step through a few more lines to see what happens. The first two
699 times, we can use @samp{s}; the next two times we use @code{n} to avoid
700 falling into the @code{xstrdup} subroutine.
704 0x3b5c 532 if (rquote != def_rquote)
706 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
707 def_lquote : xstrdup(lq);
709 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
712 538 len_lquote = strlen(rquote);
716 The last line displayed looks a little odd; we can examine the variables
717 @code{lquote} and @code{rquote} to see if they are in fact the new left
718 and right quotes we specified. We use the command @code{p}
719 (@code{print}) to see their values.
722 (@value{GDBP}) @b{p lquote}
723 $1 = 0x35d40 "<QUOTE>"
724 (@value{GDBP}) @b{p rquote}
725 $2 = 0x35d50 "<UNQUOTE>"
729 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
730 To look at some context, we can display ten lines of source
731 surrounding the current line with the @code{l} (@code{list}) command.
737 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
739 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
742 538 len_lquote = strlen(rquote);
743 539 len_rquote = strlen(lquote);
750 Let us step past the two lines that set @code{len_lquote} and
751 @code{len_rquote}, and then examine the values of those variables.
755 539 len_rquote = strlen(lquote);
758 (@value{GDBP}) @b{p len_lquote}
760 (@value{GDBP}) @b{p len_rquote}
765 That certainly looks wrong, assuming @code{len_lquote} and
766 @code{len_rquote} are meant to be the lengths of @code{lquote} and
767 @code{rquote} respectively. We can set them to better values using
768 the @code{p} command, since it can print the value of
769 any expression---and that expression can include subroutine calls and
773 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
775 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
780 Is that enough to fix the problem of using the new quotes with the
781 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
782 executing with the @code{c} (@code{continue}) command, and then try the
783 example that caused trouble initially:
789 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
796 Success! The new quotes now work just as well as the default ones. The
797 problem seems to have been just the two typos defining the wrong
798 lengths. We allow @code{m4} exit by giving it an EOF as input:
802 Program exited normally.
806 The message @samp{Program exited normally.} is from @value{GDBN}; it
807 indicates @code{m4} has finished executing. We can end our @value{GDBN}
808 session with the @value{GDBN} @code{quit} command.
811 (@value{GDBP}) @b{quit}
815 @chapter Getting In and Out of @value{GDBN}
817 This chapter discusses how to start @value{GDBN}, and how to get out of it.
821 type @samp{@value{GDBP}} to start @value{GDBN}.
823 type @kbd{quit} or @kbd{Ctrl-d} to exit.
827 * Invoking GDB:: How to start @value{GDBN}
828 * Quitting GDB:: How to quit @value{GDBN}
829 * Shell Commands:: How to use shell commands inside @value{GDBN}
830 * Logging Output:: How to log @value{GDBN}'s output to a file
834 @section Invoking @value{GDBN}
836 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
837 @value{GDBN} reads commands from the terminal until you tell it to exit.
839 You can also run @code{@value{GDBP}} with a variety of arguments and options,
840 to specify more of your debugging environment at the outset.
842 The command-line options described here are designed
843 to cover a variety of situations; in some environments, some of these
844 options may effectively be unavailable.
846 The most usual way to start @value{GDBN} is with one argument,
847 specifying an executable program:
850 @value{GDBP} @var{program}
854 You can also start with both an executable program and a core file
858 @value{GDBP} @var{program} @var{core}
861 You can, instead, specify a process ID as a second argument, if you want
862 to debug a running process:
865 @value{GDBP} @var{program} 1234
869 would attach @value{GDBN} to process @code{1234} (unless you also have a file
870 named @file{1234}; @value{GDBN} does check for a core file first).
872 Taking advantage of the second command-line argument requires a fairly
873 complete operating system; when you use @value{GDBN} as a remote
874 debugger attached to a bare board, there may not be any notion of
875 ``process'', and there is often no way to get a core dump. @value{GDBN}
876 will warn you if it is unable to attach or to read core dumps.
878 You can optionally have @code{@value{GDBP}} pass any arguments after the
879 executable file to the inferior using @code{--args}. This option stops
882 @value{GDBP} --args gcc -O2 -c foo.c
884 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
885 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
887 You can run @code{@value{GDBP}} without printing the front material, which describes
888 @value{GDBN}'s non-warranty, by specifying @code{--silent}
889 (or @code{-q}/@code{--quiet}):
892 @value{GDBP} --silent
896 You can further control how @value{GDBN} starts up by using command-line
897 options. @value{GDBN} itself can remind you of the options available.
907 to display all available options and briefly describe their use
908 (@samp{@value{GDBP} -h} is a shorter equivalent).
910 All options and command line arguments you give are processed
911 in sequential order. The order makes a difference when the
912 @samp{-x} option is used.
916 * File Options:: Choosing files
917 * Mode Options:: Choosing modes
918 * Startup:: What @value{GDBN} does during startup
922 @subsection Choosing Files
924 When @value{GDBN} starts, it reads any arguments other than options as
925 specifying an executable file and core file (or process ID). This is
926 the same as if the arguments were specified by the @samp{-se} and
927 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
928 first argument that does not have an associated option flag as
929 equivalent to the @samp{-se} option followed by that argument; and the
930 second argument that does not have an associated option flag, if any, as
931 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
932 If the second argument begins with a decimal digit, @value{GDBN} will
933 first attempt to attach to it as a process, and if that fails, attempt
934 to open it as a corefile. If you have a corefile whose name begins with
935 a digit, you can prevent @value{GDBN} from treating it as a pid by
936 prefixing it with @file{./}, e.g.@: @file{./12345}.
938 If @value{GDBN} has not been configured to included core file support,
939 such as for most embedded targets, then it will complain about a second
940 argument and ignore it.
942 Many options have both long and short forms; both are shown in the
943 following list. @value{GDBN} also recognizes the long forms if you truncate
944 them, so long as enough of the option is present to be unambiguous.
945 (If you prefer, you can flag option arguments with @samp{--} rather
946 than @samp{-}, though we illustrate the more usual convention.)
948 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
949 @c way, both those who look for -foo and --foo in the index, will find
953 @item -symbols @var{file}
955 @cindex @code{--symbols}
957 Read symbol table from file @var{file}.
959 @item -exec @var{file}
961 @cindex @code{--exec}
963 Use file @var{file} as the executable file to execute when appropriate,
964 and for examining pure data in conjunction with a core dump.
968 Read symbol table from file @var{file} and use it as the executable
971 @item -core @var{file}
973 @cindex @code{--core}
975 Use file @var{file} as a core dump to examine.
977 @item -pid @var{number}
978 @itemx -p @var{number}
981 Connect to process ID @var{number}, as with the @code{attach} command.
983 @item -command @var{file}
985 @cindex @code{--command}
987 Execute commands from file @var{file}. The contents of this file is
988 evaluated exactly as the @code{source} command would.
989 @xref{Command Files,, Command files}.
991 @item -eval-command @var{command}
992 @itemx -ex @var{command}
993 @cindex @code{--eval-command}
995 Execute a single @value{GDBN} command.
997 This option may be used multiple times to call multiple commands. It may
998 also be interleaved with @samp{-command} as required.
1001 @value{GDBP} -ex 'target sim' -ex 'load' \
1002 -x setbreakpoints -ex 'run' a.out
1005 @item -init-command @var{file}
1006 @itemx -ix @var{file}
1007 @cindex @code{--init-command}
1009 Execute commands from file @var{file} before loading the inferior (but
1010 after loading gdbinit files).
1013 @item -init-eval-command @var{command}
1014 @itemx -iex @var{command}
1015 @cindex @code{--init-eval-command}
1017 Execute a single @value{GDBN} command before loading the inferior (but
1018 after loading gdbinit files).
1021 @item -directory @var{directory}
1022 @itemx -d @var{directory}
1023 @cindex @code{--directory}
1025 Add @var{directory} to the path to search for source and script files.
1029 @cindex @code{--readnow}
1031 Read each symbol file's entire symbol table immediately, rather than
1032 the default, which is to read it incrementally as it is needed.
1033 This makes startup slower, but makes future operations faster.
1038 @subsection Choosing Modes
1040 You can run @value{GDBN} in various alternative modes---for example, in
1041 batch mode or quiet mode.
1049 Do not execute commands found in any initialization file.
1050 There are three init files, loaded in the following order:
1053 @item @file{system.gdbinit}
1054 This is the system-wide init file.
1055 Its location is specified with the @code{--with-system-gdbinit}
1056 configure option (@pxref{System-wide configuration}).
1057 It is loaded first when @value{GDBN} starts, before command line options
1058 have been processed.
1059 @item @file{~/.gdbinit}
1060 This is the init file in your home directory.
1061 It is loaded next, after @file{system.gdbinit}, and before
1062 command options have been processed.
1063 @item @file{./.gdbinit}
1064 This is the init file in the current directory.
1065 It is loaded last, after command line options other than @code{-x} and
1066 @code{-ex} have been processed. Command line options @code{-x} and
1067 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1070 For further documentation on startup processing, @xref{Startup}.
1071 For documentation on how to write command files,
1072 @xref{Command Files,,Command Files}.
1077 Do not execute commands found in @file{~/.gdbinit}, the init file
1078 in your home directory.
1084 @cindex @code{--quiet}
1085 @cindex @code{--silent}
1087 ``Quiet''. Do not print the introductory and copyright messages. These
1088 messages are also suppressed in batch mode.
1091 @cindex @code{--batch}
1092 Run in batch mode. Exit with status @code{0} after processing all the
1093 command files specified with @samp{-x} (and all commands from
1094 initialization files, if not inhibited with @samp{-n}). Exit with
1095 nonzero status if an error occurs in executing the @value{GDBN} commands
1096 in the command files. Batch mode also disables pagination, sets unlimited
1097 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1098 off} were in effect (@pxref{Messages/Warnings}).
1100 Batch mode may be useful for running @value{GDBN} as a filter, for
1101 example to download and run a program on another computer; in order to
1102 make this more useful, the message
1105 Program exited normally.
1109 (which is ordinarily issued whenever a program running under
1110 @value{GDBN} control terminates) is not issued when running in batch
1114 @cindex @code{--batch-silent}
1115 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1116 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1117 unaffected). This is much quieter than @samp{-silent} and would be useless
1118 for an interactive session.
1120 This is particularly useful when using targets that give @samp{Loading section}
1121 messages, for example.
1123 Note that targets that give their output via @value{GDBN}, as opposed to
1124 writing directly to @code{stdout}, will also be made silent.
1126 @item -return-child-result
1127 @cindex @code{--return-child-result}
1128 The return code from @value{GDBN} will be the return code from the child
1129 process (the process being debugged), with the following exceptions:
1133 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1134 internal error. In this case the exit code is the same as it would have been
1135 without @samp{-return-child-result}.
1137 The user quits with an explicit value. E.g., @samp{quit 1}.
1139 The child process never runs, or is not allowed to terminate, in which case
1140 the exit code will be -1.
1143 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1144 when @value{GDBN} is being used as a remote program loader or simulator
1149 @cindex @code{--nowindows}
1151 ``No windows''. If @value{GDBN} comes with a graphical user interface
1152 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1153 interface. If no GUI is available, this option has no effect.
1157 @cindex @code{--windows}
1159 If @value{GDBN} includes a GUI, then this option requires it to be
1162 @item -cd @var{directory}
1164 Run @value{GDBN} using @var{directory} as its working directory,
1165 instead of the current directory.
1167 @item -data-directory @var{directory}
1168 @itemx -D @var{directory}
1169 @cindex @code{--data-directory}
1171 Run @value{GDBN} using @var{directory} as its data directory.
1172 The data directory is where @value{GDBN} searches for its
1173 auxiliary files. @xref{Data Files}.
1177 @cindex @code{--fullname}
1179 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1180 subprocess. It tells @value{GDBN} to output the full file name and line
1181 number in a standard, recognizable fashion each time a stack frame is
1182 displayed (which includes each time your program stops). This
1183 recognizable format looks like two @samp{\032} characters, followed by
1184 the file name, line number and character position separated by colons,
1185 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1186 @samp{\032} characters as a signal to display the source code for the
1189 @item -annotate @var{level}
1190 @cindex @code{--annotate}
1191 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1192 effect is identical to using @samp{set annotate @var{level}}
1193 (@pxref{Annotations}). The annotation @var{level} controls how much
1194 information @value{GDBN} prints together with its prompt, values of
1195 expressions, source lines, and other types of output. Level 0 is the
1196 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1197 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1198 that control @value{GDBN}, and level 2 has been deprecated.
1200 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1204 @cindex @code{--args}
1205 Change interpretation of command line so that arguments following the
1206 executable file are passed as command line arguments to the inferior.
1207 This option stops option processing.
1209 @item -baud @var{bps}
1211 @cindex @code{--baud}
1213 Set the line speed (baud rate or bits per second) of any serial
1214 interface used by @value{GDBN} for remote debugging.
1216 @item -l @var{timeout}
1218 Set the timeout (in seconds) of any communication used by @value{GDBN}
1219 for remote debugging.
1221 @item -tty @var{device}
1222 @itemx -t @var{device}
1223 @cindex @code{--tty}
1225 Run using @var{device} for your program's standard input and output.
1226 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1228 @c resolve the situation of these eventually
1230 @cindex @code{--tui}
1231 Activate the @dfn{Text User Interface} when starting. The Text User
1232 Interface manages several text windows on the terminal, showing
1233 source, assembly, registers and @value{GDBN} command outputs
1234 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1235 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1236 Using @value{GDBN} under @sc{gnu} Emacs}).
1238 @item -interpreter @var{interp}
1239 @cindex @code{--interpreter}
1240 Use the interpreter @var{interp} for interface with the controlling
1241 program or device. This option is meant to be set by programs which
1242 communicate with @value{GDBN} using it as a back end.
1243 @xref{Interpreters, , Command Interpreters}.
1245 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1246 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1247 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1248 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1249 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1250 @sc{gdb/mi} interfaces are no longer supported.
1253 @cindex @code{--write}
1254 Open the executable and core files for both reading and writing. This
1255 is equivalent to the @samp{set write on} command inside @value{GDBN}
1259 @cindex @code{--statistics}
1260 This option causes @value{GDBN} to print statistics about time and
1261 memory usage after it completes each command and returns to the prompt.
1264 @cindex @code{--version}
1265 This option causes @value{GDBN} to print its version number and
1266 no-warranty blurb, and exit.
1268 @item -configuration
1269 @cindex @code{--configuration}
1270 This option causes @value{GDBN} to print details about its build-time
1271 configuration parameters, and then exit. These details can be
1272 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1277 @subsection What @value{GDBN} Does During Startup
1278 @cindex @value{GDBN} startup
1280 Here's the description of what @value{GDBN} does during session startup:
1284 Sets up the command interpreter as specified by the command line
1285 (@pxref{Mode Options, interpreter}).
1289 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1290 used when building @value{GDBN}; @pxref{System-wide configuration,
1291 ,System-wide configuration and settings}) and executes all the commands in
1294 @anchor{Home Directory Init File}
1296 Reads the init file (if any) in your home directory@footnote{On
1297 DOS/Windows systems, the home directory is the one pointed to by the
1298 @code{HOME} environment variable.} and executes all the commands in
1301 @anchor{Option -init-eval-command}
1303 Executes commands and command files specified by the @samp{-iex} and
1304 @samp{-ix} options in their specified order. Usually you should use the
1305 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1306 settings before @value{GDBN} init files get executed and before inferior
1310 Processes command line options and operands.
1312 @anchor{Init File in the Current Directory during Startup}
1314 Reads and executes the commands from init file (if any) in the current
1315 working directory as long as @samp{set auto-load local-gdbinit} is set to
1316 @samp{on} (@pxref{Init File in the Current Directory}).
1317 This is only done if the current directory is
1318 different from your home directory. Thus, you can have more than one
1319 init file, one generic in your home directory, and another, specific
1320 to the program you are debugging, in the directory where you invoke
1324 If the command line specified a program to debug, or a process to
1325 attach to, or a core file, @value{GDBN} loads any auto-loaded
1326 scripts provided for the program or for its loaded shared libraries.
1327 @xref{Auto-loading}.
1329 If you wish to disable the auto-loading during startup,
1330 you must do something like the following:
1333 $ gdb -iex "set auto-load python-scripts off" myprogram
1336 Option @samp{-ex} does not work because the auto-loading is then turned
1340 Executes commands and command files specified by the @samp{-ex} and
1341 @samp{-x} options in their specified order. @xref{Command Files}, for
1342 more details about @value{GDBN} command files.
1345 Reads the command history recorded in the @dfn{history file}.
1346 @xref{Command History}, for more details about the command history and the
1347 files where @value{GDBN} records it.
1350 Init files use the same syntax as @dfn{command files} (@pxref{Command
1351 Files}) and are processed by @value{GDBN} in the same way. The init
1352 file in your home directory can set options (such as @samp{set
1353 complaints}) that affect subsequent processing of command line options
1354 and operands. Init files are not executed if you use the @samp{-nx}
1355 option (@pxref{Mode Options, ,Choosing Modes}).
1357 To display the list of init files loaded by gdb at startup, you
1358 can use @kbd{gdb --help}.
1360 @cindex init file name
1361 @cindex @file{.gdbinit}
1362 @cindex @file{gdb.ini}
1363 The @value{GDBN} init files are normally called @file{.gdbinit}.
1364 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1365 the limitations of file names imposed by DOS filesystems. The Windows
1366 port of @value{GDBN} uses the standard name, but if it finds a
1367 @file{gdb.ini} file in your home directory, it warns you about that
1368 and suggests to rename the file to the standard name.
1372 @section Quitting @value{GDBN}
1373 @cindex exiting @value{GDBN}
1374 @cindex leaving @value{GDBN}
1377 @kindex quit @r{[}@var{expression}@r{]}
1378 @kindex q @r{(@code{quit})}
1379 @item quit @r{[}@var{expression}@r{]}
1381 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1382 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1383 do not supply @var{expression}, @value{GDBN} will terminate normally;
1384 otherwise it will terminate using the result of @var{expression} as the
1389 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1390 terminates the action of any @value{GDBN} command that is in progress and
1391 returns to @value{GDBN} command level. It is safe to type the interrupt
1392 character at any time because @value{GDBN} does not allow it to take effect
1393 until a time when it is safe.
1395 If you have been using @value{GDBN} to control an attached process or
1396 device, you can release it with the @code{detach} command
1397 (@pxref{Attach, ,Debugging an Already-running Process}).
1399 @node Shell Commands
1400 @section Shell Commands
1402 If you need to execute occasional shell commands during your
1403 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1404 just use the @code{shell} command.
1409 @cindex shell escape
1410 @item shell @var{command-string}
1411 @itemx !@var{command-string}
1412 Invoke a standard shell to execute @var{command-string}.
1413 Note that no space is needed between @code{!} and @var{command-string}.
1414 If it exists, the environment variable @code{SHELL} determines which
1415 shell to run. Otherwise @value{GDBN} uses the default shell
1416 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1419 The utility @code{make} is often needed in development environments.
1420 You do not have to use the @code{shell} command for this purpose in
1425 @cindex calling make
1426 @item make @var{make-args}
1427 Execute the @code{make} program with the specified
1428 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1431 @node Logging Output
1432 @section Logging Output
1433 @cindex logging @value{GDBN} output
1434 @cindex save @value{GDBN} output to a file
1436 You may want to save the output of @value{GDBN} commands to a file.
1437 There are several commands to control @value{GDBN}'s logging.
1441 @item set logging on
1443 @item set logging off
1445 @cindex logging file name
1446 @item set logging file @var{file}
1447 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1448 @item set logging overwrite [on|off]
1449 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1450 you want @code{set logging on} to overwrite the logfile instead.
1451 @item set logging redirect [on|off]
1452 By default, @value{GDBN} output will go to both the terminal and the logfile.
1453 Set @code{redirect} if you want output to go only to the log file.
1454 @kindex show logging
1456 Show the current values of the logging settings.
1460 @chapter @value{GDBN} Commands
1462 You can abbreviate a @value{GDBN} command to the first few letters of the command
1463 name, if that abbreviation is unambiguous; and you can repeat certain
1464 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1465 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1466 show you the alternatives available, if there is more than one possibility).
1469 * Command Syntax:: How to give commands to @value{GDBN}
1470 * Completion:: Command completion
1471 * Help:: How to ask @value{GDBN} for help
1474 @node Command Syntax
1475 @section Command Syntax
1477 A @value{GDBN} command is a single line of input. There is no limit on
1478 how long it can be. It starts with a command name, which is followed by
1479 arguments whose meaning depends on the command name. For example, the
1480 command @code{step} accepts an argument which is the number of times to
1481 step, as in @samp{step 5}. You can also use the @code{step} command
1482 with no arguments. Some commands do not allow any arguments.
1484 @cindex abbreviation
1485 @value{GDBN} command names may always be truncated if that abbreviation is
1486 unambiguous. Other possible command abbreviations are listed in the
1487 documentation for individual commands. In some cases, even ambiguous
1488 abbreviations are allowed; for example, @code{s} is specially defined as
1489 equivalent to @code{step} even though there are other commands whose
1490 names start with @code{s}. You can test abbreviations by using them as
1491 arguments to the @code{help} command.
1493 @cindex repeating commands
1494 @kindex RET @r{(repeat last command)}
1495 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1496 repeat the previous command. Certain commands (for example, @code{run})
1497 will not repeat this way; these are commands whose unintentional
1498 repetition might cause trouble and which you are unlikely to want to
1499 repeat. User-defined commands can disable this feature; see
1500 @ref{Define, dont-repeat}.
1502 The @code{list} and @code{x} commands, when you repeat them with
1503 @key{RET}, construct new arguments rather than repeating
1504 exactly as typed. This permits easy scanning of source or memory.
1506 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1507 output, in a way similar to the common utility @code{more}
1508 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1509 @key{RET} too many in this situation, @value{GDBN} disables command
1510 repetition after any command that generates this sort of display.
1512 @kindex # @r{(a comment)}
1514 Any text from a @kbd{#} to the end of the line is a comment; it does
1515 nothing. This is useful mainly in command files (@pxref{Command
1516 Files,,Command Files}).
1518 @cindex repeating command sequences
1519 @kindex Ctrl-o @r{(operate-and-get-next)}
1520 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1521 commands. This command accepts the current line, like @key{RET}, and
1522 then fetches the next line relative to the current line from the history
1526 @section Command Completion
1529 @cindex word completion
1530 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1531 only one possibility; it can also show you what the valid possibilities
1532 are for the next word in a command, at any time. This works for @value{GDBN}
1533 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1535 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1536 of a word. If there is only one possibility, @value{GDBN} fills in the
1537 word, and waits for you to finish the command (or press @key{RET} to
1538 enter it). For example, if you type
1540 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1541 @c complete accuracy in these examples; space introduced for clarity.
1542 @c If texinfo enhancements make it unnecessary, it would be nice to
1543 @c replace " @key" by "@key" in the following...
1545 (@value{GDBP}) info bre @key{TAB}
1549 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1550 the only @code{info} subcommand beginning with @samp{bre}:
1553 (@value{GDBP}) info breakpoints
1557 You can either press @key{RET} at this point, to run the @code{info
1558 breakpoints} command, or backspace and enter something else, if
1559 @samp{breakpoints} does not look like the command you expected. (If you
1560 were sure you wanted @code{info breakpoints} in the first place, you
1561 might as well just type @key{RET} immediately after @samp{info bre},
1562 to exploit command abbreviations rather than command completion).
1564 If there is more than one possibility for the next word when you press
1565 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1566 characters and try again, or just press @key{TAB} a second time;
1567 @value{GDBN} displays all the possible completions for that word. For
1568 example, you might want to set a breakpoint on a subroutine whose name
1569 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1570 just sounds the bell. Typing @key{TAB} again displays all the
1571 function names in your program that begin with those characters, for
1575 (@value{GDBP}) b make_ @key{TAB}
1576 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1577 make_a_section_from_file make_environ
1578 make_abs_section make_function_type
1579 make_blockvector make_pointer_type
1580 make_cleanup make_reference_type
1581 make_command make_symbol_completion_list
1582 (@value{GDBP}) b make_
1586 After displaying the available possibilities, @value{GDBN} copies your
1587 partial input (@samp{b make_} in the example) so you can finish the
1590 If you just want to see the list of alternatives in the first place, you
1591 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1592 means @kbd{@key{META} ?}. You can type this either by holding down a
1593 key designated as the @key{META} shift on your keyboard (if there is
1594 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1596 If the number of possible completions is large, @value{GDBN} will
1597 print as much of the list as it has collected, as well as a message
1598 indicating that the list may be truncated.
1601 (@value{GDBP}) b m@key{TAB}@key{TAB}
1603 <... the rest of the possible completions ...>
1604 *** List may be truncated, max-completions reached. ***
1609 This behavior can be controlled with the following commands:
1612 @kindex set max-completions
1613 @item set max-completions @var{limit}
1614 @itemx set max-completions unlimited
1615 Set the maximum number of completion candidates. @value{GDBN} will
1616 stop looking for more completions once it collects this many candidates.
1617 This is useful when completing on things like function names as collecting
1618 all the possible candidates can be time consuming.
1619 The default value is 200. A value of zero disables tab-completion.
1620 Note that setting either no limit or a very large limit can make
1622 @kindex show max-completions
1623 @item show max-completions
1624 Show the maximum number of candidates that @value{GDBN} will collect and show
1628 @cindex quotes in commands
1629 @cindex completion of quoted strings
1630 Sometimes the string you need, while logically a ``word'', may contain
1631 parentheses or other characters that @value{GDBN} normally excludes from
1632 its notion of a word. To permit word completion to work in this
1633 situation, you may enclose words in @code{'} (single quote marks) in
1634 @value{GDBN} commands.
1636 The most likely situation where you might need this is in typing the
1637 name of a C@t{++} function. This is because C@t{++} allows function
1638 overloading (multiple definitions of the same function, distinguished
1639 by argument type). For example, when you want to set a breakpoint you
1640 may need to distinguish whether you mean the version of @code{name}
1641 that takes an @code{int} parameter, @code{name(int)}, or the version
1642 that takes a @code{float} parameter, @code{name(float)}. To use the
1643 word-completion facilities in this situation, type a single quote
1644 @code{'} at the beginning of the function name. This alerts
1645 @value{GDBN} that it may need to consider more information than usual
1646 when you press @key{TAB} or @kbd{M-?} to request word completion:
1649 (@value{GDBP}) b 'bubble( @kbd{M-?}
1650 bubble(double,double) bubble(int,int)
1651 (@value{GDBP}) b 'bubble(
1654 In some cases, @value{GDBN} can tell that completing a name requires using
1655 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1656 completing as much as it can) if you do not type the quote in the first
1660 (@value{GDBP}) b bub @key{TAB}
1661 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1662 (@value{GDBP}) b 'bubble(
1666 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1667 you have not yet started typing the argument list when you ask for
1668 completion on an overloaded symbol.
1670 For more information about overloaded functions, see @ref{C Plus Plus
1671 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1672 overload-resolution off} to disable overload resolution;
1673 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1675 @cindex completion of structure field names
1676 @cindex structure field name completion
1677 @cindex completion of union field names
1678 @cindex union field name completion
1679 When completing in an expression which looks up a field in a
1680 structure, @value{GDBN} also tries@footnote{The completer can be
1681 confused by certain kinds of invalid expressions. Also, it only
1682 examines the static type of the expression, not the dynamic type.} to
1683 limit completions to the field names available in the type of the
1687 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1688 magic to_fputs to_rewind
1689 to_data to_isatty to_write
1690 to_delete to_put to_write_async_safe
1695 This is because the @code{gdb_stdout} is a variable of the type
1696 @code{struct ui_file} that is defined in @value{GDBN} sources as
1703 ui_file_flush_ftype *to_flush;
1704 ui_file_write_ftype *to_write;
1705 ui_file_write_async_safe_ftype *to_write_async_safe;
1706 ui_file_fputs_ftype *to_fputs;
1707 ui_file_read_ftype *to_read;
1708 ui_file_delete_ftype *to_delete;
1709 ui_file_isatty_ftype *to_isatty;
1710 ui_file_rewind_ftype *to_rewind;
1711 ui_file_put_ftype *to_put;
1718 @section Getting Help
1719 @cindex online documentation
1722 You can always ask @value{GDBN} itself for information on its commands,
1723 using the command @code{help}.
1726 @kindex h @r{(@code{help})}
1729 You can use @code{help} (abbreviated @code{h}) with no arguments to
1730 display a short list of named classes of commands:
1734 List of classes of commands:
1736 aliases -- Aliases of other commands
1737 breakpoints -- Making program stop at certain points
1738 data -- Examining data
1739 files -- Specifying and examining files
1740 internals -- Maintenance commands
1741 obscure -- Obscure features
1742 running -- Running the program
1743 stack -- Examining the stack
1744 status -- Status inquiries
1745 support -- Support facilities
1746 tracepoints -- Tracing of program execution without
1747 stopping the program
1748 user-defined -- User-defined commands
1750 Type "help" followed by a class name for a list of
1751 commands in that class.
1752 Type "help" followed by command name for full
1754 Command name abbreviations are allowed if unambiguous.
1757 @c the above line break eliminates huge line overfull...
1759 @item help @var{class}
1760 Using one of the general help classes as an argument, you can get a
1761 list of the individual commands in that class. For example, here is the
1762 help display for the class @code{status}:
1765 (@value{GDBP}) help status
1770 @c Line break in "show" line falsifies real output, but needed
1771 @c to fit in smallbook page size.
1772 info -- Generic command for showing things
1773 about the program being debugged
1774 show -- Generic command for showing things
1777 Type "help" followed by command name for full
1779 Command name abbreviations are allowed if unambiguous.
1783 @item help @var{command}
1784 With a command name as @code{help} argument, @value{GDBN} displays a
1785 short paragraph on how to use that command.
1788 @item apropos @var{args}
1789 The @code{apropos} command searches through all of the @value{GDBN}
1790 commands, and their documentation, for the regular expression specified in
1791 @var{args}. It prints out all matches found. For example:
1802 alias -- Define a new command that is an alias of an existing command
1803 aliases -- Aliases of other commands
1804 d -- Delete some breakpoints or auto-display expressions
1805 del -- Delete some breakpoints or auto-display expressions
1806 delete -- Delete some breakpoints or auto-display expressions
1811 @item complete @var{args}
1812 The @code{complete @var{args}} command lists all the possible completions
1813 for the beginning of a command. Use @var{args} to specify the beginning of the
1814 command you want completed. For example:
1820 @noindent results in:
1831 @noindent This is intended for use by @sc{gnu} Emacs.
1834 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1835 and @code{show} to inquire about the state of your program, or the state
1836 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1837 manual introduces each of them in the appropriate context. The listings
1838 under @code{info} and under @code{show} in the Command, Variable, and
1839 Function Index point to all the sub-commands. @xref{Command and Variable
1845 @kindex i @r{(@code{info})}
1847 This command (abbreviated @code{i}) is for describing the state of your
1848 program. For example, you can show the arguments passed to a function
1849 with @code{info args}, list the registers currently in use with @code{info
1850 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1851 You can get a complete list of the @code{info} sub-commands with
1852 @w{@code{help info}}.
1856 You can assign the result of an expression to an environment variable with
1857 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1858 @code{set prompt $}.
1862 In contrast to @code{info}, @code{show} is for describing the state of
1863 @value{GDBN} itself.
1864 You can change most of the things you can @code{show}, by using the
1865 related command @code{set}; for example, you can control what number
1866 system is used for displays with @code{set radix}, or simply inquire
1867 which is currently in use with @code{show radix}.
1870 To display all the settable parameters and their current
1871 values, you can use @code{show} with no arguments; you may also use
1872 @code{info set}. Both commands produce the same display.
1873 @c FIXME: "info set" violates the rule that "info" is for state of
1874 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1875 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1879 Here are several miscellaneous @code{show} subcommands, all of which are
1880 exceptional in lacking corresponding @code{set} commands:
1883 @kindex show version
1884 @cindex @value{GDBN} version number
1886 Show what version of @value{GDBN} is running. You should include this
1887 information in @value{GDBN} bug-reports. If multiple versions of
1888 @value{GDBN} are in use at your site, you may need to determine which
1889 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1890 commands are introduced, and old ones may wither away. Also, many
1891 system vendors ship variant versions of @value{GDBN}, and there are
1892 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1893 The version number is the same as the one announced when you start
1896 @kindex show copying
1897 @kindex info copying
1898 @cindex display @value{GDBN} copyright
1901 Display information about permission for copying @value{GDBN}.
1903 @kindex show warranty
1904 @kindex info warranty
1906 @itemx info warranty
1907 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1908 if your version of @value{GDBN} comes with one.
1910 @kindex show configuration
1911 @item show configuration
1912 Display detailed information about the way @value{GDBN} was configured
1913 when it was built. This displays the optional arguments passed to the
1914 @file{configure} script and also configuration parameters detected
1915 automatically by @command{configure}. When reporting a @value{GDBN}
1916 bug (@pxref{GDB Bugs}), it is important to include this information in
1922 @chapter Running Programs Under @value{GDBN}
1924 When you run a program under @value{GDBN}, you must first generate
1925 debugging information when you compile it.
1927 You may start @value{GDBN} with its arguments, if any, in an environment
1928 of your choice. If you are doing native debugging, you may redirect
1929 your program's input and output, debug an already running process, or
1930 kill a child process.
1933 * Compilation:: Compiling for debugging
1934 * Starting:: Starting your program
1935 * Arguments:: Your program's arguments
1936 * Environment:: Your program's environment
1938 * Working Directory:: Your program's working directory
1939 * Input/Output:: Your program's input and output
1940 * Attach:: Debugging an already-running process
1941 * Kill Process:: Killing the child process
1943 * Inferiors and Programs:: Debugging multiple inferiors and programs
1944 * Threads:: Debugging programs with multiple threads
1945 * Forks:: Debugging forks
1946 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1950 @section Compiling for Debugging
1952 In order to debug a program effectively, you need to generate
1953 debugging information when you compile it. This debugging information
1954 is stored in the object file; it describes the data type of each
1955 variable or function and the correspondence between source line numbers
1956 and addresses in the executable code.
1958 To request debugging information, specify the @samp{-g} option when you run
1961 Programs that are to be shipped to your customers are compiled with
1962 optimizations, using the @samp{-O} compiler option. However, some
1963 compilers are unable to handle the @samp{-g} and @samp{-O} options
1964 together. Using those compilers, you cannot generate optimized
1965 executables containing debugging information.
1967 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1968 without @samp{-O}, making it possible to debug optimized code. We
1969 recommend that you @emph{always} use @samp{-g} whenever you compile a
1970 program. You may think your program is correct, but there is no sense
1971 in pushing your luck. For more information, see @ref{Optimized Code}.
1973 Older versions of the @sc{gnu} C compiler permitted a variant option
1974 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1975 format; if your @sc{gnu} C compiler has this option, do not use it.
1977 @value{GDBN} knows about preprocessor macros and can show you their
1978 expansion (@pxref{Macros}). Most compilers do not include information
1979 about preprocessor macros in the debugging information if you specify
1980 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1981 the @sc{gnu} C compiler, provides macro information if you are using
1982 the DWARF debugging format, and specify the option @option{-g3}.
1984 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1985 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1986 information on @value{NGCC} options affecting debug information.
1988 You will have the best debugging experience if you use the latest
1989 version of the DWARF debugging format that your compiler supports.
1990 DWARF is currently the most expressive and best supported debugging
1991 format in @value{GDBN}.
1995 @section Starting your Program
2001 @kindex r @r{(@code{run})}
2004 Use the @code{run} command to start your program under @value{GDBN}.
2005 You must first specify the program name with an argument to
2006 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2007 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2008 command (@pxref{Files, ,Commands to Specify Files}).
2012 If you are running your program in an execution environment that
2013 supports processes, @code{run} creates an inferior process and makes
2014 that process run your program. In some environments without processes,
2015 @code{run} jumps to the start of your program. Other targets,
2016 like @samp{remote}, are always running. If you get an error
2017 message like this one:
2020 The "remote" target does not support "run".
2021 Try "help target" or "continue".
2025 then use @code{continue} to run your program. You may need @code{load}
2026 first (@pxref{load}).
2028 The execution of a program is affected by certain information it
2029 receives from its superior. @value{GDBN} provides ways to specify this
2030 information, which you must do @emph{before} starting your program. (You
2031 can change it after starting your program, but such changes only affect
2032 your program the next time you start it.) This information may be
2033 divided into four categories:
2036 @item The @emph{arguments.}
2037 Specify the arguments to give your program as the arguments of the
2038 @code{run} command. If a shell is available on your target, the shell
2039 is used to pass the arguments, so that you may use normal conventions
2040 (such as wildcard expansion or variable substitution) in describing
2042 In Unix systems, you can control which shell is used with the
2043 @code{SHELL} environment variable. If you do not define @code{SHELL},
2044 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2045 use of any shell with the @code{set startup-with-shell} command (see
2048 @item The @emph{environment.}
2049 Your program normally inherits its environment from @value{GDBN}, but you can
2050 use the @value{GDBN} commands @code{set environment} and @code{unset
2051 environment} to change parts of the environment that affect
2052 your program. @xref{Environment, ,Your Program's Environment}.
2054 @item The @emph{working directory.}
2055 Your program inherits its working directory from @value{GDBN}. You can set
2056 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2057 @xref{Working Directory, ,Your Program's Working Directory}.
2059 @item The @emph{standard input and output.}
2060 Your program normally uses the same device for standard input and
2061 standard output as @value{GDBN} is using. You can redirect input and output
2062 in the @code{run} command line, or you can use the @code{tty} command to
2063 set a different device for your program.
2064 @xref{Input/Output, ,Your Program's Input and Output}.
2067 @emph{Warning:} While input and output redirection work, you cannot use
2068 pipes to pass the output of the program you are debugging to another
2069 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2073 When you issue the @code{run} command, your program begins to execute
2074 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2075 of how to arrange for your program to stop. Once your program has
2076 stopped, you may call functions in your program, using the @code{print}
2077 or @code{call} commands. @xref{Data, ,Examining Data}.
2079 If the modification time of your symbol file has changed since the last
2080 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2081 table, and reads it again. When it does this, @value{GDBN} tries to retain
2082 your current breakpoints.
2087 @cindex run to main procedure
2088 The name of the main procedure can vary from language to language.
2089 With C or C@t{++}, the main procedure name is always @code{main}, but
2090 other languages such as Ada do not require a specific name for their
2091 main procedure. The debugger provides a convenient way to start the
2092 execution of the program and to stop at the beginning of the main
2093 procedure, depending on the language used.
2095 The @samp{start} command does the equivalent of setting a temporary
2096 breakpoint at the beginning of the main procedure and then invoking
2097 the @samp{run} command.
2099 @cindex elaboration phase
2100 Some programs contain an @dfn{elaboration} phase where some startup code is
2101 executed before the main procedure is called. This depends on the
2102 languages used to write your program. In C@t{++}, for instance,
2103 constructors for static and global objects are executed before
2104 @code{main} is called. It is therefore possible that the debugger stops
2105 before reaching the main procedure. However, the temporary breakpoint
2106 will remain to halt execution.
2108 Specify the arguments to give to your program as arguments to the
2109 @samp{start} command. These arguments will be given verbatim to the
2110 underlying @samp{run} command. Note that the same arguments will be
2111 reused if no argument is provided during subsequent calls to
2112 @samp{start} or @samp{run}.
2114 It is sometimes necessary to debug the program during elaboration. In
2115 these cases, using the @code{start} command would stop the execution of
2116 your program too late, as the program would have already completed the
2117 elaboration phase. Under these circumstances, insert breakpoints in your
2118 elaboration code before running your program.
2120 @anchor{set exec-wrapper}
2121 @kindex set exec-wrapper
2122 @item set exec-wrapper @var{wrapper}
2123 @itemx show exec-wrapper
2124 @itemx unset exec-wrapper
2125 When @samp{exec-wrapper} is set, the specified wrapper is used to
2126 launch programs for debugging. @value{GDBN} starts your program
2127 with a shell command of the form @kbd{exec @var{wrapper}
2128 @var{program}}. Quoting is added to @var{program} and its
2129 arguments, but not to @var{wrapper}, so you should add quotes if
2130 appropriate for your shell. The wrapper runs until it executes
2131 your program, and then @value{GDBN} takes control.
2133 You can use any program that eventually calls @code{execve} with
2134 its arguments as a wrapper. Several standard Unix utilities do
2135 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2136 with @code{exec "$@@"} will also work.
2138 For example, you can use @code{env} to pass an environment variable to
2139 the debugged program, without setting the variable in your shell's
2143 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2147 This command is available when debugging locally on most targets, excluding
2148 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2150 @kindex set startup-with-shell
2151 @item set startup-with-shell
2152 @itemx set startup-with-shell on
2153 @itemx set startup-with-shell off
2154 @itemx show set startup-with-shell
2155 On Unix systems, by default, if a shell is available on your target,
2156 @value{GDBN}) uses it to start your program. Arguments of the
2157 @code{run} command are passed to the shell, which does variable
2158 substitution, expands wildcard characters and performs redirection of
2159 I/O. In some circumstances, it may be useful to disable such use of a
2160 shell, for example, when debugging the shell itself or diagnosing
2161 startup failures such as:
2165 Starting program: ./a.out
2166 During startup program terminated with signal SIGSEGV, Segmentation fault.
2170 which indicates the shell or the wrapper specified with
2171 @samp{exec-wrapper} crashed, not your program. Most often, this is
2172 caused by something odd in your shell's non-interactive mode
2173 initialization file---such as @file{.cshrc} for C-shell,
2174 $@file{.zshenv} for the Z shell, or the file specified in the
2175 @samp{BASH_ENV} environment variable for BASH.
2177 @anchor{set auto-connect-native-target}
2178 @kindex set auto-connect-native-target
2179 @item set auto-connect-native-target
2180 @itemx set auto-connect-native-target on
2181 @itemx set auto-connect-native-target off
2182 @itemx show auto-connect-native-target
2184 By default, if not connected to any target yet (e.g., with
2185 @code{target remote}), the @code{run} command starts your program as a
2186 native process under @value{GDBN}, on your local machine. If you're
2187 sure you don't want to debug programs on your local machine, you can
2188 tell @value{GDBN} to not connect to the native target automatically
2189 with the @code{set auto-connect-native-target off} command.
2191 If @code{on}, which is the default, and if @value{GDBN} is not
2192 connected to a target already, the @code{run} command automaticaly
2193 connects to the native target, if one is available.
2195 If @code{off}, and if @value{GDBN} is not connected to a target
2196 already, the @code{run} command fails with an error:
2200 Don't know how to run. Try "help target".
2203 If @value{GDBN} is already connected to a target, @value{GDBN} always
2204 uses it with the @code{run} command.
2206 In any case, you can explicitly connect to the native target with the
2207 @code{target native} command. For example,
2210 (@value{GDBP}) set auto-connect-native-target off
2212 Don't know how to run. Try "help target".
2213 (@value{GDBP}) target native
2215 Starting program: ./a.out
2216 [Inferior 1 (process 10421) exited normally]
2219 In case you connected explicitly to the @code{native} target,
2220 @value{GDBN} remains connected even if all inferiors exit, ready for
2221 the next @code{run} command. Use the @code{disconnect} command to
2224 Examples of other commands that likewise respect the
2225 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2226 proc}, @code{info os}.
2228 @kindex set disable-randomization
2229 @item set disable-randomization
2230 @itemx set disable-randomization on
2231 This option (enabled by default in @value{GDBN}) will turn off the native
2232 randomization of the virtual address space of the started program. This option
2233 is useful for multiple debugging sessions to make the execution better
2234 reproducible and memory addresses reusable across debugging sessions.
2236 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2237 On @sc{gnu}/Linux you can get the same behavior using
2240 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2243 @item set disable-randomization off
2244 Leave the behavior of the started executable unchanged. Some bugs rear their
2245 ugly heads only when the program is loaded at certain addresses. If your bug
2246 disappears when you run the program under @value{GDBN}, that might be because
2247 @value{GDBN} by default disables the address randomization on platforms, such
2248 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2249 disable-randomization off} to try to reproduce such elusive bugs.
2251 On targets where it is available, virtual address space randomization
2252 protects the programs against certain kinds of security attacks. In these
2253 cases the attacker needs to know the exact location of a concrete executable
2254 code. Randomizing its location makes it impossible to inject jumps misusing
2255 a code at its expected addresses.
2257 Prelinking shared libraries provides a startup performance advantage but it
2258 makes addresses in these libraries predictable for privileged processes by
2259 having just unprivileged access at the target system. Reading the shared
2260 library binary gives enough information for assembling the malicious code
2261 misusing it. Still even a prelinked shared library can get loaded at a new
2262 random address just requiring the regular relocation process during the
2263 startup. Shared libraries not already prelinked are always loaded at
2264 a randomly chosen address.
2266 Position independent executables (PIE) contain position independent code
2267 similar to the shared libraries and therefore such executables get loaded at
2268 a randomly chosen address upon startup. PIE executables always load even
2269 already prelinked shared libraries at a random address. You can build such
2270 executable using @command{gcc -fPIE -pie}.
2272 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2273 (as long as the randomization is enabled).
2275 @item show disable-randomization
2276 Show the current setting of the explicit disable of the native randomization of
2277 the virtual address space of the started program.
2282 @section Your Program's Arguments
2284 @cindex arguments (to your program)
2285 The arguments to your program can be specified by the arguments of the
2287 They are passed to a shell, which expands wildcard characters and
2288 performs redirection of I/O, and thence to your program. Your
2289 @code{SHELL} environment variable (if it exists) specifies what shell
2290 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2291 the default shell (@file{/bin/sh} on Unix).
2293 On non-Unix systems, the program is usually invoked directly by
2294 @value{GDBN}, which emulates I/O redirection via the appropriate system
2295 calls, and the wildcard characters are expanded by the startup code of
2296 the program, not by the shell.
2298 @code{run} with no arguments uses the same arguments used by the previous
2299 @code{run}, or those set by the @code{set args} command.
2304 Specify the arguments to be used the next time your program is run. If
2305 @code{set args} has no arguments, @code{run} executes your program
2306 with no arguments. Once you have run your program with arguments,
2307 using @code{set args} before the next @code{run} is the only way to run
2308 it again without arguments.
2312 Show the arguments to give your program when it is started.
2316 @section Your Program's Environment
2318 @cindex environment (of your program)
2319 The @dfn{environment} consists of a set of environment variables and
2320 their values. Environment variables conventionally record such things as
2321 your user name, your home directory, your terminal type, and your search
2322 path for programs to run. Usually you set up environment variables with
2323 the shell and they are inherited by all the other programs you run. When
2324 debugging, it can be useful to try running your program with a modified
2325 environment without having to start @value{GDBN} over again.
2329 @item path @var{directory}
2330 Add @var{directory} to the front of the @code{PATH} environment variable
2331 (the search path for executables) that will be passed to your program.
2332 The value of @code{PATH} used by @value{GDBN} does not change.
2333 You may specify several directory names, separated by whitespace or by a
2334 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2335 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2336 is moved to the front, so it is searched sooner.
2338 You can use the string @samp{$cwd} to refer to whatever is the current
2339 working directory at the time @value{GDBN} searches the path. If you
2340 use @samp{.} instead, it refers to the directory where you executed the
2341 @code{path} command. @value{GDBN} replaces @samp{.} in the
2342 @var{directory} argument (with the current path) before adding
2343 @var{directory} to the search path.
2344 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2345 @c document that, since repeating it would be a no-op.
2349 Display the list of search paths for executables (the @code{PATH}
2350 environment variable).
2352 @kindex show environment
2353 @item show environment @r{[}@var{varname}@r{]}
2354 Print the value of environment variable @var{varname} to be given to
2355 your program when it starts. If you do not supply @var{varname},
2356 print the names and values of all environment variables to be given to
2357 your program. You can abbreviate @code{environment} as @code{env}.
2359 @kindex set environment
2360 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2361 Set environment variable @var{varname} to @var{value}. The value
2362 changes for your program (and the shell @value{GDBN} uses to launch
2363 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2364 values of environment variables are just strings, and any
2365 interpretation is supplied by your program itself. The @var{value}
2366 parameter is optional; if it is eliminated, the variable is set to a
2368 @c "any string" here does not include leading, trailing
2369 @c blanks. Gnu asks: does anyone care?
2371 For example, this command:
2378 tells the debugged program, when subsequently run, that its user is named
2379 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2380 are not actually required.)
2382 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2383 which also inherits the environment set with @code{set environment}.
2384 If necessary, you can avoid that by using the @samp{env} program as a
2385 wrapper instead of using @code{set environment}. @xref{set
2386 exec-wrapper}, for an example doing just that.
2388 @kindex unset environment
2389 @item unset environment @var{varname}
2390 Remove variable @var{varname} from the environment to be passed to your
2391 program. This is different from @samp{set env @var{varname} =};
2392 @code{unset environment} removes the variable from the environment,
2393 rather than assigning it an empty value.
2396 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2397 the shell indicated by your @code{SHELL} environment variable if it
2398 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2399 names a shell that runs an initialization file when started
2400 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2401 for the Z shell, or the file specified in the @samp{BASH_ENV}
2402 environment variable for BASH---any variables you set in that file
2403 affect your program. You may wish to move setting of environment
2404 variables to files that are only run when you sign on, such as
2405 @file{.login} or @file{.profile}.
2407 @node Working Directory
2408 @section Your Program's Working Directory
2410 @cindex working directory (of your program)
2411 Each time you start your program with @code{run}, it inherits its
2412 working directory from the current working directory of @value{GDBN}.
2413 The @value{GDBN} working directory is initially whatever it inherited
2414 from its parent process (typically the shell), but you can specify a new
2415 working directory in @value{GDBN} with the @code{cd} command.
2417 The @value{GDBN} working directory also serves as a default for the commands
2418 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2423 @cindex change working directory
2424 @item cd @r{[}@var{directory}@r{]}
2425 Set the @value{GDBN} working directory to @var{directory}. If not
2426 given, @var{directory} uses @file{'~'}.
2430 Print the @value{GDBN} working directory.
2433 It is generally impossible to find the current working directory of
2434 the process being debugged (since a program can change its directory
2435 during its run). If you work on a system where @value{GDBN} is
2436 configured with the @file{/proc} support, you can use the @code{info
2437 proc} command (@pxref{SVR4 Process Information}) to find out the
2438 current working directory of the debuggee.
2441 @section Your Program's Input and Output
2446 By default, the program you run under @value{GDBN} does input and output to
2447 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2448 to its own terminal modes to interact with you, but it records the terminal
2449 modes your program was using and switches back to them when you continue
2450 running your program.
2453 @kindex info terminal
2455 Displays information recorded by @value{GDBN} about the terminal modes your
2459 You can redirect your program's input and/or output using shell
2460 redirection with the @code{run} command. For example,
2467 starts your program, diverting its output to the file @file{outfile}.
2470 @cindex controlling terminal
2471 Another way to specify where your program should do input and output is
2472 with the @code{tty} command. This command accepts a file name as
2473 argument, and causes this file to be the default for future @code{run}
2474 commands. It also resets the controlling terminal for the child
2475 process, for future @code{run} commands. For example,
2482 directs that processes started with subsequent @code{run} commands
2483 default to do input and output on the terminal @file{/dev/ttyb} and have
2484 that as their controlling terminal.
2486 An explicit redirection in @code{run} overrides the @code{tty} command's
2487 effect on the input/output device, but not its effect on the controlling
2490 When you use the @code{tty} command or redirect input in the @code{run}
2491 command, only the input @emph{for your program} is affected. The input
2492 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2493 for @code{set inferior-tty}.
2495 @cindex inferior tty
2496 @cindex set inferior controlling terminal
2497 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2498 display the name of the terminal that will be used for future runs of your
2502 @item set inferior-tty /dev/ttyb
2503 @kindex set inferior-tty
2504 Set the tty for the program being debugged to /dev/ttyb.
2506 @item show inferior-tty
2507 @kindex show inferior-tty
2508 Show the current tty for the program being debugged.
2512 @section Debugging an Already-running Process
2517 @item attach @var{process-id}
2518 This command attaches to a running process---one that was started
2519 outside @value{GDBN}. (@code{info files} shows your active
2520 targets.) The command takes as argument a process ID. The usual way to
2521 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2522 or with the @samp{jobs -l} shell command.
2524 @code{attach} does not repeat if you press @key{RET} a second time after
2525 executing the command.
2528 To use @code{attach}, your program must be running in an environment
2529 which supports processes; for example, @code{attach} does not work for
2530 programs on bare-board targets that lack an operating system. You must
2531 also have permission to send the process a signal.
2533 When you use @code{attach}, the debugger finds the program running in
2534 the process first by looking in the current working directory, then (if
2535 the program is not found) by using the source file search path
2536 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2537 the @code{file} command to load the program. @xref{Files, ,Commands to
2540 The first thing @value{GDBN} does after arranging to debug the specified
2541 process is to stop it. You can examine and modify an attached process
2542 with all the @value{GDBN} commands that are ordinarily available when
2543 you start processes with @code{run}. You can insert breakpoints; you
2544 can step and continue; you can modify storage. If you would rather the
2545 process continue running, you may use the @code{continue} command after
2546 attaching @value{GDBN} to the process.
2551 When you have finished debugging the attached process, you can use the
2552 @code{detach} command to release it from @value{GDBN} control. Detaching
2553 the process continues its execution. After the @code{detach} command,
2554 that process and @value{GDBN} become completely independent once more, and you
2555 are ready to @code{attach} another process or start one with @code{run}.
2556 @code{detach} does not repeat if you press @key{RET} again after
2557 executing the command.
2560 If you exit @value{GDBN} while you have an attached process, you detach
2561 that process. If you use the @code{run} command, you kill that process.
2562 By default, @value{GDBN} asks for confirmation if you try to do either of these
2563 things; you can control whether or not you need to confirm by using the
2564 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2568 @section Killing the Child Process
2573 Kill the child process in which your program is running under @value{GDBN}.
2576 This command is useful if you wish to debug a core dump instead of a
2577 running process. @value{GDBN} ignores any core dump file while your program
2580 On some operating systems, a program cannot be executed outside @value{GDBN}
2581 while you have breakpoints set on it inside @value{GDBN}. You can use the
2582 @code{kill} command in this situation to permit running your program
2583 outside the debugger.
2585 The @code{kill} command is also useful if you wish to recompile and
2586 relink your program, since on many systems it is impossible to modify an
2587 executable file while it is running in a process. In this case, when you
2588 next type @code{run}, @value{GDBN} notices that the file has changed, and
2589 reads the symbol table again (while trying to preserve your current
2590 breakpoint settings).
2592 @node Inferiors and Programs
2593 @section Debugging Multiple Inferiors and Programs
2595 @value{GDBN} lets you run and debug multiple programs in a single
2596 session. In addition, @value{GDBN} on some systems may let you run
2597 several programs simultaneously (otherwise you have to exit from one
2598 before starting another). In the most general case, you can have
2599 multiple threads of execution in each of multiple processes, launched
2600 from multiple executables.
2603 @value{GDBN} represents the state of each program execution with an
2604 object called an @dfn{inferior}. An inferior typically corresponds to
2605 a process, but is more general and applies also to targets that do not
2606 have processes. Inferiors may be created before a process runs, and
2607 may be retained after a process exits. Inferiors have unique
2608 identifiers that are different from process ids. Usually each
2609 inferior will also have its own distinct address space, although some
2610 embedded targets may have several inferiors running in different parts
2611 of a single address space. Each inferior may in turn have multiple
2612 threads running in it.
2614 To find out what inferiors exist at any moment, use @w{@code{info
2618 @kindex info inferiors
2619 @item info inferiors
2620 Print a list of all inferiors currently being managed by @value{GDBN}.
2622 @value{GDBN} displays for each inferior (in this order):
2626 the inferior number assigned by @value{GDBN}
2629 the target system's inferior identifier
2632 the name of the executable the inferior is running.
2637 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2638 indicates the current inferior.
2642 @c end table here to get a little more width for example
2645 (@value{GDBP}) info inferiors
2646 Num Description Executable
2647 2 process 2307 hello
2648 * 1 process 3401 goodbye
2651 To switch focus between inferiors, use the @code{inferior} command:
2654 @kindex inferior @var{infno}
2655 @item inferior @var{infno}
2656 Make inferior number @var{infno} the current inferior. The argument
2657 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2658 in the first field of the @samp{info inferiors} display.
2662 You can get multiple executables into a debugging session via the
2663 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2664 systems @value{GDBN} can add inferiors to the debug session
2665 automatically by following calls to @code{fork} and @code{exec}. To
2666 remove inferiors from the debugging session use the
2667 @w{@code{remove-inferiors}} command.
2670 @kindex add-inferior
2671 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2672 Adds @var{n} inferiors to be run using @var{executable} as the
2673 executable; @var{n} defaults to 1. If no executable is specified,
2674 the inferiors begins empty, with no program. You can still assign or
2675 change the program assigned to the inferior at any time by using the
2676 @code{file} command with the executable name as its argument.
2678 @kindex clone-inferior
2679 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2680 Adds @var{n} inferiors ready to execute the same program as inferior
2681 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2682 number of the current inferior. This is a convenient command when you
2683 want to run another instance of the inferior you are debugging.
2686 (@value{GDBP}) info inferiors
2687 Num Description Executable
2688 * 1 process 29964 helloworld
2689 (@value{GDBP}) clone-inferior
2692 (@value{GDBP}) info inferiors
2693 Num Description Executable
2695 * 1 process 29964 helloworld
2698 You can now simply switch focus to inferior 2 and run it.
2700 @kindex remove-inferiors
2701 @item remove-inferiors @var{infno}@dots{}
2702 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2703 possible to remove an inferior that is running with this command. For
2704 those, use the @code{kill} or @code{detach} command first.
2708 To quit debugging one of the running inferiors that is not the current
2709 inferior, you can either detach from it by using the @w{@code{detach
2710 inferior}} command (allowing it to run independently), or kill it
2711 using the @w{@code{kill inferiors}} command:
2714 @kindex detach inferiors @var{infno}@dots{}
2715 @item detach inferior @var{infno}@dots{}
2716 Detach from the inferior or inferiors identified by @value{GDBN}
2717 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2718 still stays on the list of inferiors shown by @code{info inferiors},
2719 but its Description will show @samp{<null>}.
2721 @kindex kill inferiors @var{infno}@dots{}
2722 @item kill inferiors @var{infno}@dots{}
2723 Kill the inferior or inferiors identified by @value{GDBN} inferior
2724 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2725 stays on the list of inferiors shown by @code{info inferiors}, but its
2726 Description will show @samp{<null>}.
2729 After the successful completion of a command such as @code{detach},
2730 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2731 a normal process exit, the inferior is still valid and listed with
2732 @code{info inferiors}, ready to be restarted.
2735 To be notified when inferiors are started or exit under @value{GDBN}'s
2736 control use @w{@code{set print inferior-events}}:
2739 @kindex set print inferior-events
2740 @cindex print messages on inferior start and exit
2741 @item set print inferior-events
2742 @itemx set print inferior-events on
2743 @itemx set print inferior-events off
2744 The @code{set print inferior-events} command allows you to enable or
2745 disable printing of messages when @value{GDBN} notices that new
2746 inferiors have started or that inferiors have exited or have been
2747 detached. By default, these messages will not be printed.
2749 @kindex show print inferior-events
2750 @item show print inferior-events
2751 Show whether messages will be printed when @value{GDBN} detects that
2752 inferiors have started, exited or have been detached.
2755 Many commands will work the same with multiple programs as with a
2756 single program: e.g., @code{print myglobal} will simply display the
2757 value of @code{myglobal} in the current inferior.
2760 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2761 get more info about the relationship of inferiors, programs, address
2762 spaces in a debug session. You can do that with the @w{@code{maint
2763 info program-spaces}} command.
2766 @kindex maint info program-spaces
2767 @item maint info program-spaces
2768 Print a list of all program spaces currently being managed by
2771 @value{GDBN} displays for each program space (in this order):
2775 the program space number assigned by @value{GDBN}
2778 the name of the executable loaded into the program space, with e.g.,
2779 the @code{file} command.
2784 An asterisk @samp{*} preceding the @value{GDBN} program space number
2785 indicates the current program space.
2787 In addition, below each program space line, @value{GDBN} prints extra
2788 information that isn't suitable to display in tabular form. For
2789 example, the list of inferiors bound to the program space.
2792 (@value{GDBP}) maint info program-spaces
2795 Bound inferiors: ID 1 (process 21561)
2799 Here we can see that no inferior is running the program @code{hello},
2800 while @code{process 21561} is running the program @code{goodbye}. On
2801 some targets, it is possible that multiple inferiors are bound to the
2802 same program space. The most common example is that of debugging both
2803 the parent and child processes of a @code{vfork} call. For example,
2806 (@value{GDBP}) maint info program-spaces
2809 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2812 Here, both inferior 2 and inferior 1 are running in the same program
2813 space as a result of inferior 1 having executed a @code{vfork} call.
2817 @section Debugging Programs with Multiple Threads
2819 @cindex threads of execution
2820 @cindex multiple threads
2821 @cindex switching threads
2822 In some operating systems, such as HP-UX and Solaris, a single program
2823 may have more than one @dfn{thread} of execution. The precise semantics
2824 of threads differ from one operating system to another, but in general
2825 the threads of a single program are akin to multiple processes---except
2826 that they share one address space (that is, they can all examine and
2827 modify the same variables). On the other hand, each thread has its own
2828 registers and execution stack, and perhaps private memory.
2830 @value{GDBN} provides these facilities for debugging multi-thread
2834 @item automatic notification of new threads
2835 @item @samp{thread @var{threadno}}, a command to switch among threads
2836 @item @samp{info threads}, a command to inquire about existing threads
2837 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2838 a command to apply a command to a list of threads
2839 @item thread-specific breakpoints
2840 @item @samp{set print thread-events}, which controls printing of
2841 messages on thread start and exit.
2842 @item @samp{set libthread-db-search-path @var{path}}, which lets
2843 the user specify which @code{libthread_db} to use if the default choice
2844 isn't compatible with the program.
2848 @emph{Warning:} These facilities are not yet available on every
2849 @value{GDBN} configuration where the operating system supports threads.
2850 If your @value{GDBN} does not support threads, these commands have no
2851 effect. For example, a system without thread support shows no output
2852 from @samp{info threads}, and always rejects the @code{thread} command,
2856 (@value{GDBP}) info threads
2857 (@value{GDBP}) thread 1
2858 Thread ID 1 not known. Use the "info threads" command to
2859 see the IDs of currently known threads.
2861 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2862 @c doesn't support threads"?
2865 @cindex focus of debugging
2866 @cindex current thread
2867 The @value{GDBN} thread debugging facility allows you to observe all
2868 threads while your program runs---but whenever @value{GDBN} takes
2869 control, one thread in particular is always the focus of debugging.
2870 This thread is called the @dfn{current thread}. Debugging commands show
2871 program information from the perspective of the current thread.
2873 @cindex @code{New} @var{systag} message
2874 @cindex thread identifier (system)
2875 @c FIXME-implementors!! It would be more helpful if the [New...] message
2876 @c included GDB's numeric thread handle, so you could just go to that
2877 @c thread without first checking `info threads'.
2878 Whenever @value{GDBN} detects a new thread in your program, it displays
2879 the target system's identification for the thread with a message in the
2880 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2881 whose form varies depending on the particular system. For example, on
2882 @sc{gnu}/Linux, you might see
2885 [New Thread 0x41e02940 (LWP 25582)]
2889 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2890 the @var{systag} is simply something like @samp{process 368}, with no
2893 @c FIXME!! (1) Does the [New...] message appear even for the very first
2894 @c thread of a program, or does it only appear for the
2895 @c second---i.e.@: when it becomes obvious we have a multithread
2897 @c (2) *Is* there necessarily a first thread always? Or do some
2898 @c multithread systems permit starting a program with multiple
2899 @c threads ab initio?
2901 @cindex thread number
2902 @cindex thread identifier (GDB)
2903 For debugging purposes, @value{GDBN} associates its own thread
2904 number---always a single integer---with each thread in your program.
2907 @kindex info threads
2908 @item info threads @r{[}@var{id}@dots{}@r{]}
2909 Display a summary of all threads currently in your program. Optional
2910 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2911 means to print information only about the specified thread or threads.
2912 @value{GDBN} displays for each thread (in this order):
2916 the thread number assigned by @value{GDBN}
2919 the target system's thread identifier (@var{systag})
2922 the thread's name, if one is known. A thread can either be named by
2923 the user (see @code{thread name}, below), or, in some cases, by the
2927 the current stack frame summary for that thread
2931 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2932 indicates the current thread.
2936 @c end table here to get a little more width for example
2939 (@value{GDBP}) info threads
2941 3 process 35 thread 27 0x34e5 in sigpause ()
2942 2 process 35 thread 23 0x34e5 in sigpause ()
2943 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2947 On Solaris, you can display more information about user threads with a
2948 Solaris-specific command:
2951 @item maint info sol-threads
2952 @kindex maint info sol-threads
2953 @cindex thread info (Solaris)
2954 Display info on Solaris user threads.
2958 @kindex thread @var{threadno}
2959 @item thread @var{threadno}
2960 Make thread number @var{threadno} the current thread. The command
2961 argument @var{threadno} is the internal @value{GDBN} thread number, as
2962 shown in the first field of the @samp{info threads} display.
2963 @value{GDBN} responds by displaying the system identifier of the thread
2964 you selected, and its current stack frame summary:
2967 (@value{GDBP}) thread 2
2968 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2969 #0 some_function (ignore=0x0) at example.c:8
2970 8 printf ("hello\n");
2974 As with the @samp{[New @dots{}]} message, the form of the text after
2975 @samp{Switching to} depends on your system's conventions for identifying
2978 @vindex $_thread@r{, convenience variable}
2979 The debugger convenience variable @samp{$_thread} contains the number
2980 of the current thread. You may find this useful in writing breakpoint
2981 conditional expressions, command scripts, and so forth. See
2982 @xref{Convenience Vars,, Convenience Variables}, for general
2983 information on convenience variables.
2985 @kindex thread apply
2986 @cindex apply command to several threads
2987 @item thread apply [@var{threadno} | all [-ascending]] @var{command}
2988 The @code{thread apply} command allows you to apply the named
2989 @var{command} to one or more threads. Specify the numbers of the
2990 threads that you want affected with the command argument
2991 @var{threadno}. It can be a single thread number, one of the numbers
2992 shown in the first field of the @samp{info threads} display; or it
2993 could be a range of thread numbers, as in @code{2-4}. To apply
2994 a command to all threads in descending order, type @kbd{thread apply all
2995 @var{command}}. To apply a command to all threads in ascending order,
2996 type @kbd{thread apply all -ascending @var{command}}.
3000 @cindex name a thread
3001 @item thread name [@var{name}]
3002 This command assigns a name to the current thread. If no argument is
3003 given, any existing user-specified name is removed. The thread name
3004 appears in the @samp{info threads} display.
3006 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3007 determine the name of the thread as given by the OS. On these
3008 systems, a name specified with @samp{thread name} will override the
3009 system-give name, and removing the user-specified name will cause
3010 @value{GDBN} to once again display the system-specified name.
3013 @cindex search for a thread
3014 @item thread find [@var{regexp}]
3015 Search for and display thread ids whose name or @var{systag}
3016 matches the supplied regular expression.
3018 As well as being the complement to the @samp{thread name} command,
3019 this command also allows you to identify a thread by its target
3020 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3024 (@value{GDBN}) thread find 26688
3025 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3026 (@value{GDBN}) info thread 4
3028 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3031 @kindex set print thread-events
3032 @cindex print messages on thread start and exit
3033 @item set print thread-events
3034 @itemx set print thread-events on
3035 @itemx set print thread-events off
3036 The @code{set print thread-events} command allows you to enable or
3037 disable printing of messages when @value{GDBN} notices that new threads have
3038 started or that threads have exited. By default, these messages will
3039 be printed if detection of these events is supported by the target.
3040 Note that these messages cannot be disabled on all targets.
3042 @kindex show print thread-events
3043 @item show print thread-events
3044 Show whether messages will be printed when @value{GDBN} detects that threads
3045 have started and exited.
3048 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3049 more information about how @value{GDBN} behaves when you stop and start
3050 programs with multiple threads.
3052 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3053 watchpoints in programs with multiple threads.
3055 @anchor{set libthread-db-search-path}
3057 @kindex set libthread-db-search-path
3058 @cindex search path for @code{libthread_db}
3059 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3060 If this variable is set, @var{path} is a colon-separated list of
3061 directories @value{GDBN} will use to search for @code{libthread_db}.
3062 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3063 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3064 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3067 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3068 @code{libthread_db} library to obtain information about threads in the
3069 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3070 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3071 specific thread debugging library loading is enabled
3072 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3074 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3075 refers to the default system directories that are
3076 normally searched for loading shared libraries. The @samp{$sdir} entry
3077 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3078 (@pxref{libthread_db.so.1 file}).
3080 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3081 refers to the directory from which @code{libpthread}
3082 was loaded in the inferior process.
3084 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3085 @value{GDBN} attempts to initialize it with the current inferior process.
3086 If this initialization fails (which could happen because of a version
3087 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3088 will unload @code{libthread_db}, and continue with the next directory.
3089 If none of @code{libthread_db} libraries initialize successfully,
3090 @value{GDBN} will issue a warning and thread debugging will be disabled.
3092 Setting @code{libthread-db-search-path} is currently implemented
3093 only on some platforms.
3095 @kindex show libthread-db-search-path
3096 @item show libthread-db-search-path
3097 Display current libthread_db search path.
3099 @kindex set debug libthread-db
3100 @kindex show debug libthread-db
3101 @cindex debugging @code{libthread_db}
3102 @item set debug libthread-db
3103 @itemx show debug libthread-db
3104 Turns on or off display of @code{libthread_db}-related events.
3105 Use @code{1} to enable, @code{0} to disable.
3109 @section Debugging Forks
3111 @cindex fork, debugging programs which call
3112 @cindex multiple processes
3113 @cindex processes, multiple
3114 On most systems, @value{GDBN} has no special support for debugging
3115 programs which create additional processes using the @code{fork}
3116 function. When a program forks, @value{GDBN} will continue to debug the
3117 parent process and the child process will run unimpeded. If you have
3118 set a breakpoint in any code which the child then executes, the child
3119 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3120 will cause it to terminate.
3122 However, if you want to debug the child process there is a workaround
3123 which isn't too painful. Put a call to @code{sleep} in the code which
3124 the child process executes after the fork. It may be useful to sleep
3125 only if a certain environment variable is set, or a certain file exists,
3126 so that the delay need not occur when you don't want to run @value{GDBN}
3127 on the child. While the child is sleeping, use the @code{ps} program to
3128 get its process ID. Then tell @value{GDBN} (a new invocation of
3129 @value{GDBN} if you are also debugging the parent process) to attach to
3130 the child process (@pxref{Attach}). From that point on you can debug
3131 the child process just like any other process which you attached to.
3133 On some systems, @value{GDBN} provides support for debugging programs that
3134 create additional processes using the @code{fork} or @code{vfork} functions.
3135 Currently, the only platforms with this feature are HP-UX (11.x and later
3136 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3138 By default, when a program forks, @value{GDBN} will continue to debug
3139 the parent process and the child process will run unimpeded.
3141 If you want to follow the child process instead of the parent process,
3142 use the command @w{@code{set follow-fork-mode}}.
3145 @kindex set follow-fork-mode
3146 @item set follow-fork-mode @var{mode}
3147 Set the debugger response to a program call of @code{fork} or
3148 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3149 process. The @var{mode} argument can be:
3153 The original process is debugged after a fork. The child process runs
3154 unimpeded. This is the default.
3157 The new process is debugged after a fork. The parent process runs
3162 @kindex show follow-fork-mode
3163 @item show follow-fork-mode
3164 Display the current debugger response to a @code{fork} or @code{vfork} call.
3167 @cindex debugging multiple processes
3168 On Linux, if you want to debug both the parent and child processes, use the
3169 command @w{@code{set detach-on-fork}}.
3172 @kindex set detach-on-fork
3173 @item set detach-on-fork @var{mode}
3174 Tells gdb whether to detach one of the processes after a fork, or
3175 retain debugger control over them both.
3179 The child process (or parent process, depending on the value of
3180 @code{follow-fork-mode}) will be detached and allowed to run
3181 independently. This is the default.
3184 Both processes will be held under the control of @value{GDBN}.
3185 One process (child or parent, depending on the value of
3186 @code{follow-fork-mode}) is debugged as usual, while the other
3191 @kindex show detach-on-fork
3192 @item show detach-on-fork
3193 Show whether detach-on-fork mode is on/off.
3196 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3197 will retain control of all forked processes (including nested forks).
3198 You can list the forked processes under the control of @value{GDBN} by
3199 using the @w{@code{info inferiors}} command, and switch from one fork
3200 to another by using the @code{inferior} command (@pxref{Inferiors and
3201 Programs, ,Debugging Multiple Inferiors and Programs}).
3203 To quit debugging one of the forked processes, you can either detach
3204 from it by using the @w{@code{detach inferiors}} command (allowing it
3205 to run independently), or kill it using the @w{@code{kill inferiors}}
3206 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3209 If you ask to debug a child process and a @code{vfork} is followed by an
3210 @code{exec}, @value{GDBN} executes the new target up to the first
3211 breakpoint in the new target. If you have a breakpoint set on
3212 @code{main} in your original program, the breakpoint will also be set on
3213 the child process's @code{main}.
3215 On some systems, when a child process is spawned by @code{vfork}, you
3216 cannot debug the child or parent until an @code{exec} call completes.
3218 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3219 call executes, the new target restarts. To restart the parent
3220 process, use the @code{file} command with the parent executable name
3221 as its argument. By default, after an @code{exec} call executes,
3222 @value{GDBN} discards the symbols of the previous executable image.
3223 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3227 @kindex set follow-exec-mode
3228 @item set follow-exec-mode @var{mode}
3230 Set debugger response to a program call of @code{exec}. An
3231 @code{exec} call replaces the program image of a process.
3233 @code{follow-exec-mode} can be:
3237 @value{GDBN} creates a new inferior and rebinds the process to this
3238 new inferior. The program the process was running before the
3239 @code{exec} call can be restarted afterwards by restarting the
3245 (@value{GDBP}) info inferiors
3247 Id Description Executable
3250 process 12020 is executing new program: prog2
3251 Program exited normally.
3252 (@value{GDBP}) info inferiors
3253 Id Description Executable
3259 @value{GDBN} keeps the process bound to the same inferior. The new
3260 executable image replaces the previous executable loaded in the
3261 inferior. Restarting the inferior after the @code{exec} call, with
3262 e.g., the @code{run} command, restarts the executable the process was
3263 running after the @code{exec} call. This is the default mode.
3268 (@value{GDBP}) info inferiors
3269 Id Description Executable
3272 process 12020 is executing new program: prog2
3273 Program exited normally.
3274 (@value{GDBP}) info inferiors
3275 Id Description Executable
3282 You can use the @code{catch} command to make @value{GDBN} stop whenever
3283 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3284 Catchpoints, ,Setting Catchpoints}.
3286 @node Checkpoint/Restart
3287 @section Setting a @emph{Bookmark} to Return to Later
3292 @cindex snapshot of a process
3293 @cindex rewind program state
3295 On certain operating systems@footnote{Currently, only
3296 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3297 program's state, called a @dfn{checkpoint}, and come back to it
3300 Returning to a checkpoint effectively undoes everything that has
3301 happened in the program since the @code{checkpoint} was saved. This
3302 includes changes in memory, registers, and even (within some limits)
3303 system state. Effectively, it is like going back in time to the
3304 moment when the checkpoint was saved.
3306 Thus, if you're stepping thru a program and you think you're
3307 getting close to the point where things go wrong, you can save
3308 a checkpoint. Then, if you accidentally go too far and miss
3309 the critical statement, instead of having to restart your program
3310 from the beginning, you can just go back to the checkpoint and
3311 start again from there.
3313 This can be especially useful if it takes a lot of time or
3314 steps to reach the point where you think the bug occurs.
3316 To use the @code{checkpoint}/@code{restart} method of debugging:
3321 Save a snapshot of the debugged program's current execution state.
3322 The @code{checkpoint} command takes no arguments, but each checkpoint
3323 is assigned a small integer id, similar to a breakpoint id.
3325 @kindex info checkpoints
3326 @item info checkpoints
3327 List the checkpoints that have been saved in the current debugging
3328 session. For each checkpoint, the following information will be
3335 @item Source line, or label
3338 @kindex restart @var{checkpoint-id}
3339 @item restart @var{checkpoint-id}
3340 Restore the program state that was saved as checkpoint number
3341 @var{checkpoint-id}. All program variables, registers, stack frames
3342 etc.@: will be returned to the values that they had when the checkpoint
3343 was saved. In essence, gdb will ``wind back the clock'' to the point
3344 in time when the checkpoint was saved.
3346 Note that breakpoints, @value{GDBN} variables, command history etc.
3347 are not affected by restoring a checkpoint. In general, a checkpoint
3348 only restores things that reside in the program being debugged, not in
3351 @kindex delete checkpoint @var{checkpoint-id}
3352 @item delete checkpoint @var{checkpoint-id}
3353 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3357 Returning to a previously saved checkpoint will restore the user state
3358 of the program being debugged, plus a significant subset of the system
3359 (OS) state, including file pointers. It won't ``un-write'' data from
3360 a file, but it will rewind the file pointer to the previous location,
3361 so that the previously written data can be overwritten. For files
3362 opened in read mode, the pointer will also be restored so that the
3363 previously read data can be read again.
3365 Of course, characters that have been sent to a printer (or other
3366 external device) cannot be ``snatched back'', and characters received
3367 from eg.@: a serial device can be removed from internal program buffers,
3368 but they cannot be ``pushed back'' into the serial pipeline, ready to
3369 be received again. Similarly, the actual contents of files that have
3370 been changed cannot be restored (at this time).
3372 However, within those constraints, you actually can ``rewind'' your
3373 program to a previously saved point in time, and begin debugging it
3374 again --- and you can change the course of events so as to debug a
3375 different execution path this time.
3377 @cindex checkpoints and process id
3378 Finally, there is one bit of internal program state that will be
3379 different when you return to a checkpoint --- the program's process
3380 id. Each checkpoint will have a unique process id (or @var{pid}),
3381 and each will be different from the program's original @var{pid}.
3382 If your program has saved a local copy of its process id, this could
3383 potentially pose a problem.
3385 @subsection A Non-obvious Benefit of Using Checkpoints
3387 On some systems such as @sc{gnu}/Linux, address space randomization
3388 is performed on new processes for security reasons. This makes it
3389 difficult or impossible to set a breakpoint, or watchpoint, on an
3390 absolute address if you have to restart the program, since the
3391 absolute location of a symbol will change from one execution to the
3394 A checkpoint, however, is an @emph{identical} copy of a process.
3395 Therefore if you create a checkpoint at (eg.@:) the start of main,
3396 and simply return to that checkpoint instead of restarting the
3397 process, you can avoid the effects of address randomization and
3398 your symbols will all stay in the same place.
3401 @chapter Stopping and Continuing
3403 The principal purposes of using a debugger are so that you can stop your
3404 program before it terminates; or so that, if your program runs into
3405 trouble, you can investigate and find out why.
3407 Inside @value{GDBN}, your program may stop for any of several reasons,
3408 such as a signal, a breakpoint, or reaching a new line after a
3409 @value{GDBN} command such as @code{step}. You may then examine and
3410 change variables, set new breakpoints or remove old ones, and then
3411 continue execution. Usually, the messages shown by @value{GDBN} provide
3412 ample explanation of the status of your program---but you can also
3413 explicitly request this information at any time.
3416 @kindex info program
3418 Display information about the status of your program: whether it is
3419 running or not, what process it is, and why it stopped.
3423 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3424 * Continuing and Stepping:: Resuming execution
3425 * Skipping Over Functions and Files::
3426 Skipping over functions and files
3428 * Thread Stops:: Stopping and starting multi-thread programs
3432 @section Breakpoints, Watchpoints, and Catchpoints
3435 A @dfn{breakpoint} makes your program stop whenever a certain point in
3436 the program is reached. For each breakpoint, you can add conditions to
3437 control in finer detail whether your program stops. You can set
3438 breakpoints with the @code{break} command and its variants (@pxref{Set
3439 Breaks, ,Setting Breakpoints}), to specify the place where your program
3440 should stop by line number, function name or exact address in the
3443 On some systems, you can set breakpoints in shared libraries before
3444 the executable is run. There is a minor limitation on HP-UX systems:
3445 you must wait until the executable is run in order to set breakpoints
3446 in shared library routines that are not called directly by the program
3447 (for example, routines that are arguments in a @code{pthread_create}
3451 @cindex data breakpoints
3452 @cindex memory tracing
3453 @cindex breakpoint on memory address
3454 @cindex breakpoint on variable modification
3455 A @dfn{watchpoint} is a special breakpoint that stops your program
3456 when the value of an expression changes. The expression may be a value
3457 of a variable, or it could involve values of one or more variables
3458 combined by operators, such as @samp{a + b}. This is sometimes called
3459 @dfn{data breakpoints}. You must use a different command to set
3460 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3461 from that, you can manage a watchpoint like any other breakpoint: you
3462 enable, disable, and delete both breakpoints and watchpoints using the
3465 You can arrange to have values from your program displayed automatically
3466 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3470 @cindex breakpoint on events
3471 A @dfn{catchpoint} is another special breakpoint that stops your program
3472 when a certain kind of event occurs, such as the throwing of a C@t{++}
3473 exception or the loading of a library. As with watchpoints, you use a
3474 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3475 Catchpoints}), but aside from that, you can manage a catchpoint like any
3476 other breakpoint. (To stop when your program receives a signal, use the
3477 @code{handle} command; see @ref{Signals, ,Signals}.)
3479 @cindex breakpoint numbers
3480 @cindex numbers for breakpoints
3481 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3482 catchpoint when you create it; these numbers are successive integers
3483 starting with one. In many of the commands for controlling various
3484 features of breakpoints you use the breakpoint number to say which
3485 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3486 @dfn{disabled}; if disabled, it has no effect on your program until you
3489 @cindex breakpoint ranges
3490 @cindex ranges of breakpoints
3491 Some @value{GDBN} commands accept a range of breakpoints on which to
3492 operate. A breakpoint range is either a single breakpoint number, like
3493 @samp{5}, or two such numbers, in increasing order, separated by a
3494 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3495 all breakpoints in that range are operated on.
3498 * Set Breaks:: Setting breakpoints
3499 * Set Watchpoints:: Setting watchpoints
3500 * Set Catchpoints:: Setting catchpoints
3501 * Delete Breaks:: Deleting breakpoints
3502 * Disabling:: Disabling breakpoints
3503 * Conditions:: Break conditions
3504 * Break Commands:: Breakpoint command lists
3505 * Dynamic Printf:: Dynamic printf
3506 * Save Breakpoints:: How to save breakpoints in a file
3507 * Static Probe Points:: Listing static probe points
3508 * Error in Breakpoints:: ``Cannot insert breakpoints''
3509 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3513 @subsection Setting Breakpoints
3515 @c FIXME LMB what does GDB do if no code on line of breakpt?
3516 @c consider in particular declaration with/without initialization.
3518 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3521 @kindex b @r{(@code{break})}
3522 @vindex $bpnum@r{, convenience variable}
3523 @cindex latest breakpoint
3524 Breakpoints are set with the @code{break} command (abbreviated
3525 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3526 number of the breakpoint you've set most recently; see @ref{Convenience
3527 Vars,, Convenience Variables}, for a discussion of what you can do with
3528 convenience variables.
3531 @item break @var{location}
3532 Set a breakpoint at the given @var{location}, which can specify a
3533 function name, a line number, or an address of an instruction.
3534 (@xref{Specify Location}, for a list of all the possible ways to
3535 specify a @var{location}.) The breakpoint will stop your program just
3536 before it executes any of the code in the specified @var{location}.
3538 When using source languages that permit overloading of symbols, such as
3539 C@t{++}, a function name may refer to more than one possible place to break.
3540 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3543 It is also possible to insert a breakpoint that will stop the program
3544 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3545 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3548 When called without any arguments, @code{break} sets a breakpoint at
3549 the next instruction to be executed in the selected stack frame
3550 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3551 innermost, this makes your program stop as soon as control
3552 returns to that frame. This is similar to the effect of a
3553 @code{finish} command in the frame inside the selected frame---except
3554 that @code{finish} does not leave an active breakpoint. If you use
3555 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3556 the next time it reaches the current location; this may be useful
3559 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3560 least one instruction has been executed. If it did not do this, you
3561 would be unable to proceed past a breakpoint without first disabling the
3562 breakpoint. This rule applies whether or not the breakpoint already
3563 existed when your program stopped.
3565 @item break @dots{} if @var{cond}
3566 Set a breakpoint with condition @var{cond}; evaluate the expression
3567 @var{cond} each time the breakpoint is reached, and stop only if the
3568 value is nonzero---that is, if @var{cond} evaluates as true.
3569 @samp{@dots{}} stands for one of the possible arguments described
3570 above (or no argument) specifying where to break. @xref{Conditions,
3571 ,Break Conditions}, for more information on breakpoint conditions.
3574 @item tbreak @var{args}
3575 Set a breakpoint enabled only for one stop. The @var{args} are the
3576 same as for the @code{break} command, and the breakpoint is set in the same
3577 way, but the breakpoint is automatically deleted after the first time your
3578 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3581 @cindex hardware breakpoints
3582 @item hbreak @var{args}
3583 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3584 @code{break} command and the breakpoint is set in the same way, but the
3585 breakpoint requires hardware support and some target hardware may not
3586 have this support. The main purpose of this is EPROM/ROM code
3587 debugging, so you can set a breakpoint at an instruction without
3588 changing the instruction. This can be used with the new trap-generation
3589 provided by SPARClite DSU and most x86-based targets. These targets
3590 will generate traps when a program accesses some data or instruction
3591 address that is assigned to the debug registers. However the hardware
3592 breakpoint registers can take a limited number of breakpoints. For
3593 example, on the DSU, only two data breakpoints can be set at a time, and
3594 @value{GDBN} will reject this command if more than two are used. Delete
3595 or disable unused hardware breakpoints before setting new ones
3596 (@pxref{Disabling, ,Disabling Breakpoints}).
3597 @xref{Conditions, ,Break Conditions}.
3598 For remote targets, you can restrict the number of hardware
3599 breakpoints @value{GDBN} will use, see @ref{set remote
3600 hardware-breakpoint-limit}.
3603 @item thbreak @var{args}
3604 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3605 are the same as for the @code{hbreak} command and the breakpoint is set in
3606 the same way. However, like the @code{tbreak} command,
3607 the breakpoint is automatically deleted after the
3608 first time your program stops there. Also, like the @code{hbreak}
3609 command, the breakpoint requires hardware support and some target hardware
3610 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3611 See also @ref{Conditions, ,Break Conditions}.
3614 @cindex regular expression
3615 @cindex breakpoints at functions matching a regexp
3616 @cindex set breakpoints in many functions
3617 @item rbreak @var{regex}
3618 Set breakpoints on all functions matching the regular expression
3619 @var{regex}. This command sets an unconditional breakpoint on all
3620 matches, printing a list of all breakpoints it set. Once these
3621 breakpoints are set, they are treated just like the breakpoints set with
3622 the @code{break} command. You can delete them, disable them, or make
3623 them conditional the same way as any other breakpoint.
3625 The syntax of the regular expression is the standard one used with tools
3626 like @file{grep}. Note that this is different from the syntax used by
3627 shells, so for instance @code{foo*} matches all functions that include
3628 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3629 @code{.*} leading and trailing the regular expression you supply, so to
3630 match only functions that begin with @code{foo}, use @code{^foo}.
3632 @cindex non-member C@t{++} functions, set breakpoint in
3633 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3634 breakpoints on overloaded functions that are not members of any special
3637 @cindex set breakpoints on all functions
3638 The @code{rbreak} command can be used to set breakpoints in
3639 @strong{all} the functions in a program, like this:
3642 (@value{GDBP}) rbreak .
3645 @item rbreak @var{file}:@var{regex}
3646 If @code{rbreak} is called with a filename qualification, it limits
3647 the search for functions matching the given regular expression to the
3648 specified @var{file}. This can be used, for example, to set breakpoints on
3649 every function in a given file:
3652 (@value{GDBP}) rbreak file.c:.
3655 The colon separating the filename qualifier from the regex may
3656 optionally be surrounded by spaces.
3658 @kindex info breakpoints
3659 @cindex @code{$_} and @code{info breakpoints}
3660 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3661 @itemx info break @r{[}@var{n}@dots{}@r{]}
3662 Print a table of all breakpoints, watchpoints, and catchpoints set and
3663 not deleted. Optional argument @var{n} means print information only
3664 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3665 For each breakpoint, following columns are printed:
3668 @item Breakpoint Numbers
3670 Breakpoint, watchpoint, or catchpoint.
3672 Whether the breakpoint is marked to be disabled or deleted when hit.
3673 @item Enabled or Disabled
3674 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3675 that are not enabled.
3677 Where the breakpoint is in your program, as a memory address. For a
3678 pending breakpoint whose address is not yet known, this field will
3679 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3680 library that has the symbol or line referred by breakpoint is loaded.
3681 See below for details. A breakpoint with several locations will
3682 have @samp{<MULTIPLE>} in this field---see below for details.
3684 Where the breakpoint is in the source for your program, as a file and
3685 line number. For a pending breakpoint, the original string passed to
3686 the breakpoint command will be listed as it cannot be resolved until
3687 the appropriate shared library is loaded in the future.
3691 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3692 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3693 @value{GDBN} on the host's side. If it is ``target'', then the condition
3694 is evaluated by the target. The @code{info break} command shows
3695 the condition on the line following the affected breakpoint, together with
3696 its condition evaluation mode in between parentheses.
3698 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3699 allowed to have a condition specified for it. The condition is not parsed for
3700 validity until a shared library is loaded that allows the pending
3701 breakpoint to resolve to a valid location.
3704 @code{info break} with a breakpoint
3705 number @var{n} as argument lists only that breakpoint. The
3706 convenience variable @code{$_} and the default examining-address for
3707 the @code{x} command are set to the address of the last breakpoint
3708 listed (@pxref{Memory, ,Examining Memory}).
3711 @code{info break} displays a count of the number of times the breakpoint
3712 has been hit. This is especially useful in conjunction with the
3713 @code{ignore} command. You can ignore a large number of breakpoint
3714 hits, look at the breakpoint info to see how many times the breakpoint
3715 was hit, and then run again, ignoring one less than that number. This
3716 will get you quickly to the last hit of that breakpoint.
3719 For a breakpoints with an enable count (xref) greater than 1,
3720 @code{info break} also displays that count.
3724 @value{GDBN} allows you to set any number of breakpoints at the same place in
3725 your program. There is nothing silly or meaningless about this. When
3726 the breakpoints are conditional, this is even useful
3727 (@pxref{Conditions, ,Break Conditions}).
3729 @cindex multiple locations, breakpoints
3730 @cindex breakpoints, multiple locations
3731 It is possible that a breakpoint corresponds to several locations
3732 in your program. Examples of this situation are:
3736 Multiple functions in the program may have the same name.
3739 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3740 instances of the function body, used in different cases.
3743 For a C@t{++} template function, a given line in the function can
3744 correspond to any number of instantiations.
3747 For an inlined function, a given source line can correspond to
3748 several places where that function is inlined.
3751 In all those cases, @value{GDBN} will insert a breakpoint at all
3752 the relevant locations.
3754 A breakpoint with multiple locations is displayed in the breakpoint
3755 table using several rows---one header row, followed by one row for
3756 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3757 address column. The rows for individual locations contain the actual
3758 addresses for locations, and show the functions to which those
3759 locations belong. The number column for a location is of the form
3760 @var{breakpoint-number}.@var{location-number}.
3765 Num Type Disp Enb Address What
3766 1 breakpoint keep y <MULTIPLE>
3768 breakpoint already hit 1 time
3769 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3770 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3773 Each location can be individually enabled or disabled by passing
3774 @var{breakpoint-number}.@var{location-number} as argument to the
3775 @code{enable} and @code{disable} commands. Note that you cannot
3776 delete the individual locations from the list, you can only delete the
3777 entire list of locations that belong to their parent breakpoint (with
3778 the @kbd{delete @var{num}} command, where @var{num} is the number of
3779 the parent breakpoint, 1 in the above example). Disabling or enabling
3780 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3781 that belong to that breakpoint.
3783 @cindex pending breakpoints
3784 It's quite common to have a breakpoint inside a shared library.
3785 Shared libraries can be loaded and unloaded explicitly,
3786 and possibly repeatedly, as the program is executed. To support
3787 this use case, @value{GDBN} updates breakpoint locations whenever
3788 any shared library is loaded or unloaded. Typically, you would
3789 set a breakpoint in a shared library at the beginning of your
3790 debugging session, when the library is not loaded, and when the
3791 symbols from the library are not available. When you try to set
3792 breakpoint, @value{GDBN} will ask you if you want to set
3793 a so called @dfn{pending breakpoint}---breakpoint whose address
3794 is not yet resolved.
3796 After the program is run, whenever a new shared library is loaded,
3797 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3798 shared library contains the symbol or line referred to by some
3799 pending breakpoint, that breakpoint is resolved and becomes an
3800 ordinary breakpoint. When a library is unloaded, all breakpoints
3801 that refer to its symbols or source lines become pending again.
3803 This logic works for breakpoints with multiple locations, too. For
3804 example, if you have a breakpoint in a C@t{++} template function, and
3805 a newly loaded shared library has an instantiation of that template,
3806 a new location is added to the list of locations for the breakpoint.
3808 Except for having unresolved address, pending breakpoints do not
3809 differ from regular breakpoints. You can set conditions or commands,
3810 enable and disable them and perform other breakpoint operations.
3812 @value{GDBN} provides some additional commands for controlling what
3813 happens when the @samp{break} command cannot resolve breakpoint
3814 address specification to an address:
3816 @kindex set breakpoint pending
3817 @kindex show breakpoint pending
3819 @item set breakpoint pending auto
3820 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3821 location, it queries you whether a pending breakpoint should be created.
3823 @item set breakpoint pending on
3824 This indicates that an unrecognized breakpoint location should automatically
3825 result in a pending breakpoint being created.
3827 @item set breakpoint pending off
3828 This indicates that pending breakpoints are not to be created. Any
3829 unrecognized breakpoint location results in an error. This setting does
3830 not affect any pending breakpoints previously created.
3832 @item show breakpoint pending
3833 Show the current behavior setting for creating pending breakpoints.
3836 The settings above only affect the @code{break} command and its
3837 variants. Once breakpoint is set, it will be automatically updated
3838 as shared libraries are loaded and unloaded.
3840 @cindex automatic hardware breakpoints
3841 For some targets, @value{GDBN} can automatically decide if hardware or
3842 software breakpoints should be used, depending on whether the
3843 breakpoint address is read-only or read-write. This applies to
3844 breakpoints set with the @code{break} command as well as to internal
3845 breakpoints set by commands like @code{next} and @code{finish}. For
3846 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3849 You can control this automatic behaviour with the following commands::
3851 @kindex set breakpoint auto-hw
3852 @kindex show breakpoint auto-hw
3854 @item set breakpoint auto-hw on
3855 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3856 will try to use the target memory map to decide if software or hardware
3857 breakpoint must be used.
3859 @item set breakpoint auto-hw off
3860 This indicates @value{GDBN} should not automatically select breakpoint
3861 type. If the target provides a memory map, @value{GDBN} will warn when
3862 trying to set software breakpoint at a read-only address.
3865 @value{GDBN} normally implements breakpoints by replacing the program code
3866 at the breakpoint address with a special instruction, which, when
3867 executed, given control to the debugger. By default, the program
3868 code is so modified only when the program is resumed. As soon as
3869 the program stops, @value{GDBN} restores the original instructions. This
3870 behaviour guards against leaving breakpoints inserted in the
3871 target should gdb abrubptly disconnect. However, with slow remote
3872 targets, inserting and removing breakpoint can reduce the performance.
3873 This behavior can be controlled with the following commands::
3875 @kindex set breakpoint always-inserted
3876 @kindex show breakpoint always-inserted
3878 @item set breakpoint always-inserted off
3879 All breakpoints, including newly added by the user, are inserted in
3880 the target only when the target is resumed. All breakpoints are
3881 removed from the target when it stops. This is the default mode.
3883 @item set breakpoint always-inserted on
3884 Causes all breakpoints to be inserted in the target at all times. If
3885 the user adds a new breakpoint, or changes an existing breakpoint, the
3886 breakpoints in the target are updated immediately. A breakpoint is
3887 removed from the target only when breakpoint itself is deleted.
3890 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3891 when a breakpoint breaks. If the condition is true, then the process being
3892 debugged stops, otherwise the process is resumed.
3894 If the target supports evaluating conditions on its end, @value{GDBN} may
3895 download the breakpoint, together with its conditions, to it.
3897 This feature can be controlled via the following commands:
3899 @kindex set breakpoint condition-evaluation
3900 @kindex show breakpoint condition-evaluation
3902 @item set breakpoint condition-evaluation host
3903 This option commands @value{GDBN} to evaluate the breakpoint
3904 conditions on the host's side. Unconditional breakpoints are sent to
3905 the target which in turn receives the triggers and reports them back to GDB
3906 for condition evaluation. This is the standard evaluation mode.
3908 @item set breakpoint condition-evaluation target
3909 This option commands @value{GDBN} to download breakpoint conditions
3910 to the target at the moment of their insertion. The target
3911 is responsible for evaluating the conditional expression and reporting
3912 breakpoint stop events back to @value{GDBN} whenever the condition
3913 is true. Due to limitations of target-side evaluation, some conditions
3914 cannot be evaluated there, e.g., conditions that depend on local data
3915 that is only known to the host. Examples include
3916 conditional expressions involving convenience variables, complex types
3917 that cannot be handled by the agent expression parser and expressions
3918 that are too long to be sent over to the target, specially when the
3919 target is a remote system. In these cases, the conditions will be
3920 evaluated by @value{GDBN}.
3922 @item set breakpoint condition-evaluation auto
3923 This is the default mode. If the target supports evaluating breakpoint
3924 conditions on its end, @value{GDBN} will download breakpoint conditions to
3925 the target (limitations mentioned previously apply). If the target does
3926 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3927 to evaluating all these conditions on the host's side.
3931 @cindex negative breakpoint numbers
3932 @cindex internal @value{GDBN} breakpoints
3933 @value{GDBN} itself sometimes sets breakpoints in your program for
3934 special purposes, such as proper handling of @code{longjmp} (in C
3935 programs). These internal breakpoints are assigned negative numbers,
3936 starting with @code{-1}; @samp{info breakpoints} does not display them.
3937 You can see these breakpoints with the @value{GDBN} maintenance command
3938 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3941 @node Set Watchpoints
3942 @subsection Setting Watchpoints
3944 @cindex setting watchpoints
3945 You can use a watchpoint to stop execution whenever the value of an
3946 expression changes, without having to predict a particular place where
3947 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3948 The expression may be as simple as the value of a single variable, or
3949 as complex as many variables combined by operators. Examples include:
3953 A reference to the value of a single variable.
3956 An address cast to an appropriate data type. For example,
3957 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3958 address (assuming an @code{int} occupies 4 bytes).
3961 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3962 expression can use any operators valid in the program's native
3963 language (@pxref{Languages}).
3966 You can set a watchpoint on an expression even if the expression can
3967 not be evaluated yet. For instance, you can set a watchpoint on
3968 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3969 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3970 the expression produces a valid value. If the expression becomes
3971 valid in some other way than changing a variable (e.g.@: if the memory
3972 pointed to by @samp{*global_ptr} becomes readable as the result of a
3973 @code{malloc} call), @value{GDBN} may not stop until the next time
3974 the expression changes.
3976 @cindex software watchpoints
3977 @cindex hardware watchpoints
3978 Depending on your system, watchpoints may be implemented in software or
3979 hardware. @value{GDBN} does software watchpointing by single-stepping your
3980 program and testing the variable's value each time, which is hundreds of
3981 times slower than normal execution. (But this may still be worth it, to
3982 catch errors where you have no clue what part of your program is the
3985 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3986 x86-based targets, @value{GDBN} includes support for hardware
3987 watchpoints, which do not slow down the running of your program.
3991 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3992 Set a watchpoint for an expression. @value{GDBN} will break when the
3993 expression @var{expr} is written into by the program and its value
3994 changes. The simplest (and the most popular) use of this command is
3995 to watch the value of a single variable:
3998 (@value{GDBP}) watch foo
4001 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
4002 argument, @value{GDBN} breaks only when the thread identified by
4003 @var{threadnum} changes the value of @var{expr}. If any other threads
4004 change the value of @var{expr}, @value{GDBN} will not break. Note
4005 that watchpoints restricted to a single thread in this way only work
4006 with Hardware Watchpoints.
4008 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4009 (see below). The @code{-location} argument tells @value{GDBN} to
4010 instead watch the memory referred to by @var{expr}. In this case,
4011 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4012 and watch the memory at that address. The type of the result is used
4013 to determine the size of the watched memory. If the expression's
4014 result does not have an address, then @value{GDBN} will print an
4017 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4018 of masked watchpoints, if the current architecture supports this
4019 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4020 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4021 to an address to watch. The mask specifies that some bits of an address
4022 (the bits which are reset in the mask) should be ignored when matching
4023 the address accessed by the inferior against the watchpoint address.
4024 Thus, a masked watchpoint watches many addresses simultaneously---those
4025 addresses whose unmasked bits are identical to the unmasked bits in the
4026 watchpoint address. The @code{mask} argument implies @code{-location}.
4030 (@value{GDBP}) watch foo mask 0xffff00ff
4031 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4035 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4036 Set a watchpoint that will break when the value of @var{expr} is read
4040 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
4041 Set a watchpoint that will break when @var{expr} is either read from
4042 or written into by the program.
4044 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4045 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4046 This command prints a list of watchpoints, using the same format as
4047 @code{info break} (@pxref{Set Breaks}).
4050 If you watch for a change in a numerically entered address you need to
4051 dereference it, as the address itself is just a constant number which will
4052 never change. @value{GDBN} refuses to create a watchpoint that watches
4053 a never-changing value:
4056 (@value{GDBP}) watch 0x600850
4057 Cannot watch constant value 0x600850.
4058 (@value{GDBP}) watch *(int *) 0x600850
4059 Watchpoint 1: *(int *) 6293584
4062 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4063 watchpoints execute very quickly, and the debugger reports a change in
4064 value at the exact instruction where the change occurs. If @value{GDBN}
4065 cannot set a hardware watchpoint, it sets a software watchpoint, which
4066 executes more slowly and reports the change in value at the next
4067 @emph{statement}, not the instruction, after the change occurs.
4069 @cindex use only software watchpoints
4070 You can force @value{GDBN} to use only software watchpoints with the
4071 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4072 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4073 the underlying system supports them. (Note that hardware-assisted
4074 watchpoints that were set @emph{before} setting
4075 @code{can-use-hw-watchpoints} to zero will still use the hardware
4076 mechanism of watching expression values.)
4079 @item set can-use-hw-watchpoints
4080 @kindex set can-use-hw-watchpoints
4081 Set whether or not to use hardware watchpoints.
4083 @item show can-use-hw-watchpoints
4084 @kindex show can-use-hw-watchpoints
4085 Show the current mode of using hardware watchpoints.
4088 For remote targets, you can restrict the number of hardware
4089 watchpoints @value{GDBN} will use, see @ref{set remote
4090 hardware-breakpoint-limit}.
4092 When you issue the @code{watch} command, @value{GDBN} reports
4095 Hardware watchpoint @var{num}: @var{expr}
4099 if it was able to set a hardware watchpoint.
4101 Currently, the @code{awatch} and @code{rwatch} commands can only set
4102 hardware watchpoints, because accesses to data that don't change the
4103 value of the watched expression cannot be detected without examining
4104 every instruction as it is being executed, and @value{GDBN} does not do
4105 that currently. If @value{GDBN} finds that it is unable to set a
4106 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4107 will print a message like this:
4110 Expression cannot be implemented with read/access watchpoint.
4113 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4114 data type of the watched expression is wider than what a hardware
4115 watchpoint on the target machine can handle. For example, some systems
4116 can only watch regions that are up to 4 bytes wide; on such systems you
4117 cannot set hardware watchpoints for an expression that yields a
4118 double-precision floating-point number (which is typically 8 bytes
4119 wide). As a work-around, it might be possible to break the large region
4120 into a series of smaller ones and watch them with separate watchpoints.
4122 If you set too many hardware watchpoints, @value{GDBN} might be unable
4123 to insert all of them when you resume the execution of your program.
4124 Since the precise number of active watchpoints is unknown until such
4125 time as the program is about to be resumed, @value{GDBN} might not be
4126 able to warn you about this when you set the watchpoints, and the
4127 warning will be printed only when the program is resumed:
4130 Hardware watchpoint @var{num}: Could not insert watchpoint
4134 If this happens, delete or disable some of the watchpoints.
4136 Watching complex expressions that reference many variables can also
4137 exhaust the resources available for hardware-assisted watchpoints.
4138 That's because @value{GDBN} needs to watch every variable in the
4139 expression with separately allocated resources.
4141 If you call a function interactively using @code{print} or @code{call},
4142 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4143 kind of breakpoint or the call completes.
4145 @value{GDBN} automatically deletes watchpoints that watch local
4146 (automatic) variables, or expressions that involve such variables, when
4147 they go out of scope, that is, when the execution leaves the block in
4148 which these variables were defined. In particular, when the program
4149 being debugged terminates, @emph{all} local variables go out of scope,
4150 and so only watchpoints that watch global variables remain set. If you
4151 rerun the program, you will need to set all such watchpoints again. One
4152 way of doing that would be to set a code breakpoint at the entry to the
4153 @code{main} function and when it breaks, set all the watchpoints.
4155 @cindex watchpoints and threads
4156 @cindex threads and watchpoints
4157 In multi-threaded programs, watchpoints will detect changes to the
4158 watched expression from every thread.
4161 @emph{Warning:} In multi-threaded programs, software watchpoints
4162 have only limited usefulness. If @value{GDBN} creates a software
4163 watchpoint, it can only watch the value of an expression @emph{in a
4164 single thread}. If you are confident that the expression can only
4165 change due to the current thread's activity (and if you are also
4166 confident that no other thread can become current), then you can use
4167 software watchpoints as usual. However, @value{GDBN} may not notice
4168 when a non-current thread's activity changes the expression. (Hardware
4169 watchpoints, in contrast, watch an expression in all threads.)
4172 @xref{set remote hardware-watchpoint-limit}.
4174 @node Set Catchpoints
4175 @subsection Setting Catchpoints
4176 @cindex catchpoints, setting
4177 @cindex exception handlers
4178 @cindex event handling
4180 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4181 kinds of program events, such as C@t{++} exceptions or the loading of a
4182 shared library. Use the @code{catch} command to set a catchpoint.
4186 @item catch @var{event}
4187 Stop when @var{event} occurs. The @var{event} can be any of the following:
4190 @item throw @r{[}@var{regexp}@r{]}
4191 @itemx rethrow @r{[}@var{regexp}@r{]}
4192 @itemx catch @r{[}@var{regexp}@r{]}
4194 @kindex catch rethrow
4196 @cindex stop on C@t{++} exceptions
4197 The throwing, re-throwing, or catching of a C@t{++} exception.
4199 If @var{regexp} is given, then only exceptions whose type matches the
4200 regular expression will be caught.
4202 @vindex $_exception@r{, convenience variable}
4203 The convenience variable @code{$_exception} is available at an
4204 exception-related catchpoint, on some systems. This holds the
4205 exception being thrown.
4207 There are currently some limitations to C@t{++} exception handling in
4212 The support for these commands is system-dependent. Currently, only
4213 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4217 The regular expression feature and the @code{$_exception} convenience
4218 variable rely on the presence of some SDT probes in @code{libstdc++}.
4219 If these probes are not present, then these features cannot be used.
4220 These probes were first available in the GCC 4.8 release, but whether
4221 or not they are available in your GCC also depends on how it was
4225 The @code{$_exception} convenience variable is only valid at the
4226 instruction at which an exception-related catchpoint is set.
4229 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4230 location in the system library which implements runtime exception
4231 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4232 (@pxref{Selection}) to get to your code.
4235 If you call a function interactively, @value{GDBN} normally returns
4236 control to you when the function has finished executing. If the call
4237 raises an exception, however, the call may bypass the mechanism that
4238 returns control to you and cause your program either to abort or to
4239 simply continue running until it hits a breakpoint, catches a signal
4240 that @value{GDBN} is listening for, or exits. This is the case even if
4241 you set a catchpoint for the exception; catchpoints on exceptions are
4242 disabled within interactive calls. @xref{Calling}, for information on
4243 controlling this with @code{set unwind-on-terminating-exception}.
4246 You cannot raise an exception interactively.
4249 You cannot install an exception handler interactively.
4253 @kindex catch exception
4254 @cindex Ada exception catching
4255 @cindex catch Ada exceptions
4256 An Ada exception being raised. If an exception name is specified
4257 at the end of the command (eg @code{catch exception Program_Error}),
4258 the debugger will stop only when this specific exception is raised.
4259 Otherwise, the debugger stops execution when any Ada exception is raised.
4261 When inserting an exception catchpoint on a user-defined exception whose
4262 name is identical to one of the exceptions defined by the language, the
4263 fully qualified name must be used as the exception name. Otherwise,
4264 @value{GDBN} will assume that it should stop on the pre-defined exception
4265 rather than the user-defined one. For instance, assuming an exception
4266 called @code{Constraint_Error} is defined in package @code{Pck}, then
4267 the command to use to catch such exceptions is @kbd{catch exception
4268 Pck.Constraint_Error}.
4270 @item exception unhandled
4271 @kindex catch exception unhandled
4272 An exception that was raised but is not handled by the program.
4275 @kindex catch assert
4276 A failed Ada assertion.
4280 @cindex break on fork/exec
4281 A call to @code{exec}. This is currently only available for HP-UX
4285 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4286 @kindex catch syscall
4287 @cindex break on a system call.
4288 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4289 syscall is a mechanism for application programs to request a service
4290 from the operating system (OS) or one of the OS system services.
4291 @value{GDBN} can catch some or all of the syscalls issued by the
4292 debuggee, and show the related information for each syscall. If no
4293 argument is specified, calls to and returns from all system calls
4296 @var{name} can be any system call name that is valid for the
4297 underlying OS. Just what syscalls are valid depends on the OS. On
4298 GNU and Unix systems, you can find the full list of valid syscall
4299 names on @file{/usr/include/asm/unistd.h}.
4301 @c For MS-Windows, the syscall names and the corresponding numbers
4302 @c can be found, e.g., on this URL:
4303 @c http://www.metasploit.com/users/opcode/syscalls.html
4304 @c but we don't support Windows syscalls yet.
4306 Normally, @value{GDBN} knows in advance which syscalls are valid for
4307 each OS, so you can use the @value{GDBN} command-line completion
4308 facilities (@pxref{Completion,, command completion}) to list the
4311 You may also specify the system call numerically. A syscall's
4312 number is the value passed to the OS's syscall dispatcher to
4313 identify the requested service. When you specify the syscall by its
4314 name, @value{GDBN} uses its database of syscalls to convert the name
4315 into the corresponding numeric code, but using the number directly
4316 may be useful if @value{GDBN}'s database does not have the complete
4317 list of syscalls on your system (e.g., because @value{GDBN} lags
4318 behind the OS upgrades).
4320 The example below illustrates how this command works if you don't provide
4324 (@value{GDBP}) catch syscall
4325 Catchpoint 1 (syscall)
4327 Starting program: /tmp/catch-syscall
4329 Catchpoint 1 (call to syscall 'close'), \
4330 0xffffe424 in __kernel_vsyscall ()
4334 Catchpoint 1 (returned from syscall 'close'), \
4335 0xffffe424 in __kernel_vsyscall ()
4339 Here is an example of catching a system call by name:
4342 (@value{GDBP}) catch syscall chroot
4343 Catchpoint 1 (syscall 'chroot' [61])
4345 Starting program: /tmp/catch-syscall
4347 Catchpoint 1 (call to syscall 'chroot'), \
4348 0xffffe424 in __kernel_vsyscall ()
4352 Catchpoint 1 (returned from syscall 'chroot'), \
4353 0xffffe424 in __kernel_vsyscall ()
4357 An example of specifying a system call numerically. In the case
4358 below, the syscall number has a corresponding entry in the XML
4359 file, so @value{GDBN} finds its name and prints it:
4362 (@value{GDBP}) catch syscall 252
4363 Catchpoint 1 (syscall(s) 'exit_group')
4365 Starting program: /tmp/catch-syscall
4367 Catchpoint 1 (call to syscall 'exit_group'), \
4368 0xffffe424 in __kernel_vsyscall ()
4372 Program exited normally.
4376 However, there can be situations when there is no corresponding name
4377 in XML file for that syscall number. In this case, @value{GDBN} prints
4378 a warning message saying that it was not able to find the syscall name,
4379 but the catchpoint will be set anyway. See the example below:
4382 (@value{GDBP}) catch syscall 764
4383 warning: The number '764' does not represent a known syscall.
4384 Catchpoint 2 (syscall 764)
4388 If you configure @value{GDBN} using the @samp{--without-expat} option,
4389 it will not be able to display syscall names. Also, if your
4390 architecture does not have an XML file describing its system calls,
4391 you will not be able to see the syscall names. It is important to
4392 notice that these two features are used for accessing the syscall
4393 name database. In either case, you will see a warning like this:
4396 (@value{GDBP}) catch syscall
4397 warning: Could not open "syscalls/i386-linux.xml"
4398 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4399 GDB will not be able to display syscall names.
4400 Catchpoint 1 (syscall)
4404 Of course, the file name will change depending on your architecture and system.
4406 Still using the example above, you can also try to catch a syscall by its
4407 number. In this case, you would see something like:
4410 (@value{GDBP}) catch syscall 252
4411 Catchpoint 1 (syscall(s) 252)
4414 Again, in this case @value{GDBN} would not be able to display syscall's names.
4418 A call to @code{fork}. This is currently only available for HP-UX
4423 A call to @code{vfork}. This is currently only available for HP-UX
4426 @item load @r{[}regexp@r{]}
4427 @itemx unload @r{[}regexp@r{]}
4429 @kindex catch unload
4430 The loading or unloading of a shared library. If @var{regexp} is
4431 given, then the catchpoint will stop only if the regular expression
4432 matches one of the affected libraries.
4434 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4435 @kindex catch signal
4436 The delivery of a signal.
4438 With no arguments, this catchpoint will catch any signal that is not
4439 used internally by @value{GDBN}, specifically, all signals except
4440 @samp{SIGTRAP} and @samp{SIGINT}.
4442 With the argument @samp{all}, all signals, including those used by
4443 @value{GDBN}, will be caught. This argument cannot be used with other
4446 Otherwise, the arguments are a list of signal names as given to
4447 @code{handle} (@pxref{Signals}). Only signals specified in this list
4450 One reason that @code{catch signal} can be more useful than
4451 @code{handle} is that you can attach commands and conditions to the
4454 When a signal is caught by a catchpoint, the signal's @code{stop} and
4455 @code{print} settings, as specified by @code{handle}, are ignored.
4456 However, whether the signal is still delivered to the inferior depends
4457 on the @code{pass} setting; this can be changed in the catchpoint's
4462 @item tcatch @var{event}
4464 Set a catchpoint that is enabled only for one stop. The catchpoint is
4465 automatically deleted after the first time the event is caught.
4469 Use the @code{info break} command to list the current catchpoints.
4473 @subsection Deleting Breakpoints
4475 @cindex clearing breakpoints, watchpoints, catchpoints
4476 @cindex deleting breakpoints, watchpoints, catchpoints
4477 It is often necessary to eliminate a breakpoint, watchpoint, or
4478 catchpoint once it has done its job and you no longer want your program
4479 to stop there. This is called @dfn{deleting} the breakpoint. A
4480 breakpoint that has been deleted no longer exists; it is forgotten.
4482 With the @code{clear} command you can delete breakpoints according to
4483 where they are in your program. With the @code{delete} command you can
4484 delete individual breakpoints, watchpoints, or catchpoints by specifying
4485 their breakpoint numbers.
4487 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4488 automatically ignores breakpoints on the first instruction to be executed
4489 when you continue execution without changing the execution address.
4494 Delete any breakpoints at the next instruction to be executed in the
4495 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4496 the innermost frame is selected, this is a good way to delete a
4497 breakpoint where your program just stopped.
4499 @item clear @var{location}
4500 Delete any breakpoints set at the specified @var{location}.
4501 @xref{Specify Location}, for the various forms of @var{location}; the
4502 most useful ones are listed below:
4505 @item clear @var{function}
4506 @itemx clear @var{filename}:@var{function}
4507 Delete any breakpoints set at entry to the named @var{function}.
4509 @item clear @var{linenum}
4510 @itemx clear @var{filename}:@var{linenum}
4511 Delete any breakpoints set at or within the code of the specified
4512 @var{linenum} of the specified @var{filename}.
4515 @cindex delete breakpoints
4517 @kindex d @r{(@code{delete})}
4518 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4519 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4520 ranges specified as arguments. If no argument is specified, delete all
4521 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4522 confirm off}). You can abbreviate this command as @code{d}.
4526 @subsection Disabling Breakpoints
4528 @cindex enable/disable a breakpoint
4529 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4530 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4531 it had been deleted, but remembers the information on the breakpoint so
4532 that you can @dfn{enable} it again later.
4534 You disable and enable breakpoints, watchpoints, and catchpoints with
4535 the @code{enable} and @code{disable} commands, optionally specifying
4536 one or more breakpoint numbers as arguments. Use @code{info break} to
4537 print a list of all breakpoints, watchpoints, and catchpoints if you
4538 do not know which numbers to use.
4540 Disabling and enabling a breakpoint that has multiple locations
4541 affects all of its locations.
4543 A breakpoint, watchpoint, or catchpoint can have any of several
4544 different states of enablement:
4548 Enabled. The breakpoint stops your program. A breakpoint set
4549 with the @code{break} command starts out in this state.
4551 Disabled. The breakpoint has no effect on your program.
4553 Enabled once. The breakpoint stops your program, but then becomes
4556 Enabled for a count. The breakpoint stops your program for the next
4557 N times, then becomes disabled.
4559 Enabled for deletion. The breakpoint stops your program, but
4560 immediately after it does so it is deleted permanently. A breakpoint
4561 set with the @code{tbreak} command starts out in this state.
4564 You can use the following commands to enable or disable breakpoints,
4565 watchpoints, and catchpoints:
4569 @kindex dis @r{(@code{disable})}
4570 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4571 Disable the specified breakpoints---or all breakpoints, if none are
4572 listed. A disabled breakpoint has no effect but is not forgotten. All
4573 options such as ignore-counts, conditions and commands are remembered in
4574 case the breakpoint is enabled again later. You may abbreviate
4575 @code{disable} as @code{dis}.
4578 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4579 Enable the specified breakpoints (or all defined breakpoints). They
4580 become effective once again in stopping your program.
4582 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4583 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4584 of these breakpoints immediately after stopping your program.
4586 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4587 Enable the specified breakpoints temporarily. @value{GDBN} records
4588 @var{count} with each of the specified breakpoints, and decrements a
4589 breakpoint's count when it is hit. When any count reaches 0,
4590 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4591 count (@pxref{Conditions, ,Break Conditions}), that will be
4592 decremented to 0 before @var{count} is affected.
4594 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4595 Enable the specified breakpoints to work once, then die. @value{GDBN}
4596 deletes any of these breakpoints as soon as your program stops there.
4597 Breakpoints set by the @code{tbreak} command start out in this state.
4600 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4601 @c confusing: tbreak is also initially enabled.
4602 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4603 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4604 subsequently, they become disabled or enabled only when you use one of
4605 the commands above. (The command @code{until} can set and delete a
4606 breakpoint of its own, but it does not change the state of your other
4607 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4611 @subsection Break Conditions
4612 @cindex conditional breakpoints
4613 @cindex breakpoint conditions
4615 @c FIXME what is scope of break condition expr? Context where wanted?
4616 @c in particular for a watchpoint?
4617 The simplest sort of breakpoint breaks every time your program reaches a
4618 specified place. You can also specify a @dfn{condition} for a
4619 breakpoint. A condition is just a Boolean expression in your
4620 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4621 a condition evaluates the expression each time your program reaches it,
4622 and your program stops only if the condition is @emph{true}.
4624 This is the converse of using assertions for program validation; in that
4625 situation, you want to stop when the assertion is violated---that is,
4626 when the condition is false. In C, if you want to test an assertion expressed
4627 by the condition @var{assert}, you should set the condition
4628 @samp{! @var{assert}} on the appropriate breakpoint.
4630 Conditions are also accepted for watchpoints; you may not need them,
4631 since a watchpoint is inspecting the value of an expression anyhow---but
4632 it might be simpler, say, to just set a watchpoint on a variable name,
4633 and specify a condition that tests whether the new value is an interesting
4636 Break conditions can have side effects, and may even call functions in
4637 your program. This can be useful, for example, to activate functions
4638 that log program progress, or to use your own print functions to
4639 format special data structures. The effects are completely predictable
4640 unless there is another enabled breakpoint at the same address. (In
4641 that case, @value{GDBN} might see the other breakpoint first and stop your
4642 program without checking the condition of this one.) Note that
4643 breakpoint commands are usually more convenient and flexible than break
4645 purpose of performing side effects when a breakpoint is reached
4646 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4648 Breakpoint conditions can also be evaluated on the target's side if
4649 the target supports it. Instead of evaluating the conditions locally,
4650 @value{GDBN} encodes the expression into an agent expression
4651 (@pxref{Agent Expressions}) suitable for execution on the target,
4652 independently of @value{GDBN}. Global variables become raw memory
4653 locations, locals become stack accesses, and so forth.
4655 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4656 when its condition evaluates to true. This mechanism may provide faster
4657 response times depending on the performance characteristics of the target
4658 since it does not need to keep @value{GDBN} informed about
4659 every breakpoint trigger, even those with false conditions.
4661 Break conditions can be specified when a breakpoint is set, by using
4662 @samp{if} in the arguments to the @code{break} command. @xref{Set
4663 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4664 with the @code{condition} command.
4666 You can also use the @code{if} keyword with the @code{watch} command.
4667 The @code{catch} command does not recognize the @code{if} keyword;
4668 @code{condition} is the only way to impose a further condition on a
4673 @item condition @var{bnum} @var{expression}
4674 Specify @var{expression} as the break condition for breakpoint,
4675 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4676 breakpoint @var{bnum} stops your program only if the value of
4677 @var{expression} is true (nonzero, in C). When you use
4678 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4679 syntactic correctness, and to determine whether symbols in it have
4680 referents in the context of your breakpoint. If @var{expression} uses
4681 symbols not referenced in the context of the breakpoint, @value{GDBN}
4682 prints an error message:
4685 No symbol "foo" in current context.
4690 not actually evaluate @var{expression} at the time the @code{condition}
4691 command (or a command that sets a breakpoint with a condition, like
4692 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4694 @item condition @var{bnum}
4695 Remove the condition from breakpoint number @var{bnum}. It becomes
4696 an ordinary unconditional breakpoint.
4699 @cindex ignore count (of breakpoint)
4700 A special case of a breakpoint condition is to stop only when the
4701 breakpoint has been reached a certain number of times. This is so
4702 useful that there is a special way to do it, using the @dfn{ignore
4703 count} of the breakpoint. Every breakpoint has an ignore count, which
4704 is an integer. Most of the time, the ignore count is zero, and
4705 therefore has no effect. But if your program reaches a breakpoint whose
4706 ignore count is positive, then instead of stopping, it just decrements
4707 the ignore count by one and continues. As a result, if the ignore count
4708 value is @var{n}, the breakpoint does not stop the next @var{n} times
4709 your program reaches it.
4713 @item ignore @var{bnum} @var{count}
4714 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4715 The next @var{count} times the breakpoint is reached, your program's
4716 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4719 To make the breakpoint stop the next time it is reached, specify
4722 When you use @code{continue} to resume execution of your program from a
4723 breakpoint, you can specify an ignore count directly as an argument to
4724 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4725 Stepping,,Continuing and Stepping}.
4727 If a breakpoint has a positive ignore count and a condition, the
4728 condition is not checked. Once the ignore count reaches zero,
4729 @value{GDBN} resumes checking the condition.
4731 You could achieve the effect of the ignore count with a condition such
4732 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4733 is decremented each time. @xref{Convenience Vars, ,Convenience
4737 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4740 @node Break Commands
4741 @subsection Breakpoint Command Lists
4743 @cindex breakpoint commands
4744 You can give any breakpoint (or watchpoint or catchpoint) a series of
4745 commands to execute when your program stops due to that breakpoint. For
4746 example, you might want to print the values of certain expressions, or
4747 enable other breakpoints.
4751 @kindex end@r{ (breakpoint commands)}
4752 @item commands @r{[}@var{range}@dots{}@r{]}
4753 @itemx @dots{} @var{command-list} @dots{}
4755 Specify a list of commands for the given breakpoints. The commands
4756 themselves appear on the following lines. Type a line containing just
4757 @code{end} to terminate the commands.
4759 To remove all commands from a breakpoint, type @code{commands} and
4760 follow it immediately with @code{end}; that is, give no commands.
4762 With no argument, @code{commands} refers to the last breakpoint,
4763 watchpoint, or catchpoint set (not to the breakpoint most recently
4764 encountered). If the most recent breakpoints were set with a single
4765 command, then the @code{commands} will apply to all the breakpoints
4766 set by that command. This applies to breakpoints set by
4767 @code{rbreak}, and also applies when a single @code{break} command
4768 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4772 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4773 disabled within a @var{command-list}.
4775 You can use breakpoint commands to start your program up again. Simply
4776 use the @code{continue} command, or @code{step}, or any other command
4777 that resumes execution.
4779 Any other commands in the command list, after a command that resumes
4780 execution, are ignored. This is because any time you resume execution
4781 (even with a simple @code{next} or @code{step}), you may encounter
4782 another breakpoint---which could have its own command list, leading to
4783 ambiguities about which list to execute.
4786 If the first command you specify in a command list is @code{silent}, the
4787 usual message about stopping at a breakpoint is not printed. This may
4788 be desirable for breakpoints that are to print a specific message and
4789 then continue. If none of the remaining commands print anything, you
4790 see no sign that the breakpoint was reached. @code{silent} is
4791 meaningful only at the beginning of a breakpoint command list.
4793 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4794 print precisely controlled output, and are often useful in silent
4795 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4797 For example, here is how you could use breakpoint commands to print the
4798 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4804 printf "x is %d\n",x
4809 One application for breakpoint commands is to compensate for one bug so
4810 you can test for another. Put a breakpoint just after the erroneous line
4811 of code, give it a condition to detect the case in which something
4812 erroneous has been done, and give it commands to assign correct values
4813 to any variables that need them. End with the @code{continue} command
4814 so that your program does not stop, and start with the @code{silent}
4815 command so that no output is produced. Here is an example:
4826 @node Dynamic Printf
4827 @subsection Dynamic Printf
4829 @cindex dynamic printf
4831 The dynamic printf command @code{dprintf} combines a breakpoint with
4832 formatted printing of your program's data to give you the effect of
4833 inserting @code{printf} calls into your program on-the-fly, without
4834 having to recompile it.
4836 In its most basic form, the output goes to the GDB console. However,
4837 you can set the variable @code{dprintf-style} for alternate handling.
4838 For instance, you can ask to format the output by calling your
4839 program's @code{printf} function. This has the advantage that the
4840 characters go to the program's output device, so they can recorded in
4841 redirects to files and so forth.
4843 If you are doing remote debugging with a stub or agent, you can also
4844 ask to have the printf handled by the remote agent. In addition to
4845 ensuring that the output goes to the remote program's device along
4846 with any other output the program might produce, you can also ask that
4847 the dprintf remain active even after disconnecting from the remote
4848 target. Using the stub/agent is also more efficient, as it can do
4849 everything without needing to communicate with @value{GDBN}.
4853 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4854 Whenever execution reaches @var{location}, print the values of one or
4855 more @var{expressions} under the control of the string @var{template}.
4856 To print several values, separate them with commas.
4858 @item set dprintf-style @var{style}
4859 Set the dprintf output to be handled in one of several different
4860 styles enumerated below. A change of style affects all existing
4861 dynamic printfs immediately. (If you need individual control over the
4862 print commands, simply define normal breakpoints with
4863 explicitly-supplied command lists.)
4866 @kindex dprintf-style gdb
4867 Handle the output using the @value{GDBN} @code{printf} command.
4870 @kindex dprintf-style call
4871 Handle the output by calling a function in your program (normally
4875 @kindex dprintf-style agent
4876 Have the remote debugging agent (such as @code{gdbserver}) handle
4877 the output itself. This style is only available for agents that
4878 support running commands on the target.
4880 @item set dprintf-function @var{function}
4881 Set the function to call if the dprintf style is @code{call}. By
4882 default its value is @code{printf}. You may set it to any expression.
4883 that @value{GDBN} can evaluate to a function, as per the @code{call}
4886 @item set dprintf-channel @var{channel}
4887 Set a ``channel'' for dprintf. If set to a non-empty value,
4888 @value{GDBN} will evaluate it as an expression and pass the result as
4889 a first argument to the @code{dprintf-function}, in the manner of
4890 @code{fprintf} and similar functions. Otherwise, the dprintf format
4891 string will be the first argument, in the manner of @code{printf}.
4893 As an example, if you wanted @code{dprintf} output to go to a logfile
4894 that is a standard I/O stream assigned to the variable @code{mylog},
4895 you could do the following:
4898 (gdb) set dprintf-style call
4899 (gdb) set dprintf-function fprintf
4900 (gdb) set dprintf-channel mylog
4901 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4902 Dprintf 1 at 0x123456: file main.c, line 25.
4904 1 dprintf keep y 0x00123456 in main at main.c:25
4905 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4910 Note that the @code{info break} displays the dynamic printf commands
4911 as normal breakpoint commands; you can thus easily see the effect of
4912 the variable settings.
4914 @item set disconnected-dprintf on
4915 @itemx set disconnected-dprintf off
4916 @kindex set disconnected-dprintf
4917 Choose whether @code{dprintf} commands should continue to run if
4918 @value{GDBN} has disconnected from the target. This only applies
4919 if the @code{dprintf-style} is @code{agent}.
4921 @item show disconnected-dprintf off
4922 @kindex show disconnected-dprintf
4923 Show the current choice for disconnected @code{dprintf}.
4927 @value{GDBN} does not check the validity of function and channel,
4928 relying on you to supply values that are meaningful for the contexts
4929 in which they are being used. For instance, the function and channel
4930 may be the values of local variables, but if that is the case, then
4931 all enabled dynamic prints must be at locations within the scope of
4932 those locals. If evaluation fails, @value{GDBN} will report an error.
4934 @node Save Breakpoints
4935 @subsection How to save breakpoints to a file
4937 To save breakpoint definitions to a file use the @w{@code{save
4938 breakpoints}} command.
4941 @kindex save breakpoints
4942 @cindex save breakpoints to a file for future sessions
4943 @item save breakpoints [@var{filename}]
4944 This command saves all current breakpoint definitions together with
4945 their commands and ignore counts, into a file @file{@var{filename}}
4946 suitable for use in a later debugging session. This includes all
4947 types of breakpoints (breakpoints, watchpoints, catchpoints,
4948 tracepoints). To read the saved breakpoint definitions, use the
4949 @code{source} command (@pxref{Command Files}). Note that watchpoints
4950 with expressions involving local variables may fail to be recreated
4951 because it may not be possible to access the context where the
4952 watchpoint is valid anymore. Because the saved breakpoint definitions
4953 are simply a sequence of @value{GDBN} commands that recreate the
4954 breakpoints, you can edit the file in your favorite editing program,
4955 and remove the breakpoint definitions you're not interested in, or
4956 that can no longer be recreated.
4959 @node Static Probe Points
4960 @subsection Static Probe Points
4962 @cindex static probe point, SystemTap
4963 @cindex static probe point, DTrace
4964 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4965 for Statically Defined Tracing, and the probes are designed to have a tiny
4966 runtime code and data footprint, and no dynamic relocations.
4968 Currently, the following types of probes are supported on
4969 ELF-compatible systems:
4973 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4974 @acronym{SDT} probes@footnote{See
4975 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4976 for more information on how to add @code{SystemTap} @acronym{SDT}
4977 probes in your applications.}. @code{SystemTap} probes are usable
4978 from assembly, C and C@t{++} languages@footnote{See
4979 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4980 for a good reference on how the @acronym{SDT} probes are implemented.}.
4982 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
4983 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
4987 @cindex semaphores on static probe points
4988 Some @code{SystemTap} probes have an associated semaphore variable;
4989 for instance, this happens automatically if you defined your probe
4990 using a DTrace-style @file{.d} file. If your probe has a semaphore,
4991 @value{GDBN} will automatically enable it when you specify a
4992 breakpoint using the @samp{-probe-stap} notation. But, if you put a
4993 breakpoint at a probe's location by some other method (e.g.,
4994 @code{break file:line}), then @value{GDBN} will not automatically set
4995 the semaphore. @code{DTrace} probes do not support semaphores.
4997 You can examine the available static static probes using @code{info
4998 probes}, with optional arguments:
5002 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5003 If given, @var{type} is either @code{stap} for listing
5004 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5005 probes. If omitted all probes are listed regardless of their types.
5007 If given, @var{provider} is a regular expression used to match against provider
5008 names when selecting which probes to list. If omitted, probes by all
5009 probes from all providers are listed.
5011 If given, @var{name} is a regular expression to match against probe names
5012 when selecting which probes to list. If omitted, probe names are not
5013 considered when deciding whether to display them.
5015 If given, @var{objfile} is a regular expression used to select which
5016 object files (executable or shared libraries) to examine. If not
5017 given, all object files are considered.
5019 @item info probes all
5020 List the available static probes, from all types.
5023 @cindex enabling and disabling probes
5024 Some probe points can be enabled and/or disabled. The effect of
5025 enabling or disabling a probe depends on the type of probe being
5026 handled. Some @code{DTrace} probes can be enabled or
5027 disabled, but @code{SystemTap} probes cannot be disabled.
5029 You can enable (or disable) one or more probes using the following
5030 commands, with optional arguments:
5033 @kindex enable probes
5034 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5035 If given, @var{provider} is a regular expression used to match against
5036 provider names when selecting which probes to enable. If omitted,
5037 all probes from all providers are enabled.
5039 If given, @var{name} is a regular expression to match against probe
5040 names when selecting which probes to enable. If omitted, probe names
5041 are not considered when deciding whether to enable them.
5043 If given, @var{objfile} is a regular expression used to select which
5044 object files (executable or shared libraries) to examine. If not
5045 given, all object files are considered.
5047 @kindex disable probes
5048 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5049 See the @code{enable probes} command above for a description of the
5050 optional arguments accepted by this command.
5053 @vindex $_probe_arg@r{, convenience variable}
5054 A probe may specify up to twelve arguments. These are available at the
5055 point at which the probe is defined---that is, when the current PC is
5056 at the probe's location. The arguments are available using the
5057 convenience variables (@pxref{Convenience Vars})
5058 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5059 probes each probe argument is an integer of the appropriate size;
5060 types are not preserved. In @code{DTrace} probes types are preserved
5061 provided that they are recognized as such by @value{GDBN}; otherwise
5062 the value of the probe argument will be a long integer. The
5063 convenience variable @code{$_probe_argc} holds the number of arguments
5064 at the current probe point.
5066 These variables are always available, but attempts to access them at
5067 any location other than a probe point will cause @value{GDBN} to give
5071 @c @ifclear BARETARGET
5072 @node Error in Breakpoints
5073 @subsection ``Cannot insert breakpoints''
5075 If you request too many active hardware-assisted breakpoints and
5076 watchpoints, you will see this error message:
5078 @c FIXME: the precise wording of this message may change; the relevant
5079 @c source change is not committed yet (Sep 3, 1999).
5081 Stopped; cannot insert breakpoints.
5082 You may have requested too many hardware breakpoints and watchpoints.
5086 This message is printed when you attempt to resume the program, since
5087 only then @value{GDBN} knows exactly how many hardware breakpoints and
5088 watchpoints it needs to insert.
5090 When this message is printed, you need to disable or remove some of the
5091 hardware-assisted breakpoints and watchpoints, and then continue.
5093 @node Breakpoint-related Warnings
5094 @subsection ``Breakpoint address adjusted...''
5095 @cindex breakpoint address adjusted
5097 Some processor architectures place constraints on the addresses at
5098 which breakpoints may be placed. For architectures thus constrained,
5099 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5100 with the constraints dictated by the architecture.
5102 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5103 a VLIW architecture in which a number of RISC-like instructions may be
5104 bundled together for parallel execution. The FR-V architecture
5105 constrains the location of a breakpoint instruction within such a
5106 bundle to the instruction with the lowest address. @value{GDBN}
5107 honors this constraint by adjusting a breakpoint's address to the
5108 first in the bundle.
5110 It is not uncommon for optimized code to have bundles which contain
5111 instructions from different source statements, thus it may happen that
5112 a breakpoint's address will be adjusted from one source statement to
5113 another. Since this adjustment may significantly alter @value{GDBN}'s
5114 breakpoint related behavior from what the user expects, a warning is
5115 printed when the breakpoint is first set and also when the breakpoint
5118 A warning like the one below is printed when setting a breakpoint
5119 that's been subject to address adjustment:
5122 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5125 Such warnings are printed both for user settable and @value{GDBN}'s
5126 internal breakpoints. If you see one of these warnings, you should
5127 verify that a breakpoint set at the adjusted address will have the
5128 desired affect. If not, the breakpoint in question may be removed and
5129 other breakpoints may be set which will have the desired behavior.
5130 E.g., it may be sufficient to place the breakpoint at a later
5131 instruction. A conditional breakpoint may also be useful in some
5132 cases to prevent the breakpoint from triggering too often.
5134 @value{GDBN} will also issue a warning when stopping at one of these
5135 adjusted breakpoints:
5138 warning: Breakpoint 1 address previously adjusted from 0x00010414
5142 When this warning is encountered, it may be too late to take remedial
5143 action except in cases where the breakpoint is hit earlier or more
5144 frequently than expected.
5146 @node Continuing and Stepping
5147 @section Continuing and Stepping
5151 @cindex resuming execution
5152 @dfn{Continuing} means resuming program execution until your program
5153 completes normally. In contrast, @dfn{stepping} means executing just
5154 one more ``step'' of your program, where ``step'' may mean either one
5155 line of source code, or one machine instruction (depending on what
5156 particular command you use). Either when continuing or when stepping,
5157 your program may stop even sooner, due to a breakpoint or a signal. (If
5158 it stops due to a signal, you may want to use @code{handle}, or use
5159 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5160 or you may step into the signal's handler (@pxref{stepping and signal
5165 @kindex c @r{(@code{continue})}
5166 @kindex fg @r{(resume foreground execution)}
5167 @item continue @r{[}@var{ignore-count}@r{]}
5168 @itemx c @r{[}@var{ignore-count}@r{]}
5169 @itemx fg @r{[}@var{ignore-count}@r{]}
5170 Resume program execution, at the address where your program last stopped;
5171 any breakpoints set at that address are bypassed. The optional argument
5172 @var{ignore-count} allows you to specify a further number of times to
5173 ignore a breakpoint at this location; its effect is like that of
5174 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5176 The argument @var{ignore-count} is meaningful only when your program
5177 stopped due to a breakpoint. At other times, the argument to
5178 @code{continue} is ignored.
5180 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5181 debugged program is deemed to be the foreground program) are provided
5182 purely for convenience, and have exactly the same behavior as
5186 To resume execution at a different place, you can use @code{return}
5187 (@pxref{Returning, ,Returning from a Function}) to go back to the
5188 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5189 Different Address}) to go to an arbitrary location in your program.
5191 A typical technique for using stepping is to set a breakpoint
5192 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5193 beginning of the function or the section of your program where a problem
5194 is believed to lie, run your program until it stops at that breakpoint,
5195 and then step through the suspect area, examining the variables that are
5196 interesting, until you see the problem happen.
5200 @kindex s @r{(@code{step})}
5202 Continue running your program until control reaches a different source
5203 line, then stop it and return control to @value{GDBN}. This command is
5204 abbreviated @code{s}.
5207 @c "without debugging information" is imprecise; actually "without line
5208 @c numbers in the debugging information". (gcc -g1 has debugging info but
5209 @c not line numbers). But it seems complex to try to make that
5210 @c distinction here.
5211 @emph{Warning:} If you use the @code{step} command while control is
5212 within a function that was compiled without debugging information,
5213 execution proceeds until control reaches a function that does have
5214 debugging information. Likewise, it will not step into a function which
5215 is compiled without debugging information. To step through functions
5216 without debugging information, use the @code{stepi} command, described
5220 The @code{step} command only stops at the first instruction of a source
5221 line. This prevents the multiple stops that could otherwise occur in
5222 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5223 to stop if a function that has debugging information is called within
5224 the line. In other words, @code{step} @emph{steps inside} any functions
5225 called within the line.
5227 Also, the @code{step} command only enters a function if there is line
5228 number information for the function. Otherwise it acts like the
5229 @code{next} command. This avoids problems when using @code{cc -gl}
5230 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5231 was any debugging information about the routine.
5233 @item step @var{count}
5234 Continue running as in @code{step}, but do so @var{count} times. If a
5235 breakpoint is reached, or a signal not related to stepping occurs before
5236 @var{count} steps, stepping stops right away.
5239 @kindex n @r{(@code{next})}
5240 @item next @r{[}@var{count}@r{]}
5241 Continue to the next source line in the current (innermost) stack frame.
5242 This is similar to @code{step}, but function calls that appear within
5243 the line of code are executed without stopping. Execution stops when
5244 control reaches a different line of code at the original stack level
5245 that was executing when you gave the @code{next} command. This command
5246 is abbreviated @code{n}.
5248 An argument @var{count} is a repeat count, as for @code{step}.
5251 @c FIX ME!! Do we delete this, or is there a way it fits in with
5252 @c the following paragraph? --- Vctoria
5254 @c @code{next} within a function that lacks debugging information acts like
5255 @c @code{step}, but any function calls appearing within the code of the
5256 @c function are executed without stopping.
5258 The @code{next} command only stops at the first instruction of a
5259 source line. This prevents multiple stops that could otherwise occur in
5260 @code{switch} statements, @code{for} loops, etc.
5262 @kindex set step-mode
5264 @cindex functions without line info, and stepping
5265 @cindex stepping into functions with no line info
5266 @itemx set step-mode on
5267 The @code{set step-mode on} command causes the @code{step} command to
5268 stop at the first instruction of a function which contains no debug line
5269 information rather than stepping over it.
5271 This is useful in cases where you may be interested in inspecting the
5272 machine instructions of a function which has no symbolic info and do not
5273 want @value{GDBN} to automatically skip over this function.
5275 @item set step-mode off
5276 Causes the @code{step} command to step over any functions which contains no
5277 debug information. This is the default.
5279 @item show step-mode
5280 Show whether @value{GDBN} will stop in or step over functions without
5281 source line debug information.
5284 @kindex fin @r{(@code{finish})}
5286 Continue running until just after function in the selected stack frame
5287 returns. Print the returned value (if any). This command can be
5288 abbreviated as @code{fin}.
5290 Contrast this with the @code{return} command (@pxref{Returning,
5291 ,Returning from a Function}).
5294 @kindex u @r{(@code{until})}
5295 @cindex run until specified location
5298 Continue running until a source line past the current line, in the
5299 current stack frame, is reached. This command is used to avoid single
5300 stepping through a loop more than once. It is like the @code{next}
5301 command, except that when @code{until} encounters a jump, it
5302 automatically continues execution until the program counter is greater
5303 than the address of the jump.
5305 This means that when you reach the end of a loop after single stepping
5306 though it, @code{until} makes your program continue execution until it
5307 exits the loop. In contrast, a @code{next} command at the end of a loop
5308 simply steps back to the beginning of the loop, which forces you to step
5309 through the next iteration.
5311 @code{until} always stops your program if it attempts to exit the current
5314 @code{until} may produce somewhat counterintuitive results if the order
5315 of machine code does not match the order of the source lines. For
5316 example, in the following excerpt from a debugging session, the @code{f}
5317 (@code{frame}) command shows that execution is stopped at line
5318 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5322 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5324 (@value{GDBP}) until
5325 195 for ( ; argc > 0; NEXTARG) @{
5328 This happened because, for execution efficiency, the compiler had
5329 generated code for the loop closure test at the end, rather than the
5330 start, of the loop---even though the test in a C @code{for}-loop is
5331 written before the body of the loop. The @code{until} command appeared
5332 to step back to the beginning of the loop when it advanced to this
5333 expression; however, it has not really gone to an earlier
5334 statement---not in terms of the actual machine code.
5336 @code{until} with no argument works by means of single
5337 instruction stepping, and hence is slower than @code{until} with an
5340 @item until @var{location}
5341 @itemx u @var{location}
5342 Continue running your program until either the specified @var{location} is
5343 reached, or the current stack frame returns. The location is any of
5344 the forms described in @ref{Specify Location}.
5345 This form of the command uses temporary breakpoints, and
5346 hence is quicker than @code{until} without an argument. The specified
5347 location is actually reached only if it is in the current frame. This
5348 implies that @code{until} can be used to skip over recursive function
5349 invocations. For instance in the code below, if the current location is
5350 line @code{96}, issuing @code{until 99} will execute the program up to
5351 line @code{99} in the same invocation of factorial, i.e., after the inner
5352 invocations have returned.
5355 94 int factorial (int value)
5357 96 if (value > 1) @{
5358 97 value *= factorial (value - 1);
5365 @kindex advance @var{location}
5366 @item advance @var{location}
5367 Continue running the program up to the given @var{location}. An argument is
5368 required, which should be of one of the forms described in
5369 @ref{Specify Location}.
5370 Execution will also stop upon exit from the current stack
5371 frame. This command is similar to @code{until}, but @code{advance} will
5372 not skip over recursive function calls, and the target location doesn't
5373 have to be in the same frame as the current one.
5377 @kindex si @r{(@code{stepi})}
5379 @itemx stepi @var{arg}
5381 Execute one machine instruction, then stop and return to the debugger.
5383 It is often useful to do @samp{display/i $pc} when stepping by machine
5384 instructions. This makes @value{GDBN} automatically display the next
5385 instruction to be executed, each time your program stops. @xref{Auto
5386 Display,, Automatic Display}.
5388 An argument is a repeat count, as in @code{step}.
5392 @kindex ni @r{(@code{nexti})}
5394 @itemx nexti @var{arg}
5396 Execute one machine instruction, but if it is a function call,
5397 proceed until the function returns.
5399 An argument is a repeat count, as in @code{next}.
5403 @anchor{range stepping}
5404 @cindex range stepping
5405 @cindex target-assisted range stepping
5406 By default, and if available, @value{GDBN} makes use of
5407 target-assisted @dfn{range stepping}. In other words, whenever you
5408 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5409 tells the target to step the corresponding range of instruction
5410 addresses instead of issuing multiple single-steps. This speeds up
5411 line stepping, particularly for remote targets. Ideally, there should
5412 be no reason you would want to turn range stepping off. However, it's
5413 possible that a bug in the debug info, a bug in the remote stub (for
5414 remote targets), or even a bug in @value{GDBN} could make line
5415 stepping behave incorrectly when target-assisted range stepping is
5416 enabled. You can use the following command to turn off range stepping
5420 @kindex set range-stepping
5421 @kindex show range-stepping
5422 @item set range-stepping
5423 @itemx show range-stepping
5424 Control whether range stepping is enabled.
5426 If @code{on}, and the target supports it, @value{GDBN} tells the
5427 target to step a range of addresses itself, instead of issuing
5428 multiple single-steps. If @code{off}, @value{GDBN} always issues
5429 single-steps, even if range stepping is supported by the target. The
5430 default is @code{on}.
5434 @node Skipping Over Functions and Files
5435 @section Skipping Over Functions and Files
5436 @cindex skipping over functions and files
5438 The program you are debugging may contain some functions which are
5439 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5440 skip a function or all functions in a file when stepping.
5442 For example, consider the following C function:
5453 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5454 are not interested in stepping through @code{boring}. If you run @code{step}
5455 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5456 step over both @code{foo} and @code{boring}!
5458 One solution is to @code{step} into @code{boring} and use the @code{finish}
5459 command to immediately exit it. But this can become tedious if @code{boring}
5460 is called from many places.
5462 A more flexible solution is to execute @kbd{skip boring}. This instructs
5463 @value{GDBN} never to step into @code{boring}. Now when you execute
5464 @code{step} at line 103, you'll step over @code{boring} and directly into
5467 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5468 example, @code{skip file boring.c}.
5471 @kindex skip function
5472 @item skip @r{[}@var{linespec}@r{]}
5473 @itemx skip function @r{[}@var{linespec}@r{]}
5474 After running this command, the function named by @var{linespec} or the
5475 function containing the line named by @var{linespec} will be skipped over when
5476 stepping. @xref{Specify Location}.
5478 If you do not specify @var{linespec}, the function you're currently debugging
5481 (If you have a function called @code{file} that you want to skip, use
5482 @kbd{skip function file}.)
5485 @item skip file @r{[}@var{filename}@r{]}
5486 After running this command, any function whose source lives in @var{filename}
5487 will be skipped over when stepping.
5489 If you do not specify @var{filename}, functions whose source lives in the file
5490 you're currently debugging will be skipped.
5493 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5494 These are the commands for managing your list of skips:
5498 @item info skip @r{[}@var{range}@r{]}
5499 Print details about the specified skip(s). If @var{range} is not specified,
5500 print a table with details about all functions and files marked for skipping.
5501 @code{info skip} prints the following information about each skip:
5505 A number identifying this skip.
5507 The type of this skip, either @samp{function} or @samp{file}.
5508 @item Enabled or Disabled
5509 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5511 For function skips, this column indicates the address in memory of the function
5512 being skipped. If you've set a function skip on a function which has not yet
5513 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5514 which has the function is loaded, @code{info skip} will show the function's
5517 For file skips, this field contains the filename being skipped. For functions
5518 skips, this field contains the function name and its line number in the file
5519 where it is defined.
5523 @item skip delete @r{[}@var{range}@r{]}
5524 Delete the specified skip(s). If @var{range} is not specified, delete all
5528 @item skip enable @r{[}@var{range}@r{]}
5529 Enable the specified skip(s). If @var{range} is not specified, enable all
5532 @kindex skip disable
5533 @item skip disable @r{[}@var{range}@r{]}
5534 Disable the specified skip(s). If @var{range} is not specified, disable all
5543 A signal is an asynchronous event that can happen in a program. The
5544 operating system defines the possible kinds of signals, and gives each
5545 kind a name and a number. For example, in Unix @code{SIGINT} is the
5546 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5547 @code{SIGSEGV} is the signal a program gets from referencing a place in
5548 memory far away from all the areas in use; @code{SIGALRM} occurs when
5549 the alarm clock timer goes off (which happens only if your program has
5550 requested an alarm).
5552 @cindex fatal signals
5553 Some signals, including @code{SIGALRM}, are a normal part of the
5554 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5555 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5556 program has not specified in advance some other way to handle the signal.
5557 @code{SIGINT} does not indicate an error in your program, but it is normally
5558 fatal so it can carry out the purpose of the interrupt: to kill the program.
5560 @value{GDBN} has the ability to detect any occurrence of a signal in your
5561 program. You can tell @value{GDBN} in advance what to do for each kind of
5564 @cindex handling signals
5565 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5566 @code{SIGALRM} be silently passed to your program
5567 (so as not to interfere with their role in the program's functioning)
5568 but to stop your program immediately whenever an error signal happens.
5569 You can change these settings with the @code{handle} command.
5572 @kindex info signals
5576 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5577 handle each one. You can use this to see the signal numbers of all
5578 the defined types of signals.
5580 @item info signals @var{sig}
5581 Similar, but print information only about the specified signal number.
5583 @code{info handle} is an alias for @code{info signals}.
5585 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5586 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5587 for details about this command.
5590 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5591 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5592 can be the number of a signal or its name (with or without the
5593 @samp{SIG} at the beginning); a list of signal numbers of the form
5594 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5595 known signals. Optional arguments @var{keywords}, described below,
5596 say what change to make.
5600 The keywords allowed by the @code{handle} command can be abbreviated.
5601 Their full names are:
5605 @value{GDBN} should not stop your program when this signal happens. It may
5606 still print a message telling you that the signal has come in.
5609 @value{GDBN} should stop your program when this signal happens. This implies
5610 the @code{print} keyword as well.
5613 @value{GDBN} should print a message when this signal happens.
5616 @value{GDBN} should not mention the occurrence of the signal at all. This
5617 implies the @code{nostop} keyword as well.
5621 @value{GDBN} should allow your program to see this signal; your program
5622 can handle the signal, or else it may terminate if the signal is fatal
5623 and not handled. @code{pass} and @code{noignore} are synonyms.
5627 @value{GDBN} should not allow your program to see this signal.
5628 @code{nopass} and @code{ignore} are synonyms.
5632 When a signal stops your program, the signal is not visible to the
5634 continue. Your program sees the signal then, if @code{pass} is in
5635 effect for the signal in question @emph{at that time}. In other words,
5636 after @value{GDBN} reports a signal, you can use the @code{handle}
5637 command with @code{pass} or @code{nopass} to control whether your
5638 program sees that signal when you continue.
5640 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5641 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5642 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5645 You can also use the @code{signal} command to prevent your program from
5646 seeing a signal, or cause it to see a signal it normally would not see,
5647 or to give it any signal at any time. For example, if your program stopped
5648 due to some sort of memory reference error, you might store correct
5649 values into the erroneous variables and continue, hoping to see more
5650 execution; but your program would probably terminate immediately as
5651 a result of the fatal signal once it saw the signal. To prevent this,
5652 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5655 @cindex stepping and signal handlers
5656 @anchor{stepping and signal handlers}
5658 @value{GDBN} optimizes for stepping the mainline code. If a signal
5659 that has @code{handle nostop} and @code{handle pass} set arrives while
5660 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5661 in progress, @value{GDBN} lets the signal handler run and then resumes
5662 stepping the mainline code once the signal handler returns. In other
5663 words, @value{GDBN} steps over the signal handler. This prevents
5664 signals that you've specified as not interesting (with @code{handle
5665 nostop}) from changing the focus of debugging unexpectedly. Note that
5666 the signal handler itself may still hit a breakpoint, stop for another
5667 signal that has @code{handle stop} in effect, or for any other event
5668 that normally results in stopping the stepping command sooner. Also
5669 note that @value{GDBN} still informs you that the program received a
5670 signal if @code{handle print} is set.
5672 @anchor{stepping into signal handlers}
5674 If you set @code{handle pass} for a signal, and your program sets up a
5675 handler for it, then issuing a stepping command, such as @code{step}
5676 or @code{stepi}, when your program is stopped due to the signal will
5677 step @emph{into} the signal handler (if the target supports that).
5679 Likewise, if you use the @code{queue-signal} command to queue a signal
5680 to be delivered to the current thread when execution of the thread
5681 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5682 stepping command will step into the signal handler.
5684 Here's an example, using @code{stepi} to step to the first instruction
5685 of @code{SIGUSR1}'s handler:
5688 (@value{GDBP}) handle SIGUSR1
5689 Signal Stop Print Pass to program Description
5690 SIGUSR1 Yes Yes Yes User defined signal 1
5694 Program received signal SIGUSR1, User defined signal 1.
5695 main () sigusr1.c:28
5698 sigusr1_handler () at sigusr1.c:9
5702 The same, but using @code{queue-signal} instead of waiting for the
5703 program to receive the signal first:
5708 (@value{GDBP}) queue-signal SIGUSR1
5710 sigusr1_handler () at sigusr1.c:9
5715 @cindex extra signal information
5716 @anchor{extra signal information}
5718 On some targets, @value{GDBN} can inspect extra signal information
5719 associated with the intercepted signal, before it is actually
5720 delivered to the program being debugged. This information is exported
5721 by the convenience variable @code{$_siginfo}, and consists of data
5722 that is passed by the kernel to the signal handler at the time of the
5723 receipt of a signal. The data type of the information itself is
5724 target dependent. You can see the data type using the @code{ptype
5725 $_siginfo} command. On Unix systems, it typically corresponds to the
5726 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5729 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5730 referenced address that raised a segmentation fault.
5734 (@value{GDBP}) continue
5735 Program received signal SIGSEGV, Segmentation fault.
5736 0x0000000000400766 in main ()
5738 (@value{GDBP}) ptype $_siginfo
5745 struct @{...@} _kill;
5746 struct @{...@} _timer;
5748 struct @{...@} _sigchld;
5749 struct @{...@} _sigfault;
5750 struct @{...@} _sigpoll;
5753 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5757 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5758 $1 = (void *) 0x7ffff7ff7000
5762 Depending on target support, @code{$_siginfo} may also be writable.
5765 @section Stopping and Starting Multi-thread Programs
5767 @cindex stopped threads
5768 @cindex threads, stopped
5770 @cindex continuing threads
5771 @cindex threads, continuing
5773 @value{GDBN} supports debugging programs with multiple threads
5774 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5775 are two modes of controlling execution of your program within the
5776 debugger. In the default mode, referred to as @dfn{all-stop mode},
5777 when any thread in your program stops (for example, at a breakpoint
5778 or while being stepped), all other threads in the program are also stopped by
5779 @value{GDBN}. On some targets, @value{GDBN} also supports
5780 @dfn{non-stop mode}, in which other threads can continue to run freely while
5781 you examine the stopped thread in the debugger.
5784 * All-Stop Mode:: All threads stop when GDB takes control
5785 * Non-Stop Mode:: Other threads continue to execute
5786 * Background Execution:: Running your program asynchronously
5787 * Thread-Specific Breakpoints:: Controlling breakpoints
5788 * Interrupted System Calls:: GDB may interfere with system calls
5789 * Observer Mode:: GDB does not alter program behavior
5793 @subsection All-Stop Mode
5795 @cindex all-stop mode
5797 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5798 @emph{all} threads of execution stop, not just the current thread. This
5799 allows you to examine the overall state of the program, including
5800 switching between threads, without worrying that things may change
5803 Conversely, whenever you restart the program, @emph{all} threads start
5804 executing. @emph{This is true even when single-stepping} with commands
5805 like @code{step} or @code{next}.
5807 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5808 Since thread scheduling is up to your debugging target's operating
5809 system (not controlled by @value{GDBN}), other threads may
5810 execute more than one statement while the current thread completes a
5811 single step. Moreover, in general other threads stop in the middle of a
5812 statement, rather than at a clean statement boundary, when the program
5815 You might even find your program stopped in another thread after
5816 continuing or even single-stepping. This happens whenever some other
5817 thread runs into a breakpoint, a signal, or an exception before the
5818 first thread completes whatever you requested.
5820 @cindex automatic thread selection
5821 @cindex switching threads automatically
5822 @cindex threads, automatic switching
5823 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5824 signal, it automatically selects the thread where that breakpoint or
5825 signal happened. @value{GDBN} alerts you to the context switch with a
5826 message such as @samp{[Switching to Thread @var{n}]} to identify the
5829 On some OSes, you can modify @value{GDBN}'s default behavior by
5830 locking the OS scheduler to allow only a single thread to run.
5833 @item set scheduler-locking @var{mode}
5834 @cindex scheduler locking mode
5835 @cindex lock scheduler
5836 Set the scheduler locking mode. If it is @code{off}, then there is no
5837 locking and any thread may run at any time. If @code{on}, then only the
5838 current thread may run when the inferior is resumed. The @code{step}
5839 mode optimizes for single-stepping; it prevents other threads
5840 from preempting the current thread while you are stepping, so that
5841 the focus of debugging does not change unexpectedly.
5842 Other threads never get a chance to run when you step, and they are
5843 completely free to run when you use commands
5844 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5845 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5846 the current thread away from the thread that you are debugging.
5848 @item show scheduler-locking
5849 Display the current scheduler locking mode.
5852 @cindex resume threads of multiple processes simultaneously
5853 By default, when you issue one of the execution commands such as
5854 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5855 threads of the current inferior to run. For example, if @value{GDBN}
5856 is attached to two inferiors, each with two threads, the
5857 @code{continue} command resumes only the two threads of the current
5858 inferior. This is useful, for example, when you debug a program that
5859 forks and you want to hold the parent stopped (so that, for instance,
5860 it doesn't run to exit), while you debug the child. In other
5861 situations, you may not be interested in inspecting the current state
5862 of any of the processes @value{GDBN} is attached to, and you may want
5863 to resume them all until some breakpoint is hit. In the latter case,
5864 you can instruct @value{GDBN} to allow all threads of all the
5865 inferiors to run with the @w{@code{set schedule-multiple}} command.
5868 @kindex set schedule-multiple
5869 @item set schedule-multiple
5870 Set the mode for allowing threads of multiple processes to be resumed
5871 when an execution command is issued. When @code{on}, all threads of
5872 all processes are allowed to run. When @code{off}, only the threads
5873 of the current process are resumed. The default is @code{off}. The
5874 @code{scheduler-locking} mode takes precedence when set to @code{on},
5875 or while you are stepping and set to @code{step}.
5877 @item show schedule-multiple
5878 Display the current mode for resuming the execution of threads of
5883 @subsection Non-Stop Mode
5885 @cindex non-stop mode
5887 @c This section is really only a place-holder, and needs to be expanded
5888 @c with more details.
5890 For some multi-threaded targets, @value{GDBN} supports an optional
5891 mode of operation in which you can examine stopped program threads in
5892 the debugger while other threads continue to execute freely. This
5893 minimizes intrusion when debugging live systems, such as programs
5894 where some threads have real-time constraints or must continue to
5895 respond to external events. This is referred to as @dfn{non-stop} mode.
5897 In non-stop mode, when a thread stops to report a debugging event,
5898 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5899 threads as well, in contrast to the all-stop mode behavior. Additionally,
5900 execution commands such as @code{continue} and @code{step} apply by default
5901 only to the current thread in non-stop mode, rather than all threads as
5902 in all-stop mode. This allows you to control threads explicitly in
5903 ways that are not possible in all-stop mode --- for example, stepping
5904 one thread while allowing others to run freely, stepping
5905 one thread while holding all others stopped, or stepping several threads
5906 independently and simultaneously.
5908 To enter non-stop mode, use this sequence of commands before you run
5909 or attach to your program:
5912 # If using the CLI, pagination breaks non-stop.
5915 # Finally, turn it on!
5919 You can use these commands to manipulate the non-stop mode setting:
5922 @kindex set non-stop
5923 @item set non-stop on
5924 Enable selection of non-stop mode.
5925 @item set non-stop off
5926 Disable selection of non-stop mode.
5927 @kindex show non-stop
5929 Show the current non-stop enablement setting.
5932 Note these commands only reflect whether non-stop mode is enabled,
5933 not whether the currently-executing program is being run in non-stop mode.
5934 In particular, the @code{set non-stop} preference is only consulted when
5935 @value{GDBN} starts or connects to the target program, and it is generally
5936 not possible to switch modes once debugging has started. Furthermore,
5937 since not all targets support non-stop mode, even when you have enabled
5938 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5941 In non-stop mode, all execution commands apply only to the current thread
5942 by default. That is, @code{continue} only continues one thread.
5943 To continue all threads, issue @code{continue -a} or @code{c -a}.
5945 You can use @value{GDBN}'s background execution commands
5946 (@pxref{Background Execution}) to run some threads in the background
5947 while you continue to examine or step others from @value{GDBN}.
5948 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5949 always executed asynchronously in non-stop mode.
5951 Suspending execution is done with the @code{interrupt} command when
5952 running in the background, or @kbd{Ctrl-c} during foreground execution.
5953 In all-stop mode, this stops the whole process;
5954 but in non-stop mode the interrupt applies only to the current thread.
5955 To stop the whole program, use @code{interrupt -a}.
5957 Other execution commands do not currently support the @code{-a} option.
5959 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5960 that thread current, as it does in all-stop mode. This is because the
5961 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5962 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5963 changed to a different thread just as you entered a command to operate on the
5964 previously current thread.
5966 @node Background Execution
5967 @subsection Background Execution
5969 @cindex foreground execution
5970 @cindex background execution
5971 @cindex asynchronous execution
5972 @cindex execution, foreground, background and asynchronous
5974 @value{GDBN}'s execution commands have two variants: the normal
5975 foreground (synchronous) behavior, and a background
5976 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5977 the program to report that some thread has stopped before prompting for
5978 another command. In background execution, @value{GDBN} immediately gives
5979 a command prompt so that you can issue other commands while your program runs.
5981 If the target doesn't support async mode, @value{GDBN} issues an error
5982 message if you attempt to use the background execution commands.
5984 To specify background execution, add a @code{&} to the command. For example,
5985 the background form of the @code{continue} command is @code{continue&}, or
5986 just @code{c&}. The execution commands that accept background execution
5992 @xref{Starting, , Starting your Program}.
5996 @xref{Attach, , Debugging an Already-running Process}.
6000 @xref{Continuing and Stepping, step}.
6004 @xref{Continuing and Stepping, stepi}.
6008 @xref{Continuing and Stepping, next}.
6012 @xref{Continuing and Stepping, nexti}.
6016 @xref{Continuing and Stepping, continue}.
6020 @xref{Continuing and Stepping, finish}.
6024 @xref{Continuing and Stepping, until}.
6028 Background execution is especially useful in conjunction with non-stop
6029 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6030 However, you can also use these commands in the normal all-stop mode with
6031 the restriction that you cannot issue another execution command until the
6032 previous one finishes. Examples of commands that are valid in all-stop
6033 mode while the program is running include @code{help} and @code{info break}.
6035 You can interrupt your program while it is running in the background by
6036 using the @code{interrupt} command.
6043 Suspend execution of the running program. In all-stop mode,
6044 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6045 only the current thread. To stop the whole program in non-stop mode,
6046 use @code{interrupt -a}.
6049 @node Thread-Specific Breakpoints
6050 @subsection Thread-Specific Breakpoints
6052 When your program has multiple threads (@pxref{Threads,, Debugging
6053 Programs with Multiple Threads}), you can choose whether to set
6054 breakpoints on all threads, or on a particular thread.
6057 @cindex breakpoints and threads
6058 @cindex thread breakpoints
6059 @kindex break @dots{} thread @var{threadno}
6060 @item break @var{linespec} thread @var{threadno}
6061 @itemx break @var{linespec} thread @var{threadno} if @dots{}
6062 @var{linespec} specifies source lines; there are several ways of
6063 writing them (@pxref{Specify Location}), but the effect is always to
6064 specify some source line.
6066 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
6067 to specify that you only want @value{GDBN} to stop the program when a
6068 particular thread reaches this breakpoint. The @var{threadno} specifier
6069 is one of the numeric thread identifiers assigned by @value{GDBN}, shown
6070 in the first column of the @samp{info threads} display.
6072 If you do not specify @samp{thread @var{threadno}} when you set a
6073 breakpoint, the breakpoint applies to @emph{all} threads of your
6076 You can use the @code{thread} qualifier on conditional breakpoints as
6077 well; in this case, place @samp{thread @var{threadno}} before or
6078 after the breakpoint condition, like this:
6081 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6086 Thread-specific breakpoints are automatically deleted when
6087 @value{GDBN} detects the corresponding thread is no longer in the
6088 thread list. For example:
6092 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6095 There are several ways for a thread to disappear, such as a regular
6096 thread exit, but also when you detach from the process with the
6097 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6098 Process}), or if @value{GDBN} loses the remote connection
6099 (@pxref{Remote Debugging}), etc. Note that with some targets,
6100 @value{GDBN} is only able to detect a thread has exited when the user
6101 explictly asks for the thread list with the @code{info threads}
6104 @node Interrupted System Calls
6105 @subsection Interrupted System Calls
6107 @cindex thread breakpoints and system calls
6108 @cindex system calls and thread breakpoints
6109 @cindex premature return from system calls
6110 There is an unfortunate side effect when using @value{GDBN} to debug
6111 multi-threaded programs. If one thread stops for a
6112 breakpoint, or for some other reason, and another thread is blocked in a
6113 system call, then the system call may return prematurely. This is a
6114 consequence of the interaction between multiple threads and the signals
6115 that @value{GDBN} uses to implement breakpoints and other events that
6118 To handle this problem, your program should check the return value of
6119 each system call and react appropriately. This is good programming
6122 For example, do not write code like this:
6128 The call to @code{sleep} will return early if a different thread stops
6129 at a breakpoint or for some other reason.
6131 Instead, write this:
6136 unslept = sleep (unslept);
6139 A system call is allowed to return early, so the system is still
6140 conforming to its specification. But @value{GDBN} does cause your
6141 multi-threaded program to behave differently than it would without
6144 Also, @value{GDBN} uses internal breakpoints in the thread library to
6145 monitor certain events such as thread creation and thread destruction.
6146 When such an event happens, a system call in another thread may return
6147 prematurely, even though your program does not appear to stop.
6150 @subsection Observer Mode
6152 If you want to build on non-stop mode and observe program behavior
6153 without any chance of disruption by @value{GDBN}, you can set
6154 variables to disable all of the debugger's attempts to modify state,
6155 whether by writing memory, inserting breakpoints, etc. These operate
6156 at a low level, intercepting operations from all commands.
6158 When all of these are set to @code{off}, then @value{GDBN} is said to
6159 be @dfn{observer mode}. As a convenience, the variable
6160 @code{observer} can be set to disable these, plus enable non-stop
6163 Note that @value{GDBN} will not prevent you from making nonsensical
6164 combinations of these settings. For instance, if you have enabled
6165 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6166 then breakpoints that work by writing trap instructions into the code
6167 stream will still not be able to be placed.
6172 @item set observer on
6173 @itemx set observer off
6174 When set to @code{on}, this disables all the permission variables
6175 below (except for @code{insert-fast-tracepoints}), plus enables
6176 non-stop debugging. Setting this to @code{off} switches back to
6177 normal debugging, though remaining in non-stop mode.
6180 Show whether observer mode is on or off.
6182 @kindex may-write-registers
6183 @item set may-write-registers on
6184 @itemx set may-write-registers off
6185 This controls whether @value{GDBN} will attempt to alter the values of
6186 registers, such as with assignment expressions in @code{print}, or the
6187 @code{jump} command. It defaults to @code{on}.
6189 @item show may-write-registers
6190 Show the current permission to write registers.
6192 @kindex may-write-memory
6193 @item set may-write-memory on
6194 @itemx set may-write-memory off
6195 This controls whether @value{GDBN} will attempt to alter the contents
6196 of memory, such as with assignment expressions in @code{print}. It
6197 defaults to @code{on}.
6199 @item show may-write-memory
6200 Show the current permission to write memory.
6202 @kindex may-insert-breakpoints
6203 @item set may-insert-breakpoints on
6204 @itemx set may-insert-breakpoints off
6205 This controls whether @value{GDBN} will attempt to insert breakpoints.
6206 This affects all breakpoints, including internal breakpoints defined
6207 by @value{GDBN}. It defaults to @code{on}.
6209 @item show may-insert-breakpoints
6210 Show the current permission to insert breakpoints.
6212 @kindex may-insert-tracepoints
6213 @item set may-insert-tracepoints on
6214 @itemx set may-insert-tracepoints off
6215 This controls whether @value{GDBN} will attempt to insert (regular)
6216 tracepoints at the beginning of a tracing experiment. It affects only
6217 non-fast tracepoints, fast tracepoints being under the control of
6218 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6220 @item show may-insert-tracepoints
6221 Show the current permission to insert tracepoints.
6223 @kindex may-insert-fast-tracepoints
6224 @item set may-insert-fast-tracepoints on
6225 @itemx set may-insert-fast-tracepoints off
6226 This controls whether @value{GDBN} will attempt to insert fast
6227 tracepoints at the beginning of a tracing experiment. It affects only
6228 fast tracepoints, regular (non-fast) tracepoints being under the
6229 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6231 @item show may-insert-fast-tracepoints
6232 Show the current permission to insert fast tracepoints.
6234 @kindex may-interrupt
6235 @item set may-interrupt on
6236 @itemx set may-interrupt off
6237 This controls whether @value{GDBN} will attempt to interrupt or stop
6238 program execution. When this variable is @code{off}, the
6239 @code{interrupt} command will have no effect, nor will
6240 @kbd{Ctrl-c}. It defaults to @code{on}.
6242 @item show may-interrupt
6243 Show the current permission to interrupt or stop the program.
6247 @node Reverse Execution
6248 @chapter Running programs backward
6249 @cindex reverse execution
6250 @cindex running programs backward
6252 When you are debugging a program, it is not unusual to realize that
6253 you have gone too far, and some event of interest has already happened.
6254 If the target environment supports it, @value{GDBN} can allow you to
6255 ``rewind'' the program by running it backward.
6257 A target environment that supports reverse execution should be able
6258 to ``undo'' the changes in machine state that have taken place as the
6259 program was executing normally. Variables, registers etc.@: should
6260 revert to their previous values. Obviously this requires a great
6261 deal of sophistication on the part of the target environment; not
6262 all target environments can support reverse execution.
6264 When a program is executed in reverse, the instructions that
6265 have most recently been executed are ``un-executed'', in reverse
6266 order. The program counter runs backward, following the previous
6267 thread of execution in reverse. As each instruction is ``un-executed'',
6268 the values of memory and/or registers that were changed by that
6269 instruction are reverted to their previous states. After executing
6270 a piece of source code in reverse, all side effects of that code
6271 should be ``undone'', and all variables should be returned to their
6272 prior values@footnote{
6273 Note that some side effects are easier to undo than others. For instance,
6274 memory and registers are relatively easy, but device I/O is hard. Some
6275 targets may be able undo things like device I/O, and some may not.
6277 The contract between @value{GDBN} and the reverse executing target
6278 requires only that the target do something reasonable when
6279 @value{GDBN} tells it to execute backwards, and then report the
6280 results back to @value{GDBN}. Whatever the target reports back to
6281 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6282 assumes that the memory and registers that the target reports are in a
6283 consistant state, but @value{GDBN} accepts whatever it is given.
6286 If you are debugging in a target environment that supports
6287 reverse execution, @value{GDBN} provides the following commands.
6290 @kindex reverse-continue
6291 @kindex rc @r{(@code{reverse-continue})}
6292 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6293 @itemx rc @r{[}@var{ignore-count}@r{]}
6294 Beginning at the point where your program last stopped, start executing
6295 in reverse. Reverse execution will stop for breakpoints and synchronous
6296 exceptions (signals), just like normal execution. Behavior of
6297 asynchronous signals depends on the target environment.
6299 @kindex reverse-step
6300 @kindex rs @r{(@code{step})}
6301 @item reverse-step @r{[}@var{count}@r{]}
6302 Run the program backward until control reaches the start of a
6303 different source line; then stop it, and return control to @value{GDBN}.
6305 Like the @code{step} command, @code{reverse-step} will only stop
6306 at the beginning of a source line. It ``un-executes'' the previously
6307 executed source line. If the previous source line included calls to
6308 debuggable functions, @code{reverse-step} will step (backward) into
6309 the called function, stopping at the beginning of the @emph{last}
6310 statement in the called function (typically a return statement).
6312 Also, as with the @code{step} command, if non-debuggable functions are
6313 called, @code{reverse-step} will run thru them backward without stopping.
6315 @kindex reverse-stepi
6316 @kindex rsi @r{(@code{reverse-stepi})}
6317 @item reverse-stepi @r{[}@var{count}@r{]}
6318 Reverse-execute one machine instruction. Note that the instruction
6319 to be reverse-executed is @emph{not} the one pointed to by the program
6320 counter, but the instruction executed prior to that one. For instance,
6321 if the last instruction was a jump, @code{reverse-stepi} will take you
6322 back from the destination of the jump to the jump instruction itself.
6324 @kindex reverse-next
6325 @kindex rn @r{(@code{reverse-next})}
6326 @item reverse-next @r{[}@var{count}@r{]}
6327 Run backward to the beginning of the previous line executed in
6328 the current (innermost) stack frame. If the line contains function
6329 calls, they will be ``un-executed'' without stopping. Starting from
6330 the first line of a function, @code{reverse-next} will take you back
6331 to the caller of that function, @emph{before} the function was called,
6332 just as the normal @code{next} command would take you from the last
6333 line of a function back to its return to its caller
6334 @footnote{Unless the code is too heavily optimized.}.
6336 @kindex reverse-nexti
6337 @kindex rni @r{(@code{reverse-nexti})}
6338 @item reverse-nexti @r{[}@var{count}@r{]}
6339 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6340 in reverse, except that called functions are ``un-executed'' atomically.
6341 That is, if the previously executed instruction was a return from
6342 another function, @code{reverse-nexti} will continue to execute
6343 in reverse until the call to that function (from the current stack
6346 @kindex reverse-finish
6347 @item reverse-finish
6348 Just as the @code{finish} command takes you to the point where the
6349 current function returns, @code{reverse-finish} takes you to the point
6350 where it was called. Instead of ending up at the end of the current
6351 function invocation, you end up at the beginning.
6353 @kindex set exec-direction
6354 @item set exec-direction
6355 Set the direction of target execution.
6356 @item set exec-direction reverse
6357 @cindex execute forward or backward in time
6358 @value{GDBN} will perform all execution commands in reverse, until the
6359 exec-direction mode is changed to ``forward''. Affected commands include
6360 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6361 command cannot be used in reverse mode.
6362 @item set exec-direction forward
6363 @value{GDBN} will perform all execution commands in the normal fashion.
6364 This is the default.
6368 @node Process Record and Replay
6369 @chapter Recording Inferior's Execution and Replaying It
6370 @cindex process record and replay
6371 @cindex recording inferior's execution and replaying it
6373 On some platforms, @value{GDBN} provides a special @dfn{process record
6374 and replay} target that can record a log of the process execution, and
6375 replay it later with both forward and reverse execution commands.
6378 When this target is in use, if the execution log includes the record
6379 for the next instruction, @value{GDBN} will debug in @dfn{replay
6380 mode}. In the replay mode, the inferior does not really execute code
6381 instructions. Instead, all the events that normally happen during
6382 code execution are taken from the execution log. While code is not
6383 really executed in replay mode, the values of registers (including the
6384 program counter register) and the memory of the inferior are still
6385 changed as they normally would. Their contents are taken from the
6389 If the record for the next instruction is not in the execution log,
6390 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6391 inferior executes normally, and @value{GDBN} records the execution log
6394 The process record and replay target supports reverse execution
6395 (@pxref{Reverse Execution}), even if the platform on which the
6396 inferior runs does not. However, the reverse execution is limited in
6397 this case by the range of the instructions recorded in the execution
6398 log. In other words, reverse execution on platforms that don't
6399 support it directly can only be done in the replay mode.
6401 When debugging in the reverse direction, @value{GDBN} will work in
6402 replay mode as long as the execution log includes the record for the
6403 previous instruction; otherwise, it will work in record mode, if the
6404 platform supports reverse execution, or stop if not.
6406 For architecture environments that support process record and replay,
6407 @value{GDBN} provides the following commands:
6410 @kindex target record
6411 @kindex target record-full
6412 @kindex target record-btrace
6415 @kindex record btrace
6416 @kindex record btrace bts
6421 @kindex rec btrace bts
6423 @item record @var{method}
6424 This command starts the process record and replay target. The
6425 recording method can be specified as parameter. Without a parameter
6426 the command uses the @code{full} recording method. The following
6427 recording methods are available:
6431 Full record/replay recording using @value{GDBN}'s software record and
6432 replay implementation. This method allows replaying and reverse
6435 @item btrace @var{format}
6436 Hardware-supported instruction recording. This method does not record
6437 data. Further, the data is collected in a ring buffer so old data will
6438 be overwritten when the buffer is full. It allows limited replay and
6441 The recording format can be specified as parameter. Without a parameter
6442 the command chooses the recording format. The following recording
6443 formats are available:
6447 @cindex branch trace store
6448 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6449 this format, the processor stores a from/to record for each executed
6450 branch in the btrace ring buffer.
6453 Not all recording formats may be available on all processors.
6456 The process record and replay target can only debug a process that is
6457 already running. Therefore, you need first to start the process with
6458 the @kbd{run} or @kbd{start} commands, and then start the recording
6459 with the @kbd{record @var{method}} command.
6461 Both @code{record @var{method}} and @code{rec @var{method}} are
6462 aliases of @code{target record-@var{method}}.
6464 @cindex displaced stepping, and process record and replay
6465 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6466 will be automatically disabled when process record and replay target
6467 is started. That's because the process record and replay target
6468 doesn't support displaced stepping.
6470 @cindex non-stop mode, and process record and replay
6471 @cindex asynchronous execution, and process record and replay
6472 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6473 the asynchronous execution mode (@pxref{Background Execution}), not
6474 all recording methods are available. The @code{full} recording method
6475 does not support these two modes.
6480 Stop the process record and replay target. When process record and
6481 replay target stops, the entire execution log will be deleted and the
6482 inferior will either be terminated, or will remain in its final state.
6484 When you stop the process record and replay target in record mode (at
6485 the end of the execution log), the inferior will be stopped at the
6486 next instruction that would have been recorded. In other words, if
6487 you record for a while and then stop recording, the inferior process
6488 will be left in the same state as if the recording never happened.
6490 On the other hand, if the process record and replay target is stopped
6491 while in replay mode (that is, not at the end of the execution log,
6492 but at some earlier point), the inferior process will become ``live''
6493 at that earlier state, and it will then be possible to continue the
6494 usual ``live'' debugging of the process from that state.
6496 When the inferior process exits, or @value{GDBN} detaches from it,
6497 process record and replay target will automatically stop itself.
6501 Go to a specific location in the execution log. There are several
6502 ways to specify the location to go to:
6505 @item record goto begin
6506 @itemx record goto start
6507 Go to the beginning of the execution log.
6509 @item record goto end
6510 Go to the end of the execution log.
6512 @item record goto @var{n}
6513 Go to instruction number @var{n} in the execution log.
6517 @item record save @var{filename}
6518 Save the execution log to a file @file{@var{filename}}.
6519 Default filename is @file{gdb_record.@var{process_id}}, where
6520 @var{process_id} is the process ID of the inferior.
6522 This command may not be available for all recording methods.
6524 @kindex record restore
6525 @item record restore @var{filename}
6526 Restore the execution log from a file @file{@var{filename}}.
6527 File must have been created with @code{record save}.
6529 @kindex set record full
6530 @item set record full insn-number-max @var{limit}
6531 @itemx set record full insn-number-max unlimited
6532 Set the limit of instructions to be recorded for the @code{full}
6533 recording method. Default value is 200000.
6535 If @var{limit} is a positive number, then @value{GDBN} will start
6536 deleting instructions from the log once the number of the record
6537 instructions becomes greater than @var{limit}. For every new recorded
6538 instruction, @value{GDBN} will delete the earliest recorded
6539 instruction to keep the number of recorded instructions at the limit.
6540 (Since deleting recorded instructions loses information, @value{GDBN}
6541 lets you control what happens when the limit is reached, by means of
6542 the @code{stop-at-limit} option, described below.)
6544 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6545 delete recorded instructions from the execution log. The number of
6546 recorded instructions is limited only by the available memory.
6548 @kindex show record full
6549 @item show record full insn-number-max
6550 Show the limit of instructions to be recorded with the @code{full}
6553 @item set record full stop-at-limit
6554 Control the behavior of the @code{full} recording method when the
6555 number of recorded instructions reaches the limit. If ON (the
6556 default), @value{GDBN} will stop when the limit is reached for the
6557 first time and ask you whether you want to stop the inferior or
6558 continue running it and recording the execution log. If you decide
6559 to continue recording, each new recorded instruction will cause the
6560 oldest one to be deleted.
6562 If this option is OFF, @value{GDBN} will automatically delete the
6563 oldest record to make room for each new one, without asking.
6565 @item show record full stop-at-limit
6566 Show the current setting of @code{stop-at-limit}.
6568 @item set record full memory-query
6569 Control the behavior when @value{GDBN} is unable to record memory
6570 changes caused by an instruction for the @code{full} recording method.
6571 If ON, @value{GDBN} will query whether to stop the inferior in that
6574 If this option is OFF (the default), @value{GDBN} will automatically
6575 ignore the effect of such instructions on memory. Later, when
6576 @value{GDBN} replays this execution log, it will mark the log of this
6577 instruction as not accessible, and it will not affect the replay
6580 @item show record full memory-query
6581 Show the current setting of @code{memory-query}.
6583 @kindex set record btrace
6584 The @code{btrace} record target does not trace data. As a
6585 convenience, when replaying, @value{GDBN} reads read-only memory off
6586 the live program directly, assuming that the addresses of the
6587 read-only areas don't change. This for example makes it possible to
6588 disassemble code while replaying, but not to print variables.
6589 In some cases, being able to inspect variables might be useful.
6590 You can use the following command for that:
6592 @item set record btrace replay-memory-access
6593 Control the behavior of the @code{btrace} recording method when
6594 accessing memory during replay. If @code{read-only} (the default),
6595 @value{GDBN} will only allow accesses to read-only memory.
6596 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6597 and to read-write memory. Beware that the accessed memory corresponds
6598 to the live target and not necessarily to the current replay
6601 @kindex show record btrace
6602 @item show record btrace replay-memory-access
6603 Show the current setting of @code{replay-memory-access}.
6605 @kindex set record btrace bts
6606 @item set record btrace bts buffer-size @var{size}
6607 @itemx set record btrace bts buffer-size unlimited
6608 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6609 format. Default is 64KB.
6611 If @var{size} is a positive number, then @value{GDBN} will try to
6612 allocate a buffer of at least @var{size} bytes for each new thread
6613 that uses the btrace recording method and the @acronym{BTS} format.
6614 The actually obtained buffer size may differ from the requested
6615 @var{size}. Use the @code{info record} command to see the actual
6616 buffer size for each thread that uses the btrace recording method and
6617 the @acronym{BTS} format.
6619 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6620 allocate a buffer of 4MB.
6622 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6623 also need longer to process the branch trace data before it can be used.
6625 @item show record btrace bts buffer-size @var{size}
6626 Show the current setting of the requested ring buffer size for branch
6627 tracing in @acronym{BTS} format.
6631 Show various statistics about the recording depending on the recording
6636 For the @code{full} recording method, it shows the state of process
6637 record and its in-memory execution log buffer, including:
6641 Whether in record mode or replay mode.
6643 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6645 Highest recorded instruction number.
6647 Current instruction about to be replayed (if in replay mode).
6649 Number of instructions contained in the execution log.
6651 Maximum number of instructions that may be contained in the execution log.
6655 For the @code{btrace} recording method, it shows:
6661 Number of instructions that have been recorded.
6663 Number of blocks of sequential control-flow formed by the recorded
6666 Whether in record mode or replay mode.
6669 For the @code{bts} recording format, it also shows:
6672 Size of the perf ring buffer.
6676 @kindex record delete
6679 When record target runs in replay mode (``in the past''), delete the
6680 subsequent execution log and begin to record a new execution log starting
6681 from the current address. This means you will abandon the previously
6682 recorded ``future'' and begin recording a new ``future''.
6684 @kindex record instruction-history
6685 @kindex rec instruction-history
6686 @item record instruction-history
6687 Disassembles instructions from the recorded execution log. By
6688 default, ten instructions are disassembled. This can be changed using
6689 the @code{set record instruction-history-size} command. Instructions
6690 are printed in execution order. There are several ways to specify
6691 what part of the execution log to disassemble:
6694 @item record instruction-history @var{insn}
6695 Disassembles ten instructions starting from instruction number
6698 @item record instruction-history @var{insn}, +/-@var{n}
6699 Disassembles @var{n} instructions around instruction number
6700 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6701 @var{n} instructions after instruction number @var{insn}. If
6702 @var{n} is preceded with @code{-}, disassembles @var{n}
6703 instructions before instruction number @var{insn}.
6705 @item record instruction-history
6706 Disassembles ten more instructions after the last disassembly.
6708 @item record instruction-history -
6709 Disassembles ten more instructions before the last disassembly.
6711 @item record instruction-history @var{begin} @var{end}
6712 Disassembles instructions beginning with instruction number
6713 @var{begin} until instruction number @var{end}. The instruction
6714 number @var{end} is included.
6717 This command may not be available for all recording methods.
6720 @item set record instruction-history-size @var{size}
6721 @itemx set record instruction-history-size unlimited
6722 Define how many instructions to disassemble in the @code{record
6723 instruction-history} command. The default value is 10.
6724 A @var{size} of @code{unlimited} means unlimited instructions.
6727 @item show record instruction-history-size
6728 Show how many instructions to disassemble in the @code{record
6729 instruction-history} command.
6731 @kindex record function-call-history
6732 @kindex rec function-call-history
6733 @item record function-call-history
6734 Prints the execution history at function granularity. It prints one
6735 line for each sequence of instructions that belong to the same
6736 function giving the name of that function, the source lines
6737 for this instruction sequence (if the @code{/l} modifier is
6738 specified), and the instructions numbers that form the sequence (if
6739 the @code{/i} modifier is specified). The function names are indented
6740 to reflect the call stack depth if the @code{/c} modifier is
6741 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6745 (@value{GDBP}) @b{list 1, 10}
6756 (@value{GDBP}) @b{record function-call-history /ilc}
6757 1 bar inst 1,4 at foo.c:6,8
6758 2 foo inst 5,10 at foo.c:2,3
6759 3 bar inst 11,13 at foo.c:9,10
6762 By default, ten lines are printed. This can be changed using the
6763 @code{set record function-call-history-size} command. Functions are
6764 printed in execution order. There are several ways to specify what
6768 @item record function-call-history @var{func}
6769 Prints ten functions starting from function number @var{func}.
6771 @item record function-call-history @var{func}, +/-@var{n}
6772 Prints @var{n} functions around function number @var{func}. If
6773 @var{n} is preceded with @code{+}, prints @var{n} functions after
6774 function number @var{func}. If @var{n} is preceded with @code{-},
6775 prints @var{n} functions before function number @var{func}.
6777 @item record function-call-history
6778 Prints ten more functions after the last ten-line print.
6780 @item record function-call-history -
6781 Prints ten more functions before the last ten-line print.
6783 @item record function-call-history @var{begin} @var{end}
6784 Prints functions beginning with function number @var{begin} until
6785 function number @var{end}. The function number @var{end} is included.
6788 This command may not be available for all recording methods.
6790 @item set record function-call-history-size @var{size}
6791 @itemx set record function-call-history-size unlimited
6792 Define how many lines to print in the
6793 @code{record function-call-history} command. The default value is 10.
6794 A size of @code{unlimited} means unlimited lines.
6796 @item show record function-call-history-size
6797 Show how many lines to print in the
6798 @code{record function-call-history} command.
6803 @chapter Examining the Stack
6805 When your program has stopped, the first thing you need to know is where it
6806 stopped and how it got there.
6809 Each time your program performs a function call, information about the call
6811 That information includes the location of the call in your program,
6812 the arguments of the call,
6813 and the local variables of the function being called.
6814 The information is saved in a block of data called a @dfn{stack frame}.
6815 The stack frames are allocated in a region of memory called the @dfn{call
6818 When your program stops, the @value{GDBN} commands for examining the
6819 stack allow you to see all of this information.
6821 @cindex selected frame
6822 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6823 @value{GDBN} commands refer implicitly to the selected frame. In
6824 particular, whenever you ask @value{GDBN} for the value of a variable in
6825 your program, the value is found in the selected frame. There are
6826 special @value{GDBN} commands to select whichever frame you are
6827 interested in. @xref{Selection, ,Selecting a Frame}.
6829 When your program stops, @value{GDBN} automatically selects the
6830 currently executing frame and describes it briefly, similar to the
6831 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6834 * Frames:: Stack frames
6835 * Backtrace:: Backtraces
6836 * Frame Filter Management:: Managing frame filters
6837 * Selection:: Selecting a frame
6838 * Frame Info:: Information on a frame
6843 @section Stack Frames
6845 @cindex frame, definition
6847 The call stack is divided up into contiguous pieces called @dfn{stack
6848 frames}, or @dfn{frames} for short; each frame is the data associated
6849 with one call to one function. The frame contains the arguments given
6850 to the function, the function's local variables, and the address at
6851 which the function is executing.
6853 @cindex initial frame
6854 @cindex outermost frame
6855 @cindex innermost frame
6856 When your program is started, the stack has only one frame, that of the
6857 function @code{main}. This is called the @dfn{initial} frame or the
6858 @dfn{outermost} frame. Each time a function is called, a new frame is
6859 made. Each time a function returns, the frame for that function invocation
6860 is eliminated. If a function is recursive, there can be many frames for
6861 the same function. The frame for the function in which execution is
6862 actually occurring is called the @dfn{innermost} frame. This is the most
6863 recently created of all the stack frames that still exist.
6865 @cindex frame pointer
6866 Inside your program, stack frames are identified by their addresses. A
6867 stack frame consists of many bytes, each of which has its own address; each
6868 kind of computer has a convention for choosing one byte whose
6869 address serves as the address of the frame. Usually this address is kept
6870 in a register called the @dfn{frame pointer register}
6871 (@pxref{Registers, $fp}) while execution is going on in that frame.
6873 @cindex frame number
6874 @value{GDBN} assigns numbers to all existing stack frames, starting with
6875 zero for the innermost frame, one for the frame that called it,
6876 and so on upward. These numbers do not really exist in your program;
6877 they are assigned by @value{GDBN} to give you a way of designating stack
6878 frames in @value{GDBN} commands.
6880 @c The -fomit-frame-pointer below perennially causes hbox overflow
6881 @c underflow problems.
6882 @cindex frameless execution
6883 Some compilers provide a way to compile functions so that they operate
6884 without stack frames. (For example, the @value{NGCC} option
6886 @samp{-fomit-frame-pointer}
6888 generates functions without a frame.)
6889 This is occasionally done with heavily used library functions to save
6890 the frame setup time. @value{GDBN} has limited facilities for dealing
6891 with these function invocations. If the innermost function invocation
6892 has no stack frame, @value{GDBN} nevertheless regards it as though
6893 it had a separate frame, which is numbered zero as usual, allowing
6894 correct tracing of the function call chain. However, @value{GDBN} has
6895 no provision for frameless functions elsewhere in the stack.
6898 @kindex frame@r{, command}
6899 @cindex current stack frame
6900 @item frame @r{[}@var{framespec}@r{]}
6901 The @code{frame} command allows you to move from one stack frame to another,
6902 and to print the stack frame you select. The @var{framespec} may be either the
6903 address of the frame or the stack frame number. Without an argument,
6904 @code{frame} prints the current stack frame.
6906 @kindex select-frame
6907 @cindex selecting frame silently
6909 The @code{select-frame} command allows you to move from one stack frame
6910 to another without printing the frame. This is the silent version of
6918 @cindex call stack traces
6919 A backtrace is a summary of how your program got where it is. It shows one
6920 line per frame, for many frames, starting with the currently executing
6921 frame (frame zero), followed by its caller (frame one), and on up the
6924 @anchor{backtrace-command}
6927 @kindex bt @r{(@code{backtrace})}
6930 Print a backtrace of the entire stack: one line per frame for all
6931 frames in the stack.
6933 You can stop the backtrace at any time by typing the system interrupt
6934 character, normally @kbd{Ctrl-c}.
6936 @item backtrace @var{n}
6938 Similar, but print only the innermost @var{n} frames.
6940 @item backtrace -@var{n}
6942 Similar, but print only the outermost @var{n} frames.
6944 @item backtrace full
6946 @itemx bt full @var{n}
6947 @itemx bt full -@var{n}
6948 Print the values of the local variables also. As described above,
6949 @var{n} specifies the number of frames to print.
6951 @item backtrace no-filters
6952 @itemx bt no-filters
6953 @itemx bt no-filters @var{n}
6954 @itemx bt no-filters -@var{n}
6955 @itemx bt no-filters full
6956 @itemx bt no-filters full @var{n}
6957 @itemx bt no-filters full -@var{n}
6958 Do not run Python frame filters on this backtrace. @xref{Frame
6959 Filter API}, for more information. Additionally use @ref{disable
6960 frame-filter all} to turn off all frame filters. This is only
6961 relevant when @value{GDBN} has been configured with @code{Python}
6967 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6968 are additional aliases for @code{backtrace}.
6970 @cindex multiple threads, backtrace
6971 In a multi-threaded program, @value{GDBN} by default shows the
6972 backtrace only for the current thread. To display the backtrace for
6973 several or all of the threads, use the command @code{thread apply}
6974 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6975 apply all backtrace}, @value{GDBN} will display the backtrace for all
6976 the threads; this is handy when you debug a core dump of a
6977 multi-threaded program.
6979 Each line in the backtrace shows the frame number and the function name.
6980 The program counter value is also shown---unless you use @code{set
6981 print address off}. The backtrace also shows the source file name and
6982 line number, as well as the arguments to the function. The program
6983 counter value is omitted if it is at the beginning of the code for that
6986 Here is an example of a backtrace. It was made with the command
6987 @samp{bt 3}, so it shows the innermost three frames.
6991 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6993 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6994 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6996 (More stack frames follow...)
7001 The display for frame zero does not begin with a program counter
7002 value, indicating that your program has stopped at the beginning of the
7003 code for line @code{993} of @code{builtin.c}.
7006 The value of parameter @code{data} in frame 1 has been replaced by
7007 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7008 only if it is a scalar (integer, pointer, enumeration, etc). See command
7009 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7010 on how to configure the way function parameter values are printed.
7012 @cindex optimized out, in backtrace
7013 @cindex function call arguments, optimized out
7014 If your program was compiled with optimizations, some compilers will
7015 optimize away arguments passed to functions if those arguments are
7016 never used after the call. Such optimizations generate code that
7017 passes arguments through registers, but doesn't store those arguments
7018 in the stack frame. @value{GDBN} has no way of displaying such
7019 arguments in stack frames other than the innermost one. Here's what
7020 such a backtrace might look like:
7024 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7026 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7027 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7029 (More stack frames follow...)
7034 The values of arguments that were not saved in their stack frames are
7035 shown as @samp{<optimized out>}.
7037 If you need to display the values of such optimized-out arguments,
7038 either deduce that from other variables whose values depend on the one
7039 you are interested in, or recompile without optimizations.
7041 @cindex backtrace beyond @code{main} function
7042 @cindex program entry point
7043 @cindex startup code, and backtrace
7044 Most programs have a standard user entry point---a place where system
7045 libraries and startup code transition into user code. For C this is
7046 @code{main}@footnote{
7047 Note that embedded programs (the so-called ``free-standing''
7048 environment) are not required to have a @code{main} function as the
7049 entry point. They could even have multiple entry points.}.
7050 When @value{GDBN} finds the entry function in a backtrace
7051 it will terminate the backtrace, to avoid tracing into highly
7052 system-specific (and generally uninteresting) code.
7054 If you need to examine the startup code, or limit the number of levels
7055 in a backtrace, you can change this behavior:
7058 @item set backtrace past-main
7059 @itemx set backtrace past-main on
7060 @kindex set backtrace
7061 Backtraces will continue past the user entry point.
7063 @item set backtrace past-main off
7064 Backtraces will stop when they encounter the user entry point. This is the
7067 @item show backtrace past-main
7068 @kindex show backtrace
7069 Display the current user entry point backtrace policy.
7071 @item set backtrace past-entry
7072 @itemx set backtrace past-entry on
7073 Backtraces will continue past the internal entry point of an application.
7074 This entry point is encoded by the linker when the application is built,
7075 and is likely before the user entry point @code{main} (or equivalent) is called.
7077 @item set backtrace past-entry off
7078 Backtraces will stop when they encounter the internal entry point of an
7079 application. This is the default.
7081 @item show backtrace past-entry
7082 Display the current internal entry point backtrace policy.
7084 @item set backtrace limit @var{n}
7085 @itemx set backtrace limit 0
7086 @itemx set backtrace limit unlimited
7087 @cindex backtrace limit
7088 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7089 or zero means unlimited levels.
7091 @item show backtrace limit
7092 Display the current limit on backtrace levels.
7095 You can control how file names are displayed.
7098 @item set filename-display
7099 @itemx set filename-display relative
7100 @cindex filename-display
7101 Display file names relative to the compilation directory. This is the default.
7103 @item set filename-display basename
7104 Display only basename of a filename.
7106 @item set filename-display absolute
7107 Display an absolute filename.
7109 @item show filename-display
7110 Show the current way to display filenames.
7113 @node Frame Filter Management
7114 @section Management of Frame Filters.
7115 @cindex managing frame filters
7117 Frame filters are Python based utilities to manage and decorate the
7118 output of frames. @xref{Frame Filter API}, for further information.
7120 Managing frame filters is performed by several commands available
7121 within @value{GDBN}, detailed here.
7124 @kindex info frame-filter
7125 @item info frame-filter
7126 Print a list of installed frame filters from all dictionaries, showing
7127 their name, priority and enabled status.
7129 @kindex disable frame-filter
7130 @anchor{disable frame-filter all}
7131 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7132 Disable a frame filter in the dictionary matching
7133 @var{filter-dictionary} and @var{filter-name}. The
7134 @var{filter-dictionary} may be @code{all}, @code{global},
7135 @code{progspace}, or the name of the object file where the frame filter
7136 dictionary resides. When @code{all} is specified, all frame filters
7137 across all dictionaries are disabled. The @var{filter-name} is the name
7138 of the frame filter and is used when @code{all} is not the option for
7139 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7140 may be enabled again later.
7142 @kindex enable frame-filter
7143 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7144 Enable a frame filter in the dictionary matching
7145 @var{filter-dictionary} and @var{filter-name}. The
7146 @var{filter-dictionary} may be @code{all}, @code{global},
7147 @code{progspace} or the name of the object file where the frame filter
7148 dictionary resides. When @code{all} is specified, all frame filters across
7149 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7150 filter and is used when @code{all} is not the option for
7151 @var{filter-dictionary}.
7156 (gdb) info frame-filter
7158 global frame-filters:
7159 Priority Enabled Name
7160 1000 No PrimaryFunctionFilter
7163 progspace /build/test frame-filters:
7164 Priority Enabled Name
7165 100 Yes ProgspaceFilter
7167 objfile /build/test frame-filters:
7168 Priority Enabled Name
7169 999 Yes BuildProgra Filter
7171 (gdb) disable frame-filter /build/test BuildProgramFilter
7172 (gdb) info frame-filter
7174 global frame-filters:
7175 Priority Enabled Name
7176 1000 No PrimaryFunctionFilter
7179 progspace /build/test frame-filters:
7180 Priority Enabled Name
7181 100 Yes ProgspaceFilter
7183 objfile /build/test frame-filters:
7184 Priority Enabled Name
7185 999 No BuildProgramFilter
7187 (gdb) enable frame-filter global PrimaryFunctionFilter
7188 (gdb) info frame-filter
7190 global frame-filters:
7191 Priority Enabled Name
7192 1000 Yes PrimaryFunctionFilter
7195 progspace /build/test frame-filters:
7196 Priority Enabled Name
7197 100 Yes ProgspaceFilter
7199 objfile /build/test frame-filters:
7200 Priority Enabled Name
7201 999 No BuildProgramFilter
7204 @kindex set frame-filter priority
7205 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7206 Set the @var{priority} of a frame filter in the dictionary matching
7207 @var{filter-dictionary}, and the frame filter name matching
7208 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7209 @code{progspace} or the name of the object file where the frame filter
7210 dictionary resides. The @var{priority} is an integer.
7212 @kindex show frame-filter priority
7213 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7214 Show the @var{priority} of a frame filter in the dictionary matching
7215 @var{filter-dictionary}, and the frame filter name matching
7216 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7217 @code{progspace} or the name of the object file where the frame filter
7223 (gdb) info frame-filter
7225 global frame-filters:
7226 Priority Enabled Name
7227 1000 Yes PrimaryFunctionFilter
7230 progspace /build/test frame-filters:
7231 Priority Enabled Name
7232 100 Yes ProgspaceFilter
7234 objfile /build/test frame-filters:
7235 Priority Enabled Name
7236 999 No BuildProgramFilter
7238 (gdb) set frame-filter priority global Reverse 50
7239 (gdb) info frame-filter
7241 global frame-filters:
7242 Priority Enabled Name
7243 1000 Yes PrimaryFunctionFilter
7246 progspace /build/test frame-filters:
7247 Priority Enabled Name
7248 100 Yes ProgspaceFilter
7250 objfile /build/test frame-filters:
7251 Priority Enabled Name
7252 999 No BuildProgramFilter
7257 @section Selecting a Frame
7259 Most commands for examining the stack and other data in your program work on
7260 whichever stack frame is selected at the moment. Here are the commands for
7261 selecting a stack frame; all of them finish by printing a brief description
7262 of the stack frame just selected.
7265 @kindex frame@r{, selecting}
7266 @kindex f @r{(@code{frame})}
7269 Select frame number @var{n}. Recall that frame zero is the innermost
7270 (currently executing) frame, frame one is the frame that called the
7271 innermost one, and so on. The highest-numbered frame is the one for
7274 @item frame @var{addr}
7276 Select the frame at address @var{addr}. This is useful mainly if the
7277 chaining of stack frames has been damaged by a bug, making it
7278 impossible for @value{GDBN} to assign numbers properly to all frames. In
7279 addition, this can be useful when your program has multiple stacks and
7280 switches between them.
7282 On the SPARC architecture, @code{frame} needs two addresses to
7283 select an arbitrary frame: a frame pointer and a stack pointer.
7285 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7286 pointer and a program counter.
7288 On the 29k architecture, it needs three addresses: a register stack
7289 pointer, a program counter, and a memory stack pointer.
7293 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7294 numbers @var{n}, this advances toward the outermost frame, to higher
7295 frame numbers, to frames that have existed longer.
7298 @kindex do @r{(@code{down})}
7300 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7301 positive numbers @var{n}, this advances toward the innermost frame, to
7302 lower frame numbers, to frames that were created more recently.
7303 You may abbreviate @code{down} as @code{do}.
7306 All of these commands end by printing two lines of output describing the
7307 frame. The first line shows the frame number, the function name, the
7308 arguments, and the source file and line number of execution in that
7309 frame. The second line shows the text of that source line.
7317 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7319 10 read_input_file (argv[i]);
7323 After such a printout, the @code{list} command with no arguments
7324 prints ten lines centered on the point of execution in the frame.
7325 You can also edit the program at the point of execution with your favorite
7326 editing program by typing @code{edit}.
7327 @xref{List, ,Printing Source Lines},
7331 @kindex down-silently
7333 @item up-silently @var{n}
7334 @itemx down-silently @var{n}
7335 These two commands are variants of @code{up} and @code{down},
7336 respectively; they differ in that they do their work silently, without
7337 causing display of the new frame. They are intended primarily for use
7338 in @value{GDBN} command scripts, where the output might be unnecessary and
7343 @section Information About a Frame
7345 There are several other commands to print information about the selected
7351 When used without any argument, this command does not change which
7352 frame is selected, but prints a brief description of the currently
7353 selected stack frame. It can be abbreviated @code{f}. With an
7354 argument, this command is used to select a stack frame.
7355 @xref{Selection, ,Selecting a Frame}.
7358 @kindex info f @r{(@code{info frame})}
7361 This command prints a verbose description of the selected stack frame,
7366 the address of the frame
7368 the address of the next frame down (called by this frame)
7370 the address of the next frame up (caller of this frame)
7372 the language in which the source code corresponding to this frame is written
7374 the address of the frame's arguments
7376 the address of the frame's local variables
7378 the program counter saved in it (the address of execution in the caller frame)
7380 which registers were saved in the frame
7383 @noindent The verbose description is useful when
7384 something has gone wrong that has made the stack format fail to fit
7385 the usual conventions.
7387 @item info frame @var{addr}
7388 @itemx info f @var{addr}
7389 Print a verbose description of the frame at address @var{addr}, without
7390 selecting that frame. The selected frame remains unchanged by this
7391 command. This requires the same kind of address (more than one for some
7392 architectures) that you specify in the @code{frame} command.
7393 @xref{Selection, ,Selecting a Frame}.
7397 Print the arguments of the selected frame, each on a separate line.
7401 Print the local variables of the selected frame, each on a separate
7402 line. These are all variables (declared either static or automatic)
7403 accessible at the point of execution of the selected frame.
7409 @chapter Examining Source Files
7411 @value{GDBN} can print parts of your program's source, since the debugging
7412 information recorded in the program tells @value{GDBN} what source files were
7413 used to build it. When your program stops, @value{GDBN} spontaneously prints
7414 the line where it stopped. Likewise, when you select a stack frame
7415 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7416 execution in that frame has stopped. You can print other portions of
7417 source files by explicit command.
7419 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7420 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7421 @value{GDBN} under @sc{gnu} Emacs}.
7424 * List:: Printing source lines
7425 * Specify Location:: How to specify code locations
7426 * Edit:: Editing source files
7427 * Search:: Searching source files
7428 * Source Path:: Specifying source directories
7429 * Machine Code:: Source and machine code
7433 @section Printing Source Lines
7436 @kindex l @r{(@code{list})}
7437 To print lines from a source file, use the @code{list} command
7438 (abbreviated @code{l}). By default, ten lines are printed.
7439 There are several ways to specify what part of the file you want to
7440 print; see @ref{Specify Location}, for the full list.
7442 Here are the forms of the @code{list} command most commonly used:
7445 @item list @var{linenum}
7446 Print lines centered around line number @var{linenum} in the
7447 current source file.
7449 @item list @var{function}
7450 Print lines centered around the beginning of function
7454 Print more lines. If the last lines printed were printed with a
7455 @code{list} command, this prints lines following the last lines
7456 printed; however, if the last line printed was a solitary line printed
7457 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7458 Stack}), this prints lines centered around that line.
7461 Print lines just before the lines last printed.
7464 @cindex @code{list}, how many lines to display
7465 By default, @value{GDBN} prints ten source lines with any of these forms of
7466 the @code{list} command. You can change this using @code{set listsize}:
7469 @kindex set listsize
7470 @item set listsize @var{count}
7471 @itemx set listsize unlimited
7472 Make the @code{list} command display @var{count} source lines (unless
7473 the @code{list} argument explicitly specifies some other number).
7474 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7476 @kindex show listsize
7478 Display the number of lines that @code{list} prints.
7481 Repeating a @code{list} command with @key{RET} discards the argument,
7482 so it is equivalent to typing just @code{list}. This is more useful
7483 than listing the same lines again. An exception is made for an
7484 argument of @samp{-}; that argument is preserved in repetition so that
7485 each repetition moves up in the source file.
7487 In general, the @code{list} command expects you to supply zero, one or two
7488 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7489 of writing them (@pxref{Specify Location}), but the effect is always
7490 to specify some source line.
7492 Here is a complete description of the possible arguments for @code{list}:
7495 @item list @var{linespec}
7496 Print lines centered around the line specified by @var{linespec}.
7498 @item list @var{first},@var{last}
7499 Print lines from @var{first} to @var{last}. Both arguments are
7500 linespecs. When a @code{list} command has two linespecs, and the
7501 source file of the second linespec is omitted, this refers to
7502 the same source file as the first linespec.
7504 @item list ,@var{last}
7505 Print lines ending with @var{last}.
7507 @item list @var{first},
7508 Print lines starting with @var{first}.
7511 Print lines just after the lines last printed.
7514 Print lines just before the lines last printed.
7517 As described in the preceding table.
7520 @node Specify Location
7521 @section Specifying a Location
7522 @cindex specifying location
7525 Several @value{GDBN} commands accept arguments that specify a location
7526 of your program's code. Since @value{GDBN} is a source-level
7527 debugger, a location usually specifies some line in the source code;
7528 for that reason, locations are also known as @dfn{linespecs}.
7530 Here are all the different ways of specifying a code location that
7531 @value{GDBN} understands:
7535 Specifies the line number @var{linenum} of the current source file.
7538 @itemx +@var{offset}
7539 Specifies the line @var{offset} lines before or after the @dfn{current
7540 line}. For the @code{list} command, the current line is the last one
7541 printed; for the breakpoint commands, this is the line at which
7542 execution stopped in the currently selected @dfn{stack frame}
7543 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7544 used as the second of the two linespecs in a @code{list} command,
7545 this specifies the line @var{offset} lines up or down from the first
7548 @item @var{filename}:@var{linenum}
7549 Specifies the line @var{linenum} in the source file @var{filename}.
7550 If @var{filename} is a relative file name, then it will match any
7551 source file name with the same trailing components. For example, if
7552 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7553 name of @file{/build/trunk/gcc/expr.c}, but not
7554 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7556 @item @var{function}
7557 Specifies the line that begins the body of the function @var{function}.
7558 For example, in C, this is the line with the open brace.
7560 @item @var{function}:@var{label}
7561 Specifies the line where @var{label} appears in @var{function}.
7563 @item @var{filename}:@var{function}
7564 Specifies the line that begins the body of the function @var{function}
7565 in the file @var{filename}. You only need the file name with a
7566 function name to avoid ambiguity when there are identically named
7567 functions in different source files.
7570 Specifies the line at which the label named @var{label} appears.
7571 @value{GDBN} searches for the label in the function corresponding to
7572 the currently selected stack frame. If there is no current selected
7573 stack frame (for instance, if the inferior is not running), then
7574 @value{GDBN} will not search for a label.
7576 @item *@var{address}
7577 Specifies the program address @var{address}. For line-oriented
7578 commands, such as @code{list} and @code{edit}, this specifies a source
7579 line that contains @var{address}. For @code{break} and other
7580 breakpoint oriented commands, this can be used to set breakpoints in
7581 parts of your program which do not have debugging information or
7584 Here @var{address} may be any expression valid in the current working
7585 language (@pxref{Languages, working language}) that specifies a code
7586 address. In addition, as a convenience, @value{GDBN} extends the
7587 semantics of expressions used in locations to cover the situations
7588 that frequently happen during debugging. Here are the various forms
7592 @item @var{expression}
7593 Any expression valid in the current working language.
7595 @item @var{funcaddr}
7596 An address of a function or procedure derived from its name. In C,
7597 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7598 simply the function's name @var{function} (and actually a special case
7599 of a valid expression). In Pascal and Modula-2, this is
7600 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7601 (although the Pascal form also works).
7603 This form specifies the address of the function's first instruction,
7604 before the stack frame and arguments have been set up.
7606 @item '@var{filename}':@var{funcaddr}
7607 Like @var{funcaddr} above, but also specifies the name of the source
7608 file explicitly. This is useful if the name of the function does not
7609 specify the function unambiguously, e.g., if there are several
7610 functions with identical names in different source files.
7613 @cindex breakpoint at static probe point
7614 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7615 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7616 applications to embed static probes. @xref{Static Probe Points}, for more
7617 information on finding and using static probes. This form of linespec
7618 specifies the location of such a static probe.
7620 If @var{objfile} is given, only probes coming from that shared library
7621 or executable matching @var{objfile} as a regular expression are considered.
7622 If @var{provider} is given, then only probes from that provider are considered.
7623 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7624 each one of those probes.
7630 @section Editing Source Files
7631 @cindex editing source files
7634 @kindex e @r{(@code{edit})}
7635 To edit the lines in a source file, use the @code{edit} command.
7636 The editing program of your choice
7637 is invoked with the current line set to
7638 the active line in the program.
7639 Alternatively, there are several ways to specify what part of the file you
7640 want to print if you want to see other parts of the program:
7643 @item edit @var{location}
7644 Edit the source file specified by @code{location}. Editing starts at
7645 that @var{location}, e.g., at the specified source line of the
7646 specified file. @xref{Specify Location}, for all the possible forms
7647 of the @var{location} argument; here are the forms of the @code{edit}
7648 command most commonly used:
7651 @item edit @var{number}
7652 Edit the current source file with @var{number} as the active line number.
7654 @item edit @var{function}
7655 Edit the file containing @var{function} at the beginning of its definition.
7660 @subsection Choosing your Editor
7661 You can customize @value{GDBN} to use any editor you want
7663 The only restriction is that your editor (say @code{ex}), recognizes the
7664 following command-line syntax:
7666 ex +@var{number} file
7668 The optional numeric value +@var{number} specifies the number of the line in
7669 the file where to start editing.}.
7670 By default, it is @file{@value{EDITOR}}, but you can change this
7671 by setting the environment variable @code{EDITOR} before using
7672 @value{GDBN}. For example, to configure @value{GDBN} to use the
7673 @code{vi} editor, you could use these commands with the @code{sh} shell:
7679 or in the @code{csh} shell,
7681 setenv EDITOR /usr/bin/vi
7686 @section Searching Source Files
7687 @cindex searching source files
7689 There are two commands for searching through the current source file for a
7694 @kindex forward-search
7695 @kindex fo @r{(@code{forward-search})}
7696 @item forward-search @var{regexp}
7697 @itemx search @var{regexp}
7698 The command @samp{forward-search @var{regexp}} checks each line,
7699 starting with the one following the last line listed, for a match for
7700 @var{regexp}. It lists the line that is found. You can use the
7701 synonym @samp{search @var{regexp}} or abbreviate the command name as
7704 @kindex reverse-search
7705 @item reverse-search @var{regexp}
7706 The command @samp{reverse-search @var{regexp}} checks each line, starting
7707 with the one before the last line listed and going backward, for a match
7708 for @var{regexp}. It lists the line that is found. You can abbreviate
7709 this command as @code{rev}.
7713 @section Specifying Source Directories
7716 @cindex directories for source files
7717 Executable programs sometimes do not record the directories of the source
7718 files from which they were compiled, just the names. Even when they do,
7719 the directories could be moved between the compilation and your debugging
7720 session. @value{GDBN} has a list of directories to search for source files;
7721 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7722 it tries all the directories in the list, in the order they are present
7723 in the list, until it finds a file with the desired name.
7725 For example, suppose an executable references the file
7726 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7727 @file{/mnt/cross}. The file is first looked up literally; if this
7728 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7729 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7730 message is printed. @value{GDBN} does not look up the parts of the
7731 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7732 Likewise, the subdirectories of the source path are not searched: if
7733 the source path is @file{/mnt/cross}, and the binary refers to
7734 @file{foo.c}, @value{GDBN} would not find it under
7735 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7737 Plain file names, relative file names with leading directories, file
7738 names containing dots, etc.@: are all treated as described above; for
7739 instance, if the source path is @file{/mnt/cross}, and the source file
7740 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7741 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7742 that---@file{/mnt/cross/foo.c}.
7744 Note that the executable search path is @emph{not} used to locate the
7747 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7748 any information it has cached about where source files are found and where
7749 each line is in the file.
7753 When you start @value{GDBN}, its source path includes only @samp{cdir}
7754 and @samp{cwd}, in that order.
7755 To add other directories, use the @code{directory} command.
7757 The search path is used to find both program source files and @value{GDBN}
7758 script files (read using the @samp{-command} option and @samp{source} command).
7760 In addition to the source path, @value{GDBN} provides a set of commands
7761 that manage a list of source path substitution rules. A @dfn{substitution
7762 rule} specifies how to rewrite source directories stored in the program's
7763 debug information in case the sources were moved to a different
7764 directory between compilation and debugging. A rule is made of
7765 two strings, the first specifying what needs to be rewritten in
7766 the path, and the second specifying how it should be rewritten.
7767 In @ref{set substitute-path}, we name these two parts @var{from} and
7768 @var{to} respectively. @value{GDBN} does a simple string replacement
7769 of @var{from} with @var{to} at the start of the directory part of the
7770 source file name, and uses that result instead of the original file
7771 name to look up the sources.
7773 Using the previous example, suppose the @file{foo-1.0} tree has been
7774 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7775 @value{GDBN} to replace @file{/usr/src} in all source path names with
7776 @file{/mnt/cross}. The first lookup will then be
7777 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7778 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7779 substitution rule, use the @code{set substitute-path} command
7780 (@pxref{set substitute-path}).
7782 To avoid unexpected substitution results, a rule is applied only if the
7783 @var{from} part of the directory name ends at a directory separator.
7784 For instance, a rule substituting @file{/usr/source} into
7785 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7786 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7787 is applied only at the beginning of the directory name, this rule will
7788 not be applied to @file{/root/usr/source/baz.c} either.
7790 In many cases, you can achieve the same result using the @code{directory}
7791 command. However, @code{set substitute-path} can be more efficient in
7792 the case where the sources are organized in a complex tree with multiple
7793 subdirectories. With the @code{directory} command, you need to add each
7794 subdirectory of your project. If you moved the entire tree while
7795 preserving its internal organization, then @code{set substitute-path}
7796 allows you to direct the debugger to all the sources with one single
7799 @code{set substitute-path} is also more than just a shortcut command.
7800 The source path is only used if the file at the original location no
7801 longer exists. On the other hand, @code{set substitute-path} modifies
7802 the debugger behavior to look at the rewritten location instead. So, if
7803 for any reason a source file that is not relevant to your executable is
7804 located at the original location, a substitution rule is the only
7805 method available to point @value{GDBN} at the new location.
7807 @cindex @samp{--with-relocated-sources}
7808 @cindex default source path substitution
7809 You can configure a default source path substitution rule by
7810 configuring @value{GDBN} with the
7811 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7812 should be the name of a directory under @value{GDBN}'s configured
7813 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7814 directory names in debug information under @var{dir} will be adjusted
7815 automatically if the installed @value{GDBN} is moved to a new
7816 location. This is useful if @value{GDBN}, libraries or executables
7817 with debug information and corresponding source code are being moved
7821 @item directory @var{dirname} @dots{}
7822 @item dir @var{dirname} @dots{}
7823 Add directory @var{dirname} to the front of the source path. Several
7824 directory names may be given to this command, separated by @samp{:}
7825 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7826 part of absolute file names) or
7827 whitespace. You may specify a directory that is already in the source
7828 path; this moves it forward, so @value{GDBN} searches it sooner.
7832 @vindex $cdir@r{, convenience variable}
7833 @vindex $cwd@r{, convenience variable}
7834 @cindex compilation directory
7835 @cindex current directory
7836 @cindex working directory
7837 @cindex directory, current
7838 @cindex directory, compilation
7839 You can use the string @samp{$cdir} to refer to the compilation
7840 directory (if one is recorded), and @samp{$cwd} to refer to the current
7841 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7842 tracks the current working directory as it changes during your @value{GDBN}
7843 session, while the latter is immediately expanded to the current
7844 directory at the time you add an entry to the source path.
7847 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7849 @c RET-repeat for @code{directory} is explicitly disabled, but since
7850 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7852 @item set directories @var{path-list}
7853 @kindex set directories
7854 Set the source path to @var{path-list}.
7855 @samp{$cdir:$cwd} are added if missing.
7857 @item show directories
7858 @kindex show directories
7859 Print the source path: show which directories it contains.
7861 @anchor{set substitute-path}
7862 @item set substitute-path @var{from} @var{to}
7863 @kindex set substitute-path
7864 Define a source path substitution rule, and add it at the end of the
7865 current list of existing substitution rules. If a rule with the same
7866 @var{from} was already defined, then the old rule is also deleted.
7868 For example, if the file @file{/foo/bar/baz.c} was moved to
7869 @file{/mnt/cross/baz.c}, then the command
7872 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7876 will tell @value{GDBN} to replace @samp{/usr/src} with
7877 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7878 @file{baz.c} even though it was moved.
7880 In the case when more than one substitution rule have been defined,
7881 the rules are evaluated one by one in the order where they have been
7882 defined. The first one matching, if any, is selected to perform
7885 For instance, if we had entered the following commands:
7888 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7889 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7893 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7894 @file{/mnt/include/defs.h} by using the first rule. However, it would
7895 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7896 @file{/mnt/src/lib/foo.c}.
7899 @item unset substitute-path [path]
7900 @kindex unset substitute-path
7901 If a path is specified, search the current list of substitution rules
7902 for a rule that would rewrite that path. Delete that rule if found.
7903 A warning is emitted by the debugger if no rule could be found.
7905 If no path is specified, then all substitution rules are deleted.
7907 @item show substitute-path [path]
7908 @kindex show substitute-path
7909 If a path is specified, then print the source path substitution rule
7910 which would rewrite that path, if any.
7912 If no path is specified, then print all existing source path substitution
7917 If your source path is cluttered with directories that are no longer of
7918 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7919 versions of source. You can correct the situation as follows:
7923 Use @code{directory} with no argument to reset the source path to its default value.
7926 Use @code{directory} with suitable arguments to reinstall the
7927 directories you want in the source path. You can add all the
7928 directories in one command.
7932 @section Source and Machine Code
7933 @cindex source line and its code address
7935 You can use the command @code{info line} to map source lines to program
7936 addresses (and vice versa), and the command @code{disassemble} to display
7937 a range of addresses as machine instructions. You can use the command
7938 @code{set disassemble-next-line} to set whether to disassemble next
7939 source line when execution stops. When run under @sc{gnu} Emacs
7940 mode, the @code{info line} command causes the arrow to point to the
7941 line specified. Also, @code{info line} prints addresses in symbolic form as
7946 @item info line @var{linespec}
7947 Print the starting and ending addresses of the compiled code for
7948 source line @var{linespec}. You can specify source lines in any of
7949 the ways documented in @ref{Specify Location}.
7952 For example, we can use @code{info line} to discover the location of
7953 the object code for the first line of function
7954 @code{m4_changequote}:
7956 @c FIXME: I think this example should also show the addresses in
7957 @c symbolic form, as they usually would be displayed.
7959 (@value{GDBP}) info line m4_changequote
7960 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7964 @cindex code address and its source line
7965 We can also inquire (using @code{*@var{addr}} as the form for
7966 @var{linespec}) what source line covers a particular address:
7968 (@value{GDBP}) info line *0x63ff
7969 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7972 @cindex @code{$_} and @code{info line}
7973 @cindex @code{x} command, default address
7974 @kindex x@r{(examine), and} info line
7975 After @code{info line}, the default address for the @code{x} command
7976 is changed to the starting address of the line, so that @samp{x/i} is
7977 sufficient to begin examining the machine code (@pxref{Memory,
7978 ,Examining Memory}). Also, this address is saved as the value of the
7979 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7984 @cindex assembly instructions
7985 @cindex instructions, assembly
7986 @cindex machine instructions
7987 @cindex listing machine instructions
7989 @itemx disassemble /m
7990 @itemx disassemble /r
7991 This specialized command dumps a range of memory as machine
7992 instructions. It can also print mixed source+disassembly by specifying
7993 the @code{/m} modifier and print the raw instructions in hex as well as
7994 in symbolic form by specifying the @code{/r}.
7995 The default memory range is the function surrounding the
7996 program counter of the selected frame. A single argument to this
7997 command is a program counter value; @value{GDBN} dumps the function
7998 surrounding this value. When two arguments are given, they should
7999 be separated by a comma, possibly surrounded by whitespace. The
8000 arguments specify a range of addresses to dump, in one of two forms:
8003 @item @var{start},@var{end}
8004 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8005 @item @var{start},+@var{length}
8006 the addresses from @var{start} (inclusive) to
8007 @code{@var{start}+@var{length}} (exclusive).
8011 When 2 arguments are specified, the name of the function is also
8012 printed (since there could be several functions in the given range).
8014 The argument(s) can be any expression yielding a numeric value, such as
8015 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8017 If the range of memory being disassembled contains current program counter,
8018 the instruction at that location is shown with a @code{=>} marker.
8021 The following example shows the disassembly of a range of addresses of
8022 HP PA-RISC 2.0 code:
8025 (@value{GDBP}) disas 0x32c4, 0x32e4
8026 Dump of assembler code from 0x32c4 to 0x32e4:
8027 0x32c4 <main+204>: addil 0,dp
8028 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8029 0x32cc <main+212>: ldil 0x3000,r31
8030 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8031 0x32d4 <main+220>: ldo 0(r31),rp
8032 0x32d8 <main+224>: addil -0x800,dp
8033 0x32dc <main+228>: ldo 0x588(r1),r26
8034 0x32e0 <main+232>: ldil 0x3000,r31
8035 End of assembler dump.
8038 Here is an example showing mixed source+assembly for Intel x86, when the
8039 program is stopped just after function prologue:
8042 (@value{GDBP}) disas /m main
8043 Dump of assembler code for function main:
8045 0x08048330 <+0>: push %ebp
8046 0x08048331 <+1>: mov %esp,%ebp
8047 0x08048333 <+3>: sub $0x8,%esp
8048 0x08048336 <+6>: and $0xfffffff0,%esp
8049 0x08048339 <+9>: sub $0x10,%esp
8051 6 printf ("Hello.\n");
8052 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8053 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8057 0x08048348 <+24>: mov $0x0,%eax
8058 0x0804834d <+29>: leave
8059 0x0804834e <+30>: ret
8061 End of assembler dump.
8064 Here is another example showing raw instructions in hex for AMD x86-64,
8067 (gdb) disas /r 0x400281,+10
8068 Dump of assembler code from 0x400281 to 0x40028b:
8069 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8070 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8071 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8072 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8073 End of assembler dump.
8076 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
8077 So, for example, if you want to disassemble function @code{bar}
8078 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8079 and not @samp{disassemble foo.c:bar}.
8081 Some architectures have more than one commonly-used set of instruction
8082 mnemonics or other syntax.
8084 For programs that were dynamically linked and use shared libraries,
8085 instructions that call functions or branch to locations in the shared
8086 libraries might show a seemingly bogus location---it's actually a
8087 location of the relocation table. On some architectures, @value{GDBN}
8088 might be able to resolve these to actual function names.
8091 @kindex set disassembly-flavor
8092 @cindex Intel disassembly flavor
8093 @cindex AT&T disassembly flavor
8094 @item set disassembly-flavor @var{instruction-set}
8095 Select the instruction set to use when disassembling the
8096 program via the @code{disassemble} or @code{x/i} commands.
8098 Currently this command is only defined for the Intel x86 family. You
8099 can set @var{instruction-set} to either @code{intel} or @code{att}.
8100 The default is @code{att}, the AT&T flavor used by default by Unix
8101 assemblers for x86-based targets.
8103 @kindex show disassembly-flavor
8104 @item show disassembly-flavor
8105 Show the current setting of the disassembly flavor.
8109 @kindex set disassemble-next-line
8110 @kindex show disassemble-next-line
8111 @item set disassemble-next-line
8112 @itemx show disassemble-next-line
8113 Control whether or not @value{GDBN} will disassemble the next source
8114 line or instruction when execution stops. If ON, @value{GDBN} will
8115 display disassembly of the next source line when execution of the
8116 program being debugged stops. This is @emph{in addition} to
8117 displaying the source line itself, which @value{GDBN} always does if
8118 possible. If the next source line cannot be displayed for some reason
8119 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8120 info in the debug info), @value{GDBN} will display disassembly of the
8121 next @emph{instruction} instead of showing the next source line. If
8122 AUTO, @value{GDBN} will display disassembly of next instruction only
8123 if the source line cannot be displayed. This setting causes
8124 @value{GDBN} to display some feedback when you step through a function
8125 with no line info or whose source file is unavailable. The default is
8126 OFF, which means never display the disassembly of the next line or
8132 @chapter Examining Data
8134 @cindex printing data
8135 @cindex examining data
8138 The usual way to examine data in your program is with the @code{print}
8139 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8140 evaluates and prints the value of an expression of the language your
8141 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8142 Different Languages}). It may also print the expression using a
8143 Python-based pretty-printer (@pxref{Pretty Printing}).
8146 @item print @var{expr}
8147 @itemx print /@var{f} @var{expr}
8148 @var{expr} is an expression (in the source language). By default the
8149 value of @var{expr} is printed in a format appropriate to its data type;
8150 you can choose a different format by specifying @samp{/@var{f}}, where
8151 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8155 @itemx print /@var{f}
8156 @cindex reprint the last value
8157 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8158 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8159 conveniently inspect the same value in an alternative format.
8162 A more low-level way of examining data is with the @code{x} command.
8163 It examines data in memory at a specified address and prints it in a
8164 specified format. @xref{Memory, ,Examining Memory}.
8166 If you are interested in information about types, or about how the
8167 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8168 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8171 @cindex exploring hierarchical data structures
8173 Another way of examining values of expressions and type information is
8174 through the Python extension command @code{explore} (available only if
8175 the @value{GDBN} build is configured with @code{--with-python}). It
8176 offers an interactive way to start at the highest level (or, the most
8177 abstract level) of the data type of an expression (or, the data type
8178 itself) and explore all the way down to leaf scalar values/fields
8179 embedded in the higher level data types.
8182 @item explore @var{arg}
8183 @var{arg} is either an expression (in the source language), or a type
8184 visible in the current context of the program being debugged.
8187 The working of the @code{explore} command can be illustrated with an
8188 example. If a data type @code{struct ComplexStruct} is defined in your
8198 struct ComplexStruct
8200 struct SimpleStruct *ss_p;
8206 followed by variable declarations as
8209 struct SimpleStruct ss = @{ 10, 1.11 @};
8210 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8214 then, the value of the variable @code{cs} can be explored using the
8215 @code{explore} command as follows.
8219 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8220 the following fields:
8222 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8223 arr = <Enter 1 to explore this field of type `int [10]'>
8225 Enter the field number of choice:
8229 Since the fields of @code{cs} are not scalar values, you are being
8230 prompted to chose the field you want to explore. Let's say you choose
8231 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8232 pointer, you will be asked if it is pointing to a single value. From
8233 the declaration of @code{cs} above, it is indeed pointing to a single
8234 value, hence you enter @code{y}. If you enter @code{n}, then you will
8235 be asked if it were pointing to an array of values, in which case this
8236 field will be explored as if it were an array.
8239 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8240 Continue exploring it as a pointer to a single value [y/n]: y
8241 The value of `*(cs.ss_p)' is a struct/class of type `struct
8242 SimpleStruct' with the following fields:
8244 i = 10 .. (Value of type `int')
8245 d = 1.1100000000000001 .. (Value of type `double')
8247 Press enter to return to parent value:
8251 If the field @code{arr} of @code{cs} was chosen for exploration by
8252 entering @code{1} earlier, then since it is as array, you will be
8253 prompted to enter the index of the element in the array that you want
8257 `cs.arr' is an array of `int'.
8258 Enter the index of the element you want to explore in `cs.arr': 5
8260 `(cs.arr)[5]' is a scalar value of type `int'.
8264 Press enter to return to parent value:
8267 In general, at any stage of exploration, you can go deeper towards the
8268 leaf values by responding to the prompts appropriately, or hit the
8269 return key to return to the enclosing data structure (the @i{higher}
8270 level data structure).
8272 Similar to exploring values, you can use the @code{explore} command to
8273 explore types. Instead of specifying a value (which is typically a
8274 variable name or an expression valid in the current context of the
8275 program being debugged), you specify a type name. If you consider the
8276 same example as above, your can explore the type
8277 @code{struct ComplexStruct} by passing the argument
8278 @code{struct ComplexStruct} to the @code{explore} command.
8281 (gdb) explore struct ComplexStruct
8285 By responding to the prompts appropriately in the subsequent interactive
8286 session, you can explore the type @code{struct ComplexStruct} in a
8287 manner similar to how the value @code{cs} was explored in the above
8290 The @code{explore} command also has two sub-commands,
8291 @code{explore value} and @code{explore type}. The former sub-command is
8292 a way to explicitly specify that value exploration of the argument is
8293 being invoked, while the latter is a way to explicitly specify that type
8294 exploration of the argument is being invoked.
8297 @item explore value @var{expr}
8298 @cindex explore value
8299 This sub-command of @code{explore} explores the value of the
8300 expression @var{expr} (if @var{expr} is an expression valid in the
8301 current context of the program being debugged). The behavior of this
8302 command is identical to that of the behavior of the @code{explore}
8303 command being passed the argument @var{expr}.
8305 @item explore type @var{arg}
8306 @cindex explore type
8307 This sub-command of @code{explore} explores the type of @var{arg} (if
8308 @var{arg} is a type visible in the current context of program being
8309 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8310 is an expression valid in the current context of the program being
8311 debugged). If @var{arg} is a type, then the behavior of this command is
8312 identical to that of the @code{explore} command being passed the
8313 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8314 this command will be identical to that of the @code{explore} command
8315 being passed the type of @var{arg} as the argument.
8319 * Expressions:: Expressions
8320 * Ambiguous Expressions:: Ambiguous Expressions
8321 * Variables:: Program variables
8322 * Arrays:: Artificial arrays
8323 * Output Formats:: Output formats
8324 * Memory:: Examining memory
8325 * Auto Display:: Automatic display
8326 * Print Settings:: Print settings
8327 * Pretty Printing:: Python pretty printing
8328 * Value History:: Value history
8329 * Convenience Vars:: Convenience variables
8330 * Convenience Funs:: Convenience functions
8331 * Registers:: Registers
8332 * Floating Point Hardware:: Floating point hardware
8333 * Vector Unit:: Vector Unit
8334 * OS Information:: Auxiliary data provided by operating system
8335 * Memory Region Attributes:: Memory region attributes
8336 * Dump/Restore Files:: Copy between memory and a file
8337 * Core File Generation:: Cause a program dump its core
8338 * Character Sets:: Debugging programs that use a different
8339 character set than GDB does
8340 * Caching Target Data:: Data caching for targets
8341 * Searching Memory:: Searching memory for a sequence of bytes
8345 @section Expressions
8348 @code{print} and many other @value{GDBN} commands accept an expression and
8349 compute its value. Any kind of constant, variable or operator defined
8350 by the programming language you are using is valid in an expression in
8351 @value{GDBN}. This includes conditional expressions, function calls,
8352 casts, and string constants. It also includes preprocessor macros, if
8353 you compiled your program to include this information; see
8356 @cindex arrays in expressions
8357 @value{GDBN} supports array constants in expressions input by
8358 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8359 you can use the command @code{print @{1, 2, 3@}} to create an array
8360 of three integers. If you pass an array to a function or assign it
8361 to a program variable, @value{GDBN} copies the array to memory that
8362 is @code{malloc}ed in the target program.
8364 Because C is so widespread, most of the expressions shown in examples in
8365 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8366 Languages}, for information on how to use expressions in other
8369 In this section, we discuss operators that you can use in @value{GDBN}
8370 expressions regardless of your programming language.
8372 @cindex casts, in expressions
8373 Casts are supported in all languages, not just in C, because it is so
8374 useful to cast a number into a pointer in order to examine a structure
8375 at that address in memory.
8376 @c FIXME: casts supported---Mod2 true?
8378 @value{GDBN} supports these operators, in addition to those common
8379 to programming languages:
8383 @samp{@@} is a binary operator for treating parts of memory as arrays.
8384 @xref{Arrays, ,Artificial Arrays}, for more information.
8387 @samp{::} allows you to specify a variable in terms of the file or
8388 function where it is defined. @xref{Variables, ,Program Variables}.
8390 @cindex @{@var{type}@}
8391 @cindex type casting memory
8392 @cindex memory, viewing as typed object
8393 @cindex casts, to view memory
8394 @item @{@var{type}@} @var{addr}
8395 Refers to an object of type @var{type} stored at address @var{addr} in
8396 memory. The address @var{addr} may be any expression whose value is
8397 an integer or pointer (but parentheses are required around binary
8398 operators, just as in a cast). This construct is allowed regardless
8399 of what kind of data is normally supposed to reside at @var{addr}.
8402 @node Ambiguous Expressions
8403 @section Ambiguous Expressions
8404 @cindex ambiguous expressions
8406 Expressions can sometimes contain some ambiguous elements. For instance,
8407 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8408 a single function name to be defined several times, for application in
8409 different contexts. This is called @dfn{overloading}. Another example
8410 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8411 templates and is typically instantiated several times, resulting in
8412 the same function name being defined in different contexts.
8414 In some cases and depending on the language, it is possible to adjust
8415 the expression to remove the ambiguity. For instance in C@t{++}, you
8416 can specify the signature of the function you want to break on, as in
8417 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8418 qualified name of your function often makes the expression unambiguous
8421 When an ambiguity that needs to be resolved is detected, the debugger
8422 has the capability to display a menu of numbered choices for each
8423 possibility, and then waits for the selection with the prompt @samp{>}.
8424 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8425 aborts the current command. If the command in which the expression was
8426 used allows more than one choice to be selected, the next option in the
8427 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8430 For example, the following session excerpt shows an attempt to set a
8431 breakpoint at the overloaded symbol @code{String::after}.
8432 We choose three particular definitions of that function name:
8434 @c FIXME! This is likely to change to show arg type lists, at least
8437 (@value{GDBP}) b String::after
8440 [2] file:String.cc; line number:867
8441 [3] file:String.cc; line number:860
8442 [4] file:String.cc; line number:875
8443 [5] file:String.cc; line number:853
8444 [6] file:String.cc; line number:846
8445 [7] file:String.cc; line number:735
8447 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8448 Breakpoint 2 at 0xb344: file String.cc, line 875.
8449 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8450 Multiple breakpoints were set.
8451 Use the "delete" command to delete unwanted
8458 @kindex set multiple-symbols
8459 @item set multiple-symbols @var{mode}
8460 @cindex multiple-symbols menu
8462 This option allows you to adjust the debugger behavior when an expression
8465 By default, @var{mode} is set to @code{all}. If the command with which
8466 the expression is used allows more than one choice, then @value{GDBN}
8467 automatically selects all possible choices. For instance, inserting
8468 a breakpoint on a function using an ambiguous name results in a breakpoint
8469 inserted on each possible match. However, if a unique choice must be made,
8470 then @value{GDBN} uses the menu to help you disambiguate the expression.
8471 For instance, printing the address of an overloaded function will result
8472 in the use of the menu.
8474 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8475 when an ambiguity is detected.
8477 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8478 an error due to the ambiguity and the command is aborted.
8480 @kindex show multiple-symbols
8481 @item show multiple-symbols
8482 Show the current value of the @code{multiple-symbols} setting.
8486 @section Program Variables
8488 The most common kind of expression to use is the name of a variable
8491 Variables in expressions are understood in the selected stack frame
8492 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8496 global (or file-static)
8503 visible according to the scope rules of the
8504 programming language from the point of execution in that frame
8507 @noindent This means that in the function
8522 you can examine and use the variable @code{a} whenever your program is
8523 executing within the function @code{foo}, but you can only use or
8524 examine the variable @code{b} while your program is executing inside
8525 the block where @code{b} is declared.
8527 @cindex variable name conflict
8528 There is an exception: you can refer to a variable or function whose
8529 scope is a single source file even if the current execution point is not
8530 in this file. But it is possible to have more than one such variable or
8531 function with the same name (in different source files). If that
8532 happens, referring to that name has unpredictable effects. If you wish,
8533 you can specify a static variable in a particular function or file by
8534 using the colon-colon (@code{::}) notation:
8536 @cindex colon-colon, context for variables/functions
8538 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8539 @cindex @code{::}, context for variables/functions
8542 @var{file}::@var{variable}
8543 @var{function}::@var{variable}
8547 Here @var{file} or @var{function} is the name of the context for the
8548 static @var{variable}. In the case of file names, you can use quotes to
8549 make sure @value{GDBN} parses the file name as a single word---for example,
8550 to print a global value of @code{x} defined in @file{f2.c}:
8553 (@value{GDBP}) p 'f2.c'::x
8556 The @code{::} notation is normally used for referring to
8557 static variables, since you typically disambiguate uses of local variables
8558 in functions by selecting the appropriate frame and using the
8559 simple name of the variable. However, you may also use this notation
8560 to refer to local variables in frames enclosing the selected frame:
8569 process (a); /* Stop here */
8580 For example, if there is a breakpoint at the commented line,
8581 here is what you might see
8582 when the program stops after executing the call @code{bar(0)}:
8587 (@value{GDBP}) p bar::a
8590 #2 0x080483d0 in foo (a=5) at foobar.c:12
8593 (@value{GDBP}) p bar::a
8597 @cindex C@t{++} scope resolution
8598 These uses of @samp{::} are very rarely in conflict with the very
8599 similar use of the same notation in C@t{++}. When they are in
8600 conflict, the C@t{++} meaning takes precedence; however, this can be
8601 overridden by quoting the file or function name with single quotes.
8603 For example, suppose the program is stopped in a method of a class
8604 that has a field named @code{includefile}, and there is also an
8605 include file named @file{includefile} that defines a variable,
8609 (@value{GDBP}) p includefile
8611 (@value{GDBP}) p includefile::some_global
8612 A syntax error in expression, near `'.
8613 (@value{GDBP}) p 'includefile'::some_global
8617 @cindex wrong values
8618 @cindex variable values, wrong
8619 @cindex function entry/exit, wrong values of variables
8620 @cindex optimized code, wrong values of variables
8622 @emph{Warning:} Occasionally, a local variable may appear to have the
8623 wrong value at certain points in a function---just after entry to a new
8624 scope, and just before exit.
8626 You may see this problem when you are stepping by machine instructions.
8627 This is because, on most machines, it takes more than one instruction to
8628 set up a stack frame (including local variable definitions); if you are
8629 stepping by machine instructions, variables may appear to have the wrong
8630 values until the stack frame is completely built. On exit, it usually
8631 also takes more than one machine instruction to destroy a stack frame;
8632 after you begin stepping through that group of instructions, local
8633 variable definitions may be gone.
8635 This may also happen when the compiler does significant optimizations.
8636 To be sure of always seeing accurate values, turn off all optimization
8639 @cindex ``No symbol "foo" in current context''
8640 Another possible effect of compiler optimizations is to optimize
8641 unused variables out of existence, or assign variables to registers (as
8642 opposed to memory addresses). Depending on the support for such cases
8643 offered by the debug info format used by the compiler, @value{GDBN}
8644 might not be able to display values for such local variables. If that
8645 happens, @value{GDBN} will print a message like this:
8648 No symbol "foo" in current context.
8651 To solve such problems, either recompile without optimizations, or use a
8652 different debug info format, if the compiler supports several such
8653 formats. @xref{Compilation}, for more information on choosing compiler
8654 options. @xref{C, ,C and C@t{++}}, for more information about debug
8655 info formats that are best suited to C@t{++} programs.
8657 If you ask to print an object whose contents are unknown to
8658 @value{GDBN}, e.g., because its data type is not completely specified
8659 by the debug information, @value{GDBN} will say @samp{<incomplete
8660 type>}. @xref{Symbols, incomplete type}, for more about this.
8662 If you append @kbd{@@entry} string to a function parameter name you get its
8663 value at the time the function got called. If the value is not available an
8664 error message is printed. Entry values are available only with some compilers.
8665 Entry values are normally also printed at the function parameter list according
8666 to @ref{set print entry-values}.
8669 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8675 (gdb) print i@@entry
8679 Strings are identified as arrays of @code{char} values without specified
8680 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8681 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8682 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8683 defines literal string type @code{"char"} as @code{char} without a sign.
8688 signed char var1[] = "A";
8691 You get during debugging
8696 $2 = @{65 'A', 0 '\0'@}
8700 @section Artificial Arrays
8702 @cindex artificial array
8704 @kindex @@@r{, referencing memory as an array}
8705 It is often useful to print out several successive objects of the
8706 same type in memory; a section of an array, or an array of
8707 dynamically determined size for which only a pointer exists in the
8710 You can do this by referring to a contiguous span of memory as an
8711 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8712 operand of @samp{@@} should be the first element of the desired array
8713 and be an individual object. The right operand should be the desired length
8714 of the array. The result is an array value whose elements are all of
8715 the type of the left argument. The first element is actually the left
8716 argument; the second element comes from bytes of memory immediately
8717 following those that hold the first element, and so on. Here is an
8718 example. If a program says
8721 int *array = (int *) malloc (len * sizeof (int));
8725 you can print the contents of @code{array} with
8731 The left operand of @samp{@@} must reside in memory. Array values made
8732 with @samp{@@} in this way behave just like other arrays in terms of
8733 subscripting, and are coerced to pointers when used in expressions.
8734 Artificial arrays most often appear in expressions via the value history
8735 (@pxref{Value History, ,Value History}), after printing one out.
8737 Another way to create an artificial array is to use a cast.
8738 This re-interprets a value as if it were an array.
8739 The value need not be in memory:
8741 (@value{GDBP}) p/x (short[2])0x12345678
8742 $1 = @{0x1234, 0x5678@}
8745 As a convenience, if you leave the array length out (as in
8746 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8747 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8749 (@value{GDBP}) p/x (short[])0x12345678
8750 $2 = @{0x1234, 0x5678@}
8753 Sometimes the artificial array mechanism is not quite enough; in
8754 moderately complex data structures, the elements of interest may not
8755 actually be adjacent---for example, if you are interested in the values
8756 of pointers in an array. One useful work-around in this situation is
8757 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8758 Variables}) as a counter in an expression that prints the first
8759 interesting value, and then repeat that expression via @key{RET}. For
8760 instance, suppose you have an array @code{dtab} of pointers to
8761 structures, and you are interested in the values of a field @code{fv}
8762 in each structure. Here is an example of what you might type:
8772 @node Output Formats
8773 @section Output Formats
8775 @cindex formatted output
8776 @cindex output formats
8777 By default, @value{GDBN} prints a value according to its data type. Sometimes
8778 this is not what you want. For example, you might want to print a number
8779 in hex, or a pointer in decimal. Or you might want to view data in memory
8780 at a certain address as a character string or as an instruction. To do
8781 these things, specify an @dfn{output format} when you print a value.
8783 The simplest use of output formats is to say how to print a value
8784 already computed. This is done by starting the arguments of the
8785 @code{print} command with a slash and a format letter. The format
8786 letters supported are:
8790 Regard the bits of the value as an integer, and print the integer in
8794 Print as integer in signed decimal.
8797 Print as integer in unsigned decimal.
8800 Print as integer in octal.
8803 Print as integer in binary. The letter @samp{t} stands for ``two''.
8804 @footnote{@samp{b} cannot be used because these format letters are also
8805 used with the @code{x} command, where @samp{b} stands for ``byte'';
8806 see @ref{Memory,,Examining Memory}.}
8809 @cindex unknown address, locating
8810 @cindex locate address
8811 Print as an address, both absolute in hexadecimal and as an offset from
8812 the nearest preceding symbol. You can use this format used to discover
8813 where (in what function) an unknown address is located:
8816 (@value{GDBP}) p/a 0x54320
8817 $3 = 0x54320 <_initialize_vx+396>
8821 The command @code{info symbol 0x54320} yields similar results.
8822 @xref{Symbols, info symbol}.
8825 Regard as an integer and print it as a character constant. This
8826 prints both the numerical value and its character representation. The
8827 character representation is replaced with the octal escape @samp{\nnn}
8828 for characters outside the 7-bit @sc{ascii} range.
8830 Without this format, @value{GDBN} displays @code{char},
8831 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8832 constants. Single-byte members of vectors are displayed as integer
8836 Regard the bits of the value as a floating point number and print
8837 using typical floating point syntax.
8840 @cindex printing strings
8841 @cindex printing byte arrays
8842 Regard as a string, if possible. With this format, pointers to single-byte
8843 data are displayed as null-terminated strings and arrays of single-byte data
8844 are displayed as fixed-length strings. Other values are displayed in their
8847 Without this format, @value{GDBN} displays pointers to and arrays of
8848 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8849 strings. Single-byte members of a vector are displayed as an integer
8853 Like @samp{x} formatting, the value is treated as an integer and
8854 printed as hexadecimal, but leading zeros are printed to pad the value
8855 to the size of the integer type.
8858 @cindex raw printing
8859 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8860 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8861 Printing}). This typically results in a higher-level display of the
8862 value's contents. The @samp{r} format bypasses any Python
8863 pretty-printer which might exist.
8866 For example, to print the program counter in hex (@pxref{Registers}), type
8873 Note that no space is required before the slash; this is because command
8874 names in @value{GDBN} cannot contain a slash.
8876 To reprint the last value in the value history with a different format,
8877 you can use the @code{print} command with just a format and no
8878 expression. For example, @samp{p/x} reprints the last value in hex.
8881 @section Examining Memory
8883 You can use the command @code{x} (for ``examine'') to examine memory in
8884 any of several formats, independently of your program's data types.
8886 @cindex examining memory
8888 @kindex x @r{(examine memory)}
8889 @item x/@var{nfu} @var{addr}
8892 Use the @code{x} command to examine memory.
8895 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8896 much memory to display and how to format it; @var{addr} is an
8897 expression giving the address where you want to start displaying memory.
8898 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8899 Several commands set convenient defaults for @var{addr}.
8902 @item @var{n}, the repeat count
8903 The repeat count is a decimal integer; the default is 1. It specifies
8904 how much memory (counting by units @var{u}) to display.
8905 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8908 @item @var{f}, the display format
8909 The display format is one of the formats used by @code{print}
8910 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8911 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8912 The default is @samp{x} (hexadecimal) initially. The default changes
8913 each time you use either @code{x} or @code{print}.
8915 @item @var{u}, the unit size
8916 The unit size is any of
8922 Halfwords (two bytes).
8924 Words (four bytes). This is the initial default.
8926 Giant words (eight bytes).
8929 Each time you specify a unit size with @code{x}, that size becomes the
8930 default unit the next time you use @code{x}. For the @samp{i} format,
8931 the unit size is ignored and is normally not written. For the @samp{s} format,
8932 the unit size defaults to @samp{b}, unless it is explicitly given.
8933 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8934 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8935 Note that the results depend on the programming language of the
8936 current compilation unit. If the language is C, the @samp{s}
8937 modifier will use the UTF-16 encoding while @samp{w} will use
8938 UTF-32. The encoding is set by the programming language and cannot
8941 @item @var{addr}, starting display address
8942 @var{addr} is the address where you want @value{GDBN} to begin displaying
8943 memory. The expression need not have a pointer value (though it may);
8944 it is always interpreted as an integer address of a byte of memory.
8945 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8946 @var{addr} is usually just after the last address examined---but several
8947 other commands also set the default address: @code{info breakpoints} (to
8948 the address of the last breakpoint listed), @code{info line} (to the
8949 starting address of a line), and @code{print} (if you use it to display
8950 a value from memory).
8953 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8954 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8955 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8956 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8957 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8959 Since the letters indicating unit sizes are all distinct from the
8960 letters specifying output formats, you do not have to remember whether
8961 unit size or format comes first; either order works. The output
8962 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8963 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8965 Even though the unit size @var{u} is ignored for the formats @samp{s}
8966 and @samp{i}, you might still want to use a count @var{n}; for example,
8967 @samp{3i} specifies that you want to see three machine instructions,
8968 including any operands. For convenience, especially when used with
8969 the @code{display} command, the @samp{i} format also prints branch delay
8970 slot instructions, if any, beyond the count specified, which immediately
8971 follow the last instruction that is within the count. The command
8972 @code{disassemble} gives an alternative way of inspecting machine
8973 instructions; see @ref{Machine Code,,Source and Machine Code}.
8975 All the defaults for the arguments to @code{x} are designed to make it
8976 easy to continue scanning memory with minimal specifications each time
8977 you use @code{x}. For example, after you have inspected three machine
8978 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8979 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8980 the repeat count @var{n} is used again; the other arguments default as
8981 for successive uses of @code{x}.
8983 When examining machine instructions, the instruction at current program
8984 counter is shown with a @code{=>} marker. For example:
8987 (@value{GDBP}) x/5i $pc-6
8988 0x804837f <main+11>: mov %esp,%ebp
8989 0x8048381 <main+13>: push %ecx
8990 0x8048382 <main+14>: sub $0x4,%esp
8991 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8992 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8995 @cindex @code{$_}, @code{$__}, and value history
8996 The addresses and contents printed by the @code{x} command are not saved
8997 in the value history because there is often too much of them and they
8998 would get in the way. Instead, @value{GDBN} makes these values available for
8999 subsequent use in expressions as values of the convenience variables
9000 @code{$_} and @code{$__}. After an @code{x} command, the last address
9001 examined is available for use in expressions in the convenience variable
9002 @code{$_}. The contents of that address, as examined, are available in
9003 the convenience variable @code{$__}.
9005 If the @code{x} command has a repeat count, the address and contents saved
9006 are from the last memory unit printed; this is not the same as the last
9007 address printed if several units were printed on the last line of output.
9009 @cindex remote memory comparison
9010 @cindex target memory comparison
9011 @cindex verify remote memory image
9012 @cindex verify target memory image
9013 When you are debugging a program running on a remote target machine
9014 (@pxref{Remote Debugging}), you may wish to verify the program's image
9015 in the remote machine's memory against the executable file you
9016 downloaded to the target. Or, on any target, you may want to check
9017 whether the program has corrupted its own read-only sections. The
9018 @code{compare-sections} command is provided for such situations.
9021 @kindex compare-sections
9022 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9023 Compare the data of a loadable section @var{section-name} in the
9024 executable file of the program being debugged with the same section in
9025 the target machine's memory, and report any mismatches. With no
9026 arguments, compares all loadable sections. With an argument of
9027 @code{-r}, compares all loadable read-only sections.
9029 Note: for remote targets, this command can be accelerated if the
9030 target supports computing the CRC checksum of a block of memory
9031 (@pxref{qCRC packet}).
9035 @section Automatic Display
9036 @cindex automatic display
9037 @cindex display of expressions
9039 If you find that you want to print the value of an expression frequently
9040 (to see how it changes), you might want to add it to the @dfn{automatic
9041 display list} so that @value{GDBN} prints its value each time your program stops.
9042 Each expression added to the list is given a number to identify it;
9043 to remove an expression from the list, you specify that number.
9044 The automatic display looks like this:
9048 3: bar[5] = (struct hack *) 0x3804
9052 This display shows item numbers, expressions and their current values. As with
9053 displays you request manually using @code{x} or @code{print}, you can
9054 specify the output format you prefer; in fact, @code{display} decides
9055 whether to use @code{print} or @code{x} depending your format
9056 specification---it uses @code{x} if you specify either the @samp{i}
9057 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9061 @item display @var{expr}
9062 Add the expression @var{expr} to the list of expressions to display
9063 each time your program stops. @xref{Expressions, ,Expressions}.
9065 @code{display} does not repeat if you press @key{RET} again after using it.
9067 @item display/@var{fmt} @var{expr}
9068 For @var{fmt} specifying only a display format and not a size or
9069 count, add the expression @var{expr} to the auto-display list but
9070 arrange to display it each time in the specified format @var{fmt}.
9071 @xref{Output Formats,,Output Formats}.
9073 @item display/@var{fmt} @var{addr}
9074 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9075 number of units, add the expression @var{addr} as a memory address to
9076 be examined each time your program stops. Examining means in effect
9077 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9080 For example, @samp{display/i $pc} can be helpful, to see the machine
9081 instruction about to be executed each time execution stops (@samp{$pc}
9082 is a common name for the program counter; @pxref{Registers, ,Registers}).
9085 @kindex delete display
9087 @item undisplay @var{dnums}@dots{}
9088 @itemx delete display @var{dnums}@dots{}
9089 Remove items from the list of expressions to display. Specify the
9090 numbers of the displays that you want affected with the command
9091 argument @var{dnums}. It can be a single display number, one of the
9092 numbers shown in the first field of the @samp{info display} display;
9093 or it could be a range of display numbers, as in @code{2-4}.
9095 @code{undisplay} does not repeat if you press @key{RET} after using it.
9096 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9098 @kindex disable display
9099 @item disable display @var{dnums}@dots{}
9100 Disable the display of item numbers @var{dnums}. A disabled display
9101 item is not printed automatically, but is not forgotten. It may be
9102 enabled again later. Specify the numbers of the displays that you
9103 want affected with the command argument @var{dnums}. It can be a
9104 single display number, one of the numbers shown in the first field of
9105 the @samp{info display} display; or it could be a range of display
9106 numbers, as in @code{2-4}.
9108 @kindex enable display
9109 @item enable display @var{dnums}@dots{}
9110 Enable display of item numbers @var{dnums}. It becomes effective once
9111 again in auto display of its expression, until you specify otherwise.
9112 Specify the numbers of the displays that you want affected with the
9113 command argument @var{dnums}. It can be a single display number, one
9114 of the numbers shown in the first field of the @samp{info display}
9115 display; or it could be a range of display numbers, as in @code{2-4}.
9118 Display the current values of the expressions on the list, just as is
9119 done when your program stops.
9121 @kindex info display
9123 Print the list of expressions previously set up to display
9124 automatically, each one with its item number, but without showing the
9125 values. This includes disabled expressions, which are marked as such.
9126 It also includes expressions which would not be displayed right now
9127 because they refer to automatic variables not currently available.
9130 @cindex display disabled out of scope
9131 If a display expression refers to local variables, then it does not make
9132 sense outside the lexical context for which it was set up. Such an
9133 expression is disabled when execution enters a context where one of its
9134 variables is not defined. For example, if you give the command
9135 @code{display last_char} while inside a function with an argument
9136 @code{last_char}, @value{GDBN} displays this argument while your program
9137 continues to stop inside that function. When it stops elsewhere---where
9138 there is no variable @code{last_char}---the display is disabled
9139 automatically. The next time your program stops where @code{last_char}
9140 is meaningful, you can enable the display expression once again.
9142 @node Print Settings
9143 @section Print Settings
9145 @cindex format options
9146 @cindex print settings
9147 @value{GDBN} provides the following ways to control how arrays, structures,
9148 and symbols are printed.
9151 These settings are useful for debugging programs in any language:
9155 @item set print address
9156 @itemx set print address on
9157 @cindex print/don't print memory addresses
9158 @value{GDBN} prints memory addresses showing the location of stack
9159 traces, structure values, pointer values, breakpoints, and so forth,
9160 even when it also displays the contents of those addresses. The default
9161 is @code{on}. For example, this is what a stack frame display looks like with
9162 @code{set print address on}:
9167 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9169 530 if (lquote != def_lquote)
9173 @item set print address off
9174 Do not print addresses when displaying their contents. For example,
9175 this is the same stack frame displayed with @code{set print address off}:
9179 (@value{GDBP}) set print addr off
9181 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9182 530 if (lquote != def_lquote)
9186 You can use @samp{set print address off} to eliminate all machine
9187 dependent displays from the @value{GDBN} interface. For example, with
9188 @code{print address off}, you should get the same text for backtraces on
9189 all machines---whether or not they involve pointer arguments.
9192 @item show print address
9193 Show whether or not addresses are to be printed.
9196 When @value{GDBN} prints a symbolic address, it normally prints the
9197 closest earlier symbol plus an offset. If that symbol does not uniquely
9198 identify the address (for example, it is a name whose scope is a single
9199 source file), you may need to clarify. One way to do this is with
9200 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9201 you can set @value{GDBN} to print the source file and line number when
9202 it prints a symbolic address:
9205 @item set print symbol-filename on
9206 @cindex source file and line of a symbol
9207 @cindex symbol, source file and line
9208 Tell @value{GDBN} to print the source file name and line number of a
9209 symbol in the symbolic form of an address.
9211 @item set print symbol-filename off
9212 Do not print source file name and line number of a symbol. This is the
9215 @item show print symbol-filename
9216 Show whether or not @value{GDBN} will print the source file name and
9217 line number of a symbol in the symbolic form of an address.
9220 Another situation where it is helpful to show symbol filenames and line
9221 numbers is when disassembling code; @value{GDBN} shows you the line
9222 number and source file that corresponds to each instruction.
9224 Also, you may wish to see the symbolic form only if the address being
9225 printed is reasonably close to the closest earlier symbol:
9228 @item set print max-symbolic-offset @var{max-offset}
9229 @itemx set print max-symbolic-offset unlimited
9230 @cindex maximum value for offset of closest symbol
9231 Tell @value{GDBN} to only display the symbolic form of an address if the
9232 offset between the closest earlier symbol and the address is less than
9233 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9234 to always print the symbolic form of an address if any symbol precedes
9235 it. Zero is equivalent to @code{unlimited}.
9237 @item show print max-symbolic-offset
9238 Ask how large the maximum offset is that @value{GDBN} prints in a
9242 @cindex wild pointer, interpreting
9243 @cindex pointer, finding referent
9244 If you have a pointer and you are not sure where it points, try
9245 @samp{set print symbol-filename on}. Then you can determine the name
9246 and source file location of the variable where it points, using
9247 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9248 For example, here @value{GDBN} shows that a variable @code{ptt} points
9249 at another variable @code{t}, defined in @file{hi2.c}:
9252 (@value{GDBP}) set print symbol-filename on
9253 (@value{GDBP}) p/a ptt
9254 $4 = 0xe008 <t in hi2.c>
9258 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9259 does not show the symbol name and filename of the referent, even with
9260 the appropriate @code{set print} options turned on.
9263 You can also enable @samp{/a}-like formatting all the time using
9264 @samp{set print symbol on}:
9267 @item set print symbol on
9268 Tell @value{GDBN} to print the symbol corresponding to an address, if
9271 @item set print symbol off
9272 Tell @value{GDBN} not to print the symbol corresponding to an
9273 address. In this mode, @value{GDBN} will still print the symbol
9274 corresponding to pointers to functions. This is the default.
9276 @item show print symbol
9277 Show whether @value{GDBN} will display the symbol corresponding to an
9281 Other settings control how different kinds of objects are printed:
9284 @item set print array
9285 @itemx set print array on
9286 @cindex pretty print arrays
9287 Pretty print arrays. This format is more convenient to read,
9288 but uses more space. The default is off.
9290 @item set print array off
9291 Return to compressed format for arrays.
9293 @item show print array
9294 Show whether compressed or pretty format is selected for displaying
9297 @cindex print array indexes
9298 @item set print array-indexes
9299 @itemx set print array-indexes on
9300 Print the index of each element when displaying arrays. May be more
9301 convenient to locate a given element in the array or quickly find the
9302 index of a given element in that printed array. The default is off.
9304 @item set print array-indexes off
9305 Stop printing element indexes when displaying arrays.
9307 @item show print array-indexes
9308 Show whether the index of each element is printed when displaying
9311 @item set print elements @var{number-of-elements}
9312 @itemx set print elements unlimited
9313 @cindex number of array elements to print
9314 @cindex limit on number of printed array elements
9315 Set a limit on how many elements of an array @value{GDBN} will print.
9316 If @value{GDBN} is printing a large array, it stops printing after it has
9317 printed the number of elements set by the @code{set print elements} command.
9318 This limit also applies to the display of strings.
9319 When @value{GDBN} starts, this limit is set to 200.
9320 Setting @var{number-of-elements} to @code{unlimited} or zero means
9321 that the number of elements to print is unlimited.
9323 @item show print elements
9324 Display the number of elements of a large array that @value{GDBN} will print.
9325 If the number is 0, then the printing is unlimited.
9327 @item set print frame-arguments @var{value}
9328 @kindex set print frame-arguments
9329 @cindex printing frame argument values
9330 @cindex print all frame argument values
9331 @cindex print frame argument values for scalars only
9332 @cindex do not print frame argument values
9333 This command allows to control how the values of arguments are printed
9334 when the debugger prints a frame (@pxref{Frames}). The possible
9339 The values of all arguments are printed.
9342 Print the value of an argument only if it is a scalar. The value of more
9343 complex arguments such as arrays, structures, unions, etc, is replaced
9344 by @code{@dots{}}. This is the default. Here is an example where
9345 only scalar arguments are shown:
9348 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9353 None of the argument values are printed. Instead, the value of each argument
9354 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9357 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9362 By default, only scalar arguments are printed. This command can be used
9363 to configure the debugger to print the value of all arguments, regardless
9364 of their type. However, it is often advantageous to not print the value
9365 of more complex parameters. For instance, it reduces the amount of
9366 information printed in each frame, making the backtrace more readable.
9367 Also, it improves performance when displaying Ada frames, because
9368 the computation of large arguments can sometimes be CPU-intensive,
9369 especially in large applications. Setting @code{print frame-arguments}
9370 to @code{scalars} (the default) or @code{none} avoids this computation,
9371 thus speeding up the display of each Ada frame.
9373 @item show print frame-arguments
9374 Show how the value of arguments should be displayed when printing a frame.
9376 @item set print raw frame-arguments on
9377 Print frame arguments in raw, non pretty-printed, form.
9379 @item set print raw frame-arguments off
9380 Print frame arguments in pretty-printed form, if there is a pretty-printer
9381 for the value (@pxref{Pretty Printing}),
9382 otherwise print the value in raw form.
9383 This is the default.
9385 @item show print raw frame-arguments
9386 Show whether to print frame arguments in raw form.
9388 @anchor{set print entry-values}
9389 @item set print entry-values @var{value}
9390 @kindex set print entry-values
9391 Set printing of frame argument values at function entry. In some cases
9392 @value{GDBN} can determine the value of function argument which was passed by
9393 the function caller, even if the value was modified inside the called function
9394 and therefore is different. With optimized code, the current value could be
9395 unavailable, but the entry value may still be known.
9397 The default value is @code{default} (see below for its description). Older
9398 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9399 this feature will behave in the @code{default} setting the same way as with the
9402 This functionality is currently supported only by DWARF 2 debugging format and
9403 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9404 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9407 The @var{value} parameter can be one of the following:
9411 Print only actual parameter values, never print values from function entry
9415 #0 different (val=6)
9416 #0 lost (val=<optimized out>)
9418 #0 invalid (val=<optimized out>)
9422 Print only parameter values from function entry point. The actual parameter
9423 values are never printed.
9425 #0 equal (val@@entry=5)
9426 #0 different (val@@entry=5)
9427 #0 lost (val@@entry=5)
9428 #0 born (val@@entry=<optimized out>)
9429 #0 invalid (val@@entry=<optimized out>)
9433 Print only parameter values from function entry point. If value from function
9434 entry point is not known while the actual value is known, print the actual
9435 value for such parameter.
9437 #0 equal (val@@entry=5)
9438 #0 different (val@@entry=5)
9439 #0 lost (val@@entry=5)
9441 #0 invalid (val@@entry=<optimized out>)
9445 Print actual parameter values. If actual parameter value is not known while
9446 value from function entry point is known, print the entry point value for such
9450 #0 different (val=6)
9451 #0 lost (val@@entry=5)
9453 #0 invalid (val=<optimized out>)
9457 Always print both the actual parameter value and its value from function entry
9458 point, even if values of one or both are not available due to compiler
9461 #0 equal (val=5, val@@entry=5)
9462 #0 different (val=6, val@@entry=5)
9463 #0 lost (val=<optimized out>, val@@entry=5)
9464 #0 born (val=10, val@@entry=<optimized out>)
9465 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9469 Print the actual parameter value if it is known and also its value from
9470 function entry point if it is known. If neither is known, print for the actual
9471 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9472 values are known and identical, print the shortened
9473 @code{param=param@@entry=VALUE} notation.
9475 #0 equal (val=val@@entry=5)
9476 #0 different (val=6, val@@entry=5)
9477 #0 lost (val@@entry=5)
9479 #0 invalid (val=<optimized out>)
9483 Always print the actual parameter value. Print also its value from function
9484 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9485 if both values are known and identical, print the shortened
9486 @code{param=param@@entry=VALUE} notation.
9488 #0 equal (val=val@@entry=5)
9489 #0 different (val=6, val@@entry=5)
9490 #0 lost (val=<optimized out>, val@@entry=5)
9492 #0 invalid (val=<optimized out>)
9496 For analysis messages on possible failures of frame argument values at function
9497 entry resolution see @ref{set debug entry-values}.
9499 @item show print entry-values
9500 Show the method being used for printing of frame argument values at function
9503 @item set print repeats @var{number-of-repeats}
9504 @itemx set print repeats unlimited
9505 @cindex repeated array elements
9506 Set the threshold for suppressing display of repeated array
9507 elements. When the number of consecutive identical elements of an
9508 array exceeds the threshold, @value{GDBN} prints the string
9509 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9510 identical repetitions, instead of displaying the identical elements
9511 themselves. Setting the threshold to @code{unlimited} or zero will
9512 cause all elements to be individually printed. The default threshold
9515 @item show print repeats
9516 Display the current threshold for printing repeated identical
9519 @item set print null-stop
9520 @cindex @sc{null} elements in arrays
9521 Cause @value{GDBN} to stop printing the characters of an array when the first
9522 @sc{null} is encountered. This is useful when large arrays actually
9523 contain only short strings.
9526 @item show print null-stop
9527 Show whether @value{GDBN} stops printing an array on the first
9528 @sc{null} character.
9530 @item set print pretty on
9531 @cindex print structures in indented form
9532 @cindex indentation in structure display
9533 Cause @value{GDBN} to print structures in an indented format with one member
9534 per line, like this:
9549 @item set print pretty off
9550 Cause @value{GDBN} to print structures in a compact format, like this:
9554 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9555 meat = 0x54 "Pork"@}
9560 This is the default format.
9562 @item show print pretty
9563 Show which format @value{GDBN} is using to print structures.
9565 @item set print sevenbit-strings on
9566 @cindex eight-bit characters in strings
9567 @cindex octal escapes in strings
9568 Print using only seven-bit characters; if this option is set,
9569 @value{GDBN} displays any eight-bit characters (in strings or
9570 character values) using the notation @code{\}@var{nnn}. This setting is
9571 best if you are working in English (@sc{ascii}) and you use the
9572 high-order bit of characters as a marker or ``meta'' bit.
9574 @item set print sevenbit-strings off
9575 Print full eight-bit characters. This allows the use of more
9576 international character sets, and is the default.
9578 @item show print sevenbit-strings
9579 Show whether or not @value{GDBN} is printing only seven-bit characters.
9581 @item set print union on
9582 @cindex unions in structures, printing
9583 Tell @value{GDBN} to print unions which are contained in structures
9584 and other unions. This is the default setting.
9586 @item set print union off
9587 Tell @value{GDBN} not to print unions which are contained in
9588 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9591 @item show print union
9592 Ask @value{GDBN} whether or not it will print unions which are contained in
9593 structures and other unions.
9595 For example, given the declarations
9598 typedef enum @{Tree, Bug@} Species;
9599 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9600 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9611 struct thing foo = @{Tree, @{Acorn@}@};
9615 with @code{set print union on} in effect @samp{p foo} would print
9618 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9622 and with @code{set print union off} in effect it would print
9625 $1 = @{it = Tree, form = @{...@}@}
9629 @code{set print union} affects programs written in C-like languages
9635 These settings are of interest when debugging C@t{++} programs:
9638 @cindex demangling C@t{++} names
9639 @item set print demangle
9640 @itemx set print demangle on
9641 Print C@t{++} names in their source form rather than in the encoded
9642 (``mangled'') form passed to the assembler and linker for type-safe
9643 linkage. The default is on.
9645 @item show print demangle
9646 Show whether C@t{++} names are printed in mangled or demangled form.
9648 @item set print asm-demangle
9649 @itemx set print asm-demangle on
9650 Print C@t{++} names in their source form rather than their mangled form, even
9651 in assembler code printouts such as instruction disassemblies.
9654 @item show print asm-demangle
9655 Show whether C@t{++} names in assembly listings are printed in mangled
9658 @cindex C@t{++} symbol decoding style
9659 @cindex symbol decoding style, C@t{++}
9660 @kindex set demangle-style
9661 @item set demangle-style @var{style}
9662 Choose among several encoding schemes used by different compilers to
9663 represent C@t{++} names. The choices for @var{style} are currently:
9667 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9668 This is the default.
9671 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9674 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9677 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9680 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9681 @strong{Warning:} this setting alone is not sufficient to allow
9682 debugging @code{cfront}-generated executables. @value{GDBN} would
9683 require further enhancement to permit that.
9686 If you omit @var{style}, you will see a list of possible formats.
9688 @item show demangle-style
9689 Display the encoding style currently in use for decoding C@t{++} symbols.
9691 @item set print object
9692 @itemx set print object on
9693 @cindex derived type of an object, printing
9694 @cindex display derived types
9695 When displaying a pointer to an object, identify the @emph{actual}
9696 (derived) type of the object rather than the @emph{declared} type, using
9697 the virtual function table. Note that the virtual function table is
9698 required---this feature can only work for objects that have run-time
9699 type identification; a single virtual method in the object's declared
9700 type is sufficient. Note that this setting is also taken into account when
9701 working with variable objects via MI (@pxref{GDB/MI}).
9703 @item set print object off
9704 Display only the declared type of objects, without reference to the
9705 virtual function table. This is the default setting.
9707 @item show print object
9708 Show whether actual, or declared, object types are displayed.
9710 @item set print static-members
9711 @itemx set print static-members on
9712 @cindex static members of C@t{++} objects
9713 Print static members when displaying a C@t{++} object. The default is on.
9715 @item set print static-members off
9716 Do not print static members when displaying a C@t{++} object.
9718 @item show print static-members
9719 Show whether C@t{++} static members are printed or not.
9721 @item set print pascal_static-members
9722 @itemx set print pascal_static-members on
9723 @cindex static members of Pascal objects
9724 @cindex Pascal objects, static members display
9725 Print static members when displaying a Pascal object. The default is on.
9727 @item set print pascal_static-members off
9728 Do not print static members when displaying a Pascal object.
9730 @item show print pascal_static-members
9731 Show whether Pascal static members are printed or not.
9733 @c These don't work with HP ANSI C++ yet.
9734 @item set print vtbl
9735 @itemx set print vtbl on
9736 @cindex pretty print C@t{++} virtual function tables
9737 @cindex virtual functions (C@t{++}) display
9738 @cindex VTBL display
9739 Pretty print C@t{++} virtual function tables. The default is off.
9740 (The @code{vtbl} commands do not work on programs compiled with the HP
9741 ANSI C@t{++} compiler (@code{aCC}).)
9743 @item set print vtbl off
9744 Do not pretty print C@t{++} virtual function tables.
9746 @item show print vtbl
9747 Show whether C@t{++} virtual function tables are pretty printed, or not.
9750 @node Pretty Printing
9751 @section Pretty Printing
9753 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9754 Python code. It greatly simplifies the display of complex objects. This
9755 mechanism works for both MI and the CLI.
9758 * Pretty-Printer Introduction:: Introduction to pretty-printers
9759 * Pretty-Printer Example:: An example pretty-printer
9760 * Pretty-Printer Commands:: Pretty-printer commands
9763 @node Pretty-Printer Introduction
9764 @subsection Pretty-Printer Introduction
9766 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9767 registered for the value. If there is then @value{GDBN} invokes the
9768 pretty-printer to print the value. Otherwise the value is printed normally.
9770 Pretty-printers are normally named. This makes them easy to manage.
9771 The @samp{info pretty-printer} command will list all the installed
9772 pretty-printers with their names.
9773 If a pretty-printer can handle multiple data types, then its
9774 @dfn{subprinters} are the printers for the individual data types.
9775 Each such subprinter has its own name.
9776 The format of the name is @var{printer-name};@var{subprinter-name}.
9778 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9779 Typically they are automatically loaded and registered when the corresponding
9780 debug information is loaded, thus making them available without having to
9781 do anything special.
9783 There are three places where a pretty-printer can be registered.
9787 Pretty-printers registered globally are available when debugging
9791 Pretty-printers registered with a program space are available only
9792 when debugging that program.
9793 @xref{Progspaces In Python}, for more details on program spaces in Python.
9796 Pretty-printers registered with an objfile are loaded and unloaded
9797 with the corresponding objfile (e.g., shared library).
9798 @xref{Objfiles In Python}, for more details on objfiles in Python.
9801 @xref{Selecting Pretty-Printers}, for further information on how
9802 pretty-printers are selected,
9804 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9807 @node Pretty-Printer Example
9808 @subsection Pretty-Printer Example
9810 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9813 (@value{GDBP}) print s
9815 static npos = 4294967295,
9817 <std::allocator<char>> = @{
9818 <__gnu_cxx::new_allocator<char>> = @{
9819 <No data fields>@}, <No data fields>
9821 members of std::basic_string<char, std::char_traits<char>,
9822 std::allocator<char> >::_Alloc_hider:
9823 _M_p = 0x804a014 "abcd"
9828 With a pretty-printer for @code{std::string} only the contents are printed:
9831 (@value{GDBP}) print s
9835 @node Pretty-Printer Commands
9836 @subsection Pretty-Printer Commands
9837 @cindex pretty-printer commands
9840 @kindex info pretty-printer
9841 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9842 Print the list of installed pretty-printers.
9843 This includes disabled pretty-printers, which are marked as such.
9845 @var{object-regexp} is a regular expression matching the objects
9846 whose pretty-printers to list.
9847 Objects can be @code{global}, the program space's file
9848 (@pxref{Progspaces In Python}),
9849 and the object files within that program space (@pxref{Objfiles In Python}).
9850 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9851 looks up a printer from these three objects.
9853 @var{name-regexp} is a regular expression matching the name of the printers
9856 @kindex disable pretty-printer
9857 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9858 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9859 A disabled pretty-printer is not forgotten, it may be enabled again later.
9861 @kindex enable pretty-printer
9862 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9863 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9868 Suppose we have three pretty-printers installed: one from library1.so
9869 named @code{foo} that prints objects of type @code{foo}, and
9870 another from library2.so named @code{bar} that prints two types of objects,
9871 @code{bar1} and @code{bar2}.
9874 (gdb) info pretty-printer
9881 (gdb) info pretty-printer library2
9886 (gdb) disable pretty-printer library1
9888 2 of 3 printers enabled
9889 (gdb) info pretty-printer
9896 (gdb) disable pretty-printer library2 bar:bar1
9898 1 of 3 printers enabled
9899 (gdb) info pretty-printer library2
9906 (gdb) disable pretty-printer library2 bar
9908 0 of 3 printers enabled
9909 (gdb) info pretty-printer library2
9918 Note that for @code{bar} the entire printer can be disabled,
9919 as can each individual subprinter.
9922 @section Value History
9924 @cindex value history
9925 @cindex history of values printed by @value{GDBN}
9926 Values printed by the @code{print} command are saved in the @value{GDBN}
9927 @dfn{value history}. This allows you to refer to them in other expressions.
9928 Values are kept until the symbol table is re-read or discarded
9929 (for example with the @code{file} or @code{symbol-file} commands).
9930 When the symbol table changes, the value history is discarded,
9931 since the values may contain pointers back to the types defined in the
9936 @cindex history number
9937 The values printed are given @dfn{history numbers} by which you can
9938 refer to them. These are successive integers starting with one.
9939 @code{print} shows you the history number assigned to a value by
9940 printing @samp{$@var{num} = } before the value; here @var{num} is the
9943 To refer to any previous value, use @samp{$} followed by the value's
9944 history number. The way @code{print} labels its output is designed to
9945 remind you of this. Just @code{$} refers to the most recent value in
9946 the history, and @code{$$} refers to the value before that.
9947 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9948 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9949 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9951 For example, suppose you have just printed a pointer to a structure and
9952 want to see the contents of the structure. It suffices to type
9958 If you have a chain of structures where the component @code{next} points
9959 to the next one, you can print the contents of the next one with this:
9966 You can print successive links in the chain by repeating this
9967 command---which you can do by just typing @key{RET}.
9969 Note that the history records values, not expressions. If the value of
9970 @code{x} is 4 and you type these commands:
9978 then the value recorded in the value history by the @code{print} command
9979 remains 4 even though the value of @code{x} has changed.
9984 Print the last ten values in the value history, with their item numbers.
9985 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9986 values} does not change the history.
9988 @item show values @var{n}
9989 Print ten history values centered on history item number @var{n}.
9992 Print ten history values just after the values last printed. If no more
9993 values are available, @code{show values +} produces no display.
9996 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9997 same effect as @samp{show values +}.
9999 @node Convenience Vars
10000 @section Convenience Variables
10002 @cindex convenience variables
10003 @cindex user-defined variables
10004 @value{GDBN} provides @dfn{convenience variables} that you can use within
10005 @value{GDBN} to hold on to a value and refer to it later. These variables
10006 exist entirely within @value{GDBN}; they are not part of your program, and
10007 setting a convenience variable has no direct effect on further execution
10008 of your program. That is why you can use them freely.
10010 Convenience variables are prefixed with @samp{$}. Any name preceded by
10011 @samp{$} can be used for a convenience variable, unless it is one of
10012 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10013 (Value history references, in contrast, are @emph{numbers} preceded
10014 by @samp{$}. @xref{Value History, ,Value History}.)
10016 You can save a value in a convenience variable with an assignment
10017 expression, just as you would set a variable in your program.
10021 set $foo = *object_ptr
10025 would save in @code{$foo} the value contained in the object pointed to by
10028 Using a convenience variable for the first time creates it, but its
10029 value is @code{void} until you assign a new value. You can alter the
10030 value with another assignment at any time.
10032 Convenience variables have no fixed types. You can assign a convenience
10033 variable any type of value, including structures and arrays, even if
10034 that variable already has a value of a different type. The convenience
10035 variable, when used as an expression, has the type of its current value.
10038 @kindex show convenience
10039 @cindex show all user variables and functions
10040 @item show convenience
10041 Print a list of convenience variables used so far, and their values,
10042 as well as a list of the convenience functions.
10043 Abbreviated @code{show conv}.
10045 @kindex init-if-undefined
10046 @cindex convenience variables, initializing
10047 @item init-if-undefined $@var{variable} = @var{expression}
10048 Set a convenience variable if it has not already been set. This is useful
10049 for user-defined commands that keep some state. It is similar, in concept,
10050 to using local static variables with initializers in C (except that
10051 convenience variables are global). It can also be used to allow users to
10052 override default values used in a command script.
10054 If the variable is already defined then the expression is not evaluated so
10055 any side-effects do not occur.
10058 One of the ways to use a convenience variable is as a counter to be
10059 incremented or a pointer to be advanced. For example, to print
10060 a field from successive elements of an array of structures:
10064 print bar[$i++]->contents
10068 Repeat that command by typing @key{RET}.
10070 Some convenience variables are created automatically by @value{GDBN} and given
10071 values likely to be useful.
10074 @vindex $_@r{, convenience variable}
10076 The variable @code{$_} is automatically set by the @code{x} command to
10077 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10078 commands which provide a default address for @code{x} to examine also
10079 set @code{$_} to that address; these commands include @code{info line}
10080 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10081 except when set by the @code{x} command, in which case it is a pointer
10082 to the type of @code{$__}.
10084 @vindex $__@r{, convenience variable}
10086 The variable @code{$__} is automatically set by the @code{x} command
10087 to the value found in the last address examined. Its type is chosen
10088 to match the format in which the data was printed.
10091 @vindex $_exitcode@r{, convenience variable}
10092 When the program being debugged terminates normally, @value{GDBN}
10093 automatically sets this variable to the exit code of the program, and
10094 resets @code{$_exitsignal} to @code{void}.
10097 @vindex $_exitsignal@r{, convenience variable}
10098 When the program being debugged dies due to an uncaught signal,
10099 @value{GDBN} automatically sets this variable to that signal's number,
10100 and resets @code{$_exitcode} to @code{void}.
10102 To distinguish between whether the program being debugged has exited
10103 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10104 @code{$_exitsignal} is not @code{void}), the convenience function
10105 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10106 Functions}). For example, considering the following source code:
10109 #include <signal.h>
10112 main (int argc, char *argv[])
10119 A valid way of telling whether the program being debugged has exited
10120 or signalled would be:
10123 (@value{GDBP}) define has_exited_or_signalled
10124 Type commands for definition of ``has_exited_or_signalled''.
10125 End with a line saying just ``end''.
10126 >if $_isvoid ($_exitsignal)
10127 >echo The program has exited\n
10129 >echo The program has signalled\n
10135 Program terminated with signal SIGALRM, Alarm clock.
10136 The program no longer exists.
10137 (@value{GDBP}) has_exited_or_signalled
10138 The program has signalled
10141 As can be seen, @value{GDBN} correctly informs that the program being
10142 debugged has signalled, since it calls @code{raise} and raises a
10143 @code{SIGALRM} signal. If the program being debugged had not called
10144 @code{raise}, then @value{GDBN} would report a normal exit:
10147 (@value{GDBP}) has_exited_or_signalled
10148 The program has exited
10152 The variable @code{$_exception} is set to the exception object being
10153 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10156 @itemx $_probe_arg0@dots{}$_probe_arg11
10157 Arguments to a static probe. @xref{Static Probe Points}.
10160 @vindex $_sdata@r{, inspect, convenience variable}
10161 The variable @code{$_sdata} contains extra collected static tracepoint
10162 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10163 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10164 if extra static tracepoint data has not been collected.
10167 @vindex $_siginfo@r{, convenience variable}
10168 The variable @code{$_siginfo} contains extra signal information
10169 (@pxref{extra signal information}). Note that @code{$_siginfo}
10170 could be empty, if the application has not yet received any signals.
10171 For example, it will be empty before you execute the @code{run} command.
10174 @vindex $_tlb@r{, convenience variable}
10175 The variable @code{$_tlb} is automatically set when debugging
10176 applications running on MS-Windows in native mode or connected to
10177 gdbserver that supports the @code{qGetTIBAddr} request.
10178 @xref{General Query Packets}.
10179 This variable contains the address of the thread information block.
10183 On HP-UX systems, if you refer to a function or variable name that
10184 begins with a dollar sign, @value{GDBN} searches for a user or system
10185 name first, before it searches for a convenience variable.
10187 @node Convenience Funs
10188 @section Convenience Functions
10190 @cindex convenience functions
10191 @value{GDBN} also supplies some @dfn{convenience functions}. These
10192 have a syntax similar to convenience variables. A convenience
10193 function can be used in an expression just like an ordinary function;
10194 however, a convenience function is implemented internally to
10197 These functions do not require @value{GDBN} to be configured with
10198 @code{Python} support, which means that they are always available.
10202 @item $_isvoid (@var{expr})
10203 @findex $_isvoid@r{, convenience function}
10204 Return one if the expression @var{expr} is @code{void}. Otherwise it
10207 A @code{void} expression is an expression where the type of the result
10208 is @code{void}. For example, you can examine a convenience variable
10209 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10213 (@value{GDBP}) print $_exitcode
10215 (@value{GDBP}) print $_isvoid ($_exitcode)
10218 Starting program: ./a.out
10219 [Inferior 1 (process 29572) exited normally]
10220 (@value{GDBP}) print $_exitcode
10222 (@value{GDBP}) print $_isvoid ($_exitcode)
10226 In the example above, we used @code{$_isvoid} to check whether
10227 @code{$_exitcode} is @code{void} before and after the execution of the
10228 program being debugged. Before the execution there is no exit code to
10229 be examined, therefore @code{$_exitcode} is @code{void}. After the
10230 execution the program being debugged returned zero, therefore
10231 @code{$_exitcode} is zero, which means that it is not @code{void}
10234 The @code{void} expression can also be a call of a function from the
10235 program being debugged. For example, given the following function:
10244 The result of calling it inside @value{GDBN} is @code{void}:
10247 (@value{GDBP}) print foo ()
10249 (@value{GDBP}) print $_isvoid (foo ())
10251 (@value{GDBP}) set $v = foo ()
10252 (@value{GDBP}) print $v
10254 (@value{GDBP}) print $_isvoid ($v)
10260 These functions require @value{GDBN} to be configured with
10261 @code{Python} support.
10265 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10266 @findex $_memeq@r{, convenience function}
10267 Returns one if the @var{length} bytes at the addresses given by
10268 @var{buf1} and @var{buf2} are equal.
10269 Otherwise it returns zero.
10271 @item $_regex(@var{str}, @var{regex})
10272 @findex $_regex@r{, convenience function}
10273 Returns one if the string @var{str} matches the regular expression
10274 @var{regex}. Otherwise it returns zero.
10275 The syntax of the regular expression is that specified by @code{Python}'s
10276 regular expression support.
10278 @item $_streq(@var{str1}, @var{str2})
10279 @findex $_streq@r{, convenience function}
10280 Returns one if the strings @var{str1} and @var{str2} are equal.
10281 Otherwise it returns zero.
10283 @item $_strlen(@var{str})
10284 @findex $_strlen@r{, convenience function}
10285 Returns the length of string @var{str}.
10287 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10288 @findex $_caller_is@r{, convenience function}
10289 Returns one if the calling function's name is equal to @var{name}.
10290 Otherwise it returns zero.
10292 If the optional argument @var{number_of_frames} is provided,
10293 it is the number of frames up in the stack to look.
10301 at testsuite/gdb.python/py-caller-is.c:21
10302 #1 0x00000000004005a0 in middle_func ()
10303 at testsuite/gdb.python/py-caller-is.c:27
10304 #2 0x00000000004005ab in top_func ()
10305 at testsuite/gdb.python/py-caller-is.c:33
10306 #3 0x00000000004005b6 in main ()
10307 at testsuite/gdb.python/py-caller-is.c:39
10308 (gdb) print $_caller_is ("middle_func")
10310 (gdb) print $_caller_is ("top_func", 2)
10314 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10315 @findex $_caller_matches@r{, convenience function}
10316 Returns one if the calling function's name matches the regular expression
10317 @var{regexp}. Otherwise it returns zero.
10319 If the optional argument @var{number_of_frames} is provided,
10320 it is the number of frames up in the stack to look.
10323 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10324 @findex $_any_caller_is@r{, convenience function}
10325 Returns one if any calling function's name is equal to @var{name}.
10326 Otherwise it returns zero.
10328 If the optional argument @var{number_of_frames} is provided,
10329 it is the number of frames up in the stack to look.
10332 This function differs from @code{$_caller_is} in that this function
10333 checks all stack frames from the immediate caller to the frame specified
10334 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10335 frame specified by @var{number_of_frames}.
10337 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10338 @findex $_any_caller_matches@r{, convenience function}
10339 Returns one if any calling function's name matches the regular expression
10340 @var{regexp}. Otherwise it returns zero.
10342 If the optional argument @var{number_of_frames} is provided,
10343 it is the number of frames up in the stack to look.
10346 This function differs from @code{$_caller_matches} in that this function
10347 checks all stack frames from the immediate caller to the frame specified
10348 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10349 frame specified by @var{number_of_frames}.
10353 @value{GDBN} provides the ability to list and get help on
10354 convenience functions.
10357 @item help function
10358 @kindex help function
10359 @cindex show all convenience functions
10360 Print a list of all convenience functions.
10367 You can refer to machine register contents, in expressions, as variables
10368 with names starting with @samp{$}. The names of registers are different
10369 for each machine; use @code{info registers} to see the names used on
10373 @kindex info registers
10374 @item info registers
10375 Print the names and values of all registers except floating-point
10376 and vector registers (in the selected stack frame).
10378 @kindex info all-registers
10379 @cindex floating point registers
10380 @item info all-registers
10381 Print the names and values of all registers, including floating-point
10382 and vector registers (in the selected stack frame).
10384 @item info registers @var{regname} @dots{}
10385 Print the @dfn{relativized} value of each specified register @var{regname}.
10386 As discussed in detail below, register values are normally relative to
10387 the selected stack frame. The @var{regname} may be any register name valid on
10388 the machine you are using, with or without the initial @samp{$}.
10391 @anchor{standard registers}
10392 @cindex stack pointer register
10393 @cindex program counter register
10394 @cindex process status register
10395 @cindex frame pointer register
10396 @cindex standard registers
10397 @value{GDBN} has four ``standard'' register names that are available (in
10398 expressions) on most machines---whenever they do not conflict with an
10399 architecture's canonical mnemonics for registers. The register names
10400 @code{$pc} and @code{$sp} are used for the program counter register and
10401 the stack pointer. @code{$fp} is used for a register that contains a
10402 pointer to the current stack frame, and @code{$ps} is used for a
10403 register that contains the processor status. For example,
10404 you could print the program counter in hex with
10411 or print the instruction to be executed next with
10418 or add four to the stack pointer@footnote{This is a way of removing
10419 one word from the stack, on machines where stacks grow downward in
10420 memory (most machines, nowadays). This assumes that the innermost
10421 stack frame is selected; setting @code{$sp} is not allowed when other
10422 stack frames are selected. To pop entire frames off the stack,
10423 regardless of machine architecture, use @code{return};
10424 see @ref{Returning, ,Returning from a Function}.} with
10430 Whenever possible, these four standard register names are available on
10431 your machine even though the machine has different canonical mnemonics,
10432 so long as there is no conflict. The @code{info registers} command
10433 shows the canonical names. For example, on the SPARC, @code{info
10434 registers} displays the processor status register as @code{$psr} but you
10435 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10436 is an alias for the @sc{eflags} register.
10438 @value{GDBN} always considers the contents of an ordinary register as an
10439 integer when the register is examined in this way. Some machines have
10440 special registers which can hold nothing but floating point; these
10441 registers are considered to have floating point values. There is no way
10442 to refer to the contents of an ordinary register as floating point value
10443 (although you can @emph{print} it as a floating point value with
10444 @samp{print/f $@var{regname}}).
10446 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10447 means that the data format in which the register contents are saved by
10448 the operating system is not the same one that your program normally
10449 sees. For example, the registers of the 68881 floating point
10450 coprocessor are always saved in ``extended'' (raw) format, but all C
10451 programs expect to work with ``double'' (virtual) format. In such
10452 cases, @value{GDBN} normally works with the virtual format only (the format
10453 that makes sense for your program), but the @code{info registers} command
10454 prints the data in both formats.
10456 @cindex SSE registers (x86)
10457 @cindex MMX registers (x86)
10458 Some machines have special registers whose contents can be interpreted
10459 in several different ways. For example, modern x86-based machines
10460 have SSE and MMX registers that can hold several values packed
10461 together in several different formats. @value{GDBN} refers to such
10462 registers in @code{struct} notation:
10465 (@value{GDBP}) print $xmm1
10467 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10468 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10469 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10470 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10471 v4_int32 = @{0, 20657912, 11, 13@},
10472 v2_int64 = @{88725056443645952, 55834574859@},
10473 uint128 = 0x0000000d0000000b013b36f800000000
10478 To set values of such registers, you need to tell @value{GDBN} which
10479 view of the register you wish to change, as if you were assigning
10480 value to a @code{struct} member:
10483 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10486 Normally, register values are relative to the selected stack frame
10487 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10488 value that the register would contain if all stack frames farther in
10489 were exited and their saved registers restored. In order to see the
10490 true contents of hardware registers, you must select the innermost
10491 frame (with @samp{frame 0}).
10493 @cindex caller-saved registers
10494 @cindex call-clobbered registers
10495 @cindex volatile registers
10496 @cindex <not saved> values
10497 Usually ABIs reserve some registers as not needed to be saved by the
10498 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10499 registers). It may therefore not be possible for @value{GDBN} to know
10500 the value a register had before the call (in other words, in the outer
10501 frame), if the register value has since been changed by the callee.
10502 @value{GDBN} tries to deduce where the inner frame saved
10503 (``callee-saved'') registers, from the debug info, unwind info, or the
10504 machine code generated by your compiler. If some register is not
10505 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10506 its own knowledge of the ABI, or because the debug/unwind info
10507 explicitly says the register's value is undefined), @value{GDBN}
10508 displays @w{@samp{<not saved>}} as the register's value. With targets
10509 that @value{GDBN} has no knowledge of the register saving convention,
10510 if a register was not saved by the callee, then its value and location
10511 in the outer frame are assumed to be the same of the inner frame.
10512 This is usually harmless, because if the register is call-clobbered,
10513 the caller either does not care what is in the register after the
10514 call, or has code to restore the value that it does care about. Note,
10515 however, that if you change such a register in the outer frame, you
10516 may also be affecting the inner frame. Also, the more ``outer'' the
10517 frame is you're looking at, the more likely a call-clobbered
10518 register's value is to be wrong, in the sense that it doesn't actually
10519 represent the value the register had just before the call.
10521 @node Floating Point Hardware
10522 @section Floating Point Hardware
10523 @cindex floating point
10525 Depending on the configuration, @value{GDBN} may be able to give
10526 you more information about the status of the floating point hardware.
10531 Display hardware-dependent information about the floating
10532 point unit. The exact contents and layout vary depending on the
10533 floating point chip. Currently, @samp{info float} is supported on
10534 the ARM and x86 machines.
10538 @section Vector Unit
10539 @cindex vector unit
10541 Depending on the configuration, @value{GDBN} may be able to give you
10542 more information about the status of the vector unit.
10545 @kindex info vector
10547 Display information about the vector unit. The exact contents and
10548 layout vary depending on the hardware.
10551 @node OS Information
10552 @section Operating System Auxiliary Information
10553 @cindex OS information
10555 @value{GDBN} provides interfaces to useful OS facilities that can help
10556 you debug your program.
10558 @cindex auxiliary vector
10559 @cindex vector, auxiliary
10560 Some operating systems supply an @dfn{auxiliary vector} to programs at
10561 startup. This is akin to the arguments and environment that you
10562 specify for a program, but contains a system-dependent variety of
10563 binary values that tell system libraries important details about the
10564 hardware, operating system, and process. Each value's purpose is
10565 identified by an integer tag; the meanings are well-known but system-specific.
10566 Depending on the configuration and operating system facilities,
10567 @value{GDBN} may be able to show you this information. For remote
10568 targets, this functionality may further depend on the remote stub's
10569 support of the @samp{qXfer:auxv:read} packet, see
10570 @ref{qXfer auxiliary vector read}.
10575 Display the auxiliary vector of the inferior, which can be either a
10576 live process or a core dump file. @value{GDBN} prints each tag value
10577 numerically, and also shows names and text descriptions for recognized
10578 tags. Some values in the vector are numbers, some bit masks, and some
10579 pointers to strings or other data. @value{GDBN} displays each value in the
10580 most appropriate form for a recognized tag, and in hexadecimal for
10581 an unrecognized tag.
10584 On some targets, @value{GDBN} can access operating system-specific
10585 information and show it to you. The types of information available
10586 will differ depending on the type of operating system running on the
10587 target. The mechanism used to fetch the data is described in
10588 @ref{Operating System Information}. For remote targets, this
10589 functionality depends on the remote stub's support of the
10590 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10594 @item info os @var{infotype}
10596 Display OS information of the requested type.
10598 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10600 @anchor{linux info os infotypes}
10602 @kindex info os cpus
10604 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
10605 the available fields from /proc/cpuinfo. For each supported architecture
10606 different fields are available. Two common entries are processor which gives
10607 CPU number and bogomips; a system constant that is calculated during
10608 kernel initialization.
10610 @kindex info os files
10612 Display the list of open file descriptors on the target. For each
10613 file descriptor, @value{GDBN} prints the identifier of the process
10614 owning the descriptor, the command of the owning process, the value
10615 of the descriptor, and the target of the descriptor.
10617 @kindex info os modules
10619 Display the list of all loaded kernel modules on the target. For each
10620 module, @value{GDBN} prints the module name, the size of the module in
10621 bytes, the number of times the module is used, the dependencies of the
10622 module, the status of the module, and the address of the loaded module
10625 @kindex info os msg
10627 Display the list of all System V message queues on the target. For each
10628 message queue, @value{GDBN} prints the message queue key, the message
10629 queue identifier, the access permissions, the current number of bytes
10630 on the queue, the current number of messages on the queue, the processes
10631 that last sent and received a message on the queue, the user and group
10632 of the owner and creator of the message queue, the times at which a
10633 message was last sent and received on the queue, and the time at which
10634 the message queue was last changed.
10636 @kindex info os processes
10638 Display the list of processes on the target. For each process,
10639 @value{GDBN} prints the process identifier, the name of the user, the
10640 command corresponding to the process, and the list of processor cores
10641 that the process is currently running on. (To understand what these
10642 properties mean, for this and the following info types, please consult
10643 the general @sc{gnu}/Linux documentation.)
10645 @kindex info os procgroups
10647 Display the list of process groups on the target. For each process,
10648 @value{GDBN} prints the identifier of the process group that it belongs
10649 to, the command corresponding to the process group leader, the process
10650 identifier, and the command line of the process. The list is sorted
10651 first by the process group identifier, then by the process identifier,
10652 so that processes belonging to the same process group are grouped together
10653 and the process group leader is listed first.
10655 @kindex info os semaphores
10657 Display the list of all System V semaphore sets on the target. For each
10658 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10659 set identifier, the access permissions, the number of semaphores in the
10660 set, the user and group of the owner and creator of the semaphore set,
10661 and the times at which the semaphore set was operated upon and changed.
10663 @kindex info os shm
10665 Display the list of all System V shared-memory regions on the target.
10666 For each shared-memory region, @value{GDBN} prints the region key,
10667 the shared-memory identifier, the access permissions, the size of the
10668 region, the process that created the region, the process that last
10669 attached to or detached from the region, the current number of live
10670 attaches to the region, and the times at which the region was last
10671 attached to, detach from, and changed.
10673 @kindex info os sockets
10675 Display the list of Internet-domain sockets on the target. For each
10676 socket, @value{GDBN} prints the address and port of the local and
10677 remote endpoints, the current state of the connection, the creator of
10678 the socket, the IP address family of the socket, and the type of the
10681 @kindex info os threads
10683 Display the list of threads running on the target. For each thread,
10684 @value{GDBN} prints the identifier of the process that the thread
10685 belongs to, the command of the process, the thread identifier, and the
10686 processor core that it is currently running on. The main thread of a
10687 process is not listed.
10691 If @var{infotype} is omitted, then list the possible values for
10692 @var{infotype} and the kind of OS information available for each
10693 @var{infotype}. If the target does not return a list of possible
10694 types, this command will report an error.
10697 @node Memory Region Attributes
10698 @section Memory Region Attributes
10699 @cindex memory region attributes
10701 @dfn{Memory region attributes} allow you to describe special handling
10702 required by regions of your target's memory. @value{GDBN} uses
10703 attributes to determine whether to allow certain types of memory
10704 accesses; whether to use specific width accesses; and whether to cache
10705 target memory. By default the description of memory regions is
10706 fetched from the target (if the current target supports this), but the
10707 user can override the fetched regions.
10709 Defined memory regions can be individually enabled and disabled. When a
10710 memory region is disabled, @value{GDBN} uses the default attributes when
10711 accessing memory in that region. Similarly, if no memory regions have
10712 been defined, @value{GDBN} uses the default attributes when accessing
10715 When a memory region is defined, it is given a number to identify it;
10716 to enable, disable, or remove a memory region, you specify that number.
10720 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10721 Define a memory region bounded by @var{lower} and @var{upper} with
10722 attributes @var{attributes}@dots{}, and add it to the list of regions
10723 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10724 case: it is treated as the target's maximum memory address.
10725 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10728 Discard any user changes to the memory regions and use target-supplied
10729 regions, if available, or no regions if the target does not support.
10732 @item delete mem @var{nums}@dots{}
10733 Remove memory regions @var{nums}@dots{} from the list of regions
10734 monitored by @value{GDBN}.
10736 @kindex disable mem
10737 @item disable mem @var{nums}@dots{}
10738 Disable monitoring of memory regions @var{nums}@dots{}.
10739 A disabled memory region is not forgotten.
10740 It may be enabled again later.
10743 @item enable mem @var{nums}@dots{}
10744 Enable monitoring of memory regions @var{nums}@dots{}.
10748 Print a table of all defined memory regions, with the following columns
10752 @item Memory Region Number
10753 @item Enabled or Disabled.
10754 Enabled memory regions are marked with @samp{y}.
10755 Disabled memory regions are marked with @samp{n}.
10758 The address defining the inclusive lower bound of the memory region.
10761 The address defining the exclusive upper bound of the memory region.
10764 The list of attributes set for this memory region.
10769 @subsection Attributes
10771 @subsubsection Memory Access Mode
10772 The access mode attributes set whether @value{GDBN} may make read or
10773 write accesses to a memory region.
10775 While these attributes prevent @value{GDBN} from performing invalid
10776 memory accesses, they do nothing to prevent the target system, I/O DMA,
10777 etc.@: from accessing memory.
10781 Memory is read only.
10783 Memory is write only.
10785 Memory is read/write. This is the default.
10788 @subsubsection Memory Access Size
10789 The access size attribute tells @value{GDBN} to use specific sized
10790 accesses in the memory region. Often memory mapped device registers
10791 require specific sized accesses. If no access size attribute is
10792 specified, @value{GDBN} may use accesses of any size.
10796 Use 8 bit memory accesses.
10798 Use 16 bit memory accesses.
10800 Use 32 bit memory accesses.
10802 Use 64 bit memory accesses.
10805 @c @subsubsection Hardware/Software Breakpoints
10806 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10807 @c will use hardware or software breakpoints for the internal breakpoints
10808 @c used by the step, next, finish, until, etc. commands.
10812 @c Always use hardware breakpoints
10813 @c @item swbreak (default)
10816 @subsubsection Data Cache
10817 The data cache attributes set whether @value{GDBN} will cache target
10818 memory. While this generally improves performance by reducing debug
10819 protocol overhead, it can lead to incorrect results because @value{GDBN}
10820 does not know about volatile variables or memory mapped device
10825 Enable @value{GDBN} to cache target memory.
10827 Disable @value{GDBN} from caching target memory. This is the default.
10830 @subsection Memory Access Checking
10831 @value{GDBN} can be instructed to refuse accesses to memory that is
10832 not explicitly described. This can be useful if accessing such
10833 regions has undesired effects for a specific target, or to provide
10834 better error checking. The following commands control this behaviour.
10837 @kindex set mem inaccessible-by-default
10838 @item set mem inaccessible-by-default [on|off]
10839 If @code{on} is specified, make @value{GDBN} treat memory not
10840 explicitly described by the memory ranges as non-existent and refuse accesses
10841 to such memory. The checks are only performed if there's at least one
10842 memory range defined. If @code{off} is specified, make @value{GDBN}
10843 treat the memory not explicitly described by the memory ranges as RAM.
10844 The default value is @code{on}.
10845 @kindex show mem inaccessible-by-default
10846 @item show mem inaccessible-by-default
10847 Show the current handling of accesses to unknown memory.
10851 @c @subsubsection Memory Write Verification
10852 @c The memory write verification attributes set whether @value{GDBN}
10853 @c will re-reads data after each write to verify the write was successful.
10857 @c @item noverify (default)
10860 @node Dump/Restore Files
10861 @section Copy Between Memory and a File
10862 @cindex dump/restore files
10863 @cindex append data to a file
10864 @cindex dump data to a file
10865 @cindex restore data from a file
10867 You can use the commands @code{dump}, @code{append}, and
10868 @code{restore} to copy data between target memory and a file. The
10869 @code{dump} and @code{append} commands write data to a file, and the
10870 @code{restore} command reads data from a file back into the inferior's
10871 memory. Files may be in binary, Motorola S-record, Intel hex, or
10872 Tektronix Hex format; however, @value{GDBN} can only append to binary
10878 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10879 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10880 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10881 or the value of @var{expr}, to @var{filename} in the given format.
10883 The @var{format} parameter may be any one of:
10890 Motorola S-record format.
10892 Tektronix Hex format.
10895 @value{GDBN} uses the same definitions of these formats as the
10896 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10897 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10901 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10902 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10903 Append the contents of memory from @var{start_addr} to @var{end_addr},
10904 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10905 (@value{GDBN} can only append data to files in raw binary form.)
10908 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10909 Restore the contents of file @var{filename} into memory. The
10910 @code{restore} command can automatically recognize any known @sc{bfd}
10911 file format, except for raw binary. To restore a raw binary file you
10912 must specify the optional keyword @code{binary} after the filename.
10914 If @var{bias} is non-zero, its value will be added to the addresses
10915 contained in the file. Binary files always start at address zero, so
10916 they will be restored at address @var{bias}. Other bfd files have
10917 a built-in location; they will be restored at offset @var{bias}
10918 from that location.
10920 If @var{start} and/or @var{end} are non-zero, then only data between
10921 file offset @var{start} and file offset @var{end} will be restored.
10922 These offsets are relative to the addresses in the file, before
10923 the @var{bias} argument is applied.
10927 @node Core File Generation
10928 @section How to Produce a Core File from Your Program
10929 @cindex dump core from inferior
10931 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10932 image of a running process and its process status (register values
10933 etc.). Its primary use is post-mortem debugging of a program that
10934 crashed while it ran outside a debugger. A program that crashes
10935 automatically produces a core file, unless this feature is disabled by
10936 the user. @xref{Files}, for information on invoking @value{GDBN} in
10937 the post-mortem debugging mode.
10939 Occasionally, you may wish to produce a core file of the program you
10940 are debugging in order to preserve a snapshot of its state.
10941 @value{GDBN} has a special command for that.
10945 @kindex generate-core-file
10946 @item generate-core-file [@var{file}]
10947 @itemx gcore [@var{file}]
10948 Produce a core dump of the inferior process. The optional argument
10949 @var{file} specifies the file name where to put the core dump. If not
10950 specified, the file name defaults to @file{core.@var{pid}}, where
10951 @var{pid} is the inferior process ID.
10953 Note that this command is implemented only for some systems (as of
10954 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10956 On @sc{gnu}/Linux, this command can take into account the value of the
10957 file @file{/proc/@var{pid}/coredump_filter} when generating the core
10958 dump (@pxref{set use-coredump-filter}).
10960 @kindex set use-coredump-filter
10961 @anchor{set use-coredump-filter}
10962 @item set use-coredump-filter on
10963 @itemx set use-coredump-filter off
10964 Enable or disable the use of the file
10965 @file{/proc/@var{pid}/coredump_filter} when generating core dump
10966 files. This file is used by the Linux kernel to decide what types of
10967 memory mappings will be dumped or ignored when generating a core dump
10968 file. @var{pid} is the process ID of a currently running process.
10970 To make use of this feature, you have to write in the
10971 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
10972 which is a bit mask representing the memory mapping types. If a bit
10973 is set in the bit mask, then the memory mappings of the corresponding
10974 types will be dumped; otherwise, they will be ignored. This
10975 configuration is inherited by child processes. For more information
10976 about the bits that can be set in the
10977 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
10978 manpage of @code{core(5)}.
10980 By default, this option is @code{on}. If this option is turned
10981 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
10982 and instead uses the same default value as the Linux kernel in order
10983 to decide which pages will be dumped in the core dump file. This
10984 value is currently @code{0x33}, which means that bits @code{0}
10985 (anonymous private mappings), @code{1} (anonymous shared mappings),
10986 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
10987 This will cause these memory mappings to be dumped automatically.
10990 @node Character Sets
10991 @section Character Sets
10992 @cindex character sets
10994 @cindex translating between character sets
10995 @cindex host character set
10996 @cindex target character set
10998 If the program you are debugging uses a different character set to
10999 represent characters and strings than the one @value{GDBN} uses itself,
11000 @value{GDBN} can automatically translate between the character sets for
11001 you. The character set @value{GDBN} uses we call the @dfn{host
11002 character set}; the one the inferior program uses we call the
11003 @dfn{target character set}.
11005 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11006 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11007 remote protocol (@pxref{Remote Debugging}) to debug a program
11008 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11009 then the host character set is Latin-1, and the target character set is
11010 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11011 target-charset EBCDIC-US}, then @value{GDBN} translates between
11012 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11013 character and string literals in expressions.
11015 @value{GDBN} has no way to automatically recognize which character set
11016 the inferior program uses; you must tell it, using the @code{set
11017 target-charset} command, described below.
11019 Here are the commands for controlling @value{GDBN}'s character set
11023 @item set target-charset @var{charset}
11024 @kindex set target-charset
11025 Set the current target character set to @var{charset}. To display the
11026 list of supported target character sets, type
11027 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11029 @item set host-charset @var{charset}
11030 @kindex set host-charset
11031 Set the current host character set to @var{charset}.
11033 By default, @value{GDBN} uses a host character set appropriate to the
11034 system it is running on; you can override that default using the
11035 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11036 automatically determine the appropriate host character set. In this
11037 case, @value{GDBN} uses @samp{UTF-8}.
11039 @value{GDBN} can only use certain character sets as its host character
11040 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11041 @value{GDBN} will list the host character sets it supports.
11043 @item set charset @var{charset}
11044 @kindex set charset
11045 Set the current host and target character sets to @var{charset}. As
11046 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11047 @value{GDBN} will list the names of the character sets that can be used
11048 for both host and target.
11051 @kindex show charset
11052 Show the names of the current host and target character sets.
11054 @item show host-charset
11055 @kindex show host-charset
11056 Show the name of the current host character set.
11058 @item show target-charset
11059 @kindex show target-charset
11060 Show the name of the current target character set.
11062 @item set target-wide-charset @var{charset}
11063 @kindex set target-wide-charset
11064 Set the current target's wide character set to @var{charset}. This is
11065 the character set used by the target's @code{wchar_t} type. To
11066 display the list of supported wide character sets, type
11067 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11069 @item show target-wide-charset
11070 @kindex show target-wide-charset
11071 Show the name of the current target's wide character set.
11074 Here is an example of @value{GDBN}'s character set support in action.
11075 Assume that the following source code has been placed in the file
11076 @file{charset-test.c}:
11082 = @{72, 101, 108, 108, 111, 44, 32, 119,
11083 111, 114, 108, 100, 33, 10, 0@};
11084 char ibm1047_hello[]
11085 = @{200, 133, 147, 147, 150, 107, 64, 166,
11086 150, 153, 147, 132, 90, 37, 0@};
11090 printf ("Hello, world!\n");
11094 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11095 containing the string @samp{Hello, world!} followed by a newline,
11096 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11098 We compile the program, and invoke the debugger on it:
11101 $ gcc -g charset-test.c -o charset-test
11102 $ gdb -nw charset-test
11103 GNU gdb 2001-12-19-cvs
11104 Copyright 2001 Free Software Foundation, Inc.
11109 We can use the @code{show charset} command to see what character sets
11110 @value{GDBN} is currently using to interpret and display characters and
11114 (@value{GDBP}) show charset
11115 The current host and target character set is `ISO-8859-1'.
11119 For the sake of printing this manual, let's use @sc{ascii} as our
11120 initial character set:
11122 (@value{GDBP}) set charset ASCII
11123 (@value{GDBP}) show charset
11124 The current host and target character set is `ASCII'.
11128 Let's assume that @sc{ascii} is indeed the correct character set for our
11129 host system --- in other words, let's assume that if @value{GDBN} prints
11130 characters using the @sc{ascii} character set, our terminal will display
11131 them properly. Since our current target character set is also
11132 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11135 (@value{GDBP}) print ascii_hello
11136 $1 = 0x401698 "Hello, world!\n"
11137 (@value{GDBP}) print ascii_hello[0]
11142 @value{GDBN} uses the target character set for character and string
11143 literals you use in expressions:
11146 (@value{GDBP}) print '+'
11151 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11154 @value{GDBN} relies on the user to tell it which character set the
11155 target program uses. If we print @code{ibm1047_hello} while our target
11156 character set is still @sc{ascii}, we get jibberish:
11159 (@value{GDBP}) print ibm1047_hello
11160 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11161 (@value{GDBP}) print ibm1047_hello[0]
11166 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11167 @value{GDBN} tells us the character sets it supports:
11170 (@value{GDBP}) set target-charset
11171 ASCII EBCDIC-US IBM1047 ISO-8859-1
11172 (@value{GDBP}) set target-charset
11175 We can select @sc{ibm1047} as our target character set, and examine the
11176 program's strings again. Now the @sc{ascii} string is wrong, but
11177 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11178 target character set, @sc{ibm1047}, to the host character set,
11179 @sc{ascii}, and they display correctly:
11182 (@value{GDBP}) set target-charset IBM1047
11183 (@value{GDBP}) show charset
11184 The current host character set is `ASCII'.
11185 The current target character set is `IBM1047'.
11186 (@value{GDBP}) print ascii_hello
11187 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11188 (@value{GDBP}) print ascii_hello[0]
11190 (@value{GDBP}) print ibm1047_hello
11191 $8 = 0x4016a8 "Hello, world!\n"
11192 (@value{GDBP}) print ibm1047_hello[0]
11197 As above, @value{GDBN} uses the target character set for character and
11198 string literals you use in expressions:
11201 (@value{GDBP}) print '+'
11206 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11209 @node Caching Target Data
11210 @section Caching Data of Targets
11211 @cindex caching data of targets
11213 @value{GDBN} caches data exchanged between the debugger and a target.
11214 Each cache is associated with the address space of the inferior.
11215 @xref{Inferiors and Programs}, about inferior and address space.
11216 Such caching generally improves performance in remote debugging
11217 (@pxref{Remote Debugging}), because it reduces the overhead of the
11218 remote protocol by bundling memory reads and writes into large chunks.
11219 Unfortunately, simply caching everything would lead to incorrect results,
11220 since @value{GDBN} does not necessarily know anything about volatile
11221 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11222 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11224 Therefore, by default, @value{GDBN} only caches data
11225 known to be on the stack@footnote{In non-stop mode, it is moderately
11226 rare for a running thread to modify the stack of a stopped thread
11227 in a way that would interfere with a backtrace, and caching of
11228 stack reads provides a significant speed up of remote backtraces.} or
11229 in the code segment.
11230 Other regions of memory can be explicitly marked as
11231 cacheable; @pxref{Memory Region Attributes}.
11234 @kindex set remotecache
11235 @item set remotecache on
11236 @itemx set remotecache off
11237 This option no longer does anything; it exists for compatibility
11240 @kindex show remotecache
11241 @item show remotecache
11242 Show the current state of the obsolete remotecache flag.
11244 @kindex set stack-cache
11245 @item set stack-cache on
11246 @itemx set stack-cache off
11247 Enable or disable caching of stack accesses. When @code{on}, use
11248 caching. By default, this option is @code{on}.
11250 @kindex show stack-cache
11251 @item show stack-cache
11252 Show the current state of data caching for memory accesses.
11254 @kindex set code-cache
11255 @item set code-cache on
11256 @itemx set code-cache off
11257 Enable or disable caching of code segment accesses. When @code{on},
11258 use caching. By default, this option is @code{on}. This improves
11259 performance of disassembly in remote debugging.
11261 @kindex show code-cache
11262 @item show code-cache
11263 Show the current state of target memory cache for code segment
11266 @kindex info dcache
11267 @item info dcache @r{[}line@r{]}
11268 Print the information about the performance of data cache of the
11269 current inferior's address space. The information displayed
11270 includes the dcache width and depth, and for each cache line, its
11271 number, address, and how many times it was referenced. This
11272 command is useful for debugging the data cache operation.
11274 If a line number is specified, the contents of that line will be
11277 @item set dcache size @var{size}
11278 @cindex dcache size
11279 @kindex set dcache size
11280 Set maximum number of entries in dcache (dcache depth above).
11282 @item set dcache line-size @var{line-size}
11283 @cindex dcache line-size
11284 @kindex set dcache line-size
11285 Set number of bytes each dcache entry caches (dcache width above).
11286 Must be a power of 2.
11288 @item show dcache size
11289 @kindex show dcache size
11290 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11292 @item show dcache line-size
11293 @kindex show dcache line-size
11294 Show default size of dcache lines.
11298 @node Searching Memory
11299 @section Search Memory
11300 @cindex searching memory
11302 Memory can be searched for a particular sequence of bytes with the
11303 @code{find} command.
11307 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11308 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11309 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11310 etc. The search begins at address @var{start_addr} and continues for either
11311 @var{len} bytes or through to @var{end_addr} inclusive.
11314 @var{s} and @var{n} are optional parameters.
11315 They may be specified in either order, apart or together.
11318 @item @var{s}, search query size
11319 The size of each search query value.
11325 halfwords (two bytes)
11329 giant words (eight bytes)
11332 All values are interpreted in the current language.
11333 This means, for example, that if the current source language is C/C@t{++}
11334 then searching for the string ``hello'' includes the trailing '\0'.
11336 If the value size is not specified, it is taken from the
11337 value's type in the current language.
11338 This is useful when one wants to specify the search
11339 pattern as a mixture of types.
11340 Note that this means, for example, that in the case of C-like languages
11341 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11342 which is typically four bytes.
11344 @item @var{n}, maximum number of finds
11345 The maximum number of matches to print. The default is to print all finds.
11348 You can use strings as search values. Quote them with double-quotes
11350 The string value is copied into the search pattern byte by byte,
11351 regardless of the endianness of the target and the size specification.
11353 The address of each match found is printed as well as a count of the
11354 number of matches found.
11356 The address of the last value found is stored in convenience variable
11358 A count of the number of matches is stored in @samp{$numfound}.
11360 For example, if stopped at the @code{printf} in this function:
11366 static char hello[] = "hello-hello";
11367 static struct @{ char c; short s; int i; @}
11368 __attribute__ ((packed)) mixed
11369 = @{ 'c', 0x1234, 0x87654321 @};
11370 printf ("%s\n", hello);
11375 you get during debugging:
11378 (gdb) find &hello[0], +sizeof(hello), "hello"
11379 0x804956d <hello.1620+6>
11381 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11382 0x8049567 <hello.1620>
11383 0x804956d <hello.1620+6>
11385 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11386 0x8049567 <hello.1620>
11388 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11389 0x8049560 <mixed.1625>
11391 (gdb) print $numfound
11394 $2 = (void *) 0x8049560
11397 @node Optimized Code
11398 @chapter Debugging Optimized Code
11399 @cindex optimized code, debugging
11400 @cindex debugging optimized code
11402 Almost all compilers support optimization. With optimization
11403 disabled, the compiler generates assembly code that corresponds
11404 directly to your source code, in a simplistic way. As the compiler
11405 applies more powerful optimizations, the generated assembly code
11406 diverges from your original source code. With help from debugging
11407 information generated by the compiler, @value{GDBN} can map from
11408 the running program back to constructs from your original source.
11410 @value{GDBN} is more accurate with optimization disabled. If you
11411 can recompile without optimization, it is easier to follow the
11412 progress of your program during debugging. But, there are many cases
11413 where you may need to debug an optimized version.
11415 When you debug a program compiled with @samp{-g -O}, remember that the
11416 optimizer has rearranged your code; the debugger shows you what is
11417 really there. Do not be too surprised when the execution path does not
11418 exactly match your source file! An extreme example: if you define a
11419 variable, but never use it, @value{GDBN} never sees that
11420 variable---because the compiler optimizes it out of existence.
11422 Some things do not work as well with @samp{-g -O} as with just
11423 @samp{-g}, particularly on machines with instruction scheduling. If in
11424 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11425 please report it to us as a bug (including a test case!).
11426 @xref{Variables}, for more information about debugging optimized code.
11429 * Inline Functions:: How @value{GDBN} presents inlining
11430 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11433 @node Inline Functions
11434 @section Inline Functions
11435 @cindex inline functions, debugging
11437 @dfn{Inlining} is an optimization that inserts a copy of the function
11438 body directly at each call site, instead of jumping to a shared
11439 routine. @value{GDBN} displays inlined functions just like
11440 non-inlined functions. They appear in backtraces. You can view their
11441 arguments and local variables, step into them with @code{step}, skip
11442 them with @code{next}, and escape from them with @code{finish}.
11443 You can check whether a function was inlined by using the
11444 @code{info frame} command.
11446 For @value{GDBN} to support inlined functions, the compiler must
11447 record information about inlining in the debug information ---
11448 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11449 other compilers do also. @value{GDBN} only supports inlined functions
11450 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11451 do not emit two required attributes (@samp{DW_AT_call_file} and
11452 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11453 function calls with earlier versions of @value{NGCC}. It instead
11454 displays the arguments and local variables of inlined functions as
11455 local variables in the caller.
11457 The body of an inlined function is directly included at its call site;
11458 unlike a non-inlined function, there are no instructions devoted to
11459 the call. @value{GDBN} still pretends that the call site and the
11460 start of the inlined function are different instructions. Stepping to
11461 the call site shows the call site, and then stepping again shows
11462 the first line of the inlined function, even though no additional
11463 instructions are executed.
11465 This makes source-level debugging much clearer; you can see both the
11466 context of the call and then the effect of the call. Only stepping by
11467 a single instruction using @code{stepi} or @code{nexti} does not do
11468 this; single instruction steps always show the inlined body.
11470 There are some ways that @value{GDBN} does not pretend that inlined
11471 function calls are the same as normal calls:
11475 Setting breakpoints at the call site of an inlined function may not
11476 work, because the call site does not contain any code. @value{GDBN}
11477 may incorrectly move the breakpoint to the next line of the enclosing
11478 function, after the call. This limitation will be removed in a future
11479 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11480 or inside the inlined function instead.
11483 @value{GDBN} cannot locate the return value of inlined calls after
11484 using the @code{finish} command. This is a limitation of compiler-generated
11485 debugging information; after @code{finish}, you can step to the next line
11486 and print a variable where your program stored the return value.
11490 @node Tail Call Frames
11491 @section Tail Call Frames
11492 @cindex tail call frames, debugging
11494 Function @code{B} can call function @code{C} in its very last statement. In
11495 unoptimized compilation the call of @code{C} is immediately followed by return
11496 instruction at the end of @code{B} code. Optimizing compiler may replace the
11497 call and return in function @code{B} into one jump to function @code{C}
11498 instead. Such use of a jump instruction is called @dfn{tail call}.
11500 During execution of function @code{C}, there will be no indication in the
11501 function call stack frames that it was tail-called from @code{B}. If function
11502 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11503 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11504 some cases @value{GDBN} can determine that @code{C} was tail-called from
11505 @code{B}, and it will then create fictitious call frame for that, with the
11506 return address set up as if @code{B} called @code{C} normally.
11508 This functionality is currently supported only by DWARF 2 debugging format and
11509 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11510 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11513 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11514 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11518 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11520 Stack level 1, frame at 0x7fffffffda30:
11521 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11522 tail call frame, caller of frame at 0x7fffffffda30
11523 source language c++.
11524 Arglist at unknown address.
11525 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11528 The detection of all the possible code path executions can find them ambiguous.
11529 There is no execution history stored (possible @ref{Reverse Execution} is never
11530 used for this purpose) and the last known caller could have reached the known
11531 callee by multiple different jump sequences. In such case @value{GDBN} still
11532 tries to show at least all the unambiguous top tail callers and all the
11533 unambiguous bottom tail calees, if any.
11536 @anchor{set debug entry-values}
11537 @item set debug entry-values
11538 @kindex set debug entry-values
11539 When set to on, enables printing of analysis messages for both frame argument
11540 values at function entry and tail calls. It will show all the possible valid
11541 tail calls code paths it has considered. It will also print the intersection
11542 of them with the final unambiguous (possibly partial or even empty) code path
11545 @item show debug entry-values
11546 @kindex show debug entry-values
11547 Show the current state of analysis messages printing for both frame argument
11548 values at function entry and tail calls.
11551 The analysis messages for tail calls can for example show why the virtual tail
11552 call frame for function @code{c} has not been recognized (due to the indirect
11553 reference by variable @code{x}):
11556 static void __attribute__((noinline, noclone)) c (void);
11557 void (*x) (void) = c;
11558 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11559 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11560 int main (void) @{ x (); return 0; @}
11562 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11563 DW_TAG_GNU_call_site 0x40039a in main
11565 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11568 #1 0x000000000040039a in main () at t.c:5
11571 Another possibility is an ambiguous virtual tail call frames resolution:
11575 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11576 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11577 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11578 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11579 static void __attribute__((noinline, noclone)) b (void)
11580 @{ if (i) c (); else e (); @}
11581 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11582 int main (void) @{ a (); return 0; @}
11584 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11585 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11586 tailcall: reduced: 0x4004d2(a) |
11589 #1 0x00000000004004d2 in a () at t.c:8
11590 #2 0x0000000000400395 in main () at t.c:9
11593 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11594 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11596 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11597 @ifset HAVE_MAKEINFO_CLICK
11598 @set ARROW @click{}
11599 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11600 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11602 @ifclear HAVE_MAKEINFO_CLICK
11604 @set CALLSEQ1B @value{CALLSEQ1A}
11605 @set CALLSEQ2B @value{CALLSEQ2A}
11608 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11609 The code can have possible execution paths @value{CALLSEQ1B} or
11610 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11612 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11613 has found. It then finds another possible calling sequcen - that one is
11614 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11615 printed as the @code{reduced:} calling sequence. That one could have many
11616 futher @code{compare:} and @code{reduced:} statements as long as there remain
11617 any non-ambiguous sequence entries.
11619 For the frame of function @code{b} in both cases there are different possible
11620 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11621 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11622 therefore this one is displayed to the user while the ambiguous frames are
11625 There can be also reasons why printing of frame argument values at function
11630 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11631 static void __attribute__((noinline, noclone)) a (int i);
11632 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11633 static void __attribute__((noinline, noclone)) a (int i)
11634 @{ if (i) b (i - 1); else c (0); @}
11635 int main (void) @{ a (5); return 0; @}
11638 #0 c (i=i@@entry=0) at t.c:2
11639 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11640 function "a" at 0x400420 can call itself via tail calls
11641 i=<optimized out>) at t.c:6
11642 #2 0x000000000040036e in main () at t.c:7
11645 @value{GDBN} cannot find out from the inferior state if and how many times did
11646 function @code{a} call itself (via function @code{b}) as these calls would be
11647 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11648 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11649 prints @code{<optimized out>} instead.
11652 @chapter C Preprocessor Macros
11654 Some languages, such as C and C@t{++}, provide a way to define and invoke
11655 ``preprocessor macros'' which expand into strings of tokens.
11656 @value{GDBN} can evaluate expressions containing macro invocations, show
11657 the result of macro expansion, and show a macro's definition, including
11658 where it was defined.
11660 You may need to compile your program specially to provide @value{GDBN}
11661 with information about preprocessor macros. Most compilers do not
11662 include macros in their debugging information, even when you compile
11663 with the @option{-g} flag. @xref{Compilation}.
11665 A program may define a macro at one point, remove that definition later,
11666 and then provide a different definition after that. Thus, at different
11667 points in the program, a macro may have different definitions, or have
11668 no definition at all. If there is a current stack frame, @value{GDBN}
11669 uses the macros in scope at that frame's source code line. Otherwise,
11670 @value{GDBN} uses the macros in scope at the current listing location;
11673 Whenever @value{GDBN} evaluates an expression, it always expands any
11674 macro invocations present in the expression. @value{GDBN} also provides
11675 the following commands for working with macros explicitly.
11679 @kindex macro expand
11680 @cindex macro expansion, showing the results of preprocessor
11681 @cindex preprocessor macro expansion, showing the results of
11682 @cindex expanding preprocessor macros
11683 @item macro expand @var{expression}
11684 @itemx macro exp @var{expression}
11685 Show the results of expanding all preprocessor macro invocations in
11686 @var{expression}. Since @value{GDBN} simply expands macros, but does
11687 not parse the result, @var{expression} need not be a valid expression;
11688 it can be any string of tokens.
11691 @item macro expand-once @var{expression}
11692 @itemx macro exp1 @var{expression}
11693 @cindex expand macro once
11694 @i{(This command is not yet implemented.)} Show the results of
11695 expanding those preprocessor macro invocations that appear explicitly in
11696 @var{expression}. Macro invocations appearing in that expansion are
11697 left unchanged. This command allows you to see the effect of a
11698 particular macro more clearly, without being confused by further
11699 expansions. Since @value{GDBN} simply expands macros, but does not
11700 parse the result, @var{expression} need not be a valid expression; it
11701 can be any string of tokens.
11704 @cindex macro definition, showing
11705 @cindex definition of a macro, showing
11706 @cindex macros, from debug info
11707 @item info macro [-a|-all] [--] @var{macro}
11708 Show the current definition or all definitions of the named @var{macro},
11709 and describe the source location or compiler command-line where that
11710 definition was established. The optional double dash is to signify the end of
11711 argument processing and the beginning of @var{macro} for non C-like macros where
11712 the macro may begin with a hyphen.
11714 @kindex info macros
11715 @item info macros @var{linespec}
11716 Show all macro definitions that are in effect at the location specified
11717 by @var{linespec}, and describe the source location or compiler
11718 command-line where those definitions were established.
11720 @kindex macro define
11721 @cindex user-defined macros
11722 @cindex defining macros interactively
11723 @cindex macros, user-defined
11724 @item macro define @var{macro} @var{replacement-list}
11725 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11726 Introduce a definition for a preprocessor macro named @var{macro},
11727 invocations of which are replaced by the tokens given in
11728 @var{replacement-list}. The first form of this command defines an
11729 ``object-like'' macro, which takes no arguments; the second form
11730 defines a ``function-like'' macro, which takes the arguments given in
11733 A definition introduced by this command is in scope in every
11734 expression evaluated in @value{GDBN}, until it is removed with the
11735 @code{macro undef} command, described below. The definition overrides
11736 all definitions for @var{macro} present in the program being debugged,
11737 as well as any previous user-supplied definition.
11739 @kindex macro undef
11740 @item macro undef @var{macro}
11741 Remove any user-supplied definition for the macro named @var{macro}.
11742 This command only affects definitions provided with the @code{macro
11743 define} command, described above; it cannot remove definitions present
11744 in the program being debugged.
11748 List all the macros defined using the @code{macro define} command.
11751 @cindex macros, example of debugging with
11752 Here is a transcript showing the above commands in action. First, we
11753 show our source files:
11758 #include "sample.h"
11761 #define ADD(x) (M + x)
11766 printf ("Hello, world!\n");
11768 printf ("We're so creative.\n");
11770 printf ("Goodbye, world!\n");
11777 Now, we compile the program using the @sc{gnu} C compiler,
11778 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11779 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11780 and @option{-gdwarf-4}; we recommend always choosing the most recent
11781 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11782 includes information about preprocessor macros in the debugging
11786 $ gcc -gdwarf-2 -g3 sample.c -o sample
11790 Now, we start @value{GDBN} on our sample program:
11794 GNU gdb 2002-05-06-cvs
11795 Copyright 2002 Free Software Foundation, Inc.
11796 GDB is free software, @dots{}
11800 We can expand macros and examine their definitions, even when the
11801 program is not running. @value{GDBN} uses the current listing position
11802 to decide which macro definitions are in scope:
11805 (@value{GDBP}) list main
11808 5 #define ADD(x) (M + x)
11813 10 printf ("Hello, world!\n");
11815 12 printf ("We're so creative.\n");
11816 (@value{GDBP}) info macro ADD
11817 Defined at /home/jimb/gdb/macros/play/sample.c:5
11818 #define ADD(x) (M + x)
11819 (@value{GDBP}) info macro Q
11820 Defined at /home/jimb/gdb/macros/play/sample.h:1
11821 included at /home/jimb/gdb/macros/play/sample.c:2
11823 (@value{GDBP}) macro expand ADD(1)
11824 expands to: (42 + 1)
11825 (@value{GDBP}) macro expand-once ADD(1)
11826 expands to: once (M + 1)
11830 In the example above, note that @code{macro expand-once} expands only
11831 the macro invocation explicit in the original text --- the invocation of
11832 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11833 which was introduced by @code{ADD}.
11835 Once the program is running, @value{GDBN} uses the macro definitions in
11836 force at the source line of the current stack frame:
11839 (@value{GDBP}) break main
11840 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11842 Starting program: /home/jimb/gdb/macros/play/sample
11844 Breakpoint 1, main () at sample.c:10
11845 10 printf ("Hello, world!\n");
11849 At line 10, the definition of the macro @code{N} at line 9 is in force:
11852 (@value{GDBP}) info macro N
11853 Defined at /home/jimb/gdb/macros/play/sample.c:9
11855 (@value{GDBP}) macro expand N Q M
11856 expands to: 28 < 42
11857 (@value{GDBP}) print N Q M
11862 As we step over directives that remove @code{N}'s definition, and then
11863 give it a new definition, @value{GDBN} finds the definition (or lack
11864 thereof) in force at each point:
11867 (@value{GDBP}) next
11869 12 printf ("We're so creative.\n");
11870 (@value{GDBP}) info macro N
11871 The symbol `N' has no definition as a C/C++ preprocessor macro
11872 at /home/jimb/gdb/macros/play/sample.c:12
11873 (@value{GDBP}) next
11875 14 printf ("Goodbye, world!\n");
11876 (@value{GDBP}) info macro N
11877 Defined at /home/jimb/gdb/macros/play/sample.c:13
11879 (@value{GDBP}) macro expand N Q M
11880 expands to: 1729 < 42
11881 (@value{GDBP}) print N Q M
11886 In addition to source files, macros can be defined on the compilation command
11887 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11888 such a way, @value{GDBN} displays the location of their definition as line zero
11889 of the source file submitted to the compiler.
11892 (@value{GDBP}) info macro __STDC__
11893 Defined at /home/jimb/gdb/macros/play/sample.c:0
11900 @chapter Tracepoints
11901 @c This chapter is based on the documentation written by Michael
11902 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11904 @cindex tracepoints
11905 In some applications, it is not feasible for the debugger to interrupt
11906 the program's execution long enough for the developer to learn
11907 anything helpful about its behavior. If the program's correctness
11908 depends on its real-time behavior, delays introduced by a debugger
11909 might cause the program to change its behavior drastically, or perhaps
11910 fail, even when the code itself is correct. It is useful to be able
11911 to observe the program's behavior without interrupting it.
11913 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11914 specify locations in the program, called @dfn{tracepoints}, and
11915 arbitrary expressions to evaluate when those tracepoints are reached.
11916 Later, using the @code{tfind} command, you can examine the values
11917 those expressions had when the program hit the tracepoints. The
11918 expressions may also denote objects in memory---structures or arrays,
11919 for example---whose values @value{GDBN} should record; while visiting
11920 a particular tracepoint, you may inspect those objects as if they were
11921 in memory at that moment. However, because @value{GDBN} records these
11922 values without interacting with you, it can do so quickly and
11923 unobtrusively, hopefully not disturbing the program's behavior.
11925 The tracepoint facility is currently available only for remote
11926 targets. @xref{Targets}. In addition, your remote target must know
11927 how to collect trace data. This functionality is implemented in the
11928 remote stub; however, none of the stubs distributed with @value{GDBN}
11929 support tracepoints as of this writing. The format of the remote
11930 packets used to implement tracepoints are described in @ref{Tracepoint
11933 It is also possible to get trace data from a file, in a manner reminiscent
11934 of corefiles; you specify the filename, and use @code{tfind} to search
11935 through the file. @xref{Trace Files}, for more details.
11937 This chapter describes the tracepoint commands and features.
11940 * Set Tracepoints::
11941 * Analyze Collected Data::
11942 * Tracepoint Variables::
11946 @node Set Tracepoints
11947 @section Commands to Set Tracepoints
11949 Before running such a @dfn{trace experiment}, an arbitrary number of
11950 tracepoints can be set. A tracepoint is actually a special type of
11951 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11952 standard breakpoint commands. For instance, as with breakpoints,
11953 tracepoint numbers are successive integers starting from one, and many
11954 of the commands associated with tracepoints take the tracepoint number
11955 as their argument, to identify which tracepoint to work on.
11957 For each tracepoint, you can specify, in advance, some arbitrary set
11958 of data that you want the target to collect in the trace buffer when
11959 it hits that tracepoint. The collected data can include registers,
11960 local variables, or global data. Later, you can use @value{GDBN}
11961 commands to examine the values these data had at the time the
11962 tracepoint was hit.
11964 Tracepoints do not support every breakpoint feature. Ignore counts on
11965 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11966 commands when they are hit. Tracepoints may not be thread-specific
11969 @cindex fast tracepoints
11970 Some targets may support @dfn{fast tracepoints}, which are inserted in
11971 a different way (such as with a jump instead of a trap), that is
11972 faster but possibly restricted in where they may be installed.
11974 @cindex static tracepoints
11975 @cindex markers, static tracepoints
11976 @cindex probing markers, static tracepoints
11977 Regular and fast tracepoints are dynamic tracing facilities, meaning
11978 that they can be used to insert tracepoints at (almost) any location
11979 in the target. Some targets may also support controlling @dfn{static
11980 tracepoints} from @value{GDBN}. With static tracing, a set of
11981 instrumentation points, also known as @dfn{markers}, are embedded in
11982 the target program, and can be activated or deactivated by name or
11983 address. These are usually placed at locations which facilitate
11984 investigating what the target is actually doing. @value{GDBN}'s
11985 support for static tracing includes being able to list instrumentation
11986 points, and attach them with @value{GDBN} defined high level
11987 tracepoints that expose the whole range of convenience of
11988 @value{GDBN}'s tracepoints support. Namely, support for collecting
11989 registers values and values of global or local (to the instrumentation
11990 point) variables; tracepoint conditions and trace state variables.
11991 The act of installing a @value{GDBN} static tracepoint on an
11992 instrumentation point, or marker, is referred to as @dfn{probing} a
11993 static tracepoint marker.
11995 @code{gdbserver} supports tracepoints on some target systems.
11996 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11998 This section describes commands to set tracepoints and associated
11999 conditions and actions.
12002 * Create and Delete Tracepoints::
12003 * Enable and Disable Tracepoints::
12004 * Tracepoint Passcounts::
12005 * Tracepoint Conditions::
12006 * Trace State Variables::
12007 * Tracepoint Actions::
12008 * Listing Tracepoints::
12009 * Listing Static Tracepoint Markers::
12010 * Starting and Stopping Trace Experiments::
12011 * Tracepoint Restrictions::
12014 @node Create and Delete Tracepoints
12015 @subsection Create and Delete Tracepoints
12018 @cindex set tracepoint
12020 @item trace @var{location}
12021 The @code{trace} command is very similar to the @code{break} command.
12022 Its argument @var{location} can be a source line, a function name, or
12023 an address in the target program. @xref{Specify Location}. The
12024 @code{trace} command defines a tracepoint, which is a point in the
12025 target program where the debugger will briefly stop, collect some
12026 data, and then allow the program to continue. Setting a tracepoint or
12027 changing its actions takes effect immediately if the remote stub
12028 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12030 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12031 these changes don't take effect until the next @code{tstart}
12032 command, and once a trace experiment is running, further changes will
12033 not have any effect until the next trace experiment starts. In addition,
12034 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12035 address is not yet resolved. (This is similar to pending breakpoints.)
12036 Pending tracepoints are not downloaded to the target and not installed
12037 until they are resolved. The resolution of pending tracepoints requires
12038 @value{GDBN} support---when debugging with the remote target, and
12039 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12040 tracing}), pending tracepoints can not be resolved (and downloaded to
12041 the remote stub) while @value{GDBN} is disconnected.
12043 Here are some examples of using the @code{trace} command:
12046 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12048 (@value{GDBP}) @b{trace +2} // 2 lines forward
12050 (@value{GDBP}) @b{trace my_function} // first source line of function
12052 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12054 (@value{GDBP}) @b{trace *0x2117c4} // an address
12058 You can abbreviate @code{trace} as @code{tr}.
12060 @item trace @var{location} if @var{cond}
12061 Set a tracepoint with condition @var{cond}; evaluate the expression
12062 @var{cond} each time the tracepoint is reached, and collect data only
12063 if the value is nonzero---that is, if @var{cond} evaluates as true.
12064 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12065 information on tracepoint conditions.
12067 @item ftrace @var{location} [ if @var{cond} ]
12068 @cindex set fast tracepoint
12069 @cindex fast tracepoints, setting
12071 The @code{ftrace} command sets a fast tracepoint. For targets that
12072 support them, fast tracepoints will use a more efficient but possibly
12073 less general technique to trigger data collection, such as a jump
12074 instruction instead of a trap, or some sort of hardware support. It
12075 may not be possible to create a fast tracepoint at the desired
12076 location, in which case the command will exit with an explanatory
12079 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12082 On 32-bit x86-architecture systems, fast tracepoints normally need to
12083 be placed at an instruction that is 5 bytes or longer, but can be
12084 placed at 4-byte instructions if the low 64K of memory of the target
12085 program is available to install trampolines. Some Unix-type systems,
12086 such as @sc{gnu}/Linux, exclude low addresses from the program's
12087 address space; but for instance with the Linux kernel it is possible
12088 to let @value{GDBN} use this area by doing a @command{sysctl} command
12089 to set the @code{mmap_min_addr} kernel parameter, as in
12092 sudo sysctl -w vm.mmap_min_addr=32768
12096 which sets the low address to 32K, which leaves plenty of room for
12097 trampolines. The minimum address should be set to a page boundary.
12099 @item strace @var{location} [ if @var{cond} ]
12100 @cindex set static tracepoint
12101 @cindex static tracepoints, setting
12102 @cindex probe static tracepoint marker
12104 The @code{strace} command sets a static tracepoint. For targets that
12105 support it, setting a static tracepoint probes a static
12106 instrumentation point, or marker, found at @var{location}. It may not
12107 be possible to set a static tracepoint at the desired location, in
12108 which case the command will exit with an explanatory message.
12110 @value{GDBN} handles arguments to @code{strace} exactly as for
12111 @code{trace}, with the addition that the user can also specify
12112 @code{-m @var{marker}} as @var{location}. This probes the marker
12113 identified by the @var{marker} string identifier. This identifier
12114 depends on the static tracepoint backend library your program is
12115 using. You can find all the marker identifiers in the @samp{ID} field
12116 of the @code{info static-tracepoint-markers} command output.
12117 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12118 Markers}. For example, in the following small program using the UST
12124 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12129 the marker id is composed of joining the first two arguments to the
12130 @code{trace_mark} call with a slash, which translates to:
12133 (@value{GDBP}) info static-tracepoint-markers
12134 Cnt Enb ID Address What
12135 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12141 so you may probe the marker above with:
12144 (@value{GDBP}) strace -m ust/bar33
12147 Static tracepoints accept an extra collect action --- @code{collect
12148 $_sdata}. This collects arbitrary user data passed in the probe point
12149 call to the tracing library. In the UST example above, you'll see
12150 that the third argument to @code{trace_mark} is a printf-like format
12151 string. The user data is then the result of running that formating
12152 string against the following arguments. Note that @code{info
12153 static-tracepoint-markers} command output lists that format string in
12154 the @samp{Data:} field.
12156 You can inspect this data when analyzing the trace buffer, by printing
12157 the $_sdata variable like any other variable available to
12158 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12161 @cindex last tracepoint number
12162 @cindex recent tracepoint number
12163 @cindex tracepoint number
12164 The convenience variable @code{$tpnum} records the tracepoint number
12165 of the most recently set tracepoint.
12167 @kindex delete tracepoint
12168 @cindex tracepoint deletion
12169 @item delete tracepoint @r{[}@var{num}@r{]}
12170 Permanently delete one or more tracepoints. With no argument, the
12171 default is to delete all tracepoints. Note that the regular
12172 @code{delete} command can remove tracepoints also.
12177 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12179 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12183 You can abbreviate this command as @code{del tr}.
12186 @node Enable and Disable Tracepoints
12187 @subsection Enable and Disable Tracepoints
12189 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12192 @kindex disable tracepoint
12193 @item disable tracepoint @r{[}@var{num}@r{]}
12194 Disable tracepoint @var{num}, or all tracepoints if no argument
12195 @var{num} is given. A disabled tracepoint will have no effect during
12196 a trace experiment, but it is not forgotten. You can re-enable
12197 a disabled tracepoint using the @code{enable tracepoint} command.
12198 If the command is issued during a trace experiment and the debug target
12199 has support for disabling tracepoints during a trace experiment, then the
12200 change will be effective immediately. Otherwise, it will be applied to the
12201 next trace experiment.
12203 @kindex enable tracepoint
12204 @item enable tracepoint @r{[}@var{num}@r{]}
12205 Enable tracepoint @var{num}, or all tracepoints. If this command is
12206 issued during a trace experiment and the debug target supports enabling
12207 tracepoints during a trace experiment, then the enabled tracepoints will
12208 become effective immediately. Otherwise, they will become effective the
12209 next time a trace experiment is run.
12212 @node Tracepoint Passcounts
12213 @subsection Tracepoint Passcounts
12217 @cindex tracepoint pass count
12218 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12219 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12220 automatically stop a trace experiment. If a tracepoint's passcount is
12221 @var{n}, then the trace experiment will be automatically stopped on
12222 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12223 @var{num} is not specified, the @code{passcount} command sets the
12224 passcount of the most recently defined tracepoint. If no passcount is
12225 given, the trace experiment will run until stopped explicitly by the
12231 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12232 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12234 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12235 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12236 (@value{GDBP}) @b{trace foo}
12237 (@value{GDBP}) @b{pass 3}
12238 (@value{GDBP}) @b{trace bar}
12239 (@value{GDBP}) @b{pass 2}
12240 (@value{GDBP}) @b{trace baz}
12241 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12242 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12243 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12244 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12248 @node Tracepoint Conditions
12249 @subsection Tracepoint Conditions
12250 @cindex conditional tracepoints
12251 @cindex tracepoint conditions
12253 The simplest sort of tracepoint collects data every time your program
12254 reaches a specified place. You can also specify a @dfn{condition} for
12255 a tracepoint. A condition is just a Boolean expression in your
12256 programming language (@pxref{Expressions, ,Expressions}). A
12257 tracepoint with a condition evaluates the expression each time your
12258 program reaches it, and data collection happens only if the condition
12261 Tracepoint conditions can be specified when a tracepoint is set, by
12262 using @samp{if} in the arguments to the @code{trace} command.
12263 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12264 also be set or changed at any time with the @code{condition} command,
12265 just as with breakpoints.
12267 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12268 the conditional expression itself. Instead, @value{GDBN} encodes the
12269 expression into an agent expression (@pxref{Agent Expressions})
12270 suitable for execution on the target, independently of @value{GDBN}.
12271 Global variables become raw memory locations, locals become stack
12272 accesses, and so forth.
12274 For instance, suppose you have a function that is usually called
12275 frequently, but should not be called after an error has occurred. You
12276 could use the following tracepoint command to collect data about calls
12277 of that function that happen while the error code is propagating
12278 through the program; an unconditional tracepoint could end up
12279 collecting thousands of useless trace frames that you would have to
12283 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12286 @node Trace State Variables
12287 @subsection Trace State Variables
12288 @cindex trace state variables
12290 A @dfn{trace state variable} is a special type of variable that is
12291 created and managed by target-side code. The syntax is the same as
12292 that for GDB's convenience variables (a string prefixed with ``$''),
12293 but they are stored on the target. They must be created explicitly,
12294 using a @code{tvariable} command. They are always 64-bit signed
12297 Trace state variables are remembered by @value{GDBN}, and downloaded
12298 to the target along with tracepoint information when the trace
12299 experiment starts. There are no intrinsic limits on the number of
12300 trace state variables, beyond memory limitations of the target.
12302 @cindex convenience variables, and trace state variables
12303 Although trace state variables are managed by the target, you can use
12304 them in print commands and expressions as if they were convenience
12305 variables; @value{GDBN} will get the current value from the target
12306 while the trace experiment is running. Trace state variables share
12307 the same namespace as other ``$'' variables, which means that you
12308 cannot have trace state variables with names like @code{$23} or
12309 @code{$pc}, nor can you have a trace state variable and a convenience
12310 variable with the same name.
12314 @item tvariable $@var{name} [ = @var{expression} ]
12316 The @code{tvariable} command creates a new trace state variable named
12317 @code{$@var{name}}, and optionally gives it an initial value of
12318 @var{expression}. The @var{expression} is evaluated when this command is
12319 entered; the result will be converted to an integer if possible,
12320 otherwise @value{GDBN} will report an error. A subsequent
12321 @code{tvariable} command specifying the same name does not create a
12322 variable, but instead assigns the supplied initial value to the
12323 existing variable of that name, overwriting any previous initial
12324 value. The default initial value is 0.
12326 @item info tvariables
12327 @kindex info tvariables
12328 List all the trace state variables along with their initial values.
12329 Their current values may also be displayed, if the trace experiment is
12332 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12333 @kindex delete tvariable
12334 Delete the given trace state variables, or all of them if no arguments
12339 @node Tracepoint Actions
12340 @subsection Tracepoint Action Lists
12344 @cindex tracepoint actions
12345 @item actions @r{[}@var{num}@r{]}
12346 This command will prompt for a list of actions to be taken when the
12347 tracepoint is hit. If the tracepoint number @var{num} is not
12348 specified, this command sets the actions for the one that was most
12349 recently defined (so that you can define a tracepoint and then say
12350 @code{actions} without bothering about its number). You specify the
12351 actions themselves on the following lines, one action at a time, and
12352 terminate the actions list with a line containing just @code{end}. So
12353 far, the only defined actions are @code{collect}, @code{teval}, and
12354 @code{while-stepping}.
12356 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12357 Commands, ,Breakpoint Command Lists}), except that only the defined
12358 actions are allowed; any other @value{GDBN} command is rejected.
12360 @cindex remove actions from a tracepoint
12361 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12362 and follow it immediately with @samp{end}.
12365 (@value{GDBP}) @b{collect @var{data}} // collect some data
12367 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12369 (@value{GDBP}) @b{end} // signals the end of actions.
12372 In the following example, the action list begins with @code{collect}
12373 commands indicating the things to be collected when the tracepoint is
12374 hit. Then, in order to single-step and collect additional data
12375 following the tracepoint, a @code{while-stepping} command is used,
12376 followed by the list of things to be collected after each step in a
12377 sequence of single steps. The @code{while-stepping} command is
12378 terminated by its own separate @code{end} command. Lastly, the action
12379 list is terminated by an @code{end} command.
12382 (@value{GDBP}) @b{trace foo}
12383 (@value{GDBP}) @b{actions}
12384 Enter actions for tracepoint 1, one per line:
12387 > while-stepping 12
12388 > collect $pc, arr[i]
12393 @kindex collect @r{(tracepoints)}
12394 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12395 Collect values of the given expressions when the tracepoint is hit.
12396 This command accepts a comma-separated list of any valid expressions.
12397 In addition to global, static, or local variables, the following
12398 special arguments are supported:
12402 Collect all registers.
12405 Collect all function arguments.
12408 Collect all local variables.
12411 Collect the return address. This is helpful if you want to see more
12415 Collects the number of arguments from the static probe at which the
12416 tracepoint is located.
12417 @xref{Static Probe Points}.
12419 @item $_probe_arg@var{n}
12420 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12421 from the static probe at which the tracepoint is located.
12422 @xref{Static Probe Points}.
12425 @vindex $_sdata@r{, collect}
12426 Collect static tracepoint marker specific data. Only available for
12427 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12428 Lists}. On the UST static tracepoints library backend, an
12429 instrumentation point resembles a @code{printf} function call. The
12430 tracing library is able to collect user specified data formatted to a
12431 character string using the format provided by the programmer that
12432 instrumented the program. Other backends have similar mechanisms.
12433 Here's an example of a UST marker call:
12436 const char master_name[] = "$your_name";
12437 trace_mark(channel1, marker1, "hello %s", master_name)
12440 In this case, collecting @code{$_sdata} collects the string
12441 @samp{hello $yourname}. When analyzing the trace buffer, you can
12442 inspect @samp{$_sdata} like any other variable available to
12446 You can give several consecutive @code{collect} commands, each one
12447 with a single argument, or one @code{collect} command with several
12448 arguments separated by commas; the effect is the same.
12450 The optional @var{mods} changes the usual handling of the arguments.
12451 @code{s} requests that pointers to chars be handled as strings, in
12452 particular collecting the contents of the memory being pointed at, up
12453 to the first zero. The upper bound is by default the value of the
12454 @code{print elements} variable; if @code{s} is followed by a decimal
12455 number, that is the upper bound instead. So for instance
12456 @samp{collect/s25 mystr} collects as many as 25 characters at
12459 The command @code{info scope} (@pxref{Symbols, info scope}) is
12460 particularly useful for figuring out what data to collect.
12462 @kindex teval @r{(tracepoints)}
12463 @item teval @var{expr1}, @var{expr2}, @dots{}
12464 Evaluate the given expressions when the tracepoint is hit. This
12465 command accepts a comma-separated list of expressions. The results
12466 are discarded, so this is mainly useful for assigning values to trace
12467 state variables (@pxref{Trace State Variables}) without adding those
12468 values to the trace buffer, as would be the case if the @code{collect}
12471 @kindex while-stepping @r{(tracepoints)}
12472 @item while-stepping @var{n}
12473 Perform @var{n} single-step instruction traces after the tracepoint,
12474 collecting new data after each step. The @code{while-stepping}
12475 command is followed by the list of what to collect while stepping
12476 (followed by its own @code{end} command):
12479 > while-stepping 12
12480 > collect $regs, myglobal
12486 Note that @code{$pc} is not automatically collected by
12487 @code{while-stepping}; you need to explicitly collect that register if
12488 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12491 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12492 @kindex set default-collect
12493 @cindex default collection action
12494 This variable is a list of expressions to collect at each tracepoint
12495 hit. It is effectively an additional @code{collect} action prepended
12496 to every tracepoint action list. The expressions are parsed
12497 individually for each tracepoint, so for instance a variable named
12498 @code{xyz} may be interpreted as a global for one tracepoint, and a
12499 local for another, as appropriate to the tracepoint's location.
12501 @item show default-collect
12502 @kindex show default-collect
12503 Show the list of expressions that are collected by default at each
12508 @node Listing Tracepoints
12509 @subsection Listing Tracepoints
12512 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12513 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12514 @cindex information about tracepoints
12515 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12516 Display information about the tracepoint @var{num}. If you don't
12517 specify a tracepoint number, displays information about all the
12518 tracepoints defined so far. The format is similar to that used for
12519 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12520 command, simply restricting itself to tracepoints.
12522 A tracepoint's listing may include additional information specific to
12527 its passcount as given by the @code{passcount @var{n}} command
12530 the state about installed on target of each location
12534 (@value{GDBP}) @b{info trace}
12535 Num Type Disp Enb Address What
12536 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12538 collect globfoo, $regs
12543 2 tracepoint keep y <MULTIPLE>
12545 2.1 y 0x0804859c in func4 at change-loc.h:35
12546 installed on target
12547 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12548 installed on target
12549 2.3 y <PENDING> set_tracepoint
12550 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12551 not installed on target
12556 This command can be abbreviated @code{info tp}.
12559 @node Listing Static Tracepoint Markers
12560 @subsection Listing Static Tracepoint Markers
12563 @kindex info static-tracepoint-markers
12564 @cindex information about static tracepoint markers
12565 @item info static-tracepoint-markers
12566 Display information about all static tracepoint markers defined in the
12569 For each marker, the following columns are printed:
12573 An incrementing counter, output to help readability. This is not a
12576 The marker ID, as reported by the target.
12577 @item Enabled or Disabled
12578 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12579 that are not enabled.
12581 Where the marker is in your program, as a memory address.
12583 Where the marker is in the source for your program, as a file and line
12584 number. If the debug information included in the program does not
12585 allow @value{GDBN} to locate the source of the marker, this column
12586 will be left blank.
12590 In addition, the following information may be printed for each marker:
12594 User data passed to the tracing library by the marker call. In the
12595 UST backend, this is the format string passed as argument to the
12597 @item Static tracepoints probing the marker
12598 The list of static tracepoints attached to the marker.
12602 (@value{GDBP}) info static-tracepoint-markers
12603 Cnt ID Enb Address What
12604 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12605 Data: number1 %d number2 %d
12606 Probed by static tracepoints: #2
12607 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12613 @node Starting and Stopping Trace Experiments
12614 @subsection Starting and Stopping Trace Experiments
12617 @kindex tstart [ @var{notes} ]
12618 @cindex start a new trace experiment
12619 @cindex collected data discarded
12621 This command starts the trace experiment, and begins collecting data.
12622 It has the side effect of discarding all the data collected in the
12623 trace buffer during the previous trace experiment. If any arguments
12624 are supplied, they are taken as a note and stored with the trace
12625 experiment's state. The notes may be arbitrary text, and are
12626 especially useful with disconnected tracing in a multi-user context;
12627 the notes can explain what the trace is doing, supply user contact
12628 information, and so forth.
12630 @kindex tstop [ @var{notes} ]
12631 @cindex stop a running trace experiment
12633 This command stops the trace experiment. If any arguments are
12634 supplied, they are recorded with the experiment as a note. This is
12635 useful if you are stopping a trace started by someone else, for
12636 instance if the trace is interfering with the system's behavior and
12637 needs to be stopped quickly.
12639 @strong{Note}: a trace experiment and data collection may stop
12640 automatically if any tracepoint's passcount is reached
12641 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12644 @cindex status of trace data collection
12645 @cindex trace experiment, status of
12647 This command displays the status of the current trace data
12651 Here is an example of the commands we described so far:
12654 (@value{GDBP}) @b{trace gdb_c_test}
12655 (@value{GDBP}) @b{actions}
12656 Enter actions for tracepoint #1, one per line.
12657 > collect $regs,$locals,$args
12658 > while-stepping 11
12662 (@value{GDBP}) @b{tstart}
12663 [time passes @dots{}]
12664 (@value{GDBP}) @b{tstop}
12667 @anchor{disconnected tracing}
12668 @cindex disconnected tracing
12669 You can choose to continue running the trace experiment even if
12670 @value{GDBN} disconnects from the target, voluntarily or
12671 involuntarily. For commands such as @code{detach}, the debugger will
12672 ask what you want to do with the trace. But for unexpected
12673 terminations (@value{GDBN} crash, network outage), it would be
12674 unfortunate to lose hard-won trace data, so the variable
12675 @code{disconnected-tracing} lets you decide whether the trace should
12676 continue running without @value{GDBN}.
12679 @item set disconnected-tracing on
12680 @itemx set disconnected-tracing off
12681 @kindex set disconnected-tracing
12682 Choose whether a tracing run should continue to run if @value{GDBN}
12683 has disconnected from the target. Note that @code{detach} or
12684 @code{quit} will ask you directly what to do about a running trace no
12685 matter what this variable's setting, so the variable is mainly useful
12686 for handling unexpected situations, such as loss of the network.
12688 @item show disconnected-tracing
12689 @kindex show disconnected-tracing
12690 Show the current choice for disconnected tracing.
12694 When you reconnect to the target, the trace experiment may or may not
12695 still be running; it might have filled the trace buffer in the
12696 meantime, or stopped for one of the other reasons. If it is running,
12697 it will continue after reconnection.
12699 Upon reconnection, the target will upload information about the
12700 tracepoints in effect. @value{GDBN} will then compare that
12701 information to the set of tracepoints currently defined, and attempt
12702 to match them up, allowing for the possibility that the numbers may
12703 have changed due to creation and deletion in the meantime. If one of
12704 the target's tracepoints does not match any in @value{GDBN}, the
12705 debugger will create a new tracepoint, so that you have a number with
12706 which to specify that tracepoint. This matching-up process is
12707 necessarily heuristic, and it may result in useless tracepoints being
12708 created; you may simply delete them if they are of no use.
12710 @cindex circular trace buffer
12711 If your target agent supports a @dfn{circular trace buffer}, then you
12712 can run a trace experiment indefinitely without filling the trace
12713 buffer; when space runs out, the agent deletes already-collected trace
12714 frames, oldest first, until there is enough room to continue
12715 collecting. This is especially useful if your tracepoints are being
12716 hit too often, and your trace gets terminated prematurely because the
12717 buffer is full. To ask for a circular trace buffer, simply set
12718 @samp{circular-trace-buffer} to on. You can set this at any time,
12719 including during tracing; if the agent can do it, it will change
12720 buffer handling on the fly, otherwise it will not take effect until
12724 @item set circular-trace-buffer on
12725 @itemx set circular-trace-buffer off
12726 @kindex set circular-trace-buffer
12727 Choose whether a tracing run should use a linear or circular buffer
12728 for trace data. A linear buffer will not lose any trace data, but may
12729 fill up prematurely, while a circular buffer will discard old trace
12730 data, but it will have always room for the latest tracepoint hits.
12732 @item show circular-trace-buffer
12733 @kindex show circular-trace-buffer
12734 Show the current choice for the trace buffer. Note that this may not
12735 match the agent's current buffer handling, nor is it guaranteed to
12736 match the setting that might have been in effect during a past run,
12737 for instance if you are looking at frames from a trace file.
12742 @item set trace-buffer-size @var{n}
12743 @itemx set trace-buffer-size unlimited
12744 @kindex set trace-buffer-size
12745 Request that the target use a trace buffer of @var{n} bytes. Not all
12746 targets will honor the request; they may have a compiled-in size for
12747 the trace buffer, or some other limitation. Set to a value of
12748 @code{unlimited} or @code{-1} to let the target use whatever size it
12749 likes. This is also the default.
12751 @item show trace-buffer-size
12752 @kindex show trace-buffer-size
12753 Show the current requested size for the trace buffer. Note that this
12754 will only match the actual size if the target supports size-setting,
12755 and was able to handle the requested size. For instance, if the
12756 target can only change buffer size between runs, this variable will
12757 not reflect the change until the next run starts. Use @code{tstatus}
12758 to get a report of the actual buffer size.
12762 @item set trace-user @var{text}
12763 @kindex set trace-user
12765 @item show trace-user
12766 @kindex show trace-user
12768 @item set trace-notes @var{text}
12769 @kindex set trace-notes
12770 Set the trace run's notes.
12772 @item show trace-notes
12773 @kindex show trace-notes
12774 Show the trace run's notes.
12776 @item set trace-stop-notes @var{text}
12777 @kindex set trace-stop-notes
12778 Set the trace run's stop notes. The handling of the note is as for
12779 @code{tstop} arguments; the set command is convenient way to fix a
12780 stop note that is mistaken or incomplete.
12782 @item show trace-stop-notes
12783 @kindex show trace-stop-notes
12784 Show the trace run's stop notes.
12788 @node Tracepoint Restrictions
12789 @subsection Tracepoint Restrictions
12791 @cindex tracepoint restrictions
12792 There are a number of restrictions on the use of tracepoints. As
12793 described above, tracepoint data gathering occurs on the target
12794 without interaction from @value{GDBN}. Thus the full capabilities of
12795 the debugger are not available during data gathering, and then at data
12796 examination time, you will be limited by only having what was
12797 collected. The following items describe some common problems, but it
12798 is not exhaustive, and you may run into additional difficulties not
12804 Tracepoint expressions are intended to gather objects (lvalues). Thus
12805 the full flexibility of GDB's expression evaluator is not available.
12806 You cannot call functions, cast objects to aggregate types, access
12807 convenience variables or modify values (except by assignment to trace
12808 state variables). Some language features may implicitly call
12809 functions (for instance Objective-C fields with accessors), and therefore
12810 cannot be collected either.
12813 Collection of local variables, either individually or in bulk with
12814 @code{$locals} or @code{$args}, during @code{while-stepping} may
12815 behave erratically. The stepping action may enter a new scope (for
12816 instance by stepping into a function), or the location of the variable
12817 may change (for instance it is loaded into a register). The
12818 tracepoint data recorded uses the location information for the
12819 variables that is correct for the tracepoint location. When the
12820 tracepoint is created, it is not possible, in general, to determine
12821 where the steps of a @code{while-stepping} sequence will advance the
12822 program---particularly if a conditional branch is stepped.
12825 Collection of an incompletely-initialized or partially-destroyed object
12826 may result in something that @value{GDBN} cannot display, or displays
12827 in a misleading way.
12830 When @value{GDBN} displays a pointer to character it automatically
12831 dereferences the pointer to also display characters of the string
12832 being pointed to. However, collecting the pointer during tracing does
12833 not automatically collect the string. You need to explicitly
12834 dereference the pointer and provide size information if you want to
12835 collect not only the pointer, but the memory pointed to. For example,
12836 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12840 It is not possible to collect a complete stack backtrace at a
12841 tracepoint. Instead, you may collect the registers and a few hundred
12842 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12843 (adjust to use the name of the actual stack pointer register on your
12844 target architecture, and the amount of stack you wish to capture).
12845 Then the @code{backtrace} command will show a partial backtrace when
12846 using a trace frame. The number of stack frames that can be examined
12847 depends on the sizes of the frames in the collected stack. Note that
12848 if you ask for a block so large that it goes past the bottom of the
12849 stack, the target agent may report an error trying to read from an
12853 If you do not collect registers at a tracepoint, @value{GDBN} can
12854 infer that the value of @code{$pc} must be the same as the address of
12855 the tracepoint and use that when you are looking at a trace frame
12856 for that tracepoint. However, this cannot work if the tracepoint has
12857 multiple locations (for instance if it was set in a function that was
12858 inlined), or if it has a @code{while-stepping} loop. In those cases
12859 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12864 @node Analyze Collected Data
12865 @section Using the Collected Data
12867 After the tracepoint experiment ends, you use @value{GDBN} commands
12868 for examining the trace data. The basic idea is that each tracepoint
12869 collects a trace @dfn{snapshot} every time it is hit and another
12870 snapshot every time it single-steps. All these snapshots are
12871 consecutively numbered from zero and go into a buffer, and you can
12872 examine them later. The way you examine them is to @dfn{focus} on a
12873 specific trace snapshot. When the remote stub is focused on a trace
12874 snapshot, it will respond to all @value{GDBN} requests for memory and
12875 registers by reading from the buffer which belongs to that snapshot,
12876 rather than from @emph{real} memory or registers of the program being
12877 debugged. This means that @strong{all} @value{GDBN} commands
12878 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12879 behave as if we were currently debugging the program state as it was
12880 when the tracepoint occurred. Any requests for data that are not in
12881 the buffer will fail.
12884 * tfind:: How to select a trace snapshot
12885 * tdump:: How to display all data for a snapshot
12886 * save tracepoints:: How to save tracepoints for a future run
12890 @subsection @code{tfind @var{n}}
12893 @cindex select trace snapshot
12894 @cindex find trace snapshot
12895 The basic command for selecting a trace snapshot from the buffer is
12896 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12897 counting from zero. If no argument @var{n} is given, the next
12898 snapshot is selected.
12900 Here are the various forms of using the @code{tfind} command.
12904 Find the first snapshot in the buffer. This is a synonym for
12905 @code{tfind 0} (since 0 is the number of the first snapshot).
12908 Stop debugging trace snapshots, resume @emph{live} debugging.
12911 Same as @samp{tfind none}.
12914 No argument means find the next trace snapshot.
12917 Find the previous trace snapshot before the current one. This permits
12918 retracing earlier steps.
12920 @item tfind tracepoint @var{num}
12921 Find the next snapshot associated with tracepoint @var{num}. Search
12922 proceeds forward from the last examined trace snapshot. If no
12923 argument @var{num} is given, it means find the next snapshot collected
12924 for the same tracepoint as the current snapshot.
12926 @item tfind pc @var{addr}
12927 Find the next snapshot associated with the value @var{addr} of the
12928 program counter. Search proceeds forward from the last examined trace
12929 snapshot. If no argument @var{addr} is given, it means find the next
12930 snapshot with the same value of PC as the current snapshot.
12932 @item tfind outside @var{addr1}, @var{addr2}
12933 Find the next snapshot whose PC is outside the given range of
12934 addresses (exclusive).
12936 @item tfind range @var{addr1}, @var{addr2}
12937 Find the next snapshot whose PC is between @var{addr1} and
12938 @var{addr2} (inclusive).
12940 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12941 Find the next snapshot associated with the source line @var{n}. If
12942 the optional argument @var{file} is given, refer to line @var{n} in
12943 that source file. Search proceeds forward from the last examined
12944 trace snapshot. If no argument @var{n} is given, it means find the
12945 next line other than the one currently being examined; thus saying
12946 @code{tfind line} repeatedly can appear to have the same effect as
12947 stepping from line to line in a @emph{live} debugging session.
12950 The default arguments for the @code{tfind} commands are specifically
12951 designed to make it easy to scan through the trace buffer. For
12952 instance, @code{tfind} with no argument selects the next trace
12953 snapshot, and @code{tfind -} with no argument selects the previous
12954 trace snapshot. So, by giving one @code{tfind} command, and then
12955 simply hitting @key{RET} repeatedly you can examine all the trace
12956 snapshots in order. Or, by saying @code{tfind -} and then hitting
12957 @key{RET} repeatedly you can examine the snapshots in reverse order.
12958 The @code{tfind line} command with no argument selects the snapshot
12959 for the next source line executed. The @code{tfind pc} command with
12960 no argument selects the next snapshot with the same program counter
12961 (PC) as the current frame. The @code{tfind tracepoint} command with
12962 no argument selects the next trace snapshot collected by the same
12963 tracepoint as the current one.
12965 In addition to letting you scan through the trace buffer manually,
12966 these commands make it easy to construct @value{GDBN} scripts that
12967 scan through the trace buffer and print out whatever collected data
12968 you are interested in. Thus, if we want to examine the PC, FP, and SP
12969 registers from each trace frame in the buffer, we can say this:
12972 (@value{GDBP}) @b{tfind start}
12973 (@value{GDBP}) @b{while ($trace_frame != -1)}
12974 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12975 $trace_frame, $pc, $sp, $fp
12979 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12980 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12981 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12982 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12983 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12984 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12985 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12986 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12987 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12988 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12989 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12992 Or, if we want to examine the variable @code{X} at each source line in
12996 (@value{GDBP}) @b{tfind start}
12997 (@value{GDBP}) @b{while ($trace_frame != -1)}
12998 > printf "Frame %d, X == %d\n", $trace_frame, X
13008 @subsection @code{tdump}
13010 @cindex dump all data collected at tracepoint
13011 @cindex tracepoint data, display
13013 This command takes no arguments. It prints all the data collected at
13014 the current trace snapshot.
13017 (@value{GDBP}) @b{trace 444}
13018 (@value{GDBP}) @b{actions}
13019 Enter actions for tracepoint #2, one per line:
13020 > collect $regs, $locals, $args, gdb_long_test
13023 (@value{GDBP}) @b{tstart}
13025 (@value{GDBP}) @b{tfind line 444}
13026 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13028 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13030 (@value{GDBP}) @b{tdump}
13031 Data collected at tracepoint 2, trace frame 1:
13032 d0 0xc4aa0085 -995491707
13036 d4 0x71aea3d 119204413
13039 d7 0x380035 3670069
13040 a0 0x19e24a 1696330
13041 a1 0x3000668 50333288
13043 a3 0x322000 3284992
13044 a4 0x3000698 50333336
13045 a5 0x1ad3cc 1758156
13046 fp 0x30bf3c 0x30bf3c
13047 sp 0x30bf34 0x30bf34
13049 pc 0x20b2c8 0x20b2c8
13053 p = 0x20e5b4 "gdb-test"
13060 gdb_long_test = 17 '\021'
13065 @code{tdump} works by scanning the tracepoint's current collection
13066 actions and printing the value of each expression listed. So
13067 @code{tdump} can fail, if after a run, you change the tracepoint's
13068 actions to mention variables that were not collected during the run.
13070 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13071 uses the collected value of @code{$pc} to distinguish between trace
13072 frames that were collected at the tracepoint hit, and frames that were
13073 collected while stepping. This allows it to correctly choose whether
13074 to display the basic list of collections, or the collections from the
13075 body of the while-stepping loop. However, if @code{$pc} was not collected,
13076 then @code{tdump} will always attempt to dump using the basic collection
13077 list, and may fail if a while-stepping frame does not include all the
13078 same data that is collected at the tracepoint hit.
13079 @c This is getting pretty arcane, example would be good.
13081 @node save tracepoints
13082 @subsection @code{save tracepoints @var{filename}}
13083 @kindex save tracepoints
13084 @kindex save-tracepoints
13085 @cindex save tracepoints for future sessions
13087 This command saves all current tracepoint definitions together with
13088 their actions and passcounts, into a file @file{@var{filename}}
13089 suitable for use in a later debugging session. To read the saved
13090 tracepoint definitions, use the @code{source} command (@pxref{Command
13091 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13092 alias for @w{@code{save tracepoints}}
13094 @node Tracepoint Variables
13095 @section Convenience Variables for Tracepoints
13096 @cindex tracepoint variables
13097 @cindex convenience variables for tracepoints
13100 @vindex $trace_frame
13101 @item (int) $trace_frame
13102 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13103 snapshot is selected.
13105 @vindex $tracepoint
13106 @item (int) $tracepoint
13107 The tracepoint for the current trace snapshot.
13109 @vindex $trace_line
13110 @item (int) $trace_line
13111 The line number for the current trace snapshot.
13113 @vindex $trace_file
13114 @item (char []) $trace_file
13115 The source file for the current trace snapshot.
13117 @vindex $trace_func
13118 @item (char []) $trace_func
13119 The name of the function containing @code{$tracepoint}.
13122 Note: @code{$trace_file} is not suitable for use in @code{printf},
13123 use @code{output} instead.
13125 Here's a simple example of using these convenience variables for
13126 stepping through all the trace snapshots and printing some of their
13127 data. Note that these are not the same as trace state variables,
13128 which are managed by the target.
13131 (@value{GDBP}) @b{tfind start}
13133 (@value{GDBP}) @b{while $trace_frame != -1}
13134 > output $trace_file
13135 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13141 @section Using Trace Files
13142 @cindex trace files
13144 In some situations, the target running a trace experiment may no
13145 longer be available; perhaps it crashed, or the hardware was needed
13146 for a different activity. To handle these cases, you can arrange to
13147 dump the trace data into a file, and later use that file as a source
13148 of trace data, via the @code{target tfile} command.
13153 @item tsave [ -r ] @var{filename}
13154 @itemx tsave [-ctf] @var{dirname}
13155 Save the trace data to @var{filename}. By default, this command
13156 assumes that @var{filename} refers to the host filesystem, so if
13157 necessary @value{GDBN} will copy raw trace data up from the target and
13158 then save it. If the target supports it, you can also supply the
13159 optional argument @code{-r} (``remote'') to direct the target to save
13160 the data directly into @var{filename} in its own filesystem, which may be
13161 more efficient if the trace buffer is very large. (Note, however, that
13162 @code{target tfile} can only read from files accessible to the host.)
13163 By default, this command will save trace frame in tfile format.
13164 You can supply the optional argument @code{-ctf} to save date in CTF
13165 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13166 that can be shared by multiple debugging and tracing tools. Please go to
13167 @indicateurl{http://www.efficios.com/ctf} to get more information.
13169 @kindex target tfile
13173 @item target tfile @var{filename}
13174 @itemx target ctf @var{dirname}
13175 Use the file named @var{filename} or directory named @var{dirname} as
13176 a source of trace data. Commands that examine data work as they do with
13177 a live target, but it is not possible to run any new trace experiments.
13178 @code{tstatus} will report the state of the trace run at the moment
13179 the data was saved, as well as the current trace frame you are examining.
13180 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13184 (@value{GDBP}) target ctf ctf.ctf
13185 (@value{GDBP}) tfind
13186 Found trace frame 0, tracepoint 2
13187 39 ++a; /* set tracepoint 1 here */
13188 (@value{GDBP}) tdump
13189 Data collected at tracepoint 2, trace frame 0:
13193 c = @{"123", "456", "789", "123", "456", "789"@}
13194 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13202 @chapter Debugging Programs That Use Overlays
13205 If your program is too large to fit completely in your target system's
13206 memory, you can sometimes use @dfn{overlays} to work around this
13207 problem. @value{GDBN} provides some support for debugging programs that
13211 * How Overlays Work:: A general explanation of overlays.
13212 * Overlay Commands:: Managing overlays in @value{GDBN}.
13213 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13214 mapped by asking the inferior.
13215 * Overlay Sample Program:: A sample program using overlays.
13218 @node How Overlays Work
13219 @section How Overlays Work
13220 @cindex mapped overlays
13221 @cindex unmapped overlays
13222 @cindex load address, overlay's
13223 @cindex mapped address
13224 @cindex overlay area
13226 Suppose you have a computer whose instruction address space is only 64
13227 kilobytes long, but which has much more memory which can be accessed by
13228 other means: special instructions, segment registers, or memory
13229 management hardware, for example. Suppose further that you want to
13230 adapt a program which is larger than 64 kilobytes to run on this system.
13232 One solution is to identify modules of your program which are relatively
13233 independent, and need not call each other directly; call these modules
13234 @dfn{overlays}. Separate the overlays from the main program, and place
13235 their machine code in the larger memory. Place your main program in
13236 instruction memory, but leave at least enough space there to hold the
13237 largest overlay as well.
13239 Now, to call a function located in an overlay, you must first copy that
13240 overlay's machine code from the large memory into the space set aside
13241 for it in the instruction memory, and then jump to its entry point
13244 @c NB: In the below the mapped area's size is greater or equal to the
13245 @c size of all overlays. This is intentional to remind the developer
13246 @c that overlays don't necessarily need to be the same size.
13250 Data Instruction Larger
13251 Address Space Address Space Address Space
13252 +-----------+ +-----------+ +-----------+
13254 +-----------+ +-----------+ +-----------+<-- overlay 1
13255 | program | | main | .----| overlay 1 | load address
13256 | variables | | program | | +-----------+
13257 | and heap | | | | | |
13258 +-----------+ | | | +-----------+<-- overlay 2
13259 | | +-----------+ | | | load address
13260 +-----------+ | | | .-| overlay 2 |
13262 mapped --->+-----------+ | | +-----------+
13263 address | | | | | |
13264 | overlay | <-' | | |
13265 | area | <---' +-----------+<-- overlay 3
13266 | | <---. | | load address
13267 +-----------+ `--| overlay 3 |
13274 @anchor{A code overlay}A code overlay
13278 The diagram (@pxref{A code overlay}) shows a system with separate data
13279 and instruction address spaces. To map an overlay, the program copies
13280 its code from the larger address space to the instruction address space.
13281 Since the overlays shown here all use the same mapped address, only one
13282 may be mapped at a time. For a system with a single address space for
13283 data and instructions, the diagram would be similar, except that the
13284 program variables and heap would share an address space with the main
13285 program and the overlay area.
13287 An overlay loaded into instruction memory and ready for use is called a
13288 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13289 instruction memory. An overlay not present (or only partially present)
13290 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13291 is its address in the larger memory. The mapped address is also called
13292 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13293 called the @dfn{load memory address}, or @dfn{LMA}.
13295 Unfortunately, overlays are not a completely transparent way to adapt a
13296 program to limited instruction memory. They introduce a new set of
13297 global constraints you must keep in mind as you design your program:
13302 Before calling or returning to a function in an overlay, your program
13303 must make sure that overlay is actually mapped. Otherwise, the call or
13304 return will transfer control to the right address, but in the wrong
13305 overlay, and your program will probably crash.
13308 If the process of mapping an overlay is expensive on your system, you
13309 will need to choose your overlays carefully to minimize their effect on
13310 your program's performance.
13313 The executable file you load onto your system must contain each
13314 overlay's instructions, appearing at the overlay's load address, not its
13315 mapped address. However, each overlay's instructions must be relocated
13316 and its symbols defined as if the overlay were at its mapped address.
13317 You can use GNU linker scripts to specify different load and relocation
13318 addresses for pieces of your program; see @ref{Overlay Description,,,
13319 ld.info, Using ld: the GNU linker}.
13322 The procedure for loading executable files onto your system must be able
13323 to load their contents into the larger address space as well as the
13324 instruction and data spaces.
13328 The overlay system described above is rather simple, and could be
13329 improved in many ways:
13334 If your system has suitable bank switch registers or memory management
13335 hardware, you could use those facilities to make an overlay's load area
13336 contents simply appear at their mapped address in instruction space.
13337 This would probably be faster than copying the overlay to its mapped
13338 area in the usual way.
13341 If your overlays are small enough, you could set aside more than one
13342 overlay area, and have more than one overlay mapped at a time.
13345 You can use overlays to manage data, as well as instructions. In
13346 general, data overlays are even less transparent to your design than
13347 code overlays: whereas code overlays only require care when you call or
13348 return to functions, data overlays require care every time you access
13349 the data. Also, if you change the contents of a data overlay, you
13350 must copy its contents back out to its load address before you can copy a
13351 different data overlay into the same mapped area.
13356 @node Overlay Commands
13357 @section Overlay Commands
13359 To use @value{GDBN}'s overlay support, each overlay in your program must
13360 correspond to a separate section of the executable file. The section's
13361 virtual memory address and load memory address must be the overlay's
13362 mapped and load addresses. Identifying overlays with sections allows
13363 @value{GDBN} to determine the appropriate address of a function or
13364 variable, depending on whether the overlay is mapped or not.
13366 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13367 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13372 Disable @value{GDBN}'s overlay support. When overlay support is
13373 disabled, @value{GDBN} assumes that all functions and variables are
13374 always present at their mapped addresses. By default, @value{GDBN}'s
13375 overlay support is disabled.
13377 @item overlay manual
13378 @cindex manual overlay debugging
13379 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13380 relies on you to tell it which overlays are mapped, and which are not,
13381 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13382 commands described below.
13384 @item overlay map-overlay @var{overlay}
13385 @itemx overlay map @var{overlay}
13386 @cindex map an overlay
13387 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13388 be the name of the object file section containing the overlay. When an
13389 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13390 functions and variables at their mapped addresses. @value{GDBN} assumes
13391 that any other overlays whose mapped ranges overlap that of
13392 @var{overlay} are now unmapped.
13394 @item overlay unmap-overlay @var{overlay}
13395 @itemx overlay unmap @var{overlay}
13396 @cindex unmap an overlay
13397 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13398 must be the name of the object file section containing the overlay.
13399 When an overlay is unmapped, @value{GDBN} assumes it can find the
13400 overlay's functions and variables at their load addresses.
13403 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13404 consults a data structure the overlay manager maintains in the inferior
13405 to see which overlays are mapped. For details, see @ref{Automatic
13406 Overlay Debugging}.
13408 @item overlay load-target
13409 @itemx overlay load
13410 @cindex reloading the overlay table
13411 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13412 re-reads the table @value{GDBN} automatically each time the inferior
13413 stops, so this command should only be necessary if you have changed the
13414 overlay mapping yourself using @value{GDBN}. This command is only
13415 useful when using automatic overlay debugging.
13417 @item overlay list-overlays
13418 @itemx overlay list
13419 @cindex listing mapped overlays
13420 Display a list of the overlays currently mapped, along with their mapped
13421 addresses, load addresses, and sizes.
13425 Normally, when @value{GDBN} prints a code address, it includes the name
13426 of the function the address falls in:
13429 (@value{GDBP}) print main
13430 $3 = @{int ()@} 0x11a0 <main>
13433 When overlay debugging is enabled, @value{GDBN} recognizes code in
13434 unmapped overlays, and prints the names of unmapped functions with
13435 asterisks around them. For example, if @code{foo} is a function in an
13436 unmapped overlay, @value{GDBN} prints it this way:
13439 (@value{GDBP}) overlay list
13440 No sections are mapped.
13441 (@value{GDBP}) print foo
13442 $5 = @{int (int)@} 0x100000 <*foo*>
13445 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13449 (@value{GDBP}) overlay list
13450 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13451 mapped at 0x1016 - 0x104a
13452 (@value{GDBP}) print foo
13453 $6 = @{int (int)@} 0x1016 <foo>
13456 When overlay debugging is enabled, @value{GDBN} can find the correct
13457 address for functions and variables in an overlay, whether or not the
13458 overlay is mapped. This allows most @value{GDBN} commands, like
13459 @code{break} and @code{disassemble}, to work normally, even on unmapped
13460 code. However, @value{GDBN}'s breakpoint support has some limitations:
13464 @cindex breakpoints in overlays
13465 @cindex overlays, setting breakpoints in
13466 You can set breakpoints in functions in unmapped overlays, as long as
13467 @value{GDBN} can write to the overlay at its load address.
13469 @value{GDBN} can not set hardware or simulator-based breakpoints in
13470 unmapped overlays. However, if you set a breakpoint at the end of your
13471 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13472 you are using manual overlay management), @value{GDBN} will re-set its
13473 breakpoints properly.
13477 @node Automatic Overlay Debugging
13478 @section Automatic Overlay Debugging
13479 @cindex automatic overlay debugging
13481 @value{GDBN} can automatically track which overlays are mapped and which
13482 are not, given some simple co-operation from the overlay manager in the
13483 inferior. If you enable automatic overlay debugging with the
13484 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13485 looks in the inferior's memory for certain variables describing the
13486 current state of the overlays.
13488 Here are the variables your overlay manager must define to support
13489 @value{GDBN}'s automatic overlay debugging:
13493 @item @code{_ovly_table}:
13494 This variable must be an array of the following structures:
13499 /* The overlay's mapped address. */
13502 /* The size of the overlay, in bytes. */
13503 unsigned long size;
13505 /* The overlay's load address. */
13508 /* Non-zero if the overlay is currently mapped;
13510 unsigned long mapped;
13514 @item @code{_novlys}:
13515 This variable must be a four-byte signed integer, holding the total
13516 number of elements in @code{_ovly_table}.
13520 To decide whether a particular overlay is mapped or not, @value{GDBN}
13521 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13522 @code{lma} members equal the VMA and LMA of the overlay's section in the
13523 executable file. When @value{GDBN} finds a matching entry, it consults
13524 the entry's @code{mapped} member to determine whether the overlay is
13527 In addition, your overlay manager may define a function called
13528 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13529 will silently set a breakpoint there. If the overlay manager then
13530 calls this function whenever it has changed the overlay table, this
13531 will enable @value{GDBN} to accurately keep track of which overlays
13532 are in program memory, and update any breakpoints that may be set
13533 in overlays. This will allow breakpoints to work even if the
13534 overlays are kept in ROM or other non-writable memory while they
13535 are not being executed.
13537 @node Overlay Sample Program
13538 @section Overlay Sample Program
13539 @cindex overlay example program
13541 When linking a program which uses overlays, you must place the overlays
13542 at their load addresses, while relocating them to run at their mapped
13543 addresses. To do this, you must write a linker script (@pxref{Overlay
13544 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13545 since linker scripts are specific to a particular host system, target
13546 architecture, and target memory layout, this manual cannot provide
13547 portable sample code demonstrating @value{GDBN}'s overlay support.
13549 However, the @value{GDBN} source distribution does contain an overlaid
13550 program, with linker scripts for a few systems, as part of its test
13551 suite. The program consists of the following files from
13552 @file{gdb/testsuite/gdb.base}:
13556 The main program file.
13558 A simple overlay manager, used by @file{overlays.c}.
13563 Overlay modules, loaded and used by @file{overlays.c}.
13566 Linker scripts for linking the test program on the @code{d10v-elf}
13567 and @code{m32r-elf} targets.
13570 You can build the test program using the @code{d10v-elf} GCC
13571 cross-compiler like this:
13574 $ d10v-elf-gcc -g -c overlays.c
13575 $ d10v-elf-gcc -g -c ovlymgr.c
13576 $ d10v-elf-gcc -g -c foo.c
13577 $ d10v-elf-gcc -g -c bar.c
13578 $ d10v-elf-gcc -g -c baz.c
13579 $ d10v-elf-gcc -g -c grbx.c
13580 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13581 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13584 The build process is identical for any other architecture, except that
13585 you must substitute the appropriate compiler and linker script for the
13586 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13590 @chapter Using @value{GDBN} with Different Languages
13593 Although programming languages generally have common aspects, they are
13594 rarely expressed in the same manner. For instance, in ANSI C,
13595 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13596 Modula-2, it is accomplished by @code{p^}. Values can also be
13597 represented (and displayed) differently. Hex numbers in C appear as
13598 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13600 @cindex working language
13601 Language-specific information is built into @value{GDBN} for some languages,
13602 allowing you to express operations like the above in your program's
13603 native language, and allowing @value{GDBN} to output values in a manner
13604 consistent with the syntax of your program's native language. The
13605 language you use to build expressions is called the @dfn{working
13609 * Setting:: Switching between source languages
13610 * Show:: Displaying the language
13611 * Checks:: Type and range checks
13612 * Supported Languages:: Supported languages
13613 * Unsupported Languages:: Unsupported languages
13617 @section Switching Between Source Languages
13619 There are two ways to control the working language---either have @value{GDBN}
13620 set it automatically, or select it manually yourself. You can use the
13621 @code{set language} command for either purpose. On startup, @value{GDBN}
13622 defaults to setting the language automatically. The working language is
13623 used to determine how expressions you type are interpreted, how values
13626 In addition to the working language, every source file that
13627 @value{GDBN} knows about has its own working language. For some object
13628 file formats, the compiler might indicate which language a particular
13629 source file is in. However, most of the time @value{GDBN} infers the
13630 language from the name of the file. The language of a source file
13631 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13632 show each frame appropriately for its own language. There is no way to
13633 set the language of a source file from within @value{GDBN}, but you can
13634 set the language associated with a filename extension. @xref{Show, ,
13635 Displaying the Language}.
13637 This is most commonly a problem when you use a program, such
13638 as @code{cfront} or @code{f2c}, that generates C but is written in
13639 another language. In that case, make the
13640 program use @code{#line} directives in its C output; that way
13641 @value{GDBN} will know the correct language of the source code of the original
13642 program, and will display that source code, not the generated C code.
13645 * Filenames:: Filename extensions and languages.
13646 * Manually:: Setting the working language manually
13647 * Automatically:: Having @value{GDBN} infer the source language
13651 @subsection List of Filename Extensions and Languages
13653 If a source file name ends in one of the following extensions, then
13654 @value{GDBN} infers that its language is the one indicated.
13672 C@t{++} source file
13678 Objective-C source file
13682 Fortran source file
13685 Modula-2 source file
13689 Assembler source file. This actually behaves almost like C, but
13690 @value{GDBN} does not skip over function prologues when stepping.
13693 In addition, you may set the language associated with a filename
13694 extension. @xref{Show, , Displaying the Language}.
13697 @subsection Setting the Working Language
13699 If you allow @value{GDBN} to set the language automatically,
13700 expressions are interpreted the same way in your debugging session and
13703 @kindex set language
13704 If you wish, you may set the language manually. To do this, issue the
13705 command @samp{set language @var{lang}}, where @var{lang} is the name of
13706 a language, such as
13707 @code{c} or @code{modula-2}.
13708 For a list of the supported languages, type @samp{set language}.
13710 Setting the language manually prevents @value{GDBN} from updating the working
13711 language automatically. This can lead to confusion if you try
13712 to debug a program when the working language is not the same as the
13713 source language, when an expression is acceptable to both
13714 languages---but means different things. For instance, if the current
13715 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13723 might not have the effect you intended. In C, this means to add
13724 @code{b} and @code{c} and place the result in @code{a}. The result
13725 printed would be the value of @code{a}. In Modula-2, this means to compare
13726 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13728 @node Automatically
13729 @subsection Having @value{GDBN} Infer the Source Language
13731 To have @value{GDBN} set the working language automatically, use
13732 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13733 then infers the working language. That is, when your program stops in a
13734 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13735 working language to the language recorded for the function in that
13736 frame. If the language for a frame is unknown (that is, if the function
13737 or block corresponding to the frame was defined in a source file that
13738 does not have a recognized extension), the current working language is
13739 not changed, and @value{GDBN} issues a warning.
13741 This may not seem necessary for most programs, which are written
13742 entirely in one source language. However, program modules and libraries
13743 written in one source language can be used by a main program written in
13744 a different source language. Using @samp{set language auto} in this
13745 case frees you from having to set the working language manually.
13748 @section Displaying the Language
13750 The following commands help you find out which language is the
13751 working language, and also what language source files were written in.
13754 @item show language
13755 @anchor{show language}
13756 @kindex show language
13757 Display the current working language. This is the
13758 language you can use with commands such as @code{print} to
13759 build and compute expressions that may involve variables in your program.
13762 @kindex info frame@r{, show the source language}
13763 Display the source language for this frame. This language becomes the
13764 working language if you use an identifier from this frame.
13765 @xref{Frame Info, ,Information about a Frame}, to identify the other
13766 information listed here.
13769 @kindex info source@r{, show the source language}
13770 Display the source language of this source file.
13771 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13772 information listed here.
13775 In unusual circumstances, you may have source files with extensions
13776 not in the standard list. You can then set the extension associated
13777 with a language explicitly:
13780 @item set extension-language @var{ext} @var{language}
13781 @kindex set extension-language
13782 Tell @value{GDBN} that source files with extension @var{ext} are to be
13783 assumed as written in the source language @var{language}.
13785 @item info extensions
13786 @kindex info extensions
13787 List all the filename extensions and the associated languages.
13791 @section Type and Range Checking
13793 Some languages are designed to guard you against making seemingly common
13794 errors through a series of compile- and run-time checks. These include
13795 checking the type of arguments to functions and operators and making
13796 sure mathematical overflows are caught at run time. Checks such as
13797 these help to ensure a program's correctness once it has been compiled
13798 by eliminating type mismatches and providing active checks for range
13799 errors when your program is running.
13801 By default @value{GDBN} checks for these errors according to the
13802 rules of the current source language. Although @value{GDBN} does not check
13803 the statements in your program, it can check expressions entered directly
13804 into @value{GDBN} for evaluation via the @code{print} command, for example.
13807 * Type Checking:: An overview of type checking
13808 * Range Checking:: An overview of range checking
13811 @cindex type checking
13812 @cindex checks, type
13813 @node Type Checking
13814 @subsection An Overview of Type Checking
13816 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13817 arguments to operators and functions have to be of the correct type,
13818 otherwise an error occurs. These checks prevent type mismatch
13819 errors from ever causing any run-time problems. For example,
13822 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13824 (@value{GDBP}) print obj.my_method (0)
13827 (@value{GDBP}) print obj.my_method (0x1234)
13828 Cannot resolve method klass::my_method to any overloaded instance
13831 The second example fails because in C@t{++} the integer constant
13832 @samp{0x1234} is not type-compatible with the pointer parameter type.
13834 For the expressions you use in @value{GDBN} commands, you can tell
13835 @value{GDBN} to not enforce strict type checking or
13836 to treat any mismatches as errors and abandon the expression;
13837 When type checking is disabled, @value{GDBN} successfully evaluates
13838 expressions like the second example above.
13840 Even if type checking is off, there may be other reasons
13841 related to type that prevent @value{GDBN} from evaluating an expression.
13842 For instance, @value{GDBN} does not know how to add an @code{int} and
13843 a @code{struct foo}. These particular type errors have nothing to do
13844 with the language in use and usually arise from expressions which make
13845 little sense to evaluate anyway.
13847 @value{GDBN} provides some additional commands for controlling type checking:
13849 @kindex set check type
13850 @kindex show check type
13852 @item set check type on
13853 @itemx set check type off
13854 Set strict type checking on or off. If any type mismatches occur in
13855 evaluating an expression while type checking is on, @value{GDBN} prints a
13856 message and aborts evaluation of the expression.
13858 @item show check type
13859 Show the current setting of type checking and whether @value{GDBN}
13860 is enforcing strict type checking rules.
13863 @cindex range checking
13864 @cindex checks, range
13865 @node Range Checking
13866 @subsection An Overview of Range Checking
13868 In some languages (such as Modula-2), it is an error to exceed the
13869 bounds of a type; this is enforced with run-time checks. Such range
13870 checking is meant to ensure program correctness by making sure
13871 computations do not overflow, or indices on an array element access do
13872 not exceed the bounds of the array.
13874 For expressions you use in @value{GDBN} commands, you can tell
13875 @value{GDBN} to treat range errors in one of three ways: ignore them,
13876 always treat them as errors and abandon the expression, or issue
13877 warnings but evaluate the expression anyway.
13879 A range error can result from numerical overflow, from exceeding an
13880 array index bound, or when you type a constant that is not a member
13881 of any type. Some languages, however, do not treat overflows as an
13882 error. In many implementations of C, mathematical overflow causes the
13883 result to ``wrap around'' to lower values---for example, if @var{m} is
13884 the largest integer value, and @var{s} is the smallest, then
13887 @var{m} + 1 @result{} @var{s}
13890 This, too, is specific to individual languages, and in some cases
13891 specific to individual compilers or machines. @xref{Supported Languages, ,
13892 Supported Languages}, for further details on specific languages.
13894 @value{GDBN} provides some additional commands for controlling the range checker:
13896 @kindex set check range
13897 @kindex show check range
13899 @item set check range auto
13900 Set range checking on or off based on the current working language.
13901 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13904 @item set check range on
13905 @itemx set check range off
13906 Set range checking on or off, overriding the default setting for the
13907 current working language. A warning is issued if the setting does not
13908 match the language default. If a range error occurs and range checking is on,
13909 then a message is printed and evaluation of the expression is aborted.
13911 @item set check range warn
13912 Output messages when the @value{GDBN} range checker detects a range error,
13913 but attempt to evaluate the expression anyway. Evaluating the
13914 expression may still be impossible for other reasons, such as accessing
13915 memory that the process does not own (a typical example from many Unix
13919 Show the current setting of the range checker, and whether or not it is
13920 being set automatically by @value{GDBN}.
13923 @node Supported Languages
13924 @section Supported Languages
13926 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13927 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13928 @c This is false ...
13929 Some @value{GDBN} features may be used in expressions regardless of the
13930 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13931 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13932 ,Expressions}) can be used with the constructs of any supported
13935 The following sections detail to what degree each source language is
13936 supported by @value{GDBN}. These sections are not meant to be language
13937 tutorials or references, but serve only as a reference guide to what the
13938 @value{GDBN} expression parser accepts, and what input and output
13939 formats should look like for different languages. There are many good
13940 books written on each of these languages; please look to these for a
13941 language reference or tutorial.
13944 * C:: C and C@t{++}
13947 * Objective-C:: Objective-C
13948 * OpenCL C:: OpenCL C
13949 * Fortran:: Fortran
13951 * Modula-2:: Modula-2
13956 @subsection C and C@t{++}
13958 @cindex C and C@t{++}
13959 @cindex expressions in C or C@t{++}
13961 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13962 to both languages. Whenever this is the case, we discuss those languages
13966 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13967 @cindex @sc{gnu} C@t{++}
13968 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13969 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13970 effectively, you must compile your C@t{++} programs with a supported
13971 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13972 compiler (@code{aCC}).
13975 * C Operators:: C and C@t{++} operators
13976 * C Constants:: C and C@t{++} constants
13977 * C Plus Plus Expressions:: C@t{++} expressions
13978 * C Defaults:: Default settings for C and C@t{++}
13979 * C Checks:: C and C@t{++} type and range checks
13980 * Debugging C:: @value{GDBN} and C
13981 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13982 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13986 @subsubsection C and C@t{++} Operators
13988 @cindex C and C@t{++} operators
13990 Operators must be defined on values of specific types. For instance,
13991 @code{+} is defined on numbers, but not on structures. Operators are
13992 often defined on groups of types.
13994 For the purposes of C and C@t{++}, the following definitions hold:
13999 @emph{Integral types} include @code{int} with any of its storage-class
14000 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14003 @emph{Floating-point types} include @code{float}, @code{double}, and
14004 @code{long double} (if supported by the target platform).
14007 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14010 @emph{Scalar types} include all of the above.
14015 The following operators are supported. They are listed here
14016 in order of increasing precedence:
14020 The comma or sequencing operator. Expressions in a comma-separated list
14021 are evaluated from left to right, with the result of the entire
14022 expression being the last expression evaluated.
14025 Assignment. The value of an assignment expression is the value
14026 assigned. Defined on scalar types.
14029 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14030 and translated to @w{@code{@var{a} = @var{a op b}}}.
14031 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14032 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14033 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14036 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14037 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14038 should be of an integral type.
14041 Logical @sc{or}. Defined on integral types.
14044 Logical @sc{and}. Defined on integral types.
14047 Bitwise @sc{or}. Defined on integral types.
14050 Bitwise exclusive-@sc{or}. Defined on integral types.
14053 Bitwise @sc{and}. Defined on integral types.
14056 Equality and inequality. Defined on scalar types. The value of these
14057 expressions is 0 for false and non-zero for true.
14059 @item <@r{, }>@r{, }<=@r{, }>=
14060 Less than, greater than, less than or equal, greater than or equal.
14061 Defined on scalar types. The value of these expressions is 0 for false
14062 and non-zero for true.
14065 left shift, and right shift. Defined on integral types.
14068 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14071 Addition and subtraction. Defined on integral types, floating-point types and
14074 @item *@r{, }/@r{, }%
14075 Multiplication, division, and modulus. Multiplication and division are
14076 defined on integral and floating-point types. Modulus is defined on
14080 Increment and decrement. When appearing before a variable, the
14081 operation is performed before the variable is used in an expression;
14082 when appearing after it, the variable's value is used before the
14083 operation takes place.
14086 Pointer dereferencing. Defined on pointer types. Same precedence as
14090 Address operator. Defined on variables. Same precedence as @code{++}.
14092 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14093 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14094 to examine the address
14095 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14099 Negative. Defined on integral and floating-point types. Same
14100 precedence as @code{++}.
14103 Logical negation. Defined on integral types. Same precedence as
14107 Bitwise complement operator. Defined on integral types. Same precedence as
14112 Structure member, and pointer-to-structure member. For convenience,
14113 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14114 pointer based on the stored type information.
14115 Defined on @code{struct} and @code{union} data.
14118 Dereferences of pointers to members.
14121 Array indexing. @code{@var{a}[@var{i}]} is defined as
14122 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14125 Function parameter list. Same precedence as @code{->}.
14128 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14129 and @code{class} types.
14132 Doubled colons also represent the @value{GDBN} scope operator
14133 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14137 If an operator is redefined in the user code, @value{GDBN} usually
14138 attempts to invoke the redefined version instead of using the operator's
14139 predefined meaning.
14142 @subsubsection C and C@t{++} Constants
14144 @cindex C and C@t{++} constants
14146 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14151 Integer constants are a sequence of digits. Octal constants are
14152 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14153 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14154 @samp{l}, specifying that the constant should be treated as a
14158 Floating point constants are a sequence of digits, followed by a decimal
14159 point, followed by a sequence of digits, and optionally followed by an
14160 exponent. An exponent is of the form:
14161 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14162 sequence of digits. The @samp{+} is optional for positive exponents.
14163 A floating-point constant may also end with a letter @samp{f} or
14164 @samp{F}, specifying that the constant should be treated as being of
14165 the @code{float} (as opposed to the default @code{double}) type; or with
14166 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14170 Enumerated constants consist of enumerated identifiers, or their
14171 integral equivalents.
14174 Character constants are a single character surrounded by single quotes
14175 (@code{'}), or a number---the ordinal value of the corresponding character
14176 (usually its @sc{ascii} value). Within quotes, the single character may
14177 be represented by a letter or by @dfn{escape sequences}, which are of
14178 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14179 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14180 @samp{@var{x}} is a predefined special character---for example,
14181 @samp{\n} for newline.
14183 Wide character constants can be written by prefixing a character
14184 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14185 form of @samp{x}. The target wide character set is used when
14186 computing the value of this constant (@pxref{Character Sets}).
14189 String constants are a sequence of character constants surrounded by
14190 double quotes (@code{"}). Any valid character constant (as described
14191 above) may appear. Double quotes within the string must be preceded by
14192 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14195 Wide string constants can be written by prefixing a string constant
14196 with @samp{L}, as in C. The target wide character set is used when
14197 computing the value of this constant (@pxref{Character Sets}).
14200 Pointer constants are an integral value. You can also write pointers
14201 to constants using the C operator @samp{&}.
14204 Array constants are comma-separated lists surrounded by braces @samp{@{}
14205 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14206 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14207 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14210 @node C Plus Plus Expressions
14211 @subsubsection C@t{++} Expressions
14213 @cindex expressions in C@t{++}
14214 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14216 @cindex debugging C@t{++} programs
14217 @cindex C@t{++} compilers
14218 @cindex debug formats and C@t{++}
14219 @cindex @value{NGCC} and C@t{++}
14221 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14222 the proper compiler and the proper debug format. Currently,
14223 @value{GDBN} works best when debugging C@t{++} code that is compiled
14224 with the most recent version of @value{NGCC} possible. The DWARF
14225 debugging format is preferred; @value{NGCC} defaults to this on most
14226 popular platforms. Other compilers and/or debug formats are likely to
14227 work badly or not at all when using @value{GDBN} to debug C@t{++}
14228 code. @xref{Compilation}.
14233 @cindex member functions
14235 Member function calls are allowed; you can use expressions like
14238 count = aml->GetOriginal(x, y)
14241 @vindex this@r{, inside C@t{++} member functions}
14242 @cindex namespace in C@t{++}
14244 While a member function is active (in the selected stack frame), your
14245 expressions have the same namespace available as the member function;
14246 that is, @value{GDBN} allows implicit references to the class instance
14247 pointer @code{this} following the same rules as C@t{++}. @code{using}
14248 declarations in the current scope are also respected by @value{GDBN}.
14250 @cindex call overloaded functions
14251 @cindex overloaded functions, calling
14252 @cindex type conversions in C@t{++}
14254 You can call overloaded functions; @value{GDBN} resolves the function
14255 call to the right definition, with some restrictions. @value{GDBN} does not
14256 perform overload resolution involving user-defined type conversions,
14257 calls to constructors, or instantiations of templates that do not exist
14258 in the program. It also cannot handle ellipsis argument lists or
14261 It does perform integral conversions and promotions, floating-point
14262 promotions, arithmetic conversions, pointer conversions, conversions of
14263 class objects to base classes, and standard conversions such as those of
14264 functions or arrays to pointers; it requires an exact match on the
14265 number of function arguments.
14267 Overload resolution is always performed, unless you have specified
14268 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14269 ,@value{GDBN} Features for C@t{++}}.
14271 You must specify @code{set overload-resolution off} in order to use an
14272 explicit function signature to call an overloaded function, as in
14274 p 'foo(char,int)'('x', 13)
14277 The @value{GDBN} command-completion facility can simplify this;
14278 see @ref{Completion, ,Command Completion}.
14280 @cindex reference declarations
14282 @value{GDBN} understands variables declared as C@t{++} references; you can use
14283 them in expressions just as you do in C@t{++} source---they are automatically
14286 In the parameter list shown when @value{GDBN} displays a frame, the values of
14287 reference variables are not displayed (unlike other variables); this
14288 avoids clutter, since references are often used for large structures.
14289 The @emph{address} of a reference variable is always shown, unless
14290 you have specified @samp{set print address off}.
14293 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14294 expressions can use it just as expressions in your program do. Since
14295 one scope may be defined in another, you can use @code{::} repeatedly if
14296 necessary, for example in an expression like
14297 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14298 resolving name scope by reference to source files, in both C and C@t{++}
14299 debugging (@pxref{Variables, ,Program Variables}).
14302 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14307 @subsubsection C and C@t{++} Defaults
14309 @cindex C and C@t{++} defaults
14311 If you allow @value{GDBN} to set range checking automatically, it
14312 defaults to @code{off} whenever the working language changes to
14313 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14314 selects the working language.
14316 If you allow @value{GDBN} to set the language automatically, it
14317 recognizes source files whose names end with @file{.c}, @file{.C}, or
14318 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14319 these files, it sets the working language to C or C@t{++}.
14320 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14321 for further details.
14324 @subsubsection C and C@t{++} Type and Range Checks
14326 @cindex C and C@t{++} checks
14328 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14329 checking is used. However, if you turn type checking off, @value{GDBN}
14330 will allow certain non-standard conversions, such as promoting integer
14331 constants to pointers.
14333 Range checking, if turned on, is done on mathematical operations. Array
14334 indices are not checked, since they are often used to index a pointer
14335 that is not itself an array.
14338 @subsubsection @value{GDBN} and C
14340 The @code{set print union} and @code{show print union} commands apply to
14341 the @code{union} type. When set to @samp{on}, any @code{union} that is
14342 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14343 appears as @samp{@{...@}}.
14345 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14346 with pointers and a memory allocation function. @xref{Expressions,
14349 @node Debugging C Plus Plus
14350 @subsubsection @value{GDBN} Features for C@t{++}
14352 @cindex commands for C@t{++}
14354 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14355 designed specifically for use with C@t{++}. Here is a summary:
14358 @cindex break in overloaded functions
14359 @item @r{breakpoint menus}
14360 When you want a breakpoint in a function whose name is overloaded,
14361 @value{GDBN} has the capability to display a menu of possible breakpoint
14362 locations to help you specify which function definition you want.
14363 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14365 @cindex overloading in C@t{++}
14366 @item rbreak @var{regex}
14367 Setting breakpoints using regular expressions is helpful for setting
14368 breakpoints on overloaded functions that are not members of any special
14370 @xref{Set Breaks, ,Setting Breakpoints}.
14372 @cindex C@t{++} exception handling
14374 @itemx catch rethrow
14376 Debug C@t{++} exception handling using these commands. @xref{Set
14377 Catchpoints, , Setting Catchpoints}.
14379 @cindex inheritance
14380 @item ptype @var{typename}
14381 Print inheritance relationships as well as other information for type
14383 @xref{Symbols, ,Examining the Symbol Table}.
14385 @item info vtbl @var{expression}.
14386 The @code{info vtbl} command can be used to display the virtual
14387 method tables of the object computed by @var{expression}. This shows
14388 one entry per virtual table; there may be multiple virtual tables when
14389 multiple inheritance is in use.
14391 @cindex C@t{++} demangling
14392 @item demangle @var{name}
14393 Demangle @var{name}.
14394 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14396 @cindex C@t{++} symbol display
14397 @item set print demangle
14398 @itemx show print demangle
14399 @itemx set print asm-demangle
14400 @itemx show print asm-demangle
14401 Control whether C@t{++} symbols display in their source form, both when
14402 displaying code as C@t{++} source and when displaying disassemblies.
14403 @xref{Print Settings, ,Print Settings}.
14405 @item set print object
14406 @itemx show print object
14407 Choose whether to print derived (actual) or declared types of objects.
14408 @xref{Print Settings, ,Print Settings}.
14410 @item set print vtbl
14411 @itemx show print vtbl
14412 Control the format for printing virtual function tables.
14413 @xref{Print Settings, ,Print Settings}.
14414 (The @code{vtbl} commands do not work on programs compiled with the HP
14415 ANSI C@t{++} compiler (@code{aCC}).)
14417 @kindex set overload-resolution
14418 @cindex overloaded functions, overload resolution
14419 @item set overload-resolution on
14420 Enable overload resolution for C@t{++} expression evaluation. The default
14421 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14422 and searches for a function whose signature matches the argument types,
14423 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14424 Expressions, ,C@t{++} Expressions}, for details).
14425 If it cannot find a match, it emits a message.
14427 @item set overload-resolution off
14428 Disable overload resolution for C@t{++} expression evaluation. For
14429 overloaded functions that are not class member functions, @value{GDBN}
14430 chooses the first function of the specified name that it finds in the
14431 symbol table, whether or not its arguments are of the correct type. For
14432 overloaded functions that are class member functions, @value{GDBN}
14433 searches for a function whose signature @emph{exactly} matches the
14436 @kindex show overload-resolution
14437 @item show overload-resolution
14438 Show the current setting of overload resolution.
14440 @item @r{Overloaded symbol names}
14441 You can specify a particular definition of an overloaded symbol, using
14442 the same notation that is used to declare such symbols in C@t{++}: type
14443 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14444 also use the @value{GDBN} command-line word completion facilities to list the
14445 available choices, or to finish the type list for you.
14446 @xref{Completion,, Command Completion}, for details on how to do this.
14449 @node Decimal Floating Point
14450 @subsubsection Decimal Floating Point format
14451 @cindex decimal floating point format
14453 @value{GDBN} can examine, set and perform computations with numbers in
14454 decimal floating point format, which in the C language correspond to the
14455 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14456 specified by the extension to support decimal floating-point arithmetic.
14458 There are two encodings in use, depending on the architecture: BID (Binary
14459 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14460 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14463 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14464 to manipulate decimal floating point numbers, it is not possible to convert
14465 (using a cast, for example) integers wider than 32-bit to decimal float.
14467 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14468 point computations, error checking in decimal float operations ignores
14469 underflow, overflow and divide by zero exceptions.
14471 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14472 to inspect @code{_Decimal128} values stored in floating point registers.
14473 See @ref{PowerPC,,PowerPC} for more details.
14479 @value{GDBN} can be used to debug programs written in D and compiled with
14480 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14481 specific feature --- dynamic arrays.
14486 @cindex Go (programming language)
14487 @value{GDBN} can be used to debug programs written in Go and compiled with
14488 @file{gccgo} or @file{6g} compilers.
14490 Here is a summary of the Go-specific features and restrictions:
14493 @cindex current Go package
14494 @item The current Go package
14495 The name of the current package does not need to be specified when
14496 specifying global variables and functions.
14498 For example, given the program:
14502 var myglob = "Shall we?"
14508 When stopped inside @code{main} either of these work:
14512 (gdb) p main.myglob
14515 @cindex builtin Go types
14516 @item Builtin Go types
14517 The @code{string} type is recognized by @value{GDBN} and is printed
14520 @cindex builtin Go functions
14521 @item Builtin Go functions
14522 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14523 function and handles it internally.
14525 @cindex restrictions on Go expressions
14526 @item Restrictions on Go expressions
14527 All Go operators are supported except @code{&^}.
14528 The Go @code{_} ``blank identifier'' is not supported.
14529 Automatic dereferencing of pointers is not supported.
14533 @subsection Objective-C
14535 @cindex Objective-C
14536 This section provides information about some commands and command
14537 options that are useful for debugging Objective-C code. See also
14538 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14539 few more commands specific to Objective-C support.
14542 * Method Names in Commands::
14543 * The Print Command with Objective-C::
14546 @node Method Names in Commands
14547 @subsubsection Method Names in Commands
14549 The following commands have been extended to accept Objective-C method
14550 names as line specifications:
14552 @kindex clear@r{, and Objective-C}
14553 @kindex break@r{, and Objective-C}
14554 @kindex info line@r{, and Objective-C}
14555 @kindex jump@r{, and Objective-C}
14556 @kindex list@r{, and Objective-C}
14560 @item @code{info line}
14565 A fully qualified Objective-C method name is specified as
14568 -[@var{Class} @var{methodName}]
14571 where the minus sign is used to indicate an instance method and a
14572 plus sign (not shown) is used to indicate a class method. The class
14573 name @var{Class} and method name @var{methodName} are enclosed in
14574 brackets, similar to the way messages are specified in Objective-C
14575 source code. For example, to set a breakpoint at the @code{create}
14576 instance method of class @code{Fruit} in the program currently being
14580 break -[Fruit create]
14583 To list ten program lines around the @code{initialize} class method,
14587 list +[NSText initialize]
14590 In the current version of @value{GDBN}, the plus or minus sign is
14591 required. In future versions of @value{GDBN}, the plus or minus
14592 sign will be optional, but you can use it to narrow the search. It
14593 is also possible to specify just a method name:
14599 You must specify the complete method name, including any colons. If
14600 your program's source files contain more than one @code{create} method,
14601 you'll be presented with a numbered list of classes that implement that
14602 method. Indicate your choice by number, or type @samp{0} to exit if
14605 As another example, to clear a breakpoint established at the
14606 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14609 clear -[NSWindow makeKeyAndOrderFront:]
14612 @node The Print Command with Objective-C
14613 @subsubsection The Print Command With Objective-C
14614 @cindex Objective-C, print objects
14615 @kindex print-object
14616 @kindex po @r{(@code{print-object})}
14618 The print command has also been extended to accept methods. For example:
14621 print -[@var{object} hash]
14624 @cindex print an Objective-C object description
14625 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14627 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14628 and print the result. Also, an additional command has been added,
14629 @code{print-object} or @code{po} for short, which is meant to print
14630 the description of an object. However, this command may only work
14631 with certain Objective-C libraries that have a particular hook
14632 function, @code{_NSPrintForDebugger}, defined.
14635 @subsection OpenCL C
14638 This section provides information about @value{GDBN}s OpenCL C support.
14641 * OpenCL C Datatypes::
14642 * OpenCL C Expressions::
14643 * OpenCL C Operators::
14646 @node OpenCL C Datatypes
14647 @subsubsection OpenCL C Datatypes
14649 @cindex OpenCL C Datatypes
14650 @value{GDBN} supports the builtin scalar and vector datatypes specified
14651 by OpenCL 1.1. In addition the half- and double-precision floating point
14652 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14653 extensions are also known to @value{GDBN}.
14655 @node OpenCL C Expressions
14656 @subsubsection OpenCL C Expressions
14658 @cindex OpenCL C Expressions
14659 @value{GDBN} supports accesses to vector components including the access as
14660 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14661 supported by @value{GDBN} can be used as well.
14663 @node OpenCL C Operators
14664 @subsubsection OpenCL C Operators
14666 @cindex OpenCL C Operators
14667 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14671 @subsection Fortran
14672 @cindex Fortran-specific support in @value{GDBN}
14674 @value{GDBN} can be used to debug programs written in Fortran, but it
14675 currently supports only the features of Fortran 77 language.
14677 @cindex trailing underscore, in Fortran symbols
14678 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14679 among them) append an underscore to the names of variables and
14680 functions. When you debug programs compiled by those compilers, you
14681 will need to refer to variables and functions with a trailing
14685 * Fortran Operators:: Fortran operators and expressions
14686 * Fortran Defaults:: Default settings for Fortran
14687 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14690 @node Fortran Operators
14691 @subsubsection Fortran Operators and Expressions
14693 @cindex Fortran operators and expressions
14695 Operators must be defined on values of specific types. For instance,
14696 @code{+} is defined on numbers, but not on characters or other non-
14697 arithmetic types. Operators are often defined on groups of types.
14701 The exponentiation operator. It raises the first operand to the power
14705 The range operator. Normally used in the form of array(low:high) to
14706 represent a section of array.
14709 The access component operator. Normally used to access elements in derived
14710 types. Also suitable for unions. As unions aren't part of regular Fortran,
14711 this can only happen when accessing a register that uses a gdbarch-defined
14715 @node Fortran Defaults
14716 @subsubsection Fortran Defaults
14718 @cindex Fortran Defaults
14720 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14721 default uses case-insensitive matches for Fortran symbols. You can
14722 change that with the @samp{set case-insensitive} command, see
14723 @ref{Symbols}, for the details.
14725 @node Special Fortran Commands
14726 @subsubsection Special Fortran Commands
14728 @cindex Special Fortran commands
14730 @value{GDBN} has some commands to support Fortran-specific features,
14731 such as displaying common blocks.
14734 @cindex @code{COMMON} blocks, Fortran
14735 @kindex info common
14736 @item info common @r{[}@var{common-name}@r{]}
14737 This command prints the values contained in the Fortran @code{COMMON}
14738 block whose name is @var{common-name}. With no argument, the names of
14739 all @code{COMMON} blocks visible at the current program location are
14746 @cindex Pascal support in @value{GDBN}, limitations
14747 Debugging Pascal programs which use sets, subranges, file variables, or
14748 nested functions does not currently work. @value{GDBN} does not support
14749 entering expressions, printing values, or similar features using Pascal
14752 The Pascal-specific command @code{set print pascal_static-members}
14753 controls whether static members of Pascal objects are displayed.
14754 @xref{Print Settings, pascal_static-members}.
14757 @subsection Modula-2
14759 @cindex Modula-2, @value{GDBN} support
14761 The extensions made to @value{GDBN} to support Modula-2 only support
14762 output from the @sc{gnu} Modula-2 compiler (which is currently being
14763 developed). Other Modula-2 compilers are not currently supported, and
14764 attempting to debug executables produced by them is most likely
14765 to give an error as @value{GDBN} reads in the executable's symbol
14768 @cindex expressions in Modula-2
14770 * M2 Operators:: Built-in operators
14771 * Built-In Func/Proc:: Built-in functions and procedures
14772 * M2 Constants:: Modula-2 constants
14773 * M2 Types:: Modula-2 types
14774 * M2 Defaults:: Default settings for Modula-2
14775 * Deviations:: Deviations from standard Modula-2
14776 * M2 Checks:: Modula-2 type and range checks
14777 * M2 Scope:: The scope operators @code{::} and @code{.}
14778 * GDB/M2:: @value{GDBN} and Modula-2
14782 @subsubsection Operators
14783 @cindex Modula-2 operators
14785 Operators must be defined on values of specific types. For instance,
14786 @code{+} is defined on numbers, but not on structures. Operators are
14787 often defined on groups of types. For the purposes of Modula-2, the
14788 following definitions hold:
14793 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14797 @emph{Character types} consist of @code{CHAR} and its subranges.
14800 @emph{Floating-point types} consist of @code{REAL}.
14803 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14807 @emph{Scalar types} consist of all of the above.
14810 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14813 @emph{Boolean types} consist of @code{BOOLEAN}.
14817 The following operators are supported, and appear in order of
14818 increasing precedence:
14822 Function argument or array index separator.
14825 Assignment. The value of @var{var} @code{:=} @var{value} is
14829 Less than, greater than on integral, floating-point, or enumerated
14833 Less than or equal to, greater than or equal to
14834 on integral, floating-point and enumerated types, or set inclusion on
14835 set types. Same precedence as @code{<}.
14837 @item =@r{, }<>@r{, }#
14838 Equality and two ways of expressing inequality, valid on scalar types.
14839 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14840 available for inequality, since @code{#} conflicts with the script
14844 Set membership. Defined on set types and the types of their members.
14845 Same precedence as @code{<}.
14848 Boolean disjunction. Defined on boolean types.
14851 Boolean conjunction. Defined on boolean types.
14854 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14857 Addition and subtraction on integral and floating-point types, or union
14858 and difference on set types.
14861 Multiplication on integral and floating-point types, or set intersection
14865 Division on floating-point types, or symmetric set difference on set
14866 types. Same precedence as @code{*}.
14869 Integer division and remainder. Defined on integral types. Same
14870 precedence as @code{*}.
14873 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14876 Pointer dereferencing. Defined on pointer types.
14879 Boolean negation. Defined on boolean types. Same precedence as
14883 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14884 precedence as @code{^}.
14887 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14890 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14894 @value{GDBN} and Modula-2 scope operators.
14898 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14899 treats the use of the operator @code{IN}, or the use of operators
14900 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14901 @code{<=}, and @code{>=} on sets as an error.
14905 @node Built-In Func/Proc
14906 @subsubsection Built-in Functions and Procedures
14907 @cindex Modula-2 built-ins
14909 Modula-2 also makes available several built-in procedures and functions.
14910 In describing these, the following metavariables are used:
14915 represents an @code{ARRAY} variable.
14918 represents a @code{CHAR} constant or variable.
14921 represents a variable or constant of integral type.
14924 represents an identifier that belongs to a set. Generally used in the
14925 same function with the metavariable @var{s}. The type of @var{s} should
14926 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14929 represents a variable or constant of integral or floating-point type.
14932 represents a variable or constant of floating-point type.
14938 represents a variable.
14941 represents a variable or constant of one of many types. See the
14942 explanation of the function for details.
14945 All Modula-2 built-in procedures also return a result, described below.
14949 Returns the absolute value of @var{n}.
14952 If @var{c} is a lower case letter, it returns its upper case
14953 equivalent, otherwise it returns its argument.
14956 Returns the character whose ordinal value is @var{i}.
14959 Decrements the value in the variable @var{v} by one. Returns the new value.
14961 @item DEC(@var{v},@var{i})
14962 Decrements the value in the variable @var{v} by @var{i}. Returns the
14965 @item EXCL(@var{m},@var{s})
14966 Removes the element @var{m} from the set @var{s}. Returns the new
14969 @item FLOAT(@var{i})
14970 Returns the floating point equivalent of the integer @var{i}.
14972 @item HIGH(@var{a})
14973 Returns the index of the last member of @var{a}.
14976 Increments the value in the variable @var{v} by one. Returns the new value.
14978 @item INC(@var{v},@var{i})
14979 Increments the value in the variable @var{v} by @var{i}. Returns the
14982 @item INCL(@var{m},@var{s})
14983 Adds the element @var{m} to the set @var{s} if it is not already
14984 there. Returns the new set.
14987 Returns the maximum value of the type @var{t}.
14990 Returns the minimum value of the type @var{t}.
14993 Returns boolean TRUE if @var{i} is an odd number.
14996 Returns the ordinal value of its argument. For example, the ordinal
14997 value of a character is its @sc{ascii} value (on machines supporting
14998 the @sc{ascii} character set). The argument @var{x} must be of an
14999 ordered type, which include integral, character and enumerated types.
15001 @item SIZE(@var{x})
15002 Returns the size of its argument. The argument @var{x} can be a
15003 variable or a type.
15005 @item TRUNC(@var{r})
15006 Returns the integral part of @var{r}.
15008 @item TSIZE(@var{x})
15009 Returns the size of its argument. The argument @var{x} can be a
15010 variable or a type.
15012 @item VAL(@var{t},@var{i})
15013 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15017 @emph{Warning:} Sets and their operations are not yet supported, so
15018 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15022 @cindex Modula-2 constants
15024 @subsubsection Constants
15026 @value{GDBN} allows you to express the constants of Modula-2 in the following
15032 Integer constants are simply a sequence of digits. When used in an
15033 expression, a constant is interpreted to be type-compatible with the
15034 rest of the expression. Hexadecimal integers are specified by a
15035 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15038 Floating point constants appear as a sequence of digits, followed by a
15039 decimal point and another sequence of digits. An optional exponent can
15040 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15041 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15042 digits of the floating point constant must be valid decimal (base 10)
15046 Character constants consist of a single character enclosed by a pair of
15047 like quotes, either single (@code{'}) or double (@code{"}). They may
15048 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15049 followed by a @samp{C}.
15052 String constants consist of a sequence of characters enclosed by a
15053 pair of like quotes, either single (@code{'}) or double (@code{"}).
15054 Escape sequences in the style of C are also allowed. @xref{C
15055 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15059 Enumerated constants consist of an enumerated identifier.
15062 Boolean constants consist of the identifiers @code{TRUE} and
15066 Pointer constants consist of integral values only.
15069 Set constants are not yet supported.
15073 @subsubsection Modula-2 Types
15074 @cindex Modula-2 types
15076 Currently @value{GDBN} can print the following data types in Modula-2
15077 syntax: array types, record types, set types, pointer types, procedure
15078 types, enumerated types, subrange types and base types. You can also
15079 print the contents of variables declared using these type.
15080 This section gives a number of simple source code examples together with
15081 sample @value{GDBN} sessions.
15083 The first example contains the following section of code:
15092 and you can request @value{GDBN} to interrogate the type and value of
15093 @code{r} and @code{s}.
15096 (@value{GDBP}) print s
15098 (@value{GDBP}) ptype s
15100 (@value{GDBP}) print r
15102 (@value{GDBP}) ptype r
15107 Likewise if your source code declares @code{s} as:
15111 s: SET ['A'..'Z'] ;
15115 then you may query the type of @code{s} by:
15118 (@value{GDBP}) ptype s
15119 type = SET ['A'..'Z']
15123 Note that at present you cannot interactively manipulate set
15124 expressions using the debugger.
15126 The following example shows how you might declare an array in Modula-2
15127 and how you can interact with @value{GDBN} to print its type and contents:
15131 s: ARRAY [-10..10] OF CHAR ;
15135 (@value{GDBP}) ptype s
15136 ARRAY [-10..10] OF CHAR
15139 Note that the array handling is not yet complete and although the type
15140 is printed correctly, expression handling still assumes that all
15141 arrays have a lower bound of zero and not @code{-10} as in the example
15144 Here are some more type related Modula-2 examples:
15148 colour = (blue, red, yellow, green) ;
15149 t = [blue..yellow] ;
15157 The @value{GDBN} interaction shows how you can query the data type
15158 and value of a variable.
15161 (@value{GDBP}) print s
15163 (@value{GDBP}) ptype t
15164 type = [blue..yellow]
15168 In this example a Modula-2 array is declared and its contents
15169 displayed. Observe that the contents are written in the same way as
15170 their @code{C} counterparts.
15174 s: ARRAY [1..5] OF CARDINAL ;
15180 (@value{GDBP}) print s
15181 $1 = @{1, 0, 0, 0, 0@}
15182 (@value{GDBP}) ptype s
15183 type = ARRAY [1..5] OF CARDINAL
15186 The Modula-2 language interface to @value{GDBN} also understands
15187 pointer types as shown in this example:
15191 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15198 and you can request that @value{GDBN} describes the type of @code{s}.
15201 (@value{GDBP}) ptype s
15202 type = POINTER TO ARRAY [1..5] OF CARDINAL
15205 @value{GDBN} handles compound types as we can see in this example.
15206 Here we combine array types, record types, pointer types and subrange
15217 myarray = ARRAY myrange OF CARDINAL ;
15218 myrange = [-2..2] ;
15220 s: POINTER TO ARRAY myrange OF foo ;
15224 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15228 (@value{GDBP}) ptype s
15229 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15232 f3 : ARRAY [-2..2] OF CARDINAL;
15237 @subsubsection Modula-2 Defaults
15238 @cindex Modula-2 defaults
15240 If type and range checking are set automatically by @value{GDBN}, they
15241 both default to @code{on} whenever the working language changes to
15242 Modula-2. This happens regardless of whether you or @value{GDBN}
15243 selected the working language.
15245 If you allow @value{GDBN} to set the language automatically, then entering
15246 code compiled from a file whose name ends with @file{.mod} sets the
15247 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15248 Infer the Source Language}, for further details.
15251 @subsubsection Deviations from Standard Modula-2
15252 @cindex Modula-2, deviations from
15254 A few changes have been made to make Modula-2 programs easier to debug.
15255 This is done primarily via loosening its type strictness:
15259 Unlike in standard Modula-2, pointer constants can be formed by
15260 integers. This allows you to modify pointer variables during
15261 debugging. (In standard Modula-2, the actual address contained in a
15262 pointer variable is hidden from you; it can only be modified
15263 through direct assignment to another pointer variable or expression that
15264 returned a pointer.)
15267 C escape sequences can be used in strings and characters to represent
15268 non-printable characters. @value{GDBN} prints out strings with these
15269 escape sequences embedded. Single non-printable characters are
15270 printed using the @samp{CHR(@var{nnn})} format.
15273 The assignment operator (@code{:=}) returns the value of its right-hand
15277 All built-in procedures both modify @emph{and} return their argument.
15281 @subsubsection Modula-2 Type and Range Checks
15282 @cindex Modula-2 checks
15285 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15288 @c FIXME remove warning when type/range checks added
15290 @value{GDBN} considers two Modula-2 variables type equivalent if:
15294 They are of types that have been declared equivalent via a @code{TYPE
15295 @var{t1} = @var{t2}} statement
15298 They have been declared on the same line. (Note: This is true of the
15299 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15302 As long as type checking is enabled, any attempt to combine variables
15303 whose types are not equivalent is an error.
15305 Range checking is done on all mathematical operations, assignment, array
15306 index bounds, and all built-in functions and procedures.
15309 @subsubsection The Scope Operators @code{::} and @code{.}
15311 @cindex @code{.}, Modula-2 scope operator
15312 @cindex colon, doubled as scope operator
15314 @vindex colon-colon@r{, in Modula-2}
15315 @c Info cannot handle :: but TeX can.
15318 @vindex ::@r{, in Modula-2}
15321 There are a few subtle differences between the Modula-2 scope operator
15322 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15327 @var{module} . @var{id}
15328 @var{scope} :: @var{id}
15332 where @var{scope} is the name of a module or a procedure,
15333 @var{module} the name of a module, and @var{id} is any declared
15334 identifier within your program, except another module.
15336 Using the @code{::} operator makes @value{GDBN} search the scope
15337 specified by @var{scope} for the identifier @var{id}. If it is not
15338 found in the specified scope, then @value{GDBN} searches all scopes
15339 enclosing the one specified by @var{scope}.
15341 Using the @code{.} operator makes @value{GDBN} search the current scope for
15342 the identifier specified by @var{id} that was imported from the
15343 definition module specified by @var{module}. With this operator, it is
15344 an error if the identifier @var{id} was not imported from definition
15345 module @var{module}, or if @var{id} is not an identifier in
15349 @subsubsection @value{GDBN} and Modula-2
15351 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15352 Five subcommands of @code{set print} and @code{show print} apply
15353 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15354 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15355 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15356 analogue in Modula-2.
15358 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15359 with any language, is not useful with Modula-2. Its
15360 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15361 created in Modula-2 as they can in C or C@t{++}. However, because an
15362 address can be specified by an integral constant, the construct
15363 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15365 @cindex @code{#} in Modula-2
15366 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15367 interpreted as the beginning of a comment. Use @code{<>} instead.
15373 The extensions made to @value{GDBN} for Ada only support
15374 output from the @sc{gnu} Ada (GNAT) compiler.
15375 Other Ada compilers are not currently supported, and
15376 attempting to debug executables produced by them is most likely
15380 @cindex expressions in Ada
15382 * Ada Mode Intro:: General remarks on the Ada syntax
15383 and semantics supported by Ada mode
15385 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15386 * Additions to Ada:: Extensions of the Ada expression syntax.
15387 * Stopping Before Main Program:: Debugging the program during elaboration.
15388 * Ada Exceptions:: Ada Exceptions
15389 * Ada Tasks:: Listing and setting breakpoints in tasks.
15390 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15391 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15393 * Ada Glitches:: Known peculiarities of Ada mode.
15396 @node Ada Mode Intro
15397 @subsubsection Introduction
15398 @cindex Ada mode, general
15400 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15401 syntax, with some extensions.
15402 The philosophy behind the design of this subset is
15406 That @value{GDBN} should provide basic literals and access to operations for
15407 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15408 leaving more sophisticated computations to subprograms written into the
15409 program (which therefore may be called from @value{GDBN}).
15412 That type safety and strict adherence to Ada language restrictions
15413 are not particularly important to the @value{GDBN} user.
15416 That brevity is important to the @value{GDBN} user.
15419 Thus, for brevity, the debugger acts as if all names declared in
15420 user-written packages are directly visible, even if they are not visible
15421 according to Ada rules, thus making it unnecessary to fully qualify most
15422 names with their packages, regardless of context. Where this causes
15423 ambiguity, @value{GDBN} asks the user's intent.
15425 The debugger will start in Ada mode if it detects an Ada main program.
15426 As for other languages, it will enter Ada mode when stopped in a program that
15427 was translated from an Ada source file.
15429 While in Ada mode, you may use `@t{--}' for comments. This is useful
15430 mostly for documenting command files. The standard @value{GDBN} comment
15431 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15432 middle (to allow based literals).
15434 The debugger supports limited overloading. Given a subprogram call in which
15435 the function symbol has multiple definitions, it will use the number of
15436 actual parameters and some information about their types to attempt to narrow
15437 the set of definitions. It also makes very limited use of context, preferring
15438 procedures to functions in the context of the @code{call} command, and
15439 functions to procedures elsewhere.
15441 @node Omissions from Ada
15442 @subsubsection Omissions from Ada
15443 @cindex Ada, omissions from
15445 Here are the notable omissions from the subset:
15449 Only a subset of the attributes are supported:
15453 @t{'First}, @t{'Last}, and @t{'Length}
15454 on array objects (not on types and subtypes).
15457 @t{'Min} and @t{'Max}.
15460 @t{'Pos} and @t{'Val}.
15466 @t{'Range} on array objects (not subtypes), but only as the right
15467 operand of the membership (@code{in}) operator.
15470 @t{'Access}, @t{'Unchecked_Access}, and
15471 @t{'Unrestricted_Access} (a GNAT extension).
15479 @code{Characters.Latin_1} are not available and
15480 concatenation is not implemented. Thus, escape characters in strings are
15481 not currently available.
15484 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15485 equality of representations. They will generally work correctly
15486 for strings and arrays whose elements have integer or enumeration types.
15487 They may not work correctly for arrays whose element
15488 types have user-defined equality, for arrays of real values
15489 (in particular, IEEE-conformant floating point, because of negative
15490 zeroes and NaNs), and for arrays whose elements contain unused bits with
15491 indeterminate values.
15494 The other component-by-component array operations (@code{and}, @code{or},
15495 @code{xor}, @code{not}, and relational tests other than equality)
15496 are not implemented.
15499 @cindex array aggregates (Ada)
15500 @cindex record aggregates (Ada)
15501 @cindex aggregates (Ada)
15502 There is limited support for array and record aggregates. They are
15503 permitted only on the right sides of assignments, as in these examples:
15506 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15507 (@value{GDBP}) set An_Array := (1, others => 0)
15508 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15509 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15510 (@value{GDBP}) set A_Record := (1, "Peter", True);
15511 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15515 discriminant's value by assigning an aggregate has an
15516 undefined effect if that discriminant is used within the record.
15517 However, you can first modify discriminants by directly assigning to
15518 them (which normally would not be allowed in Ada), and then performing an
15519 aggregate assignment. For example, given a variable @code{A_Rec}
15520 declared to have a type such as:
15523 type Rec (Len : Small_Integer := 0) is record
15525 Vals : IntArray (1 .. Len);
15529 you can assign a value with a different size of @code{Vals} with two
15533 (@value{GDBP}) set A_Rec.Len := 4
15534 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15537 As this example also illustrates, @value{GDBN} is very loose about the usual
15538 rules concerning aggregates. You may leave out some of the
15539 components of an array or record aggregate (such as the @code{Len}
15540 component in the assignment to @code{A_Rec} above); they will retain their
15541 original values upon assignment. You may freely use dynamic values as
15542 indices in component associations. You may even use overlapping or
15543 redundant component associations, although which component values are
15544 assigned in such cases is not defined.
15547 Calls to dispatching subprograms are not implemented.
15550 The overloading algorithm is much more limited (i.e., less selective)
15551 than that of real Ada. It makes only limited use of the context in
15552 which a subexpression appears to resolve its meaning, and it is much
15553 looser in its rules for allowing type matches. As a result, some
15554 function calls will be ambiguous, and the user will be asked to choose
15555 the proper resolution.
15558 The @code{new} operator is not implemented.
15561 Entry calls are not implemented.
15564 Aside from printing, arithmetic operations on the native VAX floating-point
15565 formats are not supported.
15568 It is not possible to slice a packed array.
15571 The names @code{True} and @code{False}, when not part of a qualified name,
15572 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15574 Should your program
15575 redefine these names in a package or procedure (at best a dubious practice),
15576 you will have to use fully qualified names to access their new definitions.
15579 @node Additions to Ada
15580 @subsubsection Additions to Ada
15581 @cindex Ada, deviations from
15583 As it does for other languages, @value{GDBN} makes certain generic
15584 extensions to Ada (@pxref{Expressions}):
15588 If the expression @var{E} is a variable residing in memory (typically
15589 a local variable or array element) and @var{N} is a positive integer,
15590 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15591 @var{N}-1 adjacent variables following it in memory as an array. In
15592 Ada, this operator is generally not necessary, since its prime use is
15593 in displaying parts of an array, and slicing will usually do this in
15594 Ada. However, there are occasional uses when debugging programs in
15595 which certain debugging information has been optimized away.
15598 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15599 appears in function or file @var{B}.'' When @var{B} is a file name,
15600 you must typically surround it in single quotes.
15603 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15604 @var{type} that appears at address @var{addr}.''
15607 A name starting with @samp{$} is a convenience variable
15608 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15611 In addition, @value{GDBN} provides a few other shortcuts and outright
15612 additions specific to Ada:
15616 The assignment statement is allowed as an expression, returning
15617 its right-hand operand as its value. Thus, you may enter
15620 (@value{GDBP}) set x := y + 3
15621 (@value{GDBP}) print A(tmp := y + 1)
15625 The semicolon is allowed as an ``operator,'' returning as its value
15626 the value of its right-hand operand.
15627 This allows, for example,
15628 complex conditional breaks:
15631 (@value{GDBP}) break f
15632 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15636 Rather than use catenation and symbolic character names to introduce special
15637 characters into strings, one may instead use a special bracket notation,
15638 which is also used to print strings. A sequence of characters of the form
15639 @samp{["@var{XX}"]} within a string or character literal denotes the
15640 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15641 sequence of characters @samp{["""]} also denotes a single quotation mark
15642 in strings. For example,
15644 "One line.["0a"]Next line.["0a"]"
15647 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15651 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15652 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15656 (@value{GDBP}) print 'max(x, y)
15660 When printing arrays, @value{GDBN} uses positional notation when the
15661 array has a lower bound of 1, and uses a modified named notation otherwise.
15662 For example, a one-dimensional array of three integers with a lower bound
15663 of 3 might print as
15670 That is, in contrast to valid Ada, only the first component has a @code{=>}
15674 You may abbreviate attributes in expressions with any unique,
15675 multi-character subsequence of
15676 their names (an exact match gets preference).
15677 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15678 in place of @t{a'length}.
15681 @cindex quoting Ada internal identifiers
15682 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15683 to lower case. The GNAT compiler uses upper-case characters for
15684 some of its internal identifiers, which are normally of no interest to users.
15685 For the rare occasions when you actually have to look at them,
15686 enclose them in angle brackets to avoid the lower-case mapping.
15689 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15693 Printing an object of class-wide type or dereferencing an
15694 access-to-class-wide value will display all the components of the object's
15695 specific type (as indicated by its run-time tag). Likewise, component
15696 selection on such a value will operate on the specific type of the
15701 @node Stopping Before Main Program
15702 @subsubsection Stopping at the Very Beginning
15704 @cindex breakpointing Ada elaboration code
15705 It is sometimes necessary to debug the program during elaboration, and
15706 before reaching the main procedure.
15707 As defined in the Ada Reference
15708 Manual, the elaboration code is invoked from a procedure called
15709 @code{adainit}. To run your program up to the beginning of
15710 elaboration, simply use the following two commands:
15711 @code{tbreak adainit} and @code{run}.
15713 @node Ada Exceptions
15714 @subsubsection Ada Exceptions
15716 A command is provided to list all Ada exceptions:
15719 @kindex info exceptions
15720 @item info exceptions
15721 @itemx info exceptions @var{regexp}
15722 The @code{info exceptions} command allows you to list all Ada exceptions
15723 defined within the program being debugged, as well as their addresses.
15724 With a regular expression, @var{regexp}, as argument, only those exceptions
15725 whose names match @var{regexp} are listed.
15728 Below is a small example, showing how the command can be used, first
15729 without argument, and next with a regular expression passed as an
15733 (@value{GDBP}) info exceptions
15734 All defined Ada exceptions:
15735 constraint_error: 0x613da0
15736 program_error: 0x613d20
15737 storage_error: 0x613ce0
15738 tasking_error: 0x613ca0
15739 const.aint_global_e: 0x613b00
15740 (@value{GDBP}) info exceptions const.aint
15741 All Ada exceptions matching regular expression "const.aint":
15742 constraint_error: 0x613da0
15743 const.aint_global_e: 0x613b00
15746 It is also possible to ask @value{GDBN} to stop your program's execution
15747 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15750 @subsubsection Extensions for Ada Tasks
15751 @cindex Ada, tasking
15753 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15754 @value{GDBN} provides the following task-related commands:
15759 This command shows a list of current Ada tasks, as in the following example:
15766 (@value{GDBP}) info tasks
15767 ID TID P-ID Pri State Name
15768 1 8088000 0 15 Child Activation Wait main_task
15769 2 80a4000 1 15 Accept Statement b
15770 3 809a800 1 15 Child Activation Wait a
15771 * 4 80ae800 3 15 Runnable c
15776 In this listing, the asterisk before the last task indicates it to be the
15777 task currently being inspected.
15781 Represents @value{GDBN}'s internal task number.
15787 The parent's task ID (@value{GDBN}'s internal task number).
15790 The base priority of the task.
15793 Current state of the task.
15797 The task has been created but has not been activated. It cannot be
15801 The task is not blocked for any reason known to Ada. (It may be waiting
15802 for a mutex, though.) It is conceptually "executing" in normal mode.
15805 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15806 that were waiting on terminate alternatives have been awakened and have
15807 terminated themselves.
15809 @item Child Activation Wait
15810 The task is waiting for created tasks to complete activation.
15812 @item Accept Statement
15813 The task is waiting on an accept or selective wait statement.
15815 @item Waiting on entry call
15816 The task is waiting on an entry call.
15818 @item Async Select Wait
15819 The task is waiting to start the abortable part of an asynchronous
15823 The task is waiting on a select statement with only a delay
15826 @item Child Termination Wait
15827 The task is sleeping having completed a master within itself, and is
15828 waiting for the tasks dependent on that master to become terminated or
15829 waiting on a terminate Phase.
15831 @item Wait Child in Term Alt
15832 The task is sleeping waiting for tasks on terminate alternatives to
15833 finish terminating.
15835 @item Accepting RV with @var{taskno}
15836 The task is accepting a rendez-vous with the task @var{taskno}.
15840 Name of the task in the program.
15844 @kindex info task @var{taskno}
15845 @item info task @var{taskno}
15846 This command shows detailled informations on the specified task, as in
15847 the following example:
15852 (@value{GDBP}) info tasks
15853 ID TID P-ID Pri State Name
15854 1 8077880 0 15 Child Activation Wait main_task
15855 * 2 807c468 1 15 Runnable task_1
15856 (@value{GDBP}) info task 2
15857 Ada Task: 0x807c468
15860 Parent: 1 (main_task)
15866 @kindex task@r{ (Ada)}
15867 @cindex current Ada task ID
15868 This command prints the ID of the current task.
15874 (@value{GDBP}) info tasks
15875 ID TID P-ID Pri State Name
15876 1 8077870 0 15 Child Activation Wait main_task
15877 * 2 807c458 1 15 Runnable t
15878 (@value{GDBP}) task
15879 [Current task is 2]
15882 @item task @var{taskno}
15883 @cindex Ada task switching
15884 This command is like the @code{thread @var{threadno}}
15885 command (@pxref{Threads}). It switches the context of debugging
15886 from the current task to the given task.
15892 (@value{GDBP}) info tasks
15893 ID TID P-ID Pri State Name
15894 1 8077870 0 15 Child Activation Wait main_task
15895 * 2 807c458 1 15 Runnable t
15896 (@value{GDBP}) task 1
15897 [Switching to task 1]
15898 #0 0x8067726 in pthread_cond_wait ()
15900 #0 0x8067726 in pthread_cond_wait ()
15901 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15902 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15903 #3 0x806153e in system.tasking.stages.activate_tasks ()
15904 #4 0x804aacc in un () at un.adb:5
15907 @item break @var{linespec} task @var{taskno}
15908 @itemx break @var{linespec} task @var{taskno} if @dots{}
15909 @cindex breakpoints and tasks, in Ada
15910 @cindex task breakpoints, in Ada
15911 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15912 These commands are like the @code{break @dots{} thread @dots{}}
15913 command (@pxref{Thread Stops}). The
15914 @var{linespec} argument specifies source lines, as described
15915 in @ref{Specify Location}.
15917 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15918 to specify that you only want @value{GDBN} to stop the program when a
15919 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
15920 numeric task identifiers assigned by @value{GDBN}, shown in the first
15921 column of the @samp{info tasks} display.
15923 If you do not specify @samp{task @var{taskno}} when you set a
15924 breakpoint, the breakpoint applies to @emph{all} tasks of your
15927 You can use the @code{task} qualifier on conditional breakpoints as
15928 well; in this case, place @samp{task @var{taskno}} before the
15929 breakpoint condition (before the @code{if}).
15937 (@value{GDBP}) info tasks
15938 ID TID P-ID Pri State Name
15939 1 140022020 0 15 Child Activation Wait main_task
15940 2 140045060 1 15 Accept/Select Wait t2
15941 3 140044840 1 15 Runnable t1
15942 * 4 140056040 1 15 Runnable t3
15943 (@value{GDBP}) b 15 task 2
15944 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15945 (@value{GDBP}) cont
15950 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15952 (@value{GDBP}) info tasks
15953 ID TID P-ID Pri State Name
15954 1 140022020 0 15 Child Activation Wait main_task
15955 * 2 140045060 1 15 Runnable t2
15956 3 140044840 1 15 Runnable t1
15957 4 140056040 1 15 Delay Sleep t3
15961 @node Ada Tasks and Core Files
15962 @subsubsection Tasking Support when Debugging Core Files
15963 @cindex Ada tasking and core file debugging
15965 When inspecting a core file, as opposed to debugging a live program,
15966 tasking support may be limited or even unavailable, depending on
15967 the platform being used.
15968 For instance, on x86-linux, the list of tasks is available, but task
15969 switching is not supported.
15971 On certain platforms, the debugger needs to perform some
15972 memory writes in order to provide Ada tasking support. When inspecting
15973 a core file, this means that the core file must be opened with read-write
15974 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15975 Under these circumstances, you should make a backup copy of the core
15976 file before inspecting it with @value{GDBN}.
15978 @node Ravenscar Profile
15979 @subsubsection Tasking Support when using the Ravenscar Profile
15980 @cindex Ravenscar Profile
15982 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15983 specifically designed for systems with safety-critical real-time
15987 @kindex set ravenscar task-switching on
15988 @cindex task switching with program using Ravenscar Profile
15989 @item set ravenscar task-switching on
15990 Allows task switching when debugging a program that uses the Ravenscar
15991 Profile. This is the default.
15993 @kindex set ravenscar task-switching off
15994 @item set ravenscar task-switching off
15995 Turn off task switching when debugging a program that uses the Ravenscar
15996 Profile. This is mostly intended to disable the code that adds support
15997 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15998 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15999 To be effective, this command should be run before the program is started.
16001 @kindex show ravenscar task-switching
16002 @item show ravenscar task-switching
16003 Show whether it is possible to switch from task to task in a program
16004 using the Ravenscar Profile.
16009 @subsubsection Known Peculiarities of Ada Mode
16010 @cindex Ada, problems
16012 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16013 we know of several problems with and limitations of Ada mode in
16015 some of which will be fixed with planned future releases of the debugger
16016 and the GNU Ada compiler.
16020 Static constants that the compiler chooses not to materialize as objects in
16021 storage are invisible to the debugger.
16024 Named parameter associations in function argument lists are ignored (the
16025 argument lists are treated as positional).
16028 Many useful library packages are currently invisible to the debugger.
16031 Fixed-point arithmetic, conversions, input, and output is carried out using
16032 floating-point arithmetic, and may give results that only approximate those on
16036 The GNAT compiler never generates the prefix @code{Standard} for any of
16037 the standard symbols defined by the Ada language. @value{GDBN} knows about
16038 this: it will strip the prefix from names when you use it, and will never
16039 look for a name you have so qualified among local symbols, nor match against
16040 symbols in other packages or subprograms. If you have
16041 defined entities anywhere in your program other than parameters and
16042 local variables whose simple names match names in @code{Standard},
16043 GNAT's lack of qualification here can cause confusion. When this happens,
16044 you can usually resolve the confusion
16045 by qualifying the problematic names with package
16046 @code{Standard} explicitly.
16049 Older versions of the compiler sometimes generate erroneous debugging
16050 information, resulting in the debugger incorrectly printing the value
16051 of affected entities. In some cases, the debugger is able to work
16052 around an issue automatically. In other cases, the debugger is able
16053 to work around the issue, but the work-around has to be specifically
16056 @kindex set ada trust-PAD-over-XVS
16057 @kindex show ada trust-PAD-over-XVS
16060 @item set ada trust-PAD-over-XVS on
16061 Configure GDB to strictly follow the GNAT encoding when computing the
16062 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16063 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16064 a complete description of the encoding used by the GNAT compiler).
16065 This is the default.
16067 @item set ada trust-PAD-over-XVS off
16068 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16069 sometimes prints the wrong value for certain entities, changing @code{ada
16070 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16071 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16072 @code{off}, but this incurs a slight performance penalty, so it is
16073 recommended to leave this setting to @code{on} unless necessary.
16077 @cindex GNAT descriptive types
16078 @cindex GNAT encoding
16079 Internally, the debugger also relies on the compiler following a number
16080 of conventions known as the @samp{GNAT Encoding}, all documented in
16081 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16082 how the debugging information should be generated for certain types.
16083 In particular, this convention makes use of @dfn{descriptive types},
16084 which are artificial types generated purely to help the debugger.
16086 These encodings were defined at a time when the debugging information
16087 format used was not powerful enough to describe some of the more complex
16088 types available in Ada. Since DWARF allows us to express nearly all
16089 Ada features, the long-term goal is to slowly replace these descriptive
16090 types by their pure DWARF equivalent. To facilitate that transition,
16091 a new maintenance option is available to force the debugger to ignore
16092 those descriptive types. It allows the user to quickly evaluate how
16093 well @value{GDBN} works without them.
16097 @kindex maint ada set ignore-descriptive-types
16098 @item maintenance ada set ignore-descriptive-types [on|off]
16099 Control whether the debugger should ignore descriptive types.
16100 The default is not to ignore descriptives types (@code{off}).
16102 @kindex maint ada show ignore-descriptive-types
16103 @item maintenance ada show ignore-descriptive-types
16104 Show if descriptive types are ignored by @value{GDBN}.
16108 @node Unsupported Languages
16109 @section Unsupported Languages
16111 @cindex unsupported languages
16112 @cindex minimal language
16113 In addition to the other fully-supported programming languages,
16114 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16115 It does not represent a real programming language, but provides a set
16116 of capabilities close to what the C or assembly languages provide.
16117 This should allow most simple operations to be performed while debugging
16118 an application that uses a language currently not supported by @value{GDBN}.
16120 If the language is set to @code{auto}, @value{GDBN} will automatically
16121 select this language if the current frame corresponds to an unsupported
16125 @chapter Examining the Symbol Table
16127 The commands described in this chapter allow you to inquire about the
16128 symbols (names of variables, functions and types) defined in your
16129 program. This information is inherent in the text of your program and
16130 does not change as your program executes. @value{GDBN} finds it in your
16131 program's symbol table, in the file indicated when you started @value{GDBN}
16132 (@pxref{File Options, ,Choosing Files}), or by one of the
16133 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16135 @cindex symbol names
16136 @cindex names of symbols
16137 @cindex quoting names
16138 Occasionally, you may need to refer to symbols that contain unusual
16139 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16140 most frequent case is in referring to static variables in other
16141 source files (@pxref{Variables,,Program Variables}). File names
16142 are recorded in object files as debugging symbols, but @value{GDBN} would
16143 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16144 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16145 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16152 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16155 @cindex case-insensitive symbol names
16156 @cindex case sensitivity in symbol names
16157 @kindex set case-sensitive
16158 @item set case-sensitive on
16159 @itemx set case-sensitive off
16160 @itemx set case-sensitive auto
16161 Normally, when @value{GDBN} looks up symbols, it matches their names
16162 with case sensitivity determined by the current source language.
16163 Occasionally, you may wish to control that. The command @code{set
16164 case-sensitive} lets you do that by specifying @code{on} for
16165 case-sensitive matches or @code{off} for case-insensitive ones. If
16166 you specify @code{auto}, case sensitivity is reset to the default
16167 suitable for the source language. The default is case-sensitive
16168 matches for all languages except for Fortran, for which the default is
16169 case-insensitive matches.
16171 @kindex show case-sensitive
16172 @item show case-sensitive
16173 This command shows the current setting of case sensitivity for symbols
16176 @kindex set print type methods
16177 @item set print type methods
16178 @itemx set print type methods on
16179 @itemx set print type methods off
16180 Normally, when @value{GDBN} prints a class, it displays any methods
16181 declared in that class. You can control this behavior either by
16182 passing the appropriate flag to @code{ptype}, or using @command{set
16183 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16184 display the methods; this is the default. Specifying @code{off} will
16185 cause @value{GDBN} to omit the methods.
16187 @kindex show print type methods
16188 @item show print type methods
16189 This command shows the current setting of method display when printing
16192 @kindex set print type typedefs
16193 @item set print type typedefs
16194 @itemx set print type typedefs on
16195 @itemx set print type typedefs off
16197 Normally, when @value{GDBN} prints a class, it displays any typedefs
16198 defined in that class. You can control this behavior either by
16199 passing the appropriate flag to @code{ptype}, or using @command{set
16200 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16201 display the typedef definitions; this is the default. Specifying
16202 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16203 Note that this controls whether the typedef definition itself is
16204 printed, not whether typedef names are substituted when printing other
16207 @kindex show print type typedefs
16208 @item show print type typedefs
16209 This command shows the current setting of typedef display when
16212 @kindex info address
16213 @cindex address of a symbol
16214 @item info address @var{symbol}
16215 Describe where the data for @var{symbol} is stored. For a register
16216 variable, this says which register it is kept in. For a non-register
16217 local variable, this prints the stack-frame offset at which the variable
16220 Note the contrast with @samp{print &@var{symbol}}, which does not work
16221 at all for a register variable, and for a stack local variable prints
16222 the exact address of the current instantiation of the variable.
16224 @kindex info symbol
16225 @cindex symbol from address
16226 @cindex closest symbol and offset for an address
16227 @item info symbol @var{addr}
16228 Print the name of a symbol which is stored at the address @var{addr}.
16229 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16230 nearest symbol and an offset from it:
16233 (@value{GDBP}) info symbol 0x54320
16234 _initialize_vx + 396 in section .text
16238 This is the opposite of the @code{info address} command. You can use
16239 it to find out the name of a variable or a function given its address.
16241 For dynamically linked executables, the name of executable or shared
16242 library containing the symbol is also printed:
16245 (@value{GDBP}) info symbol 0x400225
16246 _start + 5 in section .text of /tmp/a.out
16247 (@value{GDBP}) info symbol 0x2aaaac2811cf
16248 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16253 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16254 Demangle @var{name}.
16255 If @var{language} is provided it is the name of the language to demangle
16256 @var{name} in. Otherwise @var{name} is demangled in the current language.
16258 The @samp{--} option specifies the end of options,
16259 and is useful when @var{name} begins with a dash.
16261 The parameter @code{demangle-style} specifies how to interpret the kind
16262 of mangling used. @xref{Print Settings}.
16265 @item whatis[/@var{flags}] [@var{arg}]
16266 Print the data type of @var{arg}, which can be either an expression
16267 or a name of a data type. With no argument, print the data type of
16268 @code{$}, the last value in the value history.
16270 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16271 is not actually evaluated, and any side-effecting operations (such as
16272 assignments or function calls) inside it do not take place.
16274 If @var{arg} is a variable or an expression, @code{whatis} prints its
16275 literal type as it is used in the source code. If the type was
16276 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16277 the data type underlying the @code{typedef}. If the type of the
16278 variable or the expression is a compound data type, such as
16279 @code{struct} or @code{class}, @code{whatis} never prints their
16280 fields or methods. It just prints the @code{struct}/@code{class}
16281 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16282 such a compound data type, use @code{ptype}.
16284 If @var{arg} is a type name that was defined using @code{typedef},
16285 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16286 Unrolling means that @code{whatis} will show the underlying type used
16287 in the @code{typedef} declaration of @var{arg}. However, if that
16288 underlying type is also a @code{typedef}, @code{whatis} will not
16291 For C code, the type names may also have the form @samp{class
16292 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16293 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16295 @var{flags} can be used to modify how the type is displayed.
16296 Available flags are:
16300 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16301 parameters and typedefs defined in a class when printing the class'
16302 members. The @code{/r} flag disables this.
16305 Do not print methods defined in the class.
16308 Print methods defined in the class. This is the default, but the flag
16309 exists in case you change the default with @command{set print type methods}.
16312 Do not print typedefs defined in the class. Note that this controls
16313 whether the typedef definition itself is printed, not whether typedef
16314 names are substituted when printing other types.
16317 Print typedefs defined in the class. This is the default, but the flag
16318 exists in case you change the default with @command{set print type typedefs}.
16322 @item ptype[/@var{flags}] [@var{arg}]
16323 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16324 detailed description of the type, instead of just the name of the type.
16325 @xref{Expressions, ,Expressions}.
16327 Contrary to @code{whatis}, @code{ptype} always unrolls any
16328 @code{typedef}s in its argument declaration, whether the argument is
16329 a variable, expression, or a data type. This means that @code{ptype}
16330 of a variable or an expression will not print literally its type as
16331 present in the source code---use @code{whatis} for that. @code{typedef}s at
16332 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16333 fields, methods and inner @code{class typedef}s of @code{struct}s,
16334 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16336 For example, for this variable declaration:
16339 typedef double real_t;
16340 struct complex @{ real_t real; double imag; @};
16341 typedef struct complex complex_t;
16343 real_t *real_pointer_var;
16347 the two commands give this output:
16351 (@value{GDBP}) whatis var
16353 (@value{GDBP}) ptype var
16354 type = struct complex @{
16358 (@value{GDBP}) whatis complex_t
16359 type = struct complex
16360 (@value{GDBP}) whatis struct complex
16361 type = struct complex
16362 (@value{GDBP}) ptype struct complex
16363 type = struct complex @{
16367 (@value{GDBP}) whatis real_pointer_var
16369 (@value{GDBP}) ptype real_pointer_var
16375 As with @code{whatis}, using @code{ptype} without an argument refers to
16376 the type of @code{$}, the last value in the value history.
16378 @cindex incomplete type
16379 Sometimes, programs use opaque data types or incomplete specifications
16380 of complex data structure. If the debug information included in the
16381 program does not allow @value{GDBN} to display a full declaration of
16382 the data type, it will say @samp{<incomplete type>}. For example,
16383 given these declarations:
16387 struct foo *fooptr;
16391 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16394 (@value{GDBP}) ptype foo
16395 $1 = <incomplete type>
16399 ``Incomplete type'' is C terminology for data types that are not
16400 completely specified.
16403 @item info types @var{regexp}
16405 Print a brief description of all types whose names match the regular
16406 expression @var{regexp} (or all types in your program, if you supply
16407 no argument). Each complete typename is matched as though it were a
16408 complete line; thus, @samp{i type value} gives information on all
16409 types in your program whose names include the string @code{value}, but
16410 @samp{i type ^value$} gives information only on types whose complete
16411 name is @code{value}.
16413 This command differs from @code{ptype} in two ways: first, like
16414 @code{whatis}, it does not print a detailed description; second, it
16415 lists all source files where a type is defined.
16417 @kindex info type-printers
16418 @item info type-printers
16419 Versions of @value{GDBN} that ship with Python scripting enabled may
16420 have ``type printers'' available. When using @command{ptype} or
16421 @command{whatis}, these printers are consulted when the name of a type
16422 is needed. @xref{Type Printing API}, for more information on writing
16425 @code{info type-printers} displays all the available type printers.
16427 @kindex enable type-printer
16428 @kindex disable type-printer
16429 @item enable type-printer @var{name}@dots{}
16430 @item disable type-printer @var{name}@dots{}
16431 These commands can be used to enable or disable type printers.
16434 @cindex local variables
16435 @item info scope @var{location}
16436 List all the variables local to a particular scope. This command
16437 accepts a @var{location} argument---a function name, a source line, or
16438 an address preceded by a @samp{*}, and prints all the variables local
16439 to the scope defined by that location. (@xref{Specify Location}, for
16440 details about supported forms of @var{location}.) For example:
16443 (@value{GDBP}) @b{info scope command_line_handler}
16444 Scope for command_line_handler:
16445 Symbol rl is an argument at stack/frame offset 8, length 4.
16446 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16447 Symbol linelength is in static storage at address 0x150a1c, length 4.
16448 Symbol p is a local variable in register $esi, length 4.
16449 Symbol p1 is a local variable in register $ebx, length 4.
16450 Symbol nline is a local variable in register $edx, length 4.
16451 Symbol repeat is a local variable at frame offset -8, length 4.
16455 This command is especially useful for determining what data to collect
16456 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16459 @kindex info source
16461 Show information about the current source file---that is, the source file for
16462 the function containing the current point of execution:
16465 the name of the source file, and the directory containing it,
16467 the directory it was compiled in,
16469 its length, in lines,
16471 which programming language it is written in,
16473 if the debug information provides it, the program that compiled the file
16474 (which may include, e.g., the compiler version and command line arguments),
16476 whether the executable includes debugging information for that file, and
16477 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16479 whether the debugging information includes information about
16480 preprocessor macros.
16484 @kindex info sources
16486 Print the names of all source files in your program for which there is
16487 debugging information, organized into two lists: files whose symbols
16488 have already been read, and files whose symbols will be read when needed.
16490 @kindex info functions
16491 @item info functions
16492 Print the names and data types of all defined functions.
16494 @item info functions @var{regexp}
16495 Print the names and data types of all defined functions
16496 whose names contain a match for regular expression @var{regexp}.
16497 Thus, @samp{info fun step} finds all functions whose names
16498 include @code{step}; @samp{info fun ^step} finds those whose names
16499 start with @code{step}. If a function name contains characters
16500 that conflict with the regular expression language (e.g.@:
16501 @samp{operator*()}), they may be quoted with a backslash.
16503 @kindex info variables
16504 @item info variables
16505 Print the names and data types of all variables that are defined
16506 outside of functions (i.e.@: excluding local variables).
16508 @item info variables @var{regexp}
16509 Print the names and data types of all variables (except for local
16510 variables) whose names contain a match for regular expression
16513 @kindex info classes
16514 @cindex Objective-C, classes and selectors
16516 @itemx info classes @var{regexp}
16517 Display all Objective-C classes in your program, or
16518 (with the @var{regexp} argument) all those matching a particular regular
16521 @kindex info selectors
16522 @item info selectors
16523 @itemx info selectors @var{regexp}
16524 Display all Objective-C selectors in your program, or
16525 (with the @var{regexp} argument) all those matching a particular regular
16529 This was never implemented.
16530 @kindex info methods
16532 @itemx info methods @var{regexp}
16533 The @code{info methods} command permits the user to examine all defined
16534 methods within C@t{++} program, or (with the @var{regexp} argument) a
16535 specific set of methods found in the various C@t{++} classes. Many
16536 C@t{++} classes provide a large number of methods. Thus, the output
16537 from the @code{ptype} command can be overwhelming and hard to use. The
16538 @code{info-methods} command filters the methods, printing only those
16539 which match the regular-expression @var{regexp}.
16542 @cindex opaque data types
16543 @kindex set opaque-type-resolution
16544 @item set opaque-type-resolution on
16545 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16546 declared as a pointer to a @code{struct}, @code{class}, or
16547 @code{union}---for example, @code{struct MyType *}---that is used in one
16548 source file although the full declaration of @code{struct MyType} is in
16549 another source file. The default is on.
16551 A change in the setting of this subcommand will not take effect until
16552 the next time symbols for a file are loaded.
16554 @item set opaque-type-resolution off
16555 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16556 is printed as follows:
16558 @{<no data fields>@}
16561 @kindex show opaque-type-resolution
16562 @item show opaque-type-resolution
16563 Show whether opaque types are resolved or not.
16565 @kindex set print symbol-loading
16566 @cindex print messages when symbols are loaded
16567 @item set print symbol-loading
16568 @itemx set print symbol-loading full
16569 @itemx set print symbol-loading brief
16570 @itemx set print symbol-loading off
16571 The @code{set print symbol-loading} command allows you to control the
16572 printing of messages when @value{GDBN} loads symbol information.
16573 By default a message is printed for the executable and one for each
16574 shared library, and normally this is what you want. However, when
16575 debugging apps with large numbers of shared libraries these messages
16577 When set to @code{brief} a message is printed for each executable,
16578 and when @value{GDBN} loads a collection of shared libraries at once
16579 it will only print one message regardless of the number of shared
16580 libraries. When set to @code{off} no messages are printed.
16582 @kindex show print symbol-loading
16583 @item show print symbol-loading
16584 Show whether messages will be printed when a @value{GDBN} command
16585 entered from the keyboard causes symbol information to be loaded.
16587 @kindex maint print symbols
16588 @cindex symbol dump
16589 @kindex maint print psymbols
16590 @cindex partial symbol dump
16591 @kindex maint print msymbols
16592 @cindex minimal symbol dump
16593 @item maint print symbols @var{filename}
16594 @itemx maint print psymbols @var{filename}
16595 @itemx maint print msymbols @var{filename}
16596 Write a dump of debugging symbol data into the file @var{filename}.
16597 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16598 symbols with debugging data are included. If you use @samp{maint print
16599 symbols}, @value{GDBN} includes all the symbols for which it has already
16600 collected full details: that is, @var{filename} reflects symbols for
16601 only those files whose symbols @value{GDBN} has read. You can use the
16602 command @code{info sources} to find out which files these are. If you
16603 use @samp{maint print psymbols} instead, the dump shows information about
16604 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16605 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16606 @samp{maint print msymbols} dumps just the minimal symbol information
16607 required for each object file from which @value{GDBN} has read some symbols.
16608 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16609 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16611 @kindex maint info symtabs
16612 @kindex maint info psymtabs
16613 @cindex listing @value{GDBN}'s internal symbol tables
16614 @cindex symbol tables, listing @value{GDBN}'s internal
16615 @cindex full symbol tables, listing @value{GDBN}'s internal
16616 @cindex partial symbol tables, listing @value{GDBN}'s internal
16617 @item maint info symtabs @r{[} @var{regexp} @r{]}
16618 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16620 List the @code{struct symtab} or @code{struct partial_symtab}
16621 structures whose names match @var{regexp}. If @var{regexp} is not
16622 given, list them all. The output includes expressions which you can
16623 copy into a @value{GDBN} debugging this one to examine a particular
16624 structure in more detail. For example:
16627 (@value{GDBP}) maint info psymtabs dwarf2read
16628 @{ objfile /home/gnu/build/gdb/gdb
16629 ((struct objfile *) 0x82e69d0)
16630 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16631 ((struct partial_symtab *) 0x8474b10)
16634 text addresses 0x814d3c8 -- 0x8158074
16635 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16636 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16637 dependencies (none)
16640 (@value{GDBP}) maint info symtabs
16644 We see that there is one partial symbol table whose filename contains
16645 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16646 and we see that @value{GDBN} has not read in any symtabs yet at all.
16647 If we set a breakpoint on a function, that will cause @value{GDBN} to
16648 read the symtab for the compilation unit containing that function:
16651 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16652 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16654 (@value{GDBP}) maint info symtabs
16655 @{ objfile /home/gnu/build/gdb/gdb
16656 ((struct objfile *) 0x82e69d0)
16657 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16658 ((struct symtab *) 0x86c1f38)
16661 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16662 linetable ((struct linetable *) 0x8370fa0)
16663 debugformat DWARF 2
16669 @kindex maint set symbol-cache-size
16670 @cindex symbol cache size
16671 @item maint set symbol-cache-size @var{size}
16672 Set the size of the symbol cache to @var{size}.
16673 The default size is intended to be good enough for debugging
16674 most applications. This option exists to allow for experimenting
16675 with different sizes.
16677 @kindex maint show symbol-cache-size
16678 @item maint show symbol-cache-size
16679 Show the size of the symbol cache.
16681 @kindex maint print symbol-cache
16682 @cindex symbol cache, printing its contents
16683 @item maint print symbol-cache
16684 Print the contents of the symbol cache.
16685 This is useful when debugging symbol cache issues.
16687 @kindex maint print symbol-cache-statistics
16688 @cindex symbol cache, printing usage statistics
16689 @item maint print symbol-cache-statistics
16690 Print symbol cache usage statistics.
16691 This helps determine how well the cache is being utilized.
16693 @kindex maint flush-symbol-cache
16694 @cindex symbol cache, flushing
16695 @item maint flush-symbol-cache
16696 Flush the contents of the symbol cache, all entries are removed.
16697 This command is useful when debugging the symbol cache.
16698 It is also useful when collecting performance data.
16703 @chapter Altering Execution
16705 Once you think you have found an error in your program, you might want to
16706 find out for certain whether correcting the apparent error would lead to
16707 correct results in the rest of the run. You can find the answer by
16708 experiment, using the @value{GDBN} features for altering execution of the
16711 For example, you can store new values into variables or memory
16712 locations, give your program a signal, restart it at a different
16713 address, or even return prematurely from a function.
16716 * Assignment:: Assignment to variables
16717 * Jumping:: Continuing at a different address
16718 * Signaling:: Giving your program a signal
16719 * Returning:: Returning from a function
16720 * Calling:: Calling your program's functions
16721 * Patching:: Patching your program
16722 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
16726 @section Assignment to Variables
16729 @cindex setting variables
16730 To alter the value of a variable, evaluate an assignment expression.
16731 @xref{Expressions, ,Expressions}. For example,
16738 stores the value 4 into the variable @code{x}, and then prints the
16739 value of the assignment expression (which is 4).
16740 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16741 information on operators in supported languages.
16743 @kindex set variable
16744 @cindex variables, setting
16745 If you are not interested in seeing the value of the assignment, use the
16746 @code{set} command instead of the @code{print} command. @code{set} is
16747 really the same as @code{print} except that the expression's value is
16748 not printed and is not put in the value history (@pxref{Value History,
16749 ,Value History}). The expression is evaluated only for its effects.
16751 If the beginning of the argument string of the @code{set} command
16752 appears identical to a @code{set} subcommand, use the @code{set
16753 variable} command instead of just @code{set}. This command is identical
16754 to @code{set} except for its lack of subcommands. For example, if your
16755 program has a variable @code{width}, you get an error if you try to set
16756 a new value with just @samp{set width=13}, because @value{GDBN} has the
16757 command @code{set width}:
16760 (@value{GDBP}) whatis width
16762 (@value{GDBP}) p width
16764 (@value{GDBP}) set width=47
16765 Invalid syntax in expression.
16769 The invalid expression, of course, is @samp{=47}. In
16770 order to actually set the program's variable @code{width}, use
16773 (@value{GDBP}) set var width=47
16776 Because the @code{set} command has many subcommands that can conflict
16777 with the names of program variables, it is a good idea to use the
16778 @code{set variable} command instead of just @code{set}. For example, if
16779 your program has a variable @code{g}, you run into problems if you try
16780 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16781 the command @code{set gnutarget}, abbreviated @code{set g}:
16785 (@value{GDBP}) whatis g
16789 (@value{GDBP}) set g=4
16793 The program being debugged has been started already.
16794 Start it from the beginning? (y or n) y
16795 Starting program: /home/smith/cc_progs/a.out
16796 "/home/smith/cc_progs/a.out": can't open to read symbols:
16797 Invalid bfd target.
16798 (@value{GDBP}) show g
16799 The current BFD target is "=4".
16804 The program variable @code{g} did not change, and you silently set the
16805 @code{gnutarget} to an invalid value. In order to set the variable
16809 (@value{GDBP}) set var g=4
16812 @value{GDBN} allows more implicit conversions in assignments than C; you can
16813 freely store an integer value into a pointer variable or vice versa,
16814 and you can convert any structure to any other structure that is the
16815 same length or shorter.
16816 @comment FIXME: how do structs align/pad in these conversions?
16817 @comment /doc@cygnus.com 18dec1990
16819 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16820 construct to generate a value of specified type at a specified address
16821 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16822 to memory location @code{0x83040} as an integer (which implies a certain size
16823 and representation in memory), and
16826 set @{int@}0x83040 = 4
16830 stores the value 4 into that memory location.
16833 @section Continuing at a Different Address
16835 Ordinarily, when you continue your program, you do so at the place where
16836 it stopped, with the @code{continue} command. You can instead continue at
16837 an address of your own choosing, with the following commands:
16841 @kindex j @r{(@code{jump})}
16842 @item jump @var{linespec}
16843 @itemx j @var{linespec}
16844 @itemx jump @var{location}
16845 @itemx j @var{location}
16846 Resume execution at line @var{linespec} or at address given by
16847 @var{location}. Execution stops again immediately if there is a
16848 breakpoint there. @xref{Specify Location}, for a description of the
16849 different forms of @var{linespec} and @var{location}. It is common
16850 practice to use the @code{tbreak} command in conjunction with
16851 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16853 The @code{jump} command does not change the current stack frame, or
16854 the stack pointer, or the contents of any memory location or any
16855 register other than the program counter. If line @var{linespec} is in
16856 a different function from the one currently executing, the results may
16857 be bizarre if the two functions expect different patterns of arguments or
16858 of local variables. For this reason, the @code{jump} command requests
16859 confirmation if the specified line is not in the function currently
16860 executing. However, even bizarre results are predictable if you are
16861 well acquainted with the machine-language code of your program.
16864 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16865 On many systems, you can get much the same effect as the @code{jump}
16866 command by storing a new value into the register @code{$pc}. The
16867 difference is that this does not start your program running; it only
16868 changes the address of where it @emph{will} run when you continue. For
16876 makes the next @code{continue} command or stepping command execute at
16877 address @code{0x485}, rather than at the address where your program stopped.
16878 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16880 The most common occasion to use the @code{jump} command is to back
16881 up---perhaps with more breakpoints set---over a portion of a program
16882 that has already executed, in order to examine its execution in more
16887 @section Giving your Program a Signal
16888 @cindex deliver a signal to a program
16892 @item signal @var{signal}
16893 Resume execution where your program is stopped, but immediately give it the
16894 signal @var{signal}. The @var{signal} can be the name or the number of a
16895 signal. For example, on many systems @code{signal 2} and @code{signal
16896 SIGINT} are both ways of sending an interrupt signal.
16898 Alternatively, if @var{signal} is zero, continue execution without
16899 giving a signal. This is useful when your program stopped on account of
16900 a signal and would ordinarily see the signal when resumed with the
16901 @code{continue} command; @samp{signal 0} causes it to resume without a
16904 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
16905 delivered to the currently selected thread, not the thread that last
16906 reported a stop. This includes the situation where a thread was
16907 stopped due to a signal. So if you want to continue execution
16908 suppressing the signal that stopped a thread, you should select that
16909 same thread before issuing the @samp{signal 0} command. If you issue
16910 the @samp{signal 0} command with another thread as the selected one,
16911 @value{GDBN} detects that and asks for confirmation.
16913 Invoking the @code{signal} command is not the same as invoking the
16914 @code{kill} utility from the shell. Sending a signal with @code{kill}
16915 causes @value{GDBN} to decide what to do with the signal depending on
16916 the signal handling tables (@pxref{Signals}). The @code{signal} command
16917 passes the signal directly to your program.
16919 @code{signal} does not repeat when you press @key{RET} a second time
16920 after executing the command.
16922 @kindex queue-signal
16923 @item queue-signal @var{signal}
16924 Queue @var{signal} to be delivered immediately to the current thread
16925 when execution of the thread resumes. The @var{signal} can be the name or
16926 the number of a signal. For example, on many systems @code{signal 2} and
16927 @code{signal SIGINT} are both ways of sending an interrupt signal.
16928 The handling of the signal must be set to pass the signal to the program,
16929 otherwise @value{GDBN} will report an error.
16930 You can control the handling of signals from @value{GDBN} with the
16931 @code{handle} command (@pxref{Signals}).
16933 Alternatively, if @var{signal} is zero, any currently queued signal
16934 for the current thread is discarded and when execution resumes no signal
16935 will be delivered. This is useful when your program stopped on account
16936 of a signal and would ordinarily see the signal when resumed with the
16937 @code{continue} command.
16939 This command differs from the @code{signal} command in that the signal
16940 is just queued, execution is not resumed. And @code{queue-signal} cannot
16941 be used to pass a signal whose handling state has been set to @code{nopass}
16946 @xref{stepping into signal handlers}, for information on how stepping
16947 commands behave when the thread has a signal queued.
16950 @section Returning from a Function
16953 @cindex returning from a function
16956 @itemx return @var{expression}
16957 You can cancel execution of a function call with the @code{return}
16958 command. If you give an
16959 @var{expression} argument, its value is used as the function's return
16963 When you use @code{return}, @value{GDBN} discards the selected stack frame
16964 (and all frames within it). You can think of this as making the
16965 discarded frame return prematurely. If you wish to specify a value to
16966 be returned, give that value as the argument to @code{return}.
16968 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16969 Frame}), and any other frames inside of it, leaving its caller as the
16970 innermost remaining frame. That frame becomes selected. The
16971 specified value is stored in the registers used for returning values
16974 The @code{return} command does not resume execution; it leaves the
16975 program stopped in the state that would exist if the function had just
16976 returned. In contrast, the @code{finish} command (@pxref{Continuing
16977 and Stepping, ,Continuing and Stepping}) resumes execution until the
16978 selected stack frame returns naturally.
16980 @value{GDBN} needs to know how the @var{expression} argument should be set for
16981 the inferior. The concrete registers assignment depends on the OS ABI and the
16982 type being returned by the selected stack frame. For example it is common for
16983 OS ABI to return floating point values in FPU registers while integer values in
16984 CPU registers. Still some ABIs return even floating point values in CPU
16985 registers. Larger integer widths (such as @code{long long int}) also have
16986 specific placement rules. @value{GDBN} already knows the OS ABI from its
16987 current target so it needs to find out also the type being returned to make the
16988 assignment into the right register(s).
16990 Normally, the selected stack frame has debug info. @value{GDBN} will always
16991 use the debug info instead of the implicit type of @var{expression} when the
16992 debug info is available. For example, if you type @kbd{return -1}, and the
16993 function in the current stack frame is declared to return a @code{long long
16994 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16995 into a @code{long long int}:
16998 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17000 (@value{GDBP}) return -1
17001 Make func return now? (y or n) y
17002 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17003 43 printf ("result=%lld\n", func ());
17007 However, if the selected stack frame does not have a debug info, e.g., if the
17008 function was compiled without debug info, @value{GDBN} has to find out the type
17009 to return from user. Specifying a different type by mistake may set the value
17010 in different inferior registers than the caller code expects. For example,
17011 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17012 of a @code{long long int} result for a debug info less function (on 32-bit
17013 architectures). Therefore the user is required to specify the return type by
17014 an appropriate cast explicitly:
17017 Breakpoint 2, 0x0040050b in func ()
17018 (@value{GDBP}) return -1
17019 Return value type not available for selected stack frame.
17020 Please use an explicit cast of the value to return.
17021 (@value{GDBP}) return (long long int) -1
17022 Make selected stack frame return now? (y or n) y
17023 #0 0x00400526 in main ()
17028 @section Calling Program Functions
17031 @cindex calling functions
17032 @cindex inferior functions, calling
17033 @item print @var{expr}
17034 Evaluate the expression @var{expr} and display the resulting value.
17035 The expression may include calls to functions in the program being
17039 @item call @var{expr}
17040 Evaluate the expression @var{expr} without displaying @code{void}
17043 You can use this variant of the @code{print} command if you want to
17044 execute a function from your program that does not return anything
17045 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17046 with @code{void} returned values that @value{GDBN} will otherwise
17047 print. If the result is not void, it is printed and saved in the
17051 It is possible for the function you call via the @code{print} or
17052 @code{call} command to generate a signal (e.g., if there's a bug in
17053 the function, or if you passed it incorrect arguments). What happens
17054 in that case is controlled by the @code{set unwindonsignal} command.
17056 Similarly, with a C@t{++} program it is possible for the function you
17057 call via the @code{print} or @code{call} command to generate an
17058 exception that is not handled due to the constraints of the dummy
17059 frame. In this case, any exception that is raised in the frame, but has
17060 an out-of-frame exception handler will not be found. GDB builds a
17061 dummy-frame for the inferior function call, and the unwinder cannot
17062 seek for exception handlers outside of this dummy-frame. What happens
17063 in that case is controlled by the
17064 @code{set unwind-on-terminating-exception} command.
17067 @item set unwindonsignal
17068 @kindex set unwindonsignal
17069 @cindex unwind stack in called functions
17070 @cindex call dummy stack unwinding
17071 Set unwinding of the stack if a signal is received while in a function
17072 that @value{GDBN} called in the program being debugged. If set to on,
17073 @value{GDBN} unwinds the stack it created for the call and restores
17074 the context to what it was before the call. If set to off (the
17075 default), @value{GDBN} stops in the frame where the signal was
17078 @item show unwindonsignal
17079 @kindex show unwindonsignal
17080 Show the current setting of stack unwinding in the functions called by
17083 @item set unwind-on-terminating-exception
17084 @kindex set unwind-on-terminating-exception
17085 @cindex unwind stack in called functions with unhandled exceptions
17086 @cindex call dummy stack unwinding on unhandled exception.
17087 Set unwinding of the stack if a C@t{++} exception is raised, but left
17088 unhandled while in a function that @value{GDBN} called in the program being
17089 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17090 it created for the call and restores the context to what it was before
17091 the call. If set to off, @value{GDBN} the exception is delivered to
17092 the default C@t{++} exception handler and the inferior terminated.
17094 @item show unwind-on-terminating-exception
17095 @kindex show unwind-on-terminating-exception
17096 Show the current setting of stack unwinding in the functions called by
17101 @cindex weak alias functions
17102 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17103 for another function. In such case, @value{GDBN} might not pick up
17104 the type information, including the types of the function arguments,
17105 which causes @value{GDBN} to call the inferior function incorrectly.
17106 As a result, the called function will function erroneously and may
17107 even crash. A solution to that is to use the name of the aliased
17111 @section Patching Programs
17113 @cindex patching binaries
17114 @cindex writing into executables
17115 @cindex writing into corefiles
17117 By default, @value{GDBN} opens the file containing your program's
17118 executable code (or the corefile) read-only. This prevents accidental
17119 alterations to machine code; but it also prevents you from intentionally
17120 patching your program's binary.
17122 If you'd like to be able to patch the binary, you can specify that
17123 explicitly with the @code{set write} command. For example, you might
17124 want to turn on internal debugging flags, or even to make emergency
17130 @itemx set write off
17131 If you specify @samp{set write on}, @value{GDBN} opens executable and
17132 core files for both reading and writing; if you specify @kbd{set write
17133 off} (the default), @value{GDBN} opens them read-only.
17135 If you have already loaded a file, you must load it again (using the
17136 @code{exec-file} or @code{core-file} command) after changing @code{set
17137 write}, for your new setting to take effect.
17141 Display whether executable files and core files are opened for writing
17142 as well as reading.
17145 @node Compiling and Injecting Code
17146 @section Compiling and injecting code in @value{GDBN}
17147 @cindex injecting code
17148 @cindex writing into executables
17149 @cindex compiling code
17151 @value{GDBN} supports on-demand compilation and code injection into
17152 programs running under @value{GDBN}. GCC 5.0 or higher built with
17153 @file{libcc1.so} must be installed for this functionality to be enabled.
17154 This functionality is implemented with the following commands.
17157 @kindex compile code
17158 @item compile code @var{source-code}
17159 @itemx compile code -raw @var{--} @var{source-code}
17160 Compile @var{source-code} with the compiler language found as the current
17161 language in @value{GDBN} (@pxref{Languages}). If compilation and
17162 injection is not supported with the current language specified in
17163 @value{GDBN}, or the compiler does not support this feature, an error
17164 message will be printed. If @var{source-code} compiles and links
17165 successfully, @value{GDBN} will load the object-code emitted,
17166 and execute it within the context of the currently selected inferior.
17167 It is important to note that the compiled code is executed immediately.
17168 After execution, the compiled code is removed from @value{GDBN} and any
17169 new types or variables you have defined will be deleted.
17171 The command allows you to specify @var{source-code} in two ways.
17172 The simplest method is to provide a single line of code to the command.
17176 compile code printf ("hello world\n");
17179 If you specify options on the command line as well as source code, they
17180 may conflict. The @samp{--} delimiter can be used to separate options
17181 from actual source code. E.g.:
17184 compile code -r -- printf ("hello world\n");
17187 Alternatively you can enter source code as multiple lines of text. To
17188 enter this mode, invoke the @samp{compile code} command without any text
17189 following the command. This will start the multiple-line editor and
17190 allow you to type as many lines of source code as required. When you
17191 have completed typing, enter @samp{end} on its own line to exit the
17196 >printf ("hello\n");
17197 >printf ("world\n");
17201 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17202 provided @var{source-code} in a callable scope. In this case, you must
17203 specify the entry point of the code by defining a function named
17204 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17205 inferior. Using @samp{-raw} option may be needed for example when
17206 @var{source-code} requires @samp{#include} lines which may conflict with
17207 inferior symbols otherwise.
17209 @kindex compile file
17210 @item compile file @var{filename}
17211 @itemx compile file -raw @var{filename}
17212 Like @code{compile code}, but take the source code from @var{filename}.
17215 compile file /home/user/example.c
17220 The process of compiling and injecting the code can be inspected using:
17223 @anchor{set debug compile}
17224 @item set debug compile
17225 @cindex compile command debugging info
17226 Turns on or off display of @value{GDBN} process of compiling and
17227 injecting the code. The default is off.
17229 @item show debug compile
17230 Displays the current state of displaying @value{GDBN} process of
17231 compiling and injecting the code.
17234 @subsection Compilation options for the @code{compile} command
17236 @value{GDBN} needs to specify the right compilation options for the code
17237 to be injected, in part to make its ABI compatible with the inferior
17238 and in part to make the injected code compatible with @value{GDBN}'s
17242 The options used, in increasing precedence:
17245 @item target architecture and OS options (@code{gdbarch})
17246 These options depend on target processor type and target operating
17247 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17248 (@code{-m64}) compilation option.
17250 @item compilation options recorded in the target
17251 @value{NGCC} (since version 4.7) stores the options used for compilation
17252 into @code{DW_AT_producer} part of DWARF debugging information according
17253 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17254 explicitly specify @code{-g} during inferior compilation otherwise
17255 @value{NGCC} produces no DWARF. This feature is only relevant for
17256 platforms where @code{-g} produces DWARF by default, otherwise one may
17257 try to enforce DWARF by using @code{-gdwarf-4}.
17259 @item compilation options set by @code{set compile-args}
17263 You can override compilation options using the following command:
17266 @item set compile-args
17267 @cindex compile command options override
17268 Set compilation options used for compiling and injecting code with the
17269 @code{compile} commands. These options override any conflicting ones
17270 from the target architecture and/or options stored during inferior
17273 @item show compile-args
17274 Displays the current state of compilation options override.
17275 This does not show all the options actually used during compilation,
17276 use @ref{set debug compile} for that.
17279 @subsection Caveats when using the @code{compile} command
17281 There are a few caveats to keep in mind when using the @code{compile}
17282 command. As the caveats are different per language, the table below
17283 highlights specific issues on a per language basis.
17286 @item C code examples and caveats
17287 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17288 attempt to compile the source code with a @samp{C} compiler. The source
17289 code provided to the @code{compile} command will have much the same
17290 access to variables and types as it normally would if it were part of
17291 the program currently being debugged in @value{GDBN}.
17293 Below is a sample program that forms the basis of the examples that
17294 follow. This program has been compiled and loaded into @value{GDBN},
17295 much like any other normal debugging session.
17298 void function1 (void)
17301 printf ("function 1\n");
17304 void function2 (void)
17319 For the purposes of the examples in this section, the program above has
17320 been compiled, loaded into @value{GDBN}, stopped at the function
17321 @code{main}, and @value{GDBN} is awaiting input from the user.
17323 To access variables and types for any program in @value{GDBN}, the
17324 program must be compiled and packaged with debug information. The
17325 @code{compile} command is not an exception to this rule. Without debug
17326 information, you can still use the @code{compile} command, but you will
17327 be very limited in what variables and types you can access.
17329 So with that in mind, the example above has been compiled with debug
17330 information enabled. The @code{compile} command will have access to
17331 all variables and types (except those that may have been optimized
17332 out). Currently, as @value{GDBN} has stopped the program in the
17333 @code{main} function, the @code{compile} command would have access to
17334 the variable @code{k}. You could invoke the @code{compile} command
17335 and type some source code to set the value of @code{k}. You can also
17336 read it, or do anything with that variable you would normally do in
17337 @code{C}. Be aware that changes to inferior variables in the
17338 @code{compile} command are persistent. In the following example:
17341 compile code k = 3;
17345 the variable @code{k} is now 3. It will retain that value until
17346 something else in the example program changes it, or another
17347 @code{compile} command changes it.
17349 Normal scope and access rules apply to source code compiled and
17350 injected by the @code{compile} command. In the example, the variables
17351 @code{j} and @code{k} are not accessible yet, because the program is
17352 currently stopped in the @code{main} function, where these variables
17353 are not in scope. Therefore, the following command
17356 compile code j = 3;
17360 will result in a compilation error message.
17362 Once the program is continued, execution will bring these variables in
17363 scope, and they will become accessible; then the code you specify via
17364 the @code{compile} command will be able to access them.
17366 You can create variables and types with the @code{compile} command as
17367 part of your source code. Variables and types that are created as part
17368 of the @code{compile} command are not visible to the rest of the program for
17369 the duration of its run. This example is valid:
17372 compile code int ff = 5; printf ("ff is %d\n", ff);
17375 However, if you were to type the following into @value{GDBN} after that
17376 command has completed:
17379 compile code printf ("ff is %d\n'', ff);
17383 a compiler error would be raised as the variable @code{ff} no longer
17384 exists. Object code generated and injected by the @code{compile}
17385 command is removed when its execution ends. Caution is advised
17386 when assigning to program variables values of variables created by the
17387 code submitted to the @code{compile} command. This example is valid:
17390 compile code int ff = 5; k = ff;
17393 The value of the variable @code{ff} is assigned to @code{k}. The variable
17394 @code{k} does not require the existence of @code{ff} to maintain the value
17395 it has been assigned. However, pointers require particular care in
17396 assignment. If the source code compiled with the @code{compile} command
17397 changed the address of a pointer in the example program, perhaps to a
17398 variable created in the @code{compile} command, that pointer would point
17399 to an invalid location when the command exits. The following example
17400 would likely cause issues with your debugged program:
17403 compile code int ff = 5; p = &ff;
17406 In this example, @code{p} would point to @code{ff} when the
17407 @code{compile} command is executing the source code provided to it.
17408 However, as variables in the (example) program persist with their
17409 assigned values, the variable @code{p} would point to an invalid
17410 location when the command exists. A general rule should be followed
17411 in that you should either assign @code{NULL} to any assigned pointers,
17412 or restore a valid location to the pointer before the command exits.
17414 Similar caution must be exercised with any structs, unions, and typedefs
17415 defined in @code{compile} command. Types defined in the @code{compile}
17416 command will no longer be available in the next @code{compile} command.
17417 Therefore, if you cast a variable to a type defined in the
17418 @code{compile} command, care must be taken to ensure that any future
17419 need to resolve the type can be achieved.
17422 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17423 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17424 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17425 Compilation failed.
17426 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17430 Variables that have been optimized away by the compiler are not
17431 accessible to the code submitted to the @code{compile} command.
17432 Access to those variables will generate a compiler error which @value{GDBN}
17433 will print to the console.
17436 @subsection Compiler search for the @code{compile} command
17438 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
17439 may not be obvious for remote targets of different architecture than where
17440 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
17441 shell that executed @value{GDBN}, not the one set by @value{GDBN}
17442 command @code{set environment}). @xref{Environment}. @code{PATH} on
17443 @value{GDBN} host is searched for @value{NGCC} binary matching the
17444 target architecture and operating system.
17446 Specifically @code{PATH} is searched for binaries matching regular expression
17447 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
17448 debugged. @var{arch} is processor name --- multiarch is supported, so for
17449 example both @code{i386} and @code{x86_64} targets look for pattern
17450 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
17451 for pattern @code{s390x?}. @var{os} is currently supported only for
17452 pattern @code{linux(-gnu)?}.
17455 @chapter @value{GDBN} Files
17457 @value{GDBN} needs to know the file name of the program to be debugged,
17458 both in order to read its symbol table and in order to start your
17459 program. To debug a core dump of a previous run, you must also tell
17460 @value{GDBN} the name of the core dump file.
17463 * Files:: Commands to specify files
17464 * Separate Debug Files:: Debugging information in separate files
17465 * MiniDebugInfo:: Debugging information in a special section
17466 * Index Files:: Index files speed up GDB
17467 * Symbol Errors:: Errors reading symbol files
17468 * Data Files:: GDB data files
17472 @section Commands to Specify Files
17474 @cindex symbol table
17475 @cindex core dump file
17477 You may want to specify executable and core dump file names. The usual
17478 way to do this is at start-up time, using the arguments to
17479 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17480 Out of @value{GDBN}}).
17482 Occasionally it is necessary to change to a different file during a
17483 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17484 specify a file you want to use. Or you are debugging a remote target
17485 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17486 Program}). In these situations the @value{GDBN} commands to specify
17487 new files are useful.
17490 @cindex executable file
17492 @item file @var{filename}
17493 Use @var{filename} as the program to be debugged. It is read for its
17494 symbols and for the contents of pure memory. It is also the program
17495 executed when you use the @code{run} command. If you do not specify a
17496 directory and the file is not found in the @value{GDBN} working directory,
17497 @value{GDBN} uses the environment variable @code{PATH} as a list of
17498 directories to search, just as the shell does when looking for a program
17499 to run. You can change the value of this variable, for both @value{GDBN}
17500 and your program, using the @code{path} command.
17502 @cindex unlinked object files
17503 @cindex patching object files
17504 You can load unlinked object @file{.o} files into @value{GDBN} using
17505 the @code{file} command. You will not be able to ``run'' an object
17506 file, but you can disassemble functions and inspect variables. Also,
17507 if the underlying BFD functionality supports it, you could use
17508 @kbd{gdb -write} to patch object files using this technique. Note
17509 that @value{GDBN} can neither interpret nor modify relocations in this
17510 case, so branches and some initialized variables will appear to go to
17511 the wrong place. But this feature is still handy from time to time.
17514 @code{file} with no argument makes @value{GDBN} discard any information it
17515 has on both executable file and the symbol table.
17518 @item exec-file @r{[} @var{filename} @r{]}
17519 Specify that the program to be run (but not the symbol table) is found
17520 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17521 if necessary to locate your program. Omitting @var{filename} means to
17522 discard information on the executable file.
17524 @kindex symbol-file
17525 @item symbol-file @r{[} @var{filename} @r{]}
17526 Read symbol table information from file @var{filename}. @code{PATH} is
17527 searched when necessary. Use the @code{file} command to get both symbol
17528 table and program to run from the same file.
17530 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17531 program's symbol table.
17533 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17534 some breakpoints and auto-display expressions. This is because they may
17535 contain pointers to the internal data recording symbols and data types,
17536 which are part of the old symbol table data being discarded inside
17539 @code{symbol-file} does not repeat if you press @key{RET} again after
17542 When @value{GDBN} is configured for a particular environment, it
17543 understands debugging information in whatever format is the standard
17544 generated for that environment; you may use either a @sc{gnu} compiler, or
17545 other compilers that adhere to the local conventions.
17546 Best results are usually obtained from @sc{gnu} compilers; for example,
17547 using @code{@value{NGCC}} you can generate debugging information for
17550 For most kinds of object files, with the exception of old SVR3 systems
17551 using COFF, the @code{symbol-file} command does not normally read the
17552 symbol table in full right away. Instead, it scans the symbol table
17553 quickly to find which source files and which symbols are present. The
17554 details are read later, one source file at a time, as they are needed.
17556 The purpose of this two-stage reading strategy is to make @value{GDBN}
17557 start up faster. For the most part, it is invisible except for
17558 occasional pauses while the symbol table details for a particular source
17559 file are being read. (The @code{set verbose} command can turn these
17560 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17561 Warnings and Messages}.)
17563 We have not implemented the two-stage strategy for COFF yet. When the
17564 symbol table is stored in COFF format, @code{symbol-file} reads the
17565 symbol table data in full right away. Note that ``stabs-in-COFF''
17566 still does the two-stage strategy, since the debug info is actually
17570 @cindex reading symbols immediately
17571 @cindex symbols, reading immediately
17572 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17573 @itemx file @r{[} -readnow @r{]} @var{filename}
17574 You can override the @value{GDBN} two-stage strategy for reading symbol
17575 tables by using the @samp{-readnow} option with any of the commands that
17576 load symbol table information, if you want to be sure @value{GDBN} has the
17577 entire symbol table available.
17579 @c FIXME: for now no mention of directories, since this seems to be in
17580 @c flux. 13mar1992 status is that in theory GDB would look either in
17581 @c current dir or in same dir as myprog; but issues like competing
17582 @c GDB's, or clutter in system dirs, mean that in practice right now
17583 @c only current dir is used. FFish says maybe a special GDB hierarchy
17584 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17588 @item core-file @r{[}@var{filename}@r{]}
17590 Specify the whereabouts of a core dump file to be used as the ``contents
17591 of memory''. Traditionally, core files contain only some parts of the
17592 address space of the process that generated them; @value{GDBN} can access the
17593 executable file itself for other parts.
17595 @code{core-file} with no argument specifies that no core file is
17598 Note that the core file is ignored when your program is actually running
17599 under @value{GDBN}. So, if you have been running your program and you
17600 wish to debug a core file instead, you must kill the subprocess in which
17601 the program is running. To do this, use the @code{kill} command
17602 (@pxref{Kill Process, ,Killing the Child Process}).
17604 @kindex add-symbol-file
17605 @cindex dynamic linking
17606 @item add-symbol-file @var{filename} @var{address}
17607 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17608 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17609 The @code{add-symbol-file} command reads additional symbol table
17610 information from the file @var{filename}. You would use this command
17611 when @var{filename} has been dynamically loaded (by some other means)
17612 into the program that is running. The @var{address} should give the memory
17613 address at which the file has been loaded; @value{GDBN} cannot figure
17614 this out for itself. You can additionally specify an arbitrary number
17615 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17616 section name and base address for that section. You can specify any
17617 @var{address} as an expression.
17619 The symbol table of the file @var{filename} is added to the symbol table
17620 originally read with the @code{symbol-file} command. You can use the
17621 @code{add-symbol-file} command any number of times; the new symbol data
17622 thus read is kept in addition to the old.
17624 Changes can be reverted using the command @code{remove-symbol-file}.
17626 @cindex relocatable object files, reading symbols from
17627 @cindex object files, relocatable, reading symbols from
17628 @cindex reading symbols from relocatable object files
17629 @cindex symbols, reading from relocatable object files
17630 @cindex @file{.o} files, reading symbols from
17631 Although @var{filename} is typically a shared library file, an
17632 executable file, or some other object file which has been fully
17633 relocated for loading into a process, you can also load symbolic
17634 information from relocatable @file{.o} files, as long as:
17638 the file's symbolic information refers only to linker symbols defined in
17639 that file, not to symbols defined by other object files,
17641 every section the file's symbolic information refers to has actually
17642 been loaded into the inferior, as it appears in the file, and
17644 you can determine the address at which every section was loaded, and
17645 provide these to the @code{add-symbol-file} command.
17649 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17650 relocatable files into an already running program; such systems
17651 typically make the requirements above easy to meet. However, it's
17652 important to recognize that many native systems use complex link
17653 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17654 assembly, for example) that make the requirements difficult to meet. In
17655 general, one cannot assume that using @code{add-symbol-file} to read a
17656 relocatable object file's symbolic information will have the same effect
17657 as linking the relocatable object file into the program in the normal
17660 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17662 @kindex remove-symbol-file
17663 @item remove-symbol-file @var{filename}
17664 @item remove-symbol-file -a @var{address}
17665 Remove a symbol file added via the @code{add-symbol-file} command. The
17666 file to remove can be identified by its @var{filename} or by an @var{address}
17667 that lies within the boundaries of this symbol file in memory. Example:
17670 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
17671 add symbol table from file "/home/user/gdb/mylib.so" at
17672 .text_addr = 0x7ffff7ff9480
17674 Reading symbols from /home/user/gdb/mylib.so...done.
17675 (gdb) remove-symbol-file -a 0x7ffff7ff9480
17676 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
17681 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
17683 @kindex add-symbol-file-from-memory
17684 @cindex @code{syscall DSO}
17685 @cindex load symbols from memory
17686 @item add-symbol-file-from-memory @var{address}
17687 Load symbols from the given @var{address} in a dynamically loaded
17688 object file whose image is mapped directly into the inferior's memory.
17689 For example, the Linux kernel maps a @code{syscall DSO} into each
17690 process's address space; this DSO provides kernel-specific code for
17691 some system calls. The argument can be any expression whose
17692 evaluation yields the address of the file's shared object file header.
17693 For this command to work, you must have used @code{symbol-file} or
17694 @code{exec-file} commands in advance.
17697 @item section @var{section} @var{addr}
17698 The @code{section} command changes the base address of the named
17699 @var{section} of the exec file to @var{addr}. This can be used if the
17700 exec file does not contain section addresses, (such as in the
17701 @code{a.out} format), or when the addresses specified in the file
17702 itself are wrong. Each section must be changed separately. The
17703 @code{info files} command, described below, lists all the sections and
17707 @kindex info target
17710 @code{info files} and @code{info target} are synonymous; both print the
17711 current target (@pxref{Targets, ,Specifying a Debugging Target}),
17712 including the names of the executable and core dump files currently in
17713 use by @value{GDBN}, and the files from which symbols were loaded. The
17714 command @code{help target} lists all possible targets rather than
17717 @kindex maint info sections
17718 @item maint info sections
17719 Another command that can give you extra information about program sections
17720 is @code{maint info sections}. In addition to the section information
17721 displayed by @code{info files}, this command displays the flags and file
17722 offset of each section in the executable and core dump files. In addition,
17723 @code{maint info sections} provides the following command options (which
17724 may be arbitrarily combined):
17728 Display sections for all loaded object files, including shared libraries.
17729 @item @var{sections}
17730 Display info only for named @var{sections}.
17731 @item @var{section-flags}
17732 Display info only for sections for which @var{section-flags} are true.
17733 The section flags that @value{GDBN} currently knows about are:
17736 Section will have space allocated in the process when loaded.
17737 Set for all sections except those containing debug information.
17739 Section will be loaded from the file into the child process memory.
17740 Set for pre-initialized code and data, clear for @code{.bss} sections.
17742 Section needs to be relocated before loading.
17744 Section cannot be modified by the child process.
17746 Section contains executable code only.
17748 Section contains data only (no executable code).
17750 Section will reside in ROM.
17752 Section contains data for constructor/destructor lists.
17754 Section is not empty.
17756 An instruction to the linker to not output the section.
17757 @item COFF_SHARED_LIBRARY
17758 A notification to the linker that the section contains
17759 COFF shared library information.
17761 Section contains common symbols.
17764 @kindex set trust-readonly-sections
17765 @cindex read-only sections
17766 @item set trust-readonly-sections on
17767 Tell @value{GDBN} that readonly sections in your object file
17768 really are read-only (i.e.@: that their contents will not change).
17769 In that case, @value{GDBN} can fetch values from these sections
17770 out of the object file, rather than from the target program.
17771 For some targets (notably embedded ones), this can be a significant
17772 enhancement to debugging performance.
17774 The default is off.
17776 @item set trust-readonly-sections off
17777 Tell @value{GDBN} not to trust readonly sections. This means that
17778 the contents of the section might change while the program is running,
17779 and must therefore be fetched from the target when needed.
17781 @item show trust-readonly-sections
17782 Show the current setting of trusting readonly sections.
17785 All file-specifying commands allow both absolute and relative file names
17786 as arguments. @value{GDBN} always converts the file name to an absolute file
17787 name and remembers it that way.
17789 @cindex shared libraries
17790 @anchor{Shared Libraries}
17791 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
17792 and IBM RS/6000 AIX shared libraries.
17794 On MS-Windows @value{GDBN} must be linked with the Expat library to support
17795 shared libraries. @xref{Expat}.
17797 @value{GDBN} automatically loads symbol definitions from shared libraries
17798 when you use the @code{run} command, or when you examine a core file.
17799 (Before you issue the @code{run} command, @value{GDBN} does not understand
17800 references to a function in a shared library, however---unless you are
17801 debugging a core file).
17803 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17804 automatically loads the symbols at the time of the @code{shl_load} call.
17806 @c FIXME: some @value{GDBN} release may permit some refs to undef
17807 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17808 @c FIXME...lib; check this from time to time when updating manual
17810 There are times, however, when you may wish to not automatically load
17811 symbol definitions from shared libraries, such as when they are
17812 particularly large or there are many of them.
17814 To control the automatic loading of shared library symbols, use the
17818 @kindex set auto-solib-add
17819 @item set auto-solib-add @var{mode}
17820 If @var{mode} is @code{on}, symbols from all shared object libraries
17821 will be loaded automatically when the inferior begins execution, you
17822 attach to an independently started inferior, or when the dynamic linker
17823 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17824 is @code{off}, symbols must be loaded manually, using the
17825 @code{sharedlibrary} command. The default value is @code{on}.
17827 @cindex memory used for symbol tables
17828 If your program uses lots of shared libraries with debug info that
17829 takes large amounts of memory, you can decrease the @value{GDBN}
17830 memory footprint by preventing it from automatically loading the
17831 symbols from shared libraries. To that end, type @kbd{set
17832 auto-solib-add off} before running the inferior, then load each
17833 library whose debug symbols you do need with @kbd{sharedlibrary
17834 @var{regexp}}, where @var{regexp} is a regular expression that matches
17835 the libraries whose symbols you want to be loaded.
17837 @kindex show auto-solib-add
17838 @item show auto-solib-add
17839 Display the current autoloading mode.
17842 @cindex load shared library
17843 To explicitly load shared library symbols, use the @code{sharedlibrary}
17847 @kindex info sharedlibrary
17849 @item info share @var{regex}
17850 @itemx info sharedlibrary @var{regex}
17851 Print the names of the shared libraries which are currently loaded
17852 that match @var{regex}. If @var{regex} is omitted then print
17853 all shared libraries that are loaded.
17855 @kindex sharedlibrary
17857 @item sharedlibrary @var{regex}
17858 @itemx share @var{regex}
17859 Load shared object library symbols for files matching a
17860 Unix regular expression.
17861 As with files loaded automatically, it only loads shared libraries
17862 required by your program for a core file or after typing @code{run}. If
17863 @var{regex} is omitted all shared libraries required by your program are
17866 @item nosharedlibrary
17867 @kindex nosharedlibrary
17868 @cindex unload symbols from shared libraries
17869 Unload all shared object library symbols. This discards all symbols
17870 that have been loaded from all shared libraries. Symbols from shared
17871 libraries that were loaded by explicit user requests are not
17875 Sometimes you may wish that @value{GDBN} stops and gives you control
17876 when any of shared library events happen. The best way to do this is
17877 to use @code{catch load} and @code{catch unload} (@pxref{Set
17880 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17881 command for this. This command exists for historical reasons. It is
17882 less useful than setting a catchpoint, because it does not allow for
17883 conditions or commands as a catchpoint does.
17886 @item set stop-on-solib-events
17887 @kindex set stop-on-solib-events
17888 This command controls whether @value{GDBN} should give you control
17889 when the dynamic linker notifies it about some shared library event.
17890 The most common event of interest is loading or unloading of a new
17893 @item show stop-on-solib-events
17894 @kindex show stop-on-solib-events
17895 Show whether @value{GDBN} stops and gives you control when shared
17896 library events happen.
17899 Shared libraries are also supported in many cross or remote debugging
17900 configurations. @value{GDBN} needs to have access to the target's libraries;
17901 this can be accomplished either by providing copies of the libraries
17902 on the host system, or by asking @value{GDBN} to automatically retrieve the
17903 libraries from the target. If copies of the target libraries are
17904 provided, they need to be the same as the target libraries, although the
17905 copies on the target can be stripped as long as the copies on the host are
17908 @cindex where to look for shared libraries
17909 For remote debugging, you need to tell @value{GDBN} where the target
17910 libraries are, so that it can load the correct copies---otherwise, it
17911 may try to load the host's libraries. @value{GDBN} has two variables
17912 to specify the search directories for target libraries.
17915 @cindex prefix for executable and shared library file names
17916 @cindex system root, alternate
17917 @kindex set solib-absolute-prefix
17918 @kindex set sysroot
17919 @item set sysroot @var{path}
17920 Use @var{path} as the system root for the program being debugged. Any
17921 absolute shared library paths will be prefixed with @var{path}; many
17922 runtime loaders store the absolute paths to the shared library in the
17923 target program's memory. When starting processes remotely, and when
17924 attaching to already-running processes (local or remote), their
17925 executable filenames will be prefixed with @var{path} if reported to
17926 @value{GDBN} as absolute by the operating system. If you use
17927 @code{set sysroot} to find executables and shared libraries, they need
17928 to be laid out in the same way that they are on the target, with
17929 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
17932 If @var{path} starts with the sequence @file{target:} and the target
17933 system is remote then @value{GDBN} will retrieve the target binaries
17934 from the remote system. This is only supported when using a remote
17935 target that supports the @code{remote get} command (@pxref{File
17936 Transfer,,Sending files to a remote system}). The part of @var{path}
17937 following the initial @file{target:} (if present) is used as system
17938 root prefix on the remote file system. If @var{path} starts with the
17939 sequence @file{remote:} this is converted to the sequence
17940 @file{target:} by @code{set sysroot}@footnote{Historically the
17941 functionality to retrieve binaries from the remote system was
17942 provided by prefixing @var{path} with @file{remote:}}. If you want
17943 to specify a local system root using a directory that happens to be
17944 named @file{target:} or @file{remote:}, you need to use some
17945 equivalent variant of the name like @file{./target:}.
17947 For targets with an MS-DOS based filesystem, such as MS-Windows and
17948 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17949 absolute file name with @var{path}. But first, on Unix hosts,
17950 @value{GDBN} converts all backslash directory separators into forward
17951 slashes, because the backslash is not a directory separator on Unix:
17954 c:\foo\bar.dll @result{} c:/foo/bar.dll
17957 Then, @value{GDBN} attempts prefixing the target file name with
17958 @var{path}, and looks for the resulting file name in the host file
17962 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17965 If that does not find the binary, @value{GDBN} tries removing
17966 the @samp{:} character from the drive spec, both for convenience, and,
17967 for the case of the host file system not supporting file names with
17971 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17974 This makes it possible to have a system root that mirrors a target
17975 with more than one drive. E.g., you may want to setup your local
17976 copies of the target system shared libraries like so (note @samp{c} vs
17980 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17981 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17982 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17986 and point the system root at @file{/path/to/sysroot}, so that
17987 @value{GDBN} can find the correct copies of both
17988 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17990 If that still does not find the binary, @value{GDBN} tries
17991 removing the whole drive spec from the target file name:
17994 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17997 This last lookup makes it possible to not care about the drive name,
17998 if you don't want or need to.
18000 The @code{set solib-absolute-prefix} command is an alias for @code{set
18003 @cindex default system root
18004 @cindex @samp{--with-sysroot}
18005 You can set the default system root by using the configure-time
18006 @samp{--with-sysroot} option. If the system root is inside
18007 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18008 @samp{--exec-prefix}), then the default system root will be updated
18009 automatically if the installed @value{GDBN} is moved to a new
18012 @kindex show sysroot
18014 Display the current executable and shared library prefix.
18016 @kindex set solib-search-path
18017 @item set solib-search-path @var{path}
18018 If this variable is set, @var{path} is a colon-separated list of
18019 directories to search for shared libraries. @samp{solib-search-path}
18020 is used after @samp{sysroot} fails to locate the library, or if the
18021 path to the library is relative instead of absolute. If you want to
18022 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18023 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18024 finding your host's libraries. @samp{sysroot} is preferred; setting
18025 it to a nonexistent directory may interfere with automatic loading
18026 of shared library symbols.
18028 @kindex show solib-search-path
18029 @item show solib-search-path
18030 Display the current shared library search path.
18032 @cindex DOS file-name semantics of file names.
18033 @kindex set target-file-system-kind (unix|dos-based|auto)
18034 @kindex show target-file-system-kind
18035 @item set target-file-system-kind @var{kind}
18036 Set assumed file system kind for target reported file names.
18038 Shared library file names as reported by the target system may not
18039 make sense as is on the system @value{GDBN} is running on. For
18040 example, when remote debugging a target that has MS-DOS based file
18041 system semantics, from a Unix host, the target may be reporting to
18042 @value{GDBN} a list of loaded shared libraries with file names such as
18043 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18044 drive letters, so the @samp{c:\} prefix is not normally understood as
18045 indicating an absolute file name, and neither is the backslash
18046 normally considered a directory separator character. In that case,
18047 the native file system would interpret this whole absolute file name
18048 as a relative file name with no directory components. This would make
18049 it impossible to point @value{GDBN} at a copy of the remote target's
18050 shared libraries on the host using @code{set sysroot}, and impractical
18051 with @code{set solib-search-path}. Setting
18052 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18053 to interpret such file names similarly to how the target would, and to
18054 map them to file names valid on @value{GDBN}'s native file system
18055 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18056 to one of the supported file system kinds. In that case, @value{GDBN}
18057 tries to determine the appropriate file system variant based on the
18058 current target's operating system (@pxref{ABI, ,Configuring the
18059 Current ABI}). The supported file system settings are:
18063 Instruct @value{GDBN} to assume the target file system is of Unix
18064 kind. Only file names starting the forward slash (@samp{/}) character
18065 are considered absolute, and the directory separator character is also
18069 Instruct @value{GDBN} to assume the target file system is DOS based.
18070 File names starting with either a forward slash, or a drive letter
18071 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18072 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18073 considered directory separators.
18076 Instruct @value{GDBN} to use the file system kind associated with the
18077 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18078 This is the default.
18082 @cindex file name canonicalization
18083 @cindex base name differences
18084 When processing file names provided by the user, @value{GDBN}
18085 frequently needs to compare them to the file names recorded in the
18086 program's debug info. Normally, @value{GDBN} compares just the
18087 @dfn{base names} of the files as strings, which is reasonably fast
18088 even for very large programs. (The base name of a file is the last
18089 portion of its name, after stripping all the leading directories.)
18090 This shortcut in comparison is based upon the assumption that files
18091 cannot have more than one base name. This is usually true, but
18092 references to files that use symlinks or similar filesystem
18093 facilities violate that assumption. If your program records files
18094 using such facilities, or if you provide file names to @value{GDBN}
18095 using symlinks etc., you can set @code{basenames-may-differ} to
18096 @code{true} to instruct @value{GDBN} to completely canonicalize each
18097 pair of file names it needs to compare. This will make file-name
18098 comparisons accurate, but at a price of a significant slowdown.
18101 @item set basenames-may-differ
18102 @kindex set basenames-may-differ
18103 Set whether a source file may have multiple base names.
18105 @item show basenames-may-differ
18106 @kindex show basenames-may-differ
18107 Show whether a source file may have multiple base names.
18110 @node Separate Debug Files
18111 @section Debugging Information in Separate Files
18112 @cindex separate debugging information files
18113 @cindex debugging information in separate files
18114 @cindex @file{.debug} subdirectories
18115 @cindex debugging information directory, global
18116 @cindex global debugging information directories
18117 @cindex build ID, and separate debugging files
18118 @cindex @file{.build-id} directory
18120 @value{GDBN} allows you to put a program's debugging information in a
18121 file separate from the executable itself, in a way that allows
18122 @value{GDBN} to find and load the debugging information automatically.
18123 Since debugging information can be very large---sometimes larger
18124 than the executable code itself---some systems distribute debugging
18125 information for their executables in separate files, which users can
18126 install only when they need to debug a problem.
18128 @value{GDBN} supports two ways of specifying the separate debug info
18133 The executable contains a @dfn{debug link} that specifies the name of
18134 the separate debug info file. The separate debug file's name is
18135 usually @file{@var{executable}.debug}, where @var{executable} is the
18136 name of the corresponding executable file without leading directories
18137 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18138 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18139 checksum for the debug file, which @value{GDBN} uses to validate that
18140 the executable and the debug file came from the same build.
18143 The executable contains a @dfn{build ID}, a unique bit string that is
18144 also present in the corresponding debug info file. (This is supported
18145 only on some operating systems, notably those which use the ELF format
18146 for binary files and the @sc{gnu} Binutils.) For more details about
18147 this feature, see the description of the @option{--build-id}
18148 command-line option in @ref{Options, , Command Line Options, ld.info,
18149 The GNU Linker}. The debug info file's name is not specified
18150 explicitly by the build ID, but can be computed from the build ID, see
18154 Depending on the way the debug info file is specified, @value{GDBN}
18155 uses two different methods of looking for the debug file:
18159 For the ``debug link'' method, @value{GDBN} looks up the named file in
18160 the directory of the executable file, then in a subdirectory of that
18161 directory named @file{.debug}, and finally under each one of the global debug
18162 directories, in a subdirectory whose name is identical to the leading
18163 directories of the executable's absolute file name.
18166 For the ``build ID'' method, @value{GDBN} looks in the
18167 @file{.build-id} subdirectory of each one of the global debug directories for
18168 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18169 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18170 are the rest of the bit string. (Real build ID strings are 32 or more
18171 hex characters, not 10.)
18174 So, for example, suppose you ask @value{GDBN} to debug
18175 @file{/usr/bin/ls}, which has a debug link that specifies the
18176 file @file{ls.debug}, and a build ID whose value in hex is
18177 @code{abcdef1234}. If the list of the global debug directories includes
18178 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18179 debug information files, in the indicated order:
18183 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18185 @file{/usr/bin/ls.debug}
18187 @file{/usr/bin/.debug/ls.debug}
18189 @file{/usr/lib/debug/usr/bin/ls.debug}.
18192 @anchor{debug-file-directory}
18193 Global debugging info directories default to what is set by @value{GDBN}
18194 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18195 you can also set the global debugging info directories, and view the list
18196 @value{GDBN} is currently using.
18200 @kindex set debug-file-directory
18201 @item set debug-file-directory @var{directories}
18202 Set the directories which @value{GDBN} searches for separate debugging
18203 information files to @var{directory}. Multiple path components can be set
18204 concatenating them by a path separator.
18206 @kindex show debug-file-directory
18207 @item show debug-file-directory
18208 Show the directories @value{GDBN} searches for separate debugging
18213 @cindex @code{.gnu_debuglink} sections
18214 @cindex debug link sections
18215 A debug link is a special section of the executable file named
18216 @code{.gnu_debuglink}. The section must contain:
18220 A filename, with any leading directory components removed, followed by
18223 zero to three bytes of padding, as needed to reach the next four-byte
18224 boundary within the section, and
18226 a four-byte CRC checksum, stored in the same endianness used for the
18227 executable file itself. The checksum is computed on the debugging
18228 information file's full contents by the function given below, passing
18229 zero as the @var{crc} argument.
18232 Any executable file format can carry a debug link, as long as it can
18233 contain a section named @code{.gnu_debuglink} with the contents
18236 @cindex @code{.note.gnu.build-id} sections
18237 @cindex build ID sections
18238 The build ID is a special section in the executable file (and in other
18239 ELF binary files that @value{GDBN} may consider). This section is
18240 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18241 It contains unique identification for the built files---the ID remains
18242 the same across multiple builds of the same build tree. The default
18243 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18244 content for the build ID string. The same section with an identical
18245 value is present in the original built binary with symbols, in its
18246 stripped variant, and in the separate debugging information file.
18248 The debugging information file itself should be an ordinary
18249 executable, containing a full set of linker symbols, sections, and
18250 debugging information. The sections of the debugging information file
18251 should have the same names, addresses, and sizes as the original file,
18252 but they need not contain any data---much like a @code{.bss} section
18253 in an ordinary executable.
18255 The @sc{gnu} binary utilities (Binutils) package includes the
18256 @samp{objcopy} utility that can produce
18257 the separated executable / debugging information file pairs using the
18258 following commands:
18261 @kbd{objcopy --only-keep-debug foo foo.debug}
18266 These commands remove the debugging
18267 information from the executable file @file{foo} and place it in the file
18268 @file{foo.debug}. You can use the first, second or both methods to link the
18273 The debug link method needs the following additional command to also leave
18274 behind a debug link in @file{foo}:
18277 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18280 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18281 a version of the @code{strip} command such that the command @kbd{strip foo -f
18282 foo.debug} has the same functionality as the two @code{objcopy} commands and
18283 the @code{ln -s} command above, together.
18286 Build ID gets embedded into the main executable using @code{ld --build-id} or
18287 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18288 compatibility fixes for debug files separation are present in @sc{gnu} binary
18289 utilities (Binutils) package since version 2.18.
18294 @cindex CRC algorithm definition
18295 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18296 IEEE 802.3 using the polynomial:
18298 @c TexInfo requires naked braces for multi-digit exponents for Tex
18299 @c output, but this causes HTML output to barf. HTML has to be set using
18300 @c raw commands. So we end up having to specify this equation in 2
18305 <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>
18306 + <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
18312 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18313 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18317 The function is computed byte at a time, taking the least
18318 significant bit of each byte first. The initial pattern
18319 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18320 the final result is inverted to ensure trailing zeros also affect the
18323 @emph{Note:} This is the same CRC polynomial as used in handling the
18324 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18325 However in the case of the Remote Serial Protocol, the CRC is computed
18326 @emph{most} significant bit first, and the result is not inverted, so
18327 trailing zeros have no effect on the CRC value.
18329 To complete the description, we show below the code of the function
18330 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18331 initially supplied @code{crc} argument means that an initial call to
18332 this function passing in zero will start computing the CRC using
18335 @kindex gnu_debuglink_crc32
18338 gnu_debuglink_crc32 (unsigned long crc,
18339 unsigned char *buf, size_t len)
18341 static const unsigned long crc32_table[256] =
18343 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18344 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18345 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18346 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18347 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18348 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18349 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18350 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18351 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18352 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18353 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18354 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18355 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18356 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18357 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18358 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18359 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18360 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18361 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18362 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18363 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18364 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18365 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18366 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18367 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18368 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18369 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18370 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18371 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18372 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18373 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18374 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18375 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18376 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18377 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18378 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18379 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18380 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18381 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18382 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18383 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18384 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18385 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18386 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18387 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18388 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18389 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18390 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18391 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18392 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18393 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18396 unsigned char *end;
18398 crc = ~crc & 0xffffffff;
18399 for (end = buf + len; buf < end; ++buf)
18400 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18401 return ~crc & 0xffffffff;
18406 This computation does not apply to the ``build ID'' method.
18408 @node MiniDebugInfo
18409 @section Debugging information in a special section
18410 @cindex separate debug sections
18411 @cindex @samp{.gnu_debugdata} section
18413 Some systems ship pre-built executables and libraries that have a
18414 special @samp{.gnu_debugdata} section. This feature is called
18415 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18416 is used to supply extra symbols for backtraces.
18418 The intent of this section is to provide extra minimal debugging
18419 information for use in simple backtraces. It is not intended to be a
18420 replacement for full separate debugging information (@pxref{Separate
18421 Debug Files}). The example below shows the intended use; however,
18422 @value{GDBN} does not currently put restrictions on what sort of
18423 debugging information might be included in the section.
18425 @value{GDBN} has support for this extension. If the section exists,
18426 then it is used provided that no other source of debugging information
18427 can be found, and that @value{GDBN} was configured with LZMA support.
18429 This section can be easily created using @command{objcopy} and other
18430 standard utilities:
18433 # Extract the dynamic symbols from the main binary, there is no need
18434 # to also have these in the normal symbol table.
18435 nm -D @var{binary} --format=posix --defined-only \
18436 | awk '@{ print $1 @}' | sort > dynsyms
18438 # Extract all the text (i.e. function) symbols from the debuginfo.
18439 # (Note that we actually also accept "D" symbols, for the benefit
18440 # of platforms like PowerPC64 that use function descriptors.)
18441 nm @var{binary} --format=posix --defined-only \
18442 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18445 # Keep all the function symbols not already in the dynamic symbol
18447 comm -13 dynsyms funcsyms > keep_symbols
18449 # Separate full debug info into debug binary.
18450 objcopy --only-keep-debug @var{binary} debug
18452 # Copy the full debuginfo, keeping only a minimal set of symbols and
18453 # removing some unnecessary sections.
18454 objcopy -S --remove-section .gdb_index --remove-section .comment \
18455 --keep-symbols=keep_symbols debug mini_debuginfo
18457 # Drop the full debug info from the original binary.
18458 strip --strip-all -R .comment @var{binary}
18460 # Inject the compressed data into the .gnu_debugdata section of the
18463 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18467 @section Index Files Speed Up @value{GDBN}
18468 @cindex index files
18469 @cindex @samp{.gdb_index} section
18471 When @value{GDBN} finds a symbol file, it scans the symbols in the
18472 file in order to construct an internal symbol table. This lets most
18473 @value{GDBN} operations work quickly---at the cost of a delay early
18474 on. For large programs, this delay can be quite lengthy, so
18475 @value{GDBN} provides a way to build an index, which speeds up
18478 The index is stored as a section in the symbol file. @value{GDBN} can
18479 write the index to a file, then you can put it into the symbol file
18480 using @command{objcopy}.
18482 To create an index file, use the @code{save gdb-index} command:
18485 @item save gdb-index @var{directory}
18486 @kindex save gdb-index
18487 Create an index file for each symbol file currently known by
18488 @value{GDBN}. Each file is named after its corresponding symbol file,
18489 with @samp{.gdb-index} appended, and is written into the given
18493 Once you have created an index file you can merge it into your symbol
18494 file, here named @file{symfile}, using @command{objcopy}:
18497 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18498 --set-section-flags .gdb_index=readonly symfile symfile
18501 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18502 sections that have been deprecated. Usually they are deprecated because
18503 they are missing a new feature or have performance issues.
18504 To tell @value{GDBN} to use a deprecated index section anyway
18505 specify @code{set use-deprecated-index-sections on}.
18506 The default is @code{off}.
18507 This can speed up startup, but may result in some functionality being lost.
18508 @xref{Index Section Format}.
18510 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18511 must be done before gdb reads the file. The following will not work:
18514 $ gdb -ex "set use-deprecated-index-sections on" <program>
18517 Instead you must do, for example,
18520 $ gdb -iex "set use-deprecated-index-sections on" <program>
18523 There are currently some limitation on indices. They only work when
18524 for DWARF debugging information, not stabs. And, they do not
18525 currently work for programs using Ada.
18527 @node Symbol Errors
18528 @section Errors Reading Symbol Files
18530 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18531 such as symbol types it does not recognize, or known bugs in compiler
18532 output. By default, @value{GDBN} does not notify you of such problems, since
18533 they are relatively common and primarily of interest to people
18534 debugging compilers. If you are interested in seeing information
18535 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18536 only one message about each such type of problem, no matter how many
18537 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18538 to see how many times the problems occur, with the @code{set
18539 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18542 The messages currently printed, and their meanings, include:
18545 @item inner block not inside outer block in @var{symbol}
18547 The symbol information shows where symbol scopes begin and end
18548 (such as at the start of a function or a block of statements). This
18549 error indicates that an inner scope block is not fully contained
18550 in its outer scope blocks.
18552 @value{GDBN} circumvents the problem by treating the inner block as if it had
18553 the same scope as the outer block. In the error message, @var{symbol}
18554 may be shown as ``@code{(don't know)}'' if the outer block is not a
18557 @item block at @var{address} out of order
18559 The symbol information for symbol scope blocks should occur in
18560 order of increasing addresses. This error indicates that it does not
18563 @value{GDBN} does not circumvent this problem, and has trouble
18564 locating symbols in the source file whose symbols it is reading. (You
18565 can often determine what source file is affected by specifying
18566 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18569 @item bad block start address patched
18571 The symbol information for a symbol scope block has a start address
18572 smaller than the address of the preceding source line. This is known
18573 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18575 @value{GDBN} circumvents the problem by treating the symbol scope block as
18576 starting on the previous source line.
18578 @item bad string table offset in symbol @var{n}
18581 Symbol number @var{n} contains a pointer into the string table which is
18582 larger than the size of the string table.
18584 @value{GDBN} circumvents the problem by considering the symbol to have the
18585 name @code{foo}, which may cause other problems if many symbols end up
18588 @item unknown symbol type @code{0x@var{nn}}
18590 The symbol information contains new data types that @value{GDBN} does
18591 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18592 uncomprehended information, in hexadecimal.
18594 @value{GDBN} circumvents the error by ignoring this symbol information.
18595 This usually allows you to debug your program, though certain symbols
18596 are not accessible. If you encounter such a problem and feel like
18597 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18598 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18599 and examine @code{*bufp} to see the symbol.
18601 @item stub type has NULL name
18603 @value{GDBN} could not find the full definition for a struct or class.
18605 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18606 The symbol information for a C@t{++} member function is missing some
18607 information that recent versions of the compiler should have output for
18610 @item info mismatch between compiler and debugger
18612 @value{GDBN} could not parse a type specification output by the compiler.
18617 @section GDB Data Files
18619 @cindex prefix for data files
18620 @value{GDBN} will sometimes read an auxiliary data file. These files
18621 are kept in a directory known as the @dfn{data directory}.
18623 You can set the data directory's name, and view the name @value{GDBN}
18624 is currently using.
18627 @kindex set data-directory
18628 @item set data-directory @var{directory}
18629 Set the directory which @value{GDBN} searches for auxiliary data files
18630 to @var{directory}.
18632 @kindex show data-directory
18633 @item show data-directory
18634 Show the directory @value{GDBN} searches for auxiliary data files.
18637 @cindex default data directory
18638 @cindex @samp{--with-gdb-datadir}
18639 You can set the default data directory by using the configure-time
18640 @samp{--with-gdb-datadir} option. If the data directory is inside
18641 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18642 @samp{--exec-prefix}), then the default data directory will be updated
18643 automatically if the installed @value{GDBN} is moved to a new
18646 The data directory may also be specified with the
18647 @code{--data-directory} command line option.
18648 @xref{Mode Options}.
18651 @chapter Specifying a Debugging Target
18653 @cindex debugging target
18654 A @dfn{target} is the execution environment occupied by your program.
18656 Often, @value{GDBN} runs in the same host environment as your program;
18657 in that case, the debugging target is specified as a side effect when
18658 you use the @code{file} or @code{core} commands. When you need more
18659 flexibility---for example, running @value{GDBN} on a physically separate
18660 host, or controlling a standalone system over a serial port or a
18661 realtime system over a TCP/IP connection---you can use the @code{target}
18662 command to specify one of the target types configured for @value{GDBN}
18663 (@pxref{Target Commands, ,Commands for Managing Targets}).
18665 @cindex target architecture
18666 It is possible to build @value{GDBN} for several different @dfn{target
18667 architectures}. When @value{GDBN} is built like that, you can choose
18668 one of the available architectures with the @kbd{set architecture}
18672 @kindex set architecture
18673 @kindex show architecture
18674 @item set architecture @var{arch}
18675 This command sets the current target architecture to @var{arch}. The
18676 value of @var{arch} can be @code{"auto"}, in addition to one of the
18677 supported architectures.
18679 @item show architecture
18680 Show the current target architecture.
18682 @item set processor
18684 @kindex set processor
18685 @kindex show processor
18686 These are alias commands for, respectively, @code{set architecture}
18687 and @code{show architecture}.
18691 * Active Targets:: Active targets
18692 * Target Commands:: Commands for managing targets
18693 * Byte Order:: Choosing target byte order
18696 @node Active Targets
18697 @section Active Targets
18699 @cindex stacking targets
18700 @cindex active targets
18701 @cindex multiple targets
18703 There are multiple classes of targets such as: processes, executable files or
18704 recording sessions. Core files belong to the process class, making core file
18705 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
18706 on multiple active targets, one in each class. This allows you to (for
18707 example) start a process and inspect its activity, while still having access to
18708 the executable file after the process finishes. Or if you start process
18709 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
18710 presented a virtual layer of the recording target, while the process target
18711 remains stopped at the chronologically last point of the process execution.
18713 Use the @code{core-file} and @code{exec-file} commands to select a new core
18714 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
18715 specify as a target a process that is already running, use the @code{attach}
18716 command (@pxref{Attach, ,Debugging an Already-running Process}).
18718 @node Target Commands
18719 @section Commands for Managing Targets
18722 @item target @var{type} @var{parameters}
18723 Connects the @value{GDBN} host environment to a target machine or
18724 process. A target is typically a protocol for talking to debugging
18725 facilities. You use the argument @var{type} to specify the type or
18726 protocol of the target machine.
18728 Further @var{parameters} are interpreted by the target protocol, but
18729 typically include things like device names or host names to connect
18730 with, process numbers, and baud rates.
18732 The @code{target} command does not repeat if you press @key{RET} again
18733 after executing the command.
18735 @kindex help target
18737 Displays the names of all targets available. To display targets
18738 currently selected, use either @code{info target} or @code{info files}
18739 (@pxref{Files, ,Commands to Specify Files}).
18741 @item help target @var{name}
18742 Describe a particular target, including any parameters necessary to
18745 @kindex set gnutarget
18746 @item set gnutarget @var{args}
18747 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
18748 knows whether it is reading an @dfn{executable},
18749 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
18750 with the @code{set gnutarget} command. Unlike most @code{target} commands,
18751 with @code{gnutarget} the @code{target} refers to a program, not a machine.
18754 @emph{Warning:} To specify a file format with @code{set gnutarget},
18755 you must know the actual BFD name.
18759 @xref{Files, , Commands to Specify Files}.
18761 @kindex show gnutarget
18762 @item show gnutarget
18763 Use the @code{show gnutarget} command to display what file format
18764 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
18765 @value{GDBN} will determine the file format for each file automatically,
18766 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
18769 @cindex common targets
18770 Here are some common targets (available, or not, depending on the GDB
18775 @item target exec @var{program}
18776 @cindex executable file target
18777 An executable file. @samp{target exec @var{program}} is the same as
18778 @samp{exec-file @var{program}}.
18780 @item target core @var{filename}
18781 @cindex core dump file target
18782 A core dump file. @samp{target core @var{filename}} is the same as
18783 @samp{core-file @var{filename}}.
18785 @item target remote @var{medium}
18786 @cindex remote target
18787 A remote system connected to @value{GDBN} via a serial line or network
18788 connection. This command tells @value{GDBN} to use its own remote
18789 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
18791 For example, if you have a board connected to @file{/dev/ttya} on the
18792 machine running @value{GDBN}, you could say:
18795 target remote /dev/ttya
18798 @code{target remote} supports the @code{load} command. This is only
18799 useful if you have some other way of getting the stub to the target
18800 system, and you can put it somewhere in memory where it won't get
18801 clobbered by the download.
18803 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18804 @cindex built-in simulator target
18805 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18813 works; however, you cannot assume that a specific memory map, device
18814 drivers, or even basic I/O is available, although some simulators do
18815 provide these. For info about any processor-specific simulator details,
18816 see the appropriate section in @ref{Embedded Processors, ,Embedded
18819 @item target native
18820 @cindex native target
18821 Setup for local/native process debugging. Useful to make the
18822 @code{run} command spawn native processes (likewise @code{attach},
18823 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
18824 (@pxref{set auto-connect-native-target}).
18828 Different targets are available on different configurations of @value{GDBN};
18829 your configuration may have more or fewer targets.
18831 Many remote targets require you to download the executable's code once
18832 you've successfully established a connection. You may wish to control
18833 various aspects of this process.
18838 @kindex set hash@r{, for remote monitors}
18839 @cindex hash mark while downloading
18840 This command controls whether a hash mark @samp{#} is displayed while
18841 downloading a file to the remote monitor. If on, a hash mark is
18842 displayed after each S-record is successfully downloaded to the
18846 @kindex show hash@r{, for remote monitors}
18847 Show the current status of displaying the hash mark.
18849 @item set debug monitor
18850 @kindex set debug monitor
18851 @cindex display remote monitor communications
18852 Enable or disable display of communications messages between
18853 @value{GDBN} and the remote monitor.
18855 @item show debug monitor
18856 @kindex show debug monitor
18857 Show the current status of displaying communications between
18858 @value{GDBN} and the remote monitor.
18863 @kindex load @var{filename}
18864 @item load @var{filename}
18866 Depending on what remote debugging facilities are configured into
18867 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18868 is meant to make @var{filename} (an executable) available for debugging
18869 on the remote system---by downloading, or dynamic linking, for example.
18870 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18871 the @code{add-symbol-file} command.
18873 If your @value{GDBN} does not have a @code{load} command, attempting to
18874 execute it gets the error message ``@code{You can't do that when your
18875 target is @dots{}}''
18877 The file is loaded at whatever address is specified in the executable.
18878 For some object file formats, you can specify the load address when you
18879 link the program; for other formats, like a.out, the object file format
18880 specifies a fixed address.
18881 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18883 Depending on the remote side capabilities, @value{GDBN} may be able to
18884 load programs into flash memory.
18886 @code{load} does not repeat if you press @key{RET} again after using it.
18890 @section Choosing Target Byte Order
18892 @cindex choosing target byte order
18893 @cindex target byte order
18895 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18896 offer the ability to run either big-endian or little-endian byte
18897 orders. Usually the executable or symbol will include a bit to
18898 designate the endian-ness, and you will not need to worry about
18899 which to use. However, you may still find it useful to adjust
18900 @value{GDBN}'s idea of processor endian-ness manually.
18904 @item set endian big
18905 Instruct @value{GDBN} to assume the target is big-endian.
18907 @item set endian little
18908 Instruct @value{GDBN} to assume the target is little-endian.
18910 @item set endian auto
18911 Instruct @value{GDBN} to use the byte order associated with the
18915 Display @value{GDBN}'s current idea of the target byte order.
18919 Note that these commands merely adjust interpretation of symbolic
18920 data on the host, and that they have absolutely no effect on the
18924 @node Remote Debugging
18925 @chapter Debugging Remote Programs
18926 @cindex remote debugging
18928 If you are trying to debug a program running on a machine that cannot run
18929 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18930 For example, you might use remote debugging on an operating system kernel,
18931 or on a small system which does not have a general purpose operating system
18932 powerful enough to run a full-featured debugger.
18934 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18935 to make this work with particular debugging targets. In addition,
18936 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18937 but not specific to any particular target system) which you can use if you
18938 write the remote stubs---the code that runs on the remote system to
18939 communicate with @value{GDBN}.
18941 Other remote targets may be available in your
18942 configuration of @value{GDBN}; use @code{help target} to list them.
18945 * Connecting:: Connecting to a remote target
18946 * File Transfer:: Sending files to a remote system
18947 * Server:: Using the gdbserver program
18948 * Remote Configuration:: Remote configuration
18949 * Remote Stub:: Implementing a remote stub
18953 @section Connecting to a Remote Target
18955 @value{GDBN} needs an unstripped copy of your program to access symbol
18956 and debugging information. Some remote targets (@pxref{qXfer
18957 executable filename read}, and @pxref{Host I/O Packets}) allow
18958 @value{GDBN} to access program files over the same connection used to
18959 communicate with @value{GDBN}. With such a target, if the remote
18960 program is unstripped, the only command you need is @code{target
18961 remote}. Otherwise, start up @value{GDBN} using the name of the local
18962 unstripped copy of your program as the first argument, or use the
18963 @code{file} command.
18965 @cindex @code{target remote}
18966 @value{GDBN} can communicate with the target over a serial line, or
18967 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18968 each case, @value{GDBN} uses the same protocol for debugging your
18969 program; only the medium carrying the debugging packets varies. The
18970 @code{target remote} command establishes a connection to the target.
18971 Its arguments indicate which medium to use:
18975 @item target remote @var{serial-device}
18976 @cindex serial line, @code{target remote}
18977 Use @var{serial-device} to communicate with the target. For example,
18978 to use a serial line connected to the device named @file{/dev/ttyb}:
18981 target remote /dev/ttyb
18984 If you're using a serial line, you may want to give @value{GDBN} the
18985 @samp{--baud} option, or use the @code{set serial baud} command
18986 (@pxref{Remote Configuration, set serial baud}) before the
18987 @code{target} command.
18989 @item target remote @code{@var{host}:@var{port}}
18990 @itemx target remote @code{tcp:@var{host}:@var{port}}
18991 @cindex @acronym{TCP} port, @code{target remote}
18992 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18993 The @var{host} may be either a host name or a numeric @acronym{IP}
18994 address; @var{port} must be a decimal number. The @var{host} could be
18995 the target machine itself, if it is directly connected to the net, or
18996 it might be a terminal server which in turn has a serial line to the
18999 For example, to connect to port 2828 on a terminal server named
19003 target remote manyfarms:2828
19006 If your remote target is actually running on the same machine as your
19007 debugger session (e.g.@: a simulator for your target running on the
19008 same host), you can omit the hostname. For example, to connect to
19009 port 1234 on your local machine:
19012 target remote :1234
19016 Note that the colon is still required here.
19018 @item target remote @code{udp:@var{host}:@var{port}}
19019 @cindex @acronym{UDP} port, @code{target remote}
19020 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19021 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19024 target remote udp:manyfarms:2828
19027 When using a @acronym{UDP} connection for remote debugging, you should
19028 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19029 can silently drop packets on busy or unreliable networks, which will
19030 cause havoc with your debugging session.
19032 @item target remote | @var{command}
19033 @cindex pipe, @code{target remote} to
19034 Run @var{command} in the background and communicate with it using a
19035 pipe. The @var{command} is a shell command, to be parsed and expanded
19036 by the system's command shell, @code{/bin/sh}; it should expect remote
19037 protocol packets on its standard input, and send replies on its
19038 standard output. You could use this to run a stand-alone simulator
19039 that speaks the remote debugging protocol, to make net connections
19040 using programs like @code{ssh}, or for other similar tricks.
19042 If @var{command} closes its standard output (perhaps by exiting),
19043 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19044 program has already exited, this will have no effect.)
19048 Once the connection has been established, you can use all the usual
19049 commands to examine and change data. The remote program is already
19050 running; you can use @kbd{step} and @kbd{continue}, and you do not
19051 need to use @kbd{run}.
19053 @cindex interrupting remote programs
19054 @cindex remote programs, interrupting
19055 Whenever @value{GDBN} is waiting for the remote program, if you type the
19056 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19057 program. This may or may not succeed, depending in part on the hardware
19058 and the serial drivers the remote system uses. If you type the
19059 interrupt character once again, @value{GDBN} displays this prompt:
19062 Interrupted while waiting for the program.
19063 Give up (and stop debugging it)? (y or n)
19066 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
19067 (If you decide you want to try again later, you can use @samp{target
19068 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
19069 goes back to waiting.
19072 @kindex detach (remote)
19074 When you have finished debugging the remote program, you can use the
19075 @code{detach} command to release it from @value{GDBN} control.
19076 Detaching from the target normally resumes its execution, but the results
19077 will depend on your particular remote stub. After the @code{detach}
19078 command, @value{GDBN} is free to connect to another target.
19082 The @code{disconnect} command behaves like @code{detach}, except that
19083 the target is generally not resumed. It will wait for @value{GDBN}
19084 (this instance or another one) to connect and continue debugging. After
19085 the @code{disconnect} command, @value{GDBN} is again free to connect to
19088 @cindex send command to remote monitor
19089 @cindex extend @value{GDBN} for remote targets
19090 @cindex add new commands for external monitor
19092 @item monitor @var{cmd}
19093 This command allows you to send arbitrary commands directly to the
19094 remote monitor. Since @value{GDBN} doesn't care about the commands it
19095 sends like this, this command is the way to extend @value{GDBN}---you
19096 can add new commands that only the external monitor will understand
19100 @node File Transfer
19101 @section Sending files to a remote system
19102 @cindex remote target, file transfer
19103 @cindex file transfer
19104 @cindex sending files to remote systems
19106 Some remote targets offer the ability to transfer files over the same
19107 connection used to communicate with @value{GDBN}. This is convenient
19108 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19109 running @code{gdbserver} over a network interface. For other targets,
19110 e.g.@: embedded devices with only a single serial port, this may be
19111 the only way to upload or download files.
19113 Not all remote targets support these commands.
19117 @item remote put @var{hostfile} @var{targetfile}
19118 Copy file @var{hostfile} from the host system (the machine running
19119 @value{GDBN}) to @var{targetfile} on the target system.
19122 @item remote get @var{targetfile} @var{hostfile}
19123 Copy file @var{targetfile} from the target system to @var{hostfile}
19124 on the host system.
19126 @kindex remote delete
19127 @item remote delete @var{targetfile}
19128 Delete @var{targetfile} from the target system.
19133 @section Using the @code{gdbserver} Program
19136 @cindex remote connection without stubs
19137 @code{gdbserver} is a control program for Unix-like systems, which
19138 allows you to connect your program with a remote @value{GDBN} via
19139 @code{target remote}---but without linking in the usual debugging stub.
19141 @code{gdbserver} is not a complete replacement for the debugging stubs,
19142 because it requires essentially the same operating-system facilities
19143 that @value{GDBN} itself does. In fact, a system that can run
19144 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19145 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19146 because it is a much smaller program than @value{GDBN} itself. It is
19147 also easier to port than all of @value{GDBN}, so you may be able to get
19148 started more quickly on a new system by using @code{gdbserver}.
19149 Finally, if you develop code for real-time systems, you may find that
19150 the tradeoffs involved in real-time operation make it more convenient to
19151 do as much development work as possible on another system, for example
19152 by cross-compiling. You can use @code{gdbserver} to make a similar
19153 choice for debugging.
19155 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19156 or a TCP connection, using the standard @value{GDBN} remote serial
19160 @emph{Warning:} @code{gdbserver} does not have any built-in security.
19161 Do not run @code{gdbserver} connected to any public network; a
19162 @value{GDBN} connection to @code{gdbserver} provides access to the
19163 target system with the same privileges as the user running
19167 @subsection Running @code{gdbserver}
19168 @cindex arguments, to @code{gdbserver}
19169 @cindex @code{gdbserver}, command-line arguments
19171 Run @code{gdbserver} on the target system. You need a copy of the
19172 program you want to debug, including any libraries it requires.
19173 @code{gdbserver} does not need your program's symbol table, so you can
19174 strip the program if necessary to save space. @value{GDBN} on the host
19175 system does all the symbol handling.
19177 To use the server, you must tell it how to communicate with @value{GDBN};
19178 the name of your program; and the arguments for your program. The usual
19182 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
19185 @var{comm} is either a device name (to use a serial line), or a TCP
19186 hostname and portnumber, or @code{-} or @code{stdio} to use
19187 stdin/stdout of @code{gdbserver}.
19188 For example, to debug Emacs with the argument
19189 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
19193 target> gdbserver /dev/com1 emacs foo.txt
19196 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
19199 To use a TCP connection instead of a serial line:
19202 target> gdbserver host:2345 emacs foo.txt
19205 The only difference from the previous example is the first argument,
19206 specifying that you are communicating with the host @value{GDBN} via
19207 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
19208 expect a TCP connection from machine @samp{host} to local TCP port 2345.
19209 (Currently, the @samp{host} part is ignored.) You can choose any number
19210 you want for the port number as long as it does not conflict with any
19211 TCP ports already in use on the target system (for example, @code{23} is
19212 reserved for @code{telnet}).@footnote{If you choose a port number that
19213 conflicts with another service, @code{gdbserver} prints an error message
19214 and exits.} You must use the same port number with the host @value{GDBN}
19215 @code{target remote} command.
19217 The @code{stdio} connection is useful when starting @code{gdbserver}
19221 (gdb) target remote | ssh -T hostname gdbserver - hello
19224 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19225 and we don't want escape-character handling. Ssh does this by default when
19226 a command is provided, the flag is provided to make it explicit.
19227 You could elide it if you want to.
19229 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19230 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19231 display through a pipe connected to gdbserver.
19232 Both @code{stdout} and @code{stderr} use the same pipe.
19234 @subsubsection Attaching to a Running Program
19235 @cindex attach to a program, @code{gdbserver}
19236 @cindex @option{--attach}, @code{gdbserver} option
19238 On some targets, @code{gdbserver} can also attach to running programs.
19239 This is accomplished via the @code{--attach} argument. The syntax is:
19242 target> gdbserver --attach @var{comm} @var{pid}
19245 @var{pid} is the process ID of a currently running process. It isn't necessary
19246 to point @code{gdbserver} at a binary for the running process.
19249 You can debug processes by name instead of process ID if your target has the
19250 @code{pidof} utility:
19253 target> gdbserver --attach @var{comm} `pidof @var{program}`
19256 In case more than one copy of @var{program} is running, or @var{program}
19257 has multiple threads, most versions of @code{pidof} support the
19258 @code{-s} option to only return the first process ID.
19260 @subsubsection Multi-Process Mode for @code{gdbserver}
19261 @cindex @code{gdbserver}, multiple processes
19262 @cindex multiple processes with @code{gdbserver}
19264 When you connect to @code{gdbserver} using @code{target remote},
19265 @code{gdbserver} debugs the specified program only once. When the
19266 program exits, or you detach from it, @value{GDBN} closes the connection
19267 and @code{gdbserver} exits.
19269 If you connect using @kbd{target extended-remote}, @code{gdbserver}
19270 enters multi-process mode. When the debugged program exits, or you
19271 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
19272 though no program is running. The @code{run} and @code{attach}
19273 commands instruct @code{gdbserver} to run or attach to a new program.
19274 The @code{run} command uses @code{set remote exec-file} (@pxref{set
19275 remote exec-file}) to select the program to run. Command line
19276 arguments are supported, except for wildcard expansion and I/O
19277 redirection (@pxref{Arguments}).
19279 @cindex @option{--multi}, @code{gdbserver} option
19280 To start @code{gdbserver} without supplying an initial command to run
19281 or process ID to attach, use the @option{--multi} command line option.
19282 Then you can connect using @kbd{target extended-remote} and start
19283 the program you want to debug.
19285 In multi-process mode @code{gdbserver} does not automatically exit unless you
19286 use the option @option{--once}. You can terminate it by using
19287 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
19288 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
19289 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
19290 @option{--multi} option to @code{gdbserver} has no influence on that.
19292 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19294 This section applies only when @code{gdbserver} is run to listen on a TCP port.
19296 @code{gdbserver} normally terminates after all of its debugged processes have
19297 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19298 extended-remote}, @code{gdbserver} stays running even with no processes left.
19299 @value{GDBN} normally terminates the spawned debugged process on its exit,
19300 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19301 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19302 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19303 stays running even in the @kbd{target remote} mode.
19305 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19306 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19307 completeness, at most one @value{GDBN} can be connected at a time.
19309 @cindex @option{--once}, @code{gdbserver} option
19310 By default, @code{gdbserver} keeps the listening TCP port open, so that
19311 subsequent connections are possible. However, if you start @code{gdbserver}
19312 with the @option{--once} option, it will stop listening for any further
19313 connection attempts after connecting to the first @value{GDBN} session. This
19314 means no further connections to @code{gdbserver} will be possible after the
19315 first one. It also means @code{gdbserver} will terminate after the first
19316 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19317 connections and even in the @kbd{target extended-remote} mode. The
19318 @option{--once} option allows reusing the same port number for connecting to
19319 multiple instances of @code{gdbserver} running on the same host, since each
19320 instance closes its port after the first connection.
19322 @anchor{Other Command-Line Arguments for gdbserver}
19323 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19325 @cindex @option{--debug}, @code{gdbserver} option
19326 The @option{--debug} option tells @code{gdbserver} to display extra
19327 status information about the debugging process.
19328 @cindex @option{--remote-debug}, @code{gdbserver} option
19329 The @option{--remote-debug} option tells @code{gdbserver} to display
19330 remote protocol debug output. These options are intended for
19331 @code{gdbserver} development and for bug reports to the developers.
19333 @cindex @option{--debug-format}, @code{gdbserver} option
19334 The @option{--debug-format=option1[,option2,...]} option tells
19335 @code{gdbserver} to include additional information in each output.
19336 Possible options are:
19340 Turn off all extra information in debugging output.
19342 Turn on all extra information in debugging output.
19344 Include a timestamp in each line of debugging output.
19347 Options are processed in order. Thus, for example, if @option{none}
19348 appears last then no additional information is added to debugging output.
19350 @cindex @option{--wrapper}, @code{gdbserver} option
19351 The @option{--wrapper} option specifies a wrapper to launch programs
19352 for debugging. The option should be followed by the name of the
19353 wrapper, then any command-line arguments to pass to the wrapper, then
19354 @kbd{--} indicating the end of the wrapper arguments.
19356 @code{gdbserver} runs the specified wrapper program with a combined
19357 command line including the wrapper arguments, then the name of the
19358 program to debug, then any arguments to the program. The wrapper
19359 runs until it executes your program, and then @value{GDBN} gains control.
19361 You can use any program that eventually calls @code{execve} with
19362 its arguments as a wrapper. Several standard Unix utilities do
19363 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19364 with @code{exec "$@@"} will also work.
19366 For example, you can use @code{env} to pass an environment variable to
19367 the debugged program, without setting the variable in @code{gdbserver}'s
19371 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19374 @subsection Connecting to @code{gdbserver}
19376 Run @value{GDBN} on the host system.
19378 First make sure you have the necessary symbol files. Load symbols for
19379 your application using the @code{file} command before you connect. Use
19380 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
19381 was compiled with the correct sysroot using @code{--with-sysroot}).
19383 The symbol file and target libraries must exactly match the executable
19384 and libraries on the target, with one exception: the files on the host
19385 system should not be stripped, even if the files on the target system
19386 are. Mismatched or missing files will lead to confusing results
19387 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19388 files may also prevent @code{gdbserver} from debugging multi-threaded
19391 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19392 For TCP connections, you must start up @code{gdbserver} prior to using
19393 the @code{target remote} command. Otherwise you may get an error whose
19394 text depends on the host system, but which usually looks something like
19395 @samp{Connection refused}. Don't use the @code{load}
19396 command in @value{GDBN} when using @code{gdbserver}, since the program is
19397 already on the target.
19399 @subsection Monitor Commands for @code{gdbserver}
19400 @cindex monitor commands, for @code{gdbserver}
19401 @anchor{Monitor Commands for gdbserver}
19403 During a @value{GDBN} session using @code{gdbserver}, you can use the
19404 @code{monitor} command to send special requests to @code{gdbserver}.
19405 Here are the available commands.
19409 List the available monitor commands.
19411 @item monitor set debug 0
19412 @itemx monitor set debug 1
19413 Disable or enable general debugging messages.
19415 @item monitor set remote-debug 0
19416 @itemx monitor set remote-debug 1
19417 Disable or enable specific debugging messages associated with the remote
19418 protocol (@pxref{Remote Protocol}).
19420 @item monitor set debug-format option1@r{[},option2,...@r{]}
19421 Specify additional text to add to debugging messages.
19422 Possible options are:
19426 Turn off all extra information in debugging output.
19428 Turn on all extra information in debugging output.
19430 Include a timestamp in each line of debugging output.
19433 Options are processed in order. Thus, for example, if @option{none}
19434 appears last then no additional information is added to debugging output.
19436 @item monitor set libthread-db-search-path [PATH]
19437 @cindex gdbserver, search path for @code{libthread_db}
19438 When this command is issued, @var{path} is a colon-separated list of
19439 directories to search for @code{libthread_db} (@pxref{Threads,,set
19440 libthread-db-search-path}). If you omit @var{path},
19441 @samp{libthread-db-search-path} will be reset to its default value.
19443 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19444 not supported in @code{gdbserver}.
19447 Tell gdbserver to exit immediately. This command should be followed by
19448 @code{disconnect} to close the debugging session. @code{gdbserver} will
19449 detach from any attached processes and kill any processes it created.
19450 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19451 of a multi-process mode debug session.
19455 @subsection Tracepoints support in @code{gdbserver}
19456 @cindex tracepoints support in @code{gdbserver}
19458 On some targets, @code{gdbserver} supports tracepoints, fast
19459 tracepoints and static tracepoints.
19461 For fast or static tracepoints to work, a special library called the
19462 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19463 This library is built and distributed as an integral part of
19464 @code{gdbserver}. In addition, support for static tracepoints
19465 requires building the in-process agent library with static tracepoints
19466 support. At present, the UST (LTTng Userspace Tracer,
19467 @url{http://lttng.org/ust}) tracing engine is supported. This support
19468 is automatically available if UST development headers are found in the
19469 standard include path when @code{gdbserver} is built, or if
19470 @code{gdbserver} was explicitly configured using @option{--with-ust}
19471 to point at such headers. You can explicitly disable the support
19472 using @option{--with-ust=no}.
19474 There are several ways to load the in-process agent in your program:
19477 @item Specifying it as dependency at link time
19479 You can link your program dynamically with the in-process agent
19480 library. On most systems, this is accomplished by adding
19481 @code{-linproctrace} to the link command.
19483 @item Using the system's preloading mechanisms
19485 You can force loading the in-process agent at startup time by using
19486 your system's support for preloading shared libraries. Many Unixes
19487 support the concept of preloading user defined libraries. In most
19488 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19489 in the environment. See also the description of @code{gdbserver}'s
19490 @option{--wrapper} command line option.
19492 @item Using @value{GDBN} to force loading the agent at run time
19494 On some systems, you can force the inferior to load a shared library,
19495 by calling a dynamic loader function in the inferior that takes care
19496 of dynamically looking up and loading a shared library. On most Unix
19497 systems, the function is @code{dlopen}. You'll use the @code{call}
19498 command for that. For example:
19501 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19504 Note that on most Unix systems, for the @code{dlopen} function to be
19505 available, the program needs to be linked with @code{-ldl}.
19508 On systems that have a userspace dynamic loader, like most Unix
19509 systems, when you connect to @code{gdbserver} using @code{target
19510 remote}, you'll find that the program is stopped at the dynamic
19511 loader's entry point, and no shared library has been loaded in the
19512 program's address space yet, including the in-process agent. In that
19513 case, before being able to use any of the fast or static tracepoints
19514 features, you need to let the loader run and load the shared
19515 libraries. The simplest way to do that is to run the program to the
19516 main procedure. E.g., if debugging a C or C@t{++} program, start
19517 @code{gdbserver} like so:
19520 $ gdbserver :9999 myprogram
19523 Start GDB and connect to @code{gdbserver} like so, and run to main:
19527 (@value{GDBP}) target remote myhost:9999
19528 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
19529 (@value{GDBP}) b main
19530 (@value{GDBP}) continue
19533 The in-process tracing agent library should now be loaded into the
19534 process; you can confirm it with the @code{info sharedlibrary}
19535 command, which will list @file{libinproctrace.so} as loaded in the
19536 process. You are now ready to install fast tracepoints, list static
19537 tracepoint markers, probe static tracepoints markers, and start
19540 @node Remote Configuration
19541 @section Remote Configuration
19544 @kindex show remote
19545 This section documents the configuration options available when
19546 debugging remote programs. For the options related to the File I/O
19547 extensions of the remote protocol, see @ref{system,
19548 system-call-allowed}.
19551 @item set remoteaddresssize @var{bits}
19552 @cindex address size for remote targets
19553 @cindex bits in remote address
19554 Set the maximum size of address in a memory packet to the specified
19555 number of bits. @value{GDBN} will mask off the address bits above
19556 that number, when it passes addresses to the remote target. The
19557 default value is the number of bits in the target's address.
19559 @item show remoteaddresssize
19560 Show the current value of remote address size in bits.
19562 @item set serial baud @var{n}
19563 @cindex baud rate for remote targets
19564 Set the baud rate for the remote serial I/O to @var{n} baud. The
19565 value is used to set the speed of the serial port used for debugging
19568 @item show serial baud
19569 Show the current speed of the remote connection.
19571 @item set serial parity @var{parity}
19572 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
19573 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
19575 @item show serial parity
19576 Show the current parity of the serial port.
19578 @item set remotebreak
19579 @cindex interrupt remote programs
19580 @cindex BREAK signal instead of Ctrl-C
19581 @anchor{set remotebreak}
19582 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
19583 when you type @kbd{Ctrl-c} to interrupt the program running
19584 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
19585 character instead. The default is off, since most remote systems
19586 expect to see @samp{Ctrl-C} as the interrupt signal.
19588 @item show remotebreak
19589 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
19590 interrupt the remote program.
19592 @item set remoteflow on
19593 @itemx set remoteflow off
19594 @kindex set remoteflow
19595 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
19596 on the serial port used to communicate to the remote target.
19598 @item show remoteflow
19599 @kindex show remoteflow
19600 Show the current setting of hardware flow control.
19602 @item set remotelogbase @var{base}
19603 Set the base (a.k.a.@: radix) of logging serial protocol
19604 communications to @var{base}. Supported values of @var{base} are:
19605 @code{ascii}, @code{octal}, and @code{hex}. The default is
19608 @item show remotelogbase
19609 Show the current setting of the radix for logging remote serial
19612 @item set remotelogfile @var{file}
19613 @cindex record serial communications on file
19614 Record remote serial communications on the named @var{file}. The
19615 default is not to record at all.
19617 @item show remotelogfile.
19618 Show the current setting of the file name on which to record the
19619 serial communications.
19621 @item set remotetimeout @var{num}
19622 @cindex timeout for serial communications
19623 @cindex remote timeout
19624 Set the timeout limit to wait for the remote target to respond to
19625 @var{num} seconds. The default is 2 seconds.
19627 @item show remotetimeout
19628 Show the current number of seconds to wait for the remote target
19631 @cindex limit hardware breakpoints and watchpoints
19632 @cindex remote target, limit break- and watchpoints
19633 @anchor{set remote hardware-watchpoint-limit}
19634 @anchor{set remote hardware-breakpoint-limit}
19635 @item set remote hardware-watchpoint-limit @var{limit}
19636 @itemx set remote hardware-breakpoint-limit @var{limit}
19637 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
19638 watchpoints. A limit of -1, the default, is treated as unlimited.
19640 @cindex limit hardware watchpoints length
19641 @cindex remote target, limit watchpoints length
19642 @anchor{set remote hardware-watchpoint-length-limit}
19643 @item set remote hardware-watchpoint-length-limit @var{limit}
19644 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
19645 a remote hardware watchpoint. A limit of -1, the default, is treated
19648 @item show remote hardware-watchpoint-length-limit
19649 Show the current limit (in bytes) of the maximum length of
19650 a remote hardware watchpoint.
19652 @item set remote exec-file @var{filename}
19653 @itemx show remote exec-file
19654 @anchor{set remote exec-file}
19655 @cindex executable file, for remote target
19656 Select the file used for @code{run} with @code{target
19657 extended-remote}. This should be set to a filename valid on the
19658 target system. If it is not set, the target will use a default
19659 filename (e.g.@: the last program run).
19661 @item set remote interrupt-sequence
19662 @cindex interrupt remote programs
19663 @cindex select Ctrl-C, BREAK or BREAK-g
19664 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
19665 @samp{BREAK-g} as the
19666 sequence to the remote target in order to interrupt the execution.
19667 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
19668 is high level of serial line for some certain time.
19669 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
19670 It is @code{BREAK} signal followed by character @code{g}.
19672 @item show interrupt-sequence
19673 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
19674 is sent by @value{GDBN} to interrupt the remote program.
19675 @code{BREAK-g} is BREAK signal followed by @code{g} and
19676 also known as Magic SysRq g.
19678 @item set remote interrupt-on-connect
19679 @cindex send interrupt-sequence on start
19680 Specify whether interrupt-sequence is sent to remote target when
19681 @value{GDBN} connects to it. This is mostly needed when you debug
19682 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
19683 which is known as Magic SysRq g in order to connect @value{GDBN}.
19685 @item show interrupt-on-connect
19686 Show whether interrupt-sequence is sent
19687 to remote target when @value{GDBN} connects to it.
19691 @item set tcp auto-retry on
19692 @cindex auto-retry, for remote TCP target
19693 Enable auto-retry for remote TCP connections. This is useful if the remote
19694 debugging agent is launched in parallel with @value{GDBN}; there is a race
19695 condition because the agent may not become ready to accept the connection
19696 before @value{GDBN} attempts to connect. When auto-retry is
19697 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
19698 to establish the connection using the timeout specified by
19699 @code{set tcp connect-timeout}.
19701 @item set tcp auto-retry off
19702 Do not auto-retry failed TCP connections.
19704 @item show tcp auto-retry
19705 Show the current auto-retry setting.
19707 @item set tcp connect-timeout @var{seconds}
19708 @itemx set tcp connect-timeout unlimited
19709 @cindex connection timeout, for remote TCP target
19710 @cindex timeout, for remote target connection
19711 Set the timeout for establishing a TCP connection to the remote target to
19712 @var{seconds}. The timeout affects both polling to retry failed connections
19713 (enabled by @code{set tcp auto-retry on}) and waiting for connections
19714 that are merely slow to complete, and represents an approximate cumulative
19715 value. If @var{seconds} is @code{unlimited}, there is no timeout and
19716 @value{GDBN} will keep attempting to establish a connection forever,
19717 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
19719 @item show tcp connect-timeout
19720 Show the current connection timeout setting.
19723 @cindex remote packets, enabling and disabling
19724 The @value{GDBN} remote protocol autodetects the packets supported by
19725 your debugging stub. If you need to override the autodetection, you
19726 can use these commands to enable or disable individual packets. Each
19727 packet can be set to @samp{on} (the remote target supports this
19728 packet), @samp{off} (the remote target does not support this packet),
19729 or @samp{auto} (detect remote target support for this packet). They
19730 all default to @samp{auto}. For more information about each packet,
19731 see @ref{Remote Protocol}.
19733 During normal use, you should not have to use any of these commands.
19734 If you do, that may be a bug in your remote debugging stub, or a bug
19735 in @value{GDBN}. You may want to report the problem to the
19736 @value{GDBN} developers.
19738 For each packet @var{name}, the command to enable or disable the
19739 packet is @code{set remote @var{name}-packet}. The available settings
19742 @multitable @columnfractions 0.28 0.32 0.25
19745 @tab Related Features
19747 @item @code{fetch-register}
19749 @tab @code{info registers}
19751 @item @code{set-register}
19755 @item @code{binary-download}
19757 @tab @code{load}, @code{set}
19759 @item @code{read-aux-vector}
19760 @tab @code{qXfer:auxv:read}
19761 @tab @code{info auxv}
19763 @item @code{symbol-lookup}
19764 @tab @code{qSymbol}
19765 @tab Detecting multiple threads
19767 @item @code{attach}
19768 @tab @code{vAttach}
19771 @item @code{verbose-resume}
19773 @tab Stepping or resuming multiple threads
19779 @item @code{software-breakpoint}
19783 @item @code{hardware-breakpoint}
19787 @item @code{write-watchpoint}
19791 @item @code{read-watchpoint}
19795 @item @code{access-watchpoint}
19799 @item @code{pid-to-exec-file}
19800 @tab @code{qXfer:exec-file:read}
19801 @tab @code{attach}, @code{run}
19803 @item @code{target-features}
19804 @tab @code{qXfer:features:read}
19805 @tab @code{set architecture}
19807 @item @code{library-info}
19808 @tab @code{qXfer:libraries:read}
19809 @tab @code{info sharedlibrary}
19811 @item @code{memory-map}
19812 @tab @code{qXfer:memory-map:read}
19813 @tab @code{info mem}
19815 @item @code{read-sdata-object}
19816 @tab @code{qXfer:sdata:read}
19817 @tab @code{print $_sdata}
19819 @item @code{read-spu-object}
19820 @tab @code{qXfer:spu:read}
19821 @tab @code{info spu}
19823 @item @code{write-spu-object}
19824 @tab @code{qXfer:spu:write}
19825 @tab @code{info spu}
19827 @item @code{read-siginfo-object}
19828 @tab @code{qXfer:siginfo:read}
19829 @tab @code{print $_siginfo}
19831 @item @code{write-siginfo-object}
19832 @tab @code{qXfer:siginfo:write}
19833 @tab @code{set $_siginfo}
19835 @item @code{threads}
19836 @tab @code{qXfer:threads:read}
19837 @tab @code{info threads}
19839 @item @code{get-thread-local-@*storage-address}
19840 @tab @code{qGetTLSAddr}
19841 @tab Displaying @code{__thread} variables
19843 @item @code{get-thread-information-block-address}
19844 @tab @code{qGetTIBAddr}
19845 @tab Display MS-Windows Thread Information Block.
19847 @item @code{search-memory}
19848 @tab @code{qSearch:memory}
19851 @item @code{supported-packets}
19852 @tab @code{qSupported}
19853 @tab Remote communications parameters
19855 @item @code{pass-signals}
19856 @tab @code{QPassSignals}
19857 @tab @code{handle @var{signal}}
19859 @item @code{program-signals}
19860 @tab @code{QProgramSignals}
19861 @tab @code{handle @var{signal}}
19863 @item @code{hostio-close-packet}
19864 @tab @code{vFile:close}
19865 @tab @code{remote get}, @code{remote put}
19867 @item @code{hostio-open-packet}
19868 @tab @code{vFile:open}
19869 @tab @code{remote get}, @code{remote put}
19871 @item @code{hostio-pread-packet}
19872 @tab @code{vFile:pread}
19873 @tab @code{remote get}, @code{remote put}
19875 @item @code{hostio-pwrite-packet}
19876 @tab @code{vFile:pwrite}
19877 @tab @code{remote get}, @code{remote put}
19879 @item @code{hostio-unlink-packet}
19880 @tab @code{vFile:unlink}
19881 @tab @code{remote delete}
19883 @item @code{hostio-readlink-packet}
19884 @tab @code{vFile:readlink}
19887 @item @code{hostio-fstat-packet}
19888 @tab @code{vFile:fstat}
19891 @item @code{noack-packet}
19892 @tab @code{QStartNoAckMode}
19893 @tab Packet acknowledgment
19895 @item @code{osdata}
19896 @tab @code{qXfer:osdata:read}
19897 @tab @code{info os}
19899 @item @code{query-attached}
19900 @tab @code{qAttached}
19901 @tab Querying remote process attach state.
19903 @item @code{trace-buffer-size}
19904 @tab @code{QTBuffer:size}
19905 @tab @code{set trace-buffer-size}
19907 @item @code{trace-status}
19908 @tab @code{qTStatus}
19909 @tab @code{tstatus}
19911 @item @code{traceframe-info}
19912 @tab @code{qXfer:traceframe-info:read}
19913 @tab Traceframe info
19915 @item @code{install-in-trace}
19916 @tab @code{InstallInTrace}
19917 @tab Install tracepoint in tracing
19919 @item @code{disable-randomization}
19920 @tab @code{QDisableRandomization}
19921 @tab @code{set disable-randomization}
19923 @item @code{conditional-breakpoints-packet}
19924 @tab @code{Z0 and Z1}
19925 @tab @code{Support for target-side breakpoint condition evaluation}
19927 @item @code{swbreak-feature}
19928 @tab @code{swbreak stop reason}
19931 @item @code{hwbreak-feature}
19932 @tab @code{hwbreak stop reason}
19938 @section Implementing a Remote Stub
19940 @cindex debugging stub, example
19941 @cindex remote stub, example
19942 @cindex stub example, remote debugging
19943 The stub files provided with @value{GDBN} implement the target side of the
19944 communication protocol, and the @value{GDBN} side is implemented in the
19945 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19946 these subroutines to communicate, and ignore the details. (If you're
19947 implementing your own stub file, you can still ignore the details: start
19948 with one of the existing stub files. @file{sparc-stub.c} is the best
19949 organized, and therefore the easiest to read.)
19951 @cindex remote serial debugging, overview
19952 To debug a program running on another machine (the debugging
19953 @dfn{target} machine), you must first arrange for all the usual
19954 prerequisites for the program to run by itself. For example, for a C
19959 A startup routine to set up the C runtime environment; these usually
19960 have a name like @file{crt0}. The startup routine may be supplied by
19961 your hardware supplier, or you may have to write your own.
19964 A C subroutine library to support your program's
19965 subroutine calls, notably managing input and output.
19968 A way of getting your program to the other machine---for example, a
19969 download program. These are often supplied by the hardware
19970 manufacturer, but you may have to write your own from hardware
19974 The next step is to arrange for your program to use a serial port to
19975 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19976 machine). In general terms, the scheme looks like this:
19980 @value{GDBN} already understands how to use this protocol; when everything
19981 else is set up, you can simply use the @samp{target remote} command
19982 (@pxref{Targets,,Specifying a Debugging Target}).
19984 @item On the target,
19985 you must link with your program a few special-purpose subroutines that
19986 implement the @value{GDBN} remote serial protocol. The file containing these
19987 subroutines is called a @dfn{debugging stub}.
19989 On certain remote targets, you can use an auxiliary program
19990 @code{gdbserver} instead of linking a stub into your program.
19991 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19994 The debugging stub is specific to the architecture of the remote
19995 machine; for example, use @file{sparc-stub.c} to debug programs on
19998 @cindex remote serial stub list
19999 These working remote stubs are distributed with @value{GDBN}:
20004 @cindex @file{i386-stub.c}
20007 For Intel 386 and compatible architectures.
20010 @cindex @file{m68k-stub.c}
20011 @cindex Motorola 680x0
20013 For Motorola 680x0 architectures.
20016 @cindex @file{sh-stub.c}
20019 For Renesas SH architectures.
20022 @cindex @file{sparc-stub.c}
20024 For @sc{sparc} architectures.
20026 @item sparcl-stub.c
20027 @cindex @file{sparcl-stub.c}
20030 For Fujitsu @sc{sparclite} architectures.
20034 The @file{README} file in the @value{GDBN} distribution may list other
20035 recently added stubs.
20038 * Stub Contents:: What the stub can do for you
20039 * Bootstrapping:: What you must do for the stub
20040 * Debug Session:: Putting it all together
20043 @node Stub Contents
20044 @subsection What the Stub Can Do for You
20046 @cindex remote serial stub
20047 The debugging stub for your architecture supplies these three
20051 @item set_debug_traps
20052 @findex set_debug_traps
20053 @cindex remote serial stub, initialization
20054 This routine arranges for @code{handle_exception} to run when your
20055 program stops. You must call this subroutine explicitly in your
20056 program's startup code.
20058 @item handle_exception
20059 @findex handle_exception
20060 @cindex remote serial stub, main routine
20061 This is the central workhorse, but your program never calls it
20062 explicitly---the setup code arranges for @code{handle_exception} to
20063 run when a trap is triggered.
20065 @code{handle_exception} takes control when your program stops during
20066 execution (for example, on a breakpoint), and mediates communications
20067 with @value{GDBN} on the host machine. This is where the communications
20068 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20069 representative on the target machine. It begins by sending summary
20070 information on the state of your program, then continues to execute,
20071 retrieving and transmitting any information @value{GDBN} needs, until you
20072 execute a @value{GDBN} command that makes your program resume; at that point,
20073 @code{handle_exception} returns control to your own code on the target
20077 @cindex @code{breakpoint} subroutine, remote
20078 Use this auxiliary subroutine to make your program contain a
20079 breakpoint. Depending on the particular situation, this may be the only
20080 way for @value{GDBN} to get control. For instance, if your target
20081 machine has some sort of interrupt button, you won't need to call this;
20082 pressing the interrupt button transfers control to
20083 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20084 simply receiving characters on the serial port may also trigger a trap;
20085 again, in that situation, you don't need to call @code{breakpoint} from
20086 your own program---simply running @samp{target remote} from the host
20087 @value{GDBN} session gets control.
20089 Call @code{breakpoint} if none of these is true, or if you simply want
20090 to make certain your program stops at a predetermined point for the
20091 start of your debugging session.
20094 @node Bootstrapping
20095 @subsection What You Must Do for the Stub
20097 @cindex remote stub, support routines
20098 The debugging stubs that come with @value{GDBN} are set up for a particular
20099 chip architecture, but they have no information about the rest of your
20100 debugging target machine.
20102 First of all you need to tell the stub how to communicate with the
20106 @item int getDebugChar()
20107 @findex getDebugChar
20108 Write this subroutine to read a single character from the serial port.
20109 It may be identical to @code{getchar} for your target system; a
20110 different name is used to allow you to distinguish the two if you wish.
20112 @item void putDebugChar(int)
20113 @findex putDebugChar
20114 Write this subroutine to write a single character to the serial port.
20115 It may be identical to @code{putchar} for your target system; a
20116 different name is used to allow you to distinguish the two if you wish.
20119 @cindex control C, and remote debugging
20120 @cindex interrupting remote targets
20121 If you want @value{GDBN} to be able to stop your program while it is
20122 running, you need to use an interrupt-driven serial driver, and arrange
20123 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20124 character). That is the character which @value{GDBN} uses to tell the
20125 remote system to stop.
20127 Getting the debugging target to return the proper status to @value{GDBN}
20128 probably requires changes to the standard stub; one quick and dirty way
20129 is to just execute a breakpoint instruction (the ``dirty'' part is that
20130 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20132 Other routines you need to supply are:
20135 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20136 @findex exceptionHandler
20137 Write this function to install @var{exception_address} in the exception
20138 handling tables. You need to do this because the stub does not have any
20139 way of knowing what the exception handling tables on your target system
20140 are like (for example, the processor's table might be in @sc{rom},
20141 containing entries which point to a table in @sc{ram}).
20142 The @var{exception_number} specifies the exception which should be changed;
20143 its meaning is architecture-dependent (for example, different numbers
20144 might represent divide by zero, misaligned access, etc). When this
20145 exception occurs, control should be transferred directly to
20146 @var{exception_address}, and the processor state (stack, registers,
20147 and so on) should be just as it is when a processor exception occurs. So if
20148 you want to use a jump instruction to reach @var{exception_address}, it
20149 should be a simple jump, not a jump to subroutine.
20151 For the 386, @var{exception_address} should be installed as an interrupt
20152 gate so that interrupts are masked while the handler runs. The gate
20153 should be at privilege level 0 (the most privileged level). The
20154 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
20155 help from @code{exceptionHandler}.
20157 @item void flush_i_cache()
20158 @findex flush_i_cache
20159 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
20160 instruction cache, if any, on your target machine. If there is no
20161 instruction cache, this subroutine may be a no-op.
20163 On target machines that have instruction caches, @value{GDBN} requires this
20164 function to make certain that the state of your program is stable.
20168 You must also make sure this library routine is available:
20171 @item void *memset(void *, int, int)
20173 This is the standard library function @code{memset} that sets an area of
20174 memory to a known value. If you have one of the free versions of
20175 @code{libc.a}, @code{memset} can be found there; otherwise, you must
20176 either obtain it from your hardware manufacturer, or write your own.
20179 If you do not use the GNU C compiler, you may need other standard
20180 library subroutines as well; this varies from one stub to another,
20181 but in general the stubs are likely to use any of the common library
20182 subroutines which @code{@value{NGCC}} generates as inline code.
20185 @node Debug Session
20186 @subsection Putting it All Together
20188 @cindex remote serial debugging summary
20189 In summary, when your program is ready to debug, you must follow these
20194 Make sure you have defined the supporting low-level routines
20195 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
20197 @code{getDebugChar}, @code{putDebugChar},
20198 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
20202 Insert these lines in your program's startup code, before the main
20203 procedure is called:
20210 On some machines, when a breakpoint trap is raised, the hardware
20211 automatically makes the PC point to the instruction after the
20212 breakpoint. If your machine doesn't do that, you may need to adjust
20213 @code{handle_exception} to arrange for it to return to the instruction
20214 after the breakpoint on this first invocation, so that your program
20215 doesn't keep hitting the initial breakpoint instead of making
20219 For the 680x0 stub only, you need to provide a variable called
20220 @code{exceptionHook}. Normally you just use:
20223 void (*exceptionHook)() = 0;
20227 but if before calling @code{set_debug_traps}, you set it to point to a
20228 function in your program, that function is called when
20229 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
20230 error). The function indicated by @code{exceptionHook} is called with
20231 one parameter: an @code{int} which is the exception number.
20234 Compile and link together: your program, the @value{GDBN} debugging stub for
20235 your target architecture, and the supporting subroutines.
20238 Make sure you have a serial connection between your target machine and
20239 the @value{GDBN} host, and identify the serial port on the host.
20242 @c The "remote" target now provides a `load' command, so we should
20243 @c document that. FIXME.
20244 Download your program to your target machine (or get it there by
20245 whatever means the manufacturer provides), and start it.
20248 Start @value{GDBN} on the host, and connect to the target
20249 (@pxref{Connecting,,Connecting to a Remote Target}).
20253 @node Configurations
20254 @chapter Configuration-Specific Information
20256 While nearly all @value{GDBN} commands are available for all native and
20257 cross versions of the debugger, there are some exceptions. This chapter
20258 describes things that are only available in certain configurations.
20260 There are three major categories of configurations: native
20261 configurations, where the host and target are the same, embedded
20262 operating system configurations, which are usually the same for several
20263 different processor architectures, and bare embedded processors, which
20264 are quite different from each other.
20269 * Embedded Processors::
20276 This section describes details specific to particular native
20281 * BSD libkvm Interface:: Debugging BSD kernel memory images
20282 * SVR4 Process Information:: SVR4 process information
20283 * DJGPP Native:: Features specific to the DJGPP port
20284 * Cygwin Native:: Features specific to the Cygwin port
20285 * Hurd Native:: Features specific to @sc{gnu} Hurd
20286 * Darwin:: Features specific to Darwin
20292 On HP-UX systems, if you refer to a function or variable name that
20293 begins with a dollar sign, @value{GDBN} searches for a user or system
20294 name first, before it searches for a convenience variable.
20297 @node BSD libkvm Interface
20298 @subsection BSD libkvm Interface
20301 @cindex kernel memory image
20302 @cindex kernel crash dump
20304 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
20305 interface that provides a uniform interface for accessing kernel virtual
20306 memory images, including live systems and crash dumps. @value{GDBN}
20307 uses this interface to allow you to debug live kernels and kernel crash
20308 dumps on many native BSD configurations. This is implemented as a
20309 special @code{kvm} debugging target. For debugging a live system, load
20310 the currently running kernel into @value{GDBN} and connect to the
20314 (@value{GDBP}) @b{target kvm}
20317 For debugging crash dumps, provide the file name of the crash dump as an
20321 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20324 Once connected to the @code{kvm} target, the following commands are
20330 Set current context from the @dfn{Process Control Block} (PCB) address.
20333 Set current context from proc address. This command isn't available on
20334 modern FreeBSD systems.
20337 @node SVR4 Process Information
20338 @subsection SVR4 Process Information
20340 @cindex examine process image
20341 @cindex process info via @file{/proc}
20343 Many versions of SVR4 and compatible systems provide a facility called
20344 @samp{/proc} that can be used to examine the image of a running
20345 process using file-system subroutines.
20347 If @value{GDBN} is configured for an operating system with this
20348 facility, the command @code{info proc} is available to report
20349 information about the process running your program, or about any
20350 process running on your system. This includes, as of this writing,
20351 @sc{gnu}/Linux and Solaris, but not HP-UX, for example.
20353 This command may also work on core files that were created on a system
20354 that has the @samp{/proc} facility.
20360 @itemx info proc @var{process-id}
20361 Summarize available information about any running process. If a
20362 process ID is specified by @var{process-id}, display information about
20363 that process; otherwise display information about the program being
20364 debugged. The summary includes the debugged process ID, the command
20365 line used to invoke it, its current working directory, and its
20366 executable file's absolute file name.
20368 On some systems, @var{process-id} can be of the form
20369 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20370 within a process. If the optional @var{pid} part is missing, it means
20371 a thread from the process being debugged (the leading @samp{/} still
20372 needs to be present, or else @value{GDBN} will interpret the number as
20373 a process ID rather than a thread ID).
20375 @item info proc cmdline
20376 @cindex info proc cmdline
20377 Show the original command line of the process. This command is
20378 specific to @sc{gnu}/Linux.
20380 @item info proc cwd
20381 @cindex info proc cwd
20382 Show the current working directory of the process. This command is
20383 specific to @sc{gnu}/Linux.
20385 @item info proc exe
20386 @cindex info proc exe
20387 Show the name of executable of the process. This command is specific
20390 @item info proc mappings
20391 @cindex memory address space mappings
20392 Report the memory address space ranges accessible in the program, with
20393 information on whether the process has read, write, or execute access
20394 rights to each range. On @sc{gnu}/Linux systems, each memory range
20395 includes the object file which is mapped to that range, instead of the
20396 memory access rights to that range.
20398 @item info proc stat
20399 @itemx info proc status
20400 @cindex process detailed status information
20401 These subcommands are specific to @sc{gnu}/Linux systems. They show
20402 the process-related information, including the user ID and group ID;
20403 how many threads are there in the process; its virtual memory usage;
20404 the signals that are pending, blocked, and ignored; its TTY; its
20405 consumption of system and user time; its stack size; its @samp{nice}
20406 value; etc. For more information, see the @samp{proc} man page
20407 (type @kbd{man 5 proc} from your shell prompt).
20409 @item info proc all
20410 Show all the information about the process described under all of the
20411 above @code{info proc} subcommands.
20414 @comment These sub-options of 'info proc' were not included when
20415 @comment procfs.c was re-written. Keep their descriptions around
20416 @comment against the day when someone finds the time to put them back in.
20417 @kindex info proc times
20418 @item info proc times
20419 Starting time, user CPU time, and system CPU time for your program and
20422 @kindex info proc id
20424 Report on the process IDs related to your program: its own process ID,
20425 the ID of its parent, the process group ID, and the session ID.
20428 @item set procfs-trace
20429 @kindex set procfs-trace
20430 @cindex @code{procfs} API calls
20431 This command enables and disables tracing of @code{procfs} API calls.
20433 @item show procfs-trace
20434 @kindex show procfs-trace
20435 Show the current state of @code{procfs} API call tracing.
20437 @item set procfs-file @var{file}
20438 @kindex set procfs-file
20439 Tell @value{GDBN} to write @code{procfs} API trace to the named
20440 @var{file}. @value{GDBN} appends the trace info to the previous
20441 contents of the file. The default is to display the trace on the
20444 @item show procfs-file
20445 @kindex show procfs-file
20446 Show the file to which @code{procfs} API trace is written.
20448 @item proc-trace-entry
20449 @itemx proc-trace-exit
20450 @itemx proc-untrace-entry
20451 @itemx proc-untrace-exit
20452 @kindex proc-trace-entry
20453 @kindex proc-trace-exit
20454 @kindex proc-untrace-entry
20455 @kindex proc-untrace-exit
20456 These commands enable and disable tracing of entries into and exits
20457 from the @code{syscall} interface.
20460 @kindex info pidlist
20461 @cindex process list, QNX Neutrino
20462 For QNX Neutrino only, this command displays the list of all the
20463 processes and all the threads within each process.
20466 @kindex info meminfo
20467 @cindex mapinfo list, QNX Neutrino
20468 For QNX Neutrino only, this command displays the list of all mapinfos.
20472 @subsection Features for Debugging @sc{djgpp} Programs
20473 @cindex @sc{djgpp} debugging
20474 @cindex native @sc{djgpp} debugging
20475 @cindex MS-DOS-specific commands
20478 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20479 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20480 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20481 top of real-mode DOS systems and their emulations.
20483 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20484 defines a few commands specific to the @sc{djgpp} port. This
20485 subsection describes those commands.
20490 This is a prefix of @sc{djgpp}-specific commands which print
20491 information about the target system and important OS structures.
20494 @cindex MS-DOS system info
20495 @cindex free memory information (MS-DOS)
20496 @item info dos sysinfo
20497 This command displays assorted information about the underlying
20498 platform: the CPU type and features, the OS version and flavor, the
20499 DPMI version, and the available conventional and DPMI memory.
20504 @cindex segment descriptor tables
20505 @cindex descriptor tables display
20507 @itemx info dos ldt
20508 @itemx info dos idt
20509 These 3 commands display entries from, respectively, Global, Local,
20510 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
20511 tables are data structures which store a descriptor for each segment
20512 that is currently in use. The segment's selector is an index into a
20513 descriptor table; the table entry for that index holds the
20514 descriptor's base address and limit, and its attributes and access
20517 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
20518 segment (used for both data and the stack), and a DOS segment (which
20519 allows access to DOS/BIOS data structures and absolute addresses in
20520 conventional memory). However, the DPMI host will usually define
20521 additional segments in order to support the DPMI environment.
20523 @cindex garbled pointers
20524 These commands allow to display entries from the descriptor tables.
20525 Without an argument, all entries from the specified table are
20526 displayed. An argument, which should be an integer expression, means
20527 display a single entry whose index is given by the argument. For
20528 example, here's a convenient way to display information about the
20529 debugged program's data segment:
20532 @exdent @code{(@value{GDBP}) info dos ldt $ds}
20533 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
20537 This comes in handy when you want to see whether a pointer is outside
20538 the data segment's limit (i.e.@: @dfn{garbled}).
20540 @cindex page tables display (MS-DOS)
20542 @itemx info dos pte
20543 These two commands display entries from, respectively, the Page
20544 Directory and the Page Tables. Page Directories and Page Tables are
20545 data structures which control how virtual memory addresses are mapped
20546 into physical addresses. A Page Table includes an entry for every
20547 page of memory that is mapped into the program's address space; there
20548 may be several Page Tables, each one holding up to 4096 entries. A
20549 Page Directory has up to 4096 entries, one each for every Page Table
20550 that is currently in use.
20552 Without an argument, @kbd{info dos pde} displays the entire Page
20553 Directory, and @kbd{info dos pte} displays all the entries in all of
20554 the Page Tables. An argument, an integer expression, given to the
20555 @kbd{info dos pde} command means display only that entry from the Page
20556 Directory table. An argument given to the @kbd{info dos pte} command
20557 means display entries from a single Page Table, the one pointed to by
20558 the specified entry in the Page Directory.
20560 @cindex direct memory access (DMA) on MS-DOS
20561 These commands are useful when your program uses @dfn{DMA} (Direct
20562 Memory Access), which needs physical addresses to program the DMA
20565 These commands are supported only with some DPMI servers.
20567 @cindex physical address from linear address
20568 @item info dos address-pte @var{addr}
20569 This command displays the Page Table entry for a specified linear
20570 address. The argument @var{addr} is a linear address which should
20571 already have the appropriate segment's base address added to it,
20572 because this command accepts addresses which may belong to @emph{any}
20573 segment. For example, here's how to display the Page Table entry for
20574 the page where a variable @code{i} is stored:
20577 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
20578 @exdent @code{Page Table entry for address 0x11a00d30:}
20579 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
20583 This says that @code{i} is stored at offset @code{0xd30} from the page
20584 whose physical base address is @code{0x02698000}, and shows all the
20585 attributes of that page.
20587 Note that you must cast the addresses of variables to a @code{char *},
20588 since otherwise the value of @code{__djgpp_base_address}, the base
20589 address of all variables and functions in a @sc{djgpp} program, will
20590 be added using the rules of C pointer arithmetics: if @code{i} is
20591 declared an @code{int}, @value{GDBN} will add 4 times the value of
20592 @code{__djgpp_base_address} to the address of @code{i}.
20594 Here's another example, it displays the Page Table entry for the
20598 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
20599 @exdent @code{Page Table entry for address 0x29110:}
20600 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
20604 (The @code{+ 3} offset is because the transfer buffer's address is the
20605 3rd member of the @code{_go32_info_block} structure.) The output
20606 clearly shows that this DPMI server maps the addresses in conventional
20607 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
20608 linear (@code{0x29110}) addresses are identical.
20610 This command is supported only with some DPMI servers.
20613 @cindex DOS serial data link, remote debugging
20614 In addition to native debugging, the DJGPP port supports remote
20615 debugging via a serial data link. The following commands are specific
20616 to remote serial debugging in the DJGPP port of @value{GDBN}.
20619 @kindex set com1base
20620 @kindex set com1irq
20621 @kindex set com2base
20622 @kindex set com2irq
20623 @kindex set com3base
20624 @kindex set com3irq
20625 @kindex set com4base
20626 @kindex set com4irq
20627 @item set com1base @var{addr}
20628 This command sets the base I/O port address of the @file{COM1} serial
20631 @item set com1irq @var{irq}
20632 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
20633 for the @file{COM1} serial port.
20635 There are similar commands @samp{set com2base}, @samp{set com3irq},
20636 etc.@: for setting the port address and the @code{IRQ} lines for the
20639 @kindex show com1base
20640 @kindex show com1irq
20641 @kindex show com2base
20642 @kindex show com2irq
20643 @kindex show com3base
20644 @kindex show com3irq
20645 @kindex show com4base
20646 @kindex show com4irq
20647 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
20648 display the current settings of the base address and the @code{IRQ}
20649 lines used by the COM ports.
20652 @kindex info serial
20653 @cindex DOS serial port status
20654 This command prints the status of the 4 DOS serial ports. For each
20655 port, it prints whether it's active or not, its I/O base address and
20656 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
20657 counts of various errors encountered so far.
20661 @node Cygwin Native
20662 @subsection Features for Debugging MS Windows PE Executables
20663 @cindex MS Windows debugging
20664 @cindex native Cygwin debugging
20665 @cindex Cygwin-specific commands
20667 @value{GDBN} supports native debugging of MS Windows programs, including
20668 DLLs with and without symbolic debugging information.
20670 @cindex Ctrl-BREAK, MS-Windows
20671 @cindex interrupt debuggee on MS-Windows
20672 MS-Windows programs that call @code{SetConsoleMode} to switch off the
20673 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
20674 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
20675 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
20676 sequence, which can be used to interrupt the debuggee even if it
20679 There are various additional Cygwin-specific commands, described in
20680 this section. Working with DLLs that have no debugging symbols is
20681 described in @ref{Non-debug DLL Symbols}.
20686 This is a prefix of MS Windows-specific commands which print
20687 information about the target system and important OS structures.
20689 @item info w32 selector
20690 This command displays information returned by
20691 the Win32 API @code{GetThreadSelectorEntry} function.
20692 It takes an optional argument that is evaluated to
20693 a long value to give the information about this given selector.
20694 Without argument, this command displays information
20695 about the six segment registers.
20697 @item info w32 thread-information-block
20698 This command displays thread specific information stored in the
20699 Thread Information Block (readable on the X86 CPU family using @code{$fs}
20700 selector for 32-bit programs and @code{$gs} for 64-bit programs).
20704 This is a Cygwin-specific alias of @code{info shared}.
20706 @kindex set cygwin-exceptions
20707 @cindex debugging the Cygwin DLL
20708 @cindex Cygwin DLL, debugging
20709 @item set cygwin-exceptions @var{mode}
20710 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
20711 happen inside the Cygwin DLL. If @var{mode} is @code{off},
20712 @value{GDBN} will delay recognition of exceptions, and may ignore some
20713 exceptions which seem to be caused by internal Cygwin DLL
20714 ``bookkeeping''. This option is meant primarily for debugging the
20715 Cygwin DLL itself; the default value is @code{off} to avoid annoying
20716 @value{GDBN} users with false @code{SIGSEGV} signals.
20718 @kindex show cygwin-exceptions
20719 @item show cygwin-exceptions
20720 Displays whether @value{GDBN} will break on exceptions that happen
20721 inside the Cygwin DLL itself.
20723 @kindex set new-console
20724 @item set new-console @var{mode}
20725 If @var{mode} is @code{on} the debuggee will
20726 be started in a new console on next start.
20727 If @var{mode} is @code{off}, the debuggee will
20728 be started in the same console as the debugger.
20730 @kindex show new-console
20731 @item show new-console
20732 Displays whether a new console is used
20733 when the debuggee is started.
20735 @kindex set new-group
20736 @item set new-group @var{mode}
20737 This boolean value controls whether the debuggee should
20738 start a new group or stay in the same group as the debugger.
20739 This affects the way the Windows OS handles
20742 @kindex show new-group
20743 @item show new-group
20744 Displays current value of new-group boolean.
20746 @kindex set debugevents
20747 @item set debugevents
20748 This boolean value adds debug output concerning kernel events related
20749 to the debuggee seen by the debugger. This includes events that
20750 signal thread and process creation and exit, DLL loading and
20751 unloading, console interrupts, and debugging messages produced by the
20752 Windows @code{OutputDebugString} API call.
20754 @kindex set debugexec
20755 @item set debugexec
20756 This boolean value adds debug output concerning execute events
20757 (such as resume thread) seen by the debugger.
20759 @kindex set debugexceptions
20760 @item set debugexceptions
20761 This boolean value adds debug output concerning exceptions in the
20762 debuggee seen by the debugger.
20764 @kindex set debugmemory
20765 @item set debugmemory
20766 This boolean value adds debug output concerning debuggee memory reads
20767 and writes by the debugger.
20771 This boolean values specifies whether the debuggee is called
20772 via a shell or directly (default value is on).
20776 Displays if the debuggee will be started with a shell.
20781 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
20784 @node Non-debug DLL Symbols
20785 @subsubsection Support for DLLs without Debugging Symbols
20786 @cindex DLLs with no debugging symbols
20787 @cindex Minimal symbols and DLLs
20789 Very often on windows, some of the DLLs that your program relies on do
20790 not include symbolic debugging information (for example,
20791 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
20792 symbols in a DLL, it relies on the minimal amount of symbolic
20793 information contained in the DLL's export table. This section
20794 describes working with such symbols, known internally to @value{GDBN} as
20795 ``minimal symbols''.
20797 Note that before the debugged program has started execution, no DLLs
20798 will have been loaded. The easiest way around this problem is simply to
20799 start the program --- either by setting a breakpoint or letting the
20800 program run once to completion.
20802 @subsubsection DLL Name Prefixes
20804 In keeping with the naming conventions used by the Microsoft debugging
20805 tools, DLL export symbols are made available with a prefix based on the
20806 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
20807 also entered into the symbol table, so @code{CreateFileA} is often
20808 sufficient. In some cases there will be name clashes within a program
20809 (particularly if the executable itself includes full debugging symbols)
20810 necessitating the use of the fully qualified name when referring to the
20811 contents of the DLL. Use single-quotes around the name to avoid the
20812 exclamation mark (``!'') being interpreted as a language operator.
20814 Note that the internal name of the DLL may be all upper-case, even
20815 though the file name of the DLL is lower-case, or vice-versa. Since
20816 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
20817 some confusion. If in doubt, try the @code{info functions} and
20818 @code{info variables} commands or even @code{maint print msymbols}
20819 (@pxref{Symbols}). Here's an example:
20822 (@value{GDBP}) info function CreateFileA
20823 All functions matching regular expression "CreateFileA":
20825 Non-debugging symbols:
20826 0x77e885f4 CreateFileA
20827 0x77e885f4 KERNEL32!CreateFileA
20831 (@value{GDBP}) info function !
20832 All functions matching regular expression "!":
20834 Non-debugging symbols:
20835 0x6100114c cygwin1!__assert
20836 0x61004034 cygwin1!_dll_crt0@@0
20837 0x61004240 cygwin1!dll_crt0(per_process *)
20841 @subsubsection Working with Minimal Symbols
20843 Symbols extracted from a DLL's export table do not contain very much
20844 type information. All that @value{GDBN} can do is guess whether a symbol
20845 refers to a function or variable depending on the linker section that
20846 contains the symbol. Also note that the actual contents of the memory
20847 contained in a DLL are not available unless the program is running. This
20848 means that you cannot examine the contents of a variable or disassemble
20849 a function within a DLL without a running program.
20851 Variables are generally treated as pointers and dereferenced
20852 automatically. For this reason, it is often necessary to prefix a
20853 variable name with the address-of operator (``&'') and provide explicit
20854 type information in the command. Here's an example of the type of
20858 (@value{GDBP}) print 'cygwin1!__argv'
20863 (@value{GDBP}) x 'cygwin1!__argv'
20864 0x10021610: "\230y\""
20867 And two possible solutions:
20870 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20871 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20875 (@value{GDBP}) x/2x &'cygwin1!__argv'
20876 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20877 (@value{GDBP}) x/x 0x10021608
20878 0x10021608: 0x0022fd98
20879 (@value{GDBP}) x/s 0x0022fd98
20880 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20883 Setting a break point within a DLL is possible even before the program
20884 starts execution. However, under these circumstances, @value{GDBN} can't
20885 examine the initial instructions of the function in order to skip the
20886 function's frame set-up code. You can work around this by using ``*&''
20887 to set the breakpoint at a raw memory address:
20890 (@value{GDBP}) break *&'python22!PyOS_Readline'
20891 Breakpoint 1 at 0x1e04eff0
20894 The author of these extensions is not entirely convinced that setting a
20895 break point within a shared DLL like @file{kernel32.dll} is completely
20899 @subsection Commands Specific to @sc{gnu} Hurd Systems
20900 @cindex @sc{gnu} Hurd debugging
20902 This subsection describes @value{GDBN} commands specific to the
20903 @sc{gnu} Hurd native debugging.
20908 @kindex set signals@r{, Hurd command}
20909 @kindex set sigs@r{, Hurd command}
20910 This command toggles the state of inferior signal interception by
20911 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20912 affected by this command. @code{sigs} is a shorthand alias for
20917 @kindex show signals@r{, Hurd command}
20918 @kindex show sigs@r{, Hurd command}
20919 Show the current state of intercepting inferior's signals.
20921 @item set signal-thread
20922 @itemx set sigthread
20923 @kindex set signal-thread
20924 @kindex set sigthread
20925 This command tells @value{GDBN} which thread is the @code{libc} signal
20926 thread. That thread is run when a signal is delivered to a running
20927 process. @code{set sigthread} is the shorthand alias of @code{set
20930 @item show signal-thread
20931 @itemx show sigthread
20932 @kindex show signal-thread
20933 @kindex show sigthread
20934 These two commands show which thread will run when the inferior is
20935 delivered a signal.
20938 @kindex set stopped@r{, Hurd command}
20939 This commands tells @value{GDBN} that the inferior process is stopped,
20940 as with the @code{SIGSTOP} signal. The stopped process can be
20941 continued by delivering a signal to it.
20944 @kindex show stopped@r{, Hurd command}
20945 This command shows whether @value{GDBN} thinks the debuggee is
20948 @item set exceptions
20949 @kindex set exceptions@r{, Hurd command}
20950 Use this command to turn off trapping of exceptions in the inferior.
20951 When exception trapping is off, neither breakpoints nor
20952 single-stepping will work. To restore the default, set exception
20955 @item show exceptions
20956 @kindex show exceptions@r{, Hurd command}
20957 Show the current state of trapping exceptions in the inferior.
20959 @item set task pause
20960 @kindex set task@r{, Hurd commands}
20961 @cindex task attributes (@sc{gnu} Hurd)
20962 @cindex pause current task (@sc{gnu} Hurd)
20963 This command toggles task suspension when @value{GDBN} has control.
20964 Setting it to on takes effect immediately, and the task is suspended
20965 whenever @value{GDBN} gets control. Setting it to off will take
20966 effect the next time the inferior is continued. If this option is set
20967 to off, you can use @code{set thread default pause on} or @code{set
20968 thread pause on} (see below) to pause individual threads.
20970 @item show task pause
20971 @kindex show task@r{, Hurd commands}
20972 Show the current state of task suspension.
20974 @item set task detach-suspend-count
20975 @cindex task suspend count
20976 @cindex detach from task, @sc{gnu} Hurd
20977 This command sets the suspend count the task will be left with when
20978 @value{GDBN} detaches from it.
20980 @item show task detach-suspend-count
20981 Show the suspend count the task will be left with when detaching.
20983 @item set task exception-port
20984 @itemx set task excp
20985 @cindex task exception port, @sc{gnu} Hurd
20986 This command sets the task exception port to which @value{GDBN} will
20987 forward exceptions. The argument should be the value of the @dfn{send
20988 rights} of the task. @code{set task excp} is a shorthand alias.
20990 @item set noninvasive
20991 @cindex noninvasive task options
20992 This command switches @value{GDBN} to a mode that is the least
20993 invasive as far as interfering with the inferior is concerned. This
20994 is the same as using @code{set task pause}, @code{set exceptions}, and
20995 @code{set signals} to values opposite to the defaults.
20997 @item info send-rights
20998 @itemx info receive-rights
20999 @itemx info port-rights
21000 @itemx info port-sets
21001 @itemx info dead-names
21004 @cindex send rights, @sc{gnu} Hurd
21005 @cindex receive rights, @sc{gnu} Hurd
21006 @cindex port rights, @sc{gnu} Hurd
21007 @cindex port sets, @sc{gnu} Hurd
21008 @cindex dead names, @sc{gnu} Hurd
21009 These commands display information about, respectively, send rights,
21010 receive rights, port rights, port sets, and dead names of a task.
21011 There are also shorthand aliases: @code{info ports} for @code{info
21012 port-rights} and @code{info psets} for @code{info port-sets}.
21014 @item set thread pause
21015 @kindex set thread@r{, Hurd command}
21016 @cindex thread properties, @sc{gnu} Hurd
21017 @cindex pause current thread (@sc{gnu} Hurd)
21018 This command toggles current thread suspension when @value{GDBN} has
21019 control. Setting it to on takes effect immediately, and the current
21020 thread is suspended whenever @value{GDBN} gets control. Setting it to
21021 off will take effect the next time the inferior is continued.
21022 Normally, this command has no effect, since when @value{GDBN} has
21023 control, the whole task is suspended. However, if you used @code{set
21024 task pause off} (see above), this command comes in handy to suspend
21025 only the current thread.
21027 @item show thread pause
21028 @kindex show thread@r{, Hurd command}
21029 This command shows the state of current thread suspension.
21031 @item set thread run
21032 This command sets whether the current thread is allowed to run.
21034 @item show thread run
21035 Show whether the current thread is allowed to run.
21037 @item set thread detach-suspend-count
21038 @cindex thread suspend count, @sc{gnu} Hurd
21039 @cindex detach from thread, @sc{gnu} Hurd
21040 This command sets the suspend count @value{GDBN} will leave on a
21041 thread when detaching. This number is relative to the suspend count
21042 found by @value{GDBN} when it notices the thread; use @code{set thread
21043 takeover-suspend-count} to force it to an absolute value.
21045 @item show thread detach-suspend-count
21046 Show the suspend count @value{GDBN} will leave on the thread when
21049 @item set thread exception-port
21050 @itemx set thread excp
21051 Set the thread exception port to which to forward exceptions. This
21052 overrides the port set by @code{set task exception-port} (see above).
21053 @code{set thread excp} is the shorthand alias.
21055 @item set thread takeover-suspend-count
21056 Normally, @value{GDBN}'s thread suspend counts are relative to the
21057 value @value{GDBN} finds when it notices each thread. This command
21058 changes the suspend counts to be absolute instead.
21060 @item set thread default
21061 @itemx show thread default
21062 @cindex thread default settings, @sc{gnu} Hurd
21063 Each of the above @code{set thread} commands has a @code{set thread
21064 default} counterpart (e.g., @code{set thread default pause}, @code{set
21065 thread default exception-port}, etc.). The @code{thread default}
21066 variety of commands sets the default thread properties for all
21067 threads; you can then change the properties of individual threads with
21068 the non-default commands.
21075 @value{GDBN} provides the following commands specific to the Darwin target:
21078 @item set debug darwin @var{num}
21079 @kindex set debug darwin
21080 When set to a non zero value, enables debugging messages specific to
21081 the Darwin support. Higher values produce more verbose output.
21083 @item show debug darwin
21084 @kindex show debug darwin
21085 Show the current state of Darwin messages.
21087 @item set debug mach-o @var{num}
21088 @kindex set debug mach-o
21089 When set to a non zero value, enables debugging messages while
21090 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21091 file format used on Darwin for object and executable files.) Higher
21092 values produce more verbose output. This is a command to diagnose
21093 problems internal to @value{GDBN} and should not be needed in normal
21096 @item show debug mach-o
21097 @kindex show debug mach-o
21098 Show the current state of Mach-O file messages.
21100 @item set mach-exceptions on
21101 @itemx set mach-exceptions off
21102 @kindex set mach-exceptions
21103 On Darwin, faults are first reported as a Mach exception and are then
21104 mapped to a Posix signal. Use this command to turn on trapping of
21105 Mach exceptions in the inferior. This might be sometimes useful to
21106 better understand the cause of a fault. The default is off.
21108 @item show mach-exceptions
21109 @kindex show mach-exceptions
21110 Show the current state of exceptions trapping.
21115 @section Embedded Operating Systems
21117 This section describes configurations involving the debugging of
21118 embedded operating systems that are available for several different
21121 @value{GDBN} includes the ability to debug programs running on
21122 various real-time operating systems.
21124 @node Embedded Processors
21125 @section Embedded Processors
21127 This section goes into details specific to particular embedded
21130 @cindex send command to simulator
21131 Whenever a specific embedded processor has a simulator, @value{GDBN}
21132 allows to send an arbitrary command to the simulator.
21135 @item sim @var{command}
21136 @kindex sim@r{, a command}
21137 Send an arbitrary @var{command} string to the simulator. Consult the
21138 documentation for the specific simulator in use for information about
21139 acceptable commands.
21145 * M32R/D:: Renesas M32R/D
21146 * M68K:: Motorola M68K
21147 * MicroBlaze:: Xilinx MicroBlaze
21148 * MIPS Embedded:: MIPS Embedded
21149 * PowerPC Embedded:: PowerPC Embedded
21150 * PA:: HP PA Embedded
21151 * Sparclet:: Tsqware Sparclet
21152 * Sparclite:: Fujitsu Sparclite
21153 * Z8000:: Zilog Z8000
21156 * Super-H:: Renesas Super-H
21165 @item target rdi @var{dev}
21166 ARM Angel monitor, via RDI library interface to ADP protocol. You may
21167 use this target to communicate with both boards running the Angel
21168 monitor, or with the EmbeddedICE JTAG debug device.
21171 @item target rdp @var{dev}
21176 @value{GDBN} provides the following ARM-specific commands:
21179 @item set arm disassembler
21181 This commands selects from a list of disassembly styles. The
21182 @code{"std"} style is the standard style.
21184 @item show arm disassembler
21186 Show the current disassembly style.
21188 @item set arm apcs32
21189 @cindex ARM 32-bit mode
21190 This command toggles ARM operation mode between 32-bit and 26-bit.
21192 @item show arm apcs32
21193 Display the current usage of the ARM 32-bit mode.
21195 @item set arm fpu @var{fputype}
21196 This command sets the ARM floating-point unit (FPU) type. The
21197 argument @var{fputype} can be one of these:
21201 Determine the FPU type by querying the OS ABI.
21203 Software FPU, with mixed-endian doubles on little-endian ARM
21206 GCC-compiled FPA co-processor.
21208 Software FPU with pure-endian doubles.
21214 Show the current type of the FPU.
21217 This command forces @value{GDBN} to use the specified ABI.
21220 Show the currently used ABI.
21222 @item set arm fallback-mode (arm|thumb|auto)
21223 @value{GDBN} uses the symbol table, when available, to determine
21224 whether instructions are ARM or Thumb. This command controls
21225 @value{GDBN}'s default behavior when the symbol table is not
21226 available. The default is @samp{auto}, which causes @value{GDBN} to
21227 use the current execution mode (from the @code{T} bit in the @code{CPSR}
21230 @item show arm fallback-mode
21231 Show the current fallback instruction mode.
21233 @item set arm force-mode (arm|thumb|auto)
21234 This command overrides use of the symbol table to determine whether
21235 instructions are ARM or Thumb. The default is @samp{auto}, which
21236 causes @value{GDBN} to use the symbol table and then the setting
21237 of @samp{set arm fallback-mode}.
21239 @item show arm force-mode
21240 Show the current forced instruction mode.
21242 @item set debug arm
21243 Toggle whether to display ARM-specific debugging messages from the ARM
21244 target support subsystem.
21246 @item show debug arm
21247 Show whether ARM-specific debugging messages are enabled.
21250 The following commands are available when an ARM target is debugged
21251 using the RDI interface:
21254 @item rdilogfile @r{[}@var{file}@r{]}
21256 @cindex ADP (Angel Debugger Protocol) logging
21257 Set the filename for the ADP (Angel Debugger Protocol) packet log.
21258 With an argument, sets the log file to the specified @var{file}. With
21259 no argument, show the current log file name. The default log file is
21262 @item rdilogenable @r{[}@var{arg}@r{]}
21263 @kindex rdilogenable
21264 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
21265 enables logging, with an argument 0 or @code{"no"} disables it. With
21266 no arguments displays the current setting. When logging is enabled,
21267 ADP packets exchanged between @value{GDBN} and the RDI target device
21268 are logged to a file.
21270 @item set rdiromatzero
21271 @kindex set rdiromatzero
21272 @cindex ROM at zero address, RDI
21273 Tell @value{GDBN} whether the target has ROM at address 0. If on,
21274 vector catching is disabled, so that zero address can be used. If off
21275 (the default), vector catching is enabled. For this command to take
21276 effect, it needs to be invoked prior to the @code{target rdi} command.
21278 @item show rdiromatzero
21279 @kindex show rdiromatzero
21280 Show the current setting of ROM at zero address.
21282 @item set rdiheartbeat
21283 @kindex set rdiheartbeat
21284 @cindex RDI heartbeat
21285 Enable or disable RDI heartbeat packets. It is not recommended to
21286 turn on this option, since it confuses ARM and EPI JTAG interface, as
21287 well as the Angel monitor.
21289 @item show rdiheartbeat
21290 @kindex show rdiheartbeat
21291 Show the setting of RDI heartbeat packets.
21295 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21296 The @value{GDBN} ARM simulator accepts the following optional arguments.
21299 @item --swi-support=@var{type}
21300 Tell the simulator which SWI interfaces to support. The argument
21301 @var{type} may be a comma separated list of the following values.
21302 The default value is @code{all}.
21315 @subsection Renesas M32R/D and M32R/SDI
21318 @kindex target m32r
21319 @item target m32r @var{dev}
21320 Renesas M32R/D ROM monitor.
21322 @kindex target m32rsdi
21323 @item target m32rsdi @var{dev}
21324 Renesas M32R SDI server, connected via parallel port to the board.
21327 The following @value{GDBN} commands are specific to the M32R monitor:
21330 @item set download-path @var{path}
21331 @kindex set download-path
21332 @cindex find downloadable @sc{srec} files (M32R)
21333 Set the default path for finding downloadable @sc{srec} files.
21335 @item show download-path
21336 @kindex show download-path
21337 Show the default path for downloadable @sc{srec} files.
21339 @item set board-address @var{addr}
21340 @kindex set board-address
21341 @cindex M32-EVA target board address
21342 Set the IP address for the M32R-EVA target board.
21344 @item show board-address
21345 @kindex show board-address
21346 Show the current IP address of the target board.
21348 @item set server-address @var{addr}
21349 @kindex set server-address
21350 @cindex download server address (M32R)
21351 Set the IP address for the download server, which is the @value{GDBN}'s
21354 @item show server-address
21355 @kindex show server-address
21356 Display the IP address of the download server.
21358 @item upload @r{[}@var{file}@r{]}
21359 @kindex upload@r{, M32R}
21360 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
21361 upload capability. If no @var{file} argument is given, the current
21362 executable file is uploaded.
21364 @item tload @r{[}@var{file}@r{]}
21365 @kindex tload@r{, M32R}
21366 Test the @code{upload} command.
21369 The following commands are available for M32R/SDI:
21374 @cindex reset SDI connection, M32R
21375 This command resets the SDI connection.
21379 This command shows the SDI connection status.
21382 @kindex debug_chaos
21383 @cindex M32R/Chaos debugging
21384 Instructs the remote that M32R/Chaos debugging is to be used.
21386 @item use_debug_dma
21387 @kindex use_debug_dma
21388 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21391 @kindex use_mon_code
21392 Instructs the remote to use the MON_CODE method of accessing memory.
21395 @kindex use_ib_break
21396 Instructs the remote to set breakpoints by IB break.
21398 @item use_dbt_break
21399 @kindex use_dbt_break
21400 Instructs the remote to set breakpoints by DBT.
21406 The Motorola m68k configuration includes ColdFire support, and a
21407 target command for the following ROM monitor.
21411 @kindex target dbug
21412 @item target dbug @var{dev}
21413 dBUG ROM monitor for Motorola ColdFire.
21418 @subsection MicroBlaze
21419 @cindex Xilinx MicroBlaze
21420 @cindex XMD, Xilinx Microprocessor Debugger
21422 The MicroBlaze is a soft-core processor supported on various Xilinx
21423 FPGAs, such as Spartan or Virtex series. Boards with these processors
21424 usually have JTAG ports which connect to a host system running the Xilinx
21425 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21426 This host system is used to download the configuration bitstream to
21427 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21428 communicates with the target board using the JTAG interface and
21429 presents a @code{gdbserver} interface to the board. By default
21430 @code{xmd} uses port @code{1234}. (While it is possible to change
21431 this default port, it requires the use of undocumented @code{xmd}
21432 commands. Contact Xilinx support if you need to do this.)
21434 Use these GDB commands to connect to the MicroBlaze target processor.
21437 @item target remote :1234
21438 Use this command to connect to the target if you are running @value{GDBN}
21439 on the same system as @code{xmd}.
21441 @item target remote @var{xmd-host}:1234
21442 Use this command to connect to the target if it is connected to @code{xmd}
21443 running on a different system named @var{xmd-host}.
21446 Use this command to download a program to the MicroBlaze target.
21448 @item set debug microblaze @var{n}
21449 Enable MicroBlaze-specific debugging messages if non-zero.
21451 @item show debug microblaze @var{n}
21452 Show MicroBlaze-specific debugging level.
21455 @node MIPS Embedded
21456 @subsection @acronym{MIPS} Embedded
21458 @cindex @acronym{MIPS} boards
21459 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21460 @acronym{MIPS} board attached to a serial line. This is available when
21461 you configure @value{GDBN} with @samp{--target=mips-elf}.
21464 Use these @value{GDBN} commands to specify the connection to your target board:
21467 @item target mips @var{port}
21468 @kindex target mips @var{port}
21469 To run a program on the board, start up @code{@value{GDBP}} with the
21470 name of your program as the argument. To connect to the board, use the
21471 command @samp{target mips @var{port}}, where @var{port} is the name of
21472 the serial port connected to the board. If the program has not already
21473 been downloaded to the board, you may use the @code{load} command to
21474 download it. You can then use all the usual @value{GDBN} commands.
21476 For example, this sequence connects to the target board through a serial
21477 port, and loads and runs a program called @var{prog} through the
21481 host$ @value{GDBP} @var{prog}
21482 @value{GDBN} is free software and @dots{}
21483 (@value{GDBP}) target mips /dev/ttyb
21484 (@value{GDBP}) load @var{prog}
21488 @item target mips @var{hostname}:@var{portnumber}
21489 On some @value{GDBN} host configurations, you can specify a TCP
21490 connection (for instance, to a serial line managed by a terminal
21491 concentrator) instead of a serial port, using the syntax
21492 @samp{@var{hostname}:@var{portnumber}}.
21494 @item target pmon @var{port}
21495 @kindex target pmon @var{port}
21498 @item target ddb @var{port}
21499 @kindex target ddb @var{port}
21500 NEC's DDB variant of PMON for Vr4300.
21502 @item target lsi @var{port}
21503 @kindex target lsi @var{port}
21504 LSI variant of PMON.
21506 @kindex target r3900
21507 @item target r3900 @var{dev}
21508 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
21510 @kindex target array
21511 @item target array @var{dev}
21512 Array Tech LSI33K RAID controller board.
21518 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21521 @item set mipsfpu double
21522 @itemx set mipsfpu single
21523 @itemx set mipsfpu none
21524 @itemx set mipsfpu auto
21525 @itemx show mipsfpu
21526 @kindex set mipsfpu
21527 @kindex show mipsfpu
21528 @cindex @acronym{MIPS} remote floating point
21529 @cindex floating point, @acronym{MIPS} remote
21530 If your target board does not support the @acronym{MIPS} floating point
21531 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21532 need this, you may wish to put the command in your @value{GDBN} init
21533 file). This tells @value{GDBN} how to find the return value of
21534 functions which return floating point values. It also allows
21535 @value{GDBN} to avoid saving the floating point registers when calling
21536 functions on the board. If you are using a floating point coprocessor
21537 with only single precision floating point support, as on the @sc{r4650}
21538 processor, use the command @samp{set mipsfpu single}. The default
21539 double precision floating point coprocessor may be selected using
21540 @samp{set mipsfpu double}.
21542 In previous versions the only choices were double precision or no
21543 floating point, so @samp{set mipsfpu on} will select double precision
21544 and @samp{set mipsfpu off} will select no floating point.
21546 As usual, you can inquire about the @code{mipsfpu} variable with
21547 @samp{show mipsfpu}.
21549 @item set timeout @var{seconds}
21550 @itemx set retransmit-timeout @var{seconds}
21551 @itemx show timeout
21552 @itemx show retransmit-timeout
21553 @cindex @code{timeout}, @acronym{MIPS} protocol
21554 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21555 @kindex set timeout
21556 @kindex show timeout
21557 @kindex set retransmit-timeout
21558 @kindex show retransmit-timeout
21559 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21560 remote protocol, with the @code{set timeout @var{seconds}} command. The
21561 default is 5 seconds. Similarly, you can control the timeout used while
21562 waiting for an acknowledgment of a packet with the @code{set
21563 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21564 You can inspect both values with @code{show timeout} and @code{show
21565 retransmit-timeout}. (These commands are @emph{only} available when
21566 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21568 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21569 is waiting for your program to stop. In that case, @value{GDBN} waits
21570 forever because it has no way of knowing how long the program is going
21571 to run before stopping.
21573 @item set syn-garbage-limit @var{num}
21574 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21575 @cindex synchronize with remote @acronym{MIPS} target
21576 Limit the maximum number of characters @value{GDBN} should ignore when
21577 it tries to synchronize with the remote target. The default is 10
21578 characters. Setting the limit to -1 means there's no limit.
21580 @item show syn-garbage-limit
21581 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21582 Show the current limit on the number of characters to ignore when
21583 trying to synchronize with the remote system.
21585 @item set monitor-prompt @var{prompt}
21586 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21587 @cindex remote monitor prompt
21588 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21589 remote monitor. The default depends on the target:
21599 @item show monitor-prompt
21600 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21601 Show the current strings @value{GDBN} expects as the prompt from the
21604 @item set monitor-warnings
21605 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21606 Enable or disable monitor warnings about hardware breakpoints. This
21607 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21608 display warning messages whose codes are returned by the @code{lsi}
21609 PMON monitor for breakpoint commands.
21611 @item show monitor-warnings
21612 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21613 Show the current setting of printing monitor warnings.
21615 @item pmon @var{command}
21616 @kindex pmon@r{, @acronym{MIPS} remote}
21617 @cindex send PMON command
21618 This command allows sending an arbitrary @var{command} string to the
21619 monitor. The monitor must be in debug mode for this to work.
21622 @node PowerPC Embedded
21623 @subsection PowerPC Embedded
21625 @cindex DVC register
21626 @value{GDBN} supports using the DVC (Data Value Compare) register to
21627 implement in hardware simple hardware watchpoint conditions of the form:
21630 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21631 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
21634 The DVC register will be automatically used when @value{GDBN} detects
21635 such pattern in a condition expression, and the created watchpoint uses one
21636 debug register (either the @code{exact-watchpoints} option is on and the
21637 variable is scalar, or the variable has a length of one byte). This feature
21638 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
21641 When running on PowerPC embedded processors, @value{GDBN} automatically uses
21642 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
21643 in which case watchpoints using only one debug register are created when
21644 watching variables of scalar types.
21646 You can create an artificial array to watch an arbitrary memory
21647 region using one of the following commands (@pxref{Expressions}):
21650 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
21651 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
21654 PowerPC embedded processors support masked watchpoints. See the discussion
21655 about the @code{mask} argument in @ref{Set Watchpoints}.
21657 @cindex ranged breakpoint
21658 PowerPC embedded processors support hardware accelerated
21659 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
21660 the inferior whenever it executes an instruction at any address within
21661 the range it specifies. To set a ranged breakpoint in @value{GDBN},
21662 use the @code{break-range} command.
21664 @value{GDBN} provides the following PowerPC-specific commands:
21667 @kindex break-range
21668 @item break-range @var{start-location}, @var{end-location}
21669 Set a breakpoint for an address range given by
21670 @var{start-location} and @var{end-location}, which can specify a function name,
21671 a line number, an offset of lines from the current line or from the start
21672 location, or an address of an instruction (see @ref{Specify Location},
21673 for a list of all the possible ways to specify a @var{location}.)
21674 The breakpoint will stop execution of the inferior whenever it
21675 executes an instruction at any address within the specified range,
21676 (including @var{start-location} and @var{end-location}.)
21678 @kindex set powerpc
21679 @item set powerpc soft-float
21680 @itemx show powerpc soft-float
21681 Force @value{GDBN} to use (or not use) a software floating point calling
21682 convention. By default, @value{GDBN} selects the calling convention based
21683 on the selected architecture and the provided executable file.
21685 @item set powerpc vector-abi
21686 @itemx show powerpc vector-abi
21687 Force @value{GDBN} to use the specified calling convention for vector
21688 arguments and return values. The valid options are @samp{auto};
21689 @samp{generic}, to avoid vector registers even if they are present;
21690 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
21691 registers. By default, @value{GDBN} selects the calling convention
21692 based on the selected architecture and the provided executable file.
21694 @item set powerpc exact-watchpoints
21695 @itemx show powerpc exact-watchpoints
21696 Allow @value{GDBN} to use only one debug register when watching a variable
21697 of scalar type, thus assuming that the variable is accessed through the
21698 address of its first byte.
21700 @kindex target dink32
21701 @item target dink32 @var{dev}
21702 DINK32 ROM monitor.
21704 @kindex target ppcbug
21705 @item target ppcbug @var{dev}
21706 @kindex target ppcbug1
21707 @item target ppcbug1 @var{dev}
21708 PPCBUG ROM monitor for PowerPC.
21711 @item target sds @var{dev}
21712 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21715 @cindex SDS protocol
21716 The following commands specific to the SDS protocol are supported
21720 @item set sdstimeout @var{nsec}
21721 @kindex set sdstimeout
21722 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21723 default is 2 seconds.
21725 @item show sdstimeout
21726 @kindex show sdstimeout
21727 Show the current value of the SDS timeout.
21729 @item sds @var{command}
21730 @kindex sds@r{, a command}
21731 Send the specified @var{command} string to the SDS monitor.
21736 @subsection HP PA Embedded
21740 @kindex target op50n
21741 @item target op50n @var{dev}
21742 OP50N monitor, running on an OKI HPPA board.
21744 @kindex target w89k
21745 @item target w89k @var{dev}
21746 W89K monitor, running on a Winbond HPPA board.
21751 @subsection Tsqware Sparclet
21755 @value{GDBN} enables developers to debug tasks running on
21756 Sparclet targets from a Unix host.
21757 @value{GDBN} uses code that runs on
21758 both the Unix host and on the Sparclet target. The program
21759 @code{@value{GDBP}} is installed and executed on the Unix host.
21762 @item remotetimeout @var{args}
21763 @kindex remotetimeout
21764 @value{GDBN} supports the option @code{remotetimeout}.
21765 This option is set by the user, and @var{args} represents the number of
21766 seconds @value{GDBN} waits for responses.
21769 @cindex compiling, on Sparclet
21770 When compiling for debugging, include the options @samp{-g} to get debug
21771 information and @samp{-Ttext} to relocate the program to where you wish to
21772 load it on the target. You may also want to add the options @samp{-n} or
21773 @samp{-N} in order to reduce the size of the sections. Example:
21776 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21779 You can use @code{objdump} to verify that the addresses are what you intended:
21782 sparclet-aout-objdump --headers --syms prog
21785 @cindex running, on Sparclet
21787 your Unix execution search path to find @value{GDBN}, you are ready to
21788 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21789 (or @code{sparclet-aout-gdb}, depending on your installation).
21791 @value{GDBN} comes up showing the prompt:
21798 * Sparclet File:: Setting the file to debug
21799 * Sparclet Connection:: Connecting to Sparclet
21800 * Sparclet Download:: Sparclet download
21801 * Sparclet Execution:: Running and debugging
21804 @node Sparclet File
21805 @subsubsection Setting File to Debug
21807 The @value{GDBN} command @code{file} lets you choose with program to debug.
21810 (gdbslet) file prog
21814 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21815 @value{GDBN} locates
21816 the file by searching the directories listed in the command search
21818 If the file was compiled with debug information (option @samp{-g}), source
21819 files will be searched as well.
21820 @value{GDBN} locates
21821 the source files by searching the directories listed in the directory search
21822 path (@pxref{Environment, ,Your Program's Environment}).
21824 to find a file, it displays a message such as:
21827 prog: No such file or directory.
21830 When this happens, add the appropriate directories to the search paths with
21831 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21832 @code{target} command again.
21834 @node Sparclet Connection
21835 @subsubsection Connecting to Sparclet
21837 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21838 To connect to a target on serial port ``@code{ttya}'', type:
21841 (gdbslet) target sparclet /dev/ttya
21842 Remote target sparclet connected to /dev/ttya
21843 main () at ../prog.c:3
21847 @value{GDBN} displays messages like these:
21853 @node Sparclet Download
21854 @subsubsection Sparclet Download
21856 @cindex download to Sparclet
21857 Once connected to the Sparclet target,
21858 you can use the @value{GDBN}
21859 @code{load} command to download the file from the host to the target.
21860 The file name and load offset should be given as arguments to the @code{load}
21862 Since the file format is aout, the program must be loaded to the starting
21863 address. You can use @code{objdump} to find out what this value is. The load
21864 offset is an offset which is added to the VMA (virtual memory address)
21865 of each of the file's sections.
21866 For instance, if the program
21867 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21868 and bss at 0x12010170, in @value{GDBN}, type:
21871 (gdbslet) load prog 0x12010000
21872 Loading section .text, size 0xdb0 vma 0x12010000
21875 If the code is loaded at a different address then what the program was linked
21876 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21877 to tell @value{GDBN} where to map the symbol table.
21879 @node Sparclet Execution
21880 @subsubsection Running and Debugging
21882 @cindex running and debugging Sparclet programs
21883 You can now begin debugging the task using @value{GDBN}'s execution control
21884 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21885 manual for the list of commands.
21889 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21891 Starting program: prog
21892 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21893 3 char *symarg = 0;
21895 4 char *execarg = "hello!";
21900 @subsection Fujitsu Sparclite
21904 @kindex target sparclite
21905 @item target sparclite @var{dev}
21906 Fujitsu sparclite boards, used only for the purpose of loading.
21907 You must use an additional command to debug the program.
21908 For example: target remote @var{dev} using @value{GDBN} standard
21914 @subsection Zilog Z8000
21917 @cindex simulator, Z8000
21918 @cindex Zilog Z8000 simulator
21920 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21923 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21924 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21925 segmented variant). The simulator recognizes which architecture is
21926 appropriate by inspecting the object code.
21929 @item target sim @var{args}
21931 @kindex target sim@r{, with Z8000}
21932 Debug programs on a simulated CPU. If the simulator supports setup
21933 options, specify them via @var{args}.
21937 After specifying this target, you can debug programs for the simulated
21938 CPU in the same style as programs for your host computer; use the
21939 @code{file} command to load a new program image, the @code{run} command
21940 to run your program, and so on.
21942 As well as making available all the usual machine registers
21943 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21944 additional items of information as specially named registers:
21949 Counts clock-ticks in the simulator.
21952 Counts instructions run in the simulator.
21955 Execution time in 60ths of a second.
21959 You can refer to these values in @value{GDBN} expressions with the usual
21960 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21961 conditional breakpoint that suspends only after at least 5000
21962 simulated clock ticks.
21965 @subsection Atmel AVR
21968 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21969 following AVR-specific commands:
21972 @item info io_registers
21973 @kindex info io_registers@r{, AVR}
21974 @cindex I/O registers (Atmel AVR)
21975 This command displays information about the AVR I/O registers. For
21976 each register, @value{GDBN} prints its number and value.
21983 When configured for debugging CRIS, @value{GDBN} provides the
21984 following CRIS-specific commands:
21987 @item set cris-version @var{ver}
21988 @cindex CRIS version
21989 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21990 The CRIS version affects register names and sizes. This command is useful in
21991 case autodetection of the CRIS version fails.
21993 @item show cris-version
21994 Show the current CRIS version.
21996 @item set cris-dwarf2-cfi
21997 @cindex DWARF-2 CFI and CRIS
21998 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21999 Change to @samp{off} when using @code{gcc-cris} whose version is below
22002 @item show cris-dwarf2-cfi
22003 Show the current state of using DWARF-2 CFI.
22005 @item set cris-mode @var{mode}
22007 Set the current CRIS mode to @var{mode}. It should only be changed when
22008 debugging in guru mode, in which case it should be set to
22009 @samp{guru} (the default is @samp{normal}).
22011 @item show cris-mode
22012 Show the current CRIS mode.
22016 @subsection Renesas Super-H
22019 For the Renesas Super-H processor, @value{GDBN} provides these
22023 @item set sh calling-convention @var{convention}
22024 @kindex set sh calling-convention
22025 Set the calling-convention used when calling functions from @value{GDBN}.
22026 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22027 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22028 convention. If the DWARF-2 information of the called function specifies
22029 that the function follows the Renesas calling convention, the function
22030 is called using the Renesas calling convention. If the calling convention
22031 is set to @samp{renesas}, the Renesas calling convention is always used,
22032 regardless of the DWARF-2 information. This can be used to override the
22033 default of @samp{gcc} if debug information is missing, or the compiler
22034 does not emit the DWARF-2 calling convention entry for a function.
22036 @item show sh calling-convention
22037 @kindex show sh calling-convention
22038 Show the current calling convention setting.
22043 @node Architectures
22044 @section Architectures
22046 This section describes characteristics of architectures that affect
22047 all uses of @value{GDBN} with the architecture, both native and cross.
22054 * HPPA:: HP PA architecture
22055 * SPU:: Cell Broadband Engine SPU architecture
22061 @subsection AArch64
22062 @cindex AArch64 support
22064 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22065 following special commands:
22068 @item set debug aarch64
22069 @kindex set debug aarch64
22070 This command determines whether AArch64 architecture-specific debugging
22071 messages are to be displayed.
22073 @item show debug aarch64
22074 Show whether AArch64 debugging messages are displayed.
22079 @subsection x86 Architecture-specific Issues
22082 @item set struct-convention @var{mode}
22083 @kindex set struct-convention
22084 @cindex struct return convention
22085 @cindex struct/union returned in registers
22086 Set the convention used by the inferior to return @code{struct}s and
22087 @code{union}s from functions to @var{mode}. Possible values of
22088 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22089 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22090 are returned on the stack, while @code{"reg"} means that a
22091 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22092 be returned in a register.
22094 @item show struct-convention
22095 @kindex show struct-convention
22096 Show the current setting of the convention to return @code{struct}s
22100 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
22101 @cindex Intel(R) Memory Protection Extensions (MPX).
22103 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22104 @footnote{The register named with capital letters represent the architecture
22105 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22106 which are the lower bound and upper bound. Bounds are effective addresses or
22107 memory locations. The upper bounds are architecturally represented in 1's
22108 complement form. A bound having lower bound = 0, and upper bound = 0
22109 (1's complement of all bits set) will allow access to the entire address space.
22111 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22112 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22113 display the upper bound performing the complement of one operation on the
22114 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22115 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22116 can also be noted that the upper bounds are inclusive.
22118 As an example, assume that the register BND0 holds bounds for a pointer having
22119 access allowed for the range between 0x32 and 0x71. The values present on
22120 bnd0raw and bnd registers are presented as follows:
22123 bnd0raw = @{0x32, 0xffffffff8e@}
22124 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22127 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22128 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22129 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22130 Python, the display includes the memory size, in bits, accessible to
22136 See the following section.
22139 @subsection @acronym{MIPS}
22141 @cindex stack on Alpha
22142 @cindex stack on @acronym{MIPS}
22143 @cindex Alpha stack
22144 @cindex @acronym{MIPS} stack
22145 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22146 sometimes requires @value{GDBN} to search backward in the object code to
22147 find the beginning of a function.
22149 @cindex response time, @acronym{MIPS} debugging
22150 To improve response time (especially for embedded applications, where
22151 @value{GDBN} may be restricted to a slow serial line for this search)
22152 you may want to limit the size of this search, using one of these
22156 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22157 @item set heuristic-fence-post @var{limit}
22158 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22159 search for the beginning of a function. A value of @var{0} (the
22160 default) means there is no limit. However, except for @var{0}, the
22161 larger the limit the more bytes @code{heuristic-fence-post} must search
22162 and therefore the longer it takes to run. You should only need to use
22163 this command when debugging a stripped executable.
22165 @item show heuristic-fence-post
22166 Display the current limit.
22170 These commands are available @emph{only} when @value{GDBN} is configured
22171 for debugging programs on Alpha or @acronym{MIPS} processors.
22173 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22177 @item set mips abi @var{arg}
22178 @kindex set mips abi
22179 @cindex set ABI for @acronym{MIPS}
22180 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22181 values of @var{arg} are:
22185 The default ABI associated with the current binary (this is the
22195 @item show mips abi
22196 @kindex show mips abi
22197 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22199 @item set mips compression @var{arg}
22200 @kindex set mips compression
22201 @cindex code compression, @acronym{MIPS}
22202 Tell @value{GDBN} which @acronym{MIPS} compressed
22203 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22204 inferior. @value{GDBN} uses this for code disassembly and other
22205 internal interpretation purposes. This setting is only referred to
22206 when no executable has been associated with the debugging session or
22207 the executable does not provide information about the encoding it uses.
22208 Otherwise this setting is automatically updated from information
22209 provided by the executable.
22211 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22212 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22213 executables containing @acronym{MIPS16} code frequently are not
22214 identified as such.
22216 This setting is ``sticky''; that is, it retains its value across
22217 debugging sessions until reset either explicitly with this command or
22218 implicitly from an executable.
22220 The compiler and/or assembler typically add symbol table annotations to
22221 identify functions compiled for the @acronym{MIPS16} or
22222 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22223 are present, @value{GDBN} uses them in preference to the global
22224 compressed @acronym{ISA} encoding setting.
22226 @item show mips compression
22227 @kindex show mips compression
22228 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22229 @value{GDBN} to debug the inferior.
22232 @itemx show mipsfpu
22233 @xref{MIPS Embedded, set mipsfpu}.
22235 @item set mips mask-address @var{arg}
22236 @kindex set mips mask-address
22237 @cindex @acronym{MIPS} addresses, masking
22238 This command determines whether the most-significant 32 bits of 64-bit
22239 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22240 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22241 setting, which lets @value{GDBN} determine the correct value.
22243 @item show mips mask-address
22244 @kindex show mips mask-address
22245 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22248 @item set remote-mips64-transfers-32bit-regs
22249 @kindex set remote-mips64-transfers-32bit-regs
22250 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22251 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22252 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22253 and 64 bits for other registers, set this option to @samp{on}.
22255 @item show remote-mips64-transfers-32bit-regs
22256 @kindex show remote-mips64-transfers-32bit-regs
22257 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22259 @item set debug mips
22260 @kindex set debug mips
22261 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22262 target code in @value{GDBN}.
22264 @item show debug mips
22265 @kindex show debug mips
22266 Show the current setting of @acronym{MIPS} debugging messages.
22272 @cindex HPPA support
22274 When @value{GDBN} is debugging the HP PA architecture, it provides the
22275 following special commands:
22278 @item set debug hppa
22279 @kindex set debug hppa
22280 This command determines whether HPPA architecture-specific debugging
22281 messages are to be displayed.
22283 @item show debug hppa
22284 Show whether HPPA debugging messages are displayed.
22286 @item maint print unwind @var{address}
22287 @kindex maint print unwind@r{, HPPA}
22288 This command displays the contents of the unwind table entry at the
22289 given @var{address}.
22295 @subsection Cell Broadband Engine SPU architecture
22296 @cindex Cell Broadband Engine
22299 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22300 it provides the following special commands:
22303 @item info spu event
22305 Display SPU event facility status. Shows current event mask
22306 and pending event status.
22308 @item info spu signal
22309 Display SPU signal notification facility status. Shows pending
22310 signal-control word and signal notification mode of both signal
22311 notification channels.
22313 @item info spu mailbox
22314 Display SPU mailbox facility status. Shows all pending entries,
22315 in order of processing, in each of the SPU Write Outbound,
22316 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22319 Display MFC DMA status. Shows all pending commands in the MFC
22320 DMA queue. For each entry, opcode, tag, class IDs, effective
22321 and local store addresses and transfer size are shown.
22323 @item info spu proxydma
22324 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22325 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22326 and local store addresses and transfer size are shown.
22330 When @value{GDBN} is debugging a combined PowerPC/SPU application
22331 on the Cell Broadband Engine, it provides in addition the following
22335 @item set spu stop-on-load @var{arg}
22337 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22338 will give control to the user when a new SPE thread enters its @code{main}
22339 function. The default is @code{off}.
22341 @item show spu stop-on-load
22343 Show whether to stop for new SPE threads.
22345 @item set spu auto-flush-cache @var{arg}
22346 Set whether to automatically flush the software-managed cache. When set to
22347 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22348 cache to be flushed whenever SPE execution stops. This provides a consistent
22349 view of PowerPC memory that is accessed via the cache. If an application
22350 does not use the software-managed cache, this option has no effect.
22352 @item show spu auto-flush-cache
22353 Show whether to automatically flush the software-managed cache.
22358 @subsection PowerPC
22359 @cindex PowerPC architecture
22361 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22362 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22363 numbers stored in the floating point registers. These values must be stored
22364 in two consecutive registers, always starting at an even register like
22365 @code{f0} or @code{f2}.
22367 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22368 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22369 @code{f2} and @code{f3} for @code{$dl1} and so on.
22371 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22372 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22375 @subsection Nios II
22376 @cindex Nios II architecture
22378 When @value{GDBN} is debugging the Nios II architecture,
22379 it provides the following special commands:
22383 @item set debug nios2
22384 @kindex set debug nios2
22385 This command turns on and off debugging messages for the Nios II
22386 target code in @value{GDBN}.
22388 @item show debug nios2
22389 @kindex show debug nios2
22390 Show the current setting of Nios II debugging messages.
22393 @node Controlling GDB
22394 @chapter Controlling @value{GDBN}
22396 You can alter the way @value{GDBN} interacts with you by using the
22397 @code{set} command. For commands controlling how @value{GDBN} displays
22398 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22403 * Editing:: Command editing
22404 * Command History:: Command history
22405 * Screen Size:: Screen size
22406 * Numbers:: Numbers
22407 * ABI:: Configuring the current ABI
22408 * Auto-loading:: Automatically loading associated files
22409 * Messages/Warnings:: Optional warnings and messages
22410 * Debugging Output:: Optional messages about internal happenings
22411 * Other Misc Settings:: Other Miscellaneous Settings
22419 @value{GDBN} indicates its readiness to read a command by printing a string
22420 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22421 can change the prompt string with the @code{set prompt} command. For
22422 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22423 the prompt in one of the @value{GDBN} sessions so that you can always tell
22424 which one you are talking to.
22426 @emph{Note:} @code{set prompt} does not add a space for you after the
22427 prompt you set. This allows you to set a prompt which ends in a space
22428 or a prompt that does not.
22432 @item set prompt @var{newprompt}
22433 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22435 @kindex show prompt
22437 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22440 Versions of @value{GDBN} that ship with Python scripting enabled have
22441 prompt extensions. The commands for interacting with these extensions
22445 @kindex set extended-prompt
22446 @item set extended-prompt @var{prompt}
22447 Set an extended prompt that allows for substitutions.
22448 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22449 substitution. Any escape sequences specified as part of the prompt
22450 string are replaced with the corresponding strings each time the prompt
22456 set extended-prompt Current working directory: \w (gdb)
22459 Note that when an extended-prompt is set, it takes control of the
22460 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22462 @kindex show extended-prompt
22463 @item show extended-prompt
22464 Prints the extended prompt. Any escape sequences specified as part of
22465 the prompt string with @code{set extended-prompt}, are replaced with the
22466 corresponding strings each time the prompt is displayed.
22470 @section Command Editing
22472 @cindex command line editing
22474 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22475 @sc{gnu} library provides consistent behavior for programs which provide a
22476 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22477 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22478 substitution, and a storage and recall of command history across
22479 debugging sessions.
22481 You may control the behavior of command line editing in @value{GDBN} with the
22482 command @code{set}.
22485 @kindex set editing
22488 @itemx set editing on
22489 Enable command line editing (enabled by default).
22491 @item set editing off
22492 Disable command line editing.
22494 @kindex show editing
22496 Show whether command line editing is enabled.
22499 @ifset SYSTEM_READLINE
22500 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22502 @ifclear SYSTEM_READLINE
22503 @xref{Command Line Editing},
22505 for more details about the Readline
22506 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22507 encouraged to read that chapter.
22509 @node Command History
22510 @section Command History
22511 @cindex command history
22513 @value{GDBN} can keep track of the commands you type during your
22514 debugging sessions, so that you can be certain of precisely what
22515 happened. Use these commands to manage the @value{GDBN} command
22518 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22519 package, to provide the history facility.
22520 @ifset SYSTEM_READLINE
22521 @xref{Using History Interactively, , , history, GNU History Library},
22523 @ifclear SYSTEM_READLINE
22524 @xref{Using History Interactively},
22526 for the detailed description of the History library.
22528 To issue a command to @value{GDBN} without affecting certain aspects of
22529 the state which is seen by users, prefix it with @samp{server }
22530 (@pxref{Server Prefix}). This
22531 means that this command will not affect the command history, nor will it
22532 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22533 pressed on a line by itself.
22535 @cindex @code{server}, command prefix
22536 The server prefix does not affect the recording of values into the value
22537 history; to print a value without recording it into the value history,
22538 use the @code{output} command instead of the @code{print} command.
22540 Here is the description of @value{GDBN} commands related to command
22544 @cindex history substitution
22545 @cindex history file
22546 @kindex set history filename
22547 @cindex @env{GDBHISTFILE}, environment variable
22548 @item set history filename @var{fname}
22549 Set the name of the @value{GDBN} command history file to @var{fname}.
22550 This is the file where @value{GDBN} reads an initial command history
22551 list, and where it writes the command history from this session when it
22552 exits. You can access this list through history expansion or through
22553 the history command editing characters listed below. This file defaults
22554 to the value of the environment variable @code{GDBHISTFILE}, or to
22555 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22558 @cindex save command history
22559 @kindex set history save
22560 @item set history save
22561 @itemx set history save on
22562 Record command history in a file, whose name may be specified with the
22563 @code{set history filename} command. By default, this option is disabled.
22565 @item set history save off
22566 Stop recording command history in a file.
22568 @cindex history size
22569 @kindex set history size
22570 @cindex @env{HISTSIZE}, environment variable
22571 @item set history size @var{size}
22572 @itemx set history size unlimited
22573 Set the number of commands which @value{GDBN} keeps in its history list.
22574 This defaults to the value of the environment variable
22575 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
22576 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
22577 history list is unlimited.
22580 History expansion assigns special meaning to the character @kbd{!}.
22581 @ifset SYSTEM_READLINE
22582 @xref{Event Designators, , , history, GNU History Library},
22584 @ifclear SYSTEM_READLINE
22585 @xref{Event Designators},
22589 @cindex history expansion, turn on/off
22590 Since @kbd{!} is also the logical not operator in C, history expansion
22591 is off by default. If you decide to enable history expansion with the
22592 @code{set history expansion on} command, you may sometimes need to
22593 follow @kbd{!} (when it is used as logical not, in an expression) with
22594 a space or a tab to prevent it from being expanded. The readline
22595 history facilities do not attempt substitution on the strings
22596 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22598 The commands to control history expansion are:
22601 @item set history expansion on
22602 @itemx set history expansion
22603 @kindex set history expansion
22604 Enable history expansion. History expansion is off by default.
22606 @item set history expansion off
22607 Disable history expansion.
22610 @kindex show history
22612 @itemx show history filename
22613 @itemx show history save
22614 @itemx show history size
22615 @itemx show history expansion
22616 These commands display the state of the @value{GDBN} history parameters.
22617 @code{show history} by itself displays all four states.
22622 @kindex show commands
22623 @cindex show last commands
22624 @cindex display command history
22625 @item show commands
22626 Display the last ten commands in the command history.
22628 @item show commands @var{n}
22629 Print ten commands centered on command number @var{n}.
22631 @item show commands +
22632 Print ten commands just after the commands last printed.
22636 @section Screen Size
22637 @cindex size of screen
22638 @cindex screen size
22641 @cindex pauses in output
22643 Certain commands to @value{GDBN} may produce large amounts of
22644 information output to the screen. To help you read all of it,
22645 @value{GDBN} pauses and asks you for input at the end of each page of
22646 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22647 to discard the remaining output. Also, the screen width setting
22648 determines when to wrap lines of output. Depending on what is being
22649 printed, @value{GDBN} tries to break the line at a readable place,
22650 rather than simply letting it overflow onto the following line.
22652 Normally @value{GDBN} knows the size of the screen from the terminal
22653 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22654 together with the value of the @code{TERM} environment variable and the
22655 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22656 you can override it with the @code{set height} and @code{set
22663 @kindex show height
22664 @item set height @var{lpp}
22665 @itemx set height unlimited
22667 @itemx set width @var{cpl}
22668 @itemx set width unlimited
22670 These @code{set} commands specify a screen height of @var{lpp} lines and
22671 a screen width of @var{cpl} characters. The associated @code{show}
22672 commands display the current settings.
22674 If you specify a height of either @code{unlimited} or zero lines,
22675 @value{GDBN} does not pause during output no matter how long the
22676 output is. This is useful if output is to a file or to an editor
22679 Likewise, you can specify @samp{set width unlimited} or @samp{set
22680 width 0} to prevent @value{GDBN} from wrapping its output.
22682 @item set pagination on
22683 @itemx set pagination off
22684 @kindex set pagination
22685 Turn the output pagination on or off; the default is on. Turning
22686 pagination off is the alternative to @code{set height unlimited}. Note that
22687 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22688 Options, -batch}) also automatically disables pagination.
22690 @item show pagination
22691 @kindex show pagination
22692 Show the current pagination mode.
22697 @cindex number representation
22698 @cindex entering numbers
22700 You can always enter numbers in octal, decimal, or hexadecimal in
22701 @value{GDBN} by the usual conventions: octal numbers begin with
22702 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22703 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22704 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22705 10; likewise, the default display for numbers---when no particular
22706 format is specified---is base 10. You can change the default base for
22707 both input and output with the commands described below.
22710 @kindex set input-radix
22711 @item set input-radix @var{base}
22712 Set the default base for numeric input. Supported choices
22713 for @var{base} are decimal 8, 10, or 16. The base must itself be
22714 specified either unambiguously or using the current input radix; for
22718 set input-radix 012
22719 set input-radix 10.
22720 set input-radix 0xa
22724 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22725 leaves the input radix unchanged, no matter what it was, since
22726 @samp{10}, being without any leading or trailing signs of its base, is
22727 interpreted in the current radix. Thus, if the current radix is 16,
22728 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22731 @kindex set output-radix
22732 @item set output-radix @var{base}
22733 Set the default base for numeric display. Supported choices
22734 for @var{base} are decimal 8, 10, or 16. The base must itself be
22735 specified either unambiguously or using the current input radix.
22737 @kindex show input-radix
22738 @item show input-radix
22739 Display the current default base for numeric input.
22741 @kindex show output-radix
22742 @item show output-radix
22743 Display the current default base for numeric display.
22745 @item set radix @r{[}@var{base}@r{]}
22749 These commands set and show the default base for both input and output
22750 of numbers. @code{set radix} sets the radix of input and output to
22751 the same base; without an argument, it resets the radix back to its
22752 default value of 10.
22757 @section Configuring the Current ABI
22759 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22760 application automatically. However, sometimes you need to override its
22761 conclusions. Use these commands to manage @value{GDBN}'s view of the
22767 @cindex Newlib OS ABI and its influence on the longjmp handling
22769 One @value{GDBN} configuration can debug binaries for multiple operating
22770 system targets, either via remote debugging or native emulation.
22771 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22772 but you can override its conclusion using the @code{set osabi} command.
22773 One example where this is useful is in debugging of binaries which use
22774 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22775 not have the same identifying marks that the standard C library for your
22778 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22779 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22780 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22781 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22785 Show the OS ABI currently in use.
22788 With no argument, show the list of registered available OS ABI's.
22790 @item set osabi @var{abi}
22791 Set the current OS ABI to @var{abi}.
22794 @cindex float promotion
22796 Generally, the way that an argument of type @code{float} is passed to a
22797 function depends on whether the function is prototyped. For a prototyped
22798 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22799 according to the architecture's convention for @code{float}. For unprototyped
22800 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22801 @code{double} and then passed.
22803 Unfortunately, some forms of debug information do not reliably indicate whether
22804 a function is prototyped. If @value{GDBN} calls a function that is not marked
22805 as prototyped, it consults @kbd{set coerce-float-to-double}.
22808 @kindex set coerce-float-to-double
22809 @item set coerce-float-to-double
22810 @itemx set coerce-float-to-double on
22811 Arguments of type @code{float} will be promoted to @code{double} when passed
22812 to an unprototyped function. This is the default setting.
22814 @item set coerce-float-to-double off
22815 Arguments of type @code{float} will be passed directly to unprototyped
22818 @kindex show coerce-float-to-double
22819 @item show coerce-float-to-double
22820 Show the current setting of promoting @code{float} to @code{double}.
22824 @kindex show cp-abi
22825 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22826 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22827 used to build your application. @value{GDBN} only fully supports
22828 programs with a single C@t{++} ABI; if your program contains code using
22829 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22830 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22831 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22832 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22833 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22834 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22839 Show the C@t{++} ABI currently in use.
22842 With no argument, show the list of supported C@t{++} ABI's.
22844 @item set cp-abi @var{abi}
22845 @itemx set cp-abi auto
22846 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22850 @section Automatically loading associated files
22851 @cindex auto-loading
22853 @value{GDBN} sometimes reads files with commands and settings automatically,
22854 without being explicitly told so by the user. We call this feature
22855 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22856 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22857 results or introduce security risks (e.g., if the file comes from untrusted
22861 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22862 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22864 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22865 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22868 There are various kinds of files @value{GDBN} can automatically load.
22869 In addition to these files, @value{GDBN} supports auto-loading code written
22870 in various extension languages. @xref{Auto-loading extensions}.
22872 Note that loading of these associated files (including the local @file{.gdbinit}
22873 file) requires accordingly configured @code{auto-load safe-path}
22874 (@pxref{Auto-loading safe path}).
22876 For these reasons, @value{GDBN} includes commands and options to let you
22877 control when to auto-load files and which files should be auto-loaded.
22880 @anchor{set auto-load off}
22881 @kindex set auto-load off
22882 @item set auto-load off
22883 Globally disable loading of all auto-loaded files.
22884 You may want to use this command with the @samp{-iex} option
22885 (@pxref{Option -init-eval-command}) such as:
22887 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22890 Be aware that system init file (@pxref{System-wide configuration})
22891 and init files from your home directory (@pxref{Home Directory Init File})
22892 still get read (as they come from generally trusted directories).
22893 To prevent @value{GDBN} from auto-loading even those init files, use the
22894 @option{-nx} option (@pxref{Mode Options}), in addition to
22895 @code{set auto-load no}.
22897 @anchor{show auto-load}
22898 @kindex show auto-load
22899 @item show auto-load
22900 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22904 (gdb) show auto-load
22905 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22906 libthread-db: Auto-loading of inferior specific libthread_db is on.
22907 local-gdbinit: Auto-loading of .gdbinit script from current directory
22909 python-scripts: Auto-loading of Python scripts is on.
22910 safe-path: List of directories from which it is safe to auto-load files
22911 is $debugdir:$datadir/auto-load.
22912 scripts-directory: List of directories from which to load auto-loaded scripts
22913 is $debugdir:$datadir/auto-load.
22916 @anchor{info auto-load}
22917 @kindex info auto-load
22918 @item info auto-load
22919 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22923 (gdb) info auto-load
22926 Yes /home/user/gdb/gdb-gdb.gdb
22927 libthread-db: No auto-loaded libthread-db.
22928 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22932 Yes /home/user/gdb/gdb-gdb.py
22936 These are @value{GDBN} control commands for the auto-loading:
22938 @multitable @columnfractions .5 .5
22939 @item @xref{set auto-load off}.
22940 @tab Disable auto-loading globally.
22941 @item @xref{show auto-load}.
22942 @tab Show setting of all kinds of files.
22943 @item @xref{info auto-load}.
22944 @tab Show state of all kinds of files.
22945 @item @xref{set auto-load gdb-scripts}.
22946 @tab Control for @value{GDBN} command scripts.
22947 @item @xref{show auto-load gdb-scripts}.
22948 @tab Show setting of @value{GDBN} command scripts.
22949 @item @xref{info auto-load gdb-scripts}.
22950 @tab Show state of @value{GDBN} command scripts.
22951 @item @xref{set auto-load python-scripts}.
22952 @tab Control for @value{GDBN} Python scripts.
22953 @item @xref{show auto-load python-scripts}.
22954 @tab Show setting of @value{GDBN} Python scripts.
22955 @item @xref{info auto-load python-scripts}.
22956 @tab Show state of @value{GDBN} Python scripts.
22957 @item @xref{set auto-load guile-scripts}.
22958 @tab Control for @value{GDBN} Guile scripts.
22959 @item @xref{show auto-load guile-scripts}.
22960 @tab Show setting of @value{GDBN} Guile scripts.
22961 @item @xref{info auto-load guile-scripts}.
22962 @tab Show state of @value{GDBN} Guile scripts.
22963 @item @xref{set auto-load scripts-directory}.
22964 @tab Control for @value{GDBN} auto-loaded scripts location.
22965 @item @xref{show auto-load scripts-directory}.
22966 @tab Show @value{GDBN} auto-loaded scripts location.
22967 @item @xref{add-auto-load-scripts-directory}.
22968 @tab Add directory for auto-loaded scripts location list.
22969 @item @xref{set auto-load local-gdbinit}.
22970 @tab Control for init file in the current directory.
22971 @item @xref{show auto-load local-gdbinit}.
22972 @tab Show setting of init file in the current directory.
22973 @item @xref{info auto-load local-gdbinit}.
22974 @tab Show state of init file in the current directory.
22975 @item @xref{set auto-load libthread-db}.
22976 @tab Control for thread debugging library.
22977 @item @xref{show auto-load libthread-db}.
22978 @tab Show setting of thread debugging library.
22979 @item @xref{info auto-load libthread-db}.
22980 @tab Show state of thread debugging library.
22981 @item @xref{set auto-load safe-path}.
22982 @tab Control directories trusted for automatic loading.
22983 @item @xref{show auto-load safe-path}.
22984 @tab Show directories trusted for automatic loading.
22985 @item @xref{add-auto-load-safe-path}.
22986 @tab Add directory trusted for automatic loading.
22989 @node Init File in the Current Directory
22990 @subsection Automatically loading init file in the current directory
22991 @cindex auto-loading init file in the current directory
22993 By default, @value{GDBN} reads and executes the canned sequences of commands
22994 from init file (if any) in the current working directory,
22995 see @ref{Init File in the Current Directory during Startup}.
22997 Note that loading of this local @file{.gdbinit} file also requires accordingly
22998 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23001 @anchor{set auto-load local-gdbinit}
23002 @kindex set auto-load local-gdbinit
23003 @item set auto-load local-gdbinit [on|off]
23004 Enable or disable the auto-loading of canned sequences of commands
23005 (@pxref{Sequences}) found in init file in the current directory.
23007 @anchor{show auto-load local-gdbinit}
23008 @kindex show auto-load local-gdbinit
23009 @item show auto-load local-gdbinit
23010 Show whether auto-loading of canned sequences of commands from init file in the
23011 current directory is enabled or disabled.
23013 @anchor{info auto-load local-gdbinit}
23014 @kindex info auto-load local-gdbinit
23015 @item info auto-load local-gdbinit
23016 Print whether canned sequences of commands from init file in the
23017 current directory have been auto-loaded.
23020 @node libthread_db.so.1 file
23021 @subsection Automatically loading thread debugging library
23022 @cindex auto-loading libthread_db.so.1
23024 This feature is currently present only on @sc{gnu}/Linux native hosts.
23026 @value{GDBN} reads in some cases thread debugging library from places specific
23027 to the inferior (@pxref{set libthread-db-search-path}).
23029 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23030 without checking this @samp{set auto-load libthread-db} switch as system
23031 libraries have to be trusted in general. In all other cases of
23032 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23033 auto-load libthread-db} is enabled before trying to open such thread debugging
23036 Note that loading of this debugging library also requires accordingly configured
23037 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23040 @anchor{set auto-load libthread-db}
23041 @kindex set auto-load libthread-db
23042 @item set auto-load libthread-db [on|off]
23043 Enable or disable the auto-loading of inferior specific thread debugging library.
23045 @anchor{show auto-load libthread-db}
23046 @kindex show auto-load libthread-db
23047 @item show auto-load libthread-db
23048 Show whether auto-loading of inferior specific thread debugging library is
23049 enabled or disabled.
23051 @anchor{info auto-load libthread-db}
23052 @kindex info auto-load libthread-db
23053 @item info auto-load libthread-db
23054 Print the list of all loaded inferior specific thread debugging libraries and
23055 for each such library print list of inferior @var{pid}s using it.
23058 @node Auto-loading safe path
23059 @subsection Security restriction for auto-loading
23060 @cindex auto-loading safe-path
23062 As the files of inferior can come from untrusted source (such as submitted by
23063 an application user) @value{GDBN} does not always load any files automatically.
23064 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23065 directories trusted for loading files not explicitly requested by user.
23066 Each directory can also be a shell wildcard pattern.
23068 If the path is not set properly you will see a warning and the file will not
23073 Reading symbols from /home/user/gdb/gdb...done.
23074 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23075 declined by your `auto-load safe-path' set
23076 to "$debugdir:$datadir/auto-load".
23077 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23078 declined by your `auto-load safe-path' set
23079 to "$debugdir:$datadir/auto-load".
23083 To instruct @value{GDBN} to go ahead and use the init files anyway,
23084 invoke @value{GDBN} like this:
23087 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23090 The list of trusted directories is controlled by the following commands:
23093 @anchor{set auto-load safe-path}
23094 @kindex set auto-load safe-path
23095 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23096 Set the list of directories (and their subdirectories) trusted for automatic
23097 loading and execution of scripts. You can also enter a specific trusted file.
23098 Each directory can also be a shell wildcard pattern; wildcards do not match
23099 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23100 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23101 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23102 its default value as specified during @value{GDBN} compilation.
23104 The list of directories uses path separator (@samp{:} on GNU and Unix
23105 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23106 to the @env{PATH} environment variable.
23108 @anchor{show auto-load safe-path}
23109 @kindex show auto-load safe-path
23110 @item show auto-load safe-path
23111 Show the list of directories trusted for automatic loading and execution of
23114 @anchor{add-auto-load-safe-path}
23115 @kindex add-auto-load-safe-path
23116 @item add-auto-load-safe-path
23117 Add an entry (or list of entries) to the list of directories trusted for
23118 automatic loading and execution of scripts. Multiple entries may be delimited
23119 by the host platform path separator in use.
23122 This variable defaults to what @code{--with-auto-load-dir} has been configured
23123 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23124 substitution applies the same as for @ref{set auto-load scripts-directory}.
23125 The default @code{set auto-load safe-path} value can be also overriden by
23126 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23128 Setting this variable to @file{/} disables this security protection,
23129 corresponding @value{GDBN} configuration option is
23130 @option{--without-auto-load-safe-path}.
23131 This variable is supposed to be set to the system directories writable by the
23132 system superuser only. Users can add their source directories in init files in
23133 their home directories (@pxref{Home Directory Init File}). See also deprecated
23134 init file in the current directory
23135 (@pxref{Init File in the Current Directory during Startup}).
23137 To force @value{GDBN} to load the files it declined to load in the previous
23138 example, you could use one of the following ways:
23141 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23142 Specify this trusted directory (or a file) as additional component of the list.
23143 You have to specify also any existing directories displayed by
23144 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23146 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23147 Specify this directory as in the previous case but just for a single
23148 @value{GDBN} session.
23150 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23151 Disable auto-loading safety for a single @value{GDBN} session.
23152 This assumes all the files you debug during this @value{GDBN} session will come
23153 from trusted sources.
23155 @item @kbd{./configure --without-auto-load-safe-path}
23156 During compilation of @value{GDBN} you may disable any auto-loading safety.
23157 This assumes all the files you will ever debug with this @value{GDBN} come from
23161 On the other hand you can also explicitly forbid automatic files loading which
23162 also suppresses any such warning messages:
23165 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23166 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23168 @item @file{~/.gdbinit}: @samp{set auto-load no}
23169 Disable auto-loading globally for the user
23170 (@pxref{Home Directory Init File}). While it is improbable, you could also
23171 use system init file instead (@pxref{System-wide configuration}).
23174 This setting applies to the file names as entered by user. If no entry matches
23175 @value{GDBN} tries as a last resort to also resolve all the file names into
23176 their canonical form (typically resolving symbolic links) and compare the
23177 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23178 own before starting the comparison so a canonical form of directories is
23179 recommended to be entered.
23181 @node Auto-loading verbose mode
23182 @subsection Displaying files tried for auto-load
23183 @cindex auto-loading verbose mode
23185 For better visibility of all the file locations where you can place scripts to
23186 be auto-loaded with inferior --- or to protect yourself against accidental
23187 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23188 all the files attempted to be loaded. Both existing and non-existing files may
23191 For example the list of directories from which it is safe to auto-load files
23192 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23193 may not be too obvious while setting it up.
23196 (gdb) set debug auto-load on
23197 (gdb) file ~/src/t/true
23198 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23199 for objfile "/tmp/true".
23200 auto-load: Updating directories of "/usr:/opt".
23201 auto-load: Using directory "/usr".
23202 auto-load: Using directory "/opt".
23203 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23204 by your `auto-load safe-path' set to "/usr:/opt".
23208 @anchor{set debug auto-load}
23209 @kindex set debug auto-load
23210 @item set debug auto-load [on|off]
23211 Set whether to print the filenames attempted to be auto-loaded.
23213 @anchor{show debug auto-load}
23214 @kindex show debug auto-load
23215 @item show debug auto-load
23216 Show whether printing of the filenames attempted to be auto-loaded is turned
23220 @node Messages/Warnings
23221 @section Optional Warnings and Messages
23223 @cindex verbose operation
23224 @cindex optional warnings
23225 By default, @value{GDBN} is silent about its inner workings. If you are
23226 running on a slow machine, you may want to use the @code{set verbose}
23227 command. This makes @value{GDBN} tell you when it does a lengthy
23228 internal operation, so you will not think it has crashed.
23230 Currently, the messages controlled by @code{set verbose} are those
23231 which announce that the symbol table for a source file is being read;
23232 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23235 @kindex set verbose
23236 @item set verbose on
23237 Enables @value{GDBN} output of certain informational messages.
23239 @item set verbose off
23240 Disables @value{GDBN} output of certain informational messages.
23242 @kindex show verbose
23244 Displays whether @code{set verbose} is on or off.
23247 By default, if @value{GDBN} encounters bugs in the symbol table of an
23248 object file, it is silent; but if you are debugging a compiler, you may
23249 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23254 @kindex set complaints
23255 @item set complaints @var{limit}
23256 Permits @value{GDBN} to output @var{limit} complaints about each type of
23257 unusual symbols before becoming silent about the problem. Set
23258 @var{limit} to zero to suppress all complaints; set it to a large number
23259 to prevent complaints from being suppressed.
23261 @kindex show complaints
23262 @item show complaints
23263 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23267 @anchor{confirmation requests}
23268 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23269 lot of stupid questions to confirm certain commands. For example, if
23270 you try to run a program which is already running:
23274 The program being debugged has been started already.
23275 Start it from the beginning? (y or n)
23278 If you are willing to unflinchingly face the consequences of your own
23279 commands, you can disable this ``feature'':
23283 @kindex set confirm
23285 @cindex confirmation
23286 @cindex stupid questions
23287 @item set confirm off
23288 Disables confirmation requests. Note that running @value{GDBN} with
23289 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23290 automatically disables confirmation requests.
23292 @item set confirm on
23293 Enables confirmation requests (the default).
23295 @kindex show confirm
23297 Displays state of confirmation requests.
23301 @cindex command tracing
23302 If you need to debug user-defined commands or sourced files you may find it
23303 useful to enable @dfn{command tracing}. In this mode each command will be
23304 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23305 quantity denoting the call depth of each command.
23308 @kindex set trace-commands
23309 @cindex command scripts, debugging
23310 @item set trace-commands on
23311 Enable command tracing.
23312 @item set trace-commands off
23313 Disable command tracing.
23314 @item show trace-commands
23315 Display the current state of command tracing.
23318 @node Debugging Output
23319 @section Optional Messages about Internal Happenings
23320 @cindex optional debugging messages
23322 @value{GDBN} has commands that enable optional debugging messages from
23323 various @value{GDBN} subsystems; normally these commands are of
23324 interest to @value{GDBN} maintainers, or when reporting a bug. This
23325 section documents those commands.
23328 @kindex set exec-done-display
23329 @item set exec-done-display
23330 Turns on or off the notification of asynchronous commands'
23331 completion. When on, @value{GDBN} will print a message when an
23332 asynchronous command finishes its execution. The default is off.
23333 @kindex show exec-done-display
23334 @item show exec-done-display
23335 Displays the current setting of asynchronous command completion
23338 @cindex ARM AArch64
23339 @item set debug aarch64
23340 Turns on or off display of debugging messages related to ARM AArch64.
23341 The default is off.
23343 @item show debug aarch64
23344 Displays the current state of displaying debugging messages related to
23346 @cindex gdbarch debugging info
23347 @cindex architecture debugging info
23348 @item set debug arch
23349 Turns on or off display of gdbarch debugging info. The default is off
23350 @item show debug arch
23351 Displays the current state of displaying gdbarch debugging info.
23352 @item set debug aix-solib
23353 @cindex AIX shared library debugging
23354 Control display of debugging messages from the AIX shared library
23355 support module. The default is off.
23356 @item show debug aix-thread
23357 Show the current state of displaying AIX shared library debugging messages.
23358 @item set debug aix-thread
23359 @cindex AIX threads
23360 Display debugging messages about inner workings of the AIX thread
23362 @item show debug aix-thread
23363 Show the current state of AIX thread debugging info display.
23364 @item set debug check-physname
23366 Check the results of the ``physname'' computation. When reading DWARF
23367 debugging information for C@t{++}, @value{GDBN} attempts to compute
23368 each entity's name. @value{GDBN} can do this computation in two
23369 different ways, depending on exactly what information is present.
23370 When enabled, this setting causes @value{GDBN} to compute the names
23371 both ways and display any discrepancies.
23372 @item show debug check-physname
23373 Show the current state of ``physname'' checking.
23374 @item set debug coff-pe-read
23375 @cindex COFF/PE exported symbols
23376 Control display of debugging messages related to reading of COFF/PE
23377 exported symbols. The default is off.
23378 @item show debug coff-pe-read
23379 Displays the current state of displaying debugging messages related to
23380 reading of COFF/PE exported symbols.
23381 @item set debug dwarf2-die
23382 @cindex DWARF2 DIEs
23383 Dump DWARF2 DIEs after they are read in.
23384 The value is the number of nesting levels to print.
23385 A value of zero turns off the display.
23386 @item show debug dwarf2-die
23387 Show the current state of DWARF2 DIE debugging.
23388 @item set debug dwarf2-read
23389 @cindex DWARF2 Reading
23390 Turns on or off display of debugging messages related to reading
23391 DWARF debug info. The default is 0 (off).
23392 A value of 1 provides basic information.
23393 A value greater than 1 provides more verbose information.
23394 @item show debug dwarf2-read
23395 Show the current state of DWARF2 reader debugging.
23396 @item set debug displaced
23397 @cindex displaced stepping debugging info
23398 Turns on or off display of @value{GDBN} debugging info for the
23399 displaced stepping support. The default is off.
23400 @item show debug displaced
23401 Displays the current state of displaying @value{GDBN} debugging info
23402 related to displaced stepping.
23403 @item set debug event
23404 @cindex event debugging info
23405 Turns on or off display of @value{GDBN} event debugging info. The
23407 @item show debug event
23408 Displays the current state of displaying @value{GDBN} event debugging
23410 @item set debug expression
23411 @cindex expression debugging info
23412 Turns on or off display of debugging info about @value{GDBN}
23413 expression parsing. The default is off.
23414 @item show debug expression
23415 Displays the current state of displaying debugging info about
23416 @value{GDBN} expression parsing.
23417 @item set debug frame
23418 @cindex frame debugging info
23419 Turns on or off display of @value{GDBN} frame debugging info. The
23421 @item show debug frame
23422 Displays the current state of displaying @value{GDBN} frame debugging
23424 @item set debug gnu-nat
23425 @cindex @sc{gnu}/Hurd debug messages
23426 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23427 @item show debug gnu-nat
23428 Show the current state of @sc{gnu}/Hurd debugging messages.
23429 @item set debug infrun
23430 @cindex inferior debugging info
23431 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23432 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23433 for implementing operations such as single-stepping the inferior.
23434 @item show debug infrun
23435 Displays the current state of @value{GDBN} inferior debugging.
23436 @item set debug jit
23437 @cindex just-in-time compilation, debugging messages
23438 Turns on or off debugging messages from JIT debug support.
23439 @item show debug jit
23440 Displays the current state of @value{GDBN} JIT debugging.
23441 @item set debug lin-lwp
23442 @cindex @sc{gnu}/Linux LWP debug messages
23443 @cindex Linux lightweight processes
23444 Turns on or off debugging messages from the Linux LWP debug support.
23445 @item show debug lin-lwp
23446 Show the current state of Linux LWP debugging messages.
23447 @item set debug mach-o
23448 @cindex Mach-O symbols processing
23449 Control display of debugging messages related to Mach-O symbols
23450 processing. The default is off.
23451 @item show debug mach-o
23452 Displays the current state of displaying debugging messages related to
23453 reading of COFF/PE exported symbols.
23454 @item set debug notification
23455 @cindex remote async notification debugging info
23456 Turns on or off debugging messages about remote async notification.
23457 The default is off.
23458 @item show debug notification
23459 Displays the current state of remote async notification debugging messages.
23460 @item set debug observer
23461 @cindex observer debugging info
23462 Turns on or off display of @value{GDBN} observer debugging. This
23463 includes info such as the notification of observable events.
23464 @item show debug observer
23465 Displays the current state of observer debugging.
23466 @item set debug overload
23467 @cindex C@t{++} overload debugging info
23468 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23469 info. This includes info such as ranking of functions, etc. The default
23471 @item show debug overload
23472 Displays the current state of displaying @value{GDBN} C@t{++} overload
23474 @cindex expression parser, debugging info
23475 @cindex debug expression parser
23476 @item set debug parser
23477 Turns on or off the display of expression parser debugging output.
23478 Internally, this sets the @code{yydebug} variable in the expression
23479 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23480 details. The default is off.
23481 @item show debug parser
23482 Show the current state of expression parser debugging.
23483 @cindex packets, reporting on stdout
23484 @cindex serial connections, debugging
23485 @cindex debug remote protocol
23486 @cindex remote protocol debugging
23487 @cindex display remote packets
23488 @item set debug remote
23489 Turns on or off display of reports on all packets sent back and forth across
23490 the serial line to the remote machine. The info is printed on the
23491 @value{GDBN} standard output stream. The default is off.
23492 @item show debug remote
23493 Displays the state of display of remote packets.
23494 @item set debug serial
23495 Turns on or off display of @value{GDBN} serial debugging info. The
23497 @item show debug serial
23498 Displays the current state of displaying @value{GDBN} serial debugging
23500 @item set debug solib-frv
23501 @cindex FR-V shared-library debugging
23502 Turns on or off debugging messages for FR-V shared-library code.
23503 @item show debug solib-frv
23504 Display the current state of FR-V shared-library code debugging
23506 @item set debug symbol-lookup
23507 @cindex symbol lookup
23508 Turns on or off display of debugging messages related to symbol lookup.
23509 The default is 0 (off).
23510 A value of 1 provides basic information.
23511 A value greater than 1 provides more verbose information.
23512 @item show debug symbol-lookup
23513 Show the current state of symbol lookup debugging messages.
23514 @item set debug symfile
23515 @cindex symbol file functions
23516 Turns on or off display of debugging messages related to symbol file functions.
23517 The default is off. @xref{Files}.
23518 @item show debug symfile
23519 Show the current state of symbol file debugging messages.
23520 @item set debug symtab-create
23521 @cindex symbol table creation
23522 Turns on or off display of debugging messages related to symbol table creation.
23523 The default is 0 (off).
23524 A value of 1 provides basic information.
23525 A value greater than 1 provides more verbose information.
23526 @item show debug symtab-create
23527 Show the current state of symbol table creation debugging.
23528 @item set debug target
23529 @cindex target debugging info
23530 Turns on or off display of @value{GDBN} target debugging info. This info
23531 includes what is going on at the target level of GDB, as it happens. The
23532 default is 0. Set it to 1 to track events, and to 2 to also track the
23533 value of large memory transfers.
23534 @item show debug target
23535 Displays the current state of displaying @value{GDBN} target debugging
23537 @item set debug timestamp
23538 @cindex timestampping debugging info
23539 Turns on or off display of timestamps with @value{GDBN} debugging info.
23540 When enabled, seconds and microseconds are displayed before each debugging
23542 @item show debug timestamp
23543 Displays the current state of displaying timestamps with @value{GDBN}
23545 @item set debug varobj
23546 @cindex variable object debugging info
23547 Turns on or off display of @value{GDBN} variable object debugging
23548 info. The default is off.
23549 @item show debug varobj
23550 Displays the current state of displaying @value{GDBN} variable object
23552 @item set debug xml
23553 @cindex XML parser debugging
23554 Turns on or off debugging messages for built-in XML parsers.
23555 @item show debug xml
23556 Displays the current state of XML debugging messages.
23559 @node Other Misc Settings
23560 @section Other Miscellaneous Settings
23561 @cindex miscellaneous settings
23564 @kindex set interactive-mode
23565 @item set interactive-mode
23566 If @code{on}, forces @value{GDBN} to assume that GDB was started
23567 in a terminal. In practice, this means that @value{GDBN} should wait
23568 for the user to answer queries generated by commands entered at
23569 the command prompt. If @code{off}, forces @value{GDBN} to operate
23570 in the opposite mode, and it uses the default answers to all queries.
23571 If @code{auto} (the default), @value{GDBN} tries to determine whether
23572 its standard input is a terminal, and works in interactive-mode if it
23573 is, non-interactively otherwise.
23575 In the vast majority of cases, the debugger should be able to guess
23576 correctly which mode should be used. But this setting can be useful
23577 in certain specific cases, such as running a MinGW @value{GDBN}
23578 inside a cygwin window.
23580 @kindex show interactive-mode
23581 @item show interactive-mode
23582 Displays whether the debugger is operating in interactive mode or not.
23585 @node Extending GDB
23586 @chapter Extending @value{GDBN}
23587 @cindex extending GDB
23589 @value{GDBN} provides several mechanisms for extension.
23590 @value{GDBN} also provides the ability to automatically load
23591 extensions when it reads a file for debugging. This allows the
23592 user to automatically customize @value{GDBN} for the program
23596 * Sequences:: Canned Sequences of @value{GDBN} Commands
23597 * Python:: Extending @value{GDBN} using Python
23598 * Guile:: Extending @value{GDBN} using Guile
23599 * Auto-loading extensions:: Automatically loading extensions
23600 * Multiple Extension Languages:: Working with multiple extension languages
23601 * Aliases:: Creating new spellings of existing commands
23604 To facilitate the use of extension languages, @value{GDBN} is capable
23605 of evaluating the contents of a file. When doing so, @value{GDBN}
23606 can recognize which extension language is being used by looking at
23607 the filename extension. Files with an unrecognized filename extension
23608 are always treated as a @value{GDBN} Command Files.
23609 @xref{Command Files,, Command files}.
23611 You can control how @value{GDBN} evaluates these files with the following
23615 @kindex set script-extension
23616 @kindex show script-extension
23617 @item set script-extension off
23618 All scripts are always evaluated as @value{GDBN} Command Files.
23620 @item set script-extension soft
23621 The debugger determines the scripting language based on filename
23622 extension. If this scripting language is supported, @value{GDBN}
23623 evaluates the script using that language. Otherwise, it evaluates
23624 the file as a @value{GDBN} Command File.
23626 @item set script-extension strict
23627 The debugger determines the scripting language based on filename
23628 extension, and evaluates the script using that language. If the
23629 language is not supported, then the evaluation fails.
23631 @item show script-extension
23632 Display the current value of the @code{script-extension} option.
23637 @section Canned Sequences of Commands
23639 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23640 Command Lists}), @value{GDBN} provides two ways to store sequences of
23641 commands for execution as a unit: user-defined commands and command
23645 * Define:: How to define your own commands
23646 * Hooks:: Hooks for user-defined commands
23647 * Command Files:: How to write scripts of commands to be stored in a file
23648 * Output:: Commands for controlled output
23649 * Auto-loading sequences:: Controlling auto-loaded command files
23653 @subsection User-defined Commands
23655 @cindex user-defined command
23656 @cindex arguments, to user-defined commands
23657 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23658 which you assign a new name as a command. This is done with the
23659 @code{define} command. User commands may accept up to 10 arguments
23660 separated by whitespace. Arguments are accessed within the user command
23661 via @code{$arg0@dots{}$arg9}. A trivial example:
23665 print $arg0 + $arg1 + $arg2
23670 To execute the command use:
23677 This defines the command @code{adder}, which prints the sum of
23678 its three arguments. Note the arguments are text substitutions, so they may
23679 reference variables, use complex expressions, or even perform inferior
23682 @cindex argument count in user-defined commands
23683 @cindex how many arguments (user-defined commands)
23684 In addition, @code{$argc} may be used to find out how many arguments have
23685 been passed. This expands to a number in the range 0@dots{}10.
23690 print $arg0 + $arg1
23693 print $arg0 + $arg1 + $arg2
23701 @item define @var{commandname}
23702 Define a command named @var{commandname}. If there is already a command
23703 by that name, you are asked to confirm that you want to redefine it.
23704 The argument @var{commandname} may be a bare command name consisting of letters,
23705 numbers, dashes, and underscores. It may also start with any predefined
23706 prefix command. For example, @samp{define target my-target} creates
23707 a user-defined @samp{target my-target} command.
23709 The definition of the command is made up of other @value{GDBN} command lines,
23710 which are given following the @code{define} command. The end of these
23711 commands is marked by a line containing @code{end}.
23714 @kindex end@r{ (user-defined commands)}
23715 @item document @var{commandname}
23716 Document the user-defined command @var{commandname}, so that it can be
23717 accessed by @code{help}. The command @var{commandname} must already be
23718 defined. This command reads lines of documentation just as @code{define}
23719 reads the lines of the command definition, ending with @code{end}.
23720 After the @code{document} command is finished, @code{help} on command
23721 @var{commandname} displays the documentation you have written.
23723 You may use the @code{document} command again to change the
23724 documentation of a command. Redefining the command with @code{define}
23725 does not change the documentation.
23727 @kindex dont-repeat
23728 @cindex don't repeat command
23730 Used inside a user-defined command, this tells @value{GDBN} that this
23731 command should not be repeated when the user hits @key{RET}
23732 (@pxref{Command Syntax, repeat last command}).
23734 @kindex help user-defined
23735 @item help user-defined
23736 List all user-defined commands and all python commands defined in class
23737 COMAND_USER. The first line of the documentation or docstring is
23742 @itemx show user @var{commandname}
23743 Display the @value{GDBN} commands used to define @var{commandname} (but
23744 not its documentation). If no @var{commandname} is given, display the
23745 definitions for all user-defined commands.
23746 This does not work for user-defined python commands.
23748 @cindex infinite recursion in user-defined commands
23749 @kindex show max-user-call-depth
23750 @kindex set max-user-call-depth
23751 @item show max-user-call-depth
23752 @itemx set max-user-call-depth
23753 The value of @code{max-user-call-depth} controls how many recursion
23754 levels are allowed in user-defined commands before @value{GDBN} suspects an
23755 infinite recursion and aborts the command.
23756 This does not apply to user-defined python commands.
23759 In addition to the above commands, user-defined commands frequently
23760 use control flow commands, described in @ref{Command Files}.
23762 When user-defined commands are executed, the
23763 commands of the definition are not printed. An error in any command
23764 stops execution of the user-defined command.
23766 If used interactively, commands that would ask for confirmation proceed
23767 without asking when used inside a user-defined command. Many @value{GDBN}
23768 commands that normally print messages to say what they are doing omit the
23769 messages when used in a user-defined command.
23772 @subsection User-defined Command Hooks
23773 @cindex command hooks
23774 @cindex hooks, for commands
23775 @cindex hooks, pre-command
23778 You may define @dfn{hooks}, which are a special kind of user-defined
23779 command. Whenever you run the command @samp{foo}, if the user-defined
23780 command @samp{hook-foo} exists, it is executed (with no arguments)
23781 before that command.
23783 @cindex hooks, post-command
23785 A hook may also be defined which is run after the command you executed.
23786 Whenever you run the command @samp{foo}, if the user-defined command
23787 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23788 that command. Post-execution hooks may exist simultaneously with
23789 pre-execution hooks, for the same command.
23791 It is valid for a hook to call the command which it hooks. If this
23792 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23794 @c It would be nice if hookpost could be passed a parameter indicating
23795 @c if the command it hooks executed properly or not. FIXME!
23797 @kindex stop@r{, a pseudo-command}
23798 In addition, a pseudo-command, @samp{stop} exists. Defining
23799 (@samp{hook-stop}) makes the associated commands execute every time
23800 execution stops in your program: before breakpoint commands are run,
23801 displays are printed, or the stack frame is printed.
23803 For example, to ignore @code{SIGALRM} signals while
23804 single-stepping, but treat them normally during normal execution,
23809 handle SIGALRM nopass
23813 handle SIGALRM pass
23816 define hook-continue
23817 handle SIGALRM pass
23821 As a further example, to hook at the beginning and end of the @code{echo}
23822 command, and to add extra text to the beginning and end of the message,
23830 define hookpost-echo
23834 (@value{GDBP}) echo Hello World
23835 <<<---Hello World--->>>
23840 You can define a hook for any single-word command in @value{GDBN}, but
23841 not for command aliases; you should define a hook for the basic command
23842 name, e.g.@: @code{backtrace} rather than @code{bt}.
23843 @c FIXME! So how does Joe User discover whether a command is an alias
23845 You can hook a multi-word command by adding @code{hook-} or
23846 @code{hookpost-} to the last word of the command, e.g.@:
23847 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23849 If an error occurs during the execution of your hook, execution of
23850 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23851 (before the command that you actually typed had a chance to run).
23853 If you try to define a hook which does not match any known command, you
23854 get a warning from the @code{define} command.
23856 @node Command Files
23857 @subsection Command Files
23859 @cindex command files
23860 @cindex scripting commands
23861 A command file for @value{GDBN} is a text file made of lines that are
23862 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23863 also be included. An empty line in a command file does nothing; it
23864 does not mean to repeat the last command, as it would from the
23867 You can request the execution of a command file with the @code{source}
23868 command. Note that the @code{source} command is also used to evaluate
23869 scripts that are not Command Files. The exact behavior can be configured
23870 using the @code{script-extension} setting.
23871 @xref{Extending GDB,, Extending GDB}.
23875 @cindex execute commands from a file
23876 @item source [-s] [-v] @var{filename}
23877 Execute the command file @var{filename}.
23880 The lines in a command file are generally executed sequentially,
23881 unless the order of execution is changed by one of the
23882 @emph{flow-control commands} described below. The commands are not
23883 printed as they are executed. An error in any command terminates
23884 execution of the command file and control is returned to the console.
23886 @value{GDBN} first searches for @var{filename} in the current directory.
23887 If the file is not found there, and @var{filename} does not specify a
23888 directory, then @value{GDBN} also looks for the file on the source search path
23889 (specified with the @samp{directory} command);
23890 except that @file{$cdir} is not searched because the compilation directory
23891 is not relevant to scripts.
23893 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23894 on the search path even if @var{filename} specifies a directory.
23895 The search is done by appending @var{filename} to each element of the
23896 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23897 and the search path contains @file{/home/user} then @value{GDBN} will
23898 look for the script @file{/home/user/mylib/myscript}.
23899 The search is also done if @var{filename} is an absolute path.
23900 For example, if @var{filename} is @file{/tmp/myscript} and
23901 the search path contains @file{/home/user} then @value{GDBN} will
23902 look for the script @file{/home/user/tmp/myscript}.
23903 For DOS-like systems, if @var{filename} contains a drive specification,
23904 it is stripped before concatenation. For example, if @var{filename} is
23905 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23906 will look for the script @file{c:/tmp/myscript}.
23908 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23909 each command as it is executed. The option must be given before
23910 @var{filename}, and is interpreted as part of the filename anywhere else.
23912 Commands that would ask for confirmation if used interactively proceed
23913 without asking when used in a command file. Many @value{GDBN} commands that
23914 normally print messages to say what they are doing omit the messages
23915 when called from command files.
23917 @value{GDBN} also accepts command input from standard input. In this
23918 mode, normal output goes to standard output and error output goes to
23919 standard error. Errors in a command file supplied on standard input do
23920 not terminate execution of the command file---execution continues with
23924 gdb < cmds > log 2>&1
23927 (The syntax above will vary depending on the shell used.) This example
23928 will execute commands from the file @file{cmds}. All output and errors
23929 would be directed to @file{log}.
23931 Since commands stored on command files tend to be more general than
23932 commands typed interactively, they frequently need to deal with
23933 complicated situations, such as different or unexpected values of
23934 variables and symbols, changes in how the program being debugged is
23935 built, etc. @value{GDBN} provides a set of flow-control commands to
23936 deal with these complexities. Using these commands, you can write
23937 complex scripts that loop over data structures, execute commands
23938 conditionally, etc.
23945 This command allows to include in your script conditionally executed
23946 commands. The @code{if} command takes a single argument, which is an
23947 expression to evaluate. It is followed by a series of commands that
23948 are executed only if the expression is true (its value is nonzero).
23949 There can then optionally be an @code{else} line, followed by a series
23950 of commands that are only executed if the expression was false. The
23951 end of the list is marked by a line containing @code{end}.
23955 This command allows to write loops. Its syntax is similar to
23956 @code{if}: the command takes a single argument, which is an expression
23957 to evaluate, and must be followed by the commands to execute, one per
23958 line, terminated by an @code{end}. These commands are called the
23959 @dfn{body} of the loop. The commands in the body of @code{while} are
23960 executed repeatedly as long as the expression evaluates to true.
23964 This command exits the @code{while} loop in whose body it is included.
23965 Execution of the script continues after that @code{while}s @code{end}
23968 @kindex loop_continue
23969 @item loop_continue
23970 This command skips the execution of the rest of the body of commands
23971 in the @code{while} loop in whose body it is included. Execution
23972 branches to the beginning of the @code{while} loop, where it evaluates
23973 the controlling expression.
23975 @kindex end@r{ (if/else/while commands)}
23977 Terminate the block of commands that are the body of @code{if},
23978 @code{else}, or @code{while} flow-control commands.
23983 @subsection Commands for Controlled Output
23985 During the execution of a command file or a user-defined command, normal
23986 @value{GDBN} output is suppressed; the only output that appears is what is
23987 explicitly printed by the commands in the definition. This section
23988 describes three commands useful for generating exactly the output you
23993 @item echo @var{text}
23994 @c I do not consider backslash-space a standard C escape sequence
23995 @c because it is not in ANSI.
23996 Print @var{text}. Nonprinting characters can be included in
23997 @var{text} using C escape sequences, such as @samp{\n} to print a
23998 newline. @strong{No newline is printed unless you specify one.}
23999 In addition to the standard C escape sequences, a backslash followed
24000 by a space stands for a space. This is useful for displaying a
24001 string with spaces at the beginning or the end, since leading and
24002 trailing spaces are otherwise trimmed from all arguments.
24003 To print @samp{@w{ }and foo =@w{ }}, use the command
24004 @samp{echo \@w{ }and foo = \@w{ }}.
24006 A backslash at the end of @var{text} can be used, as in C, to continue
24007 the command onto subsequent lines. For example,
24010 echo This is some text\n\
24011 which is continued\n\
24012 onto several lines.\n
24015 produces the same output as
24018 echo This is some text\n
24019 echo which is continued\n
24020 echo onto several lines.\n
24024 @item output @var{expression}
24025 Print the value of @var{expression} and nothing but that value: no
24026 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24027 value history either. @xref{Expressions, ,Expressions}, for more information
24030 @item output/@var{fmt} @var{expression}
24031 Print the value of @var{expression} in format @var{fmt}. You can use
24032 the same formats as for @code{print}. @xref{Output Formats,,Output
24033 Formats}, for more information.
24036 @item printf @var{template}, @var{expressions}@dots{}
24037 Print the values of one or more @var{expressions} under the control of
24038 the string @var{template}. To print several values, make
24039 @var{expressions} be a comma-separated list of individual expressions,
24040 which may be either numbers or pointers. Their values are printed as
24041 specified by @var{template}, exactly as a C program would do by
24042 executing the code below:
24045 printf (@var{template}, @var{expressions}@dots{});
24048 As in @code{C} @code{printf}, ordinary characters in @var{template}
24049 are printed verbatim, while @dfn{conversion specification} introduced
24050 by the @samp{%} character cause subsequent @var{expressions} to be
24051 evaluated, their values converted and formatted according to type and
24052 style information encoded in the conversion specifications, and then
24055 For example, you can print two values in hex like this:
24058 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24061 @code{printf} supports all the standard @code{C} conversion
24062 specifications, including the flags and modifiers between the @samp{%}
24063 character and the conversion letter, with the following exceptions:
24067 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24070 The modifier @samp{*} is not supported for specifying precision or
24074 The @samp{'} flag (for separation of digits into groups according to
24075 @code{LC_NUMERIC'}) is not supported.
24078 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24082 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24085 The conversion letters @samp{a} and @samp{A} are not supported.
24089 Note that the @samp{ll} type modifier is supported only if the
24090 underlying @code{C} implementation used to build @value{GDBN} supports
24091 the @code{long long int} type, and the @samp{L} type modifier is
24092 supported only if @code{long double} type is available.
24094 As in @code{C}, @code{printf} supports simple backslash-escape
24095 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24096 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24097 single character. Octal and hexadecimal escape sequences are not
24100 Additionally, @code{printf} supports conversion specifications for DFP
24101 (@dfn{Decimal Floating Point}) types using the following length modifiers
24102 together with a floating point specifier.
24107 @samp{H} for printing @code{Decimal32} types.
24110 @samp{D} for printing @code{Decimal64} types.
24113 @samp{DD} for printing @code{Decimal128} types.
24116 If the underlying @code{C} implementation used to build @value{GDBN} has
24117 support for the three length modifiers for DFP types, other modifiers
24118 such as width and precision will also be available for @value{GDBN} to use.
24120 In case there is no such @code{C} support, no additional modifiers will be
24121 available and the value will be printed in the standard way.
24123 Here's an example of printing DFP types using the above conversion letters:
24125 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24129 @item eval @var{template}, @var{expressions}@dots{}
24130 Convert the values of one or more @var{expressions} under the control of
24131 the string @var{template} to a command line, and call it.
24135 @node Auto-loading sequences
24136 @subsection Controlling auto-loading native @value{GDBN} scripts
24137 @cindex native script auto-loading
24139 When a new object file is read (for example, due to the @code{file}
24140 command, or because the inferior has loaded a shared library),
24141 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24142 @xref{Auto-loading extensions}.
24144 Auto-loading can be enabled or disabled,
24145 and the list of auto-loaded scripts can be printed.
24148 @anchor{set auto-load gdb-scripts}
24149 @kindex set auto-load gdb-scripts
24150 @item set auto-load gdb-scripts [on|off]
24151 Enable or disable the auto-loading of canned sequences of commands scripts.
24153 @anchor{show auto-load gdb-scripts}
24154 @kindex show auto-load gdb-scripts
24155 @item show auto-load gdb-scripts
24156 Show whether auto-loading of canned sequences of commands scripts is enabled or
24159 @anchor{info auto-load gdb-scripts}
24160 @kindex info auto-load gdb-scripts
24161 @cindex print list of auto-loaded canned sequences of commands scripts
24162 @item info auto-load gdb-scripts [@var{regexp}]
24163 Print the list of all canned sequences of commands scripts that @value{GDBN}
24167 If @var{regexp} is supplied only canned sequences of commands scripts with
24168 matching names are printed.
24170 @c Python docs live in a separate file.
24171 @include python.texi
24173 @c Guile docs live in a separate file.
24174 @include guile.texi
24176 @node Auto-loading extensions
24177 @section Auto-loading extensions
24178 @cindex auto-loading extensions
24180 @value{GDBN} provides two mechanisms for automatically loading extensions
24181 when a new object file is read (for example, due to the @code{file}
24182 command, or because the inferior has loaded a shared library):
24183 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24184 section of modern file formats like ELF.
24187 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24188 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24189 * Which flavor to choose?::
24192 The auto-loading feature is useful for supplying application-specific
24193 debugging commands and features.
24195 Auto-loading can be enabled or disabled,
24196 and the list of auto-loaded scripts can be printed.
24197 See the @samp{auto-loading} section of each extension language
24198 for more information.
24199 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24200 For Python files see @ref{Python Auto-loading}.
24202 Note that loading of this script file also requires accordingly configured
24203 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24205 @node objfile-gdbdotext file
24206 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24207 @cindex @file{@var{objfile}-gdb.gdb}
24208 @cindex @file{@var{objfile}-gdb.py}
24209 @cindex @file{@var{objfile}-gdb.scm}
24211 When a new object file is read, @value{GDBN} looks for a file named
24212 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24213 where @var{objfile} is the object file's name and
24214 where @var{ext} is the file extension for the extension language:
24217 @item @file{@var{objfile}-gdb.gdb}
24218 GDB's own command language
24219 @item @file{@var{objfile}-gdb.py}
24221 @item @file{@var{objfile}-gdb.scm}
24225 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24226 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24227 components, and appending the @file{-gdb.@var{ext}} suffix.
24228 If this file exists and is readable, @value{GDBN} will evaluate it as a
24229 script in the specified extension language.
24231 If this file does not exist, then @value{GDBN} will look for
24232 @var{script-name} file in all of the directories as specified below.
24234 Note that loading of these files requires an accordingly configured
24235 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24237 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24238 scripts normally according to its @file{.exe} filename. But if no scripts are
24239 found @value{GDBN} also tries script filenames matching the object file without
24240 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24241 is attempted on any platform. This makes the script filenames compatible
24242 between Unix and MS-Windows hosts.
24245 @anchor{set auto-load scripts-directory}
24246 @kindex set auto-load scripts-directory
24247 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24248 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24249 may be delimited by the host platform path separator in use
24250 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24252 Each entry here needs to be covered also by the security setting
24253 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24255 @anchor{with-auto-load-dir}
24256 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24257 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24258 configuration option @option{--with-auto-load-dir}.
24260 Any reference to @file{$debugdir} will get replaced by
24261 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24262 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24263 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24264 @file{$datadir} must be placed as a directory component --- either alone or
24265 delimited by @file{/} or @file{\} directory separators, depending on the host
24268 The list of directories uses path separator (@samp{:} on GNU and Unix
24269 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24270 to the @env{PATH} environment variable.
24272 @anchor{show auto-load scripts-directory}
24273 @kindex show auto-load scripts-directory
24274 @item show auto-load scripts-directory
24275 Show @value{GDBN} auto-loaded scripts location.
24277 @anchor{add-auto-load-scripts-directory}
24278 @kindex add-auto-load-scripts-directory
24279 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24280 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24281 Multiple entries may be delimited by the host platform path separator in use.
24284 @value{GDBN} does not track which files it has already auto-loaded this way.
24285 @value{GDBN} will load the associated script every time the corresponding
24286 @var{objfile} is opened.
24287 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24288 is evaluated more than once.
24290 @node dotdebug_gdb_scripts section
24291 @subsection The @code{.debug_gdb_scripts} section
24292 @cindex @code{.debug_gdb_scripts} section
24294 For systems using file formats like ELF and COFF,
24295 when @value{GDBN} loads a new object file
24296 it will look for a special section named @code{.debug_gdb_scripts}.
24297 If this section exists, its contents is a list of null-terminated entries
24298 specifying scripts to load. Each entry begins with a non-null prefix byte that
24299 specifies the kind of entry, typically the extension language and whether the
24300 script is in a file or inlined in @code{.debug_gdb_scripts}.
24302 The following entries are supported:
24305 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24306 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24307 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24308 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24311 @subsubsection Script File Entries
24313 If the entry specifies a file, @value{GDBN} will look for the file first
24314 in the current directory and then along the source search path
24315 (@pxref{Source Path, ,Specifying Source Directories}),
24316 except that @file{$cdir} is not searched, since the compilation
24317 directory is not relevant to scripts.
24319 File entries can be placed in section @code{.debug_gdb_scripts} with,
24320 for example, this GCC macro for Python scripts.
24323 /* Note: The "MS" section flags are to remove duplicates. */
24324 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24326 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24327 .byte 1 /* Python */\n\
24328 .asciz \"" script_name "\"\n\
24334 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24335 Then one can reference the macro in a header or source file like this:
24338 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24341 The script name may include directories if desired.
24343 Note that loading of this script file also requires accordingly configured
24344 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24346 If the macro invocation is put in a header, any application or library
24347 using this header will get a reference to the specified script,
24348 and with the use of @code{"MS"} attributes on the section, the linker
24349 will remove duplicates.
24351 @subsubsection Script Text Entries
24353 Script text entries allow to put the executable script in the entry
24354 itself instead of loading it from a file.
24355 The first line of the entry, everything after the prefix byte and up to
24356 the first newline (@code{0xa}) character, is the script name, and must not
24357 contain any kind of space character, e.g., spaces or tabs.
24358 The rest of the entry, up to the trailing null byte, is the script to
24359 execute in the specified language. The name needs to be unique among
24360 all script names, as @value{GDBN} executes each script only once based
24363 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24367 #include "symcat.h"
24368 #include "gdb/section-scripts.h"
24370 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24371 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24372 ".ascii \"gdb.inlined-script\\n\"\n"
24373 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24374 ".ascii \" def __init__ (self):\\n\"\n"
24375 ".ascii \" super (test_cmd, self).__init__ ("
24376 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24377 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24378 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24379 ".ascii \"test_cmd ()\\n\"\n"
24385 Loading of inlined scripts requires a properly configured
24386 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24387 The path to specify in @code{auto-load safe-path} is the path of the file
24388 containing the @code{.debug_gdb_scripts} section.
24390 @node Which flavor to choose?
24391 @subsection Which flavor to choose?
24393 Given the multiple ways of auto-loading extensions, it might not always
24394 be clear which one to choose. This section provides some guidance.
24397 Benefits of the @file{-gdb.@var{ext}} way:
24401 Can be used with file formats that don't support multiple sections.
24404 Ease of finding scripts for public libraries.
24406 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24407 in the source search path.
24408 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24409 isn't a source directory in which to find the script.
24412 Doesn't require source code additions.
24416 Benefits of the @code{.debug_gdb_scripts} way:
24420 Works with static linking.
24422 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24423 trigger their loading. When an application is statically linked the only
24424 objfile available is the executable, and it is cumbersome to attach all the
24425 scripts from all the input libraries to the executable's
24426 @file{-gdb.@var{ext}} script.
24429 Works with classes that are entirely inlined.
24431 Some classes can be entirely inlined, and thus there may not be an associated
24432 shared library to attach a @file{-gdb.@var{ext}} script to.
24435 Scripts needn't be copied out of the source tree.
24437 In some circumstances, apps can be built out of large collections of internal
24438 libraries, and the build infrastructure necessary to install the
24439 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24440 cumbersome. It may be easier to specify the scripts in the
24441 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24442 top of the source tree to the source search path.
24445 @node Multiple Extension Languages
24446 @section Multiple Extension Languages
24448 The Guile and Python extension languages do not share any state,
24449 and generally do not interfere with each other.
24450 There are some things to be aware of, however.
24452 @subsection Python comes first
24454 Python was @value{GDBN}'s first extension language, and to avoid breaking
24455 existing behaviour Python comes first. This is generally solved by the
24456 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24457 extension languages, and when it makes a call to an extension language,
24458 (say to pretty-print a value), it tries each in turn until an extension
24459 language indicates it has performed the request (e.g., has returned the
24460 pretty-printed form of a value).
24461 This extends to errors while performing such requests: If an error happens
24462 while, for example, trying to pretty-print an object then the error is
24463 reported and any following extension languages are not tried.
24466 @section Creating new spellings of existing commands
24467 @cindex aliases for commands
24469 It is often useful to define alternate spellings of existing commands.
24470 For example, if a new @value{GDBN} command defined in Python has
24471 a long name to type, it is handy to have an abbreviated version of it
24472 that involves less typing.
24474 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24475 of the @samp{step} command even though it is otherwise an ambiguous
24476 abbreviation of other commands like @samp{set} and @samp{show}.
24478 Aliases are also used to provide shortened or more common versions
24479 of multi-word commands. For example, @value{GDBN} provides the
24480 @samp{tty} alias of the @samp{set inferior-tty} command.
24482 You can define a new alias with the @samp{alias} command.
24487 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24491 @var{ALIAS} specifies the name of the new alias.
24492 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24495 @var{COMMAND} specifies the name of an existing command
24496 that is being aliased.
24498 The @samp{-a} option specifies that the new alias is an abbreviation
24499 of the command. Abbreviations are not shown in command
24500 lists displayed by the @samp{help} command.
24502 The @samp{--} option specifies the end of options,
24503 and is useful when @var{ALIAS} begins with a dash.
24505 Here is a simple example showing how to make an abbreviation
24506 of a command so that there is less to type.
24507 Suppose you were tired of typing @samp{disas}, the current
24508 shortest unambiguous abbreviation of the @samp{disassemble} command
24509 and you wanted an even shorter version named @samp{di}.
24510 The following will accomplish this.
24513 (gdb) alias -a di = disas
24516 Note that aliases are different from user-defined commands.
24517 With a user-defined command, you also need to write documentation
24518 for it with the @samp{document} command.
24519 An alias automatically picks up the documentation of the existing command.
24521 Here is an example where we make @samp{elms} an abbreviation of
24522 @samp{elements} in the @samp{set print elements} command.
24523 This is to show that you can make an abbreviation of any part
24527 (gdb) alias -a set print elms = set print elements
24528 (gdb) alias -a show print elms = show print elements
24529 (gdb) set p elms 20
24531 Limit on string chars or array elements to print is 200.
24534 Note that if you are defining an alias of a @samp{set} command,
24535 and you want to have an alias for the corresponding @samp{show}
24536 command, then you need to define the latter separately.
24538 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24539 @var{ALIAS}, just as they are normally.
24542 (gdb) alias -a set pr elms = set p ele
24545 Finally, here is an example showing the creation of a one word
24546 alias for a more complex command.
24547 This creates alias @samp{spe} of the command @samp{set print elements}.
24550 (gdb) alias spe = set print elements
24555 @chapter Command Interpreters
24556 @cindex command interpreters
24558 @value{GDBN} supports multiple command interpreters, and some command
24559 infrastructure to allow users or user interface writers to switch
24560 between interpreters or run commands in other interpreters.
24562 @value{GDBN} currently supports two command interpreters, the console
24563 interpreter (sometimes called the command-line interpreter or @sc{cli})
24564 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24565 describes both of these interfaces in great detail.
24567 By default, @value{GDBN} will start with the console interpreter.
24568 However, the user may choose to start @value{GDBN} with another
24569 interpreter by specifying the @option{-i} or @option{--interpreter}
24570 startup options. Defined interpreters include:
24574 @cindex console interpreter
24575 The traditional console or command-line interpreter. This is the most often
24576 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24577 @value{GDBN} will use this interpreter.
24580 @cindex mi interpreter
24581 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24582 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24583 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24587 @cindex mi2 interpreter
24588 The current @sc{gdb/mi} interface.
24591 @cindex mi1 interpreter
24592 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24596 @cindex invoke another interpreter
24597 The interpreter being used by @value{GDBN} may not be dynamically
24598 switched at runtime. Although possible, this could lead to a very
24599 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24600 enters the command "interpreter-set console" in a console view,
24601 @value{GDBN} would switch to using the console interpreter, rendering
24602 the IDE inoperable!
24604 @kindex interpreter-exec
24605 Although you may only choose a single interpreter at startup, you may execute
24606 commands in any interpreter from the current interpreter using the appropriate
24607 command. If you are running the console interpreter, simply use the
24608 @code{interpreter-exec} command:
24611 interpreter-exec mi "-data-list-register-names"
24614 @sc{gdb/mi} has a similar command, although it is only available in versions of
24615 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24618 @chapter @value{GDBN} Text User Interface
24620 @cindex Text User Interface
24623 * TUI Overview:: TUI overview
24624 * TUI Keys:: TUI key bindings
24625 * TUI Single Key Mode:: TUI single key mode
24626 * TUI Commands:: TUI-specific commands
24627 * TUI Configuration:: TUI configuration variables
24630 The @value{GDBN} Text User Interface (TUI) is a terminal
24631 interface which uses the @code{curses} library to show the source
24632 file, the assembly output, the program registers and @value{GDBN}
24633 commands in separate text windows. The TUI mode is supported only
24634 on platforms where a suitable version of the @code{curses} library
24637 The TUI mode is enabled by default when you invoke @value{GDBN} as
24638 @samp{@value{GDBP} -tui}.
24639 You can also switch in and out of TUI mode while @value{GDBN} runs by
24640 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24641 @xref{TUI Keys, ,TUI Key Bindings}.
24644 @section TUI Overview
24646 In TUI mode, @value{GDBN} can display several text windows:
24650 This window is the @value{GDBN} command window with the @value{GDBN}
24651 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24652 managed using readline.
24655 The source window shows the source file of the program. The current
24656 line and active breakpoints are displayed in this window.
24659 The assembly window shows the disassembly output of the program.
24662 This window shows the processor registers. Registers are highlighted
24663 when their values change.
24666 The source and assembly windows show the current program position
24667 by highlighting the current line and marking it with a @samp{>} marker.
24668 Breakpoints are indicated with two markers. The first marker
24669 indicates the breakpoint type:
24673 Breakpoint which was hit at least once.
24676 Breakpoint which was never hit.
24679 Hardware breakpoint which was hit at least once.
24682 Hardware breakpoint which was never hit.
24685 The second marker indicates whether the breakpoint is enabled or not:
24689 Breakpoint is enabled.
24692 Breakpoint is disabled.
24695 The source, assembly and register windows are updated when the current
24696 thread changes, when the frame changes, or when the program counter
24699 These windows are not all visible at the same time. The command
24700 window is always visible. The others can be arranged in several
24711 source and assembly,
24714 source and registers, or
24717 assembly and registers.
24720 A status line above the command window shows the following information:
24724 Indicates the current @value{GDBN} target.
24725 (@pxref{Targets, ,Specifying a Debugging Target}).
24728 Gives the current process or thread number.
24729 When no process is being debugged, this field is set to @code{No process}.
24732 Gives the current function name for the selected frame.
24733 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24734 When there is no symbol corresponding to the current program counter,
24735 the string @code{??} is displayed.
24738 Indicates the current line number for the selected frame.
24739 When the current line number is not known, the string @code{??} is displayed.
24742 Indicates the current program counter address.
24746 @section TUI Key Bindings
24747 @cindex TUI key bindings
24749 The TUI installs several key bindings in the readline keymaps
24750 @ifset SYSTEM_READLINE
24751 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24753 @ifclear SYSTEM_READLINE
24754 (@pxref{Command Line Editing}).
24756 The following key bindings are installed for both TUI mode and the
24757 @value{GDBN} standard mode.
24766 Enter or leave the TUI mode. When leaving the TUI mode,
24767 the curses window management stops and @value{GDBN} operates using
24768 its standard mode, writing on the terminal directly. When reentering
24769 the TUI mode, control is given back to the curses windows.
24770 The screen is then refreshed.
24774 Use a TUI layout with only one window. The layout will
24775 either be @samp{source} or @samp{assembly}. When the TUI mode
24776 is not active, it will switch to the TUI mode.
24778 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24782 Use a TUI layout with at least two windows. When the current
24783 layout already has two windows, the next layout with two windows is used.
24784 When a new layout is chosen, one window will always be common to the
24785 previous layout and the new one.
24787 Think of it as the Emacs @kbd{C-x 2} binding.
24791 Change the active window. The TUI associates several key bindings
24792 (like scrolling and arrow keys) with the active window. This command
24793 gives the focus to the next TUI window.
24795 Think of it as the Emacs @kbd{C-x o} binding.
24799 Switch in and out of the TUI SingleKey mode that binds single
24800 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24803 The following key bindings only work in the TUI mode:
24808 Scroll the active window one page up.
24812 Scroll the active window one page down.
24816 Scroll the active window one line up.
24820 Scroll the active window one line down.
24824 Scroll the active window one column left.
24828 Scroll the active window one column right.
24832 Refresh the screen.
24835 Because the arrow keys scroll the active window in the TUI mode, they
24836 are not available for their normal use by readline unless the command
24837 window has the focus. When another window is active, you must use
24838 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24839 and @kbd{C-f} to control the command window.
24841 @node TUI Single Key Mode
24842 @section TUI Single Key Mode
24843 @cindex TUI single key mode
24845 The TUI also provides a @dfn{SingleKey} mode, which binds several
24846 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24847 switch into this mode, where the following key bindings are used:
24850 @kindex c @r{(SingleKey TUI key)}
24854 @kindex d @r{(SingleKey TUI key)}
24858 @kindex f @r{(SingleKey TUI key)}
24862 @kindex n @r{(SingleKey TUI key)}
24866 @kindex q @r{(SingleKey TUI key)}
24868 exit the SingleKey mode.
24870 @kindex r @r{(SingleKey TUI key)}
24874 @kindex s @r{(SingleKey TUI key)}
24878 @kindex u @r{(SingleKey TUI key)}
24882 @kindex v @r{(SingleKey TUI key)}
24886 @kindex w @r{(SingleKey TUI key)}
24891 Other keys temporarily switch to the @value{GDBN} command prompt.
24892 The key that was pressed is inserted in the editing buffer so that
24893 it is possible to type most @value{GDBN} commands without interaction
24894 with the TUI SingleKey mode. Once the command is entered the TUI
24895 SingleKey mode is restored. The only way to permanently leave
24896 this mode is by typing @kbd{q} or @kbd{C-x s}.
24900 @section TUI-specific Commands
24901 @cindex TUI commands
24903 The TUI has specific commands to control the text windows.
24904 These commands are always available, even when @value{GDBN} is not in
24905 the TUI mode. When @value{GDBN} is in the standard mode, most
24906 of these commands will automatically switch to the TUI mode.
24908 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24909 terminal, or @value{GDBN} has been started with the machine interface
24910 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24911 these commands will fail with an error, because it would not be
24912 possible or desirable to enable curses window management.
24917 List and give the size of all displayed windows.
24921 Display the next layout.
24924 Display the previous layout.
24927 Display the source window only.
24930 Display the assembly window only.
24933 Display the source and assembly window.
24936 Display the register window together with the source or assembly window.
24940 Make the next window active for scrolling.
24943 Make the previous window active for scrolling.
24946 Make the source window active for scrolling.
24949 Make the assembly window active for scrolling.
24952 Make the register window active for scrolling.
24955 Make the command window active for scrolling.
24959 Refresh the screen. This is similar to typing @kbd{C-L}.
24961 @item tui reg float
24963 Show the floating point registers in the register window.
24965 @item tui reg general
24966 Show the general registers in the register window.
24969 Show the next register group. The list of register groups as well as
24970 their order is target specific. The predefined register groups are the
24971 following: @code{general}, @code{float}, @code{system}, @code{vector},
24972 @code{all}, @code{save}, @code{restore}.
24974 @item tui reg system
24975 Show the system registers in the register window.
24979 Update the source window and the current execution point.
24981 @item winheight @var{name} +@var{count}
24982 @itemx winheight @var{name} -@var{count}
24984 Change the height of the window @var{name} by @var{count}
24985 lines. Positive counts increase the height, while negative counts
24986 decrease it. The @var{name} parameter can be one of @code{src} (the
24987 source window), @code{cmd} (the command window), @code{asm} (the
24988 disassembly window), or @code{regs} (the register display window).
24990 @item tabset @var{nchars}
24992 Set the width of tab stops to be @var{nchars} characters. This
24993 setting affects the display of TAB characters in the source and
24997 @node TUI Configuration
24998 @section TUI Configuration Variables
24999 @cindex TUI configuration variables
25001 Several configuration variables control the appearance of TUI windows.
25004 @item set tui border-kind @var{kind}
25005 @kindex set tui border-kind
25006 Select the border appearance for the source, assembly and register windows.
25007 The possible values are the following:
25010 Use a space character to draw the border.
25013 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25016 Use the Alternate Character Set to draw the border. The border is
25017 drawn using character line graphics if the terminal supports them.
25020 @item set tui border-mode @var{mode}
25021 @kindex set tui border-mode
25022 @itemx set tui active-border-mode @var{mode}
25023 @kindex set tui active-border-mode
25024 Select the display attributes for the borders of the inactive windows
25025 or the active window. The @var{mode} can be one of the following:
25028 Use normal attributes to display the border.
25034 Use reverse video mode.
25037 Use half bright mode.
25039 @item half-standout
25040 Use half bright and standout mode.
25043 Use extra bright or bold mode.
25045 @item bold-standout
25046 Use extra bright or bold and standout mode.
25051 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25054 @cindex @sc{gnu} Emacs
25055 A special interface allows you to use @sc{gnu} Emacs to view (and
25056 edit) the source files for the program you are debugging with
25059 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25060 executable file you want to debug as an argument. This command starts
25061 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25062 created Emacs buffer.
25063 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25065 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25070 All ``terminal'' input and output goes through an Emacs buffer, called
25073 This applies both to @value{GDBN} commands and their output, and to the input
25074 and output done by the program you are debugging.
25076 This is useful because it means that you can copy the text of previous
25077 commands and input them again; you can even use parts of the output
25080 All the facilities of Emacs' Shell mode are available for interacting
25081 with your program. In particular, you can send signals the usual
25082 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25086 @value{GDBN} displays source code through Emacs.
25088 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25089 source file for that frame and puts an arrow (@samp{=>}) at the
25090 left margin of the current line. Emacs uses a separate buffer for
25091 source display, and splits the screen to show both your @value{GDBN} session
25094 Explicit @value{GDBN} @code{list} or search commands still produce output as
25095 usual, but you probably have no reason to use them from Emacs.
25098 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25099 a graphical mode, enabled by default, which provides further buffers
25100 that can control the execution and describe the state of your program.
25101 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25103 If you specify an absolute file name when prompted for the @kbd{M-x
25104 gdb} argument, then Emacs sets your current working directory to where
25105 your program resides. If you only specify the file name, then Emacs
25106 sets your current working directory to the directory associated
25107 with the previous buffer. In this case, @value{GDBN} may find your
25108 program by searching your environment's @code{PATH} variable, but on
25109 some operating systems it might not find the source. So, although the
25110 @value{GDBN} input and output session proceeds normally, the auxiliary
25111 buffer does not display the current source and line of execution.
25113 The initial working directory of @value{GDBN} is printed on the top
25114 line of the GUD buffer and this serves as a default for the commands
25115 that specify files for @value{GDBN} to operate on. @xref{Files,
25116 ,Commands to Specify Files}.
25118 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25119 need to call @value{GDBN} by a different name (for example, if you
25120 keep several configurations around, with different names) you can
25121 customize the Emacs variable @code{gud-gdb-command-name} to run the
25124 In the GUD buffer, you can use these special Emacs commands in
25125 addition to the standard Shell mode commands:
25129 Describe the features of Emacs' GUD Mode.
25132 Execute to another source line, like the @value{GDBN} @code{step} command; also
25133 update the display window to show the current file and location.
25136 Execute to next source line in this function, skipping all function
25137 calls, like the @value{GDBN} @code{next} command. Then update the display window
25138 to show the current file and location.
25141 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25142 display window accordingly.
25145 Execute until exit from the selected stack frame, like the @value{GDBN}
25146 @code{finish} command.
25149 Continue execution of your program, like the @value{GDBN} @code{continue}
25153 Go up the number of frames indicated by the numeric argument
25154 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25155 like the @value{GDBN} @code{up} command.
25158 Go down the number of frames indicated by the numeric argument, like the
25159 @value{GDBN} @code{down} command.
25162 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25163 tells @value{GDBN} to set a breakpoint on the source line point is on.
25165 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25166 separate frame which shows a backtrace when the GUD buffer is current.
25167 Move point to any frame in the stack and type @key{RET} to make it
25168 become the current frame and display the associated source in the
25169 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25170 selected frame become the current one. In graphical mode, the
25171 speedbar displays watch expressions.
25173 If you accidentally delete the source-display buffer, an easy way to get
25174 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25175 request a frame display; when you run under Emacs, this recreates
25176 the source buffer if necessary to show you the context of the current
25179 The source files displayed in Emacs are in ordinary Emacs buffers
25180 which are visiting the source files in the usual way. You can edit
25181 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25182 communicates with Emacs in terms of line numbers. If you add or
25183 delete lines from the text, the line numbers that @value{GDBN} knows cease
25184 to correspond properly with the code.
25186 A more detailed description of Emacs' interaction with @value{GDBN} is
25187 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25191 @chapter The @sc{gdb/mi} Interface
25193 @unnumberedsec Function and Purpose
25195 @cindex @sc{gdb/mi}, its purpose
25196 @sc{gdb/mi} is a line based machine oriented text interface to
25197 @value{GDBN} and is activated by specifying using the
25198 @option{--interpreter} command line option (@pxref{Mode Options}). It
25199 is specifically intended to support the development of systems which
25200 use the debugger as just one small component of a larger system.
25202 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25203 in the form of a reference manual.
25205 Note that @sc{gdb/mi} is still under construction, so some of the
25206 features described below are incomplete and subject to change
25207 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25209 @unnumberedsec Notation and Terminology
25211 @cindex notational conventions, for @sc{gdb/mi}
25212 This chapter uses the following notation:
25216 @code{|} separates two alternatives.
25219 @code{[ @var{something} ]} indicates that @var{something} is optional:
25220 it may or may not be given.
25223 @code{( @var{group} )*} means that @var{group} inside the parentheses
25224 may repeat zero or more times.
25227 @code{( @var{group} )+} means that @var{group} inside the parentheses
25228 may repeat one or more times.
25231 @code{"@var{string}"} means a literal @var{string}.
25235 @heading Dependencies
25239 * GDB/MI General Design::
25240 * GDB/MI Command Syntax::
25241 * GDB/MI Compatibility with CLI::
25242 * GDB/MI Development and Front Ends::
25243 * GDB/MI Output Records::
25244 * GDB/MI Simple Examples::
25245 * GDB/MI Command Description Format::
25246 * GDB/MI Breakpoint Commands::
25247 * GDB/MI Catchpoint Commands::
25248 * GDB/MI Program Context::
25249 * GDB/MI Thread Commands::
25250 * GDB/MI Ada Tasking Commands::
25251 * GDB/MI Program Execution::
25252 * GDB/MI Stack Manipulation::
25253 * GDB/MI Variable Objects::
25254 * GDB/MI Data Manipulation::
25255 * GDB/MI Tracepoint Commands::
25256 * GDB/MI Symbol Query::
25257 * GDB/MI File Commands::
25259 * GDB/MI Kod Commands::
25260 * GDB/MI Memory Overlay Commands::
25261 * GDB/MI Signal Handling Commands::
25263 * GDB/MI Target Manipulation::
25264 * GDB/MI File Transfer Commands::
25265 * GDB/MI Ada Exceptions Commands::
25266 * GDB/MI Support Commands::
25267 * GDB/MI Miscellaneous Commands::
25270 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25271 @node GDB/MI General Design
25272 @section @sc{gdb/mi} General Design
25273 @cindex GDB/MI General Design
25275 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25276 parts---commands sent to @value{GDBN}, responses to those commands
25277 and notifications. Each command results in exactly one response,
25278 indicating either successful completion of the command, or an error.
25279 For the commands that do not resume the target, the response contains the
25280 requested information. For the commands that resume the target, the
25281 response only indicates whether the target was successfully resumed.
25282 Notifications is the mechanism for reporting changes in the state of the
25283 target, or in @value{GDBN} state, that cannot conveniently be associated with
25284 a command and reported as part of that command response.
25286 The important examples of notifications are:
25290 Exec notifications. These are used to report changes in
25291 target state---when a target is resumed, or stopped. It would not
25292 be feasible to include this information in response of resuming
25293 commands, because one resume commands can result in multiple events in
25294 different threads. Also, quite some time may pass before any event
25295 happens in the target, while a frontend needs to know whether the resuming
25296 command itself was successfully executed.
25299 Console output, and status notifications. Console output
25300 notifications are used to report output of CLI commands, as well as
25301 diagnostics for other commands. Status notifications are used to
25302 report the progress of a long-running operation. Naturally, including
25303 this information in command response would mean no output is produced
25304 until the command is finished, which is undesirable.
25307 General notifications. Commands may have various side effects on
25308 the @value{GDBN} or target state beyond their official purpose. For example,
25309 a command may change the selected thread. Although such changes can
25310 be included in command response, using notification allows for more
25311 orthogonal frontend design.
25315 There's no guarantee that whenever an MI command reports an error,
25316 @value{GDBN} or the target are in any specific state, and especially,
25317 the state is not reverted to the state before the MI command was
25318 processed. Therefore, whenever an MI command results in an error,
25319 we recommend that the frontend refreshes all the information shown in
25320 the user interface.
25324 * Context management::
25325 * Asynchronous and non-stop modes::
25329 @node Context management
25330 @subsection Context management
25332 @subsubsection Threads and Frames
25334 In most cases when @value{GDBN} accesses the target, this access is
25335 done in context of a specific thread and frame (@pxref{Frames}).
25336 Often, even when accessing global data, the target requires that a thread
25337 be specified. The CLI interface maintains the selected thread and frame,
25338 and supplies them to target on each command. This is convenient,
25339 because a command line user would not want to specify that information
25340 explicitly on each command, and because user interacts with
25341 @value{GDBN} via a single terminal, so no confusion is possible as
25342 to what thread and frame are the current ones.
25344 In the case of MI, the concept of selected thread and frame is less
25345 useful. First, a frontend can easily remember this information
25346 itself. Second, a graphical frontend can have more than one window,
25347 each one used for debugging a different thread, and the frontend might
25348 want to access additional threads for internal purposes. This
25349 increases the risk that by relying on implicitly selected thread, the
25350 frontend may be operating on a wrong one. Therefore, each MI command
25351 should explicitly specify which thread and frame to operate on. To
25352 make it possible, each MI command accepts the @samp{--thread} and
25353 @samp{--frame} options, the value to each is @value{GDBN} identifier
25354 for thread and frame to operate on.
25356 Usually, each top-level window in a frontend allows the user to select
25357 a thread and a frame, and remembers the user selection for further
25358 operations. However, in some cases @value{GDBN} may suggest that the
25359 current thread be changed. For example, when stopping on a breakpoint
25360 it is reasonable to switch to the thread where breakpoint is hit. For
25361 another example, if the user issues the CLI @samp{thread} command via
25362 the frontend, it is desirable to change the frontend's selected thread to the
25363 one specified by user. @value{GDBN} communicates the suggestion to
25364 change current thread using the @samp{=thread-selected} notification.
25365 No such notification is available for the selected frame at the moment.
25367 Note that historically, MI shares the selected thread with CLI, so
25368 frontends used the @code{-thread-select} to execute commands in the
25369 right context. However, getting this to work right is cumbersome. The
25370 simplest way is for frontend to emit @code{-thread-select} command
25371 before every command. This doubles the number of commands that need
25372 to be sent. The alternative approach is to suppress @code{-thread-select}
25373 if the selected thread in @value{GDBN} is supposed to be identical to the
25374 thread the frontend wants to operate on. However, getting this
25375 optimization right can be tricky. In particular, if the frontend
25376 sends several commands to @value{GDBN}, and one of the commands changes the
25377 selected thread, then the behaviour of subsequent commands will
25378 change. So, a frontend should either wait for response from such
25379 problematic commands, or explicitly add @code{-thread-select} for
25380 all subsequent commands. No frontend is known to do this exactly
25381 right, so it is suggested to just always pass the @samp{--thread} and
25382 @samp{--frame} options.
25384 @subsubsection Language
25386 The execution of several commands depends on which language is selected.
25387 By default, the current language (@pxref{show language}) is used.
25388 But for commands known to be language-sensitive, it is recommended
25389 to use the @samp{--language} option. This option takes one argument,
25390 which is the name of the language to use while executing the command.
25394 -data-evaluate-expression --language c "sizeof (void*)"
25399 The valid language names are the same names accepted by the
25400 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25401 @samp{local} or @samp{unknown}.
25403 @node Asynchronous and non-stop modes
25404 @subsection Asynchronous command execution and non-stop mode
25406 On some targets, @value{GDBN} is capable of processing MI commands
25407 even while the target is running. This is called @dfn{asynchronous
25408 command execution} (@pxref{Background Execution}). The frontend may
25409 specify a preferrence for asynchronous execution using the
25410 @code{-gdb-set mi-async 1} command, which should be emitted before
25411 either running the executable or attaching to the target. After the
25412 frontend has started the executable or attached to the target, it can
25413 find if asynchronous execution is enabled using the
25414 @code{-list-target-features} command.
25417 @item -gdb-set mi-async on
25418 @item -gdb-set mi-async off
25419 Set whether MI is in asynchronous mode.
25421 When @code{off}, which is the default, MI execution commands (e.g.,
25422 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25423 for the program to stop before processing further commands.
25425 When @code{on}, MI execution commands are background execution
25426 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25427 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25428 MI commands even while the target is running.
25430 @item -gdb-show mi-async
25431 Show whether MI asynchronous mode is enabled.
25434 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25435 @code{target-async} instead of @code{mi-async}, and it had the effect
25436 of both putting MI in asynchronous mode and making CLI background
25437 commands possible. CLI background commands are now always possible
25438 ``out of the box'' if the target supports them. The old spelling is
25439 kept as a deprecated alias for backwards compatibility.
25441 Even if @value{GDBN} can accept a command while target is running,
25442 many commands that access the target do not work when the target is
25443 running. Therefore, asynchronous command execution is most useful
25444 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25445 it is possible to examine the state of one thread, while other threads
25448 When a given thread is running, MI commands that try to access the
25449 target in the context of that thread may not work, or may work only on
25450 some targets. In particular, commands that try to operate on thread's
25451 stack will not work, on any target. Commands that read memory, or
25452 modify breakpoints, may work or not work, depending on the target. Note
25453 that even commands that operate on global state, such as @code{print},
25454 @code{set}, and breakpoint commands, still access the target in the
25455 context of a specific thread, so frontend should try to find a
25456 stopped thread and perform the operation on that thread (using the
25457 @samp{--thread} option).
25459 Which commands will work in the context of a running thread is
25460 highly target dependent. However, the two commands
25461 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25462 to find the state of a thread, will always work.
25464 @node Thread groups
25465 @subsection Thread groups
25466 @value{GDBN} may be used to debug several processes at the same time.
25467 On some platfroms, @value{GDBN} may support debugging of several
25468 hardware systems, each one having several cores with several different
25469 processes running on each core. This section describes the MI
25470 mechanism to support such debugging scenarios.
25472 The key observation is that regardless of the structure of the
25473 target, MI can have a global list of threads, because most commands that
25474 accept the @samp{--thread} option do not need to know what process that
25475 thread belongs to. Therefore, it is not necessary to introduce
25476 neither additional @samp{--process} option, nor an notion of the
25477 current process in the MI interface. The only strictly new feature
25478 that is required is the ability to find how the threads are grouped
25481 To allow the user to discover such grouping, and to support arbitrary
25482 hierarchy of machines/cores/processes, MI introduces the concept of a
25483 @dfn{thread group}. Thread group is a collection of threads and other
25484 thread groups. A thread group always has a string identifier, a type,
25485 and may have additional attributes specific to the type. A new
25486 command, @code{-list-thread-groups}, returns the list of top-level
25487 thread groups, which correspond to processes that @value{GDBN} is
25488 debugging at the moment. By passing an identifier of a thread group
25489 to the @code{-list-thread-groups} command, it is possible to obtain
25490 the members of specific thread group.
25492 To allow the user to easily discover processes, and other objects, he
25493 wishes to debug, a concept of @dfn{available thread group} is
25494 introduced. Available thread group is an thread group that
25495 @value{GDBN} is not debugging, but that can be attached to, using the
25496 @code{-target-attach} command. The list of available top-level thread
25497 groups can be obtained using @samp{-list-thread-groups --available}.
25498 In general, the content of a thread group may be only retrieved only
25499 after attaching to that thread group.
25501 Thread groups are related to inferiors (@pxref{Inferiors and
25502 Programs}). Each inferior corresponds to a thread group of a special
25503 type @samp{process}, and some additional operations are permitted on
25504 such thread groups.
25506 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25507 @node GDB/MI Command Syntax
25508 @section @sc{gdb/mi} Command Syntax
25511 * GDB/MI Input Syntax::
25512 * GDB/MI Output Syntax::
25515 @node GDB/MI Input Syntax
25516 @subsection @sc{gdb/mi} Input Syntax
25518 @cindex input syntax for @sc{gdb/mi}
25519 @cindex @sc{gdb/mi}, input syntax
25521 @item @var{command} @expansion{}
25522 @code{@var{cli-command} | @var{mi-command}}
25524 @item @var{cli-command} @expansion{}
25525 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25526 @var{cli-command} is any existing @value{GDBN} CLI command.
25528 @item @var{mi-command} @expansion{}
25529 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25530 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25532 @item @var{token} @expansion{}
25533 "any sequence of digits"
25535 @item @var{option} @expansion{}
25536 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25538 @item @var{parameter} @expansion{}
25539 @code{@var{non-blank-sequence} | @var{c-string}}
25541 @item @var{operation} @expansion{}
25542 @emph{any of the operations described in this chapter}
25544 @item @var{non-blank-sequence} @expansion{}
25545 @emph{anything, provided it doesn't contain special characters such as
25546 "-", @var{nl}, """ and of course " "}
25548 @item @var{c-string} @expansion{}
25549 @code{""" @var{seven-bit-iso-c-string-content} """}
25551 @item @var{nl} @expansion{}
25560 The CLI commands are still handled by the @sc{mi} interpreter; their
25561 output is described below.
25564 The @code{@var{token}}, when present, is passed back when the command
25568 Some @sc{mi} commands accept optional arguments as part of the parameter
25569 list. Each option is identified by a leading @samp{-} (dash) and may be
25570 followed by an optional argument parameter. Options occur first in the
25571 parameter list and can be delimited from normal parameters using
25572 @samp{--} (this is useful when some parameters begin with a dash).
25579 We want easy access to the existing CLI syntax (for debugging).
25582 We want it to be easy to spot a @sc{mi} operation.
25585 @node GDB/MI Output Syntax
25586 @subsection @sc{gdb/mi} Output Syntax
25588 @cindex output syntax of @sc{gdb/mi}
25589 @cindex @sc{gdb/mi}, output syntax
25590 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25591 followed, optionally, by a single result record. This result record
25592 is for the most recent command. The sequence of output records is
25593 terminated by @samp{(gdb)}.
25595 If an input command was prefixed with a @code{@var{token}} then the
25596 corresponding output for that command will also be prefixed by that same
25600 @item @var{output} @expansion{}
25601 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25603 @item @var{result-record} @expansion{}
25604 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25606 @item @var{out-of-band-record} @expansion{}
25607 @code{@var{async-record} | @var{stream-record}}
25609 @item @var{async-record} @expansion{}
25610 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25612 @item @var{exec-async-output} @expansion{}
25613 @code{[ @var{token} ] "*" @var{async-output nl}}
25615 @item @var{status-async-output} @expansion{}
25616 @code{[ @var{token} ] "+" @var{async-output nl}}
25618 @item @var{notify-async-output} @expansion{}
25619 @code{[ @var{token} ] "=" @var{async-output nl}}
25621 @item @var{async-output} @expansion{}
25622 @code{@var{async-class} ( "," @var{result} )*}
25624 @item @var{result-class} @expansion{}
25625 @code{"done" | "running" | "connected" | "error" | "exit"}
25627 @item @var{async-class} @expansion{}
25628 @code{"stopped" | @var{others}} (where @var{others} will be added
25629 depending on the needs---this is still in development).
25631 @item @var{result} @expansion{}
25632 @code{ @var{variable} "=" @var{value}}
25634 @item @var{variable} @expansion{}
25635 @code{ @var{string} }
25637 @item @var{value} @expansion{}
25638 @code{ @var{const} | @var{tuple} | @var{list} }
25640 @item @var{const} @expansion{}
25641 @code{@var{c-string}}
25643 @item @var{tuple} @expansion{}
25644 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25646 @item @var{list} @expansion{}
25647 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25648 @var{result} ( "," @var{result} )* "]" }
25650 @item @var{stream-record} @expansion{}
25651 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25653 @item @var{console-stream-output} @expansion{}
25654 @code{"~" @var{c-string nl}}
25656 @item @var{target-stream-output} @expansion{}
25657 @code{"@@" @var{c-string nl}}
25659 @item @var{log-stream-output} @expansion{}
25660 @code{"&" @var{c-string nl}}
25662 @item @var{nl} @expansion{}
25665 @item @var{token} @expansion{}
25666 @emph{any sequence of digits}.
25674 All output sequences end in a single line containing a period.
25677 The @code{@var{token}} is from the corresponding request. Note that
25678 for all async output, while the token is allowed by the grammar and
25679 may be output by future versions of @value{GDBN} for select async
25680 output messages, it is generally omitted. Frontends should treat
25681 all async output as reporting general changes in the state of the
25682 target and there should be no need to associate async output to any
25686 @cindex status output in @sc{gdb/mi}
25687 @var{status-async-output} contains on-going status information about the
25688 progress of a slow operation. It can be discarded. All status output is
25689 prefixed by @samp{+}.
25692 @cindex async output in @sc{gdb/mi}
25693 @var{exec-async-output} contains asynchronous state change on the target
25694 (stopped, started, disappeared). All async output is prefixed by
25698 @cindex notify output in @sc{gdb/mi}
25699 @var{notify-async-output} contains supplementary information that the
25700 client should handle (e.g., a new breakpoint information). All notify
25701 output is prefixed by @samp{=}.
25704 @cindex console output in @sc{gdb/mi}
25705 @var{console-stream-output} is output that should be displayed as is in the
25706 console. It is the textual response to a CLI command. All the console
25707 output is prefixed by @samp{~}.
25710 @cindex target output in @sc{gdb/mi}
25711 @var{target-stream-output} is the output produced by the target program.
25712 All the target output is prefixed by @samp{@@}.
25715 @cindex log output in @sc{gdb/mi}
25716 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25717 instance messages that should be displayed as part of an error log. All
25718 the log output is prefixed by @samp{&}.
25721 @cindex list output in @sc{gdb/mi}
25722 New @sc{gdb/mi} commands should only output @var{lists} containing
25728 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25729 details about the various output records.
25731 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25732 @node GDB/MI Compatibility with CLI
25733 @section @sc{gdb/mi} Compatibility with CLI
25735 @cindex compatibility, @sc{gdb/mi} and CLI
25736 @cindex @sc{gdb/mi}, compatibility with CLI
25738 For the developers convenience CLI commands can be entered directly,
25739 but there may be some unexpected behaviour. For example, commands
25740 that query the user will behave as if the user replied yes, breakpoint
25741 command lists are not executed and some CLI commands, such as
25742 @code{if}, @code{when} and @code{define}, prompt for further input with
25743 @samp{>}, which is not valid MI output.
25745 This feature may be removed at some stage in the future and it is
25746 recommended that front ends use the @code{-interpreter-exec} command
25747 (@pxref{-interpreter-exec}).
25749 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25750 @node GDB/MI Development and Front Ends
25751 @section @sc{gdb/mi} Development and Front Ends
25752 @cindex @sc{gdb/mi} development
25754 The application which takes the MI output and presents the state of the
25755 program being debugged to the user is called a @dfn{front end}.
25757 Although @sc{gdb/mi} is still incomplete, it is currently being used
25758 by a variety of front ends to @value{GDBN}. This makes it difficult
25759 to introduce new functionality without breaking existing usage. This
25760 section tries to minimize the problems by describing how the protocol
25763 Some changes in MI need not break a carefully designed front end, and
25764 for these the MI version will remain unchanged. The following is a
25765 list of changes that may occur within one level, so front ends should
25766 parse MI output in a way that can handle them:
25770 New MI commands may be added.
25773 New fields may be added to the output of any MI command.
25776 The range of values for fields with specified values, e.g.,
25777 @code{in_scope} (@pxref{-var-update}) may be extended.
25779 @c The format of field's content e.g type prefix, may change so parse it
25780 @c at your own risk. Yes, in general?
25782 @c The order of fields may change? Shouldn't really matter but it might
25783 @c resolve inconsistencies.
25786 If the changes are likely to break front ends, the MI version level
25787 will be increased by one. This will allow the front end to parse the
25788 output according to the MI version. Apart from mi0, new versions of
25789 @value{GDBN} will not support old versions of MI and it will be the
25790 responsibility of the front end to work with the new one.
25792 @c Starting with mi3, add a new command -mi-version that prints the MI
25795 The best way to avoid unexpected changes in MI that might break your front
25796 end is to make your project known to @value{GDBN} developers and
25797 follow development on @email{gdb@@sourceware.org} and
25798 @email{gdb-patches@@sourceware.org}.
25799 @cindex mailing lists
25801 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25802 @node GDB/MI Output Records
25803 @section @sc{gdb/mi} Output Records
25806 * GDB/MI Result Records::
25807 * GDB/MI Stream Records::
25808 * GDB/MI Async Records::
25809 * GDB/MI Breakpoint Information::
25810 * GDB/MI Frame Information::
25811 * GDB/MI Thread Information::
25812 * GDB/MI Ada Exception Information::
25815 @node GDB/MI Result Records
25816 @subsection @sc{gdb/mi} Result Records
25818 @cindex result records in @sc{gdb/mi}
25819 @cindex @sc{gdb/mi}, result records
25820 In addition to a number of out-of-band notifications, the response to a
25821 @sc{gdb/mi} command includes one of the following result indications:
25825 @item "^done" [ "," @var{results} ]
25826 The synchronous operation was successful, @code{@var{results}} are the return
25831 This result record is equivalent to @samp{^done}. Historically, it
25832 was output instead of @samp{^done} if the command has resumed the
25833 target. This behaviour is maintained for backward compatibility, but
25834 all frontends should treat @samp{^done} and @samp{^running}
25835 identically and rely on the @samp{*running} output record to determine
25836 which threads are resumed.
25840 @value{GDBN} has connected to a remote target.
25842 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
25844 The operation failed. The @code{msg=@var{c-string}} variable contains
25845 the corresponding error message.
25847 If present, the @code{code=@var{c-string}} variable provides an error
25848 code on which consumers can rely on to detect the corresponding
25849 error condition. At present, only one error code is defined:
25852 @item "undefined-command"
25853 Indicates that the command causing the error does not exist.
25858 @value{GDBN} has terminated.
25862 @node GDB/MI Stream Records
25863 @subsection @sc{gdb/mi} Stream Records
25865 @cindex @sc{gdb/mi}, stream records
25866 @cindex stream records in @sc{gdb/mi}
25867 @value{GDBN} internally maintains a number of output streams: the console, the
25868 target, and the log. The output intended for each of these streams is
25869 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25871 Each stream record begins with a unique @dfn{prefix character} which
25872 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25873 Syntax}). In addition to the prefix, each stream record contains a
25874 @code{@var{string-output}}. This is either raw text (with an implicit new
25875 line) or a quoted C string (which does not contain an implicit newline).
25878 @item "~" @var{string-output}
25879 The console output stream contains text that should be displayed in the
25880 CLI console window. It contains the textual responses to CLI commands.
25882 @item "@@" @var{string-output}
25883 The target output stream contains any textual output from the running
25884 target. This is only present when GDB's event loop is truly
25885 asynchronous, which is currently only the case for remote targets.
25887 @item "&" @var{string-output}
25888 The log stream contains debugging messages being produced by @value{GDBN}'s
25892 @node GDB/MI Async Records
25893 @subsection @sc{gdb/mi} Async Records
25895 @cindex async records in @sc{gdb/mi}
25896 @cindex @sc{gdb/mi}, async records
25897 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25898 additional changes that have occurred. Those changes can either be a
25899 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25900 target activity (e.g., target stopped).
25902 The following is the list of possible async records:
25906 @item *running,thread-id="@var{thread}"
25907 The target is now running. The @var{thread} field tells which
25908 specific thread is now running, and can be @samp{all} if all threads
25909 are running. The frontend should assume that no interaction with a
25910 running thread is possible after this notification is produced.
25911 The frontend should not assume that this notification is output
25912 only once for any command. @value{GDBN} may emit this notification
25913 several times, either for different threads, because it cannot resume
25914 all threads together, or even for a single thread, if the thread must
25915 be stepped though some code before letting it run freely.
25917 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25918 The target has stopped. The @var{reason} field can have one of the
25922 @item breakpoint-hit
25923 A breakpoint was reached.
25924 @item watchpoint-trigger
25925 A watchpoint was triggered.
25926 @item read-watchpoint-trigger
25927 A read watchpoint was triggered.
25928 @item access-watchpoint-trigger
25929 An access watchpoint was triggered.
25930 @item function-finished
25931 An -exec-finish or similar CLI command was accomplished.
25932 @item location-reached
25933 An -exec-until or similar CLI command was accomplished.
25934 @item watchpoint-scope
25935 A watchpoint has gone out of scope.
25936 @item end-stepping-range
25937 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25938 similar CLI command was accomplished.
25939 @item exited-signalled
25940 The inferior exited because of a signal.
25942 The inferior exited.
25943 @item exited-normally
25944 The inferior exited normally.
25945 @item signal-received
25946 A signal was received by the inferior.
25948 The inferior has stopped due to a library being loaded or unloaded.
25949 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
25950 set or when a @code{catch load} or @code{catch unload} catchpoint is
25951 in use (@pxref{Set Catchpoints}).
25953 The inferior has forked. This is reported when @code{catch fork}
25954 (@pxref{Set Catchpoints}) has been used.
25956 The inferior has vforked. This is reported in when @code{catch vfork}
25957 (@pxref{Set Catchpoints}) has been used.
25958 @item syscall-entry
25959 The inferior entered a system call. This is reported when @code{catch
25960 syscall} (@pxref{Set Catchpoints}) has been used.
25961 @item syscall-return
25962 The inferior returned from a system call. This is reported when
25963 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
25965 The inferior called @code{exec}. This is reported when @code{catch exec}
25966 (@pxref{Set Catchpoints}) has been used.
25969 The @var{id} field identifies the thread that directly caused the stop
25970 -- for example by hitting a breakpoint. Depending on whether all-stop
25971 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25972 stop all threads, or only the thread that directly triggered the stop.
25973 If all threads are stopped, the @var{stopped} field will have the
25974 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25975 field will be a list of thread identifiers. Presently, this list will
25976 always include a single thread, but frontend should be prepared to see
25977 several threads in the list. The @var{core} field reports the
25978 processor core on which the stop event has happened. This field may be absent
25979 if such information is not available.
25981 @item =thread-group-added,id="@var{id}"
25982 @itemx =thread-group-removed,id="@var{id}"
25983 A thread group was either added or removed. The @var{id} field
25984 contains the @value{GDBN} identifier of the thread group. When a thread
25985 group is added, it generally might not be associated with a running
25986 process. When a thread group is removed, its id becomes invalid and
25987 cannot be used in any way.
25989 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25990 A thread group became associated with a running program,
25991 either because the program was just started or the thread group
25992 was attached to a program. The @var{id} field contains the
25993 @value{GDBN} identifier of the thread group. The @var{pid} field
25994 contains process identifier, specific to the operating system.
25996 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25997 A thread group is no longer associated with a running program,
25998 either because the program has exited, or because it was detached
25999 from. The @var{id} field contains the @value{GDBN} identifier of the
26000 thread group. The @var{code} field is the exit code of the inferior; it exists
26001 only when the inferior exited with some code.
26003 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26004 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26005 A thread either was created, or has exited. The @var{id} field
26006 contains the @value{GDBN} identifier of the thread. The @var{gid}
26007 field identifies the thread group this thread belongs to.
26009 @item =thread-selected,id="@var{id}"
26010 Informs that the selected thread was changed as result of the last
26011 command. This notification is not emitted as result of @code{-thread-select}
26012 command but is emitted whenever an MI command that is not documented
26013 to change the selected thread actually changes it. In particular,
26014 invoking, directly or indirectly (via user-defined command), the CLI
26015 @code{thread} command, will generate this notification.
26017 We suggest that in response to this notification, front ends
26018 highlight the selected thread and cause subsequent commands to apply to
26021 @item =library-loaded,...
26022 Reports that a new library file was loaded by the program. This
26023 notification has 4 fields---@var{id}, @var{target-name},
26024 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26025 opaque identifier of the library. For remote debugging case,
26026 @var{target-name} and @var{host-name} fields give the name of the
26027 library file on the target, and on the host respectively. For native
26028 debugging, both those fields have the same value. The
26029 @var{symbols-loaded} field is emitted only for backward compatibility
26030 and should not be relied on to convey any useful information. The
26031 @var{thread-group} field, if present, specifies the id of the thread
26032 group in whose context the library was loaded. If the field is
26033 absent, it means the library was loaded in the context of all present
26036 @item =library-unloaded,...
26037 Reports that a library was unloaded by the program. This notification
26038 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26039 the same meaning as for the @code{=library-loaded} notification.
26040 The @var{thread-group} field, if present, specifies the id of the
26041 thread group in whose context the library was unloaded. If the field is
26042 absent, it means the library was unloaded in the context of all present
26045 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26046 @itemx =traceframe-changed,end
26047 Reports that the trace frame was changed and its new number is
26048 @var{tfnum}. The number of the tracepoint associated with this trace
26049 frame is @var{tpnum}.
26051 @item =tsv-created,name=@var{name},initial=@var{initial}
26052 Reports that the new trace state variable @var{name} is created with
26053 initial value @var{initial}.
26055 @item =tsv-deleted,name=@var{name}
26056 @itemx =tsv-deleted
26057 Reports that the trace state variable @var{name} is deleted or all
26058 trace state variables are deleted.
26060 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26061 Reports that the trace state variable @var{name} is modified with
26062 the initial value @var{initial}. The current value @var{current} of
26063 trace state variable is optional and is reported if the current
26064 value of trace state variable is known.
26066 @item =breakpoint-created,bkpt=@{...@}
26067 @itemx =breakpoint-modified,bkpt=@{...@}
26068 @itemx =breakpoint-deleted,id=@var{number}
26069 Reports that a breakpoint was created, modified, or deleted,
26070 respectively. Only user-visible breakpoints are reported to the MI
26073 The @var{bkpt} argument is of the same form as returned by the various
26074 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26075 @var{number} is the ordinal number of the breakpoint.
26077 Note that if a breakpoint is emitted in the result record of a
26078 command, then it will not also be emitted in an async record.
26080 @item =record-started,thread-group="@var{id}"
26081 @itemx =record-stopped,thread-group="@var{id}"
26082 Execution log recording was either started or stopped on an
26083 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26084 group corresponding to the affected inferior.
26086 @item =cmd-param-changed,param=@var{param},value=@var{value}
26087 Reports that a parameter of the command @code{set @var{param}} is
26088 changed to @var{value}. In the multi-word @code{set} command,
26089 the @var{param} is the whole parameter list to @code{set} command.
26090 For example, In command @code{set check type on}, @var{param}
26091 is @code{check type} and @var{value} is @code{on}.
26093 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26094 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26095 written in an inferior. The @var{id} is the identifier of the
26096 thread group corresponding to the affected inferior. The optional
26097 @code{type="code"} part is reported if the memory written to holds
26101 @node GDB/MI Breakpoint Information
26102 @subsection @sc{gdb/mi} Breakpoint Information
26104 When @value{GDBN} reports information about a breakpoint, a
26105 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26110 The breakpoint number. For a breakpoint that represents one location
26111 of a multi-location breakpoint, this will be a dotted pair, like
26115 The type of the breakpoint. For ordinary breakpoints this will be
26116 @samp{breakpoint}, but many values are possible.
26119 If the type of the breakpoint is @samp{catchpoint}, then this
26120 indicates the exact type of catchpoint.
26123 This is the breakpoint disposition---either @samp{del}, meaning that
26124 the breakpoint will be deleted at the next stop, or @samp{keep},
26125 meaning that the breakpoint will not be deleted.
26128 This indicates whether the breakpoint is enabled, in which case the
26129 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26130 Note that this is not the same as the field @code{enable}.
26133 The address of the breakpoint. This may be a hexidecimal number,
26134 giving the address; or the string @samp{<PENDING>}, for a pending
26135 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26136 multiple locations. This field will not be present if no address can
26137 be determined. For example, a watchpoint does not have an address.
26140 If known, the function in which the breakpoint appears.
26141 If not known, this field is not present.
26144 The name of the source file which contains this function, if known.
26145 If not known, this field is not present.
26148 The full file name of the source file which contains this function, if
26149 known. If not known, this field is not present.
26152 The line number at which this breakpoint appears, if known.
26153 If not known, this field is not present.
26156 If the source file is not known, this field may be provided. If
26157 provided, this holds the address of the breakpoint, possibly followed
26161 If this breakpoint is pending, this field is present and holds the
26162 text used to set the breakpoint, as entered by the user.
26165 Where this breakpoint's condition is evaluated, either @samp{host} or
26169 If this is a thread-specific breakpoint, then this identifies the
26170 thread in which the breakpoint can trigger.
26173 If this breakpoint is restricted to a particular Ada task, then this
26174 field will hold the task identifier.
26177 If the breakpoint is conditional, this is the condition expression.
26180 The ignore count of the breakpoint.
26183 The enable count of the breakpoint.
26185 @item traceframe-usage
26188 @item static-tracepoint-marker-string-id
26189 For a static tracepoint, the name of the static tracepoint marker.
26192 For a masked watchpoint, this is the mask.
26195 A tracepoint's pass count.
26197 @item original-location
26198 The location of the breakpoint as originally specified by the user.
26199 This field is optional.
26202 The number of times the breakpoint has been hit.
26205 This field is only given for tracepoints. This is either @samp{y},
26206 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26210 Some extra data, the exact contents of which are type-dependent.
26214 For example, here is what the output of @code{-break-insert}
26215 (@pxref{GDB/MI Breakpoint Commands}) might be:
26218 -> -break-insert main
26219 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26220 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26221 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26226 @node GDB/MI Frame Information
26227 @subsection @sc{gdb/mi} Frame Information
26229 Response from many MI commands includes an information about stack
26230 frame. This information is a tuple that may have the following
26235 The level of the stack frame. The innermost frame has the level of
26236 zero. This field is always present.
26239 The name of the function corresponding to the frame. This field may
26240 be absent if @value{GDBN} is unable to determine the function name.
26243 The code address for the frame. This field is always present.
26246 The name of the source files that correspond to the frame's code
26247 address. This field may be absent.
26250 The source line corresponding to the frames' code address. This field
26254 The name of the binary file (either executable or shared library) the
26255 corresponds to the frame's code address. This field may be absent.
26259 @node GDB/MI Thread Information
26260 @subsection @sc{gdb/mi} Thread Information
26262 Whenever @value{GDBN} has to report an information about a thread, it
26263 uses a tuple with the following fields:
26267 The numeric id assigned to the thread by @value{GDBN}. This field is
26271 Target-specific string identifying the thread. This field is always present.
26274 Additional information about the thread provided by the target.
26275 It is supposed to be human-readable and not interpreted by the
26276 frontend. This field is optional.
26279 Either @samp{stopped} or @samp{running}, depending on whether the
26280 thread is presently running. This field is always present.
26283 The value of this field is an integer number of the processor core the
26284 thread was last seen on. This field is optional.
26287 @node GDB/MI Ada Exception Information
26288 @subsection @sc{gdb/mi} Ada Exception Information
26290 Whenever a @code{*stopped} record is emitted because the program
26291 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26292 @value{GDBN} provides the name of the exception that was raised via
26293 the @code{exception-name} field.
26295 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26296 @node GDB/MI Simple Examples
26297 @section Simple Examples of @sc{gdb/mi} Interaction
26298 @cindex @sc{gdb/mi}, simple examples
26300 This subsection presents several simple examples of interaction using
26301 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26302 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26303 the output received from @sc{gdb/mi}.
26305 Note the line breaks shown in the examples are here only for
26306 readability, they don't appear in the real output.
26308 @subheading Setting a Breakpoint
26310 Setting a breakpoint generates synchronous output which contains detailed
26311 information of the breakpoint.
26314 -> -break-insert main
26315 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26316 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26317 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26322 @subheading Program Execution
26324 Program execution generates asynchronous records and MI gives the
26325 reason that execution stopped.
26331 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26332 frame=@{addr="0x08048564",func="main",
26333 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26334 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26339 <- *stopped,reason="exited-normally"
26343 @subheading Quitting @value{GDBN}
26345 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26353 Please note that @samp{^exit} is printed immediately, but it might
26354 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26355 performs necessary cleanups, including killing programs being debugged
26356 or disconnecting from debug hardware, so the frontend should wait till
26357 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26358 fails to exit in reasonable time.
26360 @subheading A Bad Command
26362 Here's what happens if you pass a non-existent command:
26366 <- ^error,msg="Undefined MI command: rubbish"
26371 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26372 @node GDB/MI Command Description Format
26373 @section @sc{gdb/mi} Command Description Format
26375 The remaining sections describe blocks of commands. Each block of
26376 commands is laid out in a fashion similar to this section.
26378 @subheading Motivation
26380 The motivation for this collection of commands.
26382 @subheading Introduction
26384 A brief introduction to this collection of commands as a whole.
26386 @subheading Commands
26388 For each command in the block, the following is described:
26390 @subsubheading Synopsis
26393 -command @var{args}@dots{}
26396 @subsubheading Result
26398 @subsubheading @value{GDBN} Command
26400 The corresponding @value{GDBN} CLI command(s), if any.
26402 @subsubheading Example
26404 Example(s) formatted for readability. Some of the described commands have
26405 not been implemented yet and these are labeled N.A.@: (not available).
26408 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26409 @node GDB/MI Breakpoint Commands
26410 @section @sc{gdb/mi} Breakpoint Commands
26412 @cindex breakpoint commands for @sc{gdb/mi}
26413 @cindex @sc{gdb/mi}, breakpoint commands
26414 This section documents @sc{gdb/mi} commands for manipulating
26417 @subheading The @code{-break-after} Command
26418 @findex -break-after
26420 @subsubheading Synopsis
26423 -break-after @var{number} @var{count}
26426 The breakpoint number @var{number} is not in effect until it has been
26427 hit @var{count} times. To see how this is reflected in the output of
26428 the @samp{-break-list} command, see the description of the
26429 @samp{-break-list} command below.
26431 @subsubheading @value{GDBN} Command
26433 The corresponding @value{GDBN} command is @samp{ignore}.
26435 @subsubheading Example
26440 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26441 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26442 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26450 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26451 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26452 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26453 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26454 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26455 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26456 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26457 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26458 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26459 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26464 @subheading The @code{-break-catch} Command
26465 @findex -break-catch
26468 @subheading The @code{-break-commands} Command
26469 @findex -break-commands
26471 @subsubheading Synopsis
26474 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26477 Specifies the CLI commands that should be executed when breakpoint
26478 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26479 are the commands. If no command is specified, any previously-set
26480 commands are cleared. @xref{Break Commands}. Typical use of this
26481 functionality is tracing a program, that is, printing of values of
26482 some variables whenever breakpoint is hit and then continuing.
26484 @subsubheading @value{GDBN} Command
26486 The corresponding @value{GDBN} command is @samp{commands}.
26488 @subsubheading Example
26493 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26494 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26495 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26498 -break-commands 1 "print v" "continue"
26503 @subheading The @code{-break-condition} Command
26504 @findex -break-condition
26506 @subsubheading Synopsis
26509 -break-condition @var{number} @var{expr}
26512 Breakpoint @var{number} will stop the program only if the condition in
26513 @var{expr} is true. The condition becomes part of the
26514 @samp{-break-list} output (see the description of the @samp{-break-list}
26517 @subsubheading @value{GDBN} Command
26519 The corresponding @value{GDBN} command is @samp{condition}.
26521 @subsubheading Example
26525 -break-condition 1 1
26529 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26530 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26531 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26532 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26533 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26534 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26535 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26536 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26537 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26538 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26542 @subheading The @code{-break-delete} Command
26543 @findex -break-delete
26545 @subsubheading Synopsis
26548 -break-delete ( @var{breakpoint} )+
26551 Delete the breakpoint(s) whose number(s) are specified in the argument
26552 list. This is obviously reflected in the breakpoint list.
26554 @subsubheading @value{GDBN} Command
26556 The corresponding @value{GDBN} command is @samp{delete}.
26558 @subsubheading Example
26566 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26567 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26568 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26569 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26570 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26571 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26572 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26577 @subheading The @code{-break-disable} Command
26578 @findex -break-disable
26580 @subsubheading Synopsis
26583 -break-disable ( @var{breakpoint} )+
26586 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26587 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26589 @subsubheading @value{GDBN} Command
26591 The corresponding @value{GDBN} command is @samp{disable}.
26593 @subsubheading Example
26601 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26602 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26603 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26604 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26605 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26606 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26607 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26608 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26609 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26610 line="5",thread-groups=["i1"],times="0"@}]@}
26614 @subheading The @code{-break-enable} Command
26615 @findex -break-enable
26617 @subsubheading Synopsis
26620 -break-enable ( @var{breakpoint} )+
26623 Enable (previously disabled) @var{breakpoint}(s).
26625 @subsubheading @value{GDBN} Command
26627 The corresponding @value{GDBN} command is @samp{enable}.
26629 @subsubheading Example
26637 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26638 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26639 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26640 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26641 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26642 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26643 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26644 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26645 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26646 line="5",thread-groups=["i1"],times="0"@}]@}
26650 @subheading The @code{-break-info} Command
26651 @findex -break-info
26653 @subsubheading Synopsis
26656 -break-info @var{breakpoint}
26660 Get information about a single breakpoint.
26662 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26663 Information}, for details on the format of each breakpoint in the
26666 @subsubheading @value{GDBN} Command
26668 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26670 @subsubheading Example
26673 @subheading The @code{-break-insert} Command
26674 @findex -break-insert
26676 @subsubheading Synopsis
26679 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26680 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26681 [ -p @var{thread-id} ] [ @var{location} ]
26685 If specified, @var{location}, can be one of:
26692 @item filename:linenum
26693 @item filename:function
26697 The possible optional parameters of this command are:
26701 Insert a temporary breakpoint.
26703 Insert a hardware breakpoint.
26705 If @var{location} cannot be parsed (for example if it
26706 refers to unknown files or functions), create a pending
26707 breakpoint. Without this flag, @value{GDBN} will report
26708 an error, and won't create a breakpoint, if @var{location}
26711 Create a disabled breakpoint.
26713 Create a tracepoint. @xref{Tracepoints}. When this parameter
26714 is used together with @samp{-h}, a fast tracepoint is created.
26715 @item -c @var{condition}
26716 Make the breakpoint conditional on @var{condition}.
26717 @item -i @var{ignore-count}
26718 Initialize the @var{ignore-count}.
26719 @item -p @var{thread-id}
26720 Restrict the breakpoint to the specified @var{thread-id}.
26723 @subsubheading Result
26725 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26726 resulting breakpoint.
26728 Note: this format is open to change.
26729 @c An out-of-band breakpoint instead of part of the result?
26731 @subsubheading @value{GDBN} Command
26733 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26734 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26736 @subsubheading Example
26741 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26742 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26745 -break-insert -t foo
26746 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26747 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26751 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26752 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26753 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26754 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26755 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26756 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26757 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26758 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26759 addr="0x0001072c", func="main",file="recursive2.c",
26760 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26762 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26763 addr="0x00010774",func="foo",file="recursive2.c",
26764 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26767 @c -break-insert -r foo.*
26768 @c ~int foo(int, int);
26769 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26770 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26775 @subheading The @code{-dprintf-insert} Command
26776 @findex -dprintf-insert
26778 @subsubheading Synopsis
26781 -dprintf-insert [ -t ] [ -f ] [ -d ]
26782 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26783 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
26788 If specified, @var{location}, can be one of:
26791 @item @var{function}
26794 @c @item @var{linenum}
26795 @item @var{filename}:@var{linenum}
26796 @item @var{filename}:function
26797 @item *@var{address}
26800 The possible optional parameters of this command are:
26804 Insert a temporary breakpoint.
26806 If @var{location} cannot be parsed (for example, if it
26807 refers to unknown files or functions), create a pending
26808 breakpoint. Without this flag, @value{GDBN} will report
26809 an error, and won't create a breakpoint, if @var{location}
26812 Create a disabled breakpoint.
26813 @item -c @var{condition}
26814 Make the breakpoint conditional on @var{condition}.
26815 @item -i @var{ignore-count}
26816 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
26817 to @var{ignore-count}.
26818 @item -p @var{thread-id}
26819 Restrict the breakpoint to the specified @var{thread-id}.
26822 @subsubheading Result
26824 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26825 resulting breakpoint.
26827 @c An out-of-band breakpoint instead of part of the result?
26829 @subsubheading @value{GDBN} Command
26831 The corresponding @value{GDBN} command is @samp{dprintf}.
26833 @subsubheading Example
26837 4-dprintf-insert foo "At foo entry\n"
26838 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
26839 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
26840 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
26841 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
26842 original-location="foo"@}
26844 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
26845 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
26846 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
26847 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
26848 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
26849 original-location="mi-dprintf.c:26"@}
26853 @subheading The @code{-break-list} Command
26854 @findex -break-list
26856 @subsubheading Synopsis
26862 Displays the list of inserted breakpoints, showing the following fields:
26866 number of the breakpoint
26868 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26870 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26873 is the breakpoint enabled or no: @samp{y} or @samp{n}
26875 memory location at which the breakpoint is set
26877 logical location of the breakpoint, expressed by function name, file
26879 @item Thread-groups
26880 list of thread groups to which this breakpoint applies
26882 number of times the breakpoint has been hit
26885 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26886 @code{body} field is an empty list.
26888 @subsubheading @value{GDBN} Command
26890 The corresponding @value{GDBN} command is @samp{info break}.
26892 @subsubheading Example
26897 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26898 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26899 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26900 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26901 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26902 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26903 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26904 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26905 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
26907 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26908 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26909 line="13",thread-groups=["i1"],times="0"@}]@}
26913 Here's an example of the result when there are no breakpoints:
26918 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26919 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26920 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26921 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26922 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26923 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26924 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26929 @subheading The @code{-break-passcount} Command
26930 @findex -break-passcount
26932 @subsubheading Synopsis
26935 -break-passcount @var{tracepoint-number} @var{passcount}
26938 Set the passcount for tracepoint @var{tracepoint-number} to
26939 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26940 is not a tracepoint, error is emitted. This corresponds to CLI
26941 command @samp{passcount}.
26943 @subheading The @code{-break-watch} Command
26944 @findex -break-watch
26946 @subsubheading Synopsis
26949 -break-watch [ -a | -r ]
26952 Create a watchpoint. With the @samp{-a} option it will create an
26953 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26954 read from or on a write to the memory location. With the @samp{-r}
26955 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26956 trigger only when the memory location is accessed for reading. Without
26957 either of the options, the watchpoint created is a regular watchpoint,
26958 i.e., it will trigger when the memory location is accessed for writing.
26959 @xref{Set Watchpoints, , Setting Watchpoints}.
26961 Note that @samp{-break-list} will report a single list of watchpoints and
26962 breakpoints inserted.
26964 @subsubheading @value{GDBN} Command
26966 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26969 @subsubheading Example
26971 Setting a watchpoint on a variable in the @code{main} function:
26976 ^done,wpt=@{number="2",exp="x"@}
26981 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26982 value=@{old="-268439212",new="55"@},
26983 frame=@{func="main",args=[],file="recursive2.c",
26984 fullname="/home/foo/bar/recursive2.c",line="5"@}
26988 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26989 the program execution twice: first for the variable changing value, then
26990 for the watchpoint going out of scope.
26995 ^done,wpt=@{number="5",exp="C"@}
27000 *stopped,reason="watchpoint-trigger",
27001 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27002 frame=@{func="callee4",args=[],
27003 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27004 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27009 *stopped,reason="watchpoint-scope",wpnum="5",
27010 frame=@{func="callee3",args=[@{name="strarg",
27011 value="0x11940 \"A string argument.\""@}],
27012 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27013 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27017 Listing breakpoints and watchpoints, at different points in the program
27018 execution. Note that once the watchpoint goes out of scope, it is
27024 ^done,wpt=@{number="2",exp="C"@}
27027 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27028 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27029 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27030 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27031 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27032 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27033 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27034 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27035 addr="0x00010734",func="callee4",
27036 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27037 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27039 bkpt=@{number="2",type="watchpoint",disp="keep",
27040 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27045 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27046 value=@{old="-276895068",new="3"@},
27047 frame=@{func="callee4",args=[],
27048 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27049 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27052 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27053 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27054 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27055 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27056 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27057 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27058 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27059 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27060 addr="0x00010734",func="callee4",
27061 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27062 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27064 bkpt=@{number="2",type="watchpoint",disp="keep",
27065 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27069 ^done,reason="watchpoint-scope",wpnum="2",
27070 frame=@{func="callee3",args=[@{name="strarg",
27071 value="0x11940 \"A string argument.\""@}],
27072 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27073 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27076 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27077 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27078 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27079 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27080 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27081 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27082 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27083 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27084 addr="0x00010734",func="callee4",
27085 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27086 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27087 thread-groups=["i1"],times="1"@}]@}
27092 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27093 @node GDB/MI Catchpoint Commands
27094 @section @sc{gdb/mi} Catchpoint Commands
27096 This section documents @sc{gdb/mi} commands for manipulating
27100 * Shared Library GDB/MI Catchpoint Commands::
27101 * Ada Exception GDB/MI Catchpoint Commands::
27104 @node Shared Library GDB/MI Catchpoint Commands
27105 @subsection Shared Library @sc{gdb/mi} Catchpoints
27107 @subheading The @code{-catch-load} Command
27108 @findex -catch-load
27110 @subsubheading Synopsis
27113 -catch-load [ -t ] [ -d ] @var{regexp}
27116 Add a catchpoint for library load events. If the @samp{-t} option is used,
27117 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27118 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27119 in a disabled state. The @samp{regexp} argument is a regular
27120 expression used to match the name of the loaded library.
27123 @subsubheading @value{GDBN} Command
27125 The corresponding @value{GDBN} command is @samp{catch load}.
27127 @subsubheading Example
27130 -catch-load -t foo.so
27131 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27132 what="load of library matching foo.so",catch-type="load",times="0"@}
27137 @subheading The @code{-catch-unload} Command
27138 @findex -catch-unload
27140 @subsubheading Synopsis
27143 -catch-unload [ -t ] [ -d ] @var{regexp}
27146 Add a catchpoint for library unload events. If the @samp{-t} option is
27147 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27148 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27149 created in a disabled state. The @samp{regexp} argument is a regular
27150 expression used to match the name of the unloaded library.
27152 @subsubheading @value{GDBN} Command
27154 The corresponding @value{GDBN} command is @samp{catch unload}.
27156 @subsubheading Example
27159 -catch-unload -d bar.so
27160 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27161 what="load of library matching bar.so",catch-type="unload",times="0"@}
27165 @node Ada Exception GDB/MI Catchpoint Commands
27166 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27168 The following @sc{gdb/mi} commands can be used to create catchpoints
27169 that stop the execution when Ada exceptions are being raised.
27171 @subheading The @code{-catch-assert} Command
27172 @findex -catch-assert
27174 @subsubheading Synopsis
27177 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27180 Add a catchpoint for failed Ada assertions.
27182 The possible optional parameters for this command are:
27185 @item -c @var{condition}
27186 Make the catchpoint conditional on @var{condition}.
27188 Create a disabled catchpoint.
27190 Create a temporary catchpoint.
27193 @subsubheading @value{GDBN} Command
27195 The corresponding @value{GDBN} command is @samp{catch assert}.
27197 @subsubheading Example
27201 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27202 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27203 thread-groups=["i1"],times="0",
27204 original-location="__gnat_debug_raise_assert_failure"@}
27208 @subheading The @code{-catch-exception} Command
27209 @findex -catch-exception
27211 @subsubheading Synopsis
27214 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27218 Add a catchpoint stopping when Ada exceptions are raised.
27219 By default, the command stops the program when any Ada exception
27220 gets raised. But it is also possible, by using some of the
27221 optional parameters described below, to create more selective
27224 The possible optional parameters for this command are:
27227 @item -c @var{condition}
27228 Make the catchpoint conditional on @var{condition}.
27230 Create a disabled catchpoint.
27231 @item -e @var{exception-name}
27232 Only stop when @var{exception-name} is raised. This option cannot
27233 be used combined with @samp{-u}.
27235 Create a temporary catchpoint.
27237 Stop only when an unhandled exception gets raised. This option
27238 cannot be used combined with @samp{-e}.
27241 @subsubheading @value{GDBN} Command
27243 The corresponding @value{GDBN} commands are @samp{catch exception}
27244 and @samp{catch exception unhandled}.
27246 @subsubheading Example
27249 -catch-exception -e Program_Error
27250 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27251 enabled="y",addr="0x0000000000404874",
27252 what="`Program_Error' Ada exception", thread-groups=["i1"],
27253 times="0",original-location="__gnat_debug_raise_exception"@}
27257 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27258 @node GDB/MI Program Context
27259 @section @sc{gdb/mi} Program Context
27261 @subheading The @code{-exec-arguments} Command
27262 @findex -exec-arguments
27265 @subsubheading Synopsis
27268 -exec-arguments @var{args}
27271 Set the inferior program arguments, to be used in the next
27274 @subsubheading @value{GDBN} Command
27276 The corresponding @value{GDBN} command is @samp{set args}.
27278 @subsubheading Example
27282 -exec-arguments -v word
27289 @subheading The @code{-exec-show-arguments} Command
27290 @findex -exec-show-arguments
27292 @subsubheading Synopsis
27295 -exec-show-arguments
27298 Print the arguments of the program.
27300 @subsubheading @value{GDBN} Command
27302 The corresponding @value{GDBN} command is @samp{show args}.
27304 @subsubheading Example
27309 @subheading The @code{-environment-cd} Command
27310 @findex -environment-cd
27312 @subsubheading Synopsis
27315 -environment-cd @var{pathdir}
27318 Set @value{GDBN}'s working directory.
27320 @subsubheading @value{GDBN} Command
27322 The corresponding @value{GDBN} command is @samp{cd}.
27324 @subsubheading Example
27328 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27334 @subheading The @code{-environment-directory} Command
27335 @findex -environment-directory
27337 @subsubheading Synopsis
27340 -environment-directory [ -r ] [ @var{pathdir} ]+
27343 Add directories @var{pathdir} to beginning of search path for source files.
27344 If the @samp{-r} option is used, the search path is reset to the default
27345 search path. If directories @var{pathdir} are supplied in addition to the
27346 @samp{-r} option, the search path is first reset and then addition
27348 Multiple directories may be specified, separated by blanks. Specifying
27349 multiple directories in a single command
27350 results in the directories added to the beginning of the
27351 search path in the same order they were presented in the command.
27352 If blanks are needed as
27353 part of a directory name, double-quotes should be used around
27354 the name. In the command output, the path will show up separated
27355 by the system directory-separator character. The directory-separator
27356 character must not be used
27357 in any directory name.
27358 If no directories are specified, the current search path is displayed.
27360 @subsubheading @value{GDBN} Command
27362 The corresponding @value{GDBN} command is @samp{dir}.
27364 @subsubheading Example
27368 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27369 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27371 -environment-directory ""
27372 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27374 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27375 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27377 -environment-directory -r
27378 ^done,source-path="$cdir:$cwd"
27383 @subheading The @code{-environment-path} Command
27384 @findex -environment-path
27386 @subsubheading Synopsis
27389 -environment-path [ -r ] [ @var{pathdir} ]+
27392 Add directories @var{pathdir} to beginning of search path for object files.
27393 If the @samp{-r} option is used, the search path is reset to the original
27394 search path that existed at gdb start-up. If directories @var{pathdir} are
27395 supplied in addition to the
27396 @samp{-r} option, the search path is first reset and then addition
27398 Multiple directories may be specified, separated by blanks. Specifying
27399 multiple directories in a single command
27400 results in the directories added to the beginning of the
27401 search path in the same order they were presented in the command.
27402 If blanks are needed as
27403 part of a directory name, double-quotes should be used around
27404 the name. In the command output, the path will show up separated
27405 by the system directory-separator character. The directory-separator
27406 character must not be used
27407 in any directory name.
27408 If no directories are specified, the current path is displayed.
27411 @subsubheading @value{GDBN} Command
27413 The corresponding @value{GDBN} command is @samp{path}.
27415 @subsubheading Example
27420 ^done,path="/usr/bin"
27422 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27423 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27425 -environment-path -r /usr/local/bin
27426 ^done,path="/usr/local/bin:/usr/bin"
27431 @subheading The @code{-environment-pwd} Command
27432 @findex -environment-pwd
27434 @subsubheading Synopsis
27440 Show the current working directory.
27442 @subsubheading @value{GDBN} Command
27444 The corresponding @value{GDBN} command is @samp{pwd}.
27446 @subsubheading Example
27451 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27455 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27456 @node GDB/MI Thread Commands
27457 @section @sc{gdb/mi} Thread Commands
27460 @subheading The @code{-thread-info} Command
27461 @findex -thread-info
27463 @subsubheading Synopsis
27466 -thread-info [ @var{thread-id} ]
27469 Reports information about either a specific thread, if
27470 the @var{thread-id} parameter is present, or about all
27471 threads. When printing information about all threads,
27472 also reports the current thread.
27474 @subsubheading @value{GDBN} Command
27476 The @samp{info thread} command prints the same information
27479 @subsubheading Result
27481 The result is a list of threads. The following attributes are
27482 defined for a given thread:
27486 This field exists only for the current thread. It has the value @samp{*}.
27489 The identifier that @value{GDBN} uses to refer to the thread.
27492 The identifier that the target uses to refer to the thread.
27495 Extra information about the thread, in a target-specific format. This
27499 The name of the thread. If the user specified a name using the
27500 @code{thread name} command, then this name is given. Otherwise, if
27501 @value{GDBN} can extract the thread name from the target, then that
27502 name is given. If @value{GDBN} cannot find the thread name, then this
27506 The stack frame currently executing in the thread.
27509 The thread's state. The @samp{state} field may have the following
27514 The thread is stopped. Frame information is available for stopped
27518 The thread is running. There's no frame information for running
27524 If @value{GDBN} can find the CPU core on which this thread is running,
27525 then this field is the core identifier. This field is optional.
27529 @subsubheading Example
27534 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27535 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27536 args=[]@},state="running"@},
27537 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27538 frame=@{level="0",addr="0x0804891f",func="foo",
27539 args=[@{name="i",value="10"@}],
27540 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27541 state="running"@}],
27542 current-thread-id="1"
27546 @subheading The @code{-thread-list-ids} Command
27547 @findex -thread-list-ids
27549 @subsubheading Synopsis
27555 Produces a list of the currently known @value{GDBN} thread ids. At the
27556 end of the list it also prints the total number of such threads.
27558 This command is retained for historical reasons, the
27559 @code{-thread-info} command should be used instead.
27561 @subsubheading @value{GDBN} Command
27563 Part of @samp{info threads} supplies the same information.
27565 @subsubheading Example
27570 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27571 current-thread-id="1",number-of-threads="3"
27576 @subheading The @code{-thread-select} Command
27577 @findex -thread-select
27579 @subsubheading Synopsis
27582 -thread-select @var{threadnum}
27585 Make @var{threadnum} the current thread. It prints the number of the new
27586 current thread, and the topmost frame for that thread.
27588 This command is deprecated in favor of explicitly using the
27589 @samp{--thread} option to each command.
27591 @subsubheading @value{GDBN} Command
27593 The corresponding @value{GDBN} command is @samp{thread}.
27595 @subsubheading Example
27602 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27603 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27607 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27608 number-of-threads="3"
27611 ^done,new-thread-id="3",
27612 frame=@{level="0",func="vprintf",
27613 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27614 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27618 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27619 @node GDB/MI Ada Tasking Commands
27620 @section @sc{gdb/mi} Ada Tasking Commands
27622 @subheading The @code{-ada-task-info} Command
27623 @findex -ada-task-info
27625 @subsubheading Synopsis
27628 -ada-task-info [ @var{task-id} ]
27631 Reports information about either a specific Ada task, if the
27632 @var{task-id} parameter is present, or about all Ada tasks.
27634 @subsubheading @value{GDBN} Command
27636 The @samp{info tasks} command prints the same information
27637 about all Ada tasks (@pxref{Ada Tasks}).
27639 @subsubheading Result
27641 The result is a table of Ada tasks. The following columns are
27642 defined for each Ada task:
27646 This field exists only for the current thread. It has the value @samp{*}.
27649 The identifier that @value{GDBN} uses to refer to the Ada task.
27652 The identifier that the target uses to refer to the Ada task.
27655 The identifier of the thread corresponding to the Ada task.
27657 This field should always exist, as Ada tasks are always implemented
27658 on top of a thread. But if @value{GDBN} cannot find this corresponding
27659 thread for any reason, the field is omitted.
27662 This field exists only when the task was created by another task.
27663 In this case, it provides the ID of the parent task.
27666 The base priority of the task.
27669 The current state of the task. For a detailed description of the
27670 possible states, see @ref{Ada Tasks}.
27673 The name of the task.
27677 @subsubheading Example
27681 ^done,tasks=@{nr_rows="3",nr_cols="8",
27682 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27683 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27684 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27685 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27686 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27687 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27688 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27689 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27690 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27691 state="Child Termination Wait",name="main_task"@}]@}
27695 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27696 @node GDB/MI Program Execution
27697 @section @sc{gdb/mi} Program Execution
27699 These are the asynchronous commands which generate the out-of-band
27700 record @samp{*stopped}. Currently @value{GDBN} only really executes
27701 asynchronously with remote targets and this interaction is mimicked in
27704 @subheading The @code{-exec-continue} Command
27705 @findex -exec-continue
27707 @subsubheading Synopsis
27710 -exec-continue [--reverse] [--all|--thread-group N]
27713 Resumes the execution of the inferior program, which will continue
27714 to execute until it reaches a debugger stop event. If the
27715 @samp{--reverse} option is specified, execution resumes in reverse until
27716 it reaches a stop event. Stop events may include
27719 breakpoints or watchpoints
27721 signals or exceptions
27723 the end of the process (or its beginning under @samp{--reverse})
27725 the end or beginning of a replay log if one is being used.
27727 In all-stop mode (@pxref{All-Stop
27728 Mode}), may resume only one thread, or all threads, depending on the
27729 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27730 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27731 ignored in all-stop mode. If the @samp{--thread-group} options is
27732 specified, then all threads in that thread group are resumed.
27734 @subsubheading @value{GDBN} Command
27736 The corresponding @value{GDBN} corresponding is @samp{continue}.
27738 @subsubheading Example
27745 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27746 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27752 @subheading The @code{-exec-finish} Command
27753 @findex -exec-finish
27755 @subsubheading Synopsis
27758 -exec-finish [--reverse]
27761 Resumes the execution of the inferior program until the current
27762 function is exited. Displays the results returned by the function.
27763 If the @samp{--reverse} option is specified, resumes the reverse
27764 execution of the inferior program until the point where current
27765 function was called.
27767 @subsubheading @value{GDBN} Command
27769 The corresponding @value{GDBN} command is @samp{finish}.
27771 @subsubheading Example
27773 Function returning @code{void}.
27780 *stopped,reason="function-finished",frame=@{func="main",args=[],
27781 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27785 Function returning other than @code{void}. The name of the internal
27786 @value{GDBN} variable storing the result is printed, together with the
27793 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27794 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27795 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27796 gdb-result-var="$1",return-value="0"
27801 @subheading The @code{-exec-interrupt} Command
27802 @findex -exec-interrupt
27804 @subsubheading Synopsis
27807 -exec-interrupt [--all|--thread-group N]
27810 Interrupts the background execution of the target. Note how the token
27811 associated with the stop message is the one for the execution command
27812 that has been interrupted. The token for the interrupt itself only
27813 appears in the @samp{^done} output. If the user is trying to
27814 interrupt a non-running program, an error message will be printed.
27816 Note that when asynchronous execution is enabled, this command is
27817 asynchronous just like other execution commands. That is, first the
27818 @samp{^done} response will be printed, and the target stop will be
27819 reported after that using the @samp{*stopped} notification.
27821 In non-stop mode, only the context thread is interrupted by default.
27822 All threads (in all inferiors) will be interrupted if the
27823 @samp{--all} option is specified. If the @samp{--thread-group}
27824 option is specified, all threads in that group will be interrupted.
27826 @subsubheading @value{GDBN} Command
27828 The corresponding @value{GDBN} command is @samp{interrupt}.
27830 @subsubheading Example
27841 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27842 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27843 fullname="/home/foo/bar/try.c",line="13"@}
27848 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27852 @subheading The @code{-exec-jump} Command
27855 @subsubheading Synopsis
27858 -exec-jump @var{location}
27861 Resumes execution of the inferior program at the location specified by
27862 parameter. @xref{Specify Location}, for a description of the
27863 different forms of @var{location}.
27865 @subsubheading @value{GDBN} Command
27867 The corresponding @value{GDBN} command is @samp{jump}.
27869 @subsubheading Example
27872 -exec-jump foo.c:10
27873 *running,thread-id="all"
27878 @subheading The @code{-exec-next} Command
27881 @subsubheading Synopsis
27884 -exec-next [--reverse]
27887 Resumes execution of the inferior program, stopping when the beginning
27888 of the next source line is reached.
27890 If the @samp{--reverse} option is specified, resumes reverse execution
27891 of the inferior program, stopping at the beginning of the previous
27892 source line. If you issue this command on the first line of a
27893 function, it will take you back to the caller of that function, to the
27894 source line where the function was called.
27897 @subsubheading @value{GDBN} Command
27899 The corresponding @value{GDBN} command is @samp{next}.
27901 @subsubheading Example
27907 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27912 @subheading The @code{-exec-next-instruction} Command
27913 @findex -exec-next-instruction
27915 @subsubheading Synopsis
27918 -exec-next-instruction [--reverse]
27921 Executes one machine instruction. If the instruction is a function
27922 call, continues until the function returns. If the program stops at an
27923 instruction in the middle of a source line, the address will be
27926 If the @samp{--reverse} option is specified, resumes reverse execution
27927 of the inferior program, stopping at the previous instruction. If the
27928 previously executed instruction was a return from another function,
27929 it will continue to execute in reverse until the call to that function
27930 (from the current stack frame) is reached.
27932 @subsubheading @value{GDBN} Command
27934 The corresponding @value{GDBN} command is @samp{nexti}.
27936 @subsubheading Example
27940 -exec-next-instruction
27944 *stopped,reason="end-stepping-range",
27945 addr="0x000100d4",line="5",file="hello.c"
27950 @subheading The @code{-exec-return} Command
27951 @findex -exec-return
27953 @subsubheading Synopsis
27959 Makes current function return immediately. Doesn't execute the inferior.
27960 Displays the new current frame.
27962 @subsubheading @value{GDBN} Command
27964 The corresponding @value{GDBN} command is @samp{return}.
27966 @subsubheading Example
27970 200-break-insert callee4
27971 200^done,bkpt=@{number="1",addr="0x00010734",
27972 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27977 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27978 frame=@{func="callee4",args=[],
27979 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27980 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27986 111^done,frame=@{level="0",func="callee3",
27987 args=[@{name="strarg",
27988 value="0x11940 \"A string argument.\""@}],
27989 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27990 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27995 @subheading The @code{-exec-run} Command
27998 @subsubheading Synopsis
28001 -exec-run [ --all | --thread-group N ] [ --start ]
28004 Starts execution of the inferior from the beginning. The inferior
28005 executes until either a breakpoint is encountered or the program
28006 exits. In the latter case the output will include an exit code, if
28007 the program has exited exceptionally.
28009 When neither the @samp{--all} nor the @samp{--thread-group} option
28010 is specified, the current inferior is started. If the
28011 @samp{--thread-group} option is specified, it should refer to a thread
28012 group of type @samp{process}, and that thread group will be started.
28013 If the @samp{--all} option is specified, then all inferiors will be started.
28015 Using the @samp{--start} option instructs the debugger to stop
28016 the execution at the start of the inferior's main subprogram,
28017 following the same behavior as the @code{start} command
28018 (@pxref{Starting}).
28020 @subsubheading @value{GDBN} Command
28022 The corresponding @value{GDBN} command is @samp{run}.
28024 @subsubheading Examples
28029 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28034 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28035 frame=@{func="main",args=[],file="recursive2.c",
28036 fullname="/home/foo/bar/recursive2.c",line="4"@}
28041 Program exited normally:
28049 *stopped,reason="exited-normally"
28054 Program exited exceptionally:
28062 *stopped,reason="exited",exit-code="01"
28066 Another way the program can terminate is if it receives a signal such as
28067 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28071 *stopped,reason="exited-signalled",signal-name="SIGINT",
28072 signal-meaning="Interrupt"
28076 @c @subheading -exec-signal
28079 @subheading The @code{-exec-step} Command
28082 @subsubheading Synopsis
28085 -exec-step [--reverse]
28088 Resumes execution of the inferior program, stopping when the beginning
28089 of the next source line is reached, if the next source line is not a
28090 function call. If it is, stop at the first instruction of the called
28091 function. If the @samp{--reverse} option is specified, resumes reverse
28092 execution of the inferior program, stopping at the beginning of the
28093 previously executed source line.
28095 @subsubheading @value{GDBN} Command
28097 The corresponding @value{GDBN} command is @samp{step}.
28099 @subsubheading Example
28101 Stepping into a function:
28107 *stopped,reason="end-stepping-range",
28108 frame=@{func="foo",args=[@{name="a",value="10"@},
28109 @{name="b",value="0"@}],file="recursive2.c",
28110 fullname="/home/foo/bar/recursive2.c",line="11"@}
28120 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28125 @subheading The @code{-exec-step-instruction} Command
28126 @findex -exec-step-instruction
28128 @subsubheading Synopsis
28131 -exec-step-instruction [--reverse]
28134 Resumes the inferior which executes one machine instruction. If the
28135 @samp{--reverse} option is specified, resumes reverse execution of the
28136 inferior program, stopping at the previously executed instruction.
28137 The output, once @value{GDBN} has stopped, will vary depending on
28138 whether we have stopped in the middle of a source line or not. In the
28139 former case, the address at which the program stopped will be printed
28142 @subsubheading @value{GDBN} Command
28144 The corresponding @value{GDBN} command is @samp{stepi}.
28146 @subsubheading Example
28150 -exec-step-instruction
28154 *stopped,reason="end-stepping-range",
28155 frame=@{func="foo",args=[],file="try.c",
28156 fullname="/home/foo/bar/try.c",line="10"@}
28158 -exec-step-instruction
28162 *stopped,reason="end-stepping-range",
28163 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28164 fullname="/home/foo/bar/try.c",line="10"@}
28169 @subheading The @code{-exec-until} Command
28170 @findex -exec-until
28172 @subsubheading Synopsis
28175 -exec-until [ @var{location} ]
28178 Executes the inferior until the @var{location} specified in the
28179 argument is reached. If there is no argument, the inferior executes
28180 until a source line greater than the current one is reached. The
28181 reason for stopping in this case will be @samp{location-reached}.
28183 @subsubheading @value{GDBN} Command
28185 The corresponding @value{GDBN} command is @samp{until}.
28187 @subsubheading Example
28191 -exec-until recursive2.c:6
28195 *stopped,reason="location-reached",frame=@{func="main",args=[],
28196 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28201 @subheading -file-clear
28202 Is this going away????
28205 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28206 @node GDB/MI Stack Manipulation
28207 @section @sc{gdb/mi} Stack Manipulation Commands
28209 @subheading The @code{-enable-frame-filters} Command
28210 @findex -enable-frame-filters
28213 -enable-frame-filters
28216 @value{GDBN} allows Python-based frame filters to affect the output of
28217 the MI commands relating to stack traces. As there is no way to
28218 implement this in a fully backward-compatible way, a front end must
28219 request that this functionality be enabled.
28221 Once enabled, this feature cannot be disabled.
28223 Note that if Python support has not been compiled into @value{GDBN},
28224 this command will still succeed (and do nothing).
28226 @subheading The @code{-stack-info-frame} Command
28227 @findex -stack-info-frame
28229 @subsubheading Synopsis
28235 Get info on the selected frame.
28237 @subsubheading @value{GDBN} Command
28239 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28240 (without arguments).
28242 @subsubheading Example
28247 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28248 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28249 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28253 @subheading The @code{-stack-info-depth} Command
28254 @findex -stack-info-depth
28256 @subsubheading Synopsis
28259 -stack-info-depth [ @var{max-depth} ]
28262 Return the depth of the stack. If the integer argument @var{max-depth}
28263 is specified, do not count beyond @var{max-depth} frames.
28265 @subsubheading @value{GDBN} Command
28267 There's no equivalent @value{GDBN} command.
28269 @subsubheading Example
28271 For a stack with frame levels 0 through 11:
28278 -stack-info-depth 4
28281 -stack-info-depth 12
28284 -stack-info-depth 11
28287 -stack-info-depth 13
28292 @anchor{-stack-list-arguments}
28293 @subheading The @code{-stack-list-arguments} Command
28294 @findex -stack-list-arguments
28296 @subsubheading Synopsis
28299 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28300 [ @var{low-frame} @var{high-frame} ]
28303 Display a list of the arguments for the frames between @var{low-frame}
28304 and @var{high-frame} (inclusive). If @var{low-frame} and
28305 @var{high-frame} are not provided, list the arguments for the whole
28306 call stack. If the two arguments are equal, show the single frame
28307 at the corresponding level. It is an error if @var{low-frame} is
28308 larger than the actual number of frames. On the other hand,
28309 @var{high-frame} may be larger than the actual number of frames, in
28310 which case only existing frames will be returned.
28312 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28313 the variables; if it is 1 or @code{--all-values}, print also their
28314 values; and if it is 2 or @code{--simple-values}, print the name,
28315 type and value for simple data types, and the name and type for arrays,
28316 structures and unions. If the option @code{--no-frame-filters} is
28317 supplied, then Python frame filters will not be executed.
28319 If the @code{--skip-unavailable} option is specified, arguments that
28320 are not available are not listed. Partially available arguments
28321 are still displayed, however.
28323 Use of this command to obtain arguments in a single frame is
28324 deprecated in favor of the @samp{-stack-list-variables} command.
28326 @subsubheading @value{GDBN} Command
28328 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28329 @samp{gdb_get_args} command which partially overlaps with the
28330 functionality of @samp{-stack-list-arguments}.
28332 @subsubheading Example
28339 frame=@{level="0",addr="0x00010734",func="callee4",
28340 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28341 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28342 frame=@{level="1",addr="0x0001076c",func="callee3",
28343 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28344 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28345 frame=@{level="2",addr="0x0001078c",func="callee2",
28346 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28347 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28348 frame=@{level="3",addr="0x000107b4",func="callee1",
28349 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28350 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28351 frame=@{level="4",addr="0x000107e0",func="main",
28352 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28353 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28355 -stack-list-arguments 0
28358 frame=@{level="0",args=[]@},
28359 frame=@{level="1",args=[name="strarg"]@},
28360 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28361 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28362 frame=@{level="4",args=[]@}]
28364 -stack-list-arguments 1
28367 frame=@{level="0",args=[]@},
28369 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28370 frame=@{level="2",args=[
28371 @{name="intarg",value="2"@},
28372 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28373 @{frame=@{level="3",args=[
28374 @{name="intarg",value="2"@},
28375 @{name="strarg",value="0x11940 \"A string argument.\""@},
28376 @{name="fltarg",value="3.5"@}]@},
28377 frame=@{level="4",args=[]@}]
28379 -stack-list-arguments 0 2 2
28380 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28382 -stack-list-arguments 1 2 2
28383 ^done,stack-args=[frame=@{level="2",
28384 args=[@{name="intarg",value="2"@},
28385 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28389 @c @subheading -stack-list-exception-handlers
28392 @anchor{-stack-list-frames}
28393 @subheading The @code{-stack-list-frames} Command
28394 @findex -stack-list-frames
28396 @subsubheading Synopsis
28399 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28402 List the frames currently on the stack. For each frame it displays the
28407 The frame number, 0 being the topmost frame, i.e., the innermost function.
28409 The @code{$pc} value for that frame.
28413 File name of the source file where the function lives.
28414 @item @var{fullname}
28415 The full file name of the source file where the function lives.
28417 Line number corresponding to the @code{$pc}.
28419 The shared library where this function is defined. This is only given
28420 if the frame's function is not known.
28423 If invoked without arguments, this command prints a backtrace for the
28424 whole stack. If given two integer arguments, it shows the frames whose
28425 levels are between the two arguments (inclusive). If the two arguments
28426 are equal, it shows the single frame at the corresponding level. It is
28427 an error if @var{low-frame} is larger than the actual number of
28428 frames. On the other hand, @var{high-frame} may be larger than the
28429 actual number of frames, in which case only existing frames will be
28430 returned. If the option @code{--no-frame-filters} is supplied, then
28431 Python frame filters will not be executed.
28433 @subsubheading @value{GDBN} Command
28435 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28437 @subsubheading Example
28439 Full stack backtrace:
28445 [frame=@{level="0",addr="0x0001076c",func="foo",
28446 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28447 frame=@{level="1",addr="0x000107a4",func="foo",
28448 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28449 frame=@{level="2",addr="0x000107a4",func="foo",
28450 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28451 frame=@{level="3",addr="0x000107a4",func="foo",
28452 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28453 frame=@{level="4",addr="0x000107a4",func="foo",
28454 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28455 frame=@{level="5",addr="0x000107a4",func="foo",
28456 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28457 frame=@{level="6",addr="0x000107a4",func="foo",
28458 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28459 frame=@{level="7",addr="0x000107a4",func="foo",
28460 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28461 frame=@{level="8",addr="0x000107a4",func="foo",
28462 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28463 frame=@{level="9",addr="0x000107a4",func="foo",
28464 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28465 frame=@{level="10",addr="0x000107a4",func="foo",
28466 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28467 frame=@{level="11",addr="0x00010738",func="main",
28468 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28472 Show frames between @var{low_frame} and @var{high_frame}:
28476 -stack-list-frames 3 5
28478 [frame=@{level="3",addr="0x000107a4",func="foo",
28479 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28480 frame=@{level="4",addr="0x000107a4",func="foo",
28481 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28482 frame=@{level="5",addr="0x000107a4",func="foo",
28483 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28487 Show a single frame:
28491 -stack-list-frames 3 3
28493 [frame=@{level="3",addr="0x000107a4",func="foo",
28494 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28499 @subheading The @code{-stack-list-locals} Command
28500 @findex -stack-list-locals
28501 @anchor{-stack-list-locals}
28503 @subsubheading Synopsis
28506 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28509 Display the local variable names for the selected frame. If
28510 @var{print-values} is 0 or @code{--no-values}, print only the names of
28511 the variables; if it is 1 or @code{--all-values}, print also their
28512 values; and if it is 2 or @code{--simple-values}, print the name,
28513 type and value for simple data types, and the name and type for arrays,
28514 structures and unions. In this last case, a frontend can immediately
28515 display the value of simple data types and create variable objects for
28516 other data types when the user wishes to explore their values in
28517 more detail. If the option @code{--no-frame-filters} is supplied, then
28518 Python frame filters will not be executed.
28520 If the @code{--skip-unavailable} option is specified, local variables
28521 that are not available are not listed. Partially available local
28522 variables are still displayed, however.
28524 This command is deprecated in favor of the
28525 @samp{-stack-list-variables} command.
28527 @subsubheading @value{GDBN} Command
28529 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28531 @subsubheading Example
28535 -stack-list-locals 0
28536 ^done,locals=[name="A",name="B",name="C"]
28538 -stack-list-locals --all-values
28539 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28540 @{name="C",value="@{1, 2, 3@}"@}]
28541 -stack-list-locals --simple-values
28542 ^done,locals=[@{name="A",type="int",value="1"@},
28543 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28547 @anchor{-stack-list-variables}
28548 @subheading The @code{-stack-list-variables} Command
28549 @findex -stack-list-variables
28551 @subsubheading Synopsis
28554 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28557 Display the names of local variables and function arguments for the selected frame. If
28558 @var{print-values} is 0 or @code{--no-values}, print only the names of
28559 the variables; if it is 1 or @code{--all-values}, print also their
28560 values; and if it is 2 or @code{--simple-values}, print the name,
28561 type and value for simple data types, and the name and type for arrays,
28562 structures and unions. If the option @code{--no-frame-filters} is
28563 supplied, then Python frame filters will not be executed.
28565 If the @code{--skip-unavailable} option is specified, local variables
28566 and arguments that are not available are not listed. Partially
28567 available arguments and local variables are still displayed, however.
28569 @subsubheading Example
28573 -stack-list-variables --thread 1 --frame 0 --all-values
28574 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28579 @subheading The @code{-stack-select-frame} Command
28580 @findex -stack-select-frame
28582 @subsubheading Synopsis
28585 -stack-select-frame @var{framenum}
28588 Change the selected frame. Select a different frame @var{framenum} on
28591 This command in deprecated in favor of passing the @samp{--frame}
28592 option to every command.
28594 @subsubheading @value{GDBN} Command
28596 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28597 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28599 @subsubheading Example
28603 -stack-select-frame 2
28608 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28609 @node GDB/MI Variable Objects
28610 @section @sc{gdb/mi} Variable Objects
28614 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28616 For the implementation of a variable debugger window (locals, watched
28617 expressions, etc.), we are proposing the adaptation of the existing code
28618 used by @code{Insight}.
28620 The two main reasons for that are:
28624 It has been proven in practice (it is already on its second generation).
28627 It will shorten development time (needless to say how important it is
28631 The original interface was designed to be used by Tcl code, so it was
28632 slightly changed so it could be used through @sc{gdb/mi}. This section
28633 describes the @sc{gdb/mi} operations that will be available and gives some
28634 hints about their use.
28636 @emph{Note}: In addition to the set of operations described here, we
28637 expect the @sc{gui} implementation of a variable window to require, at
28638 least, the following operations:
28641 @item @code{-gdb-show} @code{output-radix}
28642 @item @code{-stack-list-arguments}
28643 @item @code{-stack-list-locals}
28644 @item @code{-stack-select-frame}
28649 @subheading Introduction to Variable Objects
28651 @cindex variable objects in @sc{gdb/mi}
28653 Variable objects are "object-oriented" MI interface for examining and
28654 changing values of expressions. Unlike some other MI interfaces that
28655 work with expressions, variable objects are specifically designed for
28656 simple and efficient presentation in the frontend. A variable object
28657 is identified by string name. When a variable object is created, the
28658 frontend specifies the expression for that variable object. The
28659 expression can be a simple variable, or it can be an arbitrary complex
28660 expression, and can even involve CPU registers. After creating a
28661 variable object, the frontend can invoke other variable object
28662 operations---for example to obtain or change the value of a variable
28663 object, or to change display format.
28665 Variable objects have hierarchical tree structure. Any variable object
28666 that corresponds to a composite type, such as structure in C, has
28667 a number of child variable objects, for example corresponding to each
28668 element of a structure. A child variable object can itself have
28669 children, recursively. Recursion ends when we reach
28670 leaf variable objects, which always have built-in types. Child variable
28671 objects are created only by explicit request, so if a frontend
28672 is not interested in the children of a particular variable object, no
28673 child will be created.
28675 For a leaf variable object it is possible to obtain its value as a
28676 string, or set the value from a string. String value can be also
28677 obtained for a non-leaf variable object, but it's generally a string
28678 that only indicates the type of the object, and does not list its
28679 contents. Assignment to a non-leaf variable object is not allowed.
28681 A frontend does not need to read the values of all variable objects each time
28682 the program stops. Instead, MI provides an update command that lists all
28683 variable objects whose values has changed since the last update
28684 operation. This considerably reduces the amount of data that must
28685 be transferred to the frontend. As noted above, children variable
28686 objects are created on demand, and only leaf variable objects have a
28687 real value. As result, gdb will read target memory only for leaf
28688 variables that frontend has created.
28690 The automatic update is not always desirable. For example, a frontend
28691 might want to keep a value of some expression for future reference,
28692 and never update it. For another example, fetching memory is
28693 relatively slow for embedded targets, so a frontend might want
28694 to disable automatic update for the variables that are either not
28695 visible on the screen, or ``closed''. This is possible using so
28696 called ``frozen variable objects''. Such variable objects are never
28697 implicitly updated.
28699 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28700 fixed variable object, the expression is parsed when the variable
28701 object is created, including associating identifiers to specific
28702 variables. The meaning of expression never changes. For a floating
28703 variable object the values of variables whose names appear in the
28704 expressions are re-evaluated every time in the context of the current
28705 frame. Consider this example:
28710 struct work_state state;
28717 If a fixed variable object for the @code{state} variable is created in
28718 this function, and we enter the recursive call, the variable
28719 object will report the value of @code{state} in the top-level
28720 @code{do_work} invocation. On the other hand, a floating variable
28721 object will report the value of @code{state} in the current frame.
28723 If an expression specified when creating a fixed variable object
28724 refers to a local variable, the variable object becomes bound to the
28725 thread and frame in which the variable object is created. When such
28726 variable object is updated, @value{GDBN} makes sure that the
28727 thread/frame combination the variable object is bound to still exists,
28728 and re-evaluates the variable object in context of that thread/frame.
28730 The following is the complete set of @sc{gdb/mi} operations defined to
28731 access this functionality:
28733 @multitable @columnfractions .4 .6
28734 @item @strong{Operation}
28735 @tab @strong{Description}
28737 @item @code{-enable-pretty-printing}
28738 @tab enable Python-based pretty-printing
28739 @item @code{-var-create}
28740 @tab create a variable object
28741 @item @code{-var-delete}
28742 @tab delete the variable object and/or its children
28743 @item @code{-var-set-format}
28744 @tab set the display format of this variable
28745 @item @code{-var-show-format}
28746 @tab show the display format of this variable
28747 @item @code{-var-info-num-children}
28748 @tab tells how many children this object has
28749 @item @code{-var-list-children}
28750 @tab return a list of the object's children
28751 @item @code{-var-info-type}
28752 @tab show the type of this variable object
28753 @item @code{-var-info-expression}
28754 @tab print parent-relative expression that this variable object represents
28755 @item @code{-var-info-path-expression}
28756 @tab print full expression that this variable object represents
28757 @item @code{-var-show-attributes}
28758 @tab is this variable editable? does it exist here?
28759 @item @code{-var-evaluate-expression}
28760 @tab get the value of this variable
28761 @item @code{-var-assign}
28762 @tab set the value of this variable
28763 @item @code{-var-update}
28764 @tab update the variable and its children
28765 @item @code{-var-set-frozen}
28766 @tab set frozeness attribute
28767 @item @code{-var-set-update-range}
28768 @tab set range of children to display on update
28771 In the next subsection we describe each operation in detail and suggest
28772 how it can be used.
28774 @subheading Description And Use of Operations on Variable Objects
28776 @subheading The @code{-enable-pretty-printing} Command
28777 @findex -enable-pretty-printing
28780 -enable-pretty-printing
28783 @value{GDBN} allows Python-based visualizers to affect the output of the
28784 MI variable object commands. However, because there was no way to
28785 implement this in a fully backward-compatible way, a front end must
28786 request that this functionality be enabled.
28788 Once enabled, this feature cannot be disabled.
28790 Note that if Python support has not been compiled into @value{GDBN},
28791 this command will still succeed (and do nothing).
28793 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28794 may work differently in future versions of @value{GDBN}.
28796 @subheading The @code{-var-create} Command
28797 @findex -var-create
28799 @subsubheading Synopsis
28802 -var-create @{@var{name} | "-"@}
28803 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28806 This operation creates a variable object, which allows the monitoring of
28807 a variable, the result of an expression, a memory cell or a CPU
28810 The @var{name} parameter is the string by which the object can be
28811 referenced. It must be unique. If @samp{-} is specified, the varobj
28812 system will generate a string ``varNNNNNN'' automatically. It will be
28813 unique provided that one does not specify @var{name} of that format.
28814 The command fails if a duplicate name is found.
28816 The frame under which the expression should be evaluated can be
28817 specified by @var{frame-addr}. A @samp{*} indicates that the current
28818 frame should be used. A @samp{@@} indicates that a floating variable
28819 object must be created.
28821 @var{expression} is any expression valid on the current language set (must not
28822 begin with a @samp{*}), or one of the following:
28826 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28829 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28832 @samp{$@var{regname}} --- a CPU register name
28835 @cindex dynamic varobj
28836 A varobj's contents may be provided by a Python-based pretty-printer. In this
28837 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28838 have slightly different semantics in some cases. If the
28839 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28840 will never create a dynamic varobj. This ensures backward
28841 compatibility for existing clients.
28843 @subsubheading Result
28845 This operation returns attributes of the newly-created varobj. These
28850 The name of the varobj.
28853 The number of children of the varobj. This number is not necessarily
28854 reliable for a dynamic varobj. Instead, you must examine the
28855 @samp{has_more} attribute.
28858 The varobj's scalar value. For a varobj whose type is some sort of
28859 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28860 will not be interesting.
28863 The varobj's type. This is a string representation of the type, as
28864 would be printed by the @value{GDBN} CLI. If @samp{print object}
28865 (@pxref{Print Settings, set print object}) is set to @code{on}, the
28866 @emph{actual} (derived) type of the object is shown rather than the
28867 @emph{declared} one.
28870 If a variable object is bound to a specific thread, then this is the
28871 thread's identifier.
28874 For a dynamic varobj, this indicates whether there appear to be any
28875 children available. For a non-dynamic varobj, this will be 0.
28878 This attribute will be present and have the value @samp{1} if the
28879 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28880 then this attribute will not be present.
28883 A dynamic varobj can supply a display hint to the front end. The
28884 value comes directly from the Python pretty-printer object's
28885 @code{display_hint} method. @xref{Pretty Printing API}.
28888 Typical output will look like this:
28891 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28892 has_more="@var{has_more}"
28896 @subheading The @code{-var-delete} Command
28897 @findex -var-delete
28899 @subsubheading Synopsis
28902 -var-delete [ -c ] @var{name}
28905 Deletes a previously created variable object and all of its children.
28906 With the @samp{-c} option, just deletes the children.
28908 Returns an error if the object @var{name} is not found.
28911 @subheading The @code{-var-set-format} Command
28912 @findex -var-set-format
28914 @subsubheading Synopsis
28917 -var-set-format @var{name} @var{format-spec}
28920 Sets the output format for the value of the object @var{name} to be
28923 @anchor{-var-set-format}
28924 The syntax for the @var{format-spec} is as follows:
28927 @var{format-spec} @expansion{}
28928 @{binary | decimal | hexadecimal | octal | natural@}
28931 The natural format is the default format choosen automatically
28932 based on the variable type (like decimal for an @code{int}, hex
28933 for pointers, etc.).
28935 For a variable with children, the format is set only on the
28936 variable itself, and the children are not affected.
28938 @subheading The @code{-var-show-format} Command
28939 @findex -var-show-format
28941 @subsubheading Synopsis
28944 -var-show-format @var{name}
28947 Returns the format used to display the value of the object @var{name}.
28950 @var{format} @expansion{}
28955 @subheading The @code{-var-info-num-children} Command
28956 @findex -var-info-num-children
28958 @subsubheading Synopsis
28961 -var-info-num-children @var{name}
28964 Returns the number of children of a variable object @var{name}:
28970 Note that this number is not completely reliable for a dynamic varobj.
28971 It will return the current number of children, but more children may
28975 @subheading The @code{-var-list-children} Command
28976 @findex -var-list-children
28978 @subsubheading Synopsis
28981 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28983 @anchor{-var-list-children}
28985 Return a list of the children of the specified variable object and
28986 create variable objects for them, if they do not already exist. With
28987 a single argument or if @var{print-values} has a value of 0 or
28988 @code{--no-values}, print only the names of the variables; if
28989 @var{print-values} is 1 or @code{--all-values}, also print their
28990 values; and if it is 2 or @code{--simple-values} print the name and
28991 value for simple data types and just the name for arrays, structures
28994 @var{from} and @var{to}, if specified, indicate the range of children
28995 to report. If @var{from} or @var{to} is less than zero, the range is
28996 reset and all children will be reported. Otherwise, children starting
28997 at @var{from} (zero-based) and up to and excluding @var{to} will be
29000 If a child range is requested, it will only affect the current call to
29001 @code{-var-list-children}, but not future calls to @code{-var-update}.
29002 For this, you must instead use @code{-var-set-update-range}. The
29003 intent of this approach is to enable a front end to implement any
29004 update approach it likes; for example, scrolling a view may cause the
29005 front end to request more children with @code{-var-list-children}, and
29006 then the front end could call @code{-var-set-update-range} with a
29007 different range to ensure that future updates are restricted to just
29010 For each child the following results are returned:
29015 Name of the variable object created for this child.
29018 The expression to be shown to the user by the front end to designate this child.
29019 For example this may be the name of a structure member.
29021 For a dynamic varobj, this value cannot be used to form an
29022 expression. There is no way to do this at all with a dynamic varobj.
29024 For C/C@t{++} structures there are several pseudo children returned to
29025 designate access qualifiers. For these pseudo children @var{exp} is
29026 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29027 type and value are not present.
29029 A dynamic varobj will not report the access qualifying
29030 pseudo-children, regardless of the language. This information is not
29031 available at all with a dynamic varobj.
29034 Number of children this child has. For a dynamic varobj, this will be
29038 The type of the child. If @samp{print object}
29039 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29040 @emph{actual} (derived) type of the object is shown rather than the
29041 @emph{declared} one.
29044 If values were requested, this is the value.
29047 If this variable object is associated with a thread, this is the thread id.
29048 Otherwise this result is not present.
29051 If the variable object is frozen, this variable will be present with a value of 1.
29054 A dynamic varobj can supply a display hint to the front end. The
29055 value comes directly from the Python pretty-printer object's
29056 @code{display_hint} method. @xref{Pretty Printing API}.
29059 This attribute will be present and have the value @samp{1} if the
29060 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29061 then this attribute will not be present.
29065 The result may have its own attributes:
29069 A dynamic varobj can supply a display hint to the front end. The
29070 value comes directly from the Python pretty-printer object's
29071 @code{display_hint} method. @xref{Pretty Printing API}.
29074 This is an integer attribute which is nonzero if there are children
29075 remaining after the end of the selected range.
29078 @subsubheading Example
29082 -var-list-children n
29083 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29084 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29086 -var-list-children --all-values n
29087 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29088 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29092 @subheading The @code{-var-info-type} Command
29093 @findex -var-info-type
29095 @subsubheading Synopsis
29098 -var-info-type @var{name}
29101 Returns the type of the specified variable @var{name}. The type is
29102 returned as a string in the same format as it is output by the
29106 type=@var{typename}
29110 @subheading The @code{-var-info-expression} Command
29111 @findex -var-info-expression
29113 @subsubheading Synopsis
29116 -var-info-expression @var{name}
29119 Returns a string that is suitable for presenting this
29120 variable object in user interface. The string is generally
29121 not valid expression in the current language, and cannot be evaluated.
29123 For example, if @code{a} is an array, and variable object
29124 @code{A} was created for @code{a}, then we'll get this output:
29127 (gdb) -var-info-expression A.1
29128 ^done,lang="C",exp="1"
29132 Here, the value of @code{lang} is the language name, which can be
29133 found in @ref{Supported Languages}.
29135 Note that the output of the @code{-var-list-children} command also
29136 includes those expressions, so the @code{-var-info-expression} command
29139 @subheading The @code{-var-info-path-expression} Command
29140 @findex -var-info-path-expression
29142 @subsubheading Synopsis
29145 -var-info-path-expression @var{name}
29148 Returns an expression that can be evaluated in the current
29149 context and will yield the same value that a variable object has.
29150 Compare this with the @code{-var-info-expression} command, which
29151 result can be used only for UI presentation. Typical use of
29152 the @code{-var-info-path-expression} command is creating a
29153 watchpoint from a variable object.
29155 This command is currently not valid for children of a dynamic varobj,
29156 and will give an error when invoked on one.
29158 For example, suppose @code{C} is a C@t{++} class, derived from class
29159 @code{Base}, and that the @code{Base} class has a member called
29160 @code{m_size}. Assume a variable @code{c} is has the type of
29161 @code{C} and a variable object @code{C} was created for variable
29162 @code{c}. Then, we'll get this output:
29164 (gdb) -var-info-path-expression C.Base.public.m_size
29165 ^done,path_expr=((Base)c).m_size)
29168 @subheading The @code{-var-show-attributes} Command
29169 @findex -var-show-attributes
29171 @subsubheading Synopsis
29174 -var-show-attributes @var{name}
29177 List attributes of the specified variable object @var{name}:
29180 status=@var{attr} [ ( ,@var{attr} )* ]
29184 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29186 @subheading The @code{-var-evaluate-expression} Command
29187 @findex -var-evaluate-expression
29189 @subsubheading Synopsis
29192 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29195 Evaluates the expression that is represented by the specified variable
29196 object and returns its value as a string. The format of the string
29197 can be specified with the @samp{-f} option. The possible values of
29198 this option are the same as for @code{-var-set-format}
29199 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29200 the current display format will be used. The current display format
29201 can be changed using the @code{-var-set-format} command.
29207 Note that one must invoke @code{-var-list-children} for a variable
29208 before the value of a child variable can be evaluated.
29210 @subheading The @code{-var-assign} Command
29211 @findex -var-assign
29213 @subsubheading Synopsis
29216 -var-assign @var{name} @var{expression}
29219 Assigns the value of @var{expression} to the variable object specified
29220 by @var{name}. The object must be @samp{editable}. If the variable's
29221 value is altered by the assign, the variable will show up in any
29222 subsequent @code{-var-update} list.
29224 @subsubheading Example
29232 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29236 @subheading The @code{-var-update} Command
29237 @findex -var-update
29239 @subsubheading Synopsis
29242 -var-update [@var{print-values}] @{@var{name} | "*"@}
29245 Reevaluate the expressions corresponding to the variable object
29246 @var{name} and all its direct and indirect children, and return the
29247 list of variable objects whose values have changed; @var{name} must
29248 be a root variable object. Here, ``changed'' means that the result of
29249 @code{-var-evaluate-expression} before and after the
29250 @code{-var-update} is different. If @samp{*} is used as the variable
29251 object names, all existing variable objects are updated, except
29252 for frozen ones (@pxref{-var-set-frozen}). The option
29253 @var{print-values} determines whether both names and values, or just
29254 names are printed. The possible values of this option are the same
29255 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29256 recommended to use the @samp{--all-values} option, to reduce the
29257 number of MI commands needed on each program stop.
29259 With the @samp{*} parameter, if a variable object is bound to a
29260 currently running thread, it will not be updated, without any
29263 If @code{-var-set-update-range} was previously used on a varobj, then
29264 only the selected range of children will be reported.
29266 @code{-var-update} reports all the changed varobjs in a tuple named
29269 Each item in the change list is itself a tuple holding:
29273 The name of the varobj.
29276 If values were requested for this update, then this field will be
29277 present and will hold the value of the varobj.
29280 @anchor{-var-update}
29281 This field is a string which may take one of three values:
29285 The variable object's current value is valid.
29288 The variable object does not currently hold a valid value but it may
29289 hold one in the future if its associated expression comes back into
29293 The variable object no longer holds a valid value.
29294 This can occur when the executable file being debugged has changed,
29295 either through recompilation or by using the @value{GDBN} @code{file}
29296 command. The front end should normally choose to delete these variable
29300 In the future new values may be added to this list so the front should
29301 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29304 This is only present if the varobj is still valid. If the type
29305 changed, then this will be the string @samp{true}; otherwise it will
29308 When a varobj's type changes, its children are also likely to have
29309 become incorrect. Therefore, the varobj's children are automatically
29310 deleted when this attribute is @samp{true}. Also, the varobj's update
29311 range, when set using the @code{-var-set-update-range} command, is
29315 If the varobj's type changed, then this field will be present and will
29318 @item new_num_children
29319 For a dynamic varobj, if the number of children changed, or if the
29320 type changed, this will be the new number of children.
29322 The @samp{numchild} field in other varobj responses is generally not
29323 valid for a dynamic varobj -- it will show the number of children that
29324 @value{GDBN} knows about, but because dynamic varobjs lazily
29325 instantiate their children, this will not reflect the number of
29326 children which may be available.
29328 The @samp{new_num_children} attribute only reports changes to the
29329 number of children known by @value{GDBN}. This is the only way to
29330 detect whether an update has removed children (which necessarily can
29331 only happen at the end of the update range).
29334 The display hint, if any.
29337 This is an integer value, which will be 1 if there are more children
29338 available outside the varobj's update range.
29341 This attribute will be present and have the value @samp{1} if the
29342 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29343 then this attribute will not be present.
29346 If new children were added to a dynamic varobj within the selected
29347 update range (as set by @code{-var-set-update-range}), then they will
29348 be listed in this attribute.
29351 @subsubheading Example
29358 -var-update --all-values var1
29359 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29360 type_changed="false"@}]
29364 @subheading The @code{-var-set-frozen} Command
29365 @findex -var-set-frozen
29366 @anchor{-var-set-frozen}
29368 @subsubheading Synopsis
29371 -var-set-frozen @var{name} @var{flag}
29374 Set the frozenness flag on the variable object @var{name}. The
29375 @var{flag} parameter should be either @samp{1} to make the variable
29376 frozen or @samp{0} to make it unfrozen. If a variable object is
29377 frozen, then neither itself, nor any of its children, are
29378 implicitly updated by @code{-var-update} of
29379 a parent variable or by @code{-var-update *}. Only
29380 @code{-var-update} of the variable itself will update its value and
29381 values of its children. After a variable object is unfrozen, it is
29382 implicitly updated by all subsequent @code{-var-update} operations.
29383 Unfreezing a variable does not update it, only subsequent
29384 @code{-var-update} does.
29386 @subsubheading Example
29390 -var-set-frozen V 1
29395 @subheading The @code{-var-set-update-range} command
29396 @findex -var-set-update-range
29397 @anchor{-var-set-update-range}
29399 @subsubheading Synopsis
29402 -var-set-update-range @var{name} @var{from} @var{to}
29405 Set the range of children to be returned by future invocations of
29406 @code{-var-update}.
29408 @var{from} and @var{to} indicate the range of children to report. If
29409 @var{from} or @var{to} is less than zero, the range is reset and all
29410 children will be reported. Otherwise, children starting at @var{from}
29411 (zero-based) and up to and excluding @var{to} will be reported.
29413 @subsubheading Example
29417 -var-set-update-range V 1 2
29421 @subheading The @code{-var-set-visualizer} command
29422 @findex -var-set-visualizer
29423 @anchor{-var-set-visualizer}
29425 @subsubheading Synopsis
29428 -var-set-visualizer @var{name} @var{visualizer}
29431 Set a visualizer for the variable object @var{name}.
29433 @var{visualizer} is the visualizer to use. The special value
29434 @samp{None} means to disable any visualizer in use.
29436 If not @samp{None}, @var{visualizer} must be a Python expression.
29437 This expression must evaluate to a callable object which accepts a
29438 single argument. @value{GDBN} will call this object with the value of
29439 the varobj @var{name} as an argument (this is done so that the same
29440 Python pretty-printing code can be used for both the CLI and MI).
29441 When called, this object must return an object which conforms to the
29442 pretty-printing interface (@pxref{Pretty Printing API}).
29444 The pre-defined function @code{gdb.default_visualizer} may be used to
29445 select a visualizer by following the built-in process
29446 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29447 a varobj is created, and so ordinarily is not needed.
29449 This feature is only available if Python support is enabled. The MI
29450 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29451 can be used to check this.
29453 @subsubheading Example
29455 Resetting the visualizer:
29459 -var-set-visualizer V None
29463 Reselecting the default (type-based) visualizer:
29467 -var-set-visualizer V gdb.default_visualizer
29471 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29472 can be used to instantiate this class for a varobj:
29476 -var-set-visualizer V "lambda val: SomeClass()"
29480 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29481 @node GDB/MI Data Manipulation
29482 @section @sc{gdb/mi} Data Manipulation
29484 @cindex data manipulation, in @sc{gdb/mi}
29485 @cindex @sc{gdb/mi}, data manipulation
29486 This section describes the @sc{gdb/mi} commands that manipulate data:
29487 examine memory and registers, evaluate expressions, etc.
29489 @c REMOVED FROM THE INTERFACE.
29490 @c @subheading -data-assign
29491 @c Change the value of a program variable. Plenty of side effects.
29492 @c @subsubheading GDB Command
29494 @c @subsubheading Example
29497 @subheading The @code{-data-disassemble} Command
29498 @findex -data-disassemble
29500 @subsubheading Synopsis
29504 [ -s @var{start-addr} -e @var{end-addr} ]
29505 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29513 @item @var{start-addr}
29514 is the beginning address (or @code{$pc})
29515 @item @var{end-addr}
29517 @item @var{filename}
29518 is the name of the file to disassemble
29519 @item @var{linenum}
29520 is the line number to disassemble around
29522 is the number of disassembly lines to be produced. If it is -1,
29523 the whole function will be disassembled, in case no @var{end-addr} is
29524 specified. If @var{end-addr} is specified as a non-zero value, and
29525 @var{lines} is lower than the number of disassembly lines between
29526 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29527 displayed; if @var{lines} is higher than the number of lines between
29528 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29531 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29532 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29533 mixed source and disassembly with raw opcodes).
29536 @subsubheading Result
29538 The result of the @code{-data-disassemble} command will be a list named
29539 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29540 used with the @code{-data-disassemble} command.
29542 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29547 The address at which this instruction was disassembled.
29550 The name of the function this instruction is within.
29553 The decimal offset in bytes from the start of @samp{func-name}.
29556 The text disassembly for this @samp{address}.
29559 This field is only present for mode 2. This contains the raw opcode
29560 bytes for the @samp{inst} field.
29564 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
29565 @samp{src_and_asm_line}, each of which has the following fields:
29569 The line number within @samp{file}.
29572 The file name from the compilation unit. This might be an absolute
29573 file name or a relative file name depending on the compile command
29577 Absolute file name of @samp{file}. It is converted to a canonical form
29578 using the source file search path
29579 (@pxref{Source Path, ,Specifying Source Directories})
29580 and after resolving all the symbolic links.
29582 If the source file is not found this field will contain the path as
29583 present in the debug information.
29585 @item line_asm_insn
29586 This is a list of tuples containing the disassembly for @samp{line} in
29587 @samp{file}. The fields of each tuple are the same as for
29588 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29589 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29594 Note that whatever included in the @samp{inst} field, is not
29595 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29598 @subsubheading @value{GDBN} Command
29600 The corresponding @value{GDBN} command is @samp{disassemble}.
29602 @subsubheading Example
29604 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29608 -data-disassemble -s $pc -e "$pc + 20" -- 0
29611 @{address="0x000107c0",func-name="main",offset="4",
29612 inst="mov 2, %o0"@},
29613 @{address="0x000107c4",func-name="main",offset="8",
29614 inst="sethi %hi(0x11800), %o2"@},
29615 @{address="0x000107c8",func-name="main",offset="12",
29616 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29617 @{address="0x000107cc",func-name="main",offset="16",
29618 inst="sethi %hi(0x11800), %o2"@},
29619 @{address="0x000107d0",func-name="main",offset="20",
29620 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29624 Disassemble the whole @code{main} function. Line 32 is part of
29628 -data-disassemble -f basics.c -l 32 -- 0
29630 @{address="0x000107bc",func-name="main",offset="0",
29631 inst="save %sp, -112, %sp"@},
29632 @{address="0x000107c0",func-name="main",offset="4",
29633 inst="mov 2, %o0"@},
29634 @{address="0x000107c4",func-name="main",offset="8",
29635 inst="sethi %hi(0x11800), %o2"@},
29637 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29638 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29642 Disassemble 3 instructions from the start of @code{main}:
29646 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29648 @{address="0x000107bc",func-name="main",offset="0",
29649 inst="save %sp, -112, %sp"@},
29650 @{address="0x000107c0",func-name="main",offset="4",
29651 inst="mov 2, %o0"@},
29652 @{address="0x000107c4",func-name="main",offset="8",
29653 inst="sethi %hi(0x11800), %o2"@}]
29657 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29661 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29663 src_and_asm_line=@{line="31",
29664 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29665 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29666 line_asm_insn=[@{address="0x000107bc",
29667 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29668 src_and_asm_line=@{line="32",
29669 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29670 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29671 line_asm_insn=[@{address="0x000107c0",
29672 func-name="main",offset="4",inst="mov 2, %o0"@},
29673 @{address="0x000107c4",func-name="main",offset="8",
29674 inst="sethi %hi(0x11800), %o2"@}]@}]
29679 @subheading The @code{-data-evaluate-expression} Command
29680 @findex -data-evaluate-expression
29682 @subsubheading Synopsis
29685 -data-evaluate-expression @var{expr}
29688 Evaluate @var{expr} as an expression. The expression could contain an
29689 inferior function call. The function call will execute synchronously.
29690 If the expression contains spaces, it must be enclosed in double quotes.
29692 @subsubheading @value{GDBN} Command
29694 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29695 @samp{call}. In @code{gdbtk} only, there's a corresponding
29696 @samp{gdb_eval} command.
29698 @subsubheading Example
29700 In the following example, the numbers that precede the commands are the
29701 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29702 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29706 211-data-evaluate-expression A
29709 311-data-evaluate-expression &A
29710 311^done,value="0xefffeb7c"
29712 411-data-evaluate-expression A+3
29715 511-data-evaluate-expression "A + 3"
29721 @subheading The @code{-data-list-changed-registers} Command
29722 @findex -data-list-changed-registers
29724 @subsubheading Synopsis
29727 -data-list-changed-registers
29730 Display a list of the registers that have changed.
29732 @subsubheading @value{GDBN} Command
29734 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29735 has the corresponding command @samp{gdb_changed_register_list}.
29737 @subsubheading Example
29739 On a PPC MBX board:
29747 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29748 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29751 -data-list-changed-registers
29752 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29753 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29754 "24","25","26","27","28","30","31","64","65","66","67","69"]
29759 @subheading The @code{-data-list-register-names} Command
29760 @findex -data-list-register-names
29762 @subsubheading Synopsis
29765 -data-list-register-names [ ( @var{regno} )+ ]
29768 Show a list of register names for the current target. If no arguments
29769 are given, it shows a list of the names of all the registers. If
29770 integer numbers are given as arguments, it will print a list of the
29771 names of the registers corresponding to the arguments. To ensure
29772 consistency between a register name and its number, the output list may
29773 include empty register names.
29775 @subsubheading @value{GDBN} Command
29777 @value{GDBN} does not have a command which corresponds to
29778 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29779 corresponding command @samp{gdb_regnames}.
29781 @subsubheading Example
29783 For the PPC MBX board:
29786 -data-list-register-names
29787 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29788 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29789 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29790 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29791 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29792 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29793 "", "pc","ps","cr","lr","ctr","xer"]
29795 -data-list-register-names 1 2 3
29796 ^done,register-names=["r1","r2","r3"]
29800 @subheading The @code{-data-list-register-values} Command
29801 @findex -data-list-register-values
29803 @subsubheading Synopsis
29806 -data-list-register-values
29807 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
29810 Display the registers' contents. The format according to which the
29811 registers' contents are to be returned is given by @var{fmt}, followed
29812 by an optional list of numbers specifying the registers to display. A
29813 missing list of numbers indicates that the contents of all the
29814 registers must be returned. The @code{--skip-unavailable} option
29815 indicates that only the available registers are to be returned.
29817 Allowed formats for @var{fmt} are:
29834 @subsubheading @value{GDBN} Command
29836 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29837 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29839 @subsubheading Example
29841 For a PPC MBX board (note: line breaks are for readability only, they
29842 don't appear in the actual output):
29846 -data-list-register-values r 64 65
29847 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29848 @{number="65",value="0x00029002"@}]
29850 -data-list-register-values x
29851 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29852 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29853 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29854 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29855 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29856 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29857 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29858 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29859 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29860 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29861 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29862 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29863 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29864 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29865 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29866 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29867 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29868 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29869 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29870 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29871 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29872 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29873 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29874 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29875 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29876 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29877 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29878 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29879 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29880 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29881 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29882 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29883 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29884 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29885 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29886 @{number="69",value="0x20002b03"@}]
29891 @subheading The @code{-data-read-memory} Command
29892 @findex -data-read-memory
29894 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29896 @subsubheading Synopsis
29899 -data-read-memory [ -o @var{byte-offset} ]
29900 @var{address} @var{word-format} @var{word-size}
29901 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29908 @item @var{address}
29909 An expression specifying the address of the first memory word to be
29910 read. Complex expressions containing embedded white space should be
29911 quoted using the C convention.
29913 @item @var{word-format}
29914 The format to be used to print the memory words. The notation is the
29915 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29918 @item @var{word-size}
29919 The size of each memory word in bytes.
29921 @item @var{nr-rows}
29922 The number of rows in the output table.
29924 @item @var{nr-cols}
29925 The number of columns in the output table.
29928 If present, indicates that each row should include an @sc{ascii} dump. The
29929 value of @var{aschar} is used as a padding character when a byte is not a
29930 member of the printable @sc{ascii} character set (printable @sc{ascii}
29931 characters are those whose code is between 32 and 126, inclusively).
29933 @item @var{byte-offset}
29934 An offset to add to the @var{address} before fetching memory.
29937 This command displays memory contents as a table of @var{nr-rows} by
29938 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29939 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29940 (returned as @samp{total-bytes}). Should less than the requested number
29941 of bytes be returned by the target, the missing words are identified
29942 using @samp{N/A}. The number of bytes read from the target is returned
29943 in @samp{nr-bytes} and the starting address used to read memory in
29946 The address of the next/previous row or page is available in
29947 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29950 @subsubheading @value{GDBN} Command
29952 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29953 @samp{gdb_get_mem} memory read command.
29955 @subsubheading Example
29957 Read six bytes of memory starting at @code{bytes+6} but then offset by
29958 @code{-6} bytes. Format as three rows of two columns. One byte per
29959 word. Display each word in hex.
29963 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29964 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29965 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29966 prev-page="0x0000138a",memory=[
29967 @{addr="0x00001390",data=["0x00","0x01"]@},
29968 @{addr="0x00001392",data=["0x02","0x03"]@},
29969 @{addr="0x00001394",data=["0x04","0x05"]@}]
29973 Read two bytes of memory starting at address @code{shorts + 64} and
29974 display as a single word formatted in decimal.
29978 5-data-read-memory shorts+64 d 2 1 1
29979 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29980 next-row="0x00001512",prev-row="0x0000150e",
29981 next-page="0x00001512",prev-page="0x0000150e",memory=[
29982 @{addr="0x00001510",data=["128"]@}]
29986 Read thirty two bytes of memory starting at @code{bytes+16} and format
29987 as eight rows of four columns. Include a string encoding with @samp{x}
29988 used as the non-printable character.
29992 4-data-read-memory bytes+16 x 1 8 4 x
29993 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29994 next-row="0x000013c0",prev-row="0x0000139c",
29995 next-page="0x000013c0",prev-page="0x00001380",memory=[
29996 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29997 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29998 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29999 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30000 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30001 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30002 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30003 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30007 @subheading The @code{-data-read-memory-bytes} Command
30008 @findex -data-read-memory-bytes
30010 @subsubheading Synopsis
30013 -data-read-memory-bytes [ -o @var{byte-offset} ]
30014 @var{address} @var{count}
30021 @item @var{address}
30022 An expression specifying the address of the first memory word to be
30023 read. Complex expressions containing embedded white space should be
30024 quoted using the C convention.
30027 The number of bytes to read. This should be an integer literal.
30029 @item @var{byte-offset}
30030 The offsets in bytes relative to @var{address} at which to start
30031 reading. This should be an integer literal. This option is provided
30032 so that a frontend is not required to first evaluate address and then
30033 perform address arithmetics itself.
30037 This command attempts to read all accessible memory regions in the
30038 specified range. First, all regions marked as unreadable in the memory
30039 map (if one is defined) will be skipped. @xref{Memory Region
30040 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30041 regions. For each one, if reading full region results in an errors,
30042 @value{GDBN} will try to read a subset of the region.
30044 In general, every single byte in the region may be readable or not,
30045 and the only way to read every readable byte is to try a read at
30046 every address, which is not practical. Therefore, @value{GDBN} will
30047 attempt to read all accessible bytes at either beginning or the end
30048 of the region, using a binary division scheme. This heuristic works
30049 well for reading accross a memory map boundary. Note that if a region
30050 has a readable range that is neither at the beginning or the end,
30051 @value{GDBN} will not read it.
30053 The result record (@pxref{GDB/MI Result Records}) that is output of
30054 the command includes a field named @samp{memory} whose content is a
30055 list of tuples. Each tuple represent a successfully read memory block
30056 and has the following fields:
30060 The start address of the memory block, as hexadecimal literal.
30063 The end address of the memory block, as hexadecimal literal.
30066 The offset of the memory block, as hexadecimal literal, relative to
30067 the start address passed to @code{-data-read-memory-bytes}.
30070 The contents of the memory block, in hex.
30076 @subsubheading @value{GDBN} Command
30078 The corresponding @value{GDBN} command is @samp{x}.
30080 @subsubheading Example
30084 -data-read-memory-bytes &a 10
30085 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30087 contents="01000000020000000300"@}]
30092 @subheading The @code{-data-write-memory-bytes} Command
30093 @findex -data-write-memory-bytes
30095 @subsubheading Synopsis
30098 -data-write-memory-bytes @var{address} @var{contents}
30099 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30106 @item @var{address}
30107 An expression specifying the address of the first memory word to be
30108 written. Complex expressions containing embedded white space should be
30109 quoted using the C convention.
30111 @item @var{contents}
30112 The hex-encoded bytes to write.
30115 Optional argument indicating the number of bytes to be written. If @var{count}
30116 is greater than @var{contents}' length, @value{GDBN} will repeatedly
30117 write @var{contents} until it fills @var{count} bytes.
30121 @subsubheading @value{GDBN} Command
30123 There's no corresponding @value{GDBN} command.
30125 @subsubheading Example
30129 -data-write-memory-bytes &a "aabbccdd"
30136 -data-write-memory-bytes &a "aabbccdd" 16e
30141 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30142 @node GDB/MI Tracepoint Commands
30143 @section @sc{gdb/mi} Tracepoint Commands
30145 The commands defined in this section implement MI support for
30146 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30148 @subheading The @code{-trace-find} Command
30149 @findex -trace-find
30151 @subsubheading Synopsis
30154 -trace-find @var{mode} [@var{parameters}@dots{}]
30157 Find a trace frame using criteria defined by @var{mode} and
30158 @var{parameters}. The following table lists permissible
30159 modes and their parameters. For details of operation, see @ref{tfind}.
30164 No parameters are required. Stops examining trace frames.
30167 An integer is required as parameter. Selects tracepoint frame with
30170 @item tracepoint-number
30171 An integer is required as parameter. Finds next
30172 trace frame that corresponds to tracepoint with the specified number.
30175 An address is required as parameter. Finds
30176 next trace frame that corresponds to any tracepoint at the specified
30179 @item pc-inside-range
30180 Two addresses are required as parameters. Finds next trace
30181 frame that corresponds to a tracepoint at an address inside the
30182 specified range. Both bounds are considered to be inside the range.
30184 @item pc-outside-range
30185 Two addresses are required as parameters. Finds
30186 next trace frame that corresponds to a tracepoint at an address outside
30187 the specified range. Both bounds are considered to be inside the range.
30190 Line specification is required as parameter. @xref{Specify Location}.
30191 Finds next trace frame that corresponds to a tracepoint at
30192 the specified location.
30196 If @samp{none} was passed as @var{mode}, the response does not
30197 have fields. Otherwise, the response may have the following fields:
30201 This field has either @samp{0} or @samp{1} as the value, depending
30202 on whether a matching tracepoint was found.
30205 The index of the found traceframe. This field is present iff
30206 the @samp{found} field has value of @samp{1}.
30209 The index of the found tracepoint. This field is present iff
30210 the @samp{found} field has value of @samp{1}.
30213 The information about the frame corresponding to the found trace
30214 frame. This field is present only if a trace frame was found.
30215 @xref{GDB/MI Frame Information}, for description of this field.
30219 @subsubheading @value{GDBN} Command
30221 The corresponding @value{GDBN} command is @samp{tfind}.
30223 @subheading -trace-define-variable
30224 @findex -trace-define-variable
30226 @subsubheading Synopsis
30229 -trace-define-variable @var{name} [ @var{value} ]
30232 Create trace variable @var{name} if it does not exist. If
30233 @var{value} is specified, sets the initial value of the specified
30234 trace variable to that value. Note that the @var{name} should start
30235 with the @samp{$} character.
30237 @subsubheading @value{GDBN} Command
30239 The corresponding @value{GDBN} command is @samp{tvariable}.
30241 @subheading The @code{-trace-frame-collected} Command
30242 @findex -trace-frame-collected
30244 @subsubheading Synopsis
30247 -trace-frame-collected
30248 [--var-print-values @var{var_pval}]
30249 [--comp-print-values @var{comp_pval}]
30250 [--registers-format @var{regformat}]
30251 [--memory-contents]
30254 This command returns the set of collected objects, register names,
30255 trace state variable names, memory ranges and computed expressions
30256 that have been collected at a particular trace frame. The optional
30257 parameters to the command affect the output format in different ways.
30258 See the output description table below for more details.
30260 The reported names can be used in the normal manner to create
30261 varobjs and inspect the objects themselves. The items returned by
30262 this command are categorized so that it is clear which is a variable,
30263 which is a register, which is a trace state variable, which is a
30264 memory range and which is a computed expression.
30266 For instance, if the actions were
30268 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30269 collect *(int*)0xaf02bef0@@40
30273 the object collected in its entirety would be @code{myVar}. The
30274 object @code{myArray} would be partially collected, because only the
30275 element at index @code{myIndex} would be collected. The remaining
30276 objects would be computed expressions.
30278 An example output would be:
30282 -trace-frame-collected
30284 explicit-variables=[@{name="myVar",value="1"@}],
30285 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30286 @{name="myObj.field",value="0"@},
30287 @{name="myPtr->field",value="1"@},
30288 @{name="myCount + 2",value="3"@},
30289 @{name="$tvar1 + 1",value="43970027"@}],
30290 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30291 @{number="1",value="0x0"@},
30292 @{number="2",value="0x4"@},
30294 @{number="125",value="0x0"@}],
30295 tvars=[@{name="$tvar1",current="43970026"@}],
30296 memory=[@{address="0x0000000000602264",length="4"@},
30297 @{address="0x0000000000615bc0",length="4"@}]
30304 @item explicit-variables
30305 The set of objects that have been collected in their entirety (as
30306 opposed to collecting just a few elements of an array or a few struct
30307 members). For each object, its name and value are printed.
30308 The @code{--var-print-values} option affects how or whether the value
30309 field is output. If @var{var_pval} is 0, then print only the names;
30310 if it is 1, print also their values; and if it is 2, print the name,
30311 type and value for simple data types, and the name and type for
30312 arrays, structures and unions.
30314 @item computed-expressions
30315 The set of computed expressions that have been collected at the
30316 current trace frame. The @code{--comp-print-values} option affects
30317 this set like the @code{--var-print-values} option affects the
30318 @code{explicit-variables} set. See above.
30321 The registers that have been collected at the current trace frame.
30322 For each register collected, the name and current value are returned.
30323 The value is formatted according to the @code{--registers-format}
30324 option. See the @command{-data-list-register-values} command for a
30325 list of the allowed formats. The default is @samp{x}.
30328 The trace state variables that have been collected at the current
30329 trace frame. For each trace state variable collected, the name and
30330 current value are returned.
30333 The set of memory ranges that have been collected at the current trace
30334 frame. Its content is a list of tuples. Each tuple represents a
30335 collected memory range and has the following fields:
30339 The start address of the memory range, as hexadecimal literal.
30342 The length of the memory range, as decimal literal.
30345 The contents of the memory block, in hex. This field is only present
30346 if the @code{--memory-contents} option is specified.
30352 @subsubheading @value{GDBN} Command
30354 There is no corresponding @value{GDBN} command.
30356 @subsubheading Example
30358 @subheading -trace-list-variables
30359 @findex -trace-list-variables
30361 @subsubheading Synopsis
30364 -trace-list-variables
30367 Return a table of all defined trace variables. Each element of the
30368 table has the following fields:
30372 The name of the trace variable. This field is always present.
30375 The initial value. This is a 64-bit signed integer. This
30376 field is always present.
30379 The value the trace variable has at the moment. This is a 64-bit
30380 signed integer. This field is absent iff current value is
30381 not defined, for example if the trace was never run, or is
30386 @subsubheading @value{GDBN} Command
30388 The corresponding @value{GDBN} command is @samp{tvariables}.
30390 @subsubheading Example
30394 -trace-list-variables
30395 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30396 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30397 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30398 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30399 body=[variable=@{name="$trace_timestamp",initial="0"@}
30400 variable=@{name="$foo",initial="10",current="15"@}]@}
30404 @subheading -trace-save
30405 @findex -trace-save
30407 @subsubheading Synopsis
30410 -trace-save [-r ] @var{filename}
30413 Saves the collected trace data to @var{filename}. Without the
30414 @samp{-r} option, the data is downloaded from the target and saved
30415 in a local file. With the @samp{-r} option the target is asked
30416 to perform the save.
30418 @subsubheading @value{GDBN} Command
30420 The corresponding @value{GDBN} command is @samp{tsave}.
30423 @subheading -trace-start
30424 @findex -trace-start
30426 @subsubheading Synopsis
30432 Starts a tracing experiments. The result of this command does not
30435 @subsubheading @value{GDBN} Command
30437 The corresponding @value{GDBN} command is @samp{tstart}.
30439 @subheading -trace-status
30440 @findex -trace-status
30442 @subsubheading Synopsis
30448 Obtains the status of a tracing experiment. The result may include
30449 the following fields:
30454 May have a value of either @samp{0}, when no tracing operations are
30455 supported, @samp{1}, when all tracing operations are supported, or
30456 @samp{file} when examining trace file. In the latter case, examining
30457 of trace frame is possible but new tracing experiement cannot be
30458 started. This field is always present.
30461 May have a value of either @samp{0} or @samp{1} depending on whether
30462 tracing experiement is in progress on target. This field is present
30463 if @samp{supported} field is not @samp{0}.
30466 Report the reason why the tracing was stopped last time. This field
30467 may be absent iff tracing was never stopped on target yet. The
30468 value of @samp{request} means the tracing was stopped as result of
30469 the @code{-trace-stop} command. The value of @samp{overflow} means
30470 the tracing buffer is full. The value of @samp{disconnection} means
30471 tracing was automatically stopped when @value{GDBN} has disconnected.
30472 The value of @samp{passcount} means tracing was stopped when a
30473 tracepoint was passed a maximal number of times for that tracepoint.
30474 This field is present if @samp{supported} field is not @samp{0}.
30476 @item stopping-tracepoint
30477 The number of tracepoint whose passcount as exceeded. This field is
30478 present iff the @samp{stop-reason} field has the value of
30482 @itemx frames-created
30483 The @samp{frames} field is a count of the total number of trace frames
30484 in the trace buffer, while @samp{frames-created} is the total created
30485 during the run, including ones that were discarded, such as when a
30486 circular trace buffer filled up. Both fields are optional.
30490 These fields tell the current size of the tracing buffer and the
30491 remaining space. These fields are optional.
30494 The value of the circular trace buffer flag. @code{1} means that the
30495 trace buffer is circular and old trace frames will be discarded if
30496 necessary to make room, @code{0} means that the trace buffer is linear
30500 The value of the disconnected tracing flag. @code{1} means that
30501 tracing will continue after @value{GDBN} disconnects, @code{0} means
30502 that the trace run will stop.
30505 The filename of the trace file being examined. This field is
30506 optional, and only present when examining a trace file.
30510 @subsubheading @value{GDBN} Command
30512 The corresponding @value{GDBN} command is @samp{tstatus}.
30514 @subheading -trace-stop
30515 @findex -trace-stop
30517 @subsubheading Synopsis
30523 Stops a tracing experiment. The result of this command has the same
30524 fields as @code{-trace-status}, except that the @samp{supported} and
30525 @samp{running} fields are not output.
30527 @subsubheading @value{GDBN} Command
30529 The corresponding @value{GDBN} command is @samp{tstop}.
30532 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30533 @node GDB/MI Symbol Query
30534 @section @sc{gdb/mi} Symbol Query Commands
30538 @subheading The @code{-symbol-info-address} Command
30539 @findex -symbol-info-address
30541 @subsubheading Synopsis
30544 -symbol-info-address @var{symbol}
30547 Describe where @var{symbol} is stored.
30549 @subsubheading @value{GDBN} Command
30551 The corresponding @value{GDBN} command is @samp{info address}.
30553 @subsubheading Example
30557 @subheading The @code{-symbol-info-file} Command
30558 @findex -symbol-info-file
30560 @subsubheading Synopsis
30566 Show the file for the symbol.
30568 @subsubheading @value{GDBN} Command
30570 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30571 @samp{gdb_find_file}.
30573 @subsubheading Example
30577 @subheading The @code{-symbol-info-function} Command
30578 @findex -symbol-info-function
30580 @subsubheading Synopsis
30583 -symbol-info-function
30586 Show which function the symbol lives in.
30588 @subsubheading @value{GDBN} Command
30590 @samp{gdb_get_function} in @code{gdbtk}.
30592 @subsubheading Example
30596 @subheading The @code{-symbol-info-line} Command
30597 @findex -symbol-info-line
30599 @subsubheading Synopsis
30605 Show the core addresses of the code for a source line.
30607 @subsubheading @value{GDBN} Command
30609 The corresponding @value{GDBN} command is @samp{info line}.
30610 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30612 @subsubheading Example
30616 @subheading The @code{-symbol-info-symbol} Command
30617 @findex -symbol-info-symbol
30619 @subsubheading Synopsis
30622 -symbol-info-symbol @var{addr}
30625 Describe what symbol is at location @var{addr}.
30627 @subsubheading @value{GDBN} Command
30629 The corresponding @value{GDBN} command is @samp{info symbol}.
30631 @subsubheading Example
30635 @subheading The @code{-symbol-list-functions} Command
30636 @findex -symbol-list-functions
30638 @subsubheading Synopsis
30641 -symbol-list-functions
30644 List the functions in the executable.
30646 @subsubheading @value{GDBN} Command
30648 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30649 @samp{gdb_search} in @code{gdbtk}.
30651 @subsubheading Example
30656 @subheading The @code{-symbol-list-lines} Command
30657 @findex -symbol-list-lines
30659 @subsubheading Synopsis
30662 -symbol-list-lines @var{filename}
30665 Print the list of lines that contain code and their associated program
30666 addresses for the given source filename. The entries are sorted in
30667 ascending PC order.
30669 @subsubheading @value{GDBN} Command
30671 There is no corresponding @value{GDBN} command.
30673 @subsubheading Example
30676 -symbol-list-lines basics.c
30677 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30683 @subheading The @code{-symbol-list-types} Command
30684 @findex -symbol-list-types
30686 @subsubheading Synopsis
30692 List all the type names.
30694 @subsubheading @value{GDBN} Command
30696 The corresponding commands are @samp{info types} in @value{GDBN},
30697 @samp{gdb_search} in @code{gdbtk}.
30699 @subsubheading Example
30703 @subheading The @code{-symbol-list-variables} Command
30704 @findex -symbol-list-variables
30706 @subsubheading Synopsis
30709 -symbol-list-variables
30712 List all the global and static variable names.
30714 @subsubheading @value{GDBN} Command
30716 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30718 @subsubheading Example
30722 @subheading The @code{-symbol-locate} Command
30723 @findex -symbol-locate
30725 @subsubheading Synopsis
30731 @subsubheading @value{GDBN} Command
30733 @samp{gdb_loc} in @code{gdbtk}.
30735 @subsubheading Example
30739 @subheading The @code{-symbol-type} Command
30740 @findex -symbol-type
30742 @subsubheading Synopsis
30745 -symbol-type @var{variable}
30748 Show type of @var{variable}.
30750 @subsubheading @value{GDBN} Command
30752 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30753 @samp{gdb_obj_variable}.
30755 @subsubheading Example
30760 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30761 @node GDB/MI File Commands
30762 @section @sc{gdb/mi} File Commands
30764 This section describes the GDB/MI commands to specify executable file names
30765 and to read in and obtain symbol table information.
30767 @subheading The @code{-file-exec-and-symbols} Command
30768 @findex -file-exec-and-symbols
30770 @subsubheading Synopsis
30773 -file-exec-and-symbols @var{file}
30776 Specify the executable file to be debugged. This file is the one from
30777 which the symbol table is also read. If no file is specified, the
30778 command clears the executable and symbol information. If breakpoints
30779 are set when using this command with no arguments, @value{GDBN} will produce
30780 error messages. Otherwise, no output is produced, except a completion
30783 @subsubheading @value{GDBN} Command
30785 The corresponding @value{GDBN} command is @samp{file}.
30787 @subsubheading Example
30791 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30797 @subheading The @code{-file-exec-file} Command
30798 @findex -file-exec-file
30800 @subsubheading Synopsis
30803 -file-exec-file @var{file}
30806 Specify the executable file to be debugged. Unlike
30807 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30808 from this file. If used without argument, @value{GDBN} clears the information
30809 about the executable file. No output is produced, except a completion
30812 @subsubheading @value{GDBN} Command
30814 The corresponding @value{GDBN} command is @samp{exec-file}.
30816 @subsubheading Example
30820 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30827 @subheading The @code{-file-list-exec-sections} Command
30828 @findex -file-list-exec-sections
30830 @subsubheading Synopsis
30833 -file-list-exec-sections
30836 List the sections of the current executable file.
30838 @subsubheading @value{GDBN} Command
30840 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30841 information as this command. @code{gdbtk} has a corresponding command
30842 @samp{gdb_load_info}.
30844 @subsubheading Example
30849 @subheading The @code{-file-list-exec-source-file} Command
30850 @findex -file-list-exec-source-file
30852 @subsubheading Synopsis
30855 -file-list-exec-source-file
30858 List the line number, the current source file, and the absolute path
30859 to the current source file for the current executable. The macro
30860 information field has a value of @samp{1} or @samp{0} depending on
30861 whether or not the file includes preprocessor macro information.
30863 @subsubheading @value{GDBN} Command
30865 The @value{GDBN} equivalent is @samp{info source}
30867 @subsubheading Example
30871 123-file-list-exec-source-file
30872 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30877 @subheading The @code{-file-list-exec-source-files} Command
30878 @findex -file-list-exec-source-files
30880 @subsubheading Synopsis
30883 -file-list-exec-source-files
30886 List the source files for the current executable.
30888 It will always output both the filename and fullname (absolute file
30889 name) of a source file.
30891 @subsubheading @value{GDBN} Command
30893 The @value{GDBN} equivalent is @samp{info sources}.
30894 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30896 @subsubheading Example
30899 -file-list-exec-source-files
30901 @{file=foo.c,fullname=/home/foo.c@},
30902 @{file=/home/bar.c,fullname=/home/bar.c@},
30903 @{file=gdb_could_not_find_fullpath.c@}]
30908 @subheading The @code{-file-list-shared-libraries} Command
30909 @findex -file-list-shared-libraries
30911 @subsubheading Synopsis
30914 -file-list-shared-libraries
30917 List the shared libraries in the program.
30919 @subsubheading @value{GDBN} Command
30921 The corresponding @value{GDBN} command is @samp{info shared}.
30923 @subsubheading Example
30927 @subheading The @code{-file-list-symbol-files} Command
30928 @findex -file-list-symbol-files
30930 @subsubheading Synopsis
30933 -file-list-symbol-files
30938 @subsubheading @value{GDBN} Command
30940 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30942 @subsubheading Example
30947 @subheading The @code{-file-symbol-file} Command
30948 @findex -file-symbol-file
30950 @subsubheading Synopsis
30953 -file-symbol-file @var{file}
30956 Read symbol table info from the specified @var{file} argument. When
30957 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30958 produced, except for a completion notification.
30960 @subsubheading @value{GDBN} Command
30962 The corresponding @value{GDBN} command is @samp{symbol-file}.
30964 @subsubheading Example
30968 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30974 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30975 @node GDB/MI Memory Overlay Commands
30976 @section @sc{gdb/mi} Memory Overlay Commands
30978 The memory overlay commands are not implemented.
30980 @c @subheading -overlay-auto
30982 @c @subheading -overlay-list-mapping-state
30984 @c @subheading -overlay-list-overlays
30986 @c @subheading -overlay-map
30988 @c @subheading -overlay-off
30990 @c @subheading -overlay-on
30992 @c @subheading -overlay-unmap
30994 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30995 @node GDB/MI Signal Handling Commands
30996 @section @sc{gdb/mi} Signal Handling Commands
30998 Signal handling commands are not implemented.
31000 @c @subheading -signal-handle
31002 @c @subheading -signal-list-handle-actions
31004 @c @subheading -signal-list-signal-types
31008 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31009 @node GDB/MI Target Manipulation
31010 @section @sc{gdb/mi} Target Manipulation Commands
31013 @subheading The @code{-target-attach} Command
31014 @findex -target-attach
31016 @subsubheading Synopsis
31019 -target-attach @var{pid} | @var{gid} | @var{file}
31022 Attach to a process @var{pid} or a file @var{file} outside of
31023 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31024 group, the id previously returned by
31025 @samp{-list-thread-groups --available} must be used.
31027 @subsubheading @value{GDBN} Command
31029 The corresponding @value{GDBN} command is @samp{attach}.
31031 @subsubheading Example
31035 =thread-created,id="1"
31036 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31042 @subheading The @code{-target-compare-sections} Command
31043 @findex -target-compare-sections
31045 @subsubheading Synopsis
31048 -target-compare-sections [ @var{section} ]
31051 Compare data of section @var{section} on target to the exec file.
31052 Without the argument, all sections are compared.
31054 @subsubheading @value{GDBN} Command
31056 The @value{GDBN} equivalent is @samp{compare-sections}.
31058 @subsubheading Example
31063 @subheading The @code{-target-detach} Command
31064 @findex -target-detach
31066 @subsubheading Synopsis
31069 -target-detach [ @var{pid} | @var{gid} ]
31072 Detach from the remote target which normally resumes its execution.
31073 If either @var{pid} or @var{gid} is specified, detaches from either
31074 the specified process, or specified thread group. There's no output.
31076 @subsubheading @value{GDBN} Command
31078 The corresponding @value{GDBN} command is @samp{detach}.
31080 @subsubheading Example
31090 @subheading The @code{-target-disconnect} Command
31091 @findex -target-disconnect
31093 @subsubheading Synopsis
31099 Disconnect from the remote target. There's no output and the target is
31100 generally not resumed.
31102 @subsubheading @value{GDBN} Command
31104 The corresponding @value{GDBN} command is @samp{disconnect}.
31106 @subsubheading Example
31116 @subheading The @code{-target-download} Command
31117 @findex -target-download
31119 @subsubheading Synopsis
31125 Loads the executable onto the remote target.
31126 It prints out an update message every half second, which includes the fields:
31130 The name of the section.
31132 The size of what has been sent so far for that section.
31134 The size of the section.
31136 The total size of what was sent so far (the current and the previous sections).
31138 The size of the overall executable to download.
31142 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31143 @sc{gdb/mi} Output Syntax}).
31145 In addition, it prints the name and size of the sections, as they are
31146 downloaded. These messages include the following fields:
31150 The name of the section.
31152 The size of the section.
31154 The size of the overall executable to download.
31158 At the end, a summary is printed.
31160 @subsubheading @value{GDBN} Command
31162 The corresponding @value{GDBN} command is @samp{load}.
31164 @subsubheading Example
31166 Note: each status message appears on a single line. Here the messages
31167 have been broken down so that they can fit onto a page.
31172 +download,@{section=".text",section-size="6668",total-size="9880"@}
31173 +download,@{section=".text",section-sent="512",section-size="6668",
31174 total-sent="512",total-size="9880"@}
31175 +download,@{section=".text",section-sent="1024",section-size="6668",
31176 total-sent="1024",total-size="9880"@}
31177 +download,@{section=".text",section-sent="1536",section-size="6668",
31178 total-sent="1536",total-size="9880"@}
31179 +download,@{section=".text",section-sent="2048",section-size="6668",
31180 total-sent="2048",total-size="9880"@}
31181 +download,@{section=".text",section-sent="2560",section-size="6668",
31182 total-sent="2560",total-size="9880"@}
31183 +download,@{section=".text",section-sent="3072",section-size="6668",
31184 total-sent="3072",total-size="9880"@}
31185 +download,@{section=".text",section-sent="3584",section-size="6668",
31186 total-sent="3584",total-size="9880"@}
31187 +download,@{section=".text",section-sent="4096",section-size="6668",
31188 total-sent="4096",total-size="9880"@}
31189 +download,@{section=".text",section-sent="4608",section-size="6668",
31190 total-sent="4608",total-size="9880"@}
31191 +download,@{section=".text",section-sent="5120",section-size="6668",
31192 total-sent="5120",total-size="9880"@}
31193 +download,@{section=".text",section-sent="5632",section-size="6668",
31194 total-sent="5632",total-size="9880"@}
31195 +download,@{section=".text",section-sent="6144",section-size="6668",
31196 total-sent="6144",total-size="9880"@}
31197 +download,@{section=".text",section-sent="6656",section-size="6668",
31198 total-sent="6656",total-size="9880"@}
31199 +download,@{section=".init",section-size="28",total-size="9880"@}
31200 +download,@{section=".fini",section-size="28",total-size="9880"@}
31201 +download,@{section=".data",section-size="3156",total-size="9880"@}
31202 +download,@{section=".data",section-sent="512",section-size="3156",
31203 total-sent="7236",total-size="9880"@}
31204 +download,@{section=".data",section-sent="1024",section-size="3156",
31205 total-sent="7748",total-size="9880"@}
31206 +download,@{section=".data",section-sent="1536",section-size="3156",
31207 total-sent="8260",total-size="9880"@}
31208 +download,@{section=".data",section-sent="2048",section-size="3156",
31209 total-sent="8772",total-size="9880"@}
31210 +download,@{section=".data",section-sent="2560",section-size="3156",
31211 total-sent="9284",total-size="9880"@}
31212 +download,@{section=".data",section-sent="3072",section-size="3156",
31213 total-sent="9796",total-size="9880"@}
31214 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31221 @subheading The @code{-target-exec-status} Command
31222 @findex -target-exec-status
31224 @subsubheading Synopsis
31227 -target-exec-status
31230 Provide information on the state of the target (whether it is running or
31231 not, for instance).
31233 @subsubheading @value{GDBN} Command
31235 There's no equivalent @value{GDBN} command.
31237 @subsubheading Example
31241 @subheading The @code{-target-list-available-targets} Command
31242 @findex -target-list-available-targets
31244 @subsubheading Synopsis
31247 -target-list-available-targets
31250 List the possible targets to connect to.
31252 @subsubheading @value{GDBN} Command
31254 The corresponding @value{GDBN} command is @samp{help target}.
31256 @subsubheading Example
31260 @subheading The @code{-target-list-current-targets} Command
31261 @findex -target-list-current-targets
31263 @subsubheading Synopsis
31266 -target-list-current-targets
31269 Describe the current target.
31271 @subsubheading @value{GDBN} Command
31273 The corresponding information is printed by @samp{info file} (among
31276 @subsubheading Example
31280 @subheading The @code{-target-list-parameters} Command
31281 @findex -target-list-parameters
31283 @subsubheading Synopsis
31286 -target-list-parameters
31292 @subsubheading @value{GDBN} Command
31296 @subsubheading Example
31300 @subheading The @code{-target-select} Command
31301 @findex -target-select
31303 @subsubheading Synopsis
31306 -target-select @var{type} @var{parameters @dots{}}
31309 Connect @value{GDBN} to the remote target. This command takes two args:
31313 The type of target, for instance @samp{remote}, etc.
31314 @item @var{parameters}
31315 Device names, host names and the like. @xref{Target Commands, ,
31316 Commands for Managing Targets}, for more details.
31319 The output is a connection notification, followed by the address at
31320 which the target program is, in the following form:
31323 ^connected,addr="@var{address}",func="@var{function name}",
31324 args=[@var{arg list}]
31327 @subsubheading @value{GDBN} Command
31329 The corresponding @value{GDBN} command is @samp{target}.
31331 @subsubheading Example
31335 -target-select remote /dev/ttya
31336 ^connected,addr="0xfe00a300",func="??",args=[]
31340 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31341 @node GDB/MI File Transfer Commands
31342 @section @sc{gdb/mi} File Transfer Commands
31345 @subheading The @code{-target-file-put} Command
31346 @findex -target-file-put
31348 @subsubheading Synopsis
31351 -target-file-put @var{hostfile} @var{targetfile}
31354 Copy file @var{hostfile} from the host system (the machine running
31355 @value{GDBN}) to @var{targetfile} on the target system.
31357 @subsubheading @value{GDBN} Command
31359 The corresponding @value{GDBN} command is @samp{remote put}.
31361 @subsubheading Example
31365 -target-file-put localfile remotefile
31371 @subheading The @code{-target-file-get} Command
31372 @findex -target-file-get
31374 @subsubheading Synopsis
31377 -target-file-get @var{targetfile} @var{hostfile}
31380 Copy file @var{targetfile} from the target system to @var{hostfile}
31381 on the host system.
31383 @subsubheading @value{GDBN} Command
31385 The corresponding @value{GDBN} command is @samp{remote get}.
31387 @subsubheading Example
31391 -target-file-get remotefile localfile
31397 @subheading The @code{-target-file-delete} Command
31398 @findex -target-file-delete
31400 @subsubheading Synopsis
31403 -target-file-delete @var{targetfile}
31406 Delete @var{targetfile} from the target system.
31408 @subsubheading @value{GDBN} Command
31410 The corresponding @value{GDBN} command is @samp{remote delete}.
31412 @subsubheading Example
31416 -target-file-delete remotefile
31422 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31423 @node GDB/MI Ada Exceptions Commands
31424 @section Ada Exceptions @sc{gdb/mi} Commands
31426 @subheading The @code{-info-ada-exceptions} Command
31427 @findex -info-ada-exceptions
31429 @subsubheading Synopsis
31432 -info-ada-exceptions [ @var{regexp}]
31435 List all Ada exceptions defined within the program being debugged.
31436 With a regular expression @var{regexp}, only those exceptions whose
31437 names match @var{regexp} are listed.
31439 @subsubheading @value{GDBN} Command
31441 The corresponding @value{GDBN} command is @samp{info exceptions}.
31443 @subsubheading Result
31445 The result is a table of Ada exceptions. The following columns are
31446 defined for each exception:
31450 The name of the exception.
31453 The address of the exception.
31457 @subsubheading Example
31460 -info-ada-exceptions aint
31461 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31462 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31463 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31464 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31465 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31468 @subheading Catching Ada Exceptions
31470 The commands describing how to ask @value{GDBN} to stop when a program
31471 raises an exception are described at @ref{Ada Exception GDB/MI
31472 Catchpoint Commands}.
31475 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31476 @node GDB/MI Support Commands
31477 @section @sc{gdb/mi} Support Commands
31479 Since new commands and features get regularly added to @sc{gdb/mi},
31480 some commands are available to help front-ends query the debugger
31481 about support for these capabilities. Similarly, it is also possible
31482 to query @value{GDBN} about target support of certain features.
31484 @subheading The @code{-info-gdb-mi-command} Command
31485 @cindex @code{-info-gdb-mi-command}
31486 @findex -info-gdb-mi-command
31488 @subsubheading Synopsis
31491 -info-gdb-mi-command @var{cmd_name}
31494 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31496 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31497 is technically not part of the command name (@pxref{GDB/MI Input
31498 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31499 for ease of use, this command also accepts the form with the leading
31502 @subsubheading @value{GDBN} Command
31504 There is no corresponding @value{GDBN} command.
31506 @subsubheading Result
31508 The result is a tuple. There is currently only one field:
31512 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31513 @code{"false"} otherwise.
31517 @subsubheading Example
31519 Here is an example where the @sc{gdb/mi} command does not exist:
31522 -info-gdb-mi-command unsupported-command
31523 ^done,command=@{exists="false"@}
31527 And here is an example where the @sc{gdb/mi} command is known
31531 -info-gdb-mi-command symbol-list-lines
31532 ^done,command=@{exists="true"@}
31535 @subheading The @code{-list-features} Command
31536 @findex -list-features
31537 @cindex supported @sc{gdb/mi} features, list
31539 Returns a list of particular features of the MI protocol that
31540 this version of gdb implements. A feature can be a command,
31541 or a new field in an output of some command, or even an
31542 important bugfix. While a frontend can sometimes detect presence
31543 of a feature at runtime, it is easier to perform detection at debugger
31546 The command returns a list of strings, with each string naming an
31547 available feature. Each returned string is just a name, it does not
31548 have any internal structure. The list of possible feature names
31554 (gdb) -list-features
31555 ^done,result=["feature1","feature2"]
31558 The current list of features is:
31561 @item frozen-varobjs
31562 Indicates support for the @code{-var-set-frozen} command, as well
31563 as possible presense of the @code{frozen} field in the output
31564 of @code{-varobj-create}.
31565 @item pending-breakpoints
31566 Indicates support for the @option{-f} option to the @code{-break-insert}
31569 Indicates Python scripting support, Python-based
31570 pretty-printing commands, and possible presence of the
31571 @samp{display_hint} field in the output of @code{-var-list-children}
31573 Indicates support for the @code{-thread-info} command.
31574 @item data-read-memory-bytes
31575 Indicates support for the @code{-data-read-memory-bytes} and the
31576 @code{-data-write-memory-bytes} commands.
31577 @item breakpoint-notifications
31578 Indicates that changes to breakpoints and breakpoints created via the
31579 CLI will be announced via async records.
31580 @item ada-task-info
31581 Indicates support for the @code{-ada-task-info} command.
31582 @item language-option
31583 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31584 option (@pxref{Context management}).
31585 @item info-gdb-mi-command
31586 Indicates support for the @code{-info-gdb-mi-command} command.
31587 @item undefined-command-error-code
31588 Indicates support for the "undefined-command" error code in error result
31589 records, produced when trying to execute an undefined @sc{gdb/mi} command
31590 (@pxref{GDB/MI Result Records}).
31591 @item exec-run-start-option
31592 Indicates that the @code{-exec-run} command supports the @option{--start}
31593 option (@pxref{GDB/MI Program Execution}).
31596 @subheading The @code{-list-target-features} Command
31597 @findex -list-target-features
31599 Returns a list of particular features that are supported by the
31600 target. Those features affect the permitted MI commands, but
31601 unlike the features reported by the @code{-list-features} command, the
31602 features depend on which target GDB is using at the moment. Whenever
31603 a target can change, due to commands such as @code{-target-select},
31604 @code{-target-attach} or @code{-exec-run}, the list of target features
31605 may change, and the frontend should obtain it again.
31609 (gdb) -list-target-features
31610 ^done,result=["async"]
31613 The current list of features is:
31617 Indicates that the target is capable of asynchronous command
31618 execution, which means that @value{GDBN} will accept further commands
31619 while the target is running.
31622 Indicates that the target is capable of reverse execution.
31623 @xref{Reverse Execution}, for more information.
31627 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31628 @node GDB/MI Miscellaneous Commands
31629 @section Miscellaneous @sc{gdb/mi} Commands
31631 @c @subheading -gdb-complete
31633 @subheading The @code{-gdb-exit} Command
31636 @subsubheading Synopsis
31642 Exit @value{GDBN} immediately.
31644 @subsubheading @value{GDBN} Command
31646 Approximately corresponds to @samp{quit}.
31648 @subsubheading Example
31658 @subheading The @code{-exec-abort} Command
31659 @findex -exec-abort
31661 @subsubheading Synopsis
31667 Kill the inferior running program.
31669 @subsubheading @value{GDBN} Command
31671 The corresponding @value{GDBN} command is @samp{kill}.
31673 @subsubheading Example
31678 @subheading The @code{-gdb-set} Command
31681 @subsubheading Synopsis
31687 Set an internal @value{GDBN} variable.
31688 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31690 @subsubheading @value{GDBN} Command
31692 The corresponding @value{GDBN} command is @samp{set}.
31694 @subsubheading Example
31704 @subheading The @code{-gdb-show} Command
31707 @subsubheading Synopsis
31713 Show the current value of a @value{GDBN} variable.
31715 @subsubheading @value{GDBN} Command
31717 The corresponding @value{GDBN} command is @samp{show}.
31719 @subsubheading Example
31728 @c @subheading -gdb-source
31731 @subheading The @code{-gdb-version} Command
31732 @findex -gdb-version
31734 @subsubheading Synopsis
31740 Show version information for @value{GDBN}. Used mostly in testing.
31742 @subsubheading @value{GDBN} Command
31744 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31745 default shows this information when you start an interactive session.
31747 @subsubheading Example
31749 @c This example modifies the actual output from GDB to avoid overfull
31755 ~Copyright 2000 Free Software Foundation, Inc.
31756 ~GDB is free software, covered by the GNU General Public License, and
31757 ~you are welcome to change it and/or distribute copies of it under
31758 ~ certain conditions.
31759 ~Type "show copying" to see the conditions.
31760 ~There is absolutely no warranty for GDB. Type "show warranty" for
31762 ~This GDB was configured as
31763 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31768 @subheading The @code{-list-thread-groups} Command
31769 @findex -list-thread-groups
31771 @subheading Synopsis
31774 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31777 Lists thread groups (@pxref{Thread groups}). When a single thread
31778 group is passed as the argument, lists the children of that group.
31779 When several thread group are passed, lists information about those
31780 thread groups. Without any parameters, lists information about all
31781 top-level thread groups.
31783 Normally, thread groups that are being debugged are reported.
31784 With the @samp{--available} option, @value{GDBN} reports thread groups
31785 available on the target.
31787 The output of this command may have either a @samp{threads} result or
31788 a @samp{groups} result. The @samp{thread} result has a list of tuples
31789 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31790 Information}). The @samp{groups} result has a list of tuples as value,
31791 each tuple describing a thread group. If top-level groups are
31792 requested (that is, no parameter is passed), or when several groups
31793 are passed, the output always has a @samp{groups} result. The format
31794 of the @samp{group} result is described below.
31796 To reduce the number of roundtrips it's possible to list thread groups
31797 together with their children, by passing the @samp{--recurse} option
31798 and the recursion depth. Presently, only recursion depth of 1 is
31799 permitted. If this option is present, then every reported thread group
31800 will also include its children, either as @samp{group} or
31801 @samp{threads} field.
31803 In general, any combination of option and parameters is permitted, with
31804 the following caveats:
31808 When a single thread group is passed, the output will typically
31809 be the @samp{threads} result. Because threads may not contain
31810 anything, the @samp{recurse} option will be ignored.
31813 When the @samp{--available} option is passed, limited information may
31814 be available. In particular, the list of threads of a process might
31815 be inaccessible. Further, specifying specific thread groups might
31816 not give any performance advantage over listing all thread groups.
31817 The frontend should assume that @samp{-list-thread-groups --available}
31818 is always an expensive operation and cache the results.
31822 The @samp{groups} result is a list of tuples, where each tuple may
31823 have the following fields:
31827 Identifier of the thread group. This field is always present.
31828 The identifier is an opaque string; frontends should not try to
31829 convert it to an integer, even though it might look like one.
31832 The type of the thread group. At present, only @samp{process} is a
31836 The target-specific process identifier. This field is only present
31837 for thread groups of type @samp{process} and only if the process exists.
31840 The exit code of this group's last exited thread, formatted in octal.
31841 This field is only present for thread groups of type @samp{process} and
31842 only if the process is not running.
31845 The number of children this thread group has. This field may be
31846 absent for an available thread group.
31849 This field has a list of tuples as value, each tuple describing a
31850 thread. It may be present if the @samp{--recurse} option is
31851 specified, and it's actually possible to obtain the threads.
31854 This field is a list of integers, each identifying a core that one
31855 thread of the group is running on. This field may be absent if
31856 such information is not available.
31859 The name of the executable file that corresponds to this thread group.
31860 The field is only present for thread groups of type @samp{process},
31861 and only if there is a corresponding executable file.
31865 @subheading Example
31869 -list-thread-groups
31870 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31871 -list-thread-groups 17
31872 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31873 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31874 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31875 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31876 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31877 -list-thread-groups --available
31878 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31879 -list-thread-groups --available --recurse 1
31880 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31881 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31882 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31883 -list-thread-groups --available --recurse 1 17 18
31884 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31885 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31886 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31889 @subheading The @code{-info-os} Command
31892 @subsubheading Synopsis
31895 -info-os [ @var{type} ]
31898 If no argument is supplied, the command returns a table of available
31899 operating-system-specific information types. If one of these types is
31900 supplied as an argument @var{type}, then the command returns a table
31901 of data of that type.
31903 The types of information available depend on the target operating
31906 @subsubheading @value{GDBN} Command
31908 The corresponding @value{GDBN} command is @samp{info os}.
31910 @subsubheading Example
31912 When run on a @sc{gnu}/Linux system, the output will look something
31918 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
31919 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
31920 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
31921 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
31922 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
31924 item=@{col0="files",col1="Listing of all file descriptors",
31925 col2="File descriptors"@},
31926 item=@{col0="modules",col1="Listing of all loaded kernel modules",
31927 col2="Kernel modules"@},
31928 item=@{col0="msg",col1="Listing of all message queues",
31929 col2="Message queues"@},
31930 item=@{col0="processes",col1="Listing of all processes",
31931 col2="Processes"@},
31932 item=@{col0="procgroups",col1="Listing of all process groups",
31933 col2="Process groups"@},
31934 item=@{col0="semaphores",col1="Listing of all semaphores",
31935 col2="Semaphores"@},
31936 item=@{col0="shm",col1="Listing of all shared-memory regions",
31937 col2="Shared-memory regions"@},
31938 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
31940 item=@{col0="threads",col1="Listing of all threads",
31944 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
31945 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
31946 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
31947 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
31948 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
31949 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
31950 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
31951 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
31953 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
31954 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
31958 (Note that the MI output here includes a @code{"Title"} column that
31959 does not appear in command-line @code{info os}; this column is useful
31960 for MI clients that want to enumerate the types of data, such as in a
31961 popup menu, but is needless clutter on the command line, and
31962 @code{info os} omits it.)
31964 @subheading The @code{-add-inferior} Command
31965 @findex -add-inferior
31967 @subheading Synopsis
31973 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31974 inferior is not associated with any executable. Such association may
31975 be established with the @samp{-file-exec-and-symbols} command
31976 (@pxref{GDB/MI File Commands}). The command response has a single
31977 field, @samp{inferior}, whose value is the identifier of the
31978 thread group corresponding to the new inferior.
31980 @subheading Example
31985 ^done,inferior="i3"
31988 @subheading The @code{-interpreter-exec} Command
31989 @findex -interpreter-exec
31991 @subheading Synopsis
31994 -interpreter-exec @var{interpreter} @var{command}
31996 @anchor{-interpreter-exec}
31998 Execute the specified @var{command} in the given @var{interpreter}.
32000 @subheading @value{GDBN} Command
32002 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32004 @subheading Example
32008 -interpreter-exec console "break main"
32009 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32010 &"During symbol reading, bad structure-type format.\n"
32011 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32016 @subheading The @code{-inferior-tty-set} Command
32017 @findex -inferior-tty-set
32019 @subheading Synopsis
32022 -inferior-tty-set /dev/pts/1
32025 Set terminal for future runs of the program being debugged.
32027 @subheading @value{GDBN} Command
32029 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32031 @subheading Example
32035 -inferior-tty-set /dev/pts/1
32040 @subheading The @code{-inferior-tty-show} Command
32041 @findex -inferior-tty-show
32043 @subheading Synopsis
32049 Show terminal for future runs of program being debugged.
32051 @subheading @value{GDBN} Command
32053 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32055 @subheading Example
32059 -inferior-tty-set /dev/pts/1
32063 ^done,inferior_tty_terminal="/dev/pts/1"
32067 @subheading The @code{-enable-timings} Command
32068 @findex -enable-timings
32070 @subheading Synopsis
32073 -enable-timings [yes | no]
32076 Toggle the printing of the wallclock, user and system times for an MI
32077 command as a field in its output. This command is to help frontend
32078 developers optimize the performance of their code. No argument is
32079 equivalent to @samp{yes}.
32081 @subheading @value{GDBN} Command
32085 @subheading Example
32093 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32094 addr="0x080484ed",func="main",file="myprog.c",
32095 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32097 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32105 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32106 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32107 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32108 fullname="/home/nickrob/myprog.c",line="73"@}
32113 @chapter @value{GDBN} Annotations
32115 This chapter describes annotations in @value{GDBN}. Annotations were
32116 designed to interface @value{GDBN} to graphical user interfaces or other
32117 similar programs which want to interact with @value{GDBN} at a
32118 relatively high level.
32120 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32124 This is Edition @value{EDITION}, @value{DATE}.
32128 * Annotations Overview:: What annotations are; the general syntax.
32129 * Server Prefix:: Issuing a command without affecting user state.
32130 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32131 * Errors:: Annotations for error messages.
32132 * Invalidation:: Some annotations describe things now invalid.
32133 * Annotations for Running::
32134 Whether the program is running, how it stopped, etc.
32135 * Source Annotations:: Annotations describing source code.
32138 @node Annotations Overview
32139 @section What is an Annotation?
32140 @cindex annotations
32142 Annotations start with a newline character, two @samp{control-z}
32143 characters, and the name of the annotation. If there is no additional
32144 information associated with this annotation, the name of the annotation
32145 is followed immediately by a newline. If there is additional
32146 information, the name of the annotation is followed by a space, the
32147 additional information, and a newline. The additional information
32148 cannot contain newline characters.
32150 Any output not beginning with a newline and two @samp{control-z}
32151 characters denotes literal output from @value{GDBN}. Currently there is
32152 no need for @value{GDBN} to output a newline followed by two
32153 @samp{control-z} characters, but if there was such a need, the
32154 annotations could be extended with an @samp{escape} annotation which
32155 means those three characters as output.
32157 The annotation @var{level}, which is specified using the
32158 @option{--annotate} command line option (@pxref{Mode Options}), controls
32159 how much information @value{GDBN} prints together with its prompt,
32160 values of expressions, source lines, and other types of output. Level 0
32161 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32162 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32163 for programs that control @value{GDBN}, and level 2 annotations have
32164 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32165 Interface, annotate, GDB's Obsolete Annotations}).
32168 @kindex set annotate
32169 @item set annotate @var{level}
32170 The @value{GDBN} command @code{set annotate} sets the level of
32171 annotations to the specified @var{level}.
32173 @item show annotate
32174 @kindex show annotate
32175 Show the current annotation level.
32178 This chapter describes level 3 annotations.
32180 A simple example of starting up @value{GDBN} with annotations is:
32183 $ @kbd{gdb --annotate=3}
32185 Copyright 2003 Free Software Foundation, Inc.
32186 GDB is free software, covered by the GNU General Public License,
32187 and you are welcome to change it and/or distribute copies of it
32188 under certain conditions.
32189 Type "show copying" to see the conditions.
32190 There is absolutely no warranty for GDB. Type "show warranty"
32192 This GDB was configured as "i386-pc-linux-gnu"
32203 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32204 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32205 denotes a @samp{control-z} character) are annotations; the rest is
32206 output from @value{GDBN}.
32208 @node Server Prefix
32209 @section The Server Prefix
32210 @cindex server prefix
32212 If you prefix a command with @samp{server } then it will not affect
32213 the command history, nor will it affect @value{GDBN}'s notion of which
32214 command to repeat if @key{RET} is pressed on a line by itself. This
32215 means that commands can be run behind a user's back by a front-end in
32216 a transparent manner.
32218 The @code{server } prefix does not affect the recording of values into
32219 the value history; to print a value without recording it into the
32220 value history, use the @code{output} command instead of the
32221 @code{print} command.
32223 Using this prefix also disables confirmation requests
32224 (@pxref{confirmation requests}).
32227 @section Annotation for @value{GDBN} Input
32229 @cindex annotations for prompts
32230 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32231 to know when to send output, when the output from a given command is
32234 Different kinds of input each have a different @dfn{input type}. Each
32235 input type has three annotations: a @code{pre-} annotation, which
32236 denotes the beginning of any prompt which is being output, a plain
32237 annotation, which denotes the end of the prompt, and then a @code{post-}
32238 annotation which denotes the end of any echo which may (or may not) be
32239 associated with the input. For example, the @code{prompt} input type
32240 features the following annotations:
32248 The input types are
32251 @findex pre-prompt annotation
32252 @findex prompt annotation
32253 @findex post-prompt annotation
32255 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32257 @findex pre-commands annotation
32258 @findex commands annotation
32259 @findex post-commands annotation
32261 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32262 command. The annotations are repeated for each command which is input.
32264 @findex pre-overload-choice annotation
32265 @findex overload-choice annotation
32266 @findex post-overload-choice annotation
32267 @item overload-choice
32268 When @value{GDBN} wants the user to select between various overloaded functions.
32270 @findex pre-query annotation
32271 @findex query annotation
32272 @findex post-query annotation
32274 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32276 @findex pre-prompt-for-continue annotation
32277 @findex prompt-for-continue annotation
32278 @findex post-prompt-for-continue annotation
32279 @item prompt-for-continue
32280 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32281 expect this to work well; instead use @code{set height 0} to disable
32282 prompting. This is because the counting of lines is buggy in the
32283 presence of annotations.
32288 @cindex annotations for errors, warnings and interrupts
32290 @findex quit annotation
32295 This annotation occurs right before @value{GDBN} responds to an interrupt.
32297 @findex error annotation
32302 This annotation occurs right before @value{GDBN} responds to an error.
32304 Quit and error annotations indicate that any annotations which @value{GDBN} was
32305 in the middle of may end abruptly. For example, if a
32306 @code{value-history-begin} annotation is followed by a @code{error}, one
32307 cannot expect to receive the matching @code{value-history-end}. One
32308 cannot expect not to receive it either, however; an error annotation
32309 does not necessarily mean that @value{GDBN} is immediately returning all the way
32312 @findex error-begin annotation
32313 A quit or error annotation may be preceded by
32319 Any output between that and the quit or error annotation is the error
32322 Warning messages are not yet annotated.
32323 @c If we want to change that, need to fix warning(), type_error(),
32324 @c range_error(), and possibly other places.
32327 @section Invalidation Notices
32329 @cindex annotations for invalidation messages
32330 The following annotations say that certain pieces of state may have
32334 @findex frames-invalid annotation
32335 @item ^Z^Zframes-invalid
32337 The frames (for example, output from the @code{backtrace} command) may
32340 @findex breakpoints-invalid annotation
32341 @item ^Z^Zbreakpoints-invalid
32343 The breakpoints may have changed. For example, the user just added or
32344 deleted a breakpoint.
32347 @node Annotations for Running
32348 @section Running the Program
32349 @cindex annotations for running programs
32351 @findex starting annotation
32352 @findex stopping annotation
32353 When the program starts executing due to a @value{GDBN} command such as
32354 @code{step} or @code{continue},
32360 is output. When the program stops,
32366 is output. Before the @code{stopped} annotation, a variety of
32367 annotations describe how the program stopped.
32370 @findex exited annotation
32371 @item ^Z^Zexited @var{exit-status}
32372 The program exited, and @var{exit-status} is the exit status (zero for
32373 successful exit, otherwise nonzero).
32375 @findex signalled annotation
32376 @findex signal-name annotation
32377 @findex signal-name-end annotation
32378 @findex signal-string annotation
32379 @findex signal-string-end annotation
32380 @item ^Z^Zsignalled
32381 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32382 annotation continues:
32388 ^Z^Zsignal-name-end
32392 ^Z^Zsignal-string-end
32397 where @var{name} is the name of the signal, such as @code{SIGILL} or
32398 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32399 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32400 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32401 user's benefit and have no particular format.
32403 @findex signal annotation
32405 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32406 just saying that the program received the signal, not that it was
32407 terminated with it.
32409 @findex breakpoint annotation
32410 @item ^Z^Zbreakpoint @var{number}
32411 The program hit breakpoint number @var{number}.
32413 @findex watchpoint annotation
32414 @item ^Z^Zwatchpoint @var{number}
32415 The program hit watchpoint number @var{number}.
32418 @node Source Annotations
32419 @section Displaying Source
32420 @cindex annotations for source display
32422 @findex source annotation
32423 The following annotation is used instead of displaying source code:
32426 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32429 where @var{filename} is an absolute file name indicating which source
32430 file, @var{line} is the line number within that file (where 1 is the
32431 first line in the file), @var{character} is the character position
32432 within the file (where 0 is the first character in the file) (for most
32433 debug formats this will necessarily point to the beginning of a line),
32434 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32435 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32436 @var{addr} is the address in the target program associated with the
32437 source which is being displayed. The @var{addr} is in the form @samp{0x}
32438 followed by one or more lowercase hex digits (note that this does not
32439 depend on the language).
32441 @node JIT Interface
32442 @chapter JIT Compilation Interface
32443 @cindex just-in-time compilation
32444 @cindex JIT compilation interface
32446 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32447 interface. A JIT compiler is a program or library that generates native
32448 executable code at runtime and executes it, usually in order to achieve good
32449 performance while maintaining platform independence.
32451 Programs that use JIT compilation are normally difficult to debug because
32452 portions of their code are generated at runtime, instead of being loaded from
32453 object files, which is where @value{GDBN} normally finds the program's symbols
32454 and debug information. In order to debug programs that use JIT compilation,
32455 @value{GDBN} has an interface that allows the program to register in-memory
32456 symbol files with @value{GDBN} at runtime.
32458 If you are using @value{GDBN} to debug a program that uses this interface, then
32459 it should work transparently so long as you have not stripped the binary. If
32460 you are developing a JIT compiler, then the interface is documented in the rest
32461 of this chapter. At this time, the only known client of this interface is the
32464 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32465 JIT compiler communicates with @value{GDBN} by writing data into a global
32466 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32467 attaches, it reads a linked list of symbol files from the global variable to
32468 find existing code, and puts a breakpoint in the function so that it can find
32469 out about additional code.
32472 * Declarations:: Relevant C struct declarations
32473 * Registering Code:: Steps to register code
32474 * Unregistering Code:: Steps to unregister code
32475 * Custom Debug Info:: Emit debug information in a custom format
32479 @section JIT Declarations
32481 These are the relevant struct declarations that a C program should include to
32482 implement the interface:
32492 struct jit_code_entry
32494 struct jit_code_entry *next_entry;
32495 struct jit_code_entry *prev_entry;
32496 const char *symfile_addr;
32497 uint64_t symfile_size;
32500 struct jit_descriptor
32503 /* This type should be jit_actions_t, but we use uint32_t
32504 to be explicit about the bitwidth. */
32505 uint32_t action_flag;
32506 struct jit_code_entry *relevant_entry;
32507 struct jit_code_entry *first_entry;
32510 /* GDB puts a breakpoint in this function. */
32511 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32513 /* Make sure to specify the version statically, because the
32514 debugger may check the version before we can set it. */
32515 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32518 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32519 modifications to this global data properly, which can easily be done by putting
32520 a global mutex around modifications to these structures.
32522 @node Registering Code
32523 @section Registering Code
32525 To register code with @value{GDBN}, the JIT should follow this protocol:
32529 Generate an object file in memory with symbols and other desired debug
32530 information. The file must include the virtual addresses of the sections.
32533 Create a code entry for the file, which gives the start and size of the symbol
32537 Add it to the linked list in the JIT descriptor.
32540 Point the relevant_entry field of the descriptor at the entry.
32543 Set @code{action_flag} to @code{JIT_REGISTER} and call
32544 @code{__jit_debug_register_code}.
32547 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32548 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32549 new code. However, the linked list must still be maintained in order to allow
32550 @value{GDBN} to attach to a running process and still find the symbol files.
32552 @node Unregistering Code
32553 @section Unregistering Code
32555 If code is freed, then the JIT should use the following protocol:
32559 Remove the code entry corresponding to the code from the linked list.
32562 Point the @code{relevant_entry} field of the descriptor at the code entry.
32565 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32566 @code{__jit_debug_register_code}.
32569 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32570 and the JIT will leak the memory used for the associated symbol files.
32572 @node Custom Debug Info
32573 @section Custom Debug Info
32574 @cindex custom JIT debug info
32575 @cindex JIT debug info reader
32577 Generating debug information in platform-native file formats (like ELF
32578 or COFF) may be an overkill for JIT compilers; especially if all the
32579 debug info is used for is displaying a meaningful backtrace. The
32580 issue can be resolved by having the JIT writers decide on a debug info
32581 format and also provide a reader that parses the debug info generated
32582 by the JIT compiler. This section gives a brief overview on writing
32583 such a parser. More specific details can be found in the source file
32584 @file{gdb/jit-reader.in}, which is also installed as a header at
32585 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32587 The reader is implemented as a shared object (so this functionality is
32588 not available on platforms which don't allow loading shared objects at
32589 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32590 @code{jit-reader-unload} are provided, to be used to load and unload
32591 the readers from a preconfigured directory. Once loaded, the shared
32592 object is used the parse the debug information emitted by the JIT
32596 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32597 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32600 @node Using JIT Debug Info Readers
32601 @subsection Using JIT Debug Info Readers
32602 @kindex jit-reader-load
32603 @kindex jit-reader-unload
32605 Readers can be loaded and unloaded using the @code{jit-reader-load}
32606 and @code{jit-reader-unload} commands.
32609 @item jit-reader-load @var{reader}
32610 Load the JIT reader named @var{reader}, which is a shared
32611 object specified as either an absolute or a relative file name. In
32612 the latter case, @value{GDBN} will try to load the reader from a
32613 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32614 system (here @var{libdir} is the system library directory, often
32615 @file{/usr/local/lib}).
32617 Only one reader can be active at a time; trying to load a second
32618 reader when one is already loaded will result in @value{GDBN}
32619 reporting an error. A new JIT reader can be loaded by first unloading
32620 the current one using @code{jit-reader-unload} and then invoking
32621 @code{jit-reader-load}.
32623 @item jit-reader-unload
32624 Unload the currently loaded JIT reader.
32628 @node Writing JIT Debug Info Readers
32629 @subsection Writing JIT Debug Info Readers
32630 @cindex writing JIT debug info readers
32632 As mentioned, a reader is essentially a shared object conforming to a
32633 certain ABI. This ABI is described in @file{jit-reader.h}.
32635 @file{jit-reader.h} defines the structures, macros and functions
32636 required to write a reader. It is installed (along with
32637 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32638 the system include directory.
32640 Readers need to be released under a GPL compatible license. A reader
32641 can be declared as released under such a license by placing the macro
32642 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32644 The entry point for readers is the symbol @code{gdb_init_reader},
32645 which is expected to be a function with the prototype
32647 @findex gdb_init_reader
32649 extern struct gdb_reader_funcs *gdb_init_reader (void);
32652 @cindex @code{struct gdb_reader_funcs}
32654 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32655 functions. These functions are executed to read the debug info
32656 generated by the JIT compiler (@code{read}), to unwind stack frames
32657 (@code{unwind}) and to create canonical frame IDs
32658 (@code{get_Frame_id}). It also has a callback that is called when the
32659 reader is being unloaded (@code{destroy}). The struct looks like this
32662 struct gdb_reader_funcs
32664 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32665 int reader_version;
32667 /* For use by the reader. */
32670 gdb_read_debug_info *read;
32671 gdb_unwind_frame *unwind;
32672 gdb_get_frame_id *get_frame_id;
32673 gdb_destroy_reader *destroy;
32677 @cindex @code{struct gdb_symbol_callbacks}
32678 @cindex @code{struct gdb_unwind_callbacks}
32680 The callbacks are provided with another set of callbacks by
32681 @value{GDBN} to do their job. For @code{read}, these callbacks are
32682 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32683 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32684 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32685 files and new symbol tables inside those object files. @code{struct
32686 gdb_unwind_callbacks} has callbacks to read registers off the current
32687 frame and to write out the values of the registers in the previous
32688 frame. Both have a callback (@code{target_read}) to read bytes off the
32689 target's address space.
32691 @node In-Process Agent
32692 @chapter In-Process Agent
32693 @cindex debugging agent
32694 The traditional debugging model is conceptually low-speed, but works fine,
32695 because most bugs can be reproduced in debugging-mode execution. However,
32696 as multi-core or many-core processors are becoming mainstream, and
32697 multi-threaded programs become more and more popular, there should be more
32698 and more bugs that only manifest themselves at normal-mode execution, for
32699 example, thread races, because debugger's interference with the program's
32700 timing may conceal the bugs. On the other hand, in some applications,
32701 it is not feasible for the debugger to interrupt the program's execution
32702 long enough for the developer to learn anything helpful about its behavior.
32703 If the program's correctness depends on its real-time behavior, delays
32704 introduced by a debugger might cause the program to fail, even when the
32705 code itself is correct. It is useful to be able to observe the program's
32706 behavior without interrupting it.
32708 Therefore, traditional debugging model is too intrusive to reproduce
32709 some bugs. In order to reduce the interference with the program, we can
32710 reduce the number of operations performed by debugger. The
32711 @dfn{In-Process Agent}, a shared library, is running within the same
32712 process with inferior, and is able to perform some debugging operations
32713 itself. As a result, debugger is only involved when necessary, and
32714 performance of debugging can be improved accordingly. Note that
32715 interference with program can be reduced but can't be removed completely,
32716 because the in-process agent will still stop or slow down the program.
32718 The in-process agent can interpret and execute Agent Expressions
32719 (@pxref{Agent Expressions}) during performing debugging operations. The
32720 agent expressions can be used for different purposes, such as collecting
32721 data in tracepoints, and condition evaluation in breakpoints.
32723 @anchor{Control Agent}
32724 You can control whether the in-process agent is used as an aid for
32725 debugging with the following commands:
32728 @kindex set agent on
32730 Causes the in-process agent to perform some operations on behalf of the
32731 debugger. Just which operations requested by the user will be done
32732 by the in-process agent depends on the its capabilities. For example,
32733 if you request to evaluate breakpoint conditions in the in-process agent,
32734 and the in-process agent has such capability as well, then breakpoint
32735 conditions will be evaluated in the in-process agent.
32737 @kindex set agent off
32738 @item set agent off
32739 Disables execution of debugging operations by the in-process agent. All
32740 of the operations will be performed by @value{GDBN}.
32744 Display the current setting of execution of debugging operations by
32745 the in-process agent.
32749 * In-Process Agent Protocol::
32752 @node In-Process Agent Protocol
32753 @section In-Process Agent Protocol
32754 @cindex in-process agent protocol
32756 The in-process agent is able to communicate with both @value{GDBN} and
32757 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32758 used for communications between @value{GDBN} or GDBserver and the IPA.
32759 In general, @value{GDBN} or GDBserver sends commands
32760 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32761 in-process agent replies back with the return result of the command, or
32762 some other information. The data sent to in-process agent is composed
32763 of primitive data types, such as 4-byte or 8-byte type, and composite
32764 types, which are called objects (@pxref{IPA Protocol Objects}).
32767 * IPA Protocol Objects::
32768 * IPA Protocol Commands::
32771 @node IPA Protocol Objects
32772 @subsection IPA Protocol Objects
32773 @cindex ipa protocol objects
32775 The commands sent to and results received from agent may contain some
32776 complex data types called @dfn{objects}.
32778 The in-process agent is running on the same machine with @value{GDBN}
32779 or GDBserver, so it doesn't have to handle as much differences between
32780 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
32781 However, there are still some differences of two ends in two processes:
32785 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
32786 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
32788 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
32789 GDBserver is compiled with one, and in-process agent is compiled with
32793 Here are the IPA Protocol Objects:
32797 agent expression object. It represents an agent expression
32798 (@pxref{Agent Expressions}).
32799 @anchor{agent expression object}
32801 tracepoint action object. It represents a tracepoint action
32802 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
32803 memory, static trace data and to evaluate expression.
32804 @anchor{tracepoint action object}
32806 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
32807 @anchor{tracepoint object}
32811 The following table describes important attributes of each IPA protocol
32814 @multitable @columnfractions .30 .20 .50
32815 @headitem Name @tab Size @tab Description
32816 @item @emph{agent expression object} @tab @tab
32817 @item length @tab 4 @tab length of bytes code
32818 @item byte code @tab @var{length} @tab contents of byte code
32819 @item @emph{tracepoint action for collecting memory} @tab @tab
32820 @item 'M' @tab 1 @tab type of tracepoint action
32821 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
32822 address of the lowest byte to collect, otherwise @var{addr} is the offset
32823 of @var{basereg} for memory collecting.
32824 @item len @tab 8 @tab length of memory for collecting
32825 @item basereg @tab 4 @tab the register number containing the starting
32826 memory address for collecting.
32827 @item @emph{tracepoint action for collecting registers} @tab @tab
32828 @item 'R' @tab 1 @tab type of tracepoint action
32829 @item @emph{tracepoint action for collecting static trace data} @tab @tab
32830 @item 'L' @tab 1 @tab type of tracepoint action
32831 @item @emph{tracepoint action for expression evaluation} @tab @tab
32832 @item 'X' @tab 1 @tab type of tracepoint action
32833 @item agent expression @tab length of @tab @ref{agent expression object}
32834 @item @emph{tracepoint object} @tab @tab
32835 @item number @tab 4 @tab number of tracepoint
32836 @item address @tab 8 @tab address of tracepoint inserted on
32837 @item type @tab 4 @tab type of tracepoint
32838 @item enabled @tab 1 @tab enable or disable of tracepoint
32839 @item step_count @tab 8 @tab step
32840 @item pass_count @tab 8 @tab pass
32841 @item numactions @tab 4 @tab number of tracepoint actions
32842 @item hit count @tab 8 @tab hit count
32843 @item trace frame usage @tab 8 @tab trace frame usage
32844 @item compiled_cond @tab 8 @tab compiled condition
32845 @item orig_size @tab 8 @tab orig size
32846 @item condition @tab 4 if condition is NULL otherwise length of
32847 @ref{agent expression object}
32848 @tab zero if condition is NULL, otherwise is
32849 @ref{agent expression object}
32850 @item actions @tab variable
32851 @tab numactions number of @ref{tracepoint action object}
32854 @node IPA Protocol Commands
32855 @subsection IPA Protocol Commands
32856 @cindex ipa protocol commands
32858 The spaces in each command are delimiters to ease reading this commands
32859 specification. They don't exist in real commands.
32863 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
32864 Installs a new fast tracepoint described by @var{tracepoint_object}
32865 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
32866 head of @dfn{jumppad}, which is used to jump to data collection routine
32871 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
32872 @var{target_address} is address of tracepoint in the inferior.
32873 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
32874 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
32875 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
32876 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
32883 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
32884 is about to kill inferiors.
32892 @item probe_marker_at:@var{address}
32893 Asks in-process agent to probe the marker at @var{address}.
32900 @item unprobe_marker_at:@var{address}
32901 Asks in-process agent to unprobe the marker at @var{address}.
32905 @chapter Reporting Bugs in @value{GDBN}
32906 @cindex bugs in @value{GDBN}
32907 @cindex reporting bugs in @value{GDBN}
32909 Your bug reports play an essential role in making @value{GDBN} reliable.
32911 Reporting a bug may help you by bringing a solution to your problem, or it
32912 may not. But in any case the principal function of a bug report is to help
32913 the entire community by making the next version of @value{GDBN} work better. Bug
32914 reports are your contribution to the maintenance of @value{GDBN}.
32916 In order for a bug report to serve its purpose, you must include the
32917 information that enables us to fix the bug.
32920 * Bug Criteria:: Have you found a bug?
32921 * Bug Reporting:: How to report bugs
32925 @section Have You Found a Bug?
32926 @cindex bug criteria
32928 If you are not sure whether you have found a bug, here are some guidelines:
32931 @cindex fatal signal
32932 @cindex debugger crash
32933 @cindex crash of debugger
32935 If the debugger gets a fatal signal, for any input whatever, that is a
32936 @value{GDBN} bug. Reliable debuggers never crash.
32938 @cindex error on valid input
32940 If @value{GDBN} produces an error message for valid input, that is a
32941 bug. (Note that if you're cross debugging, the problem may also be
32942 somewhere in the connection to the target.)
32944 @cindex invalid input
32946 If @value{GDBN} does not produce an error message for invalid input,
32947 that is a bug. However, you should note that your idea of
32948 ``invalid input'' might be our idea of ``an extension'' or ``support
32949 for traditional practice''.
32952 If you are an experienced user of debugging tools, your suggestions
32953 for improvement of @value{GDBN} are welcome in any case.
32956 @node Bug Reporting
32957 @section How to Report Bugs
32958 @cindex bug reports
32959 @cindex @value{GDBN} bugs, reporting
32961 A number of companies and individuals offer support for @sc{gnu} products.
32962 If you obtained @value{GDBN} from a support organization, we recommend you
32963 contact that organization first.
32965 You can find contact information for many support companies and
32966 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32968 @c should add a web page ref...
32971 @ifset BUGURL_DEFAULT
32972 In any event, we also recommend that you submit bug reports for
32973 @value{GDBN}. The preferred method is to submit them directly using
32974 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32975 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32978 @strong{Do not send bug reports to @samp{info-gdb}, or to
32979 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32980 not want to receive bug reports. Those that do have arranged to receive
32983 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32984 serves as a repeater. The mailing list and the newsgroup carry exactly
32985 the same messages. Often people think of posting bug reports to the
32986 newsgroup instead of mailing them. This appears to work, but it has one
32987 problem which can be crucial: a newsgroup posting often lacks a mail
32988 path back to the sender. Thus, if we need to ask for more information,
32989 we may be unable to reach you. For this reason, it is better to send
32990 bug reports to the mailing list.
32992 @ifclear BUGURL_DEFAULT
32993 In any event, we also recommend that you submit bug reports for
32994 @value{GDBN} to @value{BUGURL}.
32998 The fundamental principle of reporting bugs usefully is this:
32999 @strong{report all the facts}. If you are not sure whether to state a
33000 fact or leave it out, state it!
33002 Often people omit facts because they think they know what causes the
33003 problem and assume that some details do not matter. Thus, you might
33004 assume that the name of the variable you use in an example does not matter.
33005 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33006 stray memory reference which happens to fetch from the location where that
33007 name is stored in memory; perhaps, if the name were different, the contents
33008 of that location would fool the debugger into doing the right thing despite
33009 the bug. Play it safe and give a specific, complete example. That is the
33010 easiest thing for you to do, and the most helpful.
33012 Keep in mind that the purpose of a bug report is to enable us to fix the
33013 bug. It may be that the bug has been reported previously, but neither
33014 you nor we can know that unless your bug report is complete and
33017 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33018 bell?'' Those bug reports are useless, and we urge everyone to
33019 @emph{refuse to respond to them} except to chide the sender to report
33022 To enable us to fix the bug, you should include all these things:
33026 The version of @value{GDBN}. @value{GDBN} announces it if you start
33027 with no arguments; you can also print it at any time using @code{show
33030 Without this, we will not know whether there is any point in looking for
33031 the bug in the current version of @value{GDBN}.
33034 The type of machine you are using, and the operating system name and
33038 The details of the @value{GDBN} build-time configuration.
33039 @value{GDBN} shows these details if you invoke it with the
33040 @option{--configuration} command-line option, or if you type
33041 @code{show configuration} at @value{GDBN}'s prompt.
33044 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33045 ``@value{GCC}--2.8.1''.
33048 What compiler (and its version) was used to compile the program you are
33049 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33050 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33051 to get this information; for other compilers, see the documentation for
33055 The command arguments you gave the compiler to compile your example and
33056 observe the bug. For example, did you use @samp{-O}? To guarantee
33057 you will not omit something important, list them all. A copy of the
33058 Makefile (or the output from make) is sufficient.
33060 If we were to try to guess the arguments, we would probably guess wrong
33061 and then we might not encounter the bug.
33064 A complete input script, and all necessary source files, that will
33068 A description of what behavior you observe that you believe is
33069 incorrect. For example, ``It gets a fatal signal.''
33071 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33072 will certainly notice it. But if the bug is incorrect output, we might
33073 not notice unless it is glaringly wrong. You might as well not give us
33074 a chance to make a mistake.
33076 Even if the problem you experience is a fatal signal, you should still
33077 say so explicitly. Suppose something strange is going on, such as, your
33078 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33079 the C library on your system. (This has happened!) Your copy might
33080 crash and ours would not. If you told us to expect a crash, then when
33081 ours fails to crash, we would know that the bug was not happening for
33082 us. If you had not told us to expect a crash, then we would not be able
33083 to draw any conclusion from our observations.
33086 @cindex recording a session script
33087 To collect all this information, you can use a session recording program
33088 such as @command{script}, which is available on many Unix systems.
33089 Just run your @value{GDBN} session inside @command{script} and then
33090 include the @file{typescript} file with your bug report.
33092 Another way to record a @value{GDBN} session is to run @value{GDBN}
33093 inside Emacs and then save the entire buffer to a file.
33096 If you wish to suggest changes to the @value{GDBN} source, send us context
33097 diffs. If you even discuss something in the @value{GDBN} source, refer to
33098 it by context, not by line number.
33100 The line numbers in our development sources will not match those in your
33101 sources. Your line numbers would convey no useful information to us.
33105 Here are some things that are not necessary:
33109 A description of the envelope of the bug.
33111 Often people who encounter a bug spend a lot of time investigating
33112 which changes to the input file will make the bug go away and which
33113 changes will not affect it.
33115 This is often time consuming and not very useful, because the way we
33116 will find the bug is by running a single example under the debugger
33117 with breakpoints, not by pure deduction from a series of examples.
33118 We recommend that you save your time for something else.
33120 Of course, if you can find a simpler example to report @emph{instead}
33121 of the original one, that is a convenience for us. Errors in the
33122 output will be easier to spot, running under the debugger will take
33123 less time, and so on.
33125 However, simplification is not vital; if you do not want to do this,
33126 report the bug anyway and send us the entire test case you used.
33129 A patch for the bug.
33131 A patch for the bug does help us if it is a good one. But do not omit
33132 the necessary information, such as the test case, on the assumption that
33133 a patch is all we need. We might see problems with your patch and decide
33134 to fix the problem another way, or we might not understand it at all.
33136 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33137 construct an example that will make the program follow a certain path
33138 through the code. If you do not send us the example, we will not be able
33139 to construct one, so we will not be able to verify that the bug is fixed.
33141 And if we cannot understand what bug you are trying to fix, or why your
33142 patch should be an improvement, we will not install it. A test case will
33143 help us to understand.
33146 A guess about what the bug is or what it depends on.
33148 Such guesses are usually wrong. Even we cannot guess right about such
33149 things without first using the debugger to find the facts.
33152 @c The readline documentation is distributed with the readline code
33153 @c and consists of the two following files:
33156 @c Use -I with makeinfo to point to the appropriate directory,
33157 @c environment var TEXINPUTS with TeX.
33158 @ifclear SYSTEM_READLINE
33159 @include rluser.texi
33160 @include hsuser.texi
33164 @appendix In Memoriam
33166 The @value{GDBN} project mourns the loss of the following long-time
33171 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33172 to Free Software in general. Outside of @value{GDBN}, he was known in
33173 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33175 @item Michael Snyder
33176 Michael was one of the Global Maintainers of the @value{GDBN} project,
33177 with contributions recorded as early as 1996, until 2011. In addition
33178 to his day to day participation, he was a large driving force behind
33179 adding Reverse Debugging to @value{GDBN}.
33182 Beyond their technical contributions to the project, they were also
33183 enjoyable members of the Free Software Community. We will miss them.
33185 @node Formatting Documentation
33186 @appendix Formatting Documentation
33188 @cindex @value{GDBN} reference card
33189 @cindex reference card
33190 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33191 for printing with PostScript or Ghostscript, in the @file{gdb}
33192 subdirectory of the main source directory@footnote{In
33193 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33194 release.}. If you can use PostScript or Ghostscript with your printer,
33195 you can print the reference card immediately with @file{refcard.ps}.
33197 The release also includes the source for the reference card. You
33198 can format it, using @TeX{}, by typing:
33204 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33205 mode on US ``letter'' size paper;
33206 that is, on a sheet 11 inches wide by 8.5 inches
33207 high. You will need to specify this form of printing as an option to
33208 your @sc{dvi} output program.
33210 @cindex documentation
33212 All the documentation for @value{GDBN} comes as part of the machine-readable
33213 distribution. The documentation is written in Texinfo format, which is
33214 a documentation system that uses a single source file to produce both
33215 on-line information and a printed manual. You can use one of the Info
33216 formatting commands to create the on-line version of the documentation
33217 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33219 @value{GDBN} includes an already formatted copy of the on-line Info
33220 version of this manual in the @file{gdb} subdirectory. The main Info
33221 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33222 subordinate files matching @samp{gdb.info*} in the same directory. If
33223 necessary, you can print out these files, or read them with any editor;
33224 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33225 Emacs or the standalone @code{info} program, available as part of the
33226 @sc{gnu} Texinfo distribution.
33228 If you want to format these Info files yourself, you need one of the
33229 Info formatting programs, such as @code{texinfo-format-buffer} or
33232 If you have @code{makeinfo} installed, and are in the top level
33233 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33234 version @value{GDBVN}), you can make the Info file by typing:
33241 If you want to typeset and print copies of this manual, you need @TeX{},
33242 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33243 Texinfo definitions file.
33245 @TeX{} is a typesetting program; it does not print files directly, but
33246 produces output files called @sc{dvi} files. To print a typeset
33247 document, you need a program to print @sc{dvi} files. If your system
33248 has @TeX{} installed, chances are it has such a program. The precise
33249 command to use depends on your system; @kbd{lpr -d} is common; another
33250 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33251 require a file name without any extension or a @samp{.dvi} extension.
33253 @TeX{} also requires a macro definitions file called
33254 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33255 written in Texinfo format. On its own, @TeX{} cannot either read or
33256 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33257 and is located in the @file{gdb-@var{version-number}/texinfo}
33260 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33261 typeset and print this manual. First switch to the @file{gdb}
33262 subdirectory of the main source directory (for example, to
33263 @file{gdb-@value{GDBVN}/gdb}) and type:
33269 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33271 @node Installing GDB
33272 @appendix Installing @value{GDBN}
33273 @cindex installation
33276 * Requirements:: Requirements for building @value{GDBN}
33277 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33278 * Separate Objdir:: Compiling @value{GDBN} in another directory
33279 * Config Names:: Specifying names for hosts and targets
33280 * Configure Options:: Summary of options for configure
33281 * System-wide configuration:: Having a system-wide init file
33285 @section Requirements for Building @value{GDBN}
33286 @cindex building @value{GDBN}, requirements for
33288 Building @value{GDBN} requires various tools and packages to be available.
33289 Other packages will be used only if they are found.
33291 @heading Tools/Packages Necessary for Building @value{GDBN}
33293 @item ISO C90 compiler
33294 @value{GDBN} is written in ISO C90. It should be buildable with any
33295 working C90 compiler, e.g.@: GCC.
33299 @heading Tools/Packages Optional for Building @value{GDBN}
33303 @value{GDBN} can use the Expat XML parsing library. This library may be
33304 included with your operating system distribution; if it is not, you
33305 can get the latest version from @url{http://expat.sourceforge.net}.
33306 The @file{configure} script will search for this library in several
33307 standard locations; if it is installed in an unusual path, you can
33308 use the @option{--with-libexpat-prefix} option to specify its location.
33314 Remote protocol memory maps (@pxref{Memory Map Format})
33316 Target descriptions (@pxref{Target Descriptions})
33318 Remote shared library lists (@xref{Library List Format},
33319 or alternatively @pxref{Library List Format for SVR4 Targets})
33321 MS-Windows shared libraries (@pxref{Shared Libraries})
33323 Traceframe info (@pxref{Traceframe Info Format})
33325 Branch trace (@pxref{Branch Trace Format},
33326 @pxref{Branch Trace Configuration Format})
33330 @cindex compressed debug sections
33331 @value{GDBN} will use the @samp{zlib} library, if available, to read
33332 compressed debug sections. Some linkers, such as GNU gold, are capable
33333 of producing binaries with compressed debug sections. If @value{GDBN}
33334 is compiled with @samp{zlib}, it will be able to read the debug
33335 information in such binaries.
33337 The @samp{zlib} library is likely included with your operating system
33338 distribution; if it is not, you can get the latest version from
33339 @url{http://zlib.net}.
33342 @value{GDBN}'s features related to character sets (@pxref{Character
33343 Sets}) require a functioning @code{iconv} implementation. If you are
33344 on a GNU system, then this is provided by the GNU C Library. Some
33345 other systems also provide a working @code{iconv}.
33347 If @value{GDBN} is using the @code{iconv} program which is installed
33348 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33349 This is done with @option{--with-iconv-bin} which specifies the
33350 directory that contains the @code{iconv} program.
33352 On systems without @code{iconv}, you can install GNU Libiconv. If you
33353 have previously installed Libiconv, you can use the
33354 @option{--with-libiconv-prefix} option to configure.
33356 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33357 arrange to build Libiconv if a directory named @file{libiconv} appears
33358 in the top-most source directory. If Libiconv is built this way, and
33359 if the operating system does not provide a suitable @code{iconv}
33360 implementation, then the just-built library will automatically be used
33361 by @value{GDBN}. One easy way to set this up is to download GNU
33362 Libiconv, unpack it, and then rename the directory holding the
33363 Libiconv source code to @samp{libiconv}.
33366 @node Running Configure
33367 @section Invoking the @value{GDBN} @file{configure} Script
33368 @cindex configuring @value{GDBN}
33369 @value{GDBN} comes with a @file{configure} script that automates the process
33370 of preparing @value{GDBN} for installation; you can then use @code{make} to
33371 build the @code{gdb} program.
33373 @c irrelevant in info file; it's as current as the code it lives with.
33374 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33375 look at the @file{README} file in the sources; we may have improved the
33376 installation procedures since publishing this manual.}
33379 The @value{GDBN} distribution includes all the source code you need for
33380 @value{GDBN} in a single directory, whose name is usually composed by
33381 appending the version number to @samp{gdb}.
33383 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33384 @file{gdb-@value{GDBVN}} directory. That directory contains:
33387 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33388 script for configuring @value{GDBN} and all its supporting libraries
33390 @item gdb-@value{GDBVN}/gdb
33391 the source specific to @value{GDBN} itself
33393 @item gdb-@value{GDBVN}/bfd
33394 source for the Binary File Descriptor library
33396 @item gdb-@value{GDBVN}/include
33397 @sc{gnu} include files
33399 @item gdb-@value{GDBVN}/libiberty
33400 source for the @samp{-liberty} free software library
33402 @item gdb-@value{GDBVN}/opcodes
33403 source for the library of opcode tables and disassemblers
33405 @item gdb-@value{GDBVN}/readline
33406 source for the @sc{gnu} command-line interface
33408 @item gdb-@value{GDBVN}/glob
33409 source for the @sc{gnu} filename pattern-matching subroutine
33411 @item gdb-@value{GDBVN}/mmalloc
33412 source for the @sc{gnu} memory-mapped malloc package
33415 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33416 from the @file{gdb-@var{version-number}} source directory, which in
33417 this example is the @file{gdb-@value{GDBVN}} directory.
33419 First switch to the @file{gdb-@var{version-number}} source directory
33420 if you are not already in it; then run @file{configure}. Pass the
33421 identifier for the platform on which @value{GDBN} will run as an
33427 cd gdb-@value{GDBVN}
33428 ./configure @var{host}
33433 where @var{host} is an identifier such as @samp{sun4} or
33434 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33435 (You can often leave off @var{host}; @file{configure} tries to guess the
33436 correct value by examining your system.)
33438 Running @samp{configure @var{host}} and then running @code{make} builds the
33439 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33440 libraries, then @code{gdb} itself. The configured source files, and the
33441 binaries, are left in the corresponding source directories.
33444 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33445 system does not recognize this automatically when you run a different
33446 shell, you may need to run @code{sh} on it explicitly:
33449 sh configure @var{host}
33452 If you run @file{configure} from a directory that contains source
33453 directories for multiple libraries or programs, such as the
33454 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33456 creates configuration files for every directory level underneath (unless
33457 you tell it not to, with the @samp{--norecursion} option).
33459 You should run the @file{configure} script from the top directory in the
33460 source tree, the @file{gdb-@var{version-number}} directory. If you run
33461 @file{configure} from one of the subdirectories, you will configure only
33462 that subdirectory. That is usually not what you want. In particular,
33463 if you run the first @file{configure} from the @file{gdb} subdirectory
33464 of the @file{gdb-@var{version-number}} directory, you will omit the
33465 configuration of @file{bfd}, @file{readline}, and other sibling
33466 directories of the @file{gdb} subdirectory. This leads to build errors
33467 about missing include files such as @file{bfd/bfd.h}.
33469 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33470 However, you should make sure that the shell on your path (named by
33471 the @samp{SHELL} environment variable) is publicly readable. Remember
33472 that @value{GDBN} uses the shell to start your program---some systems refuse to
33473 let @value{GDBN} debug child processes whose programs are not readable.
33475 @node Separate Objdir
33476 @section Compiling @value{GDBN} in Another Directory
33478 If you want to run @value{GDBN} versions for several host or target machines,
33479 you need a different @code{gdb} compiled for each combination of
33480 host and target. @file{configure} is designed to make this easy by
33481 allowing you to generate each configuration in a separate subdirectory,
33482 rather than in the source directory. If your @code{make} program
33483 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33484 @code{make} in each of these directories builds the @code{gdb}
33485 program specified there.
33487 To build @code{gdb} in a separate directory, run @file{configure}
33488 with the @samp{--srcdir} option to specify where to find the source.
33489 (You also need to specify a path to find @file{configure}
33490 itself from your working directory. If the path to @file{configure}
33491 would be the same as the argument to @samp{--srcdir}, you can leave out
33492 the @samp{--srcdir} option; it is assumed.)
33494 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33495 separate directory for a Sun 4 like this:
33499 cd gdb-@value{GDBVN}
33502 ../gdb-@value{GDBVN}/configure sun4
33507 When @file{configure} builds a configuration using a remote source
33508 directory, it creates a tree for the binaries with the same structure
33509 (and using the same names) as the tree under the source directory. In
33510 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33511 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33512 @file{gdb-sun4/gdb}.
33514 Make sure that your path to the @file{configure} script has just one
33515 instance of @file{gdb} in it. If your path to @file{configure} looks
33516 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33517 one subdirectory of @value{GDBN}, not the whole package. This leads to
33518 build errors about missing include files such as @file{bfd/bfd.h}.
33520 One popular reason to build several @value{GDBN} configurations in separate
33521 directories is to configure @value{GDBN} for cross-compiling (where
33522 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33523 programs that run on another machine---the @dfn{target}).
33524 You specify a cross-debugging target by
33525 giving the @samp{--target=@var{target}} option to @file{configure}.
33527 When you run @code{make} to build a program or library, you must run
33528 it in a configured directory---whatever directory you were in when you
33529 called @file{configure} (or one of its subdirectories).
33531 The @code{Makefile} that @file{configure} generates in each source
33532 directory also runs recursively. If you type @code{make} in a source
33533 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33534 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33535 will build all the required libraries, and then build GDB.
33537 When you have multiple hosts or targets configured in separate
33538 directories, you can run @code{make} on them in parallel (for example,
33539 if they are NFS-mounted on each of the hosts); they will not interfere
33543 @section Specifying Names for Hosts and Targets
33545 The specifications used for hosts and targets in the @file{configure}
33546 script are based on a three-part naming scheme, but some short predefined
33547 aliases are also supported. The full naming scheme encodes three pieces
33548 of information in the following pattern:
33551 @var{architecture}-@var{vendor}-@var{os}
33554 For example, you can use the alias @code{sun4} as a @var{host} argument,
33555 or as the value for @var{target} in a @code{--target=@var{target}}
33556 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33558 The @file{configure} script accompanying @value{GDBN} does not provide
33559 any query facility to list all supported host and target names or
33560 aliases. @file{configure} calls the Bourne shell script
33561 @code{config.sub} to map abbreviations to full names; you can read the
33562 script, if you wish, or you can use it to test your guesses on
33563 abbreviations---for example:
33566 % sh config.sub i386-linux
33568 % sh config.sub alpha-linux
33569 alpha-unknown-linux-gnu
33570 % sh config.sub hp9k700
33572 % sh config.sub sun4
33573 sparc-sun-sunos4.1.1
33574 % sh config.sub sun3
33575 m68k-sun-sunos4.1.1
33576 % sh config.sub i986v
33577 Invalid configuration `i986v': machine `i986v' not recognized
33581 @code{config.sub} is also distributed in the @value{GDBN} source
33582 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33584 @node Configure Options
33585 @section @file{configure} Options
33587 Here is a summary of the @file{configure} options and arguments that
33588 are most often useful for building @value{GDBN}. @file{configure} also has
33589 several other options not listed here. @inforef{What Configure
33590 Does,,configure.info}, for a full explanation of @file{configure}.
33593 configure @r{[}--help@r{]}
33594 @r{[}--prefix=@var{dir}@r{]}
33595 @r{[}--exec-prefix=@var{dir}@r{]}
33596 @r{[}--srcdir=@var{dirname}@r{]}
33597 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33598 @r{[}--target=@var{target}@r{]}
33603 You may introduce options with a single @samp{-} rather than
33604 @samp{--} if you prefer; but you may abbreviate option names if you use
33609 Display a quick summary of how to invoke @file{configure}.
33611 @item --prefix=@var{dir}
33612 Configure the source to install programs and files under directory
33615 @item --exec-prefix=@var{dir}
33616 Configure the source to install programs under directory
33619 @c avoid splitting the warning from the explanation:
33621 @item --srcdir=@var{dirname}
33622 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33623 @code{make} that implements the @code{VPATH} feature.}@*
33624 Use this option to make configurations in directories separate from the
33625 @value{GDBN} source directories. Among other things, you can use this to
33626 build (or maintain) several configurations simultaneously, in separate
33627 directories. @file{configure} writes configuration-specific files in
33628 the current directory, but arranges for them to use the source in the
33629 directory @var{dirname}. @file{configure} creates directories under
33630 the working directory in parallel to the source directories below
33633 @item --norecursion
33634 Configure only the directory level where @file{configure} is executed; do not
33635 propagate configuration to subdirectories.
33637 @item --target=@var{target}
33638 Configure @value{GDBN} for cross-debugging programs running on the specified
33639 @var{target}. Without this option, @value{GDBN} is configured to debug
33640 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33642 There is no convenient way to generate a list of all available targets.
33644 @item @var{host} @dots{}
33645 Configure @value{GDBN} to run on the specified @var{host}.
33647 There is no convenient way to generate a list of all available hosts.
33650 There are many other options available as well, but they are generally
33651 needed for special purposes only.
33653 @node System-wide configuration
33654 @section System-wide configuration and settings
33655 @cindex system-wide init file
33657 @value{GDBN} can be configured to have a system-wide init file;
33658 this file will be read and executed at startup (@pxref{Startup, , What
33659 @value{GDBN} does during startup}).
33661 Here is the corresponding configure option:
33664 @item --with-system-gdbinit=@var{file}
33665 Specify that the default location of the system-wide init file is
33669 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33670 it may be subject to relocation. Two possible cases:
33674 If the default location of this init file contains @file{$prefix},
33675 it will be subject to relocation. Suppose that the configure options
33676 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33677 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33678 init file is looked for as @file{$install/etc/gdbinit} instead of
33679 @file{$prefix/etc/gdbinit}.
33682 By contrast, if the default location does not contain the prefix,
33683 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33684 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33685 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33686 wherever @value{GDBN} is installed.
33689 If the configured location of the system-wide init file (as given by the
33690 @option{--with-system-gdbinit} option at configure time) is in the
33691 data-directory (as specified by @option{--with-gdb-datadir} at configure
33692 time) or in one of its subdirectories, then @value{GDBN} will look for the
33693 system-wide init file in the directory specified by the
33694 @option{--data-directory} command-line option.
33695 Note that the system-wide init file is only read once, during @value{GDBN}
33696 initialization. If the data-directory is changed after @value{GDBN} has
33697 started with the @code{set data-directory} command, the file will not be
33701 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33704 @node System-wide Configuration Scripts
33705 @subsection Installed System-wide Configuration Scripts
33706 @cindex system-wide configuration scripts
33708 The @file{system-gdbinit} directory, located inside the data-directory
33709 (as specified by @option{--with-gdb-datadir} at configure time) contains
33710 a number of scripts which can be used as system-wide init files. To
33711 automatically source those scripts at startup, @value{GDBN} should be
33712 configured with @option{--with-system-gdbinit}. Otherwise, any user
33713 should be able to source them by hand as needed.
33715 The following scripts are currently available:
33718 @item @file{elinos.py}
33720 @cindex ELinOS system-wide configuration script
33721 This script is useful when debugging a program on an ELinOS target.
33722 It takes advantage of the environment variables defined in a standard
33723 ELinOS environment in order to determine the location of the system
33724 shared libraries, and then sets the @samp{solib-absolute-prefix}
33725 and @samp{solib-search-path} variables appropriately.
33727 @item @file{wrs-linux.py}
33728 @pindex wrs-linux.py
33729 @cindex Wind River Linux system-wide configuration script
33730 This script is useful when debugging a program on a target running
33731 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33732 the host-side sysroot used by the target system.
33736 @node Maintenance Commands
33737 @appendix Maintenance Commands
33738 @cindex maintenance commands
33739 @cindex internal commands
33741 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33742 includes a number of commands intended for @value{GDBN} developers,
33743 that are not documented elsewhere in this manual. These commands are
33744 provided here for reference. (For commands that turn on debugging
33745 messages, see @ref{Debugging Output}.)
33748 @kindex maint agent
33749 @kindex maint agent-eval
33750 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33751 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33752 Translate the given @var{expression} into remote agent bytecodes.
33753 This command is useful for debugging the Agent Expression mechanism
33754 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33755 expression useful for data collection, such as by tracepoints, while
33756 @samp{maint agent-eval} produces an expression that evaluates directly
33757 to a result. For instance, a collection expression for @code{globa +
33758 globb} will include bytecodes to record four bytes of memory at each
33759 of the addresses of @code{globa} and @code{globb}, while discarding
33760 the result of the addition, while an evaluation expression will do the
33761 addition and return the sum.
33762 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33763 If not, generate remote agent bytecode for current frame PC address.
33765 @kindex maint agent-printf
33766 @item maint agent-printf @var{format},@var{expr},...
33767 Translate the given format string and list of argument expressions
33768 into remote agent bytecodes and display them as a disassembled list.
33769 This command is useful for debugging the agent version of dynamic
33770 printf (@pxref{Dynamic Printf}).
33772 @kindex maint info breakpoints
33773 @item @anchor{maint info breakpoints}maint info breakpoints
33774 Using the same format as @samp{info breakpoints}, display both the
33775 breakpoints you've set explicitly, and those @value{GDBN} is using for
33776 internal purposes. Internal breakpoints are shown with negative
33777 breakpoint numbers. The type column identifies what kind of breakpoint
33782 Normal, explicitly set breakpoint.
33785 Normal, explicitly set watchpoint.
33788 Internal breakpoint, used to handle correctly stepping through
33789 @code{longjmp} calls.
33791 @item longjmp resume
33792 Internal breakpoint at the target of a @code{longjmp}.
33795 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33798 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33801 Shared library events.
33805 @kindex maint info bfds
33806 @item maint info bfds
33807 This prints information about each @code{bfd} object that is known to
33808 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
33810 @kindex set displaced-stepping
33811 @kindex show displaced-stepping
33812 @cindex displaced stepping support
33813 @cindex out-of-line single-stepping
33814 @item set displaced-stepping
33815 @itemx show displaced-stepping
33816 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33817 if the target supports it. Displaced stepping is a way to single-step
33818 over breakpoints without removing them from the inferior, by executing
33819 an out-of-line copy of the instruction that was originally at the
33820 breakpoint location. It is also known as out-of-line single-stepping.
33823 @item set displaced-stepping on
33824 If the target architecture supports it, @value{GDBN} will use
33825 displaced stepping to step over breakpoints.
33827 @item set displaced-stepping off
33828 @value{GDBN} will not use displaced stepping to step over breakpoints,
33829 even if such is supported by the target architecture.
33831 @cindex non-stop mode, and @samp{set displaced-stepping}
33832 @item set displaced-stepping auto
33833 This is the default mode. @value{GDBN} will use displaced stepping
33834 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33835 architecture supports displaced stepping.
33838 @kindex maint check-psymtabs
33839 @item maint check-psymtabs
33840 Check the consistency of currently expanded psymtabs versus symtabs.
33841 Use this to check, for example, whether a symbol is in one but not the other.
33843 @kindex maint check-symtabs
33844 @item maint check-symtabs
33845 Check the consistency of currently expanded symtabs.
33847 @kindex maint expand-symtabs
33848 @item maint expand-symtabs [@var{regexp}]
33849 Expand symbol tables.
33850 If @var{regexp} is specified, only expand symbol tables for file
33851 names matching @var{regexp}.
33853 @kindex maint set catch-demangler-crashes
33854 @kindex maint show catch-demangler-crashes
33855 @cindex demangler crashes
33856 @item maint set catch-demangler-crashes [on|off]
33857 @itemx maint show catch-demangler-crashes
33858 Control whether @value{GDBN} should attempt to catch crashes in the
33859 symbol name demangler. The default is to attempt to catch crashes.
33860 If enabled, the first time a crash is caught, a core file is created,
33861 the offending symbol is displayed and the user is presented with the
33862 option to terminate the current session.
33864 @kindex maint cplus first_component
33865 @item maint cplus first_component @var{name}
33866 Print the first C@t{++} class/namespace component of @var{name}.
33868 @kindex maint cplus namespace
33869 @item maint cplus namespace
33870 Print the list of possible C@t{++} namespaces.
33872 @kindex maint deprecate
33873 @kindex maint undeprecate
33874 @cindex deprecated commands
33875 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33876 @itemx maint undeprecate @var{command}
33877 Deprecate or undeprecate the named @var{command}. Deprecated commands
33878 cause @value{GDBN} to issue a warning when you use them. The optional
33879 argument @var{replacement} says which newer command should be used in
33880 favor of the deprecated one; if it is given, @value{GDBN} will mention
33881 the replacement as part of the warning.
33883 @kindex maint dump-me
33884 @item maint dump-me
33885 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33886 Cause a fatal signal in the debugger and force it to dump its core.
33887 This is supported only on systems which support aborting a program
33888 with the @code{SIGQUIT} signal.
33890 @kindex maint internal-error
33891 @kindex maint internal-warning
33892 @kindex maint demangler-warning
33893 @cindex demangler crashes
33894 @item maint internal-error @r{[}@var{message-text}@r{]}
33895 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33896 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
33898 Cause @value{GDBN} to call the internal function @code{internal_error},
33899 @code{internal_warning} or @code{demangler_warning} and hence behave
33900 as though an internal problem has been detected. In addition to
33901 reporting the internal problem, these functions give the user the
33902 opportunity to either quit @value{GDBN} or (for @code{internal_error}
33903 and @code{internal_warning}) create a core file of the current
33904 @value{GDBN} session.
33906 These commands take an optional parameter @var{message-text} that is
33907 used as the text of the error or warning message.
33909 Here's an example of using @code{internal-error}:
33912 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33913 @dots{}/maint.c:121: internal-error: testing, 1, 2
33914 A problem internal to GDB has been detected. Further
33915 debugging may prove unreliable.
33916 Quit this debugging session? (y or n) @kbd{n}
33917 Create a core file? (y or n) @kbd{n}
33921 @cindex @value{GDBN} internal error
33922 @cindex internal errors, control of @value{GDBN} behavior
33923 @cindex demangler crashes
33925 @kindex maint set internal-error
33926 @kindex maint show internal-error
33927 @kindex maint set internal-warning
33928 @kindex maint show internal-warning
33929 @kindex maint set demangler-warning
33930 @kindex maint show demangler-warning
33931 @item maint set internal-error @var{action} [ask|yes|no]
33932 @itemx maint show internal-error @var{action}
33933 @itemx maint set internal-warning @var{action} [ask|yes|no]
33934 @itemx maint show internal-warning @var{action}
33935 @itemx maint set demangler-warning @var{action} [ask|yes|no]
33936 @itemx maint show demangler-warning @var{action}
33937 When @value{GDBN} reports an internal problem (error or warning) it
33938 gives the user the opportunity to both quit @value{GDBN} and create a
33939 core file of the current @value{GDBN} session. These commands let you
33940 override the default behaviour for each particular @var{action},
33941 described in the table below.
33945 You can specify that @value{GDBN} should always (yes) or never (no)
33946 quit. The default is to ask the user what to do.
33949 You can specify that @value{GDBN} should always (yes) or never (no)
33950 create a core file. The default is to ask the user what to do. Note
33951 that there is no @code{corefile} option for @code{demangler-warning}:
33952 demangler warnings always create a core file and this cannot be
33956 @kindex maint packet
33957 @item maint packet @var{text}
33958 If @value{GDBN} is talking to an inferior via the serial protocol,
33959 then this command sends the string @var{text} to the inferior, and
33960 displays the response packet. @value{GDBN} supplies the initial
33961 @samp{$} character, the terminating @samp{#} character, and the
33964 @kindex maint print architecture
33965 @item maint print architecture @r{[}@var{file}@r{]}
33966 Print the entire architecture configuration. The optional argument
33967 @var{file} names the file where the output goes.
33969 @kindex maint print c-tdesc
33970 @item maint print c-tdesc
33971 Print the current target description (@pxref{Target Descriptions}) as
33972 a C source file. The created source file can be used in @value{GDBN}
33973 when an XML parser is not available to parse the description.
33975 @kindex maint print dummy-frames
33976 @item maint print dummy-frames
33977 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33980 (@value{GDBP}) @kbd{b add}
33982 (@value{GDBP}) @kbd{print add(2,3)}
33983 Breakpoint 2, add (a=2, b=3) at @dots{}
33985 The program being debugged stopped while in a function called from GDB.
33987 (@value{GDBP}) @kbd{maint print dummy-frames}
33988 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
33992 Takes an optional file parameter.
33994 @kindex maint print registers
33995 @kindex maint print raw-registers
33996 @kindex maint print cooked-registers
33997 @kindex maint print register-groups
33998 @kindex maint print remote-registers
33999 @item maint print registers @r{[}@var{file}@r{]}
34000 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34001 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34002 @itemx maint print register-groups @r{[}@var{file}@r{]}
34003 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34004 Print @value{GDBN}'s internal register data structures.
34006 The command @code{maint print raw-registers} includes the contents of
34007 the raw register cache; the command @code{maint print
34008 cooked-registers} includes the (cooked) value of all registers,
34009 including registers which aren't available on the target nor visible
34010 to user; the command @code{maint print register-groups} includes the
34011 groups that each register is a member of; and the command @code{maint
34012 print remote-registers} includes the remote target's register numbers
34013 and offsets in the `G' packets.
34015 These commands take an optional parameter, a file name to which to
34016 write the information.
34018 @kindex maint print reggroups
34019 @item maint print reggroups @r{[}@var{file}@r{]}
34020 Print @value{GDBN}'s internal register group data structures. The
34021 optional argument @var{file} tells to what file to write the
34024 The register groups info looks like this:
34027 (@value{GDBP}) @kbd{maint print reggroups}
34040 This command forces @value{GDBN} to flush its internal register cache.
34042 @kindex maint print objfiles
34043 @cindex info for known object files
34044 @item maint print objfiles @r{[}@var{regexp}@r{]}
34045 Print a dump of all known object files.
34046 If @var{regexp} is specified, only print object files whose names
34047 match @var{regexp}. For each object file, this command prints its name,
34048 address in memory, and all of its psymtabs and symtabs.
34050 @kindex maint print user-registers
34051 @cindex user registers
34052 @item maint print user-registers
34053 List all currently available @dfn{user registers}. User registers
34054 typically provide alternate names for actual hardware registers. They
34055 include the four ``standard'' registers @code{$fp}, @code{$pc},
34056 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34057 registers can be used in expressions in the same way as the canonical
34058 register names, but only the latter are listed by the @code{info
34059 registers} and @code{maint print registers} commands.
34061 @kindex maint print section-scripts
34062 @cindex info for known .debug_gdb_scripts-loaded scripts
34063 @item maint print section-scripts [@var{regexp}]
34064 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34065 If @var{regexp} is specified, only print scripts loaded by object files
34066 matching @var{regexp}.
34067 For each script, this command prints its name as specified in the objfile,
34068 and the full path if known.
34069 @xref{dotdebug_gdb_scripts section}.
34071 @kindex maint print statistics
34072 @cindex bcache statistics
34073 @item maint print statistics
34074 This command prints, for each object file in the program, various data
34075 about that object file followed by the byte cache (@dfn{bcache})
34076 statistics for the object file. The objfile data includes the number
34077 of minimal, partial, full, and stabs symbols, the number of types
34078 defined by the objfile, the number of as yet unexpanded psym tables,
34079 the number of line tables and string tables, and the amount of memory
34080 used by the various tables. The bcache statistics include the counts,
34081 sizes, and counts of duplicates of all and unique objects, max,
34082 average, and median entry size, total memory used and its overhead and
34083 savings, and various measures of the hash table size and chain
34086 @kindex maint print target-stack
34087 @cindex target stack description
34088 @item maint print target-stack
34089 A @dfn{target} is an interface between the debugger and a particular
34090 kind of file or process. Targets can be stacked in @dfn{strata},
34091 so that more than one target can potentially respond to a request.
34092 In particular, memory accesses will walk down the stack of targets
34093 until they find a target that is interested in handling that particular
34096 This command prints a short description of each layer that was pushed on
34097 the @dfn{target stack}, starting from the top layer down to the bottom one.
34099 @kindex maint print type
34100 @cindex type chain of a data type
34101 @item maint print type @var{expr}
34102 Print the type chain for a type specified by @var{expr}. The argument
34103 can be either a type name or a symbol. If it is a symbol, the type of
34104 that symbol is described. The type chain produced by this command is
34105 a recursive definition of the data type as stored in @value{GDBN}'s
34106 data structures, including its flags and contained types.
34108 @kindex maint set dwarf2 always-disassemble
34109 @kindex maint show dwarf2 always-disassemble
34110 @item maint set dwarf2 always-disassemble
34111 @item maint show dwarf2 always-disassemble
34112 Control the behavior of @code{info address} when using DWARF debugging
34115 The default is @code{off}, which means that @value{GDBN} should try to
34116 describe a variable's location in an easily readable format. When
34117 @code{on}, @value{GDBN} will instead display the DWARF location
34118 expression in an assembly-like format. Note that some locations are
34119 too complex for @value{GDBN} to describe simply; in this case you will
34120 always see the disassembly form.
34122 Here is an example of the resulting disassembly:
34125 (gdb) info addr argc
34126 Symbol "argc" is a complex DWARF expression:
34130 For more information on these expressions, see
34131 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34133 @kindex maint set dwarf2 max-cache-age
34134 @kindex maint show dwarf2 max-cache-age
34135 @item maint set dwarf2 max-cache-age
34136 @itemx maint show dwarf2 max-cache-age
34137 Control the DWARF 2 compilation unit cache.
34139 @cindex DWARF 2 compilation units cache
34140 In object files with inter-compilation-unit references, such as those
34141 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
34142 reader needs to frequently refer to previously read compilation units.
34143 This setting controls how long a compilation unit will remain in the
34144 cache if it is not referenced. A higher limit means that cached
34145 compilation units will be stored in memory longer, and more total
34146 memory will be used. Setting it to zero disables caching, which will
34147 slow down @value{GDBN} startup, but reduce memory consumption.
34149 @kindex maint set profile
34150 @kindex maint show profile
34151 @cindex profiling GDB
34152 @item maint set profile
34153 @itemx maint show profile
34154 Control profiling of @value{GDBN}.
34156 Profiling will be disabled until you use the @samp{maint set profile}
34157 command to enable it. When you enable profiling, the system will begin
34158 collecting timing and execution count data; when you disable profiling or
34159 exit @value{GDBN}, the results will be written to a log file. Remember that
34160 if you use profiling, @value{GDBN} will overwrite the profiling log file
34161 (often called @file{gmon.out}). If you have a record of important profiling
34162 data in a @file{gmon.out} file, be sure to move it to a safe location.
34164 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34165 compiled with the @samp{-pg} compiler option.
34167 @kindex maint set show-debug-regs
34168 @kindex maint show show-debug-regs
34169 @cindex hardware debug registers
34170 @item maint set show-debug-regs
34171 @itemx maint show show-debug-regs
34172 Control whether to show variables that mirror the hardware debug
34173 registers. Use @code{on} to enable, @code{off} to disable. If
34174 enabled, the debug registers values are shown when @value{GDBN} inserts or
34175 removes a hardware breakpoint or watchpoint, and when the inferior
34176 triggers a hardware-assisted breakpoint or watchpoint.
34178 @kindex maint set show-all-tib
34179 @kindex maint show show-all-tib
34180 @item maint set show-all-tib
34181 @itemx maint show show-all-tib
34182 Control whether to show all non zero areas within a 1k block starting
34183 at thread local base, when using the @samp{info w32 thread-information-block}
34186 @kindex maint set target-async
34187 @kindex maint show target-async
34188 @item maint set target-async
34189 @itemx maint show target-async
34190 This controls whether @value{GDBN} targets operate in synchronous or
34191 asynchronous mode (@pxref{Background Execution}). Normally the
34192 default is asynchronous, if it is available; but this can be changed
34193 to more easily debug problems occurring only in synchronous mode.
34195 @kindex maint set per-command
34196 @kindex maint show per-command
34197 @item maint set per-command
34198 @itemx maint show per-command
34199 @cindex resources used by commands
34201 @value{GDBN} can display the resources used by each command.
34202 This is useful in debugging performance problems.
34205 @item maint set per-command space [on|off]
34206 @itemx maint show per-command space
34207 Enable or disable the printing of the memory used by GDB for each command.
34208 If enabled, @value{GDBN} will display how much memory each command
34209 took, following the command's own output.
34210 This can also be requested by invoking @value{GDBN} with the
34211 @option{--statistics} command-line switch (@pxref{Mode Options}).
34213 @item maint set per-command time [on|off]
34214 @itemx maint show per-command time
34215 Enable or disable the printing of the execution time of @value{GDBN}
34217 If enabled, @value{GDBN} will display how much time it
34218 took to execute each command, following the command's own output.
34219 Both CPU time and wallclock time are printed.
34220 Printing both is useful when trying to determine whether the cost is
34221 CPU or, e.g., disk/network latency.
34222 Note that the CPU time printed is for @value{GDBN} only, it does not include
34223 the execution time of the inferior because there's no mechanism currently
34224 to compute how much time was spent by @value{GDBN} and how much time was
34225 spent by the program been debugged.
34226 This can also be requested by invoking @value{GDBN} with the
34227 @option{--statistics} command-line switch (@pxref{Mode Options}).
34229 @item maint set per-command symtab [on|off]
34230 @itemx maint show per-command symtab
34231 Enable or disable the printing of basic symbol table statistics
34233 If enabled, @value{GDBN} will display the following information:
34237 number of symbol tables
34239 number of primary symbol tables
34241 number of blocks in the blockvector
34245 @kindex maint space
34246 @cindex memory used by commands
34247 @item maint space @var{value}
34248 An alias for @code{maint set per-command space}.
34249 A non-zero value enables it, zero disables it.
34252 @cindex time of command execution
34253 @item maint time @var{value}
34254 An alias for @code{maint set per-command time}.
34255 A non-zero value enables it, zero disables it.
34257 @kindex maint translate-address
34258 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34259 Find the symbol stored at the location specified by the address
34260 @var{addr} and an optional section name @var{section}. If found,
34261 @value{GDBN} prints the name of the closest symbol and an offset from
34262 the symbol's location to the specified address. This is similar to
34263 the @code{info address} command (@pxref{Symbols}), except that this
34264 command also allows to find symbols in other sections.
34266 If section was not specified, the section in which the symbol was found
34267 is also printed. For dynamically linked executables, the name of
34268 executable or shared library containing the symbol is printed as well.
34272 The following command is useful for non-interactive invocations of
34273 @value{GDBN}, such as in the test suite.
34276 @item set watchdog @var{nsec}
34277 @kindex set watchdog
34278 @cindex watchdog timer
34279 @cindex timeout for commands
34280 Set the maximum number of seconds @value{GDBN} will wait for the
34281 target operation to finish. If this time expires, @value{GDBN}
34282 reports and error and the command is aborted.
34284 @item show watchdog
34285 Show the current setting of the target wait timeout.
34288 @node Remote Protocol
34289 @appendix @value{GDBN} Remote Serial Protocol
34294 * Stop Reply Packets::
34295 * General Query Packets::
34296 * Architecture-Specific Protocol Details::
34297 * Tracepoint Packets::
34298 * Host I/O Packets::
34300 * Notification Packets::
34301 * Remote Non-Stop::
34302 * Packet Acknowledgment::
34304 * File-I/O Remote Protocol Extension::
34305 * Library List Format::
34306 * Library List Format for SVR4 Targets::
34307 * Memory Map Format::
34308 * Thread List Format::
34309 * Traceframe Info Format::
34310 * Branch Trace Format::
34311 * Branch Trace Configuration Format::
34317 There may be occasions when you need to know something about the
34318 protocol---for example, if there is only one serial port to your target
34319 machine, you might want your program to do something special if it
34320 recognizes a packet meant for @value{GDBN}.
34322 In the examples below, @samp{->} and @samp{<-} are used to indicate
34323 transmitted and received data, respectively.
34325 @cindex protocol, @value{GDBN} remote serial
34326 @cindex serial protocol, @value{GDBN} remote
34327 @cindex remote serial protocol
34328 All @value{GDBN} commands and responses (other than acknowledgments
34329 and notifications, see @ref{Notification Packets}) are sent as a
34330 @var{packet}. A @var{packet} is introduced with the character
34331 @samp{$}, the actual @var{packet-data}, and the terminating character
34332 @samp{#} followed by a two-digit @var{checksum}:
34335 @code{$}@var{packet-data}@code{#}@var{checksum}
34339 @cindex checksum, for @value{GDBN} remote
34341 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34342 characters between the leading @samp{$} and the trailing @samp{#} (an
34343 eight bit unsigned checksum).
34345 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34346 specification also included an optional two-digit @var{sequence-id}:
34349 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34352 @cindex sequence-id, for @value{GDBN} remote
34354 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34355 has never output @var{sequence-id}s. Stubs that handle packets added
34356 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34358 When either the host or the target machine receives a packet, the first
34359 response expected is an acknowledgment: either @samp{+} (to indicate
34360 the package was received correctly) or @samp{-} (to request
34364 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34369 The @samp{+}/@samp{-} acknowledgments can be disabled
34370 once a connection is established.
34371 @xref{Packet Acknowledgment}, for details.
34373 The host (@value{GDBN}) sends @var{command}s, and the target (the
34374 debugging stub incorporated in your program) sends a @var{response}. In
34375 the case of step and continue @var{command}s, the response is only sent
34376 when the operation has completed, and the target has again stopped all
34377 threads in all attached processes. This is the default all-stop mode
34378 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34379 execution mode; see @ref{Remote Non-Stop}, for details.
34381 @var{packet-data} consists of a sequence of characters with the
34382 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34385 @cindex remote protocol, field separator
34386 Fields within the packet should be separated using @samp{,} @samp{;} or
34387 @samp{:}. Except where otherwise noted all numbers are represented in
34388 @sc{hex} with leading zeros suppressed.
34390 Implementors should note that prior to @value{GDBN} 5.0, the character
34391 @samp{:} could not appear as the third character in a packet (as it
34392 would potentially conflict with the @var{sequence-id}).
34394 @cindex remote protocol, binary data
34395 @anchor{Binary Data}
34396 Binary data in most packets is encoded either as two hexadecimal
34397 digits per byte of binary data. This allowed the traditional remote
34398 protocol to work over connections which were only seven-bit clean.
34399 Some packets designed more recently assume an eight-bit clean
34400 connection, and use a more efficient encoding to send and receive
34403 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34404 as an escape character. Any escaped byte is transmitted as the escape
34405 character followed by the original character XORed with @code{0x20}.
34406 For example, the byte @code{0x7d} would be transmitted as the two
34407 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34408 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34409 @samp{@}}) must always be escaped. Responses sent by the stub
34410 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34411 is not interpreted as the start of a run-length encoded sequence
34414 Response @var{data} can be run-length encoded to save space.
34415 Run-length encoding replaces runs of identical characters with one
34416 instance of the repeated character, followed by a @samp{*} and a
34417 repeat count. The repeat count is itself sent encoded, to avoid
34418 binary characters in @var{data}: a value of @var{n} is sent as
34419 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34420 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34421 code 32) for a repeat count of 3. (This is because run-length
34422 encoding starts to win for counts 3 or more.) Thus, for example,
34423 @samp{0* } is a run-length encoding of ``0000'': the space character
34424 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34427 The printable characters @samp{#} and @samp{$} or with a numeric value
34428 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34429 seven repeats (@samp{$}) can be expanded using a repeat count of only
34430 five (@samp{"}). For example, @samp{00000000} can be encoded as
34433 The error response returned for some packets includes a two character
34434 error number. That number is not well defined.
34436 @cindex empty response, for unsupported packets
34437 For any @var{command} not supported by the stub, an empty response
34438 (@samp{$#00}) should be returned. That way it is possible to extend the
34439 protocol. A newer @value{GDBN} can tell if a packet is supported based
34442 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34443 commands for register access, and the @samp{m} and @samp{M} commands
34444 for memory access. Stubs that only control single-threaded targets
34445 can implement run control with the @samp{c} (continue), and @samp{s}
34446 (step) commands. Stubs that support multi-threading targets should
34447 support the @samp{vCont} command. All other commands are optional.
34452 The following table provides a complete list of all currently defined
34453 @var{command}s and their corresponding response @var{data}.
34454 @xref{File-I/O Remote Protocol Extension}, for details about the File
34455 I/O extension of the remote protocol.
34457 Each packet's description has a template showing the packet's overall
34458 syntax, followed by an explanation of the packet's meaning. We
34459 include spaces in some of the templates for clarity; these are not
34460 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34461 separate its components. For example, a template like @samp{foo
34462 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34463 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34464 @var{baz}. @value{GDBN} does not transmit a space character between the
34465 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34468 @cindex @var{thread-id}, in remote protocol
34469 @anchor{thread-id syntax}
34470 Several packets and replies include a @var{thread-id} field to identify
34471 a thread. Normally these are positive numbers with a target-specific
34472 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34473 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34476 In addition, the remote protocol supports a multiprocess feature in
34477 which the @var{thread-id} syntax is extended to optionally include both
34478 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34479 The @var{pid} (process) and @var{tid} (thread) components each have the
34480 format described above: a positive number with target-specific
34481 interpretation formatted as a big-endian hex string, literal @samp{-1}
34482 to indicate all processes or threads (respectively), or @samp{0} to
34483 indicate an arbitrary process or thread. Specifying just a process, as
34484 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34485 error to specify all processes but a specific thread, such as
34486 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34487 for those packets and replies explicitly documented to include a process
34488 ID, rather than a @var{thread-id}.
34490 The multiprocess @var{thread-id} syntax extensions are only used if both
34491 @value{GDBN} and the stub report support for the @samp{multiprocess}
34492 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34495 Note that all packet forms beginning with an upper- or lower-case
34496 letter, other than those described here, are reserved for future use.
34498 Here are the packet descriptions.
34503 @cindex @samp{!} packet
34504 @anchor{extended mode}
34505 Enable extended mode. In extended mode, the remote server is made
34506 persistent. The @samp{R} packet is used to restart the program being
34512 The remote target both supports and has enabled extended mode.
34516 @cindex @samp{?} packet
34518 Indicate the reason the target halted. The reply is the same as for
34519 step and continue. This packet has a special interpretation when the
34520 target is in non-stop mode; see @ref{Remote Non-Stop}.
34523 @xref{Stop Reply Packets}, for the reply specifications.
34525 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34526 @cindex @samp{A} packet
34527 Initialized @code{argv[]} array passed into program. @var{arglen}
34528 specifies the number of bytes in the hex encoded byte stream
34529 @var{arg}. See @code{gdbserver} for more details.
34534 The arguments were set.
34540 @cindex @samp{b} packet
34541 (Don't use this packet; its behavior is not well-defined.)
34542 Change the serial line speed to @var{baud}.
34544 JTC: @emph{When does the transport layer state change? When it's
34545 received, or after the ACK is transmitted. In either case, there are
34546 problems if the command or the acknowledgment packet is dropped.}
34548 Stan: @emph{If people really wanted to add something like this, and get
34549 it working for the first time, they ought to modify ser-unix.c to send
34550 some kind of out-of-band message to a specially-setup stub and have the
34551 switch happen "in between" packets, so that from remote protocol's point
34552 of view, nothing actually happened.}
34554 @item B @var{addr},@var{mode}
34555 @cindex @samp{B} packet
34556 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34557 breakpoint at @var{addr}.
34559 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34560 (@pxref{insert breakpoint or watchpoint packet}).
34562 @cindex @samp{bc} packet
34565 Backward continue. Execute the target system in reverse. No parameter.
34566 @xref{Reverse Execution}, for more information.
34569 @xref{Stop Reply Packets}, for the reply specifications.
34571 @cindex @samp{bs} packet
34574 Backward single step. Execute one instruction in reverse. No parameter.
34575 @xref{Reverse Execution}, for more information.
34578 @xref{Stop Reply Packets}, for the reply specifications.
34580 @item c @r{[}@var{addr}@r{]}
34581 @cindex @samp{c} packet
34582 Continue at @var{addr}, which is the address to resume. If @var{addr}
34583 is omitted, resume at current address.
34585 This packet is deprecated for multi-threading support. @xref{vCont
34589 @xref{Stop Reply Packets}, for the reply specifications.
34591 @item C @var{sig}@r{[};@var{addr}@r{]}
34592 @cindex @samp{C} packet
34593 Continue with signal @var{sig} (hex signal number). If
34594 @samp{;@var{addr}} is omitted, resume at same address.
34596 This packet is deprecated for multi-threading support. @xref{vCont
34600 @xref{Stop Reply Packets}, for the reply specifications.
34603 @cindex @samp{d} packet
34606 Don't use this packet; instead, define a general set packet
34607 (@pxref{General Query Packets}).
34611 @cindex @samp{D} packet
34612 The first form of the packet is used to detach @value{GDBN} from the
34613 remote system. It is sent to the remote target
34614 before @value{GDBN} disconnects via the @code{detach} command.
34616 The second form, including a process ID, is used when multiprocess
34617 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34618 detach only a specific process. The @var{pid} is specified as a
34619 big-endian hex string.
34629 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34630 @cindex @samp{F} packet
34631 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34632 This is part of the File-I/O protocol extension. @xref{File-I/O
34633 Remote Protocol Extension}, for the specification.
34636 @anchor{read registers packet}
34637 @cindex @samp{g} packet
34638 Read general registers.
34642 @item @var{XX@dots{}}
34643 Each byte of register data is described by two hex digits. The bytes
34644 with the register are transmitted in target byte order. The size of
34645 each register and their position within the @samp{g} packet are
34646 determined by the @value{GDBN} internal gdbarch functions
34647 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34648 specification of several standard @samp{g} packets is specified below.
34650 When reading registers from a trace frame (@pxref{Analyze Collected
34651 Data,,Using the Collected Data}), the stub may also return a string of
34652 literal @samp{x}'s in place of the register data digits, to indicate
34653 that the corresponding register has not been collected, thus its value
34654 is unavailable. For example, for an architecture with 4 registers of
34655 4 bytes each, the following reply indicates to @value{GDBN} that
34656 registers 0 and 2 have not been collected, while registers 1 and 3
34657 have been collected, and both have zero value:
34661 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34668 @item G @var{XX@dots{}}
34669 @cindex @samp{G} packet
34670 Write general registers. @xref{read registers packet}, for a
34671 description of the @var{XX@dots{}} data.
34681 @item H @var{op} @var{thread-id}
34682 @cindex @samp{H} packet
34683 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34684 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34685 should be @samp{c} for step and continue operations (note that this
34686 is deprecated, supporting the @samp{vCont} command is a better
34687 option), and @samp{g} for other operations. The thread designator
34688 @var{thread-id} has the format and interpretation described in
34689 @ref{thread-id syntax}.
34700 @c 'H': How restrictive (or permissive) is the thread model. If a
34701 @c thread is selected and stopped, are other threads allowed
34702 @c to continue to execute? As I mentioned above, I think the
34703 @c semantics of each command when a thread is selected must be
34704 @c described. For example:
34706 @c 'g': If the stub supports threads and a specific thread is
34707 @c selected, returns the register block from that thread;
34708 @c otherwise returns current registers.
34710 @c 'G' If the stub supports threads and a specific thread is
34711 @c selected, sets the registers of the register block of
34712 @c that thread; otherwise sets current registers.
34714 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34715 @anchor{cycle step packet}
34716 @cindex @samp{i} packet
34717 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34718 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34719 step starting at that address.
34722 @cindex @samp{I} packet
34723 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34727 @cindex @samp{k} packet
34730 The exact effect of this packet is not specified.
34732 For a bare-metal target, it may power cycle or reset the target
34733 system. For that reason, the @samp{k} packet has no reply.
34735 For a single-process target, it may kill that process if possible.
34737 A multiple-process target may choose to kill just one process, or all
34738 that are under @value{GDBN}'s control. For more precise control, use
34739 the vKill packet (@pxref{vKill packet}).
34741 If the target system immediately closes the connection in response to
34742 @samp{k}, @value{GDBN} does not consider the lack of packet
34743 acknowledgment to be an error, and assumes the kill was successful.
34745 If connected using @kbd{target extended-remote}, and the target does
34746 not close the connection in response to a kill request, @value{GDBN}
34747 probes the target state as if a new connection was opened
34748 (@pxref{? packet}).
34750 @item m @var{addr},@var{length}
34751 @cindex @samp{m} packet
34752 Read @var{length} bytes of memory starting at address @var{addr}.
34753 Note that @var{addr} may not be aligned to any particular boundary.
34755 The stub need not use any particular size or alignment when gathering
34756 data from memory for the response; even if @var{addr} is word-aligned
34757 and @var{length} is a multiple of the word size, the stub is free to
34758 use byte accesses, or not. For this reason, this packet may not be
34759 suitable for accessing memory-mapped I/O devices.
34760 @cindex alignment of remote memory accesses
34761 @cindex size of remote memory accesses
34762 @cindex memory, alignment and size of remote accesses
34766 @item @var{XX@dots{}}
34767 Memory contents; each byte is transmitted as a two-digit hexadecimal
34768 number. The reply may contain fewer bytes than requested if the
34769 server was able to read only part of the region of memory.
34774 @item M @var{addr},@var{length}:@var{XX@dots{}}
34775 @cindex @samp{M} packet
34776 Write @var{length} bytes of memory starting at address @var{addr}.
34777 The data is given by @var{XX@dots{}}; each byte is transmitted as a two-digit
34778 hexadecimal number.
34785 for an error (this includes the case where only part of the data was
34790 @cindex @samp{p} packet
34791 Read the value of register @var{n}; @var{n} is in hex.
34792 @xref{read registers packet}, for a description of how the returned
34793 register value is encoded.
34797 @item @var{XX@dots{}}
34798 the register's value
34802 Indicating an unrecognized @var{query}.
34805 @item P @var{n@dots{}}=@var{r@dots{}}
34806 @anchor{write register packet}
34807 @cindex @samp{P} packet
34808 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34809 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34810 digits for each byte in the register (target byte order).
34820 @item q @var{name} @var{params}@dots{}
34821 @itemx Q @var{name} @var{params}@dots{}
34822 @cindex @samp{q} packet
34823 @cindex @samp{Q} packet
34824 General query (@samp{q}) and set (@samp{Q}). These packets are
34825 described fully in @ref{General Query Packets}.
34828 @cindex @samp{r} packet
34829 Reset the entire system.
34831 Don't use this packet; use the @samp{R} packet instead.
34834 @cindex @samp{R} packet
34835 Restart the program being debugged. The @var{XX}, while needed, is ignored.
34836 This packet is only available in extended mode (@pxref{extended mode}).
34838 The @samp{R} packet has no reply.
34840 @item s @r{[}@var{addr}@r{]}
34841 @cindex @samp{s} packet
34842 Single step, resuming at @var{addr}. If
34843 @var{addr} is omitted, resume at same address.
34845 This packet is deprecated for multi-threading support. @xref{vCont
34849 @xref{Stop Reply Packets}, for the reply specifications.
34851 @item S @var{sig}@r{[};@var{addr}@r{]}
34852 @anchor{step with signal packet}
34853 @cindex @samp{S} packet
34854 Step with signal. This is analogous to the @samp{C} packet, but
34855 requests a single-step, rather than a normal resumption of execution.
34857 This packet is deprecated for multi-threading support. @xref{vCont
34861 @xref{Stop Reply Packets}, for the reply specifications.
34863 @item t @var{addr}:@var{PP},@var{MM}
34864 @cindex @samp{t} packet
34865 Search backwards starting at address @var{addr} for a match with pattern
34866 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
34867 There must be at least 3 digits in @var{addr}.
34869 @item T @var{thread-id}
34870 @cindex @samp{T} packet
34871 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34876 thread is still alive
34882 Packets starting with @samp{v} are identified by a multi-letter name,
34883 up to the first @samp{;} or @samp{?} (or the end of the packet).
34885 @item vAttach;@var{pid}
34886 @cindex @samp{vAttach} packet
34887 Attach to a new process with the specified process ID @var{pid}.
34888 The process ID is a
34889 hexadecimal integer identifying the process. In all-stop mode, all
34890 threads in the attached process are stopped; in non-stop mode, it may be
34891 attached without being stopped if that is supported by the target.
34893 @c In non-stop mode, on a successful vAttach, the stub should set the
34894 @c current thread to a thread of the newly-attached process. After
34895 @c attaching, GDB queries for the attached process's thread ID with qC.
34896 @c Also note that, from a user perspective, whether or not the
34897 @c target is stopped on attach in non-stop mode depends on whether you
34898 @c use the foreground or background version of the attach command, not
34899 @c on what vAttach does; GDB does the right thing with respect to either
34900 @c stopping or restarting threads.
34902 This packet is only available in extended mode (@pxref{extended mode}).
34908 @item @r{Any stop packet}
34909 for success in all-stop mode (@pxref{Stop Reply Packets})
34911 for success in non-stop mode (@pxref{Remote Non-Stop})
34914 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34915 @cindex @samp{vCont} packet
34916 @anchor{vCont packet}
34917 Resume the inferior, specifying different actions for each thread.
34918 If an action is specified with no @var{thread-id}, then it is applied to any
34919 threads that don't have a specific action specified; if no default action is
34920 specified then other threads should remain stopped in all-stop mode and
34921 in their current state in non-stop mode.
34922 Specifying multiple
34923 default actions is an error; specifying no actions is also an error.
34924 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34926 Currently supported actions are:
34932 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34936 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34939 @item r @var{start},@var{end}
34940 Step once, and then keep stepping as long as the thread stops at
34941 addresses between @var{start} (inclusive) and @var{end} (exclusive).
34942 The remote stub reports a stop reply when either the thread goes out
34943 of the range or is stopped due to an unrelated reason, such as hitting
34944 a breakpoint. @xref{range stepping}.
34946 If the range is empty (@var{start} == @var{end}), then the action
34947 becomes equivalent to the @samp{s} action. In other words,
34948 single-step once, and report the stop (even if the stepped instruction
34949 jumps to @var{start}).
34951 (A stop reply may be sent at any point even if the PC is still within
34952 the stepping range; for example, it is valid to implement this packet
34953 in a degenerate way as a single instruction step operation.)
34957 The optional argument @var{addr} normally associated with the
34958 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34959 not supported in @samp{vCont}.
34961 The @samp{t} action is only relevant in non-stop mode
34962 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34963 A stop reply should be generated for any affected thread not already stopped.
34964 When a thread is stopped by means of a @samp{t} action,
34965 the corresponding stop reply should indicate that the thread has stopped with
34966 signal @samp{0}, regardless of whether the target uses some other signal
34967 as an implementation detail.
34969 The stub must support @samp{vCont} if it reports support for
34970 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34971 this case @samp{vCont} actions can be specified to apply to all threads
34972 in a process by using the @samp{p@var{pid}.-1} form of the
34976 @xref{Stop Reply Packets}, for the reply specifications.
34979 @cindex @samp{vCont?} packet
34980 Request a list of actions supported by the @samp{vCont} packet.
34984 @item vCont@r{[};@var{action}@dots{}@r{]}
34985 The @samp{vCont} packet is supported. Each @var{action} is a supported
34986 command in the @samp{vCont} packet.
34988 The @samp{vCont} packet is not supported.
34991 @item vFile:@var{operation}:@var{parameter}@dots{}
34992 @cindex @samp{vFile} packet
34993 Perform a file operation on the target system. For details,
34994 see @ref{Host I/O Packets}.
34996 @item vFlashErase:@var{addr},@var{length}
34997 @cindex @samp{vFlashErase} packet
34998 Direct the stub to erase @var{length} bytes of flash starting at
34999 @var{addr}. The region may enclose any number of flash blocks, but
35000 its start and end must fall on block boundaries, as indicated by the
35001 flash block size appearing in the memory map (@pxref{Memory Map
35002 Format}). @value{GDBN} groups flash memory programming operations
35003 together, and sends a @samp{vFlashDone} request after each group; the
35004 stub is allowed to delay erase operation until the @samp{vFlashDone}
35005 packet is received.
35015 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35016 @cindex @samp{vFlashWrite} packet
35017 Direct the stub to write data to flash address @var{addr}. The data
35018 is passed in binary form using the same encoding as for the @samp{X}
35019 packet (@pxref{Binary Data}). The memory ranges specified by
35020 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35021 not overlap, and must appear in order of increasing addresses
35022 (although @samp{vFlashErase} packets for higher addresses may already
35023 have been received; the ordering is guaranteed only between
35024 @samp{vFlashWrite} packets). If a packet writes to an address that was
35025 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35026 target-specific method, the results are unpredictable.
35034 for vFlashWrite addressing non-flash memory
35040 @cindex @samp{vFlashDone} packet
35041 Indicate to the stub that flash programming operation is finished.
35042 The stub is permitted to delay or batch the effects of a group of
35043 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35044 @samp{vFlashDone} packet is received. The contents of the affected
35045 regions of flash memory are unpredictable until the @samp{vFlashDone}
35046 request is completed.
35048 @item vKill;@var{pid}
35049 @cindex @samp{vKill} packet
35050 @anchor{vKill packet}
35051 Kill the process with the specified process ID @var{pid}, which is a
35052 hexadecimal integer identifying the process. This packet is used in
35053 preference to @samp{k} when multiprocess protocol extensions are
35054 supported; see @ref{multiprocess extensions}.
35064 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35065 @cindex @samp{vRun} packet
35066 Run the program @var{filename}, passing it each @var{argument} on its
35067 command line. The file and arguments are hex-encoded strings. If
35068 @var{filename} is an empty string, the stub may use a default program
35069 (e.g.@: the last program run). The program is created in the stopped
35072 @c FIXME: What about non-stop mode?
35074 This packet is only available in extended mode (@pxref{extended mode}).
35080 @item @r{Any stop packet}
35081 for success (@pxref{Stop Reply Packets})
35085 @cindex @samp{vStopped} packet
35086 @xref{Notification Packets}.
35088 @item X @var{addr},@var{length}:@var{XX@dots{}}
35090 @cindex @samp{X} packet
35091 Write data to memory, where the data is transmitted in binary.
35092 Memory is specified by its address @var{addr} and number of bytes @var{length};
35093 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35103 @item z @var{type},@var{addr},@var{kind}
35104 @itemx Z @var{type},@var{addr},@var{kind}
35105 @anchor{insert breakpoint or watchpoint packet}
35106 @cindex @samp{z} packet
35107 @cindex @samp{Z} packets
35108 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35109 watchpoint starting at address @var{address} of kind @var{kind}.
35111 Each breakpoint and watchpoint packet @var{type} is documented
35114 @emph{Implementation notes: A remote target shall return an empty string
35115 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35116 remote target shall support either both or neither of a given
35117 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35118 avoid potential problems with duplicate packets, the operations should
35119 be implemented in an idempotent way.}
35121 @item z0,@var{addr},@var{kind}
35122 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35123 @cindex @samp{z0} packet
35124 @cindex @samp{Z0} packet
35125 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35126 @var{addr} of type @var{kind}.
35128 A memory breakpoint is implemented by replacing the instruction at
35129 @var{addr} with a software breakpoint or trap instruction. The
35130 @var{kind} is target-specific and typically indicates the size of
35131 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35132 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35133 architectures have additional meanings for @var{kind};
35134 @var{cond_list} is an optional list of conditional expressions in bytecode
35135 form that should be evaluated on the target's side. These are the
35136 conditions that should be taken into consideration when deciding if
35137 the breakpoint trigger should be reported back to @var{GDBN}.
35139 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35140 for how to best report a memory breakpoint event to @value{GDBN}.
35142 The @var{cond_list} parameter is comprised of a series of expressions,
35143 concatenated without separators. Each expression has the following form:
35147 @item X @var{len},@var{expr}
35148 @var{len} is the length of the bytecode expression and @var{expr} is the
35149 actual conditional expression in bytecode form.
35153 The optional @var{cmd_list} parameter introduces commands that may be
35154 run on the target, rather than being reported back to @value{GDBN}.
35155 The parameter starts with a numeric flag @var{persist}; if the flag is
35156 nonzero, then the breakpoint may remain active and the commands
35157 continue to be run even when @value{GDBN} disconnects from the target.
35158 Following this flag is a series of expressions concatenated with no
35159 separators. Each expression has the following form:
35163 @item X @var{len},@var{expr}
35164 @var{len} is the length of the bytecode expression and @var{expr} is the
35165 actual conditional expression in bytecode form.
35169 see @ref{Architecture-Specific Protocol Details}.
35171 @emph{Implementation note: It is possible for a target to copy or move
35172 code that contains memory breakpoints (e.g., when implementing
35173 overlays). The behavior of this packet, in the presence of such a
35174 target, is not defined.}
35186 @item z1,@var{addr},@var{kind}
35187 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35188 @cindex @samp{z1} packet
35189 @cindex @samp{Z1} packet
35190 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35191 address @var{addr}.
35193 A hardware breakpoint is implemented using a mechanism that is not
35194 dependant on being able to modify the target's memory. The @var{kind}
35195 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35197 @emph{Implementation note: A hardware breakpoint is not affected by code
35210 @item z2,@var{addr},@var{kind}
35211 @itemx Z2,@var{addr},@var{kind}
35212 @cindex @samp{z2} packet
35213 @cindex @samp{Z2} packet
35214 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35215 The number of bytes to watch is specified by @var{kind}.
35227 @item z3,@var{addr},@var{kind}
35228 @itemx Z3,@var{addr},@var{kind}
35229 @cindex @samp{z3} packet
35230 @cindex @samp{Z3} packet
35231 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35232 The number of bytes to watch is specified by @var{kind}.
35244 @item z4,@var{addr},@var{kind}
35245 @itemx Z4,@var{addr},@var{kind}
35246 @cindex @samp{z4} packet
35247 @cindex @samp{Z4} packet
35248 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35249 The number of bytes to watch is specified by @var{kind}.
35263 @node Stop Reply Packets
35264 @section Stop Reply Packets
35265 @cindex stop reply packets
35267 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35268 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35269 receive any of the below as a reply. Except for @samp{?}
35270 and @samp{vStopped}, that reply is only returned
35271 when the target halts. In the below the exact meaning of @dfn{signal
35272 number} is defined by the header @file{include/gdb/signals.h} in the
35273 @value{GDBN} source code.
35275 As in the description of request packets, we include spaces in the
35276 reply templates for clarity; these are not part of the reply packet's
35277 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35283 The program received signal number @var{AA} (a two-digit hexadecimal
35284 number). This is equivalent to a @samp{T} response with no
35285 @var{n}:@var{r} pairs.
35287 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35288 @cindex @samp{T} packet reply
35289 The program received signal number @var{AA} (a two-digit hexadecimal
35290 number). This is equivalent to an @samp{S} response, except that the
35291 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35292 and other information directly in the stop reply packet, reducing
35293 round-trip latency. Single-step and breakpoint traps are reported
35294 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35298 If @var{n} is a hexadecimal number, it is a register number, and the
35299 corresponding @var{r} gives that register's value. The data @var{r} is a
35300 series of bytes in target byte order, with each byte given by a
35301 two-digit hex number.
35304 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35305 the stopped thread, as specified in @ref{thread-id syntax}.
35308 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35309 the core on which the stop event was detected.
35312 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35313 specific event that stopped the target. The currently defined stop
35314 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35315 signal. At most one stop reason should be present.
35318 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35319 and go on to the next; this allows us to extend the protocol in the
35323 The currently defined stop reasons are:
35329 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35332 @cindex shared library events, remote reply
35334 The packet indicates that the loaded libraries have changed.
35335 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35336 list of loaded libraries. The @var{r} part is ignored.
35338 @cindex replay log events, remote reply
35340 The packet indicates that the target cannot continue replaying
35341 logged execution events, because it has reached the end (or the
35342 beginning when executing backward) of the log. The value of @var{r}
35343 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35344 for more information.
35347 @anchor{swbreak stop reason}
35348 The packet indicates a memory breakpoint instruction was executed,
35349 irrespective of whether it was @value{GDBN} that planted the
35350 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35351 part must be left empty.
35353 On some architectures, such as x86, at the architecture level, when a
35354 breakpoint instruction executes the program counter points at the
35355 breakpoint address plus an offset. On such targets, the stub is
35356 responsible for adjusting the PC to point back at the breakpoint
35359 This packet should not be sent by default; older @value{GDBN} versions
35360 did not support it. @value{GDBN} requests it, by supplying an
35361 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35362 remote stub must also supply the appropriate @samp{qSupported} feature
35363 indicating support.
35365 This packet is required for correct non-stop mode operation.
35368 The packet indicates the target stopped for a hardware breakpoint.
35369 The @var{r} part must be left empty.
35371 The same remarks about @samp{qSupported} and non-stop mode above
35376 @itemx W @var{AA} ; process:@var{pid}
35377 The process exited, and @var{AA} is the exit status. This is only
35378 applicable to certain targets.
35380 The second form of the response, including the process ID of the exited
35381 process, can be used only when @value{GDBN} has reported support for
35382 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35383 The @var{pid} is formatted as a big-endian hex string.
35386 @itemx X @var{AA} ; process:@var{pid}
35387 The process terminated with signal @var{AA}.
35389 The second form of the response, including the process ID of the
35390 terminated process, can be used only when @value{GDBN} has reported
35391 support for multiprocess protocol extensions; see @ref{multiprocess
35392 extensions}. The @var{pid} is formatted as a big-endian hex string.
35394 @item O @var{XX}@dots{}
35395 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35396 written as the program's console output. This can happen at any time
35397 while the program is running and the debugger should continue to wait
35398 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35400 @item F @var{call-id},@var{parameter}@dots{}
35401 @var{call-id} is the identifier which says which host system call should
35402 be called. This is just the name of the function. Translation into the
35403 correct system call is only applicable as it's defined in @value{GDBN}.
35404 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35407 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35408 this very system call.
35410 The target replies with this packet when it expects @value{GDBN} to
35411 call a host system call on behalf of the target. @value{GDBN} replies
35412 with an appropriate @samp{F} packet and keeps up waiting for the next
35413 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35414 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35415 Protocol Extension}, for more details.
35419 @node General Query Packets
35420 @section General Query Packets
35421 @cindex remote query requests
35423 Packets starting with @samp{q} are @dfn{general query packets};
35424 packets starting with @samp{Q} are @dfn{general set packets}. General
35425 query and set packets are a semi-unified form for retrieving and
35426 sending information to and from the stub.
35428 The initial letter of a query or set packet is followed by a name
35429 indicating what sort of thing the packet applies to. For example,
35430 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35431 definitions with the stub. These packet names follow some
35436 The name must not contain commas, colons or semicolons.
35438 Most @value{GDBN} query and set packets have a leading upper case
35441 The names of custom vendor packets should use a company prefix, in
35442 lower case, followed by a period. For example, packets designed at
35443 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35444 foos) or @samp{Qacme.bar} (for setting bars).
35447 The name of a query or set packet should be separated from any
35448 parameters by a @samp{:}; the parameters themselves should be
35449 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35450 full packet name, and check for a separator or the end of the packet,
35451 in case two packet names share a common prefix. New packets should not begin
35452 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35453 packets predate these conventions, and have arguments without any terminator
35454 for the packet name; we suspect they are in widespread use in places that
35455 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35456 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35459 Like the descriptions of the other packets, each description here
35460 has a template showing the packet's overall syntax, followed by an
35461 explanation of the packet's meaning. We include spaces in some of the
35462 templates for clarity; these are not part of the packet's syntax. No
35463 @value{GDBN} packet uses spaces to separate its components.
35465 Here are the currently defined query and set packets:
35471 Turn on or off the agent as a helper to perform some debugging operations
35472 delegated from @value{GDBN} (@pxref{Control Agent}).
35474 @item QAllow:@var{op}:@var{val}@dots{}
35475 @cindex @samp{QAllow} packet
35476 Specify which operations @value{GDBN} expects to request of the
35477 target, as a semicolon-separated list of operation name and value
35478 pairs. Possible values for @var{op} include @samp{WriteReg},
35479 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35480 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35481 indicating that @value{GDBN} will not request the operation, or 1,
35482 indicating that it may. (The target can then use this to set up its
35483 own internals optimally, for instance if the debugger never expects to
35484 insert breakpoints, it may not need to install its own trap handler.)
35487 @cindex current thread, remote request
35488 @cindex @samp{qC} packet
35489 Return the current thread ID.
35493 @item QC @var{thread-id}
35494 Where @var{thread-id} is a thread ID as documented in
35495 @ref{thread-id syntax}.
35496 @item @r{(anything else)}
35497 Any other reply implies the old thread ID.
35500 @item qCRC:@var{addr},@var{length}
35501 @cindex CRC of memory block, remote request
35502 @cindex @samp{qCRC} packet
35503 @anchor{qCRC packet}
35504 Compute the CRC checksum of a block of memory using CRC-32 defined in
35505 IEEE 802.3. The CRC is computed byte at a time, taking the most
35506 significant bit of each byte first. The initial pattern code
35507 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35509 @emph{Note:} This is the same CRC used in validating separate debug
35510 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35511 Files}). However the algorithm is slightly different. When validating
35512 separate debug files, the CRC is computed taking the @emph{least}
35513 significant bit of each byte first, and the final result is inverted to
35514 detect trailing zeros.
35519 An error (such as memory fault)
35520 @item C @var{crc32}
35521 The specified memory region's checksum is @var{crc32}.
35524 @item QDisableRandomization:@var{value}
35525 @cindex disable address space randomization, remote request
35526 @cindex @samp{QDisableRandomization} packet
35527 Some target operating systems will randomize the virtual address space
35528 of the inferior process as a security feature, but provide a feature
35529 to disable such randomization, e.g.@: to allow for a more deterministic
35530 debugging experience. On such systems, this packet with a @var{value}
35531 of 1 directs the target to disable address space randomization for
35532 processes subsequently started via @samp{vRun} packets, while a packet
35533 with a @var{value} of 0 tells the target to enable address space
35536 This packet is only available in extended mode (@pxref{extended mode}).
35541 The request succeeded.
35544 An error occurred. The error number @var{nn} is given as hex digits.
35547 An empty reply indicates that @samp{QDisableRandomization} is not supported
35551 This packet is not probed by default; the remote stub must request it,
35552 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35553 This should only be done on targets that actually support disabling
35554 address space randomization.
35557 @itemx qsThreadInfo
35558 @cindex list active threads, remote request
35559 @cindex @samp{qfThreadInfo} packet
35560 @cindex @samp{qsThreadInfo} packet
35561 Obtain a list of all active thread IDs from the target (OS). Since there
35562 may be too many active threads to fit into one reply packet, this query
35563 works iteratively: it may require more than one query/reply sequence to
35564 obtain the entire list of threads. The first query of the sequence will
35565 be the @samp{qfThreadInfo} query; subsequent queries in the
35566 sequence will be the @samp{qsThreadInfo} query.
35568 NOTE: This packet replaces the @samp{qL} query (see below).
35572 @item m @var{thread-id}
35574 @item m @var{thread-id},@var{thread-id}@dots{}
35575 a comma-separated list of thread IDs
35577 (lower case letter @samp{L}) denotes end of list.
35580 In response to each query, the target will reply with a list of one or
35581 more thread IDs, separated by commas.
35582 @value{GDBN} will respond to each reply with a request for more thread
35583 ids (using the @samp{qs} form of the query), until the target responds
35584 with @samp{l} (lower-case ell, for @dfn{last}).
35585 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
35588 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
35589 initial connection with the remote target, and the very first thread ID
35590 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
35591 message. Therefore, the stub should ensure that the first thread ID in
35592 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
35594 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
35595 @cindex get thread-local storage address, remote request
35596 @cindex @samp{qGetTLSAddr} packet
35597 Fetch the address associated with thread local storage specified
35598 by @var{thread-id}, @var{offset}, and @var{lm}.
35600 @var{thread-id} is the thread ID associated with the
35601 thread for which to fetch the TLS address. @xref{thread-id syntax}.
35603 @var{offset} is the (big endian, hex encoded) offset associated with the
35604 thread local variable. (This offset is obtained from the debug
35605 information associated with the variable.)
35607 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
35608 load module associated with the thread local storage. For example,
35609 a @sc{gnu}/Linux system will pass the link map address of the shared
35610 object associated with the thread local storage under consideration.
35611 Other operating environments may choose to represent the load module
35612 differently, so the precise meaning of this parameter will vary.
35616 @item @var{XX}@dots{}
35617 Hex encoded (big endian) bytes representing the address of the thread
35618 local storage requested.
35621 An error occurred. The error number @var{nn} is given as hex digits.
35624 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
35627 @item qGetTIBAddr:@var{thread-id}
35628 @cindex get thread information block address
35629 @cindex @samp{qGetTIBAddr} packet
35630 Fetch address of the Windows OS specific Thread Information Block.
35632 @var{thread-id} is the thread ID associated with the thread.
35636 @item @var{XX}@dots{}
35637 Hex encoded (big endian) bytes representing the linear address of the
35638 thread information block.
35641 An error occured. This means that either the thread was not found, or the
35642 address could not be retrieved.
35645 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
35648 @item qL @var{startflag} @var{threadcount} @var{nextthread}
35649 Obtain thread information from RTOS. Where: @var{startflag} (one hex
35650 digit) is one to indicate the first query and zero to indicate a
35651 subsequent query; @var{threadcount} (two hex digits) is the maximum
35652 number of threads the response packet can contain; and @var{nextthread}
35653 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
35654 returned in the response as @var{argthread}.
35656 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
35660 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
35661 Where: @var{count} (two hex digits) is the number of threads being
35662 returned; @var{done} (one hex digit) is zero to indicate more threads
35663 and one indicates no further threads; @var{argthreadid} (eight hex
35664 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
35665 is a sequence of thread IDs, @var{threadid} (eight hex
35666 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
35670 @cindex section offsets, remote request
35671 @cindex @samp{qOffsets} packet
35672 Get section offsets that the target used when relocating the downloaded
35677 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
35678 Relocate the @code{Text} section by @var{xxx} from its original address.
35679 Relocate the @code{Data} section by @var{yyy} from its original address.
35680 If the object file format provides segment information (e.g.@: @sc{elf}
35681 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
35682 segments by the supplied offsets.
35684 @emph{Note: while a @code{Bss} offset may be included in the response,
35685 @value{GDBN} ignores this and instead applies the @code{Data} offset
35686 to the @code{Bss} section.}
35688 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
35689 Relocate the first segment of the object file, which conventionally
35690 contains program code, to a starting address of @var{xxx}. If
35691 @samp{DataSeg} is specified, relocate the second segment, which
35692 conventionally contains modifiable data, to a starting address of
35693 @var{yyy}. @value{GDBN} will report an error if the object file
35694 does not contain segment information, or does not contain at least
35695 as many segments as mentioned in the reply. Extra segments are
35696 kept at fixed offsets relative to the last relocated segment.
35699 @item qP @var{mode} @var{thread-id}
35700 @cindex thread information, remote request
35701 @cindex @samp{qP} packet
35702 Returns information on @var{thread-id}. Where: @var{mode} is a hex
35703 encoded 32 bit mode; @var{thread-id} is a thread ID
35704 (@pxref{thread-id syntax}).
35706 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
35709 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
35713 @cindex non-stop mode, remote request
35714 @cindex @samp{QNonStop} packet
35716 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
35717 @xref{Remote Non-Stop}, for more information.
35722 The request succeeded.
35725 An error occurred. The error number @var{nn} is given as hex digits.
35728 An empty reply indicates that @samp{QNonStop} is not supported by
35732 This packet is not probed by default; the remote stub must request it,
35733 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35734 Use of this packet is controlled by the @code{set non-stop} command;
35735 @pxref{Non-Stop Mode}.
35737 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35738 @cindex pass signals to inferior, remote request
35739 @cindex @samp{QPassSignals} packet
35740 @anchor{QPassSignals}
35741 Each listed @var{signal} should be passed directly to the inferior process.
35742 Signals are numbered identically to continue packets and stop replies
35743 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35744 strictly greater than the previous item. These signals do not need to stop
35745 the inferior, or be reported to @value{GDBN}. All other signals should be
35746 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
35747 combine; any earlier @samp{QPassSignals} list is completely replaced by the
35748 new list. This packet improves performance when using @samp{handle
35749 @var{signal} nostop noprint pass}.
35754 The request succeeded.
35757 An error occurred. The error number @var{nn} is given as hex digits.
35760 An empty reply indicates that @samp{QPassSignals} is not supported by
35764 Use of this packet is controlled by the @code{set remote pass-signals}
35765 command (@pxref{Remote Configuration, set remote pass-signals}).
35766 This packet is not probed by default; the remote stub must request it,
35767 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35769 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
35770 @cindex signals the inferior may see, remote request
35771 @cindex @samp{QProgramSignals} packet
35772 @anchor{QProgramSignals}
35773 Each listed @var{signal} may be delivered to the inferior process.
35774 Others should be silently discarded.
35776 In some cases, the remote stub may need to decide whether to deliver a
35777 signal to the program or not without @value{GDBN} involvement. One
35778 example of that is while detaching --- the program's threads may have
35779 stopped for signals that haven't yet had a chance of being reported to
35780 @value{GDBN}, and so the remote stub can use the signal list specified
35781 by this packet to know whether to deliver or ignore those pending
35784 This does not influence whether to deliver a signal as requested by a
35785 resumption packet (@pxref{vCont packet}).
35787 Signals are numbered identically to continue packets and stop replies
35788 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35789 strictly greater than the previous item. Multiple
35790 @samp{QProgramSignals} packets do not combine; any earlier
35791 @samp{QProgramSignals} list is completely replaced by the new list.
35796 The request succeeded.
35799 An error occurred. The error number @var{nn} is given as hex digits.
35802 An empty reply indicates that @samp{QProgramSignals} is not supported
35806 Use of this packet is controlled by the @code{set remote program-signals}
35807 command (@pxref{Remote Configuration, set remote program-signals}).
35808 This packet is not probed by default; the remote stub must request it,
35809 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35811 @item qRcmd,@var{command}
35812 @cindex execute remote command, remote request
35813 @cindex @samp{qRcmd} packet
35814 @var{command} (hex encoded) is passed to the local interpreter for
35815 execution. Invalid commands should be reported using the output
35816 string. Before the final result packet, the target may also respond
35817 with a number of intermediate @samp{O@var{output}} console output
35818 packets. @emph{Implementors should note that providing access to a
35819 stubs's interpreter may have security implications}.
35824 A command response with no output.
35826 A command response with the hex encoded output string @var{OUTPUT}.
35828 Indicate a badly formed request.
35830 An empty reply indicates that @samp{qRcmd} is not recognized.
35833 (Note that the @code{qRcmd} packet's name is separated from the
35834 command by a @samp{,}, not a @samp{:}, contrary to the naming
35835 conventions above. Please don't use this packet as a model for new
35838 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35839 @cindex searching memory, in remote debugging
35841 @cindex @samp{qSearch:memory} packet
35843 @cindex @samp{qSearch memory} packet
35844 @anchor{qSearch memory}
35845 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35846 Both @var{address} and @var{length} are encoded in hex;
35847 @var{search-pattern} is a sequence of bytes, also hex encoded.
35852 The pattern was not found.
35854 The pattern was found at @var{address}.
35856 A badly formed request or an error was encountered while searching memory.
35858 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35861 @item QStartNoAckMode
35862 @cindex @samp{QStartNoAckMode} packet
35863 @anchor{QStartNoAckMode}
35864 Request that the remote stub disable the normal @samp{+}/@samp{-}
35865 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35870 The stub has switched to no-acknowledgment mode.
35871 @value{GDBN} acknowledges this reponse,
35872 but neither the stub nor @value{GDBN} shall send or expect further
35873 @samp{+}/@samp{-} acknowledgments in the current connection.
35875 An empty reply indicates that the stub does not support no-acknowledgment mode.
35878 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35879 @cindex supported packets, remote query
35880 @cindex features of the remote protocol
35881 @cindex @samp{qSupported} packet
35882 @anchor{qSupported}
35883 Tell the remote stub about features supported by @value{GDBN}, and
35884 query the stub for features it supports. This packet allows
35885 @value{GDBN} and the remote stub to take advantage of each others'
35886 features. @samp{qSupported} also consolidates multiple feature probes
35887 at startup, to improve @value{GDBN} performance---a single larger
35888 packet performs better than multiple smaller probe packets on
35889 high-latency links. Some features may enable behavior which must not
35890 be on by default, e.g.@: because it would confuse older clients or
35891 stubs. Other features may describe packets which could be
35892 automatically probed for, but are not. These features must be
35893 reported before @value{GDBN} will use them. This ``default
35894 unsupported'' behavior is not appropriate for all packets, but it
35895 helps to keep the initial connection time under control with new
35896 versions of @value{GDBN} which support increasing numbers of packets.
35900 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35901 The stub supports or does not support each returned @var{stubfeature},
35902 depending on the form of each @var{stubfeature} (see below for the
35905 An empty reply indicates that @samp{qSupported} is not recognized,
35906 or that no features needed to be reported to @value{GDBN}.
35909 The allowed forms for each feature (either a @var{gdbfeature} in the
35910 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35914 @item @var{name}=@var{value}
35915 The remote protocol feature @var{name} is supported, and associated
35916 with the specified @var{value}. The format of @var{value} depends
35917 on the feature, but it must not include a semicolon.
35919 The remote protocol feature @var{name} is supported, and does not
35920 need an associated value.
35922 The remote protocol feature @var{name} is not supported.
35924 The remote protocol feature @var{name} may be supported, and
35925 @value{GDBN} should auto-detect support in some other way when it is
35926 needed. This form will not be used for @var{gdbfeature} notifications,
35927 but may be used for @var{stubfeature} responses.
35930 Whenever the stub receives a @samp{qSupported} request, the
35931 supplied set of @value{GDBN} features should override any previous
35932 request. This allows @value{GDBN} to put the stub in a known
35933 state, even if the stub had previously been communicating with
35934 a different version of @value{GDBN}.
35936 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35941 This feature indicates whether @value{GDBN} supports multiprocess
35942 extensions to the remote protocol. @value{GDBN} does not use such
35943 extensions unless the stub also reports that it supports them by
35944 including @samp{multiprocess+} in its @samp{qSupported} reply.
35945 @xref{multiprocess extensions}, for details.
35948 This feature indicates that @value{GDBN} supports the XML target
35949 description. If the stub sees @samp{xmlRegisters=} with target
35950 specific strings separated by a comma, it will report register
35954 This feature indicates whether @value{GDBN} supports the
35955 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35956 instruction reply packet}).
35959 This feature indicates whether @value{GDBN} supports the swbreak stop
35960 reason in stop replies. @xref{swbreak stop reason}, for details.
35963 This feature indicates whether @value{GDBN} supports the hwbreak stop
35964 reason in stop replies. @xref{swbreak stop reason}, for details.
35967 Stubs should ignore any unknown values for
35968 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35969 packet supports receiving packets of unlimited length (earlier
35970 versions of @value{GDBN} may reject overly long responses). Additional values
35971 for @var{gdbfeature} may be defined in the future to let the stub take
35972 advantage of new features in @value{GDBN}, e.g.@: incompatible
35973 improvements in the remote protocol---the @samp{multiprocess} feature is
35974 an example of such a feature. The stub's reply should be independent
35975 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35976 describes all the features it supports, and then the stub replies with
35977 all the features it supports.
35979 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35980 responses, as long as each response uses one of the standard forms.
35982 Some features are flags. A stub which supports a flag feature
35983 should respond with a @samp{+} form response. Other features
35984 require values, and the stub should respond with an @samp{=}
35987 Each feature has a default value, which @value{GDBN} will use if
35988 @samp{qSupported} is not available or if the feature is not mentioned
35989 in the @samp{qSupported} response. The default values are fixed; a
35990 stub is free to omit any feature responses that match the defaults.
35992 Not all features can be probed, but for those which can, the probing
35993 mechanism is useful: in some cases, a stub's internal
35994 architecture may not allow the protocol layer to know some information
35995 about the underlying target in advance. This is especially common in
35996 stubs which may be configured for multiple targets.
35998 These are the currently defined stub features and their properties:
36000 @multitable @columnfractions 0.35 0.2 0.12 0.2
36001 @c NOTE: The first row should be @headitem, but we do not yet require
36002 @c a new enough version of Texinfo (4.7) to use @headitem.
36004 @tab Value Required
36008 @item @samp{PacketSize}
36013 @item @samp{qXfer:auxv:read}
36018 @item @samp{qXfer:btrace:read}
36023 @item @samp{qXfer:btrace-conf:read}
36028 @item @samp{qXfer:exec-file:read}
36033 @item @samp{qXfer:features:read}
36038 @item @samp{qXfer:libraries:read}
36043 @item @samp{qXfer:libraries-svr4:read}
36048 @item @samp{augmented-libraries-svr4-read}
36053 @item @samp{qXfer:memory-map:read}
36058 @item @samp{qXfer:sdata:read}
36063 @item @samp{qXfer:spu:read}
36068 @item @samp{qXfer:spu:write}
36073 @item @samp{qXfer:siginfo:read}
36078 @item @samp{qXfer:siginfo:write}
36083 @item @samp{qXfer:threads:read}
36088 @item @samp{qXfer:traceframe-info:read}
36093 @item @samp{qXfer:uib:read}
36098 @item @samp{qXfer:fdpic:read}
36103 @item @samp{Qbtrace:off}
36108 @item @samp{Qbtrace:bts}
36113 @item @samp{Qbtrace-conf:bts:size}
36118 @item @samp{QNonStop}
36123 @item @samp{QPassSignals}
36128 @item @samp{QStartNoAckMode}
36133 @item @samp{multiprocess}
36138 @item @samp{ConditionalBreakpoints}
36143 @item @samp{ConditionalTracepoints}
36148 @item @samp{ReverseContinue}
36153 @item @samp{ReverseStep}
36158 @item @samp{TracepointSource}
36163 @item @samp{QAgent}
36168 @item @samp{QAllow}
36173 @item @samp{QDisableRandomization}
36178 @item @samp{EnableDisableTracepoints}
36183 @item @samp{QTBuffer:size}
36188 @item @samp{tracenz}
36193 @item @samp{BreakpointCommands}
36198 @item @samp{swbreak}
36203 @item @samp{hwbreak}
36210 These are the currently defined stub features, in more detail:
36213 @cindex packet size, remote protocol
36214 @item PacketSize=@var{bytes}
36215 The remote stub can accept packets up to at least @var{bytes} in
36216 length. @value{GDBN} will send packets up to this size for bulk
36217 transfers, and will never send larger packets. This is a limit on the
36218 data characters in the packet, including the frame and checksum.
36219 There is no trailing NUL byte in a remote protocol packet; if the stub
36220 stores packets in a NUL-terminated format, it should allow an extra
36221 byte in its buffer for the NUL. If this stub feature is not supported,
36222 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36224 @item qXfer:auxv:read
36225 The remote stub understands the @samp{qXfer:auxv:read} packet
36226 (@pxref{qXfer auxiliary vector read}).
36228 @item qXfer:btrace:read
36229 The remote stub understands the @samp{qXfer:btrace:read}
36230 packet (@pxref{qXfer btrace read}).
36232 @item qXfer:btrace-conf:read
36233 The remote stub understands the @samp{qXfer:btrace-conf:read}
36234 packet (@pxref{qXfer btrace-conf read}).
36236 @item qXfer:exec-file:read
36237 The remote stub understands the @samp{qXfer:exec-file:read} packet
36238 (@pxref{qXfer executable filename read}).
36240 @item qXfer:features:read
36241 The remote stub understands the @samp{qXfer:features:read} packet
36242 (@pxref{qXfer target description read}).
36244 @item qXfer:libraries:read
36245 The remote stub understands the @samp{qXfer:libraries:read} packet
36246 (@pxref{qXfer library list read}).
36248 @item qXfer:libraries-svr4:read
36249 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36250 (@pxref{qXfer svr4 library list read}).
36252 @item augmented-libraries-svr4-read
36253 The remote stub understands the augmented form of the
36254 @samp{qXfer:libraries-svr4:read} packet
36255 (@pxref{qXfer svr4 library list read}).
36257 @item qXfer:memory-map:read
36258 The remote stub understands the @samp{qXfer:memory-map:read} packet
36259 (@pxref{qXfer memory map read}).
36261 @item qXfer:sdata:read
36262 The remote stub understands the @samp{qXfer:sdata:read} packet
36263 (@pxref{qXfer sdata read}).
36265 @item qXfer:spu:read
36266 The remote stub understands the @samp{qXfer:spu:read} packet
36267 (@pxref{qXfer spu read}).
36269 @item qXfer:spu:write
36270 The remote stub understands the @samp{qXfer:spu:write} packet
36271 (@pxref{qXfer spu write}).
36273 @item qXfer:siginfo:read
36274 The remote stub understands the @samp{qXfer:siginfo:read} packet
36275 (@pxref{qXfer siginfo read}).
36277 @item qXfer:siginfo:write
36278 The remote stub understands the @samp{qXfer:siginfo:write} packet
36279 (@pxref{qXfer siginfo write}).
36281 @item qXfer:threads:read
36282 The remote stub understands the @samp{qXfer:threads:read} packet
36283 (@pxref{qXfer threads read}).
36285 @item qXfer:traceframe-info:read
36286 The remote stub understands the @samp{qXfer:traceframe-info:read}
36287 packet (@pxref{qXfer traceframe info read}).
36289 @item qXfer:uib:read
36290 The remote stub understands the @samp{qXfer:uib:read}
36291 packet (@pxref{qXfer unwind info block}).
36293 @item qXfer:fdpic:read
36294 The remote stub understands the @samp{qXfer:fdpic:read}
36295 packet (@pxref{qXfer fdpic loadmap read}).
36298 The remote stub understands the @samp{QNonStop} packet
36299 (@pxref{QNonStop}).
36302 The remote stub understands the @samp{QPassSignals} packet
36303 (@pxref{QPassSignals}).
36305 @item QStartNoAckMode
36306 The remote stub understands the @samp{QStartNoAckMode} packet and
36307 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36310 @anchor{multiprocess extensions}
36311 @cindex multiprocess extensions, in remote protocol
36312 The remote stub understands the multiprocess extensions to the remote
36313 protocol syntax. The multiprocess extensions affect the syntax of
36314 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36315 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36316 replies. Note that reporting this feature indicates support for the
36317 syntactic extensions only, not that the stub necessarily supports
36318 debugging of more than one process at a time. The stub must not use
36319 multiprocess extensions in packet replies unless @value{GDBN} has also
36320 indicated it supports them in its @samp{qSupported} request.
36322 @item qXfer:osdata:read
36323 The remote stub understands the @samp{qXfer:osdata:read} packet
36324 ((@pxref{qXfer osdata read}).
36326 @item ConditionalBreakpoints
36327 The target accepts and implements evaluation of conditional expressions
36328 defined for breakpoints. The target will only report breakpoint triggers
36329 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36331 @item ConditionalTracepoints
36332 The remote stub accepts and implements conditional expressions defined
36333 for tracepoints (@pxref{Tracepoint Conditions}).
36335 @item ReverseContinue
36336 The remote stub accepts and implements the reverse continue packet
36340 The remote stub accepts and implements the reverse step packet
36343 @item TracepointSource
36344 The remote stub understands the @samp{QTDPsrc} packet that supplies
36345 the source form of tracepoint definitions.
36348 The remote stub understands the @samp{QAgent} packet.
36351 The remote stub understands the @samp{QAllow} packet.
36353 @item QDisableRandomization
36354 The remote stub understands the @samp{QDisableRandomization} packet.
36356 @item StaticTracepoint
36357 @cindex static tracepoints, in remote protocol
36358 The remote stub supports static tracepoints.
36360 @item InstallInTrace
36361 @anchor{install tracepoint in tracing}
36362 The remote stub supports installing tracepoint in tracing.
36364 @item EnableDisableTracepoints
36365 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36366 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36367 to be enabled and disabled while a trace experiment is running.
36369 @item QTBuffer:size
36370 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
36371 packet that allows to change the size of the trace buffer.
36374 @cindex string tracing, in remote protocol
36375 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36376 See @ref{Bytecode Descriptions} for details about the bytecode.
36378 @item BreakpointCommands
36379 @cindex breakpoint commands, in remote protocol
36380 The remote stub supports running a breakpoint's command list itself,
36381 rather than reporting the hit to @value{GDBN}.
36384 The remote stub understands the @samp{Qbtrace:off} packet.
36387 The remote stub understands the @samp{Qbtrace:bts} packet.
36389 @item Qbtrace-conf:bts:size
36390 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
36393 The remote stub reports the @samp{swbreak} stop reason for memory
36397 The remote stub reports the @samp{hwbreak} stop reason for hardware
36403 @cindex symbol lookup, remote request
36404 @cindex @samp{qSymbol} packet
36405 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36406 requests. Accept requests from the target for the values of symbols.
36411 The target does not need to look up any (more) symbols.
36412 @item qSymbol:@var{sym_name}
36413 The target requests the value of symbol @var{sym_name} (hex encoded).
36414 @value{GDBN} may provide the value by using the
36415 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
36419 @item qSymbol:@var{sym_value}:@var{sym_name}
36420 Set the value of @var{sym_name} to @var{sym_value}.
36422 @var{sym_name} (hex encoded) is the name of a symbol whose value the
36423 target has previously requested.
36425 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
36426 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
36432 The target does not need to look up any (more) symbols.
36433 @item qSymbol:@var{sym_name}
36434 The target requests the value of a new symbol @var{sym_name} (hex
36435 encoded). @value{GDBN} will continue to supply the values of symbols
36436 (if available), until the target ceases to request them.
36441 @itemx QTDisconnected
36448 @itemx qTMinFTPILen
36450 @xref{Tracepoint Packets}.
36452 @item qThreadExtraInfo,@var{thread-id}
36453 @cindex thread attributes info, remote request
36454 @cindex @samp{qThreadExtraInfo} packet
36455 Obtain from the target OS a printable string description of thread
36456 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
36457 for the forms of @var{thread-id}. This
36458 string may contain anything that the target OS thinks is interesting
36459 for @value{GDBN} to tell the user about the thread. The string is
36460 displayed in @value{GDBN}'s @code{info threads} display. Some
36461 examples of possible thread extra info strings are @samp{Runnable}, or
36462 @samp{Blocked on Mutex}.
36466 @item @var{XX}@dots{}
36467 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
36468 comprising the printable string containing the extra information about
36469 the thread's attributes.
36472 (Note that the @code{qThreadExtraInfo} packet's name is separated from
36473 the command by a @samp{,}, not a @samp{:}, contrary to the naming
36474 conventions above. Please don't use this packet as a model for new
36493 @xref{Tracepoint Packets}.
36495 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
36496 @cindex read special object, remote request
36497 @cindex @samp{qXfer} packet
36498 @anchor{qXfer read}
36499 Read uninterpreted bytes from the target's special data area
36500 identified by the keyword @var{object}. Request @var{length} bytes
36501 starting at @var{offset} bytes into the data. The content and
36502 encoding of @var{annex} is specific to @var{object}; it can supply
36503 additional details about what data to access.
36505 Here are the specific requests of this form defined so far. All
36506 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
36507 formats, listed below.
36510 @item qXfer:auxv:read::@var{offset},@var{length}
36511 @anchor{qXfer auxiliary vector read}
36512 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
36513 auxiliary vector}. Note @var{annex} must be empty.
36515 This packet is not probed by default; the remote stub must request it,
36516 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36518 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
36519 @anchor{qXfer btrace read}
36521 Return a description of the current branch trace.
36522 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
36523 packet may have one of the following values:
36527 Returns all available branch trace.
36530 Returns all available branch trace if the branch trace changed since
36531 the last read request.
36534 Returns the new branch trace since the last read request. Adds a new
36535 block to the end of the trace that begins at zero and ends at the source
36536 location of the first branch in the trace buffer. This extra block is
36537 used to stitch traces together.
36539 If the trace buffer overflowed, returns an error indicating the overflow.
36542 This packet is not probed by default; the remote stub must request it
36543 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36545 @item qXfer:btrace-conf:read::@var{offset},@var{length}
36546 @anchor{qXfer btrace-conf read}
36548 Return a description of the current branch trace configuration.
36549 @xref{Branch Trace Configuration Format}.
36551 This packet is not probed by default; the remote stub must request it
36552 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36554 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
36555 @anchor{qXfer executable filename read}
36556 Return the full absolute name of the file that was executed to create
36557 a process running on the remote system. The annex specifies the
36558 numeric process ID of the process to query, encoded as a hexadecimal
36561 This packet is not probed by default; the remote stub must request it,
36562 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36564 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
36565 @anchor{qXfer target description read}
36566 Access the @dfn{target description}. @xref{Target Descriptions}. The
36567 annex specifies which XML document to access. The main description is
36568 always loaded from the @samp{target.xml} annex.
36570 This packet is not probed by default; the remote stub must request it,
36571 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36573 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
36574 @anchor{qXfer library list read}
36575 Access the target's list of loaded libraries. @xref{Library List Format}.
36576 The annex part of the generic @samp{qXfer} packet must be empty
36577 (@pxref{qXfer read}).
36579 Targets which maintain a list of libraries in the program's memory do
36580 not need to implement this packet; it is designed for platforms where
36581 the operating system manages the list of loaded libraries.
36583 This packet is not probed by default; the remote stub must request it,
36584 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36586 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
36587 @anchor{qXfer svr4 library list read}
36588 Access the target's list of loaded libraries when the target is an SVR4
36589 platform. @xref{Library List Format for SVR4 Targets}. The annex part
36590 of the generic @samp{qXfer} packet must be empty unless the remote
36591 stub indicated it supports the augmented form of this packet
36592 by supplying an appropriate @samp{qSupported} response
36593 (@pxref{qXfer read}, @ref{qSupported}).
36595 This packet is optional for better performance on SVR4 targets.
36596 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
36598 This packet is not probed by default; the remote stub must request it,
36599 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36601 If the remote stub indicates it supports the augmented form of this
36602 packet then the annex part of the generic @samp{qXfer} packet may
36603 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
36604 arguments. The currently supported arguments are:
36607 @item start=@var{address}
36608 A hexadecimal number specifying the address of the @samp{struct
36609 link_map} to start reading the library list from. If unset or zero
36610 then the first @samp{struct link_map} in the library list will be
36611 chosen as the starting point.
36613 @item prev=@var{address}
36614 A hexadecimal number specifying the address of the @samp{struct
36615 link_map} immediately preceding the @samp{struct link_map}
36616 specified by the @samp{start} argument. If unset or zero then
36617 the remote stub will expect that no @samp{struct link_map}
36618 exists prior to the starting point.
36622 Arguments that are not understood by the remote stub will be silently
36625 @item qXfer:memory-map:read::@var{offset},@var{length}
36626 @anchor{qXfer memory map read}
36627 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
36628 annex part of the generic @samp{qXfer} packet must be empty
36629 (@pxref{qXfer read}).
36631 This packet is not probed by default; the remote stub must request it,
36632 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36634 @item qXfer:sdata:read::@var{offset},@var{length}
36635 @anchor{qXfer sdata read}
36637 Read contents of the extra collected static tracepoint marker
36638 information. The annex part of the generic @samp{qXfer} packet must
36639 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
36642 This packet is not probed by default; the remote stub must request it,
36643 by supplying an appropriate @samp{qSupported} response
36644 (@pxref{qSupported}).
36646 @item qXfer:siginfo:read::@var{offset},@var{length}
36647 @anchor{qXfer siginfo read}
36648 Read contents of the extra signal information on the target
36649 system. The annex part of the generic @samp{qXfer} packet must be
36650 empty (@pxref{qXfer read}).
36652 This packet is not probed by default; the remote stub must request it,
36653 by supplying an appropriate @samp{qSupported} response
36654 (@pxref{qSupported}).
36656 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
36657 @anchor{qXfer spu read}
36658 Read contents of an @code{spufs} file on the target system. The
36659 annex specifies which file to read; it must be of the form
36660 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36661 in the target process, and @var{name} identifes the @code{spufs} file
36662 in that context to be accessed.
36664 This packet is not probed by default; the remote stub must request it,
36665 by supplying an appropriate @samp{qSupported} response
36666 (@pxref{qSupported}).
36668 @item qXfer:threads:read::@var{offset},@var{length}
36669 @anchor{qXfer threads read}
36670 Access the list of threads on target. @xref{Thread List Format}. The
36671 annex part of the generic @samp{qXfer} packet must be empty
36672 (@pxref{qXfer read}).
36674 This packet is not probed by default; the remote stub must request it,
36675 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36677 @item qXfer:traceframe-info:read::@var{offset},@var{length}
36678 @anchor{qXfer traceframe info read}
36680 Return a description of the current traceframe's contents.
36681 @xref{Traceframe Info Format}. The annex part of the generic
36682 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
36684 This packet is not probed by default; the remote stub must request it,
36685 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36687 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
36688 @anchor{qXfer unwind info block}
36690 Return the unwind information block for @var{pc}. This packet is used
36691 on OpenVMS/ia64 to ask the kernel unwind information.
36693 This packet is not probed by default.
36695 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
36696 @anchor{qXfer fdpic loadmap read}
36697 Read contents of @code{loadmap}s on the target system. The
36698 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
36699 executable @code{loadmap} or interpreter @code{loadmap} to read.
36701 This packet is not probed by default; the remote stub must request it,
36702 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36704 @item qXfer:osdata:read::@var{offset},@var{length}
36705 @anchor{qXfer osdata read}
36706 Access the target's @dfn{operating system information}.
36707 @xref{Operating System Information}.
36714 Data @var{data} (@pxref{Binary Data}) has been read from the
36715 target. There may be more data at a higher address (although
36716 it is permitted to return @samp{m} even for the last valid
36717 block of data, as long as at least one byte of data was read).
36718 It is possible for @var{data} to have fewer bytes than the @var{length} in the
36722 Data @var{data} (@pxref{Binary Data}) has been read from the target.
36723 There is no more data to be read. It is possible for @var{data} to
36724 have fewer bytes than the @var{length} in the request.
36727 The @var{offset} in the request is at the end of the data.
36728 There is no more data to be read.
36731 The request was malformed, or @var{annex} was invalid.
36734 The offset was invalid, or there was an error encountered reading the data.
36735 The @var{nn} part is a hex-encoded @code{errno} value.
36738 An empty reply indicates the @var{object} string was not recognized by
36739 the stub, or that the object does not support reading.
36742 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
36743 @cindex write data into object, remote request
36744 @anchor{qXfer write}
36745 Write uninterpreted bytes into the target's special data area
36746 identified by the keyword @var{object}, starting at @var{offset} bytes
36747 into the data. The binary-encoded data (@pxref{Binary Data}) to be
36748 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
36749 is specific to @var{object}; it can supply additional details about what data
36752 Here are the specific requests of this form defined so far. All
36753 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
36754 formats, listed below.
36757 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
36758 @anchor{qXfer siginfo write}
36759 Write @var{data} to the extra signal information on the target system.
36760 The annex part of the generic @samp{qXfer} packet must be
36761 empty (@pxref{qXfer write}).
36763 This packet is not probed by default; the remote stub must request it,
36764 by supplying an appropriate @samp{qSupported} response
36765 (@pxref{qSupported}).
36767 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
36768 @anchor{qXfer spu write}
36769 Write @var{data} to an @code{spufs} file on the target system. The
36770 annex specifies which file to write; it must be of the form
36771 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
36772 in the target process, and @var{name} identifes the @code{spufs} file
36773 in that context to be accessed.
36775 This packet is not probed by default; the remote stub must request it,
36776 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36782 @var{nn} (hex encoded) is the number of bytes written.
36783 This may be fewer bytes than supplied in the request.
36786 The request was malformed, or @var{annex} was invalid.
36789 The offset was invalid, or there was an error encountered writing the data.
36790 The @var{nn} part is a hex-encoded @code{errno} value.
36793 An empty reply indicates the @var{object} string was not
36794 recognized by the stub, or that the object does not support writing.
36797 @item qXfer:@var{object}:@var{operation}:@dots{}
36798 Requests of this form may be added in the future. When a stub does
36799 not recognize the @var{object} keyword, or its support for
36800 @var{object} does not recognize the @var{operation} keyword, the stub
36801 must respond with an empty packet.
36803 @item qAttached:@var{pid}
36804 @cindex query attached, remote request
36805 @cindex @samp{qAttached} packet
36806 Return an indication of whether the remote server attached to an
36807 existing process or created a new process. When the multiprocess
36808 protocol extensions are supported (@pxref{multiprocess extensions}),
36809 @var{pid} is an integer in hexadecimal format identifying the target
36810 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
36811 the query packet will be simplified as @samp{qAttached}.
36813 This query is used, for example, to know whether the remote process
36814 should be detached or killed when a @value{GDBN} session is ended with
36815 the @code{quit} command.
36820 The remote server attached to an existing process.
36822 The remote server created a new process.
36824 A badly formed request or an error was encountered.
36828 Enable branch tracing for the current thread using bts tracing.
36833 Branch tracing has been enabled.
36835 A badly formed request or an error was encountered.
36839 Disable branch tracing for the current thread.
36844 Branch tracing has been disabled.
36846 A badly formed request or an error was encountered.
36849 @item Qbtrace-conf:bts:size=@var{value}
36850 Set the requested ring buffer size for new threads that use the
36851 btrace recording method in bts format.
36856 The ring buffer size has been set.
36858 A badly formed request or an error was encountered.
36863 @node Architecture-Specific Protocol Details
36864 @section Architecture-Specific Protocol Details
36866 This section describes how the remote protocol is applied to specific
36867 target architectures. Also see @ref{Standard Target Features}, for
36868 details of XML target descriptions for each architecture.
36871 * ARM-Specific Protocol Details::
36872 * MIPS-Specific Protocol Details::
36875 @node ARM-Specific Protocol Details
36876 @subsection @acronym{ARM}-specific Protocol Details
36879 * ARM Breakpoint Kinds::
36882 @node ARM Breakpoint Kinds
36883 @subsubsection @acronym{ARM} Breakpoint Kinds
36884 @cindex breakpoint kinds, @acronym{ARM}
36886 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36891 16-bit Thumb mode breakpoint.
36894 32-bit Thumb mode (Thumb-2) breakpoint.
36897 32-bit @acronym{ARM} mode breakpoint.
36901 @node MIPS-Specific Protocol Details
36902 @subsection @acronym{MIPS}-specific Protocol Details
36905 * MIPS Register packet Format::
36906 * MIPS Breakpoint Kinds::
36909 @node MIPS Register packet Format
36910 @subsubsection @acronym{MIPS} Register Packet Format
36911 @cindex register packet format, @acronym{MIPS}
36913 The following @code{g}/@code{G} packets have previously been defined.
36914 In the below, some thirty-two bit registers are transferred as
36915 sixty-four bits. Those registers should be zero/sign extended (which?)
36916 to fill the space allocated. Register bytes are transferred in target
36917 byte order. The two nibbles within a register byte are transferred
36918 most-significant -- least-significant.
36923 All registers are transferred as thirty-two bit quantities in the order:
36924 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
36925 registers; fsr; fir; fp.
36928 All registers are transferred as sixty-four bit quantities (including
36929 thirty-two bit registers such as @code{sr}). The ordering is the same
36934 @node MIPS Breakpoint Kinds
36935 @subsubsection @acronym{MIPS} Breakpoint Kinds
36936 @cindex breakpoint kinds, @acronym{MIPS}
36938 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
36943 16-bit @acronym{MIPS16} mode breakpoint.
36946 16-bit @acronym{microMIPS} mode breakpoint.
36949 32-bit standard @acronym{MIPS} mode breakpoint.
36952 32-bit @acronym{microMIPS} mode breakpoint.
36956 @node Tracepoint Packets
36957 @section Tracepoint Packets
36958 @cindex tracepoint packets
36959 @cindex packets, tracepoint
36961 Here we describe the packets @value{GDBN} uses to implement
36962 tracepoints (@pxref{Tracepoints}).
36966 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
36967 @cindex @samp{QTDP} packet
36968 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
36969 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
36970 the tracepoint is disabled. The @var{step} gives the tracepoint's step
36971 count, and @var{pass} gives its pass count. If an @samp{F} is present,
36972 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
36973 the number of bytes that the target should copy elsewhere to make room
36974 for the tracepoint. If an @samp{X} is present, it introduces a
36975 tracepoint condition, which consists of a hexadecimal length, followed
36976 by a comma and hex-encoded bytes, in a manner similar to action
36977 encodings as described below. If the trailing @samp{-} is present,
36978 further @samp{QTDP} packets will follow to specify this tracepoint's
36984 The packet was understood and carried out.
36986 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36988 The packet was not recognized.
36991 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
36992 Define actions to be taken when a tracepoint is hit. The @var{n} and
36993 @var{addr} must be the same as in the initial @samp{QTDP} packet for
36994 this tracepoint. This packet may only be sent immediately after
36995 another @samp{QTDP} packet that ended with a @samp{-}. If the
36996 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
36997 specifying more actions for this tracepoint.
36999 In the series of action packets for a given tracepoint, at most one
37000 can have an @samp{S} before its first @var{action}. If such a packet
37001 is sent, it and the following packets define ``while-stepping''
37002 actions. Any prior packets define ordinary actions --- that is, those
37003 taken when the tracepoint is first hit. If no action packet has an
37004 @samp{S}, then all the packets in the series specify ordinary
37005 tracepoint actions.
37007 The @samp{@var{action}@dots{}} portion of the packet is a series of
37008 actions, concatenated without separators. Each action has one of the
37014 Collect the registers whose bits are set in @var{mask},
37015 a hexadecimal number whose @var{i}'th bit is set if register number
37016 @var{i} should be collected. (The least significant bit is numbered
37017 zero.) Note that @var{mask} may be any number of digits long; it may
37018 not fit in a 32-bit word.
37020 @item M @var{basereg},@var{offset},@var{len}
37021 Collect @var{len} bytes of memory starting at the address in register
37022 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37023 @samp{-1}, then the range has a fixed address: @var{offset} is the
37024 address of the lowest byte to collect. The @var{basereg},
37025 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37026 values (the @samp{-1} value for @var{basereg} is a special case).
37028 @item X @var{len},@var{expr}
37029 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37030 it directs. The agent expression @var{expr} is as described in
37031 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37032 two-digit hex number in the packet; @var{len} is the number of bytes
37033 in the expression (and thus one-half the number of hex digits in the
37038 Any number of actions may be packed together in a single @samp{QTDP}
37039 packet, as long as the packet does not exceed the maximum packet
37040 length (400 bytes, for many stubs). There may be only one @samp{R}
37041 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37042 actions. Any registers referred to by @samp{M} and @samp{X} actions
37043 must be collected by a preceding @samp{R} action. (The
37044 ``while-stepping'' actions are treated as if they were attached to a
37045 separate tracepoint, as far as these restrictions are concerned.)
37050 The packet was understood and carried out.
37052 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37054 The packet was not recognized.
37057 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37058 @cindex @samp{QTDPsrc} packet
37059 Specify a source string of tracepoint @var{n} at address @var{addr}.
37060 This is useful to get accurate reproduction of the tracepoints
37061 originally downloaded at the beginning of the trace run. The @var{type}
37062 is the name of the tracepoint part, such as @samp{cond} for the
37063 tracepoint's conditional expression (see below for a list of types), while
37064 @var{bytes} is the string, encoded in hexadecimal.
37066 @var{start} is the offset of the @var{bytes} within the overall source
37067 string, while @var{slen} is the total length of the source string.
37068 This is intended for handling source strings that are longer than will
37069 fit in a single packet.
37070 @c Add detailed example when this info is moved into a dedicated
37071 @c tracepoint descriptions section.
37073 The available string types are @samp{at} for the location,
37074 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37075 @value{GDBN} sends a separate packet for each command in the action
37076 list, in the same order in which the commands are stored in the list.
37078 The target does not need to do anything with source strings except
37079 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37082 Although this packet is optional, and @value{GDBN} will only send it
37083 if the target replies with @samp{TracepointSource} @xref{General
37084 Query Packets}, it makes both disconnected tracing and trace files
37085 much easier to use. Otherwise the user must be careful that the
37086 tracepoints in effect while looking at trace frames are identical to
37087 the ones in effect during the trace run; even a small discrepancy
37088 could cause @samp{tdump} not to work, or a particular trace frame not
37091 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
37092 @cindex define trace state variable, remote request
37093 @cindex @samp{QTDV} packet
37094 Create a new trace state variable, number @var{n}, with an initial
37095 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37096 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37097 the option of not using this packet for initial values of zero; the
37098 target should simply create the trace state variables as they are
37099 mentioned in expressions. The value @var{builtin} should be 1 (one)
37100 if the trace state variable is builtin and 0 (zero) if it is not builtin.
37101 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
37102 @samp{qTsV} packet had it set. The contents of @var{name} is the
37103 hex-encoded name (without the leading @samp{$}) of the trace state
37106 @item QTFrame:@var{n}
37107 @cindex @samp{QTFrame} packet
37108 Select the @var{n}'th tracepoint frame from the buffer, and use the
37109 register and memory contents recorded there to answer subsequent
37110 request packets from @value{GDBN}.
37112 A successful reply from the stub indicates that the stub has found the
37113 requested frame. The response is a series of parts, concatenated
37114 without separators, describing the frame we selected. Each part has
37115 one of the following forms:
37119 The selected frame is number @var{n} in the trace frame buffer;
37120 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37121 was no frame matching the criteria in the request packet.
37124 The selected trace frame records a hit of tracepoint number @var{t};
37125 @var{t} is a hexadecimal number.
37129 @item QTFrame:pc:@var{addr}
37130 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37131 currently selected frame whose PC is @var{addr};
37132 @var{addr} is a hexadecimal number.
37134 @item QTFrame:tdp:@var{t}
37135 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37136 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37137 is a hexadecimal number.
37139 @item QTFrame:range:@var{start}:@var{end}
37140 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37141 currently selected frame whose PC is between @var{start} (inclusive)
37142 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37145 @item QTFrame:outside:@var{start}:@var{end}
37146 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37147 frame @emph{outside} the given range of addresses (exclusive).
37150 @cindex @samp{qTMinFTPILen} packet
37151 This packet requests the minimum length of instruction at which a fast
37152 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37153 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37154 it depends on the target system being able to create trampolines in
37155 the first 64K of memory, which might or might not be possible for that
37156 system. So the reply to this packet will be 4 if it is able to
37163 The minimum instruction length is currently unknown.
37165 The minimum instruction length is @var{length}, where @var{length}
37166 is a hexadecimal number greater or equal to 1. A reply
37167 of 1 means that a fast tracepoint may be placed on any instruction
37168 regardless of size.
37170 An error has occurred.
37172 An empty reply indicates that the request is not supported by the stub.
37176 @cindex @samp{QTStart} packet
37177 Begin the tracepoint experiment. Begin collecting data from
37178 tracepoint hits in the trace frame buffer. This packet supports the
37179 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37180 instruction reply packet}).
37183 @cindex @samp{QTStop} packet
37184 End the tracepoint experiment. Stop collecting trace frames.
37186 @item QTEnable:@var{n}:@var{addr}
37188 @cindex @samp{QTEnable} packet
37189 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37190 experiment. If the tracepoint was previously disabled, then collection
37191 of data from it will resume.
37193 @item QTDisable:@var{n}:@var{addr}
37195 @cindex @samp{QTDisable} packet
37196 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37197 experiment. No more data will be collected from the tracepoint unless
37198 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37201 @cindex @samp{QTinit} packet
37202 Clear the table of tracepoints, and empty the trace frame buffer.
37204 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37205 @cindex @samp{QTro} packet
37206 Establish the given ranges of memory as ``transparent''. The stub
37207 will answer requests for these ranges from memory's current contents,
37208 if they were not collected as part of the tracepoint hit.
37210 @value{GDBN} uses this to mark read-only regions of memory, like those
37211 containing program code. Since these areas never change, they should
37212 still have the same contents they did when the tracepoint was hit, so
37213 there's no reason for the stub to refuse to provide their contents.
37215 @item QTDisconnected:@var{value}
37216 @cindex @samp{QTDisconnected} packet
37217 Set the choice to what to do with the tracing run when @value{GDBN}
37218 disconnects from the target. A @var{value} of 1 directs the target to
37219 continue the tracing run, while 0 tells the target to stop tracing if
37220 @value{GDBN} is no longer in the picture.
37223 @cindex @samp{qTStatus} packet
37224 Ask the stub if there is a trace experiment running right now.
37226 The reply has the form:
37230 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37231 @var{running} is a single digit @code{1} if the trace is presently
37232 running, or @code{0} if not. It is followed by semicolon-separated
37233 optional fields that an agent may use to report additional status.
37237 If the trace is not running, the agent may report any of several
37238 explanations as one of the optional fields:
37243 No trace has been run yet.
37245 @item tstop[:@var{text}]:0
37246 The trace was stopped by a user-originated stop command. The optional
37247 @var{text} field is a user-supplied string supplied as part of the
37248 stop command (for instance, an explanation of why the trace was
37249 stopped manually). It is hex-encoded.
37252 The trace stopped because the trace buffer filled up.
37254 @item tdisconnected:0
37255 The trace stopped because @value{GDBN} disconnected from the target.
37257 @item tpasscount:@var{tpnum}
37258 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37260 @item terror:@var{text}:@var{tpnum}
37261 The trace stopped because tracepoint @var{tpnum} had an error. The
37262 string @var{text} is available to describe the nature of the error
37263 (for instance, a divide by zero in the condition expression); it
37267 The trace stopped for some other reason.
37271 Additional optional fields supply statistical and other information.
37272 Although not required, they are extremely useful for users monitoring
37273 the progress of a trace run. If a trace has stopped, and these
37274 numbers are reported, they must reflect the state of the just-stopped
37279 @item tframes:@var{n}
37280 The number of trace frames in the buffer.
37282 @item tcreated:@var{n}
37283 The total number of trace frames created during the run. This may
37284 be larger than the trace frame count, if the buffer is circular.
37286 @item tsize:@var{n}
37287 The total size of the trace buffer, in bytes.
37289 @item tfree:@var{n}
37290 The number of bytes still unused in the buffer.
37292 @item circular:@var{n}
37293 The value of the circular trace buffer flag. @code{1} means that the
37294 trace buffer is circular and old trace frames will be discarded if
37295 necessary to make room, @code{0} means that the trace buffer is linear
37298 @item disconn:@var{n}
37299 The value of the disconnected tracing flag. @code{1} means that
37300 tracing will continue after @value{GDBN} disconnects, @code{0} means
37301 that the trace run will stop.
37305 @item qTP:@var{tp}:@var{addr}
37306 @cindex tracepoint status, remote request
37307 @cindex @samp{qTP} packet
37308 Ask the stub for the current state of tracepoint number @var{tp} at
37309 address @var{addr}.
37313 @item V@var{hits}:@var{usage}
37314 The tracepoint has been hit @var{hits} times so far during the trace
37315 run, and accounts for @var{usage} in the trace buffer. Note that
37316 @code{while-stepping} steps are not counted as separate hits, but the
37317 steps' space consumption is added into the usage number.
37321 @item qTV:@var{var}
37322 @cindex trace state variable value, remote request
37323 @cindex @samp{qTV} packet
37324 Ask the stub for the value of the trace state variable number @var{var}.
37329 The value of the variable is @var{value}. This will be the current
37330 value of the variable if the user is examining a running target, or a
37331 saved value if the variable was collected in the trace frame that the
37332 user is looking at. Note that multiple requests may result in
37333 different reply values, such as when requesting values while the
37334 program is running.
37337 The value of the variable is unknown. This would occur, for example,
37338 if the user is examining a trace frame in which the requested variable
37343 @cindex @samp{qTfP} packet
37345 @cindex @samp{qTsP} packet
37346 These packets request data about tracepoints that are being used by
37347 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37348 of data, and multiple @code{qTsP} to get additional pieces. Replies
37349 to these packets generally take the form of the @code{QTDP} packets
37350 that define tracepoints. (FIXME add detailed syntax)
37353 @cindex @samp{qTfV} packet
37355 @cindex @samp{qTsV} packet
37356 These packets request data about trace state variables that are on the
37357 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37358 and multiple @code{qTsV} to get additional variables. Replies to
37359 these packets follow the syntax of the @code{QTDV} packets that define
37360 trace state variables.
37366 @cindex @samp{qTfSTM} packet
37367 @cindex @samp{qTsSTM} packet
37368 These packets request data about static tracepoint markers that exist
37369 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37370 first piece of data, and multiple @code{qTsSTM} to get additional
37371 pieces. Replies to these packets take the following form:
37375 @item m @var{address}:@var{id}:@var{extra}
37377 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37378 a comma-separated list of markers
37380 (lower case letter @samp{L}) denotes end of list.
37382 An error occurred. The error number @var{nn} is given as hex digits.
37384 An empty reply indicates that the request is not supported by the
37388 The @var{address} is encoded in hex;
37389 @var{id} and @var{extra} are strings encoded in hex.
37391 In response to each query, the target will reply with a list of one or
37392 more markers, separated by commas. @value{GDBN} will respond to each
37393 reply with a request for more markers (using the @samp{qs} form of the
37394 query), until the target responds with @samp{l} (lower-case ell, for
37397 @item qTSTMat:@var{address}
37399 @cindex @samp{qTSTMat} packet
37400 This packets requests data about static tracepoint markers in the
37401 target program at @var{address}. Replies to this packet follow the
37402 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
37403 tracepoint markers.
37405 @item QTSave:@var{filename}
37406 @cindex @samp{QTSave} packet
37407 This packet directs the target to save trace data to the file name
37408 @var{filename} in the target's filesystem. The @var{filename} is encoded
37409 as a hex string; the interpretation of the file name (relative vs
37410 absolute, wild cards, etc) is up to the target.
37412 @item qTBuffer:@var{offset},@var{len}
37413 @cindex @samp{qTBuffer} packet
37414 Return up to @var{len} bytes of the current contents of trace buffer,
37415 starting at @var{offset}. The trace buffer is treated as if it were
37416 a contiguous collection of traceframes, as per the trace file format.
37417 The reply consists as many hex-encoded bytes as the target can deliver
37418 in a packet; it is not an error to return fewer than were asked for.
37419 A reply consisting of just @code{l} indicates that no bytes are
37422 @item QTBuffer:circular:@var{value}
37423 This packet directs the target to use a circular trace buffer if
37424 @var{value} is 1, or a linear buffer if the value is 0.
37426 @item QTBuffer:size:@var{size}
37427 @anchor{QTBuffer-size}
37428 @cindex @samp{QTBuffer size} packet
37429 This packet directs the target to make the trace buffer be of size
37430 @var{size} if possible. A value of @code{-1} tells the target to
37431 use whatever size it prefers.
37433 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
37434 @cindex @samp{QTNotes} packet
37435 This packet adds optional textual notes to the trace run. Allowable
37436 types include @code{user}, @code{notes}, and @code{tstop}, the
37437 @var{text} fields are arbitrary strings, hex-encoded.
37441 @subsection Relocate instruction reply packet
37442 When installing fast tracepoints in memory, the target may need to
37443 relocate the instruction currently at the tracepoint address to a
37444 different address in memory. For most instructions, a simple copy is
37445 enough, but, for example, call instructions that implicitly push the
37446 return address on the stack, and relative branches or other
37447 PC-relative instructions require offset adjustment, so that the effect
37448 of executing the instruction at a different address is the same as if
37449 it had executed in the original location.
37451 In response to several of the tracepoint packets, the target may also
37452 respond with a number of intermediate @samp{qRelocInsn} request
37453 packets before the final result packet, to have @value{GDBN} handle
37454 this relocation operation. If a packet supports this mechanism, its
37455 documentation will explicitly say so. See for example the above
37456 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
37457 format of the request is:
37460 @item qRelocInsn:@var{from};@var{to}
37462 This requests @value{GDBN} to copy instruction at address @var{from}
37463 to address @var{to}, possibly adjusted so that executing the
37464 instruction at @var{to} has the same effect as executing it at
37465 @var{from}. @value{GDBN} writes the adjusted instruction to target
37466 memory starting at @var{to}.
37471 @item qRelocInsn:@var{adjusted_size}
37472 Informs the stub the relocation is complete. The @var{adjusted_size} is
37473 the length in bytes of resulting relocated instruction sequence.
37475 A badly formed request was detected, or an error was encountered while
37476 relocating the instruction.
37479 @node Host I/O Packets
37480 @section Host I/O Packets
37481 @cindex Host I/O, remote protocol
37482 @cindex file transfer, remote protocol
37484 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
37485 operations on the far side of a remote link. For example, Host I/O is
37486 used to upload and download files to a remote target with its own
37487 filesystem. Host I/O uses the same constant values and data structure
37488 layout as the target-initiated File-I/O protocol. However, the
37489 Host I/O packets are structured differently. The target-initiated
37490 protocol relies on target memory to store parameters and buffers.
37491 Host I/O requests are initiated by @value{GDBN}, and the
37492 target's memory is not involved. @xref{File-I/O Remote Protocol
37493 Extension}, for more details on the target-initiated protocol.
37495 The Host I/O request packets all encode a single operation along with
37496 its arguments. They have this format:
37500 @item vFile:@var{operation}: @var{parameter}@dots{}
37501 @var{operation} is the name of the particular request; the target
37502 should compare the entire packet name up to the second colon when checking
37503 for a supported operation. The format of @var{parameter} depends on
37504 the operation. Numbers are always passed in hexadecimal. Negative
37505 numbers have an explicit minus sign (i.e.@: two's complement is not
37506 used). Strings (e.g.@: filenames) are encoded as a series of
37507 hexadecimal bytes. The last argument to a system call may be a
37508 buffer of escaped binary data (@pxref{Binary Data}).
37512 The valid responses to Host I/O packets are:
37516 @item F @var{result} [, @var{errno}] [; @var{attachment}]
37517 @var{result} is the integer value returned by this operation, usually
37518 non-negative for success and -1 for errors. If an error has occured,
37519 @var{errno} will be included in the result specifying a
37520 value defined by the File-I/O protocol (@pxref{Errno Values}). For
37521 operations which return data, @var{attachment} supplies the data as a
37522 binary buffer. Binary buffers in response packets are escaped in the
37523 normal way (@pxref{Binary Data}). See the individual packet
37524 documentation for the interpretation of @var{result} and
37528 An empty response indicates that this operation is not recognized.
37532 These are the supported Host I/O operations:
37535 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
37536 Open a file at @var{filename} and return a file descriptor for it, or
37537 return -1 if an error occurs. The @var{filename} is a string,
37538 @var{flags} is an integer indicating a mask of open flags
37539 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
37540 of mode bits to use if the file is created (@pxref{mode_t Values}).
37541 @xref{open}, for details of the open flags and mode values.
37543 @item vFile:close: @var{fd}
37544 Close the open file corresponding to @var{fd} and return 0, or
37545 -1 if an error occurs.
37547 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
37548 Read data from the open file corresponding to @var{fd}. Up to
37549 @var{count} bytes will be read from the file, starting at @var{offset}
37550 relative to the start of the file. The target may read fewer bytes;
37551 common reasons include packet size limits and an end-of-file
37552 condition. The number of bytes read is returned. Zero should only be
37553 returned for a successful read at the end of the file, or if
37554 @var{count} was zero.
37556 The data read should be returned as a binary attachment on success.
37557 If zero bytes were read, the response should include an empty binary
37558 attachment (i.e.@: a trailing semicolon). The return value is the
37559 number of target bytes read; the binary attachment may be longer if
37560 some characters were escaped.
37562 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
37563 Write @var{data} (a binary buffer) to the open file corresponding
37564 to @var{fd}. Start the write at @var{offset} from the start of the
37565 file. Unlike many @code{write} system calls, there is no
37566 separate @var{count} argument; the length of @var{data} in the
37567 packet is used. @samp{vFile:write} returns the number of bytes written,
37568 which may be shorter than the length of @var{data}, or -1 if an
37571 @item vFile:fstat: @var{fd}
37572 Get information about the open file corresponding to @var{fd}.
37573 On success the information is returned as a binary attachment
37574 and the return value is the size of this attachment in bytes.
37575 If an error occurs the return value is -1. The format of the
37576 returned binary attachment is as described in @ref{struct stat}.
37578 @item vFile:unlink: @var{filename}
37579 Delete the file at @var{filename} on the target. Return 0,
37580 or -1 if an error occurs. The @var{filename} is a string.
37582 @item vFile:readlink: @var{filename}
37583 Read value of symbolic link @var{filename} on the target. Return
37584 the number of bytes read, or -1 if an error occurs.
37586 The data read should be returned as a binary attachment on success.
37587 If zero bytes were read, the response should include an empty binary
37588 attachment (i.e.@: a trailing semicolon). The return value is the
37589 number of target bytes read; the binary attachment may be longer if
37590 some characters were escaped.
37595 @section Interrupts
37596 @cindex interrupts (remote protocol)
37598 When a program on the remote target is running, @value{GDBN} may
37599 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
37600 a @code{BREAK} followed by @code{g},
37601 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
37603 The precise meaning of @code{BREAK} is defined by the transport
37604 mechanism and may, in fact, be undefined. @value{GDBN} does not
37605 currently define a @code{BREAK} mechanism for any of the network
37606 interfaces except for TCP, in which case @value{GDBN} sends the
37607 @code{telnet} BREAK sequence.
37609 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
37610 transport mechanisms. It is represented by sending the single byte
37611 @code{0x03} without any of the usual packet overhead described in
37612 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
37613 transmitted as part of a packet, it is considered to be packet data
37614 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
37615 (@pxref{X packet}), used for binary downloads, may include an unescaped
37616 @code{0x03} as part of its packet.
37618 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
37619 When Linux kernel receives this sequence from serial port,
37620 it stops execution and connects to gdb.
37622 Stubs are not required to recognize these interrupt mechanisms and the
37623 precise meaning associated with receipt of the interrupt is
37624 implementation defined. If the target supports debugging of multiple
37625 threads and/or processes, it should attempt to interrupt all
37626 currently-executing threads and processes.
37627 If the stub is successful at interrupting the
37628 running program, it should send one of the stop
37629 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
37630 of successfully stopping the program in all-stop mode, and a stop reply
37631 for each stopped thread in non-stop mode.
37632 Interrupts received while the
37633 program is stopped are discarded.
37635 @node Notification Packets
37636 @section Notification Packets
37637 @cindex notification packets
37638 @cindex packets, notification
37640 The @value{GDBN} remote serial protocol includes @dfn{notifications},
37641 packets that require no acknowledgment. Both the GDB and the stub
37642 may send notifications (although the only notifications defined at
37643 present are sent by the stub). Notifications carry information
37644 without incurring the round-trip latency of an acknowledgment, and so
37645 are useful for low-impact communications where occasional packet loss
37648 A notification packet has the form @samp{% @var{data} #
37649 @var{checksum}}, where @var{data} is the content of the notification,
37650 and @var{checksum} is a checksum of @var{data}, computed and formatted
37651 as for ordinary @value{GDBN} packets. A notification's @var{data}
37652 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
37653 receiving a notification, the recipient sends no @samp{+} or @samp{-}
37654 to acknowledge the notification's receipt or to report its corruption.
37656 Every notification's @var{data} begins with a name, which contains no
37657 colon characters, followed by a colon character.
37659 Recipients should silently ignore corrupted notifications and
37660 notifications they do not understand. Recipients should restart
37661 timeout periods on receipt of a well-formed notification, whether or
37662 not they understand it.
37664 Senders should only send the notifications described here when this
37665 protocol description specifies that they are permitted. In the
37666 future, we may extend the protocol to permit existing notifications in
37667 new contexts; this rule helps older senders avoid confusing newer
37670 (Older versions of @value{GDBN} ignore bytes received until they see
37671 the @samp{$} byte that begins an ordinary packet, so new stubs may
37672 transmit notifications without fear of confusing older clients. There
37673 are no notifications defined for @value{GDBN} to send at the moment, but we
37674 assume that most older stubs would ignore them, as well.)
37676 Each notification is comprised of three parts:
37678 @item @var{name}:@var{event}
37679 The notification packet is sent by the side that initiates the
37680 exchange (currently, only the stub does that), with @var{event}
37681 carrying the specific information about the notification, and
37682 @var{name} specifying the name of the notification.
37684 The acknowledge sent by the other side, usually @value{GDBN}, to
37685 acknowledge the exchange and request the event.
37688 The purpose of an asynchronous notification mechanism is to report to
37689 @value{GDBN} that something interesting happened in the remote stub.
37691 The remote stub may send notification @var{name}:@var{event}
37692 at any time, but @value{GDBN} acknowledges the notification when
37693 appropriate. The notification event is pending before @value{GDBN}
37694 acknowledges. Only one notification at a time may be pending; if
37695 additional events occur before @value{GDBN} has acknowledged the
37696 previous notification, they must be queued by the stub for later
37697 synchronous transmission in response to @var{ack} packets from
37698 @value{GDBN}. Because the notification mechanism is unreliable,
37699 the stub is permitted to resend a notification if it believes
37700 @value{GDBN} may not have received it.
37702 Specifically, notifications may appear when @value{GDBN} is not
37703 otherwise reading input from the stub, or when @value{GDBN} is
37704 expecting to read a normal synchronous response or a
37705 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
37706 Notification packets are distinct from any other communication from
37707 the stub so there is no ambiguity.
37709 After receiving a notification, @value{GDBN} shall acknowledge it by
37710 sending a @var{ack} packet as a regular, synchronous request to the
37711 stub. Such acknowledgment is not required to happen immediately, as
37712 @value{GDBN} is permitted to send other, unrelated packets to the
37713 stub first, which the stub should process normally.
37715 Upon receiving a @var{ack} packet, if the stub has other queued
37716 events to report to @value{GDBN}, it shall respond by sending a
37717 normal @var{event}. @value{GDBN} shall then send another @var{ack}
37718 packet to solicit further responses; again, it is permitted to send
37719 other, unrelated packets as well which the stub should process
37722 If the stub receives a @var{ack} packet and there are no additional
37723 @var{event} to report, the stub shall return an @samp{OK} response.
37724 At this point, @value{GDBN} has finished processing a notification
37725 and the stub has completed sending any queued events. @value{GDBN}
37726 won't accept any new notifications until the final @samp{OK} is
37727 received . If further notification events occur, the stub shall send
37728 a new notification, @value{GDBN} shall accept the notification, and
37729 the process shall be repeated.
37731 The process of asynchronous notification can be illustrated by the
37734 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
37737 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
37739 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
37744 The following notifications are defined:
37745 @multitable @columnfractions 0.12 0.12 0.38 0.38
37754 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
37755 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
37756 for information on how these notifications are acknowledged by
37758 @tab Report an asynchronous stop event in non-stop mode.
37762 @node Remote Non-Stop
37763 @section Remote Protocol Support for Non-Stop Mode
37765 @value{GDBN}'s remote protocol supports non-stop debugging of
37766 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
37767 supports non-stop mode, it should report that to @value{GDBN} by including
37768 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
37770 @value{GDBN} typically sends a @samp{QNonStop} packet only when
37771 establishing a new connection with the stub. Entering non-stop mode
37772 does not alter the state of any currently-running threads, but targets
37773 must stop all threads in any already-attached processes when entering
37774 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
37775 probe the target state after a mode change.
37777 In non-stop mode, when an attached process encounters an event that
37778 would otherwise be reported with a stop reply, it uses the
37779 asynchronous notification mechanism (@pxref{Notification Packets}) to
37780 inform @value{GDBN}. In contrast to all-stop mode, where all threads
37781 in all processes are stopped when a stop reply is sent, in non-stop
37782 mode only the thread reporting the stop event is stopped. That is,
37783 when reporting a @samp{S} or @samp{T} response to indicate completion
37784 of a step operation, hitting a breakpoint, or a fault, only the
37785 affected thread is stopped; any other still-running threads continue
37786 to run. When reporting a @samp{W} or @samp{X} response, all running
37787 threads belonging to other attached processes continue to run.
37789 In non-stop mode, the target shall respond to the @samp{?} packet as
37790 follows. First, any incomplete stop reply notification/@samp{vStopped}
37791 sequence in progress is abandoned. The target must begin a new
37792 sequence reporting stop events for all stopped threads, whether or not
37793 it has previously reported those events to @value{GDBN}. The first
37794 stop reply is sent as a synchronous reply to the @samp{?} packet, and
37795 subsequent stop replies are sent as responses to @samp{vStopped} packets
37796 using the mechanism described above. The target must not send
37797 asynchronous stop reply notifications until the sequence is complete.
37798 If all threads are running when the target receives the @samp{?} packet,
37799 or if the target is not attached to any process, it shall respond
37802 If the stub supports non-stop mode, it should also support the
37803 @samp{swbreak} stop reason if software breakpoints are supported, and
37804 the @samp{hwbreak} stop reason if hardware breakpoints are supported
37805 (@pxref{swbreak stop reason}). This is because given the asynchronous
37806 nature of non-stop mode, between the time a thread hits a breakpoint
37807 and the time the event is finally processed by @value{GDBN}, the
37808 breakpoint may have already been removed from the target. Due to
37809 this, @value{GDBN} needs to be able to tell whether a trap stop was
37810 caused by a delayed breakpoint event, which should be ignored, as
37811 opposed to a random trap signal, which should be reported to the user.
37812 Note the @samp{swbreak} feature implies that the target is responsible
37813 for adjusting the PC when a software breakpoint triggers, if
37814 necessary, such as on the x86 architecture.
37816 @node Packet Acknowledgment
37817 @section Packet Acknowledgment
37819 @cindex acknowledgment, for @value{GDBN} remote
37820 @cindex packet acknowledgment, for @value{GDBN} remote
37821 By default, when either the host or the target machine receives a packet,
37822 the first response expected is an acknowledgment: either @samp{+} (to indicate
37823 the package was received correctly) or @samp{-} (to request retransmission).
37824 This mechanism allows the @value{GDBN} remote protocol to operate over
37825 unreliable transport mechanisms, such as a serial line.
37827 In cases where the transport mechanism is itself reliable (such as a pipe or
37828 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
37829 It may be desirable to disable them in that case to reduce communication
37830 overhead, or for other reasons. This can be accomplished by means of the
37831 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
37833 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
37834 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
37835 and response format still includes the normal checksum, as described in
37836 @ref{Overview}, but the checksum may be ignored by the receiver.
37838 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
37839 no-acknowledgment mode, it should report that to @value{GDBN}
37840 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
37841 @pxref{qSupported}.
37842 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
37843 disabled via the @code{set remote noack-packet off} command
37844 (@pxref{Remote Configuration}),
37845 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
37846 Only then may the stub actually turn off packet acknowledgments.
37847 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
37848 response, which can be safely ignored by the stub.
37850 Note that @code{set remote noack-packet} command only affects negotiation
37851 between @value{GDBN} and the stub when subsequent connections are made;
37852 it does not affect the protocol acknowledgment state for any current
37854 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
37855 new connection is established,
37856 there is also no protocol request to re-enable the acknowledgments
37857 for the current connection, once disabled.
37862 Example sequence of a target being re-started. Notice how the restart
37863 does not get any direct output:
37868 @emph{target restarts}
37871 <- @code{T001:1234123412341234}
37875 Example sequence of a target being stepped by a single instruction:
37878 -> @code{G1445@dots{}}
37883 <- @code{T001:1234123412341234}
37887 <- @code{1455@dots{}}
37891 @node File-I/O Remote Protocol Extension
37892 @section File-I/O Remote Protocol Extension
37893 @cindex File-I/O remote protocol extension
37896 * File-I/O Overview::
37897 * Protocol Basics::
37898 * The F Request Packet::
37899 * The F Reply Packet::
37900 * The Ctrl-C Message::
37902 * List of Supported Calls::
37903 * Protocol-specific Representation of Datatypes::
37905 * File-I/O Examples::
37908 @node File-I/O Overview
37909 @subsection File-I/O Overview
37910 @cindex file-i/o overview
37912 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
37913 target to use the host's file system and console I/O to perform various
37914 system calls. System calls on the target system are translated into a
37915 remote protocol packet to the host system, which then performs the needed
37916 actions and returns a response packet to the target system.
37917 This simulates file system operations even on targets that lack file systems.
37919 The protocol is defined to be independent of both the host and target systems.
37920 It uses its own internal representation of datatypes and values. Both
37921 @value{GDBN} and the target's @value{GDBN} stub are responsible for
37922 translating the system-dependent value representations into the internal
37923 protocol representations when data is transmitted.
37925 The communication is synchronous. A system call is possible only when
37926 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
37927 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
37928 the target is stopped to allow deterministic access to the target's
37929 memory. Therefore File-I/O is not interruptible by target signals. On
37930 the other hand, it is possible to interrupt File-I/O by a user interrupt
37931 (@samp{Ctrl-C}) within @value{GDBN}.
37933 The target's request to perform a host system call does not finish
37934 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
37935 after finishing the system call, the target returns to continuing the
37936 previous activity (continue, step). No additional continue or step
37937 request from @value{GDBN} is required.
37940 (@value{GDBP}) continue
37941 <- target requests 'system call X'
37942 target is stopped, @value{GDBN} executes system call
37943 -> @value{GDBN} returns result
37944 ... target continues, @value{GDBN} returns to wait for the target
37945 <- target hits breakpoint and sends a Txx packet
37948 The protocol only supports I/O on the console and to regular files on
37949 the host file system. Character or block special devices, pipes,
37950 named pipes, sockets or any other communication method on the host
37951 system are not supported by this protocol.
37953 File I/O is not supported in non-stop mode.
37955 @node Protocol Basics
37956 @subsection Protocol Basics
37957 @cindex protocol basics, file-i/o
37959 The File-I/O protocol uses the @code{F} packet as the request as well
37960 as reply packet. Since a File-I/O system call can only occur when
37961 @value{GDBN} is waiting for a response from the continuing or stepping target,
37962 the File-I/O request is a reply that @value{GDBN} has to expect as a result
37963 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
37964 This @code{F} packet contains all information needed to allow @value{GDBN}
37965 to call the appropriate host system call:
37969 A unique identifier for the requested system call.
37972 All parameters to the system call. Pointers are given as addresses
37973 in the target memory address space. Pointers to strings are given as
37974 pointer/length pair. Numerical values are given as they are.
37975 Numerical control flags are given in a protocol-specific representation.
37979 At this point, @value{GDBN} has to perform the following actions.
37983 If the parameters include pointer values to data needed as input to a
37984 system call, @value{GDBN} requests this data from the target with a
37985 standard @code{m} packet request. This additional communication has to be
37986 expected by the target implementation and is handled as any other @code{m}
37990 @value{GDBN} translates all value from protocol representation to host
37991 representation as needed. Datatypes are coerced into the host types.
37994 @value{GDBN} calls the system call.
37997 It then coerces datatypes back to protocol representation.
38000 If the system call is expected to return data in buffer space specified
38001 by pointer parameters to the call, the data is transmitted to the
38002 target using a @code{M} or @code{X} packet. This packet has to be expected
38003 by the target implementation and is handled as any other @code{M} or @code{X}
38008 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38009 necessary information for the target to continue. This at least contains
38016 @code{errno}, if has been changed by the system call.
38023 After having done the needed type and value coercion, the target continues
38024 the latest continue or step action.
38026 @node The F Request Packet
38027 @subsection The @code{F} Request Packet
38028 @cindex file-i/o request packet
38029 @cindex @code{F} request packet
38031 The @code{F} request packet has the following format:
38034 @item F@var{call-id},@var{parameter@dots{}}
38036 @var{call-id} is the identifier to indicate the host system call to be called.
38037 This is just the name of the function.
38039 @var{parameter@dots{}} are the parameters to the system call.
38040 Parameters are hexadecimal integer values, either the actual values in case
38041 of scalar datatypes, pointers to target buffer space in case of compound
38042 datatypes and unspecified memory areas, or pointer/length pairs in case
38043 of string parameters. These are appended to the @var{call-id} as a
38044 comma-delimited list. All values are transmitted in ASCII
38045 string representation, pointer/length pairs separated by a slash.
38051 @node The F Reply Packet
38052 @subsection The @code{F} Reply Packet
38053 @cindex file-i/o reply packet
38054 @cindex @code{F} reply packet
38056 The @code{F} reply packet has the following format:
38060 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38062 @var{retcode} is the return code of the system call as hexadecimal value.
38064 @var{errno} is the @code{errno} set by the call, in protocol-specific
38066 This parameter can be omitted if the call was successful.
38068 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38069 case, @var{errno} must be sent as well, even if the call was successful.
38070 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38077 or, if the call was interrupted before the host call has been performed:
38084 assuming 4 is the protocol-specific representation of @code{EINTR}.
38089 @node The Ctrl-C Message
38090 @subsection The @samp{Ctrl-C} Message
38091 @cindex ctrl-c message, in file-i/o protocol
38093 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38094 reply packet (@pxref{The F Reply Packet}),
38095 the target should behave as if it had
38096 gotten a break message. The meaning for the target is ``system call
38097 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38098 (as with a break message) and return to @value{GDBN} with a @code{T02}
38101 It's important for the target to know in which
38102 state the system call was interrupted. There are two possible cases:
38106 The system call hasn't been performed on the host yet.
38109 The system call on the host has been finished.
38113 These two states can be distinguished by the target by the value of the
38114 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38115 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38116 on POSIX systems. In any other case, the target may presume that the
38117 system call has been finished --- successfully or not --- and should behave
38118 as if the break message arrived right after the system call.
38120 @value{GDBN} must behave reliably. If the system call has not been called
38121 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38122 @code{errno} in the packet. If the system call on the host has been finished
38123 before the user requests a break, the full action must be finished by
38124 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38125 The @code{F} packet may only be sent when either nothing has happened
38126 or the full action has been completed.
38129 @subsection Console I/O
38130 @cindex console i/o as part of file-i/o
38132 By default and if not explicitly closed by the target system, the file
38133 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38134 on the @value{GDBN} console is handled as any other file output operation
38135 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38136 by @value{GDBN} so that after the target read request from file descriptor
38137 0 all following typing is buffered until either one of the following
38142 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38144 system call is treated as finished.
38147 The user presses @key{RET}. This is treated as end of input with a trailing
38151 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38152 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38156 If the user has typed more characters than fit in the buffer given to
38157 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38158 either another @code{read(0, @dots{})} is requested by the target, or debugging
38159 is stopped at the user's request.
38162 @node List of Supported Calls
38163 @subsection List of Supported Calls
38164 @cindex list of supported file-i/o calls
38181 @unnumberedsubsubsec open
38182 @cindex open, file-i/o system call
38187 int open(const char *pathname, int flags);
38188 int open(const char *pathname, int flags, mode_t mode);
38192 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38195 @var{flags} is the bitwise @code{OR} of the following values:
38199 If the file does not exist it will be created. The host
38200 rules apply as far as file ownership and time stamps
38204 When used with @code{O_CREAT}, if the file already exists it is
38205 an error and open() fails.
38208 If the file already exists and the open mode allows
38209 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38210 truncated to zero length.
38213 The file is opened in append mode.
38216 The file is opened for reading only.
38219 The file is opened for writing only.
38222 The file is opened for reading and writing.
38226 Other bits are silently ignored.
38230 @var{mode} is the bitwise @code{OR} of the following values:
38234 User has read permission.
38237 User has write permission.
38240 Group has read permission.
38243 Group has write permission.
38246 Others have read permission.
38249 Others have write permission.
38253 Other bits are silently ignored.
38256 @item Return value:
38257 @code{open} returns the new file descriptor or -1 if an error
38264 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38267 @var{pathname} refers to a directory.
38270 The requested access is not allowed.
38273 @var{pathname} was too long.
38276 A directory component in @var{pathname} does not exist.
38279 @var{pathname} refers to a device, pipe, named pipe or socket.
38282 @var{pathname} refers to a file on a read-only filesystem and
38283 write access was requested.
38286 @var{pathname} is an invalid pointer value.
38289 No space on device to create the file.
38292 The process already has the maximum number of files open.
38295 The limit on the total number of files open on the system
38299 The call was interrupted by the user.
38305 @unnumberedsubsubsec close
38306 @cindex close, file-i/o system call
38315 @samp{Fclose,@var{fd}}
38317 @item Return value:
38318 @code{close} returns zero on success, or -1 if an error occurred.
38324 @var{fd} isn't a valid open file descriptor.
38327 The call was interrupted by the user.
38333 @unnumberedsubsubsec read
38334 @cindex read, file-i/o system call
38339 int read(int fd, void *buf, unsigned int count);
38343 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38345 @item Return value:
38346 On success, the number of bytes read is returned.
38347 Zero indicates end of file. If count is zero, read
38348 returns zero as well. On error, -1 is returned.
38354 @var{fd} is not a valid file descriptor or is not open for
38358 @var{bufptr} is an invalid pointer value.
38361 The call was interrupted by the user.
38367 @unnumberedsubsubsec write
38368 @cindex write, file-i/o system call
38373 int write(int fd, const void *buf, unsigned int count);
38377 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
38379 @item Return value:
38380 On success, the number of bytes written are returned.
38381 Zero indicates nothing was written. On error, -1
38388 @var{fd} is not a valid file descriptor or is not open for
38392 @var{bufptr} is an invalid pointer value.
38395 An attempt was made to write a file that exceeds the
38396 host-specific maximum file size allowed.
38399 No space on device to write the data.
38402 The call was interrupted by the user.
38408 @unnumberedsubsubsec lseek
38409 @cindex lseek, file-i/o system call
38414 long lseek (int fd, long offset, int flag);
38418 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
38420 @var{flag} is one of:
38424 The offset is set to @var{offset} bytes.
38427 The offset is set to its current location plus @var{offset}
38431 The offset is set to the size of the file plus @var{offset}
38435 @item Return value:
38436 On success, the resulting unsigned offset in bytes from
38437 the beginning of the file is returned. Otherwise, a
38438 value of -1 is returned.
38444 @var{fd} is not a valid open file descriptor.
38447 @var{fd} is associated with the @value{GDBN} console.
38450 @var{flag} is not a proper value.
38453 The call was interrupted by the user.
38459 @unnumberedsubsubsec rename
38460 @cindex rename, file-i/o system call
38465 int rename(const char *oldpath, const char *newpath);
38469 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
38471 @item Return value:
38472 On success, zero is returned. On error, -1 is returned.
38478 @var{newpath} is an existing directory, but @var{oldpath} is not a
38482 @var{newpath} is a non-empty directory.
38485 @var{oldpath} or @var{newpath} is a directory that is in use by some
38489 An attempt was made to make a directory a subdirectory
38493 A component used as a directory in @var{oldpath} or new
38494 path is not a directory. Or @var{oldpath} is a directory
38495 and @var{newpath} exists but is not a directory.
38498 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
38501 No access to the file or the path of the file.
38505 @var{oldpath} or @var{newpath} was too long.
38508 A directory component in @var{oldpath} or @var{newpath} does not exist.
38511 The file is on a read-only filesystem.
38514 The device containing the file has no room for the new
38518 The call was interrupted by the user.
38524 @unnumberedsubsubsec unlink
38525 @cindex unlink, file-i/o system call
38530 int unlink(const char *pathname);
38534 @samp{Funlink,@var{pathnameptr}/@var{len}}
38536 @item Return value:
38537 On success, zero is returned. On error, -1 is returned.
38543 No access to the file or the path of the file.
38546 The system does not allow unlinking of directories.
38549 The file @var{pathname} cannot be unlinked because it's
38550 being used by another process.
38553 @var{pathnameptr} is an invalid pointer value.
38556 @var{pathname} was too long.
38559 A directory component in @var{pathname} does not exist.
38562 A component of the path is not a directory.
38565 The file is on a read-only filesystem.
38568 The call was interrupted by the user.
38574 @unnumberedsubsubsec stat/fstat
38575 @cindex fstat, file-i/o system call
38576 @cindex stat, file-i/o system call
38581 int stat(const char *pathname, struct stat *buf);
38582 int fstat(int fd, struct stat *buf);
38586 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
38587 @samp{Ffstat,@var{fd},@var{bufptr}}
38589 @item Return value:
38590 On success, zero is returned. On error, -1 is returned.
38596 @var{fd} is not a valid open file.
38599 A directory component in @var{pathname} does not exist or the
38600 path is an empty string.
38603 A component of the path is not a directory.
38606 @var{pathnameptr} is an invalid pointer value.
38609 No access to the file or the path of the file.
38612 @var{pathname} was too long.
38615 The call was interrupted by the user.
38621 @unnumberedsubsubsec gettimeofday
38622 @cindex gettimeofday, file-i/o system call
38627 int gettimeofday(struct timeval *tv, void *tz);
38631 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
38633 @item Return value:
38634 On success, 0 is returned, -1 otherwise.
38640 @var{tz} is a non-NULL pointer.
38643 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
38649 @unnumberedsubsubsec isatty
38650 @cindex isatty, file-i/o system call
38655 int isatty(int fd);
38659 @samp{Fisatty,@var{fd}}
38661 @item Return value:
38662 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
38668 The call was interrupted by the user.
38673 Note that the @code{isatty} call is treated as a special case: it returns
38674 1 to the target if the file descriptor is attached
38675 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
38676 would require implementing @code{ioctl} and would be more complex than
38681 @unnumberedsubsubsec system
38682 @cindex system, file-i/o system call
38687 int system(const char *command);
38691 @samp{Fsystem,@var{commandptr}/@var{len}}
38693 @item Return value:
38694 If @var{len} is zero, the return value indicates whether a shell is
38695 available. A zero return value indicates a shell is not available.
38696 For non-zero @var{len}, the value returned is -1 on error and the
38697 return status of the command otherwise. Only the exit status of the
38698 command is returned, which is extracted from the host's @code{system}
38699 return value by calling @code{WEXITSTATUS(retval)}. In case
38700 @file{/bin/sh} could not be executed, 127 is returned.
38706 The call was interrupted by the user.
38711 @value{GDBN} takes over the full task of calling the necessary host calls
38712 to perform the @code{system} call. The return value of @code{system} on
38713 the host is simplified before it's returned
38714 to the target. Any termination signal information from the child process
38715 is discarded, and the return value consists
38716 entirely of the exit status of the called command.
38718 Due to security concerns, the @code{system} call is by default refused
38719 by @value{GDBN}. The user has to allow this call explicitly with the
38720 @code{set remote system-call-allowed 1} command.
38723 @item set remote system-call-allowed
38724 @kindex set remote system-call-allowed
38725 Control whether to allow the @code{system} calls in the File I/O
38726 protocol for the remote target. The default is zero (disabled).
38728 @item show remote system-call-allowed
38729 @kindex show remote system-call-allowed
38730 Show whether the @code{system} calls are allowed in the File I/O
38734 @node Protocol-specific Representation of Datatypes
38735 @subsection Protocol-specific Representation of Datatypes
38736 @cindex protocol-specific representation of datatypes, in file-i/o protocol
38739 * Integral Datatypes::
38741 * Memory Transfer::
38746 @node Integral Datatypes
38747 @unnumberedsubsubsec Integral Datatypes
38748 @cindex integral datatypes, in file-i/o protocol
38750 The integral datatypes used in the system calls are @code{int},
38751 @code{unsigned int}, @code{long}, @code{unsigned long},
38752 @code{mode_t}, and @code{time_t}.
38754 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
38755 implemented as 32 bit values in this protocol.
38757 @code{long} and @code{unsigned long} are implemented as 64 bit types.
38759 @xref{Limits}, for corresponding MIN and MAX values (similar to those
38760 in @file{limits.h}) to allow range checking on host and target.
38762 @code{time_t} datatypes are defined as seconds since the Epoch.
38764 All integral datatypes transferred as part of a memory read or write of a
38765 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
38768 @node Pointer Values
38769 @unnumberedsubsubsec Pointer Values
38770 @cindex pointer values, in file-i/o protocol
38772 Pointers to target data are transmitted as they are. An exception
38773 is made for pointers to buffers for which the length isn't
38774 transmitted as part of the function call, namely strings. Strings
38775 are transmitted as a pointer/length pair, both as hex values, e.g.@:
38782 which is a pointer to data of length 18 bytes at position 0x1aaf.
38783 The length is defined as the full string length in bytes, including
38784 the trailing null byte. For example, the string @code{"hello world"}
38785 at address 0x123456 is transmitted as
38791 @node Memory Transfer
38792 @unnumberedsubsubsec Memory Transfer
38793 @cindex memory transfer, in file-i/o protocol
38795 Structured data which is transferred using a memory read or write (for
38796 example, a @code{struct stat}) is expected to be in a protocol-specific format
38797 with all scalar multibyte datatypes being big endian. Translation to
38798 this representation needs to be done both by the target before the @code{F}
38799 packet is sent, and by @value{GDBN} before
38800 it transfers memory to the target. Transferred pointers to structured
38801 data should point to the already-coerced data at any time.
38805 @unnumberedsubsubsec struct stat
38806 @cindex struct stat, in file-i/o protocol
38808 The buffer of type @code{struct stat} used by the target and @value{GDBN}
38809 is defined as follows:
38813 unsigned int st_dev; /* device */
38814 unsigned int st_ino; /* inode */
38815 mode_t st_mode; /* protection */
38816 unsigned int st_nlink; /* number of hard links */
38817 unsigned int st_uid; /* user ID of owner */
38818 unsigned int st_gid; /* group ID of owner */
38819 unsigned int st_rdev; /* device type (if inode device) */
38820 unsigned long st_size; /* total size, in bytes */
38821 unsigned long st_blksize; /* blocksize for filesystem I/O */
38822 unsigned long st_blocks; /* number of blocks allocated */
38823 time_t st_atime; /* time of last access */
38824 time_t st_mtime; /* time of last modification */
38825 time_t st_ctime; /* time of last change */
38829 The integral datatypes conform to the definitions given in the
38830 appropriate section (see @ref{Integral Datatypes}, for details) so this
38831 structure is of size 64 bytes.
38833 The values of several fields have a restricted meaning and/or
38839 A value of 0 represents a file, 1 the console.
38842 No valid meaning for the target. Transmitted unchanged.
38845 Valid mode bits are described in @ref{Constants}. Any other
38846 bits have currently no meaning for the target.
38851 No valid meaning for the target. Transmitted unchanged.
38856 These values have a host and file system dependent
38857 accuracy. Especially on Windows hosts, the file system may not
38858 support exact timing values.
38861 The target gets a @code{struct stat} of the above representation and is
38862 responsible for coercing it to the target representation before
38865 Note that due to size differences between the host, target, and protocol
38866 representations of @code{struct stat} members, these members could eventually
38867 get truncated on the target.
38869 @node struct timeval
38870 @unnumberedsubsubsec struct timeval
38871 @cindex struct timeval, in file-i/o protocol
38873 The buffer of type @code{struct timeval} used by the File-I/O protocol
38874 is defined as follows:
38878 time_t tv_sec; /* second */
38879 long tv_usec; /* microsecond */
38883 The integral datatypes conform to the definitions given in the
38884 appropriate section (see @ref{Integral Datatypes}, for details) so this
38885 structure is of size 8 bytes.
38888 @subsection Constants
38889 @cindex constants, in file-i/o protocol
38891 The following values are used for the constants inside of the
38892 protocol. @value{GDBN} and target are responsible for translating these
38893 values before and after the call as needed.
38904 @unnumberedsubsubsec Open Flags
38905 @cindex open flags, in file-i/o protocol
38907 All values are given in hexadecimal representation.
38919 @node mode_t Values
38920 @unnumberedsubsubsec mode_t Values
38921 @cindex mode_t values, in file-i/o protocol
38923 All values are given in octal representation.
38940 @unnumberedsubsubsec Errno Values
38941 @cindex errno values, in file-i/o protocol
38943 All values are given in decimal representation.
38968 @code{EUNKNOWN} is used as a fallback error value if a host system returns
38969 any error value not in the list of supported error numbers.
38972 @unnumberedsubsubsec Lseek Flags
38973 @cindex lseek flags, in file-i/o protocol
38982 @unnumberedsubsubsec Limits
38983 @cindex limits, in file-i/o protocol
38985 All values are given in decimal representation.
38988 INT_MIN -2147483648
38990 UINT_MAX 4294967295
38991 LONG_MIN -9223372036854775808
38992 LONG_MAX 9223372036854775807
38993 ULONG_MAX 18446744073709551615
38996 @node File-I/O Examples
38997 @subsection File-I/O Examples
38998 @cindex file-i/o examples
39000 Example sequence of a write call, file descriptor 3, buffer is at target
39001 address 0x1234, 6 bytes should be written:
39004 <- @code{Fwrite,3,1234,6}
39005 @emph{request memory read from target}
39008 @emph{return "6 bytes written"}
39012 Example sequence of a read call, file descriptor 3, buffer is at target
39013 address 0x1234, 6 bytes should be read:
39016 <- @code{Fread,3,1234,6}
39017 @emph{request memory write to target}
39018 -> @code{X1234,6:XXXXXX}
39019 @emph{return "6 bytes read"}
39023 Example sequence of a read call, call fails on the host due to invalid
39024 file descriptor (@code{EBADF}):
39027 <- @code{Fread,3,1234,6}
39031 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39035 <- @code{Fread,3,1234,6}
39040 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39044 <- @code{Fread,3,1234,6}
39045 -> @code{X1234,6:XXXXXX}
39049 @node Library List Format
39050 @section Library List Format
39051 @cindex library list format, remote protocol
39053 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39054 same process as your application to manage libraries. In this case,
39055 @value{GDBN} can use the loader's symbol table and normal memory
39056 operations to maintain a list of shared libraries. On other
39057 platforms, the operating system manages loaded libraries.
39058 @value{GDBN} can not retrieve the list of currently loaded libraries
39059 through memory operations, so it uses the @samp{qXfer:libraries:read}
39060 packet (@pxref{qXfer library list read}) instead. The remote stub
39061 queries the target's operating system and reports which libraries
39064 The @samp{qXfer:libraries:read} packet returns an XML document which
39065 lists loaded libraries and their offsets. Each library has an
39066 associated name and one or more segment or section base addresses,
39067 which report where the library was loaded in memory.
39069 For the common case of libraries that are fully linked binaries, the
39070 library should have a list of segments. If the target supports
39071 dynamic linking of a relocatable object file, its library XML element
39072 should instead include a list of allocated sections. The segment or
39073 section bases are start addresses, not relocation offsets; they do not
39074 depend on the library's link-time base addresses.
39076 @value{GDBN} must be linked with the Expat library to support XML
39077 library lists. @xref{Expat}.
39079 A simple memory map, with one loaded library relocated by a single
39080 offset, looks like this:
39084 <library name="/lib/libc.so.6">
39085 <segment address="0x10000000"/>
39090 Another simple memory map, with one loaded library with three
39091 allocated sections (.text, .data, .bss), looks like this:
39095 <library name="sharedlib.o">
39096 <section address="0x10000000"/>
39097 <section address="0x20000000"/>
39098 <section address="0x30000000"/>
39103 The format of a library list is described by this DTD:
39106 <!-- library-list: Root element with versioning -->
39107 <!ELEMENT library-list (library)*>
39108 <!ATTLIST library-list version CDATA #FIXED "1.0">
39109 <!ELEMENT library (segment*, section*)>
39110 <!ATTLIST library name CDATA #REQUIRED>
39111 <!ELEMENT segment EMPTY>
39112 <!ATTLIST segment address CDATA #REQUIRED>
39113 <!ELEMENT section EMPTY>
39114 <!ATTLIST section address CDATA #REQUIRED>
39117 In addition, segments and section descriptors cannot be mixed within a
39118 single library element, and you must supply at least one segment or
39119 section for each library.
39121 @node Library List Format for SVR4 Targets
39122 @section Library List Format for SVR4 Targets
39123 @cindex library list format, remote protocol
39125 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39126 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39127 shared libraries. Still a special library list provided by this packet is
39128 more efficient for the @value{GDBN} remote protocol.
39130 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39131 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39132 target, the following parameters are reported:
39136 @code{name}, the absolute file name from the @code{l_name} field of
39137 @code{struct link_map}.
39139 @code{lm} with address of @code{struct link_map} used for TLS
39140 (Thread Local Storage) access.
39142 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39143 @code{struct link_map}. For prelinked libraries this is not an absolute
39144 memory address. It is a displacement of absolute memory address against
39145 address the file was prelinked to during the library load.
39147 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39150 Additionally the single @code{main-lm} attribute specifies address of
39151 @code{struct link_map} used for the main executable. This parameter is used
39152 for TLS access and its presence is optional.
39154 @value{GDBN} must be linked with the Expat library to support XML
39155 SVR4 library lists. @xref{Expat}.
39157 A simple memory map, with two loaded libraries (which do not use prelink),
39161 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39162 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39164 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39166 </library-list-svr>
39169 The format of an SVR4 library list is described by this DTD:
39172 <!-- library-list-svr4: Root element with versioning -->
39173 <!ELEMENT library-list-svr4 (library)*>
39174 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39175 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39176 <!ELEMENT library EMPTY>
39177 <!ATTLIST library name CDATA #REQUIRED>
39178 <!ATTLIST library lm CDATA #REQUIRED>
39179 <!ATTLIST library l_addr CDATA #REQUIRED>
39180 <!ATTLIST library l_ld CDATA #REQUIRED>
39183 @node Memory Map Format
39184 @section Memory Map Format
39185 @cindex memory map format
39187 To be able to write into flash memory, @value{GDBN} needs to obtain a
39188 memory map from the target. This section describes the format of the
39191 The memory map is obtained using the @samp{qXfer:memory-map:read}
39192 (@pxref{qXfer memory map read}) packet and is an XML document that
39193 lists memory regions.
39195 @value{GDBN} must be linked with the Expat library to support XML
39196 memory maps. @xref{Expat}.
39198 The top-level structure of the document is shown below:
39201 <?xml version="1.0"?>
39202 <!DOCTYPE memory-map
39203 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39204 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39210 Each region can be either:
39215 A region of RAM starting at @var{addr} and extending for @var{length}
39219 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39224 A region of read-only memory:
39227 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39232 A region of flash memory, with erasure blocks @var{blocksize}
39236 <memory type="flash" start="@var{addr}" length="@var{length}">
39237 <property name="blocksize">@var{blocksize}</property>
39243 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39244 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39245 packets to write to addresses in such ranges.
39247 The formal DTD for memory map format is given below:
39250 <!-- ................................................... -->
39251 <!-- Memory Map XML DTD ................................ -->
39252 <!-- File: memory-map.dtd .............................. -->
39253 <!-- .................................... .............. -->
39254 <!-- memory-map.dtd -->
39255 <!-- memory-map: Root element with versioning -->
39256 <!ELEMENT memory-map (memory | property)>
39257 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39258 <!ELEMENT memory (property)>
39259 <!-- memory: Specifies a memory region,
39260 and its type, or device. -->
39261 <!ATTLIST memory type CDATA #REQUIRED
39262 start CDATA #REQUIRED
39263 length CDATA #REQUIRED
39264 device CDATA #IMPLIED>
39265 <!-- property: Generic attribute tag -->
39266 <!ELEMENT property (#PCDATA | property)*>
39267 <!ATTLIST property name CDATA #REQUIRED>
39270 @node Thread List Format
39271 @section Thread List Format
39272 @cindex thread list format
39274 To efficiently update the list of threads and their attributes,
39275 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39276 (@pxref{qXfer threads read}) and obtains the XML document with
39277 the following structure:
39280 <?xml version="1.0"?>
39282 <thread id="id" core="0">
39283 ... description ...
39288 Each @samp{thread} element must have the @samp{id} attribute that
39289 identifies the thread (@pxref{thread-id syntax}). The
39290 @samp{core} attribute, if present, specifies which processor core
39291 the thread was last executing on. The content of the of @samp{thread}
39292 element is interpreted as human-readable auxilliary information.
39294 @node Traceframe Info Format
39295 @section Traceframe Info Format
39296 @cindex traceframe info format
39298 To be able to know which objects in the inferior can be examined when
39299 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39300 memory ranges, registers and trace state variables that have been
39301 collected in a traceframe.
39303 This list is obtained using the @samp{qXfer:traceframe-info:read}
39304 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39306 @value{GDBN} must be linked with the Expat library to support XML
39307 traceframe info discovery. @xref{Expat}.
39309 The top-level structure of the document is shown below:
39312 <?xml version="1.0"?>
39313 <!DOCTYPE traceframe-info
39314 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39315 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39321 Each traceframe block can be either:
39326 A region of collected memory starting at @var{addr} and extending for
39327 @var{length} bytes from there:
39330 <memory start="@var{addr}" length="@var{length}"/>
39334 A block indicating trace state variable numbered @var{number} has been
39338 <tvar id="@var{number}"/>
39343 The formal DTD for the traceframe info format is given below:
39346 <!ELEMENT traceframe-info (memory | tvar)* >
39347 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39349 <!ELEMENT memory EMPTY>
39350 <!ATTLIST memory start CDATA #REQUIRED
39351 length CDATA #REQUIRED>
39353 <!ATTLIST tvar id CDATA #REQUIRED>
39356 @node Branch Trace Format
39357 @section Branch Trace Format
39358 @cindex branch trace format
39360 In order to display the branch trace of an inferior thread,
39361 @value{GDBN} needs to obtain the list of branches. This list is
39362 represented as list of sequential code blocks that are connected via
39363 branches. The code in each block has been executed sequentially.
39365 This list is obtained using the @samp{qXfer:btrace:read}
39366 (@pxref{qXfer btrace read}) packet and is an XML document.
39368 @value{GDBN} must be linked with the Expat library to support XML
39369 traceframe info discovery. @xref{Expat}.
39371 The top-level structure of the document is shown below:
39374 <?xml version="1.0"?>
39376 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
39377 "http://sourceware.org/gdb/gdb-btrace.dtd">
39386 A block of sequentially executed instructions starting at @var{begin}
39387 and ending at @var{end}:
39390 <block begin="@var{begin}" end="@var{end}"/>
39395 The formal DTD for the branch trace format is given below:
39398 <!ELEMENT btrace (block)* >
39399 <!ATTLIST btrace version CDATA #FIXED "1.0">
39401 <!ELEMENT block EMPTY>
39402 <!ATTLIST block begin CDATA #REQUIRED
39403 end CDATA #REQUIRED>
39406 @node Branch Trace Configuration Format
39407 @section Branch Trace Configuration Format
39408 @cindex branch trace configuration format
39410 For each inferior thread, @value{GDBN} can obtain the branch trace
39411 configuration using the @samp{qXfer:btrace-conf:read}
39412 (@pxref{qXfer btrace-conf read}) packet.
39414 The configuration describes the branch trace format and configuration
39415 settings for that format. The following information is described:
39419 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
39422 The size of the @acronym{BTS} ring buffer in bytes.
39426 @value{GDBN} must be linked with the Expat library to support XML
39427 branch trace configuration discovery. @xref{Expat}.
39429 The formal DTD for the branch trace configuration format is given below:
39432 <!ELEMENT btrace-conf (bts?)>
39433 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
39435 <!ELEMENT bts EMPTY>
39436 <!ATTLIST bts size CDATA #IMPLIED>
39439 @include agentexpr.texi
39441 @node Target Descriptions
39442 @appendix Target Descriptions
39443 @cindex target descriptions
39445 One of the challenges of using @value{GDBN} to debug embedded systems
39446 is that there are so many minor variants of each processor
39447 architecture in use. It is common practice for vendors to start with
39448 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
39449 and then make changes to adapt it to a particular market niche. Some
39450 architectures have hundreds of variants, available from dozens of
39451 vendors. This leads to a number of problems:
39455 With so many different customized processors, it is difficult for
39456 the @value{GDBN} maintainers to keep up with the changes.
39458 Since individual variants may have short lifetimes or limited
39459 audiences, it may not be worthwhile to carry information about every
39460 variant in the @value{GDBN} source tree.
39462 When @value{GDBN} does support the architecture of the embedded system
39463 at hand, the task of finding the correct architecture name to give the
39464 @command{set architecture} command can be error-prone.
39467 To address these problems, the @value{GDBN} remote protocol allows a
39468 target system to not only identify itself to @value{GDBN}, but to
39469 actually describe its own features. This lets @value{GDBN} support
39470 processor variants it has never seen before --- to the extent that the
39471 descriptions are accurate, and that @value{GDBN} understands them.
39473 @value{GDBN} must be linked with the Expat library to support XML
39474 target descriptions. @xref{Expat}.
39477 * Retrieving Descriptions:: How descriptions are fetched from a target.
39478 * Target Description Format:: The contents of a target description.
39479 * Predefined Target Types:: Standard types available for target
39481 * Standard Target Features:: Features @value{GDBN} knows about.
39484 @node Retrieving Descriptions
39485 @section Retrieving Descriptions
39487 Target descriptions can be read from the target automatically, or
39488 specified by the user manually. The default behavior is to read the
39489 description from the target. @value{GDBN} retrieves it via the remote
39490 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
39491 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
39492 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
39493 XML document, of the form described in @ref{Target Description
39496 Alternatively, you can specify a file to read for the target description.
39497 If a file is set, the target will not be queried. The commands to
39498 specify a file are:
39501 @cindex set tdesc filename
39502 @item set tdesc filename @var{path}
39503 Read the target description from @var{path}.
39505 @cindex unset tdesc filename
39506 @item unset tdesc filename
39507 Do not read the XML target description from a file. @value{GDBN}
39508 will use the description supplied by the current target.
39510 @cindex show tdesc filename
39511 @item show tdesc filename
39512 Show the filename to read for a target description, if any.
39516 @node Target Description Format
39517 @section Target Description Format
39518 @cindex target descriptions, XML format
39520 A target description annex is an @uref{http://www.w3.org/XML/, XML}
39521 document which complies with the Document Type Definition provided in
39522 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
39523 means you can use generally available tools like @command{xmllint} to
39524 check that your feature descriptions are well-formed and valid.
39525 However, to help people unfamiliar with XML write descriptions for
39526 their targets, we also describe the grammar here.
39528 Target descriptions can identify the architecture of the remote target
39529 and (for some architectures) provide information about custom register
39530 sets. They can also identify the OS ABI of the remote target.
39531 @value{GDBN} can use this information to autoconfigure for your
39532 target, or to warn you if you connect to an unsupported target.
39534 Here is a simple target description:
39537 <target version="1.0">
39538 <architecture>i386:x86-64</architecture>
39543 This minimal description only says that the target uses
39544 the x86-64 architecture.
39546 A target description has the following overall form, with [ ] marking
39547 optional elements and @dots{} marking repeatable elements. The elements
39548 are explained further below.
39551 <?xml version="1.0"?>
39552 <!DOCTYPE target SYSTEM "gdb-target.dtd">
39553 <target version="1.0">
39554 @r{[}@var{architecture}@r{]}
39555 @r{[}@var{osabi}@r{]}
39556 @r{[}@var{compatible}@r{]}
39557 @r{[}@var{feature}@dots{}@r{]}
39562 The description is generally insensitive to whitespace and line
39563 breaks, under the usual common-sense rules. The XML version
39564 declaration and document type declaration can generally be omitted
39565 (@value{GDBN} does not require them), but specifying them may be
39566 useful for XML validation tools. The @samp{version} attribute for
39567 @samp{<target>} may also be omitted, but we recommend
39568 including it; if future versions of @value{GDBN} use an incompatible
39569 revision of @file{gdb-target.dtd}, they will detect and report
39570 the version mismatch.
39572 @subsection Inclusion
39573 @cindex target descriptions, inclusion
39576 @cindex <xi:include>
39579 It can sometimes be valuable to split a target description up into
39580 several different annexes, either for organizational purposes, or to
39581 share files between different possible target descriptions. You can
39582 divide a description into multiple files by replacing any element of
39583 the target description with an inclusion directive of the form:
39586 <xi:include href="@var{document}"/>
39590 When @value{GDBN} encounters an element of this form, it will retrieve
39591 the named XML @var{document}, and replace the inclusion directive with
39592 the contents of that document. If the current description was read
39593 using @samp{qXfer}, then so will be the included document;
39594 @var{document} will be interpreted as the name of an annex. If the
39595 current description was read from a file, @value{GDBN} will look for
39596 @var{document} as a file in the same directory where it found the
39597 original description.
39599 @subsection Architecture
39600 @cindex <architecture>
39602 An @samp{<architecture>} element has this form:
39605 <architecture>@var{arch}</architecture>
39608 @var{arch} is one of the architectures from the set accepted by
39609 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39612 @cindex @code{<osabi>}
39614 This optional field was introduced in @value{GDBN} version 7.0.
39615 Previous versions of @value{GDBN} ignore it.
39617 An @samp{<osabi>} element has this form:
39620 <osabi>@var{abi-name}</osabi>
39623 @var{abi-name} is an OS ABI name from the same selection accepted by
39624 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
39626 @subsection Compatible Architecture
39627 @cindex @code{<compatible>}
39629 This optional field was introduced in @value{GDBN} version 7.0.
39630 Previous versions of @value{GDBN} ignore it.
39632 A @samp{<compatible>} element has this form:
39635 <compatible>@var{arch}</compatible>
39638 @var{arch} is one of the architectures from the set accepted by
39639 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
39641 A @samp{<compatible>} element is used to specify that the target
39642 is able to run binaries in some other than the main target architecture
39643 given by the @samp{<architecture>} element. For example, on the
39644 Cell Broadband Engine, the main architecture is @code{powerpc:common}
39645 or @code{powerpc:common64}, but the system is able to run binaries
39646 in the @code{spu} architecture as well. The way to describe this
39647 capability with @samp{<compatible>} is as follows:
39650 <architecture>powerpc:common</architecture>
39651 <compatible>spu</compatible>
39654 @subsection Features
39657 Each @samp{<feature>} describes some logical portion of the target
39658 system. Features are currently used to describe available CPU
39659 registers and the types of their contents. A @samp{<feature>} element
39663 <feature name="@var{name}">
39664 @r{[}@var{type}@dots{}@r{]}
39670 Each feature's name should be unique within the description. The name
39671 of a feature does not matter unless @value{GDBN} has some special
39672 knowledge of the contents of that feature; if it does, the feature
39673 should have its standard name. @xref{Standard Target Features}.
39677 Any register's value is a collection of bits which @value{GDBN} must
39678 interpret. The default interpretation is a two's complement integer,
39679 but other types can be requested by name in the register description.
39680 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
39681 Target Types}), and the description can define additional composite types.
39683 Each type element must have an @samp{id} attribute, which gives
39684 a unique (within the containing @samp{<feature>}) name to the type.
39685 Types must be defined before they are used.
39688 Some targets offer vector registers, which can be treated as arrays
39689 of scalar elements. These types are written as @samp{<vector>} elements,
39690 specifying the array element type, @var{type}, and the number of elements,
39694 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
39698 If a register's value is usefully viewed in multiple ways, define it
39699 with a union type containing the useful representations. The
39700 @samp{<union>} element contains one or more @samp{<field>} elements,
39701 each of which has a @var{name} and a @var{type}:
39704 <union id="@var{id}">
39705 <field name="@var{name}" type="@var{type}"/>
39711 If a register's value is composed from several separate values, define
39712 it with a structure type. There are two forms of the @samp{<struct>}
39713 element; a @samp{<struct>} element must either contain only bitfields
39714 or contain no bitfields. If the structure contains only bitfields,
39715 its total size in bytes must be specified, each bitfield must have an
39716 explicit start and end, and bitfields are automatically assigned an
39717 integer type. The field's @var{start} should be less than or
39718 equal to its @var{end}, and zero represents the least significant bit.
39721 <struct id="@var{id}" size="@var{size}">
39722 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39727 If the structure contains no bitfields, then each field has an
39728 explicit type, and no implicit padding is added.
39731 <struct id="@var{id}">
39732 <field name="@var{name}" type="@var{type}"/>
39738 If a register's value is a series of single-bit flags, define it with
39739 a flags type. The @samp{<flags>} element has an explicit @var{size}
39740 and contains one or more @samp{<field>} elements. Each field has a
39741 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
39745 <flags id="@var{id}" size="@var{size}">
39746 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
39751 @subsection Registers
39754 Each register is represented as an element with this form:
39757 <reg name="@var{name}"
39758 bitsize="@var{size}"
39759 @r{[}regnum="@var{num}"@r{]}
39760 @r{[}save-restore="@var{save-restore}"@r{]}
39761 @r{[}type="@var{type}"@r{]}
39762 @r{[}group="@var{group}"@r{]}/>
39766 The components are as follows:
39771 The register's name; it must be unique within the target description.
39774 The register's size, in bits.
39777 The register's number. If omitted, a register's number is one greater
39778 than that of the previous register (either in the current feature or in
39779 a preceding feature); the first register in the target description
39780 defaults to zero. This register number is used to read or write
39781 the register; e.g.@: it is used in the remote @code{p} and @code{P}
39782 packets, and registers appear in the @code{g} and @code{G} packets
39783 in order of increasing register number.
39786 Whether the register should be preserved across inferior function
39787 calls; this must be either @code{yes} or @code{no}. The default is
39788 @code{yes}, which is appropriate for most registers except for
39789 some system control registers; this is not related to the target's
39793 The type of the register. It may be a predefined type, a type
39794 defined in the current feature, or one of the special types @code{int}
39795 and @code{float}. @code{int} is an integer type of the correct size
39796 for @var{bitsize}, and @code{float} is a floating point type (in the
39797 architecture's normal floating point format) of the correct size for
39798 @var{bitsize}. The default is @code{int}.
39801 The register group to which this register belongs. It must
39802 be either @code{general}, @code{float}, or @code{vector}. If no
39803 @var{group} is specified, @value{GDBN} will not display the register
39804 in @code{info registers}.
39808 @node Predefined Target Types
39809 @section Predefined Target Types
39810 @cindex target descriptions, predefined types
39812 Type definitions in the self-description can build up composite types
39813 from basic building blocks, but can not define fundamental types. Instead,
39814 standard identifiers are provided by @value{GDBN} for the fundamental
39815 types. The currently supported types are:
39824 Signed integer types holding the specified number of bits.
39831 Unsigned integer types holding the specified number of bits.
39835 Pointers to unspecified code and data. The program counter and
39836 any dedicated return address register may be marked as code
39837 pointers; printing a code pointer converts it into a symbolic
39838 address. The stack pointer and any dedicated address registers
39839 may be marked as data pointers.
39842 Single precision IEEE floating point.
39845 Double precision IEEE floating point.
39848 The 12-byte extended precision format used by ARM FPA registers.
39851 The 10-byte extended precision format used by x87 registers.
39854 32bit @sc{eflags} register used by x86.
39857 32bit @sc{mxcsr} register used by x86.
39861 @node Standard Target Features
39862 @section Standard Target Features
39863 @cindex target descriptions, standard features
39865 A target description must contain either no registers or all the
39866 target's registers. If the description contains no registers, then
39867 @value{GDBN} will assume a default register layout, selected based on
39868 the architecture. If the description contains any registers, the
39869 default layout will not be used; the standard registers must be
39870 described in the target description, in such a way that @value{GDBN}
39871 can recognize them.
39873 This is accomplished by giving specific names to feature elements
39874 which contain standard registers. @value{GDBN} will look for features
39875 with those names and verify that they contain the expected registers;
39876 if any known feature is missing required registers, or if any required
39877 feature is missing, @value{GDBN} will reject the target
39878 description. You can add additional registers to any of the
39879 standard features --- @value{GDBN} will display them just as if
39880 they were added to an unrecognized feature.
39882 This section lists the known features and their expected contents.
39883 Sample XML documents for these features are included in the
39884 @value{GDBN} source tree, in the directory @file{gdb/features}.
39886 Names recognized by @value{GDBN} should include the name of the
39887 company or organization which selected the name, and the overall
39888 architecture to which the feature applies; so e.g.@: the feature
39889 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
39891 The names of registers are not case sensitive for the purpose
39892 of recognizing standard features, but @value{GDBN} will only display
39893 registers using the capitalization used in the description.
39896 * AArch64 Features::
39899 * MicroBlaze Features::
39902 * Nios II Features::
39903 * PowerPC Features::
39904 * S/390 and System z Features::
39909 @node AArch64 Features
39910 @subsection AArch64 Features
39911 @cindex target descriptions, AArch64 features
39913 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
39914 targets. It should contain registers @samp{x0} through @samp{x30},
39915 @samp{sp}, @samp{pc}, and @samp{cpsr}.
39917 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
39918 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
39922 @subsection ARM Features
39923 @cindex target descriptions, ARM features
39925 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
39927 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
39928 @samp{lr}, @samp{pc}, and @samp{cpsr}.
39930 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
39931 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
39932 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
39935 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
39936 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
39938 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
39939 it should contain at least registers @samp{wR0} through @samp{wR15} and
39940 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
39941 @samp{wCSSF}, and @samp{wCASF} registers are optional.
39943 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
39944 should contain at least registers @samp{d0} through @samp{d15}. If
39945 they are present, @samp{d16} through @samp{d31} should also be included.
39946 @value{GDBN} will synthesize the single-precision registers from
39947 halves of the double-precision registers.
39949 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
39950 need to contain registers; it instructs @value{GDBN} to display the
39951 VFP double-precision registers as vectors and to synthesize the
39952 quad-precision registers from pairs of double-precision registers.
39953 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
39954 be present and include 32 double-precision registers.
39956 @node i386 Features
39957 @subsection i386 Features
39958 @cindex target descriptions, i386 features
39960 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
39961 targets. It should describe the following registers:
39965 @samp{eax} through @samp{edi} plus @samp{eip} for i386
39967 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
39969 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
39970 @samp{fs}, @samp{gs}
39972 @samp{st0} through @samp{st7}
39974 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
39975 @samp{foseg}, @samp{fooff} and @samp{fop}
39978 The register sets may be different, depending on the target.
39980 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
39981 describe registers:
39985 @samp{xmm0} through @samp{xmm7} for i386
39987 @samp{xmm0} through @samp{xmm15} for amd64
39992 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
39993 @samp{org.gnu.gdb.i386.sse} feature. It should
39994 describe the upper 128 bits of @sc{ymm} registers:
39998 @samp{ymm0h} through @samp{ymm7h} for i386
40000 @samp{ymm0h} through @samp{ymm15h} for amd64
40003 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
40004 Memory Protection Extension (MPX). It should describe the following registers:
40008 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
40010 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
40013 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40014 describe a single register, @samp{orig_eax}.
40016 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
40017 @samp{org.gnu.gdb.i386.avx} feature. It should
40018 describe additional @sc{xmm} registers:
40022 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
40025 It should describe the upper 128 bits of additional @sc{ymm} registers:
40029 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
40033 describe the upper 256 bits of @sc{zmm} registers:
40037 @samp{zmm0h} through @samp{zmm7h} for i386.
40039 @samp{zmm0h} through @samp{zmm15h} for amd64.
40043 describe the additional @sc{zmm} registers:
40047 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
40050 @node MicroBlaze Features
40051 @subsection MicroBlaze Features
40052 @cindex target descriptions, MicroBlaze features
40054 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
40055 targets. It should contain registers @samp{r0} through @samp{r31},
40056 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
40057 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
40058 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
40060 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
40061 If present, it should contain registers @samp{rshr} and @samp{rslr}
40063 @node MIPS Features
40064 @subsection @acronym{MIPS} Features
40065 @cindex target descriptions, @acronym{MIPS} features
40067 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40068 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40069 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40072 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40073 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40074 registers. They may be 32-bit or 64-bit depending on the target.
40076 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40077 it may be optional in a future version of @value{GDBN}. It should
40078 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40079 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40081 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40082 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40083 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40084 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40086 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40087 contain a single register, @samp{restart}, which is used by the
40088 Linux kernel to control restartable syscalls.
40090 @node M68K Features
40091 @subsection M68K Features
40092 @cindex target descriptions, M68K features
40095 @item @samp{org.gnu.gdb.m68k.core}
40096 @itemx @samp{org.gnu.gdb.coldfire.core}
40097 @itemx @samp{org.gnu.gdb.fido.core}
40098 One of those features must be always present.
40099 The feature that is present determines which flavor of m68k is
40100 used. The feature that is present should contain registers
40101 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40102 @samp{sp}, @samp{ps} and @samp{pc}.
40104 @item @samp{org.gnu.gdb.coldfire.fp}
40105 This feature is optional. If present, it should contain registers
40106 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40110 @node Nios II Features
40111 @subsection Nios II Features
40112 @cindex target descriptions, Nios II features
40114 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
40115 targets. It should contain the 32 core registers (@samp{zero},
40116 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
40117 @samp{pc}, and the 16 control registers (@samp{status} through
40120 @node PowerPC Features
40121 @subsection PowerPC Features
40122 @cindex target descriptions, PowerPC features
40124 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40125 targets. It should contain registers @samp{r0} through @samp{r31},
40126 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40127 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40129 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40130 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40132 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40133 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40136 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40137 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40138 will combine these registers with the floating point registers
40139 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40140 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40141 through @samp{vs63}, the set of vector registers for POWER7.
40143 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40144 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40145 @samp{spefscr}. SPE targets should provide 32-bit registers in
40146 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40147 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40148 these to present registers @samp{ev0} through @samp{ev31} to the
40151 @node S/390 and System z Features
40152 @subsection S/390 and System z Features
40153 @cindex target descriptions, S/390 features
40154 @cindex target descriptions, System z features
40156 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
40157 System z targets. It should contain the PSW and the 16 general
40158 registers. In particular, System z targets should provide the 64-bit
40159 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
40160 S/390 targets should provide the 32-bit versions of these registers.
40161 A System z target that runs in 31-bit addressing mode should provide
40162 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
40163 register's upper halves @samp{r0h} through @samp{r15h}, and their
40164 lower halves @samp{r0l} through @samp{r15l}.
40166 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
40167 contain the 64-bit registers @samp{f0} through @samp{f15}, and
40170 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
40171 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
40173 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
40174 contain the register @samp{orig_r2}, which is 64-bit wide on System z
40175 targets and 32-bit otherwise. In addition, the feature may contain
40176 the @samp{last_break} register, whose width depends on the addressing
40177 mode, as well as the @samp{system_call} register, which is always
40180 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
40181 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
40182 @samp{atia}, and @samp{tr0} through @samp{tr15}.
40184 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
40185 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
40186 combined by @value{GDBN} with the floating point registers @samp{f0}
40187 through @samp{f15} to present the 128-bit wide vector registers
40188 @samp{v0} through @samp{v15}. In addition, this feature should
40189 contain the 128-bit wide vector registers @samp{v16} through
40192 @node TIC6x Features
40193 @subsection TMS320C6x Features
40194 @cindex target descriptions, TIC6x features
40195 @cindex target descriptions, TMS320C6x features
40196 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40197 targets. It should contain registers @samp{A0} through @samp{A15},
40198 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40200 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40201 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40202 through @samp{B31}.
40204 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40205 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40207 @node Operating System Information
40208 @appendix Operating System Information
40209 @cindex operating system information
40215 Users of @value{GDBN} often wish to obtain information about the state of
40216 the operating system running on the target---for example the list of
40217 processes, or the list of open files. This section describes the
40218 mechanism that makes it possible. This mechanism is similar to the
40219 target features mechanism (@pxref{Target Descriptions}), but focuses
40220 on a different aspect of target.
40222 Operating system information is retrived from the target via the
40223 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40224 read}). The object name in the request should be @samp{osdata}, and
40225 the @var{annex} identifies the data to be fetched.
40228 @appendixsection Process list
40229 @cindex operating system information, process list
40231 When requesting the process list, the @var{annex} field in the
40232 @samp{qXfer} request should be @samp{processes}. The returned data is
40233 an XML document. The formal syntax of this document is defined in
40234 @file{gdb/features/osdata.dtd}.
40236 An example document is:
40239 <?xml version="1.0"?>
40240 <!DOCTYPE target SYSTEM "osdata.dtd">
40241 <osdata type="processes">
40243 <column name="pid">1</column>
40244 <column name="user">root</column>
40245 <column name="command">/sbin/init</column>
40246 <column name="cores">1,2,3</column>
40251 Each item should include a column whose name is @samp{pid}. The value
40252 of that column should identify the process on the target. The
40253 @samp{user} and @samp{command} columns are optional, and will be
40254 displayed by @value{GDBN}. The @samp{cores} column, if present,
40255 should contain a comma-separated list of cores that this process
40256 is running on. Target may provide additional columns,
40257 which @value{GDBN} currently ignores.
40259 @node Trace File Format
40260 @appendix Trace File Format
40261 @cindex trace file format
40263 The trace file comes in three parts: a header, a textual description
40264 section, and a trace frame section with binary data.
40266 The header has the form @code{\x7fTRACE0\n}. The first byte is
40267 @code{0x7f} so as to indicate that the file contains binary data,
40268 while the @code{0} is a version number that may have different values
40271 The description section consists of multiple lines of @sc{ascii} text
40272 separated by newline characters (@code{0xa}). The lines may include a
40273 variety of optional descriptive or context-setting information, such
40274 as tracepoint definitions or register set size. @value{GDBN} will
40275 ignore any line that it does not recognize. An empty line marks the end
40278 @c FIXME add some specific types of data
40280 The trace frame section consists of a number of consecutive frames.
40281 Each frame begins with a two-byte tracepoint number, followed by a
40282 four-byte size giving the amount of data in the frame. The data in
40283 the frame consists of a number of blocks, each introduced by a
40284 character indicating its type (at least register, memory, and trace
40285 state variable). The data in this section is raw binary, not a
40286 hexadecimal or other encoding; its endianness matches the target's
40289 @c FIXME bi-arch may require endianness/arch info in description section
40292 @item R @var{bytes}
40293 Register block. The number and ordering of bytes matches that of a
40294 @code{g} packet in the remote protocol. Note that these are the
40295 actual bytes, in target order and @value{GDBN} register order, not a
40296 hexadecimal encoding.
40298 @item M @var{address} @var{length} @var{bytes}...
40299 Memory block. This is a contiguous block of memory, at the 8-byte
40300 address @var{address}, with a 2-byte length @var{length}, followed by
40301 @var{length} bytes.
40303 @item V @var{number} @var{value}
40304 Trace state variable block. This records the 8-byte signed value
40305 @var{value} of trace state variable numbered @var{number}.
40309 Future enhancements of the trace file format may include additional types
40312 @node Index Section Format
40313 @appendix @code{.gdb_index} section format
40314 @cindex .gdb_index section format
40315 @cindex index section format
40317 This section documents the index section that is created by @code{save
40318 gdb-index} (@pxref{Index Files}). The index section is
40319 DWARF-specific; some knowledge of DWARF is assumed in this
40322 The mapped index file format is designed to be directly
40323 @code{mmap}able on any architecture. In most cases, a datum is
40324 represented using a little-endian 32-bit integer value, called an
40325 @code{offset_type}. Big endian machines must byte-swap the values
40326 before using them. Exceptions to this rule are noted. The data is
40327 laid out such that alignment is always respected.
40329 A mapped index consists of several areas, laid out in order.
40333 The file header. This is a sequence of values, of @code{offset_type}
40334 unless otherwise noted:
40338 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
40339 Version 4 uses a different hashing function from versions 5 and 6.
40340 Version 6 includes symbols for inlined functions, whereas versions 4
40341 and 5 do not. Version 7 adds attributes to the CU indices in the
40342 symbol table. Version 8 specifies that symbols from DWARF type units
40343 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
40344 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
40346 @value{GDBN} will only read version 4, 5, or 6 indices
40347 by specifying @code{set use-deprecated-index-sections on}.
40348 GDB has a workaround for potentially broken version 7 indices so it is
40349 currently not flagged as deprecated.
40352 The offset, from the start of the file, of the CU list.
40355 The offset, from the start of the file, of the types CU list. Note
40356 that this area can be empty, in which case this offset will be equal
40357 to the next offset.
40360 The offset, from the start of the file, of the address area.
40363 The offset, from the start of the file, of the symbol table.
40366 The offset, from the start of the file, of the constant pool.
40370 The CU list. This is a sequence of pairs of 64-bit little-endian
40371 values, sorted by the CU offset. The first element in each pair is
40372 the offset of a CU in the @code{.debug_info} section. The second
40373 element in each pair is the length of that CU. References to a CU
40374 elsewhere in the map are done using a CU index, which is just the
40375 0-based index into this table. Note that if there are type CUs, then
40376 conceptually CUs and type CUs form a single list for the purposes of
40380 The types CU list. This is a sequence of triplets of 64-bit
40381 little-endian values. In a triplet, the first value is the CU offset,
40382 the second value is the type offset in the CU, and the third value is
40383 the type signature. The types CU list is not sorted.
40386 The address area. The address area consists of a sequence of address
40387 entries. Each address entry has three elements:
40391 The low address. This is a 64-bit little-endian value.
40394 The high address. This is a 64-bit little-endian value. Like
40395 @code{DW_AT_high_pc}, the value is one byte beyond the end.
40398 The CU index. This is an @code{offset_type} value.
40402 The symbol table. This is an open-addressed hash table. The size of
40403 the hash table is always a power of 2.
40405 Each slot in the hash table consists of a pair of @code{offset_type}
40406 values. The first value is the offset of the symbol's name in the
40407 constant pool. The second value is the offset of the CU vector in the
40410 If both values are 0, then this slot in the hash table is empty. This
40411 is ok because while 0 is a valid constant pool index, it cannot be a
40412 valid index for both a string and a CU vector.
40414 The hash value for a table entry is computed by applying an
40415 iterative hash function to the symbol's name. Starting with an
40416 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
40417 the string is incorporated into the hash using the formula depending on the
40422 The formula is @code{r = r * 67 + c - 113}.
40424 @item Versions 5 to 7
40425 The formula is @code{r = r * 67 + tolower (c) - 113}.
40428 The terminating @samp{\0} is not incorporated into the hash.
40430 The step size used in the hash table is computed via
40431 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
40432 value, and @samp{size} is the size of the hash table. The step size
40433 is used to find the next candidate slot when handling a hash
40436 The names of C@t{++} symbols in the hash table are canonicalized. We
40437 don't currently have a simple description of the canonicalization
40438 algorithm; if you intend to create new index sections, you must read
40442 The constant pool. This is simply a bunch of bytes. It is organized
40443 so that alignment is correct: CU vectors are stored first, followed by
40446 A CU vector in the constant pool is a sequence of @code{offset_type}
40447 values. The first value is the number of CU indices in the vector.
40448 Each subsequent value is the index and symbol attributes of a CU in
40449 the CU list. This element in the hash table is used to indicate which
40450 CUs define the symbol and how the symbol is used.
40451 See below for the format of each CU index+attributes entry.
40453 A string in the constant pool is zero-terminated.
40456 Attributes were added to CU index values in @code{.gdb_index} version 7.
40457 If a symbol has multiple uses within a CU then there is one
40458 CU index+attributes value for each use.
40460 The format of each CU index+attributes entry is as follows
40466 This is the index of the CU in the CU list.
40468 These bits are reserved for future purposes and must be zero.
40470 The kind of the symbol in the CU.
40474 This value is reserved and should not be used.
40475 By reserving zero the full @code{offset_type} value is backwards compatible
40476 with previous versions of the index.
40478 The symbol is a type.
40480 The symbol is a variable or an enum value.
40482 The symbol is a function.
40484 Any other kind of symbol.
40486 These values are reserved.
40490 This bit is zero if the value is global and one if it is static.
40492 The determination of whether a symbol is global or static is complicated.
40493 The authorative reference is the file @file{dwarf2read.c} in
40494 @value{GDBN} sources.
40498 This pseudo-code describes the computation of a symbol's kind and
40499 global/static attributes in the index.
40502 is_external = get_attribute (die, DW_AT_external);
40503 language = get_attribute (cu_die, DW_AT_language);
40506 case DW_TAG_typedef:
40507 case DW_TAG_base_type:
40508 case DW_TAG_subrange_type:
40512 case DW_TAG_enumerator:
40514 is_static = (language != CPLUS && language != JAVA);
40516 case DW_TAG_subprogram:
40518 is_static = ! (is_external || language == ADA);
40520 case DW_TAG_constant:
40522 is_static = ! is_external;
40524 case DW_TAG_variable:
40526 is_static = ! is_external;
40528 case DW_TAG_namespace:
40532 case DW_TAG_class_type:
40533 case DW_TAG_interface_type:
40534 case DW_TAG_structure_type:
40535 case DW_TAG_union_type:
40536 case DW_TAG_enumeration_type:
40538 is_static = (language != CPLUS && language != JAVA);
40546 @appendix Manual pages
40550 * gdb man:: The GNU Debugger man page
40551 * gdbserver man:: Remote Server for the GNU Debugger man page
40552 * gcore man:: Generate a core file of a running program
40553 * gdbinit man:: gdbinit scripts
40559 @c man title gdb The GNU Debugger
40561 @c man begin SYNOPSIS gdb
40562 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
40563 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
40564 [@option{-b}@w{ }@var{bps}]
40565 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
40566 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
40567 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
40568 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
40569 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
40572 @c man begin DESCRIPTION gdb
40573 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
40574 going on ``inside'' another program while it executes -- or what another
40575 program was doing at the moment it crashed.
40577 @value{GDBN} can do four main kinds of things (plus other things in support of
40578 these) to help you catch bugs in the act:
40582 Start your program, specifying anything that might affect its behavior.
40585 Make your program stop on specified conditions.
40588 Examine what has happened, when your program has stopped.
40591 Change things in your program, so you can experiment with correcting the
40592 effects of one bug and go on to learn about another.
40595 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
40598 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
40599 commands from the terminal until you tell it to exit with the @value{GDBN}
40600 command @code{quit}. You can get online help from @value{GDBN} itself
40601 by using the command @code{help}.
40603 You can run @code{gdb} with no arguments or options; but the most
40604 usual way to start @value{GDBN} is with one argument or two, specifying an
40605 executable program as the argument:
40611 You can also start with both an executable program and a core file specified:
40617 You can, instead, specify a process ID as a second argument, if you want
40618 to debug a running process:
40626 would attach @value{GDBN} to process @code{1234} (unless you also have a file
40627 named @file{1234}; @value{GDBN} does check for a core file first).
40628 With option @option{-p} you can omit the @var{program} filename.
40630 Here are some of the most frequently needed @value{GDBN} commands:
40632 @c pod2man highlights the right hand side of the @item lines.
40634 @item break [@var{file}:]@var{functiop}
40635 Set a breakpoint at @var{function} (in @var{file}).
40637 @item run [@var{arglist}]
40638 Start your program (with @var{arglist}, if specified).
40641 Backtrace: display the program stack.
40643 @item print @var{expr}
40644 Display the value of an expression.
40647 Continue running your program (after stopping, e.g. at a breakpoint).
40650 Execute next program line (after stopping); step @emph{over} any
40651 function calls in the line.
40653 @item edit [@var{file}:]@var{function}
40654 look at the program line where it is presently stopped.
40656 @item list [@var{file}:]@var{function}
40657 type the text of the program in the vicinity of where it is presently stopped.
40660 Execute next program line (after stopping); step @emph{into} any
40661 function calls in the line.
40663 @item help [@var{name}]
40664 Show information about @value{GDBN} command @var{name}, or general information
40665 about using @value{GDBN}.
40668 Exit from @value{GDBN}.
40672 For full details on @value{GDBN},
40673 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40674 by Richard M. Stallman and Roland H. Pesch. The same text is available online
40675 as the @code{gdb} entry in the @code{info} program.
40679 @c man begin OPTIONS gdb
40680 Any arguments other than options specify an executable
40681 file and core file (or process ID); that is, the first argument
40682 encountered with no
40683 associated option flag is equivalent to a @option{-se} option, and the second,
40684 if any, is equivalent to a @option{-c} option if it's the name of a file.
40686 both long and short forms; both are shown here. The long forms are also
40687 recognized if you truncate them, so long as enough of the option is
40688 present to be unambiguous. (If you prefer, you can flag option
40689 arguments with @option{+} rather than @option{-}, though we illustrate the
40690 more usual convention.)
40692 All the options and command line arguments you give are processed
40693 in sequential order. The order makes a difference when the @option{-x}
40699 List all options, with brief explanations.
40701 @item -symbols=@var{file}
40702 @itemx -s @var{file}
40703 Read symbol table from file @var{file}.
40706 Enable writing into executable and core files.
40708 @item -exec=@var{file}
40709 @itemx -e @var{file}
40710 Use file @var{file} as the executable file to execute when
40711 appropriate, and for examining pure data in conjunction with a core
40714 @item -se=@var{file}
40715 Read symbol table from file @var{file} and use it as the executable
40718 @item -core=@var{file}
40719 @itemx -c @var{file}
40720 Use file @var{file} as a core dump to examine.
40722 @item -command=@var{file}
40723 @itemx -x @var{file}
40724 Execute @value{GDBN} commands from file @var{file}.
40726 @item -ex @var{command}
40727 Execute given @value{GDBN} @var{command}.
40729 @item -directory=@var{directory}
40730 @itemx -d @var{directory}
40731 Add @var{directory} to the path to search for source files.
40734 Do not execute commands from @file{~/.gdbinit}.
40738 Do not execute commands from any @file{.gdbinit} initialization files.
40742 ``Quiet''. Do not print the introductory and copyright messages. These
40743 messages are also suppressed in batch mode.
40746 Run in batch mode. Exit with status @code{0} after processing all the command
40747 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
40748 Exit with nonzero status if an error occurs in executing the @value{GDBN}
40749 commands in the command files.
40751 Batch mode may be useful for running @value{GDBN} as a filter, for example to
40752 download and run a program on another computer; in order to make this
40753 more useful, the message
40756 Program exited normally.
40760 (which is ordinarily issued whenever a program running under @value{GDBN} control
40761 terminates) is not issued when running in batch mode.
40763 @item -cd=@var{directory}
40764 Run @value{GDBN} using @var{directory} as its working directory,
40765 instead of the current directory.
40769 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
40770 @value{GDBN} to output the full file name and line number in a standard,
40771 recognizable fashion each time a stack frame is displayed (which
40772 includes each time the program stops). This recognizable format looks
40773 like two @samp{\032} characters, followed by the file name, line number
40774 and character position separated by colons, and a newline. The
40775 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
40776 characters as a signal to display the source code for the frame.
40779 Set the line speed (baud rate or bits per second) of any serial
40780 interface used by @value{GDBN} for remote debugging.
40782 @item -tty=@var{device}
40783 Run using @var{device} for your program's standard input and output.
40787 @c man begin SEEALSO gdb
40789 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
40790 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
40791 documentation are properly installed at your site, the command
40798 should give you access to the complete manual.
40800 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
40801 Richard M. Stallman and Roland H. Pesch, July 1991.
40805 @node gdbserver man
40806 @heading gdbserver man
40808 @c man title gdbserver Remote Server for the GNU Debugger
40810 @c man begin SYNOPSIS gdbserver
40811 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40813 gdbserver --attach @var{comm} @var{pid}
40815 gdbserver --multi @var{comm}
40819 @c man begin DESCRIPTION gdbserver
40820 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
40821 than the one which is running the program being debugged.
40824 @subheading Usage (server (target) side)
40827 Usage (server (target) side):
40830 First, you need to have a copy of the program you want to debug put onto
40831 the target system. The program can be stripped to save space if needed, as
40832 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
40833 the @value{GDBN} running on the host system.
40835 To use the server, you log on to the target system, and run the @command{gdbserver}
40836 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
40837 your program, and (c) its arguments. The general syntax is:
40840 target> gdbserver @var{comm} @var{program} [@var{args} ...]
40843 For example, using a serial port, you might say:
40847 @c @file would wrap it as F</dev/com1>.
40848 target> gdbserver /dev/com1 emacs foo.txt
40851 target> gdbserver @file{/dev/com1} emacs foo.txt
40855 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
40856 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
40857 waits patiently for the host @value{GDBN} to communicate with it.
40859 To use a TCP connection, you could say:
40862 target> gdbserver host:2345 emacs foo.txt
40865 This says pretty much the same thing as the last example, except that we are
40866 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
40867 that we are expecting to see a TCP connection from @code{host} to local TCP port
40868 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
40869 want for the port number as long as it does not conflict with any existing TCP
40870 ports on the target system. This same port number must be used in the host
40871 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
40872 you chose a port number that conflicts with another service, @command{gdbserver} will
40873 print an error message and exit.
40875 @command{gdbserver} can also attach to running programs.
40876 This is accomplished via the @option{--attach} argument. The syntax is:
40879 target> gdbserver --attach @var{comm} @var{pid}
40882 @var{pid} is the process ID of a currently running process. It isn't
40883 necessary to point @command{gdbserver} at a binary for the running process.
40885 To start @code{gdbserver} without supplying an initial command to run
40886 or process ID to attach, use the @option{--multi} command line option.
40887 In such case you should connect using @kbd{target extended-remote} to start
40888 the program you want to debug.
40891 target> gdbserver --multi @var{comm}
40895 @subheading Usage (host side)
40901 You need an unstripped copy of the target program on your host system, since
40902 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
40903 would, with the target program as the first argument. (You may need to use the
40904 @option{--baud} option if the serial line is running at anything except 9600 baud.)
40905 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
40906 new command you need to know about is @code{target remote}
40907 (or @code{target extended-remote}). Its argument is either
40908 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
40909 descriptor. For example:
40913 @c @file would wrap it as F</dev/ttyb>.
40914 (gdb) target remote /dev/ttyb
40917 (gdb) target remote @file{/dev/ttyb}
40922 communicates with the server via serial line @file{/dev/ttyb}, and:
40925 (gdb) target remote the-target:2345
40929 communicates via a TCP connection to port 2345 on host `the-target', where
40930 you previously started up @command{gdbserver} with the same port number. Note that for
40931 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
40932 command, otherwise you may get an error that looks something like
40933 `Connection refused'.
40935 @command{gdbserver} can also debug multiple inferiors at once,
40938 the @value{GDBN} manual in node @code{Inferiors and Programs}
40939 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
40942 @ref{Inferiors and Programs}.
40944 In such case use the @code{extended-remote} @value{GDBN} command variant:
40947 (gdb) target extended-remote the-target:2345
40950 The @command{gdbserver} option @option{--multi} may or may not be used in such
40954 @c man begin OPTIONS gdbserver
40955 There are three different modes for invoking @command{gdbserver}:
40960 Debug a specific program specified by its program name:
40963 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
40966 The @var{comm} parameter specifies how should the server communicate
40967 with @value{GDBN}; it is either a device name (to use a serial line),
40968 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
40969 stdin/stdout of @code{gdbserver}. Specify the name of the program to
40970 debug in @var{prog}. Any remaining arguments will be passed to the
40971 program verbatim. When the program exits, @value{GDBN} will close the
40972 connection, and @code{gdbserver} will exit.
40975 Debug a specific program by specifying the process ID of a running
40979 gdbserver --attach @var{comm} @var{pid}
40982 The @var{comm} parameter is as described above. Supply the process ID
40983 of a running program in @var{pid}; @value{GDBN} will do everything
40984 else. Like with the previous mode, when the process @var{pid} exits,
40985 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
40988 Multi-process mode -- debug more than one program/process:
40991 gdbserver --multi @var{comm}
40994 In this mode, @value{GDBN} can instruct @command{gdbserver} which
40995 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
40996 close the connection when a process being debugged exits, so you can
40997 debug several processes in the same session.
41000 In each of the modes you may specify these options:
41005 List all options, with brief explanations.
41008 This option causes @command{gdbserver} to print its version number and exit.
41011 @command{gdbserver} will attach to a running program. The syntax is:
41014 target> gdbserver --attach @var{comm} @var{pid}
41017 @var{pid} is the process ID of a currently running process. It isn't
41018 necessary to point @command{gdbserver} at a binary for the running process.
41021 To start @code{gdbserver} without supplying an initial command to run
41022 or process ID to attach, use this command line option.
41023 Then you can connect using @kbd{target extended-remote} and start
41024 the program you want to debug. The syntax is:
41027 target> gdbserver --multi @var{comm}
41031 Instruct @code{gdbserver} to display extra status information about the debugging
41033 This option is intended for @code{gdbserver} development and for bug reports to
41036 @item --remote-debug
41037 Instruct @code{gdbserver} to display remote protocol debug output.
41038 This option is intended for @code{gdbserver} development and for bug reports to
41041 @item --debug-format=option1@r{[},option2,...@r{]}
41042 Instruct @code{gdbserver} to include extra information in each line
41043 of debugging output.
41044 @xref{Other Command-Line Arguments for gdbserver}.
41047 Specify a wrapper to launch programs
41048 for debugging. The option should be followed by the name of the
41049 wrapper, then any command-line arguments to pass to the wrapper, then
41050 @kbd{--} indicating the end of the wrapper arguments.
41053 By default, @command{gdbserver} keeps the listening TCP port open, so that
41054 additional connections are possible. However, if you start @code{gdbserver}
41055 with the @option{--once} option, it will stop listening for any further
41056 connection attempts after connecting to the first @value{GDBN} session.
41058 @c --disable-packet is not documented for users.
41060 @c --disable-randomization and --no-disable-randomization are superseded by
41061 @c QDisableRandomization.
41066 @c man begin SEEALSO gdbserver
41068 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41069 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41070 documentation are properly installed at your site, the command
41076 should give you access to the complete manual.
41078 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41079 Richard M. Stallman and Roland H. Pesch, July 1991.
41086 @c man title gcore Generate a core file of a running program
41089 @c man begin SYNOPSIS gcore
41090 gcore [-o @var{filename}] @var{pid}
41094 @c man begin DESCRIPTION gcore
41095 Generate a core dump of a running program with process ID @var{pid}.
41096 Produced file is equivalent to a kernel produced core file as if the process
41097 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
41098 limit). Unlike after a crash, after @command{gcore} the program remains
41099 running without any change.
41102 @c man begin OPTIONS gcore
41104 @item -o @var{filename}
41105 The optional argument
41106 @var{filename} specifies the file name where to put the core dump.
41107 If not specified, the file name defaults to @file{core.@var{pid}},
41108 where @var{pid} is the running program process ID.
41112 @c man begin SEEALSO gcore
41114 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41115 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41116 documentation are properly installed at your site, the command
41123 should give you access to the complete manual.
41125 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41126 Richard M. Stallman and Roland H. Pesch, July 1991.
41133 @c man title gdbinit GDB initialization scripts
41136 @c man begin SYNOPSIS gdbinit
41137 @ifset SYSTEM_GDBINIT
41138 @value{SYSTEM_GDBINIT}
41147 @c man begin DESCRIPTION gdbinit
41148 These files contain @value{GDBN} commands to automatically execute during
41149 @value{GDBN} startup. The lines of contents are canned sequences of commands,
41152 the @value{GDBN} manual in node @code{Sequences}
41153 -- shell command @code{info -f gdb -n Sequences}.
41159 Please read more in
41161 the @value{GDBN} manual in node @code{Startup}
41162 -- shell command @code{info -f gdb -n Startup}.
41169 @ifset SYSTEM_GDBINIT
41170 @item @value{SYSTEM_GDBINIT}
41172 @ifclear SYSTEM_GDBINIT
41173 @item (not enabled with @code{--with-system-gdbinit} during compilation)
41175 System-wide initialization file. It is executed unless user specified
41176 @value{GDBN} option @code{-nx} or @code{-n}.
41179 the @value{GDBN} manual in node @code{System-wide configuration}
41180 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
41183 @ref{System-wide configuration}.
41187 User initialization file. It is executed unless user specified
41188 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
41191 Initialization file for current directory. It may need to be enabled with
41192 @value{GDBN} security command @code{set auto-load local-gdbinit}.
41195 the @value{GDBN} manual in node @code{Init File in the Current Directory}
41196 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
41199 @ref{Init File in the Current Directory}.
41204 @c man begin SEEALSO gdbinit
41206 gdb(1), @code{info -f gdb -n Startup}
41208 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41209 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41210 documentation are properly installed at your site, the command
41216 should give you access to the complete manual.
41218 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41219 Richard M. Stallman and Roland H. Pesch, July 1991.
41225 @node GNU Free Documentation License
41226 @appendix GNU Free Documentation License
41229 @node Concept Index
41230 @unnumbered Concept Index
41234 @node Command and Variable Index
41235 @unnumbered Command, Variable, and Function Index
41240 % I think something like @@colophon should be in texinfo. In the
41242 \long\def\colophon{\hbox to0pt{}\vfill
41243 \centerline{The body of this manual is set in}
41244 \centerline{\fontname\tenrm,}
41245 \centerline{with headings in {\bf\fontname\tenbf}}
41246 \centerline{and examples in {\tt\fontname\tentt}.}
41247 \centerline{{\it\fontname\tenit\/},}
41248 \centerline{{\bf\fontname\tenbf}, and}
41249 \centerline{{\sl\fontname\tensl\/}}
41250 \centerline{are used for emphasis.}\vfill}
41252 % Blame: doc@@cygnus.com, 1991.