1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.3 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
104 This edition of the GDB manual is dedicated to the memory of Fred
105 Fish. Fred was a long-standing contributor to GDB and to Free
106 software in general. We will miss him.
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) 1988-2010 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.
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 * Command Line Editing:: Command Line Editing
167 * Using History Interactively:: Using History Interactively
168 * Formatting Documentation:: How to format and print @value{GDBN} documentation
169 * Installing GDB:: Installing GDB
170 * Maintenance Commands:: Maintenance Commands
171 * Remote Protocol:: GDB Remote Serial Protocol
172 * Agent Expressions:: The GDB Agent Expression Mechanism
173 * Target Descriptions:: How targets can describe themselves to
175 * Operating System Information:: Getting additional information from
177 * Trace File Format:: GDB trace file format
178 * Copying:: GNU General Public License says
179 how you can copy and share GDB
180 * GNU Free Documentation License:: The license for this documentation
189 @unnumbered Summary of @value{GDBN}
191 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
192 going on ``inside'' another program while it executes---or what another
193 program was doing at the moment it crashed.
195 @value{GDBN} can do four main kinds of things (plus other things in support of
196 these) to help you catch bugs in the act:
200 Start your program, specifying anything that might affect its behavior.
203 Make your program stop on specified conditions.
206 Examine what has happened, when your program has stopped.
209 Change things in your program, so you can experiment with correcting the
210 effects of one bug and go on to learn about another.
213 You can use @value{GDBN} to debug programs written in C and C@t{++}.
214 For more information, see @ref{Supported Languages,,Supported Languages}.
215 For more information, see @ref{C,,C and C++}.
217 Support for D is partial. For information on D, see
221 Support for Modula-2 is partial. For information on Modula-2, see
222 @ref{Modula-2,,Modula-2}.
225 Debugging Pascal programs which use sets, subranges, file variables, or
226 nested functions does not currently work. @value{GDBN} does not support
227 entering expressions, printing values, or similar features using Pascal
231 @value{GDBN} can be used to debug programs written in Fortran, although
232 it may be necessary to refer to some variables with a trailing
235 @value{GDBN} can be used to debug programs written in Objective-C,
236 using either the Apple/NeXT or the GNU Objective-C runtime.
239 * Free Software:: Freely redistributable software
240 * Contributors:: Contributors to GDB
244 @unnumberedsec Free Software
246 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
247 General Public License
248 (GPL). The GPL gives you the freedom to copy or adapt a licensed
249 program---but every person getting a copy also gets with it the
250 freedom to modify that copy (which means that they must get access to
251 the source code), and the freedom to distribute further copies.
252 Typical software companies use copyrights to limit your freedoms; the
253 Free Software Foundation uses the GPL to preserve these freedoms.
255 Fundamentally, the General Public License is a license which says that
256 you have these freedoms and that you cannot take these freedoms away
259 @unnumberedsec Free Software Needs Free Documentation
261 The biggest deficiency in the free software community today is not in
262 the software---it is the lack of good free documentation that we can
263 include with the free software. Many of our most important
264 programs do not come with free reference manuals and free introductory
265 texts. Documentation is an essential part of any software package;
266 when an important free software package does not come with a free
267 manual and a free tutorial, that is a major gap. We have many such
270 Consider Perl, for instance. The tutorial manuals that people
271 normally use are non-free. How did this come about? Because the
272 authors of those manuals published them with restrictive terms---no
273 copying, no modification, source files not available---which exclude
274 them from the free software world.
276 That wasn't the first time this sort of thing happened, and it was far
277 from the last. Many times we have heard a GNU user eagerly describe a
278 manual that he is writing, his intended contribution to the community,
279 only to learn that he had ruined everything by signing a publication
280 contract to make it non-free.
282 Free documentation, like free software, is a matter of freedom, not
283 price. The problem with the non-free manual is not that publishers
284 charge a price for printed copies---that in itself is fine. (The Free
285 Software Foundation sells printed copies of manuals, too.) The
286 problem is the restrictions on the use of the manual. Free manuals
287 are available in source code form, and give you permission to copy and
288 modify. Non-free manuals do not allow this.
290 The criteria of freedom for a free manual are roughly the same as for
291 free software. Redistribution (including the normal kinds of
292 commercial redistribution) must be permitted, so that the manual can
293 accompany every copy of the program, both on-line and on paper.
295 Permission for modification of the technical content is crucial too.
296 When people modify the software, adding or changing features, if they
297 are conscientious they will change the manual too---so they can
298 provide accurate and clear documentation for the modified program. A
299 manual that leaves you no choice but to write a new manual to document
300 a changed version of the program is not really available to our
303 Some kinds of limits on the way modification is handled are
304 acceptable. For example, requirements to preserve the original
305 author's copyright notice, the distribution terms, or the list of
306 authors, are ok. It is also no problem to require modified versions
307 to include notice that they were modified. Even entire sections that
308 may not be deleted or changed are acceptable, as long as they deal
309 with nontechnical topics (like this one). These kinds of restrictions
310 are acceptable because they don't obstruct the community's normal use
313 However, it must be possible to modify all the @emph{technical}
314 content of the manual, and then distribute the result in all the usual
315 media, through all the usual channels. Otherwise, the restrictions
316 obstruct the use of the manual, it is not free, and we need another
317 manual to replace it.
319 Please spread the word about this issue. Our community continues to
320 lose manuals to proprietary publishing. If we spread the word that
321 free software needs free reference manuals and free tutorials, perhaps
322 the next person who wants to contribute by writing documentation will
323 realize, before it is too late, that only free manuals contribute to
324 the free software community.
326 If you are writing documentation, please insist on publishing it under
327 the GNU Free Documentation License or another free documentation
328 license. Remember that this decision requires your approval---you
329 don't have to let the publisher decide. Some commercial publishers
330 will use a free license if you insist, but they will not propose the
331 option; it is up to you to raise the issue and say firmly that this is
332 what you want. If the publisher you are dealing with refuses, please
333 try other publishers. If you're not sure whether a proposed license
334 is free, write to @email{licensing@@gnu.org}.
336 You can encourage commercial publishers to sell more free, copylefted
337 manuals and tutorials by buying them, and particularly by buying
338 copies from the publishers that paid for their writing or for major
339 improvements. Meanwhile, try to avoid buying non-free documentation
340 at all. Check the distribution terms of a manual before you buy it,
341 and insist that whoever seeks your business must respect your freedom.
342 Check the history of the book, and try to reward the publishers that
343 have paid or pay the authors to work on it.
345 The Free Software Foundation maintains a list of free documentation
346 published by other publishers, at
347 @url{http://www.fsf.org/doc/other-free-books.html}.
350 @unnumberedsec Contributors to @value{GDBN}
352 Richard Stallman was the original author of @value{GDBN}, and of many
353 other @sc{gnu} programs. Many others have contributed to its
354 development. This section attempts to credit major contributors. One
355 of the virtues of free software is that everyone is free to contribute
356 to it; with regret, we cannot actually acknowledge everyone here. The
357 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
358 blow-by-blow account.
360 Changes much prior to version 2.0 are lost in the mists of time.
363 @emph{Plea:} Additions to this section are particularly welcome. If you
364 or your friends (or enemies, to be evenhanded) have been unfairly
365 omitted from this list, we would like to add your names!
368 So that they may not regard their many labors as thankless, we
369 particularly thank those who shepherded @value{GDBN} through major
371 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
372 Jim Blandy (release 4.18);
373 Jason Molenda (release 4.17);
374 Stan Shebs (release 4.14);
375 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
376 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
377 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
378 Jim Kingdon (releases 3.5, 3.4, and 3.3);
379 and Randy Smith (releases 3.2, 3.1, and 3.0).
381 Richard Stallman, assisted at various times by Peter TerMaat, Chris
382 Hanson, and Richard Mlynarik, handled releases through 2.8.
384 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
385 in @value{GDBN}, with significant additional contributions from Per
386 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
387 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
388 much general update work leading to release 3.0).
390 @value{GDBN} uses the BFD subroutine library to examine multiple
391 object-file formats; BFD was a joint project of David V.
392 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
394 David Johnson wrote the original COFF support; Pace Willison did
395 the original support for encapsulated COFF.
397 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
399 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
400 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
402 Jean-Daniel Fekete contributed Sun 386i support.
403 Chris Hanson improved the HP9000 support.
404 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
405 David Johnson contributed Encore Umax support.
406 Jyrki Kuoppala contributed Altos 3068 support.
407 Jeff Law contributed HP PA and SOM support.
408 Keith Packard contributed NS32K support.
409 Doug Rabson contributed Acorn Risc Machine support.
410 Bob Rusk contributed Harris Nighthawk CX-UX support.
411 Chris Smith contributed Convex support (and Fortran debugging).
412 Jonathan Stone contributed Pyramid support.
413 Michael Tiemann contributed SPARC support.
414 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
415 Pace Willison contributed Intel 386 support.
416 Jay Vosburgh contributed Symmetry support.
417 Marko Mlinar contributed OpenRISC 1000 support.
419 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
421 Rich Schaefer and Peter Schauer helped with support of SunOS shared
424 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
425 about several machine instruction sets.
427 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
428 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
429 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
430 and RDI targets, respectively.
432 Brian Fox is the author of the readline libraries providing
433 command-line editing and command history.
435 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
436 Modula-2 support, and contributed the Languages chapter of this manual.
438 Fred Fish wrote most of the support for Unix System Vr4.
439 He also enhanced the command-completion support to cover C@t{++} overloaded
442 Hitachi America (now Renesas America), Ltd. sponsored the support for
443 H8/300, H8/500, and Super-H processors.
445 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
447 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
450 Toshiba sponsored the support for the TX39 Mips processor.
452 Matsushita sponsored the support for the MN10200 and MN10300 processors.
454 Fujitsu sponsored the support for SPARClite and FR30 processors.
456 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
459 Michael Snyder added support for tracepoints.
461 Stu Grossman wrote gdbserver.
463 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
464 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
466 The following people at the Hewlett-Packard Company contributed
467 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
468 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
469 compiler, and the Text User Interface (nee Terminal User Interface):
470 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
471 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
472 provided HP-specific information in this manual.
474 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
475 Robert Hoehne made significant contributions to the DJGPP port.
477 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
478 development since 1991. Cygnus engineers who have worked on @value{GDBN}
479 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
480 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
481 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
482 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
483 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
484 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
485 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
486 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
487 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
488 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
489 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
490 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
491 Zuhn have made contributions both large and small.
493 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
494 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
496 Jim Blandy added support for preprocessor macros, while working for Red
499 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
500 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
501 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
502 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
503 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
504 with the migration of old architectures to this new framework.
506 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
507 unwinder framework, this consisting of a fresh new design featuring
508 frame IDs, independent frame sniffers, and the sentinel frame. Mark
509 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
510 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
511 trad unwinders. The architecture-specific changes, each involving a
512 complete rewrite of the architecture's frame code, were carried out by
513 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
514 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
515 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
516 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
519 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
520 Tensilica, Inc.@: contributed support for Xtensa processors. Others
521 who have worked on the Xtensa port of @value{GDBN} in the past include
522 Steve Tjiang, John Newlin, and Scott Foehner.
524 Michael Eager and staff of Xilinx, Inc., contributed support for the
525 Xilinx MicroBlaze architecture.
528 @chapter A Sample @value{GDBN} Session
530 You can use this manual at your leisure to read all about @value{GDBN}.
531 However, a handful of commands are enough to get started using the
532 debugger. This chapter illustrates those commands.
535 In this sample session, we emphasize user input like this: @b{input},
536 to make it easier to pick out from the surrounding output.
539 @c FIXME: this example may not be appropriate for some configs, where
540 @c FIXME...primary interest is in remote use.
542 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
543 processor) exhibits the following bug: sometimes, when we change its
544 quote strings from the default, the commands used to capture one macro
545 definition within another stop working. In the following short @code{m4}
546 session, we define a macro @code{foo} which expands to @code{0000}; we
547 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
548 same thing. However, when we change the open quote string to
549 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
550 procedure fails to define a new synonym @code{baz}:
559 @b{define(bar,defn(`foo'))}
563 @b{changequote(<QUOTE>,<UNQUOTE>)}
565 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
568 m4: End of input: 0: fatal error: EOF in string
572 Let us use @value{GDBN} to try to see what is going on.
575 $ @b{@value{GDBP} m4}
576 @c FIXME: this falsifies the exact text played out, to permit smallbook
577 @c FIXME... format to come out better.
578 @value{GDBN} is free software and you are welcome to distribute copies
579 of it under certain conditions; type "show copying" to see
581 There is absolutely no warranty for @value{GDBN}; type "show warranty"
584 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
589 @value{GDBN} reads only enough symbol data to know where to find the
590 rest when needed; as a result, the first prompt comes up very quickly.
591 We now tell @value{GDBN} to use a narrower display width than usual, so
592 that examples fit in this manual.
595 (@value{GDBP}) @b{set width 70}
599 We need to see how the @code{m4} built-in @code{changequote} works.
600 Having looked at the source, we know the relevant subroutine is
601 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
602 @code{break} command.
605 (@value{GDBP}) @b{break m4_changequote}
606 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
610 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
611 control; as long as control does not reach the @code{m4_changequote}
612 subroutine, the program runs as usual:
615 (@value{GDBP}) @b{run}
616 Starting program: /work/Editorial/gdb/gnu/m4/m4
624 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
625 suspends execution of @code{m4}, displaying information about the
626 context where it stops.
629 @b{changequote(<QUOTE>,<UNQUOTE>)}
631 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
633 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
637 Now we use the command @code{n} (@code{next}) to advance execution to
638 the next line of the current function.
642 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
647 @code{set_quotes} looks like a promising subroutine. We can go into it
648 by using the command @code{s} (@code{step}) instead of @code{next}.
649 @code{step} goes to the next line to be executed in @emph{any}
650 subroutine, so it steps into @code{set_quotes}.
654 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
656 530 if (lquote != def_lquote)
660 The display that shows the subroutine where @code{m4} is now
661 suspended (and its arguments) is called a stack frame display. It
662 shows a summary of the stack. We can use the @code{backtrace}
663 command (which can also be spelled @code{bt}), to see where we are
664 in the stack as a whole: the @code{backtrace} command displays a
665 stack frame for each active subroutine.
668 (@value{GDBP}) @b{bt}
669 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
671 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
673 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
674 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
676 #4 0x79dc in expand_input () at macro.c:40
677 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
681 We step through a few more lines to see what happens. The first two
682 times, we can use @samp{s}; the next two times we use @code{n} to avoid
683 falling into the @code{xstrdup} subroutine.
687 0x3b5c 532 if (rquote != def_rquote)
689 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
690 def_lquote : xstrdup(lq);
692 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
695 538 len_lquote = strlen(rquote);
699 The last line displayed looks a little odd; we can examine the variables
700 @code{lquote} and @code{rquote} to see if they are in fact the new left
701 and right quotes we specified. We use the command @code{p}
702 (@code{print}) to see their values.
705 (@value{GDBP}) @b{p lquote}
706 $1 = 0x35d40 "<QUOTE>"
707 (@value{GDBP}) @b{p rquote}
708 $2 = 0x35d50 "<UNQUOTE>"
712 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
713 To look at some context, we can display ten lines of source
714 surrounding the current line with the @code{l} (@code{list}) command.
720 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
722 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
725 538 len_lquote = strlen(rquote);
726 539 len_rquote = strlen(lquote);
733 Let us step past the two lines that set @code{len_lquote} and
734 @code{len_rquote}, and then examine the values of those variables.
738 539 len_rquote = strlen(lquote);
741 (@value{GDBP}) @b{p len_lquote}
743 (@value{GDBP}) @b{p len_rquote}
748 That certainly looks wrong, assuming @code{len_lquote} and
749 @code{len_rquote} are meant to be the lengths of @code{lquote} and
750 @code{rquote} respectively. We can set them to better values using
751 the @code{p} command, since it can print the value of
752 any expression---and that expression can include subroutine calls and
756 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
758 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
763 Is that enough to fix the problem of using the new quotes with the
764 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
765 executing with the @code{c} (@code{continue}) command, and then try the
766 example that caused trouble initially:
772 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
779 Success! The new quotes now work just as well as the default ones. The
780 problem seems to have been just the two typos defining the wrong
781 lengths. We allow @code{m4} exit by giving it an EOF as input:
785 Program exited normally.
789 The message @samp{Program exited normally.} is from @value{GDBN}; it
790 indicates @code{m4} has finished executing. We can end our @value{GDBN}
791 session with the @value{GDBN} @code{quit} command.
794 (@value{GDBP}) @b{quit}
798 @chapter Getting In and Out of @value{GDBN}
800 This chapter discusses how to start @value{GDBN}, and how to get out of it.
804 type @samp{@value{GDBP}} to start @value{GDBN}.
806 type @kbd{quit} or @kbd{Ctrl-d} to exit.
810 * Invoking GDB:: How to start @value{GDBN}
811 * Quitting GDB:: How to quit @value{GDBN}
812 * Shell Commands:: How to use shell commands inside @value{GDBN}
813 * Logging Output:: How to log @value{GDBN}'s output to a file
817 @section Invoking @value{GDBN}
819 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
820 @value{GDBN} reads commands from the terminal until you tell it to exit.
822 You can also run @code{@value{GDBP}} with a variety of arguments and options,
823 to specify more of your debugging environment at the outset.
825 The command-line options described here are designed
826 to cover a variety of situations; in some environments, some of these
827 options may effectively be unavailable.
829 The most usual way to start @value{GDBN} is with one argument,
830 specifying an executable program:
833 @value{GDBP} @var{program}
837 You can also start with both an executable program and a core file
841 @value{GDBP} @var{program} @var{core}
844 You can, instead, specify a process ID as a second argument, if you want
845 to debug a running process:
848 @value{GDBP} @var{program} 1234
852 would attach @value{GDBN} to process @code{1234} (unless you also have a file
853 named @file{1234}; @value{GDBN} does check for a core file first).
855 Taking advantage of the second command-line argument requires a fairly
856 complete operating system; when you use @value{GDBN} as a remote
857 debugger attached to a bare board, there may not be any notion of
858 ``process'', and there is often no way to get a core dump. @value{GDBN}
859 will warn you if it is unable to attach or to read core dumps.
861 You can optionally have @code{@value{GDBP}} pass any arguments after the
862 executable file to the inferior using @code{--args}. This option stops
865 @value{GDBP} --args gcc -O2 -c foo.c
867 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
868 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
870 You can run @code{@value{GDBP}} without printing the front material, which describes
871 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
878 You can further control how @value{GDBN} starts up by using command-line
879 options. @value{GDBN} itself can remind you of the options available.
889 to display all available options and briefly describe their use
890 (@samp{@value{GDBP} -h} is a shorter equivalent).
892 All options and command line arguments you give are processed
893 in sequential order. The order makes a difference when the
894 @samp{-x} option is used.
898 * File Options:: Choosing files
899 * Mode Options:: Choosing modes
900 * Startup:: What @value{GDBN} does during startup
904 @subsection Choosing Files
906 When @value{GDBN} starts, it reads any arguments other than options as
907 specifying an executable file and core file (or process ID). This is
908 the same as if the arguments were specified by the @samp{-se} and
909 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
910 first argument that does not have an associated option flag as
911 equivalent to the @samp{-se} option followed by that argument; and the
912 second argument that does not have an associated option flag, if any, as
913 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
914 If the second argument begins with a decimal digit, @value{GDBN} will
915 first attempt to attach to it as a process, and if that fails, attempt
916 to open it as a corefile. If you have a corefile whose name begins with
917 a digit, you can prevent @value{GDBN} from treating it as a pid by
918 prefixing it with @file{./}, e.g.@: @file{./12345}.
920 If @value{GDBN} has not been configured to included core file support,
921 such as for most embedded targets, then it will complain about a second
922 argument and ignore it.
924 Many options have both long and short forms; both are shown in the
925 following list. @value{GDBN} also recognizes the long forms if you truncate
926 them, so long as enough of the option is present to be unambiguous.
927 (If you prefer, you can flag option arguments with @samp{--} rather
928 than @samp{-}, though we illustrate the more usual convention.)
930 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
931 @c way, both those who look for -foo and --foo in the index, will find
935 @item -symbols @var{file}
937 @cindex @code{--symbols}
939 Read symbol table from file @var{file}.
941 @item -exec @var{file}
943 @cindex @code{--exec}
945 Use file @var{file} as the executable file to execute when appropriate,
946 and for examining pure data in conjunction with a core dump.
950 Read symbol table from file @var{file} and use it as the executable
953 @item -core @var{file}
955 @cindex @code{--core}
957 Use file @var{file} as a core dump to examine.
959 @item -pid @var{number}
960 @itemx -p @var{number}
963 Connect to process ID @var{number}, as with the @code{attach} command.
965 @item -command @var{file}
967 @cindex @code{--command}
969 Execute commands from file @var{file}. The contents of this file is
970 evaluated exactly as the @code{source} command would.
971 @xref{Command Files,, Command files}.
973 @item -eval-command @var{command}
974 @itemx -ex @var{command}
975 @cindex @code{--eval-command}
977 Execute a single @value{GDBN} command.
979 This option may be used multiple times to call multiple commands. It may
980 also be interleaved with @samp{-command} as required.
983 @value{GDBP} -ex 'target sim' -ex 'load' \
984 -x setbreakpoints -ex 'run' a.out
987 @item -directory @var{directory}
988 @itemx -d @var{directory}
989 @cindex @code{--directory}
991 Add @var{directory} to the path to search for source and script files.
995 @cindex @code{--readnow}
997 Read each symbol file's entire symbol table immediately, rather than
998 the default, which is to read it incrementally as it is needed.
999 This makes startup slower, but makes future operations faster.
1004 @subsection Choosing Modes
1006 You can run @value{GDBN} in various alternative modes---for example, in
1007 batch mode or quiet mode.
1014 Do not execute commands found in any initialization files. Normally,
1015 @value{GDBN} executes the commands in these files after all the command
1016 options and arguments have been processed. @xref{Command Files,,Command
1022 @cindex @code{--quiet}
1023 @cindex @code{--silent}
1025 ``Quiet''. Do not print the introductory and copyright messages. These
1026 messages are also suppressed in batch mode.
1029 @cindex @code{--batch}
1030 Run in batch mode. Exit with status @code{0} after processing all the
1031 command files specified with @samp{-x} (and all commands from
1032 initialization files, if not inhibited with @samp{-n}). Exit with
1033 nonzero status if an error occurs in executing the @value{GDBN} commands
1034 in the command files. Batch mode also disables pagination, sets unlimited
1035 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1036 off} were in effect (@pxref{Messages/Warnings}).
1038 Batch mode may be useful for running @value{GDBN} as a filter, for
1039 example to download and run a program on another computer; in order to
1040 make this more useful, the message
1043 Program exited normally.
1047 (which is ordinarily issued whenever a program running under
1048 @value{GDBN} control terminates) is not issued when running in batch
1052 @cindex @code{--batch-silent}
1053 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1054 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1055 unaffected). This is much quieter than @samp{-silent} and would be useless
1056 for an interactive session.
1058 This is particularly useful when using targets that give @samp{Loading section}
1059 messages, for example.
1061 Note that targets that give their output via @value{GDBN}, as opposed to
1062 writing directly to @code{stdout}, will also be made silent.
1064 @item -return-child-result
1065 @cindex @code{--return-child-result}
1066 The return code from @value{GDBN} will be the return code from the child
1067 process (the process being debugged), with the following exceptions:
1071 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1072 internal error. In this case the exit code is the same as it would have been
1073 without @samp{-return-child-result}.
1075 The user quits with an explicit value. E.g., @samp{quit 1}.
1077 The child process never runs, or is not allowed to terminate, in which case
1078 the exit code will be -1.
1081 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1082 when @value{GDBN} is being used as a remote program loader or simulator
1087 @cindex @code{--nowindows}
1089 ``No windows''. If @value{GDBN} comes with a graphical user interface
1090 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1091 interface. If no GUI is available, this option has no effect.
1095 @cindex @code{--windows}
1097 If @value{GDBN} includes a GUI, then this option requires it to be
1100 @item -cd @var{directory}
1102 Run @value{GDBN} using @var{directory} as its working directory,
1103 instead of the current directory.
1107 @cindex @code{--fullname}
1109 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1110 subprocess. It tells @value{GDBN} to output the full file name and line
1111 number in a standard, recognizable fashion each time a stack frame is
1112 displayed (which includes each time your program stops). This
1113 recognizable format looks like two @samp{\032} characters, followed by
1114 the file name, line number and character position separated by colons,
1115 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1116 @samp{\032} characters as a signal to display the source code for the
1120 @cindex @code{--epoch}
1121 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1122 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1123 routines so as to allow Epoch to display values of expressions in a
1126 @item -annotate @var{level}
1127 @cindex @code{--annotate}
1128 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1129 effect is identical to using @samp{set annotate @var{level}}
1130 (@pxref{Annotations}). The annotation @var{level} controls how much
1131 information @value{GDBN} prints together with its prompt, values of
1132 expressions, source lines, and other types of output. Level 0 is the
1133 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1134 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1135 that control @value{GDBN}, and level 2 has been deprecated.
1137 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1141 @cindex @code{--args}
1142 Change interpretation of command line so that arguments following the
1143 executable file are passed as command line arguments to the inferior.
1144 This option stops option processing.
1146 @item -baud @var{bps}
1148 @cindex @code{--baud}
1150 Set the line speed (baud rate or bits per second) of any serial
1151 interface used by @value{GDBN} for remote debugging.
1153 @item -l @var{timeout}
1155 Set the timeout (in seconds) of any communication used by @value{GDBN}
1156 for remote debugging.
1158 @item -tty @var{device}
1159 @itemx -t @var{device}
1160 @cindex @code{--tty}
1162 Run using @var{device} for your program's standard input and output.
1163 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1165 @c resolve the situation of these eventually
1167 @cindex @code{--tui}
1168 Activate the @dfn{Text User Interface} when starting. The Text User
1169 Interface manages several text windows on the terminal, showing
1170 source, assembly, registers and @value{GDBN} command outputs
1171 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1172 Text User Interface can be enabled by invoking the program
1173 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1174 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1177 @c @cindex @code{--xdb}
1178 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1179 @c For information, see the file @file{xdb_trans.html}, which is usually
1180 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1183 @item -interpreter @var{interp}
1184 @cindex @code{--interpreter}
1185 Use the interpreter @var{interp} for interface with the controlling
1186 program or device. This option is meant to be set by programs which
1187 communicate with @value{GDBN} using it as a back end.
1188 @xref{Interpreters, , Command Interpreters}.
1190 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1191 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1192 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1193 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1194 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1195 @sc{gdb/mi} interfaces are no longer supported.
1198 @cindex @code{--write}
1199 Open the executable and core files for both reading and writing. This
1200 is equivalent to the @samp{set write on} command inside @value{GDBN}
1204 @cindex @code{--statistics}
1205 This option causes @value{GDBN} to print statistics about time and
1206 memory usage after it completes each command and returns to the prompt.
1209 @cindex @code{--version}
1210 This option causes @value{GDBN} to print its version number and
1211 no-warranty blurb, and exit.
1216 @subsection What @value{GDBN} Does During Startup
1217 @cindex @value{GDBN} startup
1219 Here's the description of what @value{GDBN} does during session startup:
1223 Sets up the command interpreter as specified by the command line
1224 (@pxref{Mode Options, interpreter}).
1228 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1229 used when building @value{GDBN}; @pxref{System-wide configuration,
1230 ,System-wide configuration and settings}) and executes all the commands in
1234 Reads the init file (if any) in your home directory@footnote{On
1235 DOS/Windows systems, the home directory is the one pointed to by the
1236 @code{HOME} environment variable.} and executes all the commands in
1240 Processes command line options and operands.
1243 Reads and executes the commands from init file (if any) in the current
1244 working directory. This is only done if the current directory is
1245 different from your home directory. Thus, you can have more than one
1246 init file, one generic in your home directory, and another, specific
1247 to the program you are debugging, in the directory where you invoke
1251 Reads command files specified by the @samp{-x} option. @xref{Command
1252 Files}, for more details about @value{GDBN} command files.
1255 Reads the command history recorded in the @dfn{history file}.
1256 @xref{Command History}, for more details about the command history and the
1257 files where @value{GDBN} records it.
1260 Init files use the same syntax as @dfn{command files} (@pxref{Command
1261 Files}) and are processed by @value{GDBN} in the same way. The init
1262 file in your home directory can set options (such as @samp{set
1263 complaints}) that affect subsequent processing of command line options
1264 and operands. Init files are not executed if you use the @samp{-nx}
1265 option (@pxref{Mode Options, ,Choosing Modes}).
1267 To display the list of init files loaded by gdb at startup, you
1268 can use @kbd{gdb --help}.
1270 @cindex init file name
1271 @cindex @file{.gdbinit}
1272 @cindex @file{gdb.ini}
1273 The @value{GDBN} init files are normally called @file{.gdbinit}.
1274 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1275 the limitations of file names imposed by DOS filesystems. The Windows
1276 ports of @value{GDBN} use the standard name, but if they find a
1277 @file{gdb.ini} file, they warn you about that and suggest to rename
1278 the file to the standard name.
1282 @section Quitting @value{GDBN}
1283 @cindex exiting @value{GDBN}
1284 @cindex leaving @value{GDBN}
1287 @kindex quit @r{[}@var{expression}@r{]}
1288 @kindex q @r{(@code{quit})}
1289 @item quit @r{[}@var{expression}@r{]}
1291 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1292 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1293 do not supply @var{expression}, @value{GDBN} will terminate normally;
1294 otherwise it will terminate using the result of @var{expression} as the
1299 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1300 terminates the action of any @value{GDBN} command that is in progress and
1301 returns to @value{GDBN} command level. It is safe to type the interrupt
1302 character at any time because @value{GDBN} does not allow it to take effect
1303 until a time when it is safe.
1305 If you have been using @value{GDBN} to control an attached process or
1306 device, you can release it with the @code{detach} command
1307 (@pxref{Attach, ,Debugging an Already-running Process}).
1309 @node Shell Commands
1310 @section Shell Commands
1312 If you need to execute occasional shell commands during your
1313 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1314 just use the @code{shell} command.
1318 @cindex shell escape
1319 @item shell @var{command string}
1320 Invoke a standard shell to execute @var{command string}.
1321 If it exists, the environment variable @code{SHELL} determines which
1322 shell to run. Otherwise @value{GDBN} uses the default shell
1323 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1326 The utility @code{make} is often needed in development environments.
1327 You do not have to use the @code{shell} command for this purpose in
1332 @cindex calling make
1333 @item make @var{make-args}
1334 Execute the @code{make} program with the specified
1335 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1338 @node Logging Output
1339 @section Logging Output
1340 @cindex logging @value{GDBN} output
1341 @cindex save @value{GDBN} output to a file
1343 You may want to save the output of @value{GDBN} commands to a file.
1344 There are several commands to control @value{GDBN}'s logging.
1348 @item set logging on
1350 @item set logging off
1352 @cindex logging file name
1353 @item set logging file @var{file}
1354 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1355 @item set logging overwrite [on|off]
1356 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1357 you want @code{set logging on} to overwrite the logfile instead.
1358 @item set logging redirect [on|off]
1359 By default, @value{GDBN} output will go to both the terminal and the logfile.
1360 Set @code{redirect} if you want output to go only to the log file.
1361 @kindex show logging
1363 Show the current values of the logging settings.
1367 @chapter @value{GDBN} Commands
1369 You can abbreviate a @value{GDBN} command to the first few letters of the command
1370 name, if that abbreviation is unambiguous; and you can repeat certain
1371 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1372 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1373 show you the alternatives available, if there is more than one possibility).
1376 * Command Syntax:: How to give commands to @value{GDBN}
1377 * Completion:: Command completion
1378 * Help:: How to ask @value{GDBN} for help
1381 @node Command Syntax
1382 @section Command Syntax
1384 A @value{GDBN} command is a single line of input. There is no limit on
1385 how long it can be. It starts with a command name, which is followed by
1386 arguments whose meaning depends on the command name. For example, the
1387 command @code{step} accepts an argument which is the number of times to
1388 step, as in @samp{step 5}. You can also use the @code{step} command
1389 with no arguments. Some commands do not allow any arguments.
1391 @cindex abbreviation
1392 @value{GDBN} command names may always be truncated if that abbreviation is
1393 unambiguous. Other possible command abbreviations are listed in the
1394 documentation for individual commands. In some cases, even ambiguous
1395 abbreviations are allowed; for example, @code{s} is specially defined as
1396 equivalent to @code{step} even though there are other commands whose
1397 names start with @code{s}. You can test abbreviations by using them as
1398 arguments to the @code{help} command.
1400 @cindex repeating commands
1401 @kindex RET @r{(repeat last command)}
1402 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1403 repeat the previous command. Certain commands (for example, @code{run})
1404 will not repeat this way; these are commands whose unintentional
1405 repetition might cause trouble and which you are unlikely to want to
1406 repeat. User-defined commands can disable this feature; see
1407 @ref{Define, dont-repeat}.
1409 The @code{list} and @code{x} commands, when you repeat them with
1410 @key{RET}, construct new arguments rather than repeating
1411 exactly as typed. This permits easy scanning of source or memory.
1413 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1414 output, in a way similar to the common utility @code{more}
1415 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1416 @key{RET} too many in this situation, @value{GDBN} disables command
1417 repetition after any command that generates this sort of display.
1419 @kindex # @r{(a comment)}
1421 Any text from a @kbd{#} to the end of the line is a comment; it does
1422 nothing. This is useful mainly in command files (@pxref{Command
1423 Files,,Command Files}).
1425 @cindex repeating command sequences
1426 @kindex Ctrl-o @r{(operate-and-get-next)}
1427 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1428 commands. This command accepts the current line, like @key{RET}, and
1429 then fetches the next line relative to the current line from the history
1433 @section Command Completion
1436 @cindex word completion
1437 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1438 only one possibility; it can also show you what the valid possibilities
1439 are for the next word in a command, at any time. This works for @value{GDBN}
1440 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1442 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1443 of a word. If there is only one possibility, @value{GDBN} fills in the
1444 word, and waits for you to finish the command (or press @key{RET} to
1445 enter it). For example, if you type
1447 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1448 @c complete accuracy in these examples; space introduced for clarity.
1449 @c If texinfo enhancements make it unnecessary, it would be nice to
1450 @c replace " @key" by "@key" in the following...
1452 (@value{GDBP}) info bre @key{TAB}
1456 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1457 the only @code{info} subcommand beginning with @samp{bre}:
1460 (@value{GDBP}) info breakpoints
1464 You can either press @key{RET} at this point, to run the @code{info
1465 breakpoints} command, or backspace and enter something else, if
1466 @samp{breakpoints} does not look like the command you expected. (If you
1467 were sure you wanted @code{info breakpoints} in the first place, you
1468 might as well just type @key{RET} immediately after @samp{info bre},
1469 to exploit command abbreviations rather than command completion).
1471 If there is more than one possibility for the next word when you press
1472 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1473 characters and try again, or just press @key{TAB} a second time;
1474 @value{GDBN} displays all the possible completions for that word. For
1475 example, you might want to set a breakpoint on a subroutine whose name
1476 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1477 just sounds the bell. Typing @key{TAB} again displays all the
1478 function names in your program that begin with those characters, for
1482 (@value{GDBP}) b make_ @key{TAB}
1483 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1484 make_a_section_from_file make_environ
1485 make_abs_section make_function_type
1486 make_blockvector make_pointer_type
1487 make_cleanup make_reference_type
1488 make_command make_symbol_completion_list
1489 (@value{GDBP}) b make_
1493 After displaying the available possibilities, @value{GDBN} copies your
1494 partial input (@samp{b make_} in the example) so you can finish the
1497 If you just want to see the list of alternatives in the first place, you
1498 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1499 means @kbd{@key{META} ?}. You can type this either by holding down a
1500 key designated as the @key{META} shift on your keyboard (if there is
1501 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1503 @cindex quotes in commands
1504 @cindex completion of quoted strings
1505 Sometimes the string you need, while logically a ``word'', may contain
1506 parentheses or other characters that @value{GDBN} normally excludes from
1507 its notion of a word. To permit word completion to work in this
1508 situation, you may enclose words in @code{'} (single quote marks) in
1509 @value{GDBN} commands.
1511 The most likely situation where you might need this is in typing the
1512 name of a C@t{++} function. This is because C@t{++} allows function
1513 overloading (multiple definitions of the same function, distinguished
1514 by argument type). For example, when you want to set a breakpoint you
1515 may need to distinguish whether you mean the version of @code{name}
1516 that takes an @code{int} parameter, @code{name(int)}, or the version
1517 that takes a @code{float} parameter, @code{name(float)}. To use the
1518 word-completion facilities in this situation, type a single quote
1519 @code{'} at the beginning of the function name. This alerts
1520 @value{GDBN} that it may need to consider more information than usual
1521 when you press @key{TAB} or @kbd{M-?} to request word completion:
1524 (@value{GDBP}) b 'bubble( @kbd{M-?}
1525 bubble(double,double) bubble(int,int)
1526 (@value{GDBP}) b 'bubble(
1529 In some cases, @value{GDBN} can tell that completing a name requires using
1530 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1531 completing as much as it can) if you do not type the quote in the first
1535 (@value{GDBP}) b bub @key{TAB}
1536 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1537 (@value{GDBP}) b 'bubble(
1541 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1542 you have not yet started typing the argument list when you ask for
1543 completion on an overloaded symbol.
1545 For more information about overloaded functions, see @ref{C Plus Plus
1546 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1547 overload-resolution off} to disable overload resolution;
1548 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1550 @cindex completion of structure field names
1551 @cindex structure field name completion
1552 @cindex completion of union field names
1553 @cindex union field name completion
1554 When completing in an expression which looks up a field in a
1555 structure, @value{GDBN} also tries@footnote{The completer can be
1556 confused by certain kinds of invalid expressions. Also, it only
1557 examines the static type of the expression, not the dynamic type.} to
1558 limit completions to the field names available in the type of the
1562 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1563 magic to_delete to_fputs to_put to_rewind
1564 to_data to_flush to_isatty to_read to_write
1568 This is because the @code{gdb_stdout} is a variable of the type
1569 @code{struct ui_file} that is defined in @value{GDBN} sources as
1576 ui_file_flush_ftype *to_flush;
1577 ui_file_write_ftype *to_write;
1578 ui_file_fputs_ftype *to_fputs;
1579 ui_file_read_ftype *to_read;
1580 ui_file_delete_ftype *to_delete;
1581 ui_file_isatty_ftype *to_isatty;
1582 ui_file_rewind_ftype *to_rewind;
1583 ui_file_put_ftype *to_put;
1590 @section Getting Help
1591 @cindex online documentation
1594 You can always ask @value{GDBN} itself for information on its commands,
1595 using the command @code{help}.
1598 @kindex h @r{(@code{help})}
1601 You can use @code{help} (abbreviated @code{h}) with no arguments to
1602 display a short list of named classes of commands:
1606 List of classes of commands:
1608 aliases -- Aliases of other commands
1609 breakpoints -- Making program stop at certain points
1610 data -- Examining data
1611 files -- Specifying and examining files
1612 internals -- Maintenance commands
1613 obscure -- Obscure features
1614 running -- Running the program
1615 stack -- Examining the stack
1616 status -- Status inquiries
1617 support -- Support facilities
1618 tracepoints -- Tracing of program execution without
1619 stopping the program
1620 user-defined -- User-defined commands
1622 Type "help" followed by a class name for a list of
1623 commands in that class.
1624 Type "help" followed by command name for full
1626 Command name abbreviations are allowed if unambiguous.
1629 @c the above line break eliminates huge line overfull...
1631 @item help @var{class}
1632 Using one of the general help classes as an argument, you can get a
1633 list of the individual commands in that class. For example, here is the
1634 help display for the class @code{status}:
1637 (@value{GDBP}) help status
1642 @c Line break in "show" line falsifies real output, but needed
1643 @c to fit in smallbook page size.
1644 info -- Generic command for showing things
1645 about the program being debugged
1646 show -- Generic command for showing things
1649 Type "help" followed by command name for full
1651 Command name abbreviations are allowed if unambiguous.
1655 @item help @var{command}
1656 With a command name as @code{help} argument, @value{GDBN} displays a
1657 short paragraph on how to use that command.
1660 @item apropos @var{args}
1661 The @code{apropos} command searches through all of the @value{GDBN}
1662 commands, and their documentation, for the regular expression specified in
1663 @var{args}. It prints out all matches found. For example:
1674 set symbol-reloading -- Set dynamic symbol table reloading
1675 multiple times in one run
1676 show symbol-reloading -- Show dynamic symbol table reloading
1677 multiple times in one run
1682 @item complete @var{args}
1683 The @code{complete @var{args}} command lists all the possible completions
1684 for the beginning of a command. Use @var{args} to specify the beginning of the
1685 command you want completed. For example:
1691 @noindent results in:
1702 @noindent This is intended for use by @sc{gnu} Emacs.
1705 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1706 and @code{show} to inquire about the state of your program, or the state
1707 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1708 manual introduces each of them in the appropriate context. The listings
1709 under @code{info} and under @code{show} in the Index point to
1710 all the sub-commands. @xref{Index}.
1715 @kindex i @r{(@code{info})}
1717 This command (abbreviated @code{i}) is for describing the state of your
1718 program. For example, you can show the arguments passed to a function
1719 with @code{info args}, list the registers currently in use with @code{info
1720 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1721 You can get a complete list of the @code{info} sub-commands with
1722 @w{@code{help info}}.
1726 You can assign the result of an expression to an environment variable with
1727 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1728 @code{set prompt $}.
1732 In contrast to @code{info}, @code{show} is for describing the state of
1733 @value{GDBN} itself.
1734 You can change most of the things you can @code{show}, by using the
1735 related command @code{set}; for example, you can control what number
1736 system is used for displays with @code{set radix}, or simply inquire
1737 which is currently in use with @code{show radix}.
1740 To display all the settable parameters and their current
1741 values, you can use @code{show} with no arguments; you may also use
1742 @code{info set}. Both commands produce the same display.
1743 @c FIXME: "info set" violates the rule that "info" is for state of
1744 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1745 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1749 Here are three miscellaneous @code{show} subcommands, all of which are
1750 exceptional in lacking corresponding @code{set} commands:
1753 @kindex show version
1754 @cindex @value{GDBN} version number
1756 Show what version of @value{GDBN} is running. You should include this
1757 information in @value{GDBN} bug-reports. If multiple versions of
1758 @value{GDBN} are in use at your site, you may need to determine which
1759 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1760 commands are introduced, and old ones may wither away. Also, many
1761 system vendors ship variant versions of @value{GDBN}, and there are
1762 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1763 The version number is the same as the one announced when you start
1766 @kindex show copying
1767 @kindex info copying
1768 @cindex display @value{GDBN} copyright
1771 Display information about permission for copying @value{GDBN}.
1773 @kindex show warranty
1774 @kindex info warranty
1776 @itemx info warranty
1777 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1778 if your version of @value{GDBN} comes with one.
1783 @chapter Running Programs Under @value{GDBN}
1785 When you run a program under @value{GDBN}, you must first generate
1786 debugging information when you compile it.
1788 You may start @value{GDBN} with its arguments, if any, in an environment
1789 of your choice. If you are doing native debugging, you may redirect
1790 your program's input and output, debug an already running process, or
1791 kill a child process.
1794 * Compilation:: Compiling for debugging
1795 * Starting:: Starting your program
1796 * Arguments:: Your program's arguments
1797 * Environment:: Your program's environment
1799 * Working Directory:: Your program's working directory
1800 * Input/Output:: Your program's input and output
1801 * Attach:: Debugging an already-running process
1802 * Kill Process:: Killing the child process
1804 * Inferiors and Programs:: Debugging multiple inferiors and programs
1805 * Threads:: Debugging programs with multiple threads
1806 * Forks:: Debugging forks
1807 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1811 @section Compiling for Debugging
1813 In order to debug a program effectively, you need to generate
1814 debugging information when you compile it. This debugging information
1815 is stored in the object file; it describes the data type of each
1816 variable or function and the correspondence between source line numbers
1817 and addresses in the executable code.
1819 To request debugging information, specify the @samp{-g} option when you run
1822 Programs that are to be shipped to your customers are compiled with
1823 optimizations, using the @samp{-O} compiler option. However, some
1824 compilers are unable to handle the @samp{-g} and @samp{-O} options
1825 together. Using those compilers, you cannot generate optimized
1826 executables containing debugging information.
1828 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1829 without @samp{-O}, making it possible to debug optimized code. We
1830 recommend that you @emph{always} use @samp{-g} whenever you compile a
1831 program. You may think your program is correct, but there is no sense
1832 in pushing your luck. For more information, see @ref{Optimized Code}.
1834 Older versions of the @sc{gnu} C compiler permitted a variant option
1835 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1836 format; if your @sc{gnu} C compiler has this option, do not use it.
1838 @value{GDBN} knows about preprocessor macros and can show you their
1839 expansion (@pxref{Macros}). Most compilers do not include information
1840 about preprocessor macros in the debugging information if you specify
1841 the @option{-g} flag alone, because this information is rather large.
1842 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1843 provides macro information if you specify the options
1844 @option{-gdwarf-2} and @option{-g3}; the former option requests
1845 debugging information in the Dwarf 2 format, and the latter requests
1846 ``extra information''. In the future, we hope to find more compact
1847 ways to represent macro information, so that it can be included with
1852 @section Starting your Program
1858 @kindex r @r{(@code{run})}
1861 Use the @code{run} command to start your program under @value{GDBN}.
1862 You must first specify the program name (except on VxWorks) with an
1863 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1864 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1865 (@pxref{Files, ,Commands to Specify Files}).
1869 If you are running your program in an execution environment that
1870 supports processes, @code{run} creates an inferior process and makes
1871 that process run your program. In some environments without processes,
1872 @code{run} jumps to the start of your program. Other targets,
1873 like @samp{remote}, are always running. If you get an error
1874 message like this one:
1877 The "remote" target does not support "run".
1878 Try "help target" or "continue".
1882 then use @code{continue} to run your program. You may need @code{load}
1883 first (@pxref{load}).
1885 The execution of a program is affected by certain information it
1886 receives from its superior. @value{GDBN} provides ways to specify this
1887 information, which you must do @emph{before} starting your program. (You
1888 can change it after starting your program, but such changes only affect
1889 your program the next time you start it.) This information may be
1890 divided into four categories:
1893 @item The @emph{arguments.}
1894 Specify the arguments to give your program as the arguments of the
1895 @code{run} command. If a shell is available on your target, the shell
1896 is used to pass the arguments, so that you may use normal conventions
1897 (such as wildcard expansion or variable substitution) in describing
1899 In Unix systems, you can control which shell is used with the
1900 @code{SHELL} environment variable.
1901 @xref{Arguments, ,Your Program's Arguments}.
1903 @item The @emph{environment.}
1904 Your program normally inherits its environment from @value{GDBN}, but you can
1905 use the @value{GDBN} commands @code{set environment} and @code{unset
1906 environment} to change parts of the environment that affect
1907 your program. @xref{Environment, ,Your Program's Environment}.
1909 @item The @emph{working directory.}
1910 Your program inherits its working directory from @value{GDBN}. You can set
1911 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1912 @xref{Working Directory, ,Your Program's Working Directory}.
1914 @item The @emph{standard input and output.}
1915 Your program normally uses the same device for standard input and
1916 standard output as @value{GDBN} is using. You can redirect input and output
1917 in the @code{run} command line, or you can use the @code{tty} command to
1918 set a different device for your program.
1919 @xref{Input/Output, ,Your Program's Input and Output}.
1922 @emph{Warning:} While input and output redirection work, you cannot use
1923 pipes to pass the output of the program you are debugging to another
1924 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1928 When you issue the @code{run} command, your program begins to execute
1929 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1930 of how to arrange for your program to stop. Once your program has
1931 stopped, you may call functions in your program, using the @code{print}
1932 or @code{call} commands. @xref{Data, ,Examining Data}.
1934 If the modification time of your symbol file has changed since the last
1935 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1936 table, and reads it again. When it does this, @value{GDBN} tries to retain
1937 your current breakpoints.
1942 @cindex run to main procedure
1943 The name of the main procedure can vary from language to language.
1944 With C or C@t{++}, the main procedure name is always @code{main}, but
1945 other languages such as Ada do not require a specific name for their
1946 main procedure. The debugger provides a convenient way to start the
1947 execution of the program and to stop at the beginning of the main
1948 procedure, depending on the language used.
1950 The @samp{start} command does the equivalent of setting a temporary
1951 breakpoint at the beginning of the main procedure and then invoking
1952 the @samp{run} command.
1954 @cindex elaboration phase
1955 Some programs contain an @dfn{elaboration} phase where some startup code is
1956 executed before the main procedure is called. This depends on the
1957 languages used to write your program. In C@t{++}, for instance,
1958 constructors for static and global objects are executed before
1959 @code{main} is called. It is therefore possible that the debugger stops
1960 before reaching the main procedure. However, the temporary breakpoint
1961 will remain to halt execution.
1963 Specify the arguments to give to your program as arguments to the
1964 @samp{start} command. These arguments will be given verbatim to the
1965 underlying @samp{run} command. Note that the same arguments will be
1966 reused if no argument is provided during subsequent calls to
1967 @samp{start} or @samp{run}.
1969 It is sometimes necessary to debug the program during elaboration. In
1970 these cases, using the @code{start} command would stop the execution of
1971 your program too late, as the program would have already completed the
1972 elaboration phase. Under these circumstances, insert breakpoints in your
1973 elaboration code before running your program.
1975 @kindex set exec-wrapper
1976 @item set exec-wrapper @var{wrapper}
1977 @itemx show exec-wrapper
1978 @itemx unset exec-wrapper
1979 When @samp{exec-wrapper} is set, the specified wrapper is used to
1980 launch programs for debugging. @value{GDBN} starts your program
1981 with a shell command of the form @kbd{exec @var{wrapper}
1982 @var{program}}. Quoting is added to @var{program} and its
1983 arguments, but not to @var{wrapper}, so you should add quotes if
1984 appropriate for your shell. The wrapper runs until it executes
1985 your program, and then @value{GDBN} takes control.
1987 You can use any program that eventually calls @code{execve} with
1988 its arguments as a wrapper. Several standard Unix utilities do
1989 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1990 with @code{exec "$@@"} will also work.
1992 For example, you can use @code{env} to pass an environment variable to
1993 the debugged program, without setting the variable in your shell's
1997 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2001 This command is available when debugging locally on most targets, excluding
2002 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2004 @kindex set disable-randomization
2005 @item set disable-randomization
2006 @itemx set disable-randomization on
2007 This option (enabled by default in @value{GDBN}) will turn off the native
2008 randomization of the virtual address space of the started program. This option
2009 is useful for multiple debugging sessions to make the execution better
2010 reproducible and memory addresses reusable across debugging sessions.
2012 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2016 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2019 @item set disable-randomization off
2020 Leave the behavior of the started executable unchanged. Some bugs rear their
2021 ugly heads only when the program is loaded at certain addresses. If your bug
2022 disappears when you run the program under @value{GDBN}, that might be because
2023 @value{GDBN} by default disables the address randomization on platforms, such
2024 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2025 disable-randomization off} to try to reproduce such elusive bugs.
2027 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2028 It protects the programs against some kinds of security attacks. In these
2029 cases the attacker needs to know the exact location of a concrete executable
2030 code. Randomizing its location makes it impossible to inject jumps misusing
2031 a code at its expected addresses.
2033 Prelinking shared libraries provides a startup performance advantage but it
2034 makes addresses in these libraries predictable for privileged processes by
2035 having just unprivileged access at the target system. Reading the shared
2036 library binary gives enough information for assembling the malicious code
2037 misusing it. Still even a prelinked shared library can get loaded at a new
2038 random address just requiring the regular relocation process during the
2039 startup. Shared libraries not already prelinked are always loaded at
2040 a randomly chosen address.
2042 Position independent executables (PIE) contain position independent code
2043 similar to the shared libraries and therefore such executables get loaded at
2044 a randomly chosen address upon startup. PIE executables always load even
2045 already prelinked shared libraries at a random address. You can build such
2046 executable using @command{gcc -fPIE -pie}.
2048 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2049 (as long as the randomization is enabled).
2051 @item show disable-randomization
2052 Show the current setting of the explicit disable of the native randomization of
2053 the virtual address space of the started program.
2058 @section Your Program's Arguments
2060 @cindex arguments (to your program)
2061 The arguments to your program can be specified by the arguments of the
2063 They are passed to a shell, which expands wildcard characters and
2064 performs redirection of I/O, and thence to your program. Your
2065 @code{SHELL} environment variable (if it exists) specifies what shell
2066 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2067 the default shell (@file{/bin/sh} on Unix).
2069 On non-Unix systems, the program is usually invoked directly by
2070 @value{GDBN}, which emulates I/O redirection via the appropriate system
2071 calls, and the wildcard characters are expanded by the startup code of
2072 the program, not by the shell.
2074 @code{run} with no arguments uses the same arguments used by the previous
2075 @code{run}, or those set by the @code{set args} command.
2080 Specify the arguments to be used the next time your program is run. If
2081 @code{set args} has no arguments, @code{run} executes your program
2082 with no arguments. Once you have run your program with arguments,
2083 using @code{set args} before the next @code{run} is the only way to run
2084 it again without arguments.
2088 Show the arguments to give your program when it is started.
2092 @section Your Program's Environment
2094 @cindex environment (of your program)
2095 The @dfn{environment} consists of a set of environment variables and
2096 their values. Environment variables conventionally record such things as
2097 your user name, your home directory, your terminal type, and your search
2098 path for programs to run. Usually you set up environment variables with
2099 the shell and they are inherited by all the other programs you run. When
2100 debugging, it can be useful to try running your program with a modified
2101 environment without having to start @value{GDBN} over again.
2105 @item path @var{directory}
2106 Add @var{directory} to the front of the @code{PATH} environment variable
2107 (the search path for executables) that will be passed to your program.
2108 The value of @code{PATH} used by @value{GDBN} does not change.
2109 You may specify several directory names, separated by whitespace or by a
2110 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2111 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2112 is moved to the front, so it is searched sooner.
2114 You can use the string @samp{$cwd} to refer to whatever is the current
2115 working directory at the time @value{GDBN} searches the path. If you
2116 use @samp{.} instead, it refers to the directory where you executed the
2117 @code{path} command. @value{GDBN} replaces @samp{.} in the
2118 @var{directory} argument (with the current path) before adding
2119 @var{directory} to the search path.
2120 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2121 @c document that, since repeating it would be a no-op.
2125 Display the list of search paths for executables (the @code{PATH}
2126 environment variable).
2128 @kindex show environment
2129 @item show environment @r{[}@var{varname}@r{]}
2130 Print the value of environment variable @var{varname} to be given to
2131 your program when it starts. If you do not supply @var{varname},
2132 print the names and values of all environment variables to be given to
2133 your program. You can abbreviate @code{environment} as @code{env}.
2135 @kindex set environment
2136 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2137 Set environment variable @var{varname} to @var{value}. The value
2138 changes for your program only, not for @value{GDBN} itself. @var{value} may
2139 be any string; the values of environment variables are just strings, and
2140 any interpretation is supplied by your program itself. The @var{value}
2141 parameter is optional; if it is eliminated, the variable is set to a
2143 @c "any string" here does not include leading, trailing
2144 @c blanks. Gnu asks: does anyone care?
2146 For example, this command:
2153 tells the debugged program, when subsequently run, that its user is named
2154 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2155 are not actually required.)
2157 @kindex unset environment
2158 @item unset environment @var{varname}
2159 Remove variable @var{varname} from the environment to be passed to your
2160 program. This is different from @samp{set env @var{varname} =};
2161 @code{unset environment} removes the variable from the environment,
2162 rather than assigning it an empty value.
2165 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2167 by your @code{SHELL} environment variable if it exists (or
2168 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2169 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2170 @file{.bashrc} for BASH---any variables you set in that file affect
2171 your program. You may wish to move setting of environment variables to
2172 files that are only run when you sign on, such as @file{.login} or
2175 @node Working Directory
2176 @section Your Program's Working Directory
2178 @cindex working directory (of your program)
2179 Each time you start your program with @code{run}, it inherits its
2180 working directory from the current working directory of @value{GDBN}.
2181 The @value{GDBN} working directory is initially whatever it inherited
2182 from its parent process (typically the shell), but you can specify a new
2183 working directory in @value{GDBN} with the @code{cd} command.
2185 The @value{GDBN} working directory also serves as a default for the commands
2186 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2191 @cindex change working directory
2192 @item cd @var{directory}
2193 Set the @value{GDBN} working directory to @var{directory}.
2197 Print the @value{GDBN} working directory.
2200 It is generally impossible to find the current working directory of
2201 the process being debugged (since a program can change its directory
2202 during its run). If you work on a system where @value{GDBN} is
2203 configured with the @file{/proc} support, you can use the @code{info
2204 proc} command (@pxref{SVR4 Process Information}) to find out the
2205 current working directory of the debuggee.
2208 @section Your Program's Input and Output
2213 By default, the program you run under @value{GDBN} does input and output to
2214 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2215 to its own terminal modes to interact with you, but it records the terminal
2216 modes your program was using and switches back to them when you continue
2217 running your program.
2220 @kindex info terminal
2222 Displays information recorded by @value{GDBN} about the terminal modes your
2226 You can redirect your program's input and/or output using shell
2227 redirection with the @code{run} command. For example,
2234 starts your program, diverting its output to the file @file{outfile}.
2237 @cindex controlling terminal
2238 Another way to specify where your program should do input and output is
2239 with the @code{tty} command. This command accepts a file name as
2240 argument, and causes this file to be the default for future @code{run}
2241 commands. It also resets the controlling terminal for the child
2242 process, for future @code{run} commands. For example,
2249 directs that processes started with subsequent @code{run} commands
2250 default to do input and output on the terminal @file{/dev/ttyb} and have
2251 that as their controlling terminal.
2253 An explicit redirection in @code{run} overrides the @code{tty} command's
2254 effect on the input/output device, but not its effect on the controlling
2257 When you use the @code{tty} command or redirect input in the @code{run}
2258 command, only the input @emph{for your program} is affected. The input
2259 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2260 for @code{set inferior-tty}.
2262 @cindex inferior tty
2263 @cindex set inferior controlling terminal
2264 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2265 display the name of the terminal that will be used for future runs of your
2269 @item set inferior-tty /dev/ttyb
2270 @kindex set inferior-tty
2271 Set the tty for the program being debugged to /dev/ttyb.
2273 @item show inferior-tty
2274 @kindex show inferior-tty
2275 Show the current tty for the program being debugged.
2279 @section Debugging an Already-running Process
2284 @item attach @var{process-id}
2285 This command attaches to a running process---one that was started
2286 outside @value{GDBN}. (@code{info files} shows your active
2287 targets.) The command takes as argument a process ID. The usual way to
2288 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2289 or with the @samp{jobs -l} shell command.
2291 @code{attach} does not repeat if you press @key{RET} a second time after
2292 executing the command.
2295 To use @code{attach}, your program must be running in an environment
2296 which supports processes; for example, @code{attach} does not work for
2297 programs on bare-board targets that lack an operating system. You must
2298 also have permission to send the process a signal.
2300 When you use @code{attach}, the debugger finds the program running in
2301 the process first by looking in the current working directory, then (if
2302 the program is not found) by using the source file search path
2303 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2304 the @code{file} command to load the program. @xref{Files, ,Commands to
2307 The first thing @value{GDBN} does after arranging to debug the specified
2308 process is to stop it. You can examine and modify an attached process
2309 with all the @value{GDBN} commands that are ordinarily available when
2310 you start processes with @code{run}. You can insert breakpoints; you
2311 can step and continue; you can modify storage. If you would rather the
2312 process continue running, you may use the @code{continue} command after
2313 attaching @value{GDBN} to the process.
2318 When you have finished debugging the attached process, you can use the
2319 @code{detach} command to release it from @value{GDBN} control. Detaching
2320 the process continues its execution. After the @code{detach} command,
2321 that process and @value{GDBN} become completely independent once more, and you
2322 are ready to @code{attach} another process or start one with @code{run}.
2323 @code{detach} does not repeat if you press @key{RET} again after
2324 executing the command.
2327 If you exit @value{GDBN} while you have an attached process, you detach
2328 that process. If you use the @code{run} command, you kill that process.
2329 By default, @value{GDBN} asks for confirmation if you try to do either of these
2330 things; you can control whether or not you need to confirm by using the
2331 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2335 @section Killing the Child Process
2340 Kill the child process in which your program is running under @value{GDBN}.
2343 This command is useful if you wish to debug a core dump instead of a
2344 running process. @value{GDBN} ignores any core dump file while your program
2347 On some operating systems, a program cannot be executed outside @value{GDBN}
2348 while you have breakpoints set on it inside @value{GDBN}. You can use the
2349 @code{kill} command in this situation to permit running your program
2350 outside the debugger.
2352 The @code{kill} command is also useful if you wish to recompile and
2353 relink your program, since on many systems it is impossible to modify an
2354 executable file while it is running in a process. In this case, when you
2355 next type @code{run}, @value{GDBN} notices that the file has changed, and
2356 reads the symbol table again (while trying to preserve your current
2357 breakpoint settings).
2359 @node Inferiors and Programs
2360 @section Debugging Multiple Inferiors and Programs
2362 @value{GDBN} lets you run and debug multiple programs in a single
2363 session. In addition, @value{GDBN} on some systems may let you run
2364 several programs simultaneously (otherwise you have to exit from one
2365 before starting another). In the most general case, you can have
2366 multiple threads of execution in each of multiple processes, launched
2367 from multiple executables.
2370 @value{GDBN} represents the state of each program execution with an
2371 object called an @dfn{inferior}. An inferior typically corresponds to
2372 a process, but is more general and applies also to targets that do not
2373 have processes. Inferiors may be created before a process runs, and
2374 may be retained after a process exits. Inferiors have unique
2375 identifiers that are different from process ids. Usually each
2376 inferior will also have its own distinct address space, although some
2377 embedded targets may have several inferiors running in different parts
2378 of a single address space. Each inferior may in turn have multiple
2379 threads running in it.
2381 To find out what inferiors exist at any moment, use @w{@code{info
2385 @kindex info inferiors
2386 @item info inferiors
2387 Print a list of all inferiors currently being managed by @value{GDBN}.
2389 @value{GDBN} displays for each inferior (in this order):
2393 the inferior number assigned by @value{GDBN}
2396 the target system's inferior identifier
2399 the name of the executable the inferior is running.
2404 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2405 indicates the current inferior.
2409 @c end table here to get a little more width for example
2412 (@value{GDBP}) info inferiors
2413 Num Description Executable
2414 2 process 2307 hello
2415 * 1 process 3401 goodbye
2418 To switch focus between inferiors, use the @code{inferior} command:
2421 @kindex inferior @var{infno}
2422 @item inferior @var{infno}
2423 Make inferior number @var{infno} the current inferior. The argument
2424 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2425 in the first field of the @samp{info inferiors} display.
2429 You can get multiple executables into a debugging session via the
2430 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2431 systems @value{GDBN} can add inferiors to the debug session
2432 automatically by following calls to @code{fork} and @code{exec}. To
2433 remove inferiors from the debugging session use the
2434 @w{@code{remove-inferior}} command.
2437 @kindex add-inferior
2438 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2439 Adds @var{n} inferiors to be run using @var{executable} as the
2440 executable. @var{n} defaults to 1. If no executable is specified,
2441 the inferiors begins empty, with no program. You can still assign or
2442 change the program assigned to the inferior at any time by using the
2443 @code{file} command with the executable name as its argument.
2445 @kindex clone-inferior
2446 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2447 Adds @var{n} inferiors ready to execute the same program as inferior
2448 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2449 number of the current inferior. This is a convenient command when you
2450 want to run another instance of the inferior you are debugging.
2453 (@value{GDBP}) info inferiors
2454 Num Description Executable
2455 * 1 process 29964 helloworld
2456 (@value{GDBP}) clone-inferior
2459 (@value{GDBP}) info inferiors
2460 Num Description Executable
2462 * 1 process 29964 helloworld
2465 You can now simply switch focus to inferior 2 and run it.
2467 @kindex remove-inferior
2468 @item remove-inferior @var{infno}
2469 Removes the inferior @var{infno}. It is not possible to remove an
2470 inferior that is running with this command. For those, use the
2471 @code{kill} or @code{detach} command first.
2475 To quit debugging one of the running inferiors that is not the current
2476 inferior, you can either detach from it by using the @w{@code{detach
2477 inferior}} command (allowing it to run independently), or kill it
2478 using the @w{@code{kill inferior}} command:
2481 @kindex detach inferior @var{infno}
2482 @item detach inferior @var{infno}
2483 Detach from the inferior identified by @value{GDBN} inferior number
2484 @var{infno}. Note that the inferior's entry still stays on the list
2485 of inferiors shown by @code{info inferiors}, but its Description will
2488 @kindex kill inferior @var{infno}
2489 @item kill inferior @var{infno}
2490 Kill the inferior identified by @value{GDBN} inferior number
2491 @var{infno}. Note that the inferior's entry still stays on the list
2492 of inferiors shown by @code{info inferiors}, but its Description will
2496 After the successful completion of a command such as @code{detach},
2497 @code{detach inferior}, @code{kill} or @code{kill inferior}, or after
2498 a normal process exit, the inferior is still valid and listed with
2499 @code{info inferiors}, ready to be restarted.
2502 To be notified when inferiors are started or exit under @value{GDBN}'s
2503 control use @w{@code{set print inferior-events}}:
2506 @kindex set print inferior-events
2507 @cindex print messages on inferior start and exit
2508 @item set print inferior-events
2509 @itemx set print inferior-events on
2510 @itemx set print inferior-events off
2511 The @code{set print inferior-events} command allows you to enable or
2512 disable printing of messages when @value{GDBN} notices that new
2513 inferiors have started or that inferiors have exited or have been
2514 detached. By default, these messages will not be printed.
2516 @kindex show print inferior-events
2517 @item show print inferior-events
2518 Show whether messages will be printed when @value{GDBN} detects that
2519 inferiors have started, exited or have been detached.
2522 Many commands will work the same with multiple programs as with a
2523 single program: e.g., @code{print myglobal} will simply display the
2524 value of @code{myglobal} in the current inferior.
2527 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2528 get more info about the relationship of inferiors, programs, address
2529 spaces in a debug session. You can do that with the @w{@code{maint
2530 info program-spaces}} command.
2533 @kindex maint info program-spaces
2534 @item maint info program-spaces
2535 Print a list of all program spaces currently being managed by
2538 @value{GDBN} displays for each program space (in this order):
2542 the program space number assigned by @value{GDBN}
2545 the name of the executable loaded into the program space, with e.g.,
2546 the @code{file} command.
2551 An asterisk @samp{*} preceding the @value{GDBN} program space number
2552 indicates the current program space.
2554 In addition, below each program space line, @value{GDBN} prints extra
2555 information that isn't suitable to display in tabular form. For
2556 example, the list of inferiors bound to the program space.
2559 (@value{GDBP}) maint info program-spaces
2562 Bound inferiors: ID 1 (process 21561)
2566 Here we can see that no inferior is running the program @code{hello},
2567 while @code{process 21561} is running the program @code{goodbye}. On
2568 some targets, it is possible that multiple inferiors are bound to the
2569 same program space. The most common example is that of debugging both
2570 the parent and child processes of a @code{vfork} call. For example,
2573 (@value{GDBP}) maint info program-spaces
2576 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2579 Here, both inferior 2 and inferior 1 are running in the same program
2580 space as a result of inferior 1 having executed a @code{vfork} call.
2584 @section Debugging Programs with Multiple Threads
2586 @cindex threads of execution
2587 @cindex multiple threads
2588 @cindex switching threads
2589 In some operating systems, such as HP-UX and Solaris, a single program
2590 may have more than one @dfn{thread} of execution. The precise semantics
2591 of threads differ from one operating system to another, but in general
2592 the threads of a single program are akin to multiple processes---except
2593 that they share one address space (that is, they can all examine and
2594 modify the same variables). On the other hand, each thread has its own
2595 registers and execution stack, and perhaps private memory.
2597 @value{GDBN} provides these facilities for debugging multi-thread
2601 @item automatic notification of new threads
2602 @item @samp{thread @var{threadno}}, a command to switch among threads
2603 @item @samp{info threads}, a command to inquire about existing threads
2604 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2605 a command to apply a command to a list of threads
2606 @item thread-specific breakpoints
2607 @item @samp{set print thread-events}, which controls printing of
2608 messages on thread start and exit.
2609 @item @samp{set libthread-db-search-path @var{path}}, which lets
2610 the user specify which @code{libthread_db} to use if the default choice
2611 isn't compatible with the program.
2615 @emph{Warning:} These facilities are not yet available on every
2616 @value{GDBN} configuration where the operating system supports threads.
2617 If your @value{GDBN} does not support threads, these commands have no
2618 effect. For example, a system without thread support shows no output
2619 from @samp{info threads}, and always rejects the @code{thread} command,
2623 (@value{GDBP}) info threads
2624 (@value{GDBP}) thread 1
2625 Thread ID 1 not known. Use the "info threads" command to
2626 see the IDs of currently known threads.
2628 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2629 @c doesn't support threads"?
2632 @cindex focus of debugging
2633 @cindex current thread
2634 The @value{GDBN} thread debugging facility allows you to observe all
2635 threads while your program runs---but whenever @value{GDBN} takes
2636 control, one thread in particular is always the focus of debugging.
2637 This thread is called the @dfn{current thread}. Debugging commands show
2638 program information from the perspective of the current thread.
2640 @cindex @code{New} @var{systag} message
2641 @cindex thread identifier (system)
2642 @c FIXME-implementors!! It would be more helpful if the [New...] message
2643 @c included GDB's numeric thread handle, so you could just go to that
2644 @c thread without first checking `info threads'.
2645 Whenever @value{GDBN} detects a new thread in your program, it displays
2646 the target system's identification for the thread with a message in the
2647 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2648 whose form varies depending on the particular system. For example, on
2649 @sc{gnu}/Linux, you might see
2652 [New Thread 46912507313328 (LWP 25582)]
2656 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2657 the @var{systag} is simply something like @samp{process 368}, with no
2660 @c FIXME!! (1) Does the [New...] message appear even for the very first
2661 @c thread of a program, or does it only appear for the
2662 @c second---i.e.@: when it becomes obvious we have a multithread
2664 @c (2) *Is* there necessarily a first thread always? Or do some
2665 @c multithread systems permit starting a program with multiple
2666 @c threads ab initio?
2668 @cindex thread number
2669 @cindex thread identifier (GDB)
2670 For debugging purposes, @value{GDBN} associates its own thread
2671 number---always a single integer---with each thread in your program.
2674 @kindex info threads
2676 Display a summary of all threads currently in your
2677 program. @value{GDBN} displays for each thread (in this order):
2681 the thread number assigned by @value{GDBN}
2684 the target system's thread identifier (@var{systag})
2687 the current stack frame summary for that thread
2691 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2692 indicates the current thread.
2696 @c end table here to get a little more width for example
2699 (@value{GDBP}) info threads
2700 3 process 35 thread 27 0x34e5 in sigpause ()
2701 2 process 35 thread 23 0x34e5 in sigpause ()
2702 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2708 @cindex debugging multithreaded programs (on HP-UX)
2709 @cindex thread identifier (GDB), on HP-UX
2710 For debugging purposes, @value{GDBN} associates its own thread
2711 number---a small integer assigned in thread-creation order---with each
2712 thread in your program.
2714 @cindex @code{New} @var{systag} message, on HP-UX
2715 @cindex thread identifier (system), on HP-UX
2716 @c FIXME-implementors!! It would be more helpful if the [New...] message
2717 @c included GDB's numeric thread handle, so you could just go to that
2718 @c thread without first checking `info threads'.
2719 Whenever @value{GDBN} detects a new thread in your program, it displays
2720 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2721 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2722 whose form varies depending on the particular system. For example, on
2726 [New thread 2 (system thread 26594)]
2730 when @value{GDBN} notices a new thread.
2733 @kindex info threads (HP-UX)
2735 Display a summary of all threads currently in your
2736 program. @value{GDBN} displays for each thread (in this order):
2739 @item the thread number assigned by @value{GDBN}
2741 @item the target system's thread identifier (@var{systag})
2743 @item the current stack frame summary for that thread
2747 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2748 indicates the current thread.
2752 @c end table here to get a little more width for example
2755 (@value{GDBP}) info threads
2756 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2758 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2759 from /usr/lib/libc.2
2760 1 system thread 27905 0x7b003498 in _brk () \@*
2761 from /usr/lib/libc.2
2764 On Solaris, you can display more information about user threads with a
2765 Solaris-specific command:
2768 @item maint info sol-threads
2769 @kindex maint info sol-threads
2770 @cindex thread info (Solaris)
2771 Display info on Solaris user threads.
2775 @kindex thread @var{threadno}
2776 @item thread @var{threadno}
2777 Make thread number @var{threadno} the current thread. The command
2778 argument @var{threadno} is the internal @value{GDBN} thread number, as
2779 shown in the first field of the @samp{info threads} display.
2780 @value{GDBN} responds by displaying the system identifier of the thread
2781 you selected, and its current stack frame summary:
2784 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2785 (@value{GDBP}) thread 2
2786 [Switching to process 35 thread 23]
2787 0x34e5 in sigpause ()
2791 As with the @samp{[New @dots{}]} message, the form of the text after
2792 @samp{Switching to} depends on your system's conventions for identifying
2795 @vindex $_thread@r{, convenience variable}
2796 The debugger convenience variable @samp{$_thread} contains the number
2797 of the current thread. You may find this useful in writing breakpoint
2798 conditional expressions, command scripts, and so forth. See
2799 @xref{Convenience Vars,, Convenience Variables}, for general
2800 information on convenience variables.
2802 @kindex thread apply
2803 @cindex apply command to several threads
2804 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2805 The @code{thread apply} command allows you to apply the named
2806 @var{command} to one or more threads. Specify the numbers of the
2807 threads that you want affected with the command argument
2808 @var{threadno}. It can be a single thread number, one of the numbers
2809 shown in the first field of the @samp{info threads} display; or it
2810 could be a range of thread numbers, as in @code{2-4}. To apply a
2811 command to all threads, type @kbd{thread apply all @var{command}}.
2813 @kindex set print thread-events
2814 @cindex print messages on thread start and exit
2815 @item set print thread-events
2816 @itemx set print thread-events on
2817 @itemx set print thread-events off
2818 The @code{set print thread-events} command allows you to enable or
2819 disable printing of messages when @value{GDBN} notices that new threads have
2820 started or that threads have exited. By default, these messages will
2821 be printed if detection of these events is supported by the target.
2822 Note that these messages cannot be disabled on all targets.
2824 @kindex show print thread-events
2825 @item show print thread-events
2826 Show whether messages will be printed when @value{GDBN} detects that threads
2827 have started and exited.
2830 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2831 more information about how @value{GDBN} behaves when you stop and start
2832 programs with multiple threads.
2834 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2835 watchpoints in programs with multiple threads.
2838 @kindex set libthread-db-search-path
2839 @cindex search path for @code{libthread_db}
2840 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2841 If this variable is set, @var{path} is a colon-separated list of
2842 directories @value{GDBN} will use to search for @code{libthread_db}.
2843 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2846 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2847 @code{libthread_db} library to obtain information about threads in the
2848 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2849 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2850 with default system shared library directories, and finally the directory
2851 from which @code{libpthread} was loaded in the inferior process.
2853 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2854 @value{GDBN} attempts to initialize it with the current inferior process.
2855 If this initialization fails (which could happen because of a version
2856 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2857 will unload @code{libthread_db}, and continue with the next directory.
2858 If none of @code{libthread_db} libraries initialize successfully,
2859 @value{GDBN} will issue a warning and thread debugging will be disabled.
2861 Setting @code{libthread-db-search-path} is currently implemented
2862 only on some platforms.
2864 @kindex show libthread-db-search-path
2865 @item show libthread-db-search-path
2866 Display current libthread_db search path.
2868 @kindex set debug libthread-db
2869 @kindex show debug libthread-db
2870 @cindex debugging @code{libthread_db}
2871 @item set debug libthread-db
2872 @itemx show debug libthread-db
2873 Turns on or off display of @code{libthread_db}-related events.
2874 Use @code{1} to enable, @code{0} to disable.
2878 @section Debugging Forks
2880 @cindex fork, debugging programs which call
2881 @cindex multiple processes
2882 @cindex processes, multiple
2883 On most systems, @value{GDBN} has no special support for debugging
2884 programs which create additional processes using the @code{fork}
2885 function. When a program forks, @value{GDBN} will continue to debug the
2886 parent process and the child process will run unimpeded. If you have
2887 set a breakpoint in any code which the child then executes, the child
2888 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2889 will cause it to terminate.
2891 However, if you want to debug the child process there is a workaround
2892 which isn't too painful. Put a call to @code{sleep} in the code which
2893 the child process executes after the fork. It may be useful to sleep
2894 only if a certain environment variable is set, or a certain file exists,
2895 so that the delay need not occur when you don't want to run @value{GDBN}
2896 on the child. While the child is sleeping, use the @code{ps} program to
2897 get its process ID. Then tell @value{GDBN} (a new invocation of
2898 @value{GDBN} if you are also debugging the parent process) to attach to
2899 the child process (@pxref{Attach}). From that point on you can debug
2900 the child process just like any other process which you attached to.
2902 On some systems, @value{GDBN} provides support for debugging programs that
2903 create additional processes using the @code{fork} or @code{vfork} functions.
2904 Currently, the only platforms with this feature are HP-UX (11.x and later
2905 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2907 By default, when a program forks, @value{GDBN} will continue to debug
2908 the parent process and the child process will run unimpeded.
2910 If you want to follow the child process instead of the parent process,
2911 use the command @w{@code{set follow-fork-mode}}.
2914 @kindex set follow-fork-mode
2915 @item set follow-fork-mode @var{mode}
2916 Set the debugger response to a program call of @code{fork} or
2917 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2918 process. The @var{mode} argument can be:
2922 The original process is debugged after a fork. The child process runs
2923 unimpeded. This is the default.
2926 The new process is debugged after a fork. The parent process runs
2931 @kindex show follow-fork-mode
2932 @item show follow-fork-mode
2933 Display the current debugger response to a @code{fork} or @code{vfork} call.
2936 @cindex debugging multiple processes
2937 On Linux, if you want to debug both the parent and child processes, use the
2938 command @w{@code{set detach-on-fork}}.
2941 @kindex set detach-on-fork
2942 @item set detach-on-fork @var{mode}
2943 Tells gdb whether to detach one of the processes after a fork, or
2944 retain debugger control over them both.
2948 The child process (or parent process, depending on the value of
2949 @code{follow-fork-mode}) will be detached and allowed to run
2950 independently. This is the default.
2953 Both processes will be held under the control of @value{GDBN}.
2954 One process (child or parent, depending on the value of
2955 @code{follow-fork-mode}) is debugged as usual, while the other
2960 @kindex show detach-on-fork
2961 @item show detach-on-fork
2962 Show whether detach-on-fork mode is on/off.
2965 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2966 will retain control of all forked processes (including nested forks).
2967 You can list the forked processes under the control of @value{GDBN} by
2968 using the @w{@code{info inferiors}} command, and switch from one fork
2969 to another by using the @code{inferior} command (@pxref{Inferiors and
2970 Programs, ,Debugging Multiple Inferiors and Programs}).
2972 To quit debugging one of the forked processes, you can either detach
2973 from it by using the @w{@code{detach inferior}} command (allowing it
2974 to run independently), or kill it using the @w{@code{kill inferior}}
2975 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2978 If you ask to debug a child process and a @code{vfork} is followed by an
2979 @code{exec}, @value{GDBN} executes the new target up to the first
2980 breakpoint in the new target. If you have a breakpoint set on
2981 @code{main} in your original program, the breakpoint will also be set on
2982 the child process's @code{main}.
2984 On some systems, when a child process is spawned by @code{vfork}, you
2985 cannot debug the child or parent until an @code{exec} call completes.
2987 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2988 call executes, the new target restarts. To restart the parent
2989 process, use the @code{file} command with the parent executable name
2990 as its argument. By default, after an @code{exec} call executes,
2991 @value{GDBN} discards the symbols of the previous executable image.
2992 You can change this behaviour with the @w{@code{set follow-exec-mode}}
2996 @kindex set follow-exec-mode
2997 @item set follow-exec-mode @var{mode}
2999 Set debugger response to a program call of @code{exec}. An
3000 @code{exec} call replaces the program image of a process.
3002 @code{follow-exec-mode} can be:
3006 @value{GDBN} creates a new inferior and rebinds the process to this
3007 new inferior. The program the process was running before the
3008 @code{exec} call can be restarted afterwards by restarting the
3014 (@value{GDBP}) info inferiors
3016 Id Description Executable
3019 process 12020 is executing new program: prog2
3020 Program exited normally.
3021 (@value{GDBP}) info inferiors
3022 Id Description Executable
3028 @value{GDBN} keeps the process bound to the same inferior. The new
3029 executable image replaces the previous executable loaded in the
3030 inferior. Restarting the inferior after the @code{exec} call, with
3031 e.g., the @code{run} command, restarts the executable the process was
3032 running after the @code{exec} call. This is the default mode.
3037 (@value{GDBP}) info inferiors
3038 Id Description Executable
3041 process 12020 is executing new program: prog2
3042 Program exited normally.
3043 (@value{GDBP}) info inferiors
3044 Id Description Executable
3051 You can use the @code{catch} command to make @value{GDBN} stop whenever
3052 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3053 Catchpoints, ,Setting Catchpoints}.
3055 @node Checkpoint/Restart
3056 @section Setting a @emph{Bookmark} to Return to Later
3061 @cindex snapshot of a process
3062 @cindex rewind program state
3064 On certain operating systems@footnote{Currently, only
3065 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3066 program's state, called a @dfn{checkpoint}, and come back to it
3069 Returning to a checkpoint effectively undoes everything that has
3070 happened in the program since the @code{checkpoint} was saved. This
3071 includes changes in memory, registers, and even (within some limits)
3072 system state. Effectively, it is like going back in time to the
3073 moment when the checkpoint was saved.
3075 Thus, if you're stepping thru a program and you think you're
3076 getting close to the point where things go wrong, you can save
3077 a checkpoint. Then, if you accidentally go too far and miss
3078 the critical statement, instead of having to restart your program
3079 from the beginning, you can just go back to the checkpoint and
3080 start again from there.
3082 This can be especially useful if it takes a lot of time or
3083 steps to reach the point where you think the bug occurs.
3085 To use the @code{checkpoint}/@code{restart} method of debugging:
3090 Save a snapshot of the debugged program's current execution state.
3091 The @code{checkpoint} command takes no arguments, but each checkpoint
3092 is assigned a small integer id, similar to a breakpoint id.
3094 @kindex info checkpoints
3095 @item info checkpoints
3096 List the checkpoints that have been saved in the current debugging
3097 session. For each checkpoint, the following information will be
3104 @item Source line, or label
3107 @kindex restart @var{checkpoint-id}
3108 @item restart @var{checkpoint-id}
3109 Restore the program state that was saved as checkpoint number
3110 @var{checkpoint-id}. All program variables, registers, stack frames
3111 etc.@: will be returned to the values that they had when the checkpoint
3112 was saved. In essence, gdb will ``wind back the clock'' to the point
3113 in time when the checkpoint was saved.
3115 Note that breakpoints, @value{GDBN} variables, command history etc.
3116 are not affected by restoring a checkpoint. In general, a checkpoint
3117 only restores things that reside in the program being debugged, not in
3120 @kindex delete checkpoint @var{checkpoint-id}
3121 @item delete checkpoint @var{checkpoint-id}
3122 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3126 Returning to a previously saved checkpoint will restore the user state
3127 of the program being debugged, plus a significant subset of the system
3128 (OS) state, including file pointers. It won't ``un-write'' data from
3129 a file, but it will rewind the file pointer to the previous location,
3130 so that the previously written data can be overwritten. For files
3131 opened in read mode, the pointer will also be restored so that the
3132 previously read data can be read again.
3134 Of course, characters that have been sent to a printer (or other
3135 external device) cannot be ``snatched back'', and characters received
3136 from eg.@: a serial device can be removed from internal program buffers,
3137 but they cannot be ``pushed back'' into the serial pipeline, ready to
3138 be received again. Similarly, the actual contents of files that have
3139 been changed cannot be restored (at this time).
3141 However, within those constraints, you actually can ``rewind'' your
3142 program to a previously saved point in time, and begin debugging it
3143 again --- and you can change the course of events so as to debug a
3144 different execution path this time.
3146 @cindex checkpoints and process id
3147 Finally, there is one bit of internal program state that will be
3148 different when you return to a checkpoint --- the program's process
3149 id. Each checkpoint will have a unique process id (or @var{pid}),
3150 and each will be different from the program's original @var{pid}.
3151 If your program has saved a local copy of its process id, this could
3152 potentially pose a problem.
3154 @subsection A Non-obvious Benefit of Using Checkpoints
3156 On some systems such as @sc{gnu}/Linux, address space randomization
3157 is performed on new processes for security reasons. This makes it
3158 difficult or impossible to set a breakpoint, or watchpoint, on an
3159 absolute address if you have to restart the program, since the
3160 absolute location of a symbol will change from one execution to the
3163 A checkpoint, however, is an @emph{identical} copy of a process.
3164 Therefore if you create a checkpoint at (eg.@:) the start of main,
3165 and simply return to that checkpoint instead of restarting the
3166 process, you can avoid the effects of address randomization and
3167 your symbols will all stay in the same place.
3170 @chapter Stopping and Continuing
3172 The principal purposes of using a debugger are so that you can stop your
3173 program before it terminates; or so that, if your program runs into
3174 trouble, you can investigate and find out why.
3176 Inside @value{GDBN}, your program may stop for any of several reasons,
3177 such as a signal, a breakpoint, or reaching a new line after a
3178 @value{GDBN} command such as @code{step}. You may then examine and
3179 change variables, set new breakpoints or remove old ones, and then
3180 continue execution. Usually, the messages shown by @value{GDBN} provide
3181 ample explanation of the status of your program---but you can also
3182 explicitly request this information at any time.
3185 @kindex info program
3187 Display information about the status of your program: whether it is
3188 running or not, what process it is, and why it stopped.
3192 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3193 * Continuing and Stepping:: Resuming execution
3195 * Thread Stops:: Stopping and starting multi-thread programs
3199 @section Breakpoints, Watchpoints, and Catchpoints
3202 A @dfn{breakpoint} makes your program stop whenever a certain point in
3203 the program is reached. For each breakpoint, you can add conditions to
3204 control in finer detail whether your program stops. You can set
3205 breakpoints with the @code{break} command and its variants (@pxref{Set
3206 Breaks, ,Setting Breakpoints}), to specify the place where your program
3207 should stop by line number, function name or exact address in the
3210 On some systems, you can set breakpoints in shared libraries before
3211 the executable is run. There is a minor limitation on HP-UX systems:
3212 you must wait until the executable is run in order to set breakpoints
3213 in shared library routines that are not called directly by the program
3214 (for example, routines that are arguments in a @code{pthread_create}
3218 @cindex data breakpoints
3219 @cindex memory tracing
3220 @cindex breakpoint on memory address
3221 @cindex breakpoint on variable modification
3222 A @dfn{watchpoint} is a special breakpoint that stops your program
3223 when the value of an expression changes. The expression may be a value
3224 of a variable, or it could involve values of one or more variables
3225 combined by operators, such as @samp{a + b}. This is sometimes called
3226 @dfn{data breakpoints}. You must use a different command to set
3227 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3228 from that, you can manage a watchpoint like any other breakpoint: you
3229 enable, disable, and delete both breakpoints and watchpoints using the
3232 You can arrange to have values from your program displayed automatically
3233 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3237 @cindex breakpoint on events
3238 A @dfn{catchpoint} is another special breakpoint that stops your program
3239 when a certain kind of event occurs, such as the throwing of a C@t{++}
3240 exception or the loading of a library. As with watchpoints, you use a
3241 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3242 Catchpoints}), but aside from that, you can manage a catchpoint like any
3243 other breakpoint. (To stop when your program receives a signal, use the
3244 @code{handle} command; see @ref{Signals, ,Signals}.)
3246 @cindex breakpoint numbers
3247 @cindex numbers for breakpoints
3248 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3249 catchpoint when you create it; these numbers are successive integers
3250 starting with one. In many of the commands for controlling various
3251 features of breakpoints you use the breakpoint number to say which
3252 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3253 @dfn{disabled}; if disabled, it has no effect on your program until you
3256 @cindex breakpoint ranges
3257 @cindex ranges of breakpoints
3258 Some @value{GDBN} commands accept a range of breakpoints on which to
3259 operate. A breakpoint range is either a single breakpoint number, like
3260 @samp{5}, or two such numbers, in increasing order, separated by a
3261 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3262 all breakpoints in that range are operated on.
3265 * Set Breaks:: Setting breakpoints
3266 * Set Watchpoints:: Setting watchpoints
3267 * Set Catchpoints:: Setting catchpoints
3268 * Delete Breaks:: Deleting breakpoints
3269 * Disabling:: Disabling breakpoints
3270 * Conditions:: Break conditions
3271 * Break Commands:: Breakpoint command lists
3272 * Save Breakpoints:: How to save breakpoints in a file
3273 * Error in Breakpoints:: ``Cannot insert breakpoints''
3274 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3278 @subsection Setting Breakpoints
3280 @c FIXME LMB what does GDB do if no code on line of breakpt?
3281 @c consider in particular declaration with/without initialization.
3283 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3286 @kindex b @r{(@code{break})}
3287 @vindex $bpnum@r{, convenience variable}
3288 @cindex latest breakpoint
3289 Breakpoints are set with the @code{break} command (abbreviated
3290 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3291 number of the breakpoint you've set most recently; see @ref{Convenience
3292 Vars,, Convenience Variables}, for a discussion of what you can do with
3293 convenience variables.
3296 @item break @var{location}
3297 Set a breakpoint at the given @var{location}, which can specify a
3298 function name, a line number, or an address of an instruction.
3299 (@xref{Specify Location}, for a list of all the possible ways to
3300 specify a @var{location}.) The breakpoint will stop your program just
3301 before it executes any of the code in the specified @var{location}.
3303 When using source languages that permit overloading of symbols, such as
3304 C@t{++}, a function name may refer to more than one possible place to break.
3305 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3308 It is also possible to insert a breakpoint that will stop the program
3309 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3310 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3313 When called without any arguments, @code{break} sets a breakpoint at
3314 the next instruction to be executed in the selected stack frame
3315 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3316 innermost, this makes your program stop as soon as control
3317 returns to that frame. This is similar to the effect of a
3318 @code{finish} command in the frame inside the selected frame---except
3319 that @code{finish} does not leave an active breakpoint. If you use
3320 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3321 the next time it reaches the current location; this may be useful
3324 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3325 least one instruction has been executed. If it did not do this, you
3326 would be unable to proceed past a breakpoint without first disabling the
3327 breakpoint. This rule applies whether or not the breakpoint already
3328 existed when your program stopped.
3330 @item break @dots{} if @var{cond}
3331 Set a breakpoint with condition @var{cond}; evaluate the expression
3332 @var{cond} each time the breakpoint is reached, and stop only if the
3333 value is nonzero---that is, if @var{cond} evaluates as true.
3334 @samp{@dots{}} stands for one of the possible arguments described
3335 above (or no argument) specifying where to break. @xref{Conditions,
3336 ,Break Conditions}, for more information on breakpoint conditions.
3339 @item tbreak @var{args}
3340 Set a breakpoint enabled only for one stop. @var{args} are the
3341 same as for the @code{break} command, and the breakpoint is set in the same
3342 way, but the breakpoint is automatically deleted after the first time your
3343 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3346 @cindex hardware breakpoints
3347 @item hbreak @var{args}
3348 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3349 @code{break} command and the breakpoint is set in the same way, but the
3350 breakpoint requires hardware support and some target hardware may not
3351 have this support. The main purpose of this is EPROM/ROM code
3352 debugging, so you can set a breakpoint at an instruction without
3353 changing the instruction. This can be used with the new trap-generation
3354 provided by SPARClite DSU and most x86-based targets. These targets
3355 will generate traps when a program accesses some data or instruction
3356 address that is assigned to the debug registers. However the hardware
3357 breakpoint registers can take a limited number of breakpoints. For
3358 example, on the DSU, only two data breakpoints can be set at a time, and
3359 @value{GDBN} will reject this command if more than two are used. Delete
3360 or disable unused hardware breakpoints before setting new ones
3361 (@pxref{Disabling, ,Disabling Breakpoints}).
3362 @xref{Conditions, ,Break Conditions}.
3363 For remote targets, you can restrict the number of hardware
3364 breakpoints @value{GDBN} will use, see @ref{set remote
3365 hardware-breakpoint-limit}.
3368 @item thbreak @var{args}
3369 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3370 are the same as for the @code{hbreak} command and the breakpoint is set in
3371 the same way. However, like the @code{tbreak} command,
3372 the breakpoint is automatically deleted after the
3373 first time your program stops there. Also, like the @code{hbreak}
3374 command, the breakpoint requires hardware support and some target hardware
3375 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3376 See also @ref{Conditions, ,Break Conditions}.
3379 @cindex regular expression
3380 @cindex breakpoints at functions matching a regexp
3381 @cindex set breakpoints in many functions
3382 @item rbreak @var{regex}
3383 Set breakpoints on all functions matching the regular expression
3384 @var{regex}. This command sets an unconditional breakpoint on all
3385 matches, printing a list of all breakpoints it set. Once these
3386 breakpoints are set, they are treated just like the breakpoints set with
3387 the @code{break} command. You can delete them, disable them, or make
3388 them conditional the same way as any other breakpoint.
3390 The syntax of the regular expression is the standard one used with tools
3391 like @file{grep}. Note that this is different from the syntax used by
3392 shells, so for instance @code{foo*} matches all functions that include
3393 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3394 @code{.*} leading and trailing the regular expression you supply, so to
3395 match only functions that begin with @code{foo}, use @code{^foo}.
3397 @cindex non-member C@t{++} functions, set breakpoint in
3398 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3399 breakpoints on overloaded functions that are not members of any special
3402 @cindex set breakpoints on all functions
3403 The @code{rbreak} command can be used to set breakpoints in
3404 @strong{all} the functions in a program, like this:
3407 (@value{GDBP}) rbreak .
3410 @item rbreak @var{file}:@var{regex}
3411 If @code{rbreak} is called with a filename qualification, it limits
3412 the search for functions matching the given regular expression to the
3413 specified @var{file}. This can be used, for example, to set breakpoints on
3414 every function in a given file:
3417 (@value{GDBP}) rbreak file.c:.
3420 The colon separating the filename qualifier from the regex may
3421 optionally be surrounded by spaces.
3423 @kindex info breakpoints
3424 @cindex @code{$_} and @code{info breakpoints}
3425 @item info breakpoints @r{[}@var{n}@r{]}
3426 @itemx info break @r{[}@var{n}@r{]}
3427 Print a table of all breakpoints, watchpoints, and catchpoints set and
3428 not deleted. Optional argument @var{n} means print information only
3429 about the specified breakpoint (or watchpoint or catchpoint). For
3430 each breakpoint, following columns are printed:
3433 @item Breakpoint Numbers
3435 Breakpoint, watchpoint, or catchpoint.
3437 Whether the breakpoint is marked to be disabled or deleted when hit.
3438 @item Enabled or Disabled
3439 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3440 that are not enabled.
3442 Where the breakpoint is in your program, as a memory address. For a
3443 pending breakpoint whose address is not yet known, this field will
3444 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3445 library that has the symbol or line referred by breakpoint is loaded.
3446 See below for details. A breakpoint with several locations will
3447 have @samp{<MULTIPLE>} in this field---see below for details.
3449 Where the breakpoint is in the source for your program, as a file and
3450 line number. For a pending breakpoint, the original string passed to
3451 the breakpoint command will be listed as it cannot be resolved until
3452 the appropriate shared library is loaded in the future.
3456 If a breakpoint is conditional, @code{info break} shows the condition on
3457 the line following the affected breakpoint; breakpoint commands, if any,
3458 are listed after that. A pending breakpoint is allowed to have a condition
3459 specified for it. The condition is not parsed for validity until a shared
3460 library is loaded that allows the pending breakpoint to resolve to a
3464 @code{info break} with a breakpoint
3465 number @var{n} as argument lists only that breakpoint. The
3466 convenience variable @code{$_} and the default examining-address for
3467 the @code{x} command are set to the address of the last breakpoint
3468 listed (@pxref{Memory, ,Examining Memory}).
3471 @code{info break} displays a count of the number of times the breakpoint
3472 has been hit. This is especially useful in conjunction with the
3473 @code{ignore} command. You can ignore a large number of breakpoint
3474 hits, look at the breakpoint info to see how many times the breakpoint
3475 was hit, and then run again, ignoring one less than that number. This
3476 will get you quickly to the last hit of that breakpoint.
3479 @value{GDBN} allows you to set any number of breakpoints at the same place in
3480 your program. There is nothing silly or meaningless about this. When
3481 the breakpoints are conditional, this is even useful
3482 (@pxref{Conditions, ,Break Conditions}).
3484 @cindex multiple locations, breakpoints
3485 @cindex breakpoints, multiple locations
3486 It is possible that a breakpoint corresponds to several locations
3487 in your program. Examples of this situation are:
3491 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3492 instances of the function body, used in different cases.
3495 For a C@t{++} template function, a given line in the function can
3496 correspond to any number of instantiations.
3499 For an inlined function, a given source line can correspond to
3500 several places where that function is inlined.
3503 In all those cases, @value{GDBN} will insert a breakpoint at all
3504 the relevant locations@footnote{
3505 As of this writing, multiple-location breakpoints work only if there's
3506 line number information for all the locations. This means that they
3507 will generally not work in system libraries, unless you have debug
3508 info with line numbers for them.}.
3510 A breakpoint with multiple locations is displayed in the breakpoint
3511 table using several rows---one header row, followed by one row for
3512 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3513 address column. The rows for individual locations contain the actual
3514 addresses for locations, and show the functions to which those
3515 locations belong. The number column for a location is of the form
3516 @var{breakpoint-number}.@var{location-number}.
3521 Num Type Disp Enb Address What
3522 1 breakpoint keep y <MULTIPLE>
3524 breakpoint already hit 1 time
3525 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3526 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3529 Each location can be individually enabled or disabled by passing
3530 @var{breakpoint-number}.@var{location-number} as argument to the
3531 @code{enable} and @code{disable} commands. Note that you cannot
3532 delete the individual locations from the list, you can only delete the
3533 entire list of locations that belong to their parent breakpoint (with
3534 the @kbd{delete @var{num}} command, where @var{num} is the number of
3535 the parent breakpoint, 1 in the above example). Disabling or enabling
3536 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3537 that belong to that breakpoint.
3539 @cindex pending breakpoints
3540 It's quite common to have a breakpoint inside a shared library.
3541 Shared libraries can be loaded and unloaded explicitly,
3542 and possibly repeatedly, as the program is executed. To support
3543 this use case, @value{GDBN} updates breakpoint locations whenever
3544 any shared library is loaded or unloaded. Typically, you would
3545 set a breakpoint in a shared library at the beginning of your
3546 debugging session, when the library is not loaded, and when the
3547 symbols from the library are not available. When you try to set
3548 breakpoint, @value{GDBN} will ask you if you want to set
3549 a so called @dfn{pending breakpoint}---breakpoint whose address
3550 is not yet resolved.
3552 After the program is run, whenever a new shared library is loaded,
3553 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3554 shared library contains the symbol or line referred to by some
3555 pending breakpoint, that breakpoint is resolved and becomes an
3556 ordinary breakpoint. When a library is unloaded, all breakpoints
3557 that refer to its symbols or source lines become pending again.
3559 This logic works for breakpoints with multiple locations, too. For
3560 example, if you have a breakpoint in a C@t{++} template function, and
3561 a newly loaded shared library has an instantiation of that template,
3562 a new location is added to the list of locations for the breakpoint.
3564 Except for having unresolved address, pending breakpoints do not
3565 differ from regular breakpoints. You can set conditions or commands,
3566 enable and disable them and perform other breakpoint operations.
3568 @value{GDBN} provides some additional commands for controlling what
3569 happens when the @samp{break} command cannot resolve breakpoint
3570 address specification to an address:
3572 @kindex set breakpoint pending
3573 @kindex show breakpoint pending
3575 @item set breakpoint pending auto
3576 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3577 location, it queries you whether a pending breakpoint should be created.
3579 @item set breakpoint pending on
3580 This indicates that an unrecognized breakpoint location should automatically
3581 result in a pending breakpoint being created.
3583 @item set breakpoint pending off
3584 This indicates that pending breakpoints are not to be created. Any
3585 unrecognized breakpoint location results in an error. This setting does
3586 not affect any pending breakpoints previously created.
3588 @item show breakpoint pending
3589 Show the current behavior setting for creating pending breakpoints.
3592 The settings above only affect the @code{break} command and its
3593 variants. Once breakpoint is set, it will be automatically updated
3594 as shared libraries are loaded and unloaded.
3596 @cindex automatic hardware breakpoints
3597 For some targets, @value{GDBN} can automatically decide if hardware or
3598 software breakpoints should be used, depending on whether the
3599 breakpoint address is read-only or read-write. This applies to
3600 breakpoints set with the @code{break} command as well as to internal
3601 breakpoints set by commands like @code{next} and @code{finish}. For
3602 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3605 You can control this automatic behaviour with the following commands::
3607 @kindex set breakpoint auto-hw
3608 @kindex show breakpoint auto-hw
3610 @item set breakpoint auto-hw on
3611 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3612 will try to use the target memory map to decide if software or hardware
3613 breakpoint must be used.
3615 @item set breakpoint auto-hw off
3616 This indicates @value{GDBN} should not automatically select breakpoint
3617 type. If the target provides a memory map, @value{GDBN} will warn when
3618 trying to set software breakpoint at a read-only address.
3621 @value{GDBN} normally implements breakpoints by replacing the program code
3622 at the breakpoint address with a special instruction, which, when
3623 executed, given control to the debugger. By default, the program
3624 code is so modified only when the program is resumed. As soon as
3625 the program stops, @value{GDBN} restores the original instructions. This
3626 behaviour guards against leaving breakpoints inserted in the
3627 target should gdb abrubptly disconnect. However, with slow remote
3628 targets, inserting and removing breakpoint can reduce the performance.
3629 This behavior can be controlled with the following commands::
3631 @kindex set breakpoint always-inserted
3632 @kindex show breakpoint always-inserted
3634 @item set breakpoint always-inserted off
3635 All breakpoints, including newly added by the user, are inserted in
3636 the target only when the target is resumed. All breakpoints are
3637 removed from the target when it stops.
3639 @item set breakpoint always-inserted on
3640 Causes all breakpoints to be inserted in the target at all times. If
3641 the user adds a new breakpoint, or changes an existing breakpoint, the
3642 breakpoints in the target are updated immediately. A breakpoint is
3643 removed from the target only when breakpoint itself is removed.
3645 @cindex non-stop mode, and @code{breakpoint always-inserted}
3646 @item set breakpoint always-inserted auto
3647 This is the default mode. If @value{GDBN} is controlling the inferior
3648 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3649 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3650 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3651 @code{breakpoint always-inserted} mode is off.
3654 @cindex negative breakpoint numbers
3655 @cindex internal @value{GDBN} breakpoints
3656 @value{GDBN} itself sometimes sets breakpoints in your program for
3657 special purposes, such as proper handling of @code{longjmp} (in C
3658 programs). These internal breakpoints are assigned negative numbers,
3659 starting with @code{-1}; @samp{info breakpoints} does not display them.
3660 You can see these breakpoints with the @value{GDBN} maintenance command
3661 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3664 @node Set Watchpoints
3665 @subsection Setting Watchpoints
3667 @cindex setting watchpoints
3668 You can use a watchpoint to stop execution whenever the value of an
3669 expression changes, without having to predict a particular place where
3670 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3671 The expression may be as simple as the value of a single variable, or
3672 as complex as many variables combined by operators. Examples include:
3676 A reference to the value of a single variable.
3679 An address cast to an appropriate data type. For example,
3680 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3681 address (assuming an @code{int} occupies 4 bytes).
3684 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3685 expression can use any operators valid in the program's native
3686 language (@pxref{Languages}).
3689 You can set a watchpoint on an expression even if the expression can
3690 not be evaluated yet. For instance, you can set a watchpoint on
3691 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3692 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3693 the expression produces a valid value. If the expression becomes
3694 valid in some other way than changing a variable (e.g.@: if the memory
3695 pointed to by @samp{*global_ptr} becomes readable as the result of a
3696 @code{malloc} call), @value{GDBN} may not stop until the next time
3697 the expression changes.
3699 @cindex software watchpoints
3700 @cindex hardware watchpoints
3701 Depending on your system, watchpoints may be implemented in software or
3702 hardware. @value{GDBN} does software watchpointing by single-stepping your
3703 program and testing the variable's value each time, which is hundreds of
3704 times slower than normal execution. (But this may still be worth it, to
3705 catch errors where you have no clue what part of your program is the
3708 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3709 x86-based targets, @value{GDBN} includes support for hardware
3710 watchpoints, which do not slow down the running of your program.
3714 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3715 Set a watchpoint for an expression. @value{GDBN} will break when the
3716 expression @var{expr} is written into by the program and its value
3717 changes. The simplest (and the most popular) use of this command is
3718 to watch the value of a single variable:
3721 (@value{GDBP}) watch foo
3724 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3725 clause, @value{GDBN} breaks only when the thread identified by
3726 @var{threadnum} changes the value of @var{expr}. If any other threads
3727 change the value of @var{expr}, @value{GDBN} will not break. Note
3728 that watchpoints restricted to a single thread in this way only work
3729 with Hardware Watchpoints.
3732 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3733 Set a watchpoint that will break when the value of @var{expr} is read
3737 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3738 Set a watchpoint that will break when @var{expr} is either read from
3739 or written into by the program.
3741 @kindex info watchpoints @r{[}@var{n}@r{]}
3742 @item info watchpoints
3743 This command prints a list of watchpoints, using the same format as
3744 @code{info break} (@pxref{Set Breaks}).
3747 If you watch for a change in a numerically entered address you need to
3748 dereference it, as the address itself is just a constant number which will
3749 never change. @value{GDBN} refuses to create a watchpoint that watches
3750 a never-changing value:
3753 (@value{GDBP}) watch 0x600850
3754 Cannot watch constant value 0x600850.
3755 (@value{GDBP}) watch *(int *) 0x600850
3756 Watchpoint 1: *(int *) 6293584
3759 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3760 watchpoints execute very quickly, and the debugger reports a change in
3761 value at the exact instruction where the change occurs. If @value{GDBN}
3762 cannot set a hardware watchpoint, it sets a software watchpoint, which
3763 executes more slowly and reports the change in value at the next
3764 @emph{statement}, not the instruction, after the change occurs.
3766 @cindex use only software watchpoints
3767 You can force @value{GDBN} to use only software watchpoints with the
3768 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3769 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3770 the underlying system supports them. (Note that hardware-assisted
3771 watchpoints that were set @emph{before} setting
3772 @code{can-use-hw-watchpoints} to zero will still use the hardware
3773 mechanism of watching expression values.)
3776 @item set can-use-hw-watchpoints
3777 @kindex set can-use-hw-watchpoints
3778 Set whether or not to use hardware watchpoints.
3780 @item show can-use-hw-watchpoints
3781 @kindex show can-use-hw-watchpoints
3782 Show the current mode of using hardware watchpoints.
3785 For remote targets, you can restrict the number of hardware
3786 watchpoints @value{GDBN} will use, see @ref{set remote
3787 hardware-breakpoint-limit}.
3789 When you issue the @code{watch} command, @value{GDBN} reports
3792 Hardware watchpoint @var{num}: @var{expr}
3796 if it was able to set a hardware watchpoint.
3798 Currently, the @code{awatch} and @code{rwatch} commands can only set
3799 hardware watchpoints, because accesses to data that don't change the
3800 value of the watched expression cannot be detected without examining
3801 every instruction as it is being executed, and @value{GDBN} does not do
3802 that currently. If @value{GDBN} finds that it is unable to set a
3803 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3804 will print a message like this:
3807 Expression cannot be implemented with read/access watchpoint.
3810 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3811 data type of the watched expression is wider than what a hardware
3812 watchpoint on the target machine can handle. For example, some systems
3813 can only watch regions that are up to 4 bytes wide; on such systems you
3814 cannot set hardware watchpoints for an expression that yields a
3815 double-precision floating-point number (which is typically 8 bytes
3816 wide). As a work-around, it might be possible to break the large region
3817 into a series of smaller ones and watch them with separate watchpoints.
3819 If you set too many hardware watchpoints, @value{GDBN} might be unable
3820 to insert all of them when you resume the execution of your program.
3821 Since the precise number of active watchpoints is unknown until such
3822 time as the program is about to be resumed, @value{GDBN} might not be
3823 able to warn you about this when you set the watchpoints, and the
3824 warning will be printed only when the program is resumed:
3827 Hardware watchpoint @var{num}: Could not insert watchpoint
3831 If this happens, delete or disable some of the watchpoints.
3833 Watching complex expressions that reference many variables can also
3834 exhaust the resources available for hardware-assisted watchpoints.
3835 That's because @value{GDBN} needs to watch every variable in the
3836 expression with separately allocated resources.
3838 If you call a function interactively using @code{print} or @code{call},
3839 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3840 kind of breakpoint or the call completes.
3842 @value{GDBN} automatically deletes watchpoints that watch local
3843 (automatic) variables, or expressions that involve such variables, when
3844 they go out of scope, that is, when the execution leaves the block in
3845 which these variables were defined. In particular, when the program
3846 being debugged terminates, @emph{all} local variables go out of scope,
3847 and so only watchpoints that watch global variables remain set. If you
3848 rerun the program, you will need to set all such watchpoints again. One
3849 way of doing that would be to set a code breakpoint at the entry to the
3850 @code{main} function and when it breaks, set all the watchpoints.
3852 @cindex watchpoints and threads
3853 @cindex threads and watchpoints
3854 In multi-threaded programs, watchpoints will detect changes to the
3855 watched expression from every thread.
3858 @emph{Warning:} In multi-threaded programs, software watchpoints
3859 have only limited usefulness. If @value{GDBN} creates a software
3860 watchpoint, it can only watch the value of an expression @emph{in a
3861 single thread}. If you are confident that the expression can only
3862 change due to the current thread's activity (and if you are also
3863 confident that no other thread can become current), then you can use
3864 software watchpoints as usual. However, @value{GDBN} may not notice
3865 when a non-current thread's activity changes the expression. (Hardware
3866 watchpoints, in contrast, watch an expression in all threads.)
3869 @xref{set remote hardware-watchpoint-limit}.
3871 @node Set Catchpoints
3872 @subsection Setting Catchpoints
3873 @cindex catchpoints, setting
3874 @cindex exception handlers
3875 @cindex event handling
3877 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3878 kinds of program events, such as C@t{++} exceptions or the loading of a
3879 shared library. Use the @code{catch} command to set a catchpoint.
3883 @item catch @var{event}
3884 Stop when @var{event} occurs. @var{event} can be any of the following:
3887 @cindex stop on C@t{++} exceptions
3888 The throwing of a C@t{++} exception.
3891 The catching of a C@t{++} exception.
3894 @cindex Ada exception catching
3895 @cindex catch Ada exceptions
3896 An Ada exception being raised. If an exception name is specified
3897 at the end of the command (eg @code{catch exception Program_Error}),
3898 the debugger will stop only when this specific exception is raised.
3899 Otherwise, the debugger stops execution when any Ada exception is raised.
3901 When inserting an exception catchpoint on a user-defined exception whose
3902 name is identical to one of the exceptions defined by the language, the
3903 fully qualified name must be used as the exception name. Otherwise,
3904 @value{GDBN} will assume that it should stop on the pre-defined exception
3905 rather than the user-defined one. For instance, assuming an exception
3906 called @code{Constraint_Error} is defined in package @code{Pck}, then
3907 the command to use to catch such exceptions is @kbd{catch exception
3908 Pck.Constraint_Error}.
3910 @item exception unhandled
3911 An exception that was raised but is not handled by the program.
3914 A failed Ada assertion.
3917 @cindex break on fork/exec
3918 A call to @code{exec}. This is currently only available for HP-UX
3922 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3923 @cindex break on a system call.
3924 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3925 syscall is a mechanism for application programs to request a service
3926 from the operating system (OS) or one of the OS system services.
3927 @value{GDBN} can catch some or all of the syscalls issued by the
3928 debuggee, and show the related information for each syscall. If no
3929 argument is specified, calls to and returns from all system calls
3932 @var{name} can be any system call name that is valid for the
3933 underlying OS. Just what syscalls are valid depends on the OS. On
3934 GNU and Unix systems, you can find the full list of valid syscall
3935 names on @file{/usr/include/asm/unistd.h}.
3937 @c For MS-Windows, the syscall names and the corresponding numbers
3938 @c can be found, e.g., on this URL:
3939 @c http://www.metasploit.com/users/opcode/syscalls.html
3940 @c but we don't support Windows syscalls yet.
3942 Normally, @value{GDBN} knows in advance which syscalls are valid for
3943 each OS, so you can use the @value{GDBN} command-line completion
3944 facilities (@pxref{Completion,, command completion}) to list the
3947 You may also specify the system call numerically. A syscall's
3948 number is the value passed to the OS's syscall dispatcher to
3949 identify the requested service. When you specify the syscall by its
3950 name, @value{GDBN} uses its database of syscalls to convert the name
3951 into the corresponding numeric code, but using the number directly
3952 may be useful if @value{GDBN}'s database does not have the complete
3953 list of syscalls on your system (e.g., because @value{GDBN} lags
3954 behind the OS upgrades).
3956 The example below illustrates how this command works if you don't provide
3960 (@value{GDBP}) catch syscall
3961 Catchpoint 1 (syscall)
3963 Starting program: /tmp/catch-syscall
3965 Catchpoint 1 (call to syscall 'close'), \
3966 0xffffe424 in __kernel_vsyscall ()
3970 Catchpoint 1 (returned from syscall 'close'), \
3971 0xffffe424 in __kernel_vsyscall ()
3975 Here is an example of catching a system call by name:
3978 (@value{GDBP}) catch syscall chroot
3979 Catchpoint 1 (syscall 'chroot' [61])
3981 Starting program: /tmp/catch-syscall
3983 Catchpoint 1 (call to syscall 'chroot'), \
3984 0xffffe424 in __kernel_vsyscall ()
3988 Catchpoint 1 (returned from syscall 'chroot'), \
3989 0xffffe424 in __kernel_vsyscall ()
3993 An example of specifying a system call numerically. In the case
3994 below, the syscall number has a corresponding entry in the XML
3995 file, so @value{GDBN} finds its name and prints it:
3998 (@value{GDBP}) catch syscall 252
3999 Catchpoint 1 (syscall(s) 'exit_group')
4001 Starting program: /tmp/catch-syscall
4003 Catchpoint 1 (call to syscall 'exit_group'), \
4004 0xffffe424 in __kernel_vsyscall ()
4008 Program exited normally.
4012 However, there can be situations when there is no corresponding name
4013 in XML file for that syscall number. In this case, @value{GDBN} prints
4014 a warning message saying that it was not able to find the syscall name,
4015 but the catchpoint will be set anyway. See the example below:
4018 (@value{GDBP}) catch syscall 764
4019 warning: The number '764' does not represent a known syscall.
4020 Catchpoint 2 (syscall 764)
4024 If you configure @value{GDBN} using the @samp{--without-expat} option,
4025 it will not be able to display syscall names. Also, if your
4026 architecture does not have an XML file describing its system calls,
4027 you will not be able to see the syscall names. It is important to
4028 notice that these two features are used for accessing the syscall
4029 name database. In either case, you will see a warning like this:
4032 (@value{GDBP}) catch syscall
4033 warning: Could not open "syscalls/i386-linux.xml"
4034 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4035 GDB will not be able to display syscall names.
4036 Catchpoint 1 (syscall)
4040 Of course, the file name will change depending on your architecture and system.
4042 Still using the example above, you can also try to catch a syscall by its
4043 number. In this case, you would see something like:
4046 (@value{GDBP}) catch syscall 252
4047 Catchpoint 1 (syscall(s) 252)
4050 Again, in this case @value{GDBN} would not be able to display syscall's names.
4053 A call to @code{fork}. This is currently only available for HP-UX
4057 A call to @code{vfork}. This is currently only available for HP-UX
4062 @item tcatch @var{event}
4063 Set a catchpoint that is enabled only for one stop. The catchpoint is
4064 automatically deleted after the first time the event is caught.
4068 Use the @code{info break} command to list the current catchpoints.
4070 There are currently some limitations to C@t{++} exception handling
4071 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4075 If you call a function interactively, @value{GDBN} normally returns
4076 control to you when the function has finished executing. If the call
4077 raises an exception, however, the call may bypass the mechanism that
4078 returns control to you and cause your program either to abort or to
4079 simply continue running until it hits a breakpoint, catches a signal
4080 that @value{GDBN} is listening for, or exits. This is the case even if
4081 you set a catchpoint for the exception; catchpoints on exceptions are
4082 disabled within interactive calls.
4085 You cannot raise an exception interactively.
4088 You cannot install an exception handler interactively.
4091 @cindex raise exceptions
4092 Sometimes @code{catch} is not the best way to debug exception handling:
4093 if you need to know exactly where an exception is raised, it is better to
4094 stop @emph{before} the exception handler is called, since that way you
4095 can see the stack before any unwinding takes place. If you set a
4096 breakpoint in an exception handler instead, it may not be easy to find
4097 out where the exception was raised.
4099 To stop just before an exception handler is called, you need some
4100 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4101 raised by calling a library function named @code{__raise_exception}
4102 which has the following ANSI C interface:
4105 /* @var{addr} is where the exception identifier is stored.
4106 @var{id} is the exception identifier. */
4107 void __raise_exception (void **addr, void *id);
4111 To make the debugger catch all exceptions before any stack
4112 unwinding takes place, set a breakpoint on @code{__raise_exception}
4113 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4115 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4116 that depends on the value of @var{id}, you can stop your program when
4117 a specific exception is raised. You can use multiple conditional
4118 breakpoints to stop your program when any of a number of exceptions are
4123 @subsection Deleting Breakpoints
4125 @cindex clearing breakpoints, watchpoints, catchpoints
4126 @cindex deleting breakpoints, watchpoints, catchpoints
4127 It is often necessary to eliminate a breakpoint, watchpoint, or
4128 catchpoint once it has done its job and you no longer want your program
4129 to stop there. This is called @dfn{deleting} the breakpoint. A
4130 breakpoint that has been deleted no longer exists; it is forgotten.
4132 With the @code{clear} command you can delete breakpoints according to
4133 where they are in your program. With the @code{delete} command you can
4134 delete individual breakpoints, watchpoints, or catchpoints by specifying
4135 their breakpoint numbers.
4137 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4138 automatically ignores breakpoints on the first instruction to be executed
4139 when you continue execution without changing the execution address.
4144 Delete any breakpoints at the next instruction to be executed in the
4145 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4146 the innermost frame is selected, this is a good way to delete a
4147 breakpoint where your program just stopped.
4149 @item clear @var{location}
4150 Delete any breakpoints set at the specified @var{location}.
4151 @xref{Specify Location}, for the various forms of @var{location}; the
4152 most useful ones are listed below:
4155 @item clear @var{function}
4156 @itemx clear @var{filename}:@var{function}
4157 Delete any breakpoints set at entry to the named @var{function}.
4159 @item clear @var{linenum}
4160 @itemx clear @var{filename}:@var{linenum}
4161 Delete any breakpoints set at or within the code of the specified
4162 @var{linenum} of the specified @var{filename}.
4165 @cindex delete breakpoints
4167 @kindex d @r{(@code{delete})}
4168 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4169 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4170 ranges specified as arguments. If no argument is specified, delete all
4171 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4172 confirm off}). You can abbreviate this command as @code{d}.
4176 @subsection Disabling Breakpoints
4178 @cindex enable/disable a breakpoint
4179 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4180 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4181 it had been deleted, but remembers the information on the breakpoint so
4182 that you can @dfn{enable} it again later.
4184 You disable and enable breakpoints, watchpoints, and catchpoints with
4185 the @code{enable} and @code{disable} commands, optionally specifying
4186 one or more breakpoint numbers as arguments. Use @code{info break} to
4187 print a list of all breakpoints, watchpoints, and catchpoints if you
4188 do not know which numbers to use.
4190 Disabling and enabling a breakpoint that has multiple locations
4191 affects all of its locations.
4193 A breakpoint, watchpoint, or catchpoint can have any of four different
4194 states of enablement:
4198 Enabled. The breakpoint stops your program. A breakpoint set
4199 with the @code{break} command starts out in this state.
4201 Disabled. The breakpoint has no effect on your program.
4203 Enabled once. The breakpoint stops your program, but then becomes
4206 Enabled for deletion. The breakpoint stops your program, but
4207 immediately after it does so it is deleted permanently. A breakpoint
4208 set with the @code{tbreak} command starts out in this state.
4211 You can use the following commands to enable or disable breakpoints,
4212 watchpoints, and catchpoints:
4216 @kindex dis @r{(@code{disable})}
4217 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4218 Disable the specified breakpoints---or all breakpoints, if none are
4219 listed. A disabled breakpoint has no effect but is not forgotten. All
4220 options such as ignore-counts, conditions and commands are remembered in
4221 case the breakpoint is enabled again later. You may abbreviate
4222 @code{disable} as @code{dis}.
4225 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4226 Enable the specified breakpoints (or all defined breakpoints). They
4227 become effective once again in stopping your program.
4229 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4230 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4231 of these breakpoints immediately after stopping your program.
4233 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4234 Enable the specified breakpoints to work once, then die. @value{GDBN}
4235 deletes any of these breakpoints as soon as your program stops there.
4236 Breakpoints set by the @code{tbreak} command start out in this state.
4239 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4240 @c confusing: tbreak is also initially enabled.
4241 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4242 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4243 subsequently, they become disabled or enabled only when you use one of
4244 the commands above. (The command @code{until} can set and delete a
4245 breakpoint of its own, but it does not change the state of your other
4246 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4250 @subsection Break Conditions
4251 @cindex conditional breakpoints
4252 @cindex breakpoint conditions
4254 @c FIXME what is scope of break condition expr? Context where wanted?
4255 @c in particular for a watchpoint?
4256 The simplest sort of breakpoint breaks every time your program reaches a
4257 specified place. You can also specify a @dfn{condition} for a
4258 breakpoint. A condition is just a Boolean expression in your
4259 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4260 a condition evaluates the expression each time your program reaches it,
4261 and your program stops only if the condition is @emph{true}.
4263 This is the converse of using assertions for program validation; in that
4264 situation, you want to stop when the assertion is violated---that is,
4265 when the condition is false. In C, if you want to test an assertion expressed
4266 by the condition @var{assert}, you should set the condition
4267 @samp{! @var{assert}} on the appropriate breakpoint.
4269 Conditions are also accepted for watchpoints; you may not need them,
4270 since a watchpoint is inspecting the value of an expression anyhow---but
4271 it might be simpler, say, to just set a watchpoint on a variable name,
4272 and specify a condition that tests whether the new value is an interesting
4275 Break conditions can have side effects, and may even call functions in
4276 your program. This can be useful, for example, to activate functions
4277 that log program progress, or to use your own print functions to
4278 format special data structures. The effects are completely predictable
4279 unless there is another enabled breakpoint at the same address. (In
4280 that case, @value{GDBN} might see the other breakpoint first and stop your
4281 program without checking the condition of this one.) Note that
4282 breakpoint commands are usually more convenient and flexible than break
4284 purpose of performing side effects when a breakpoint is reached
4285 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4287 Break conditions can be specified when a breakpoint is set, by using
4288 @samp{if} in the arguments to the @code{break} command. @xref{Set
4289 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4290 with the @code{condition} command.
4292 You can also use the @code{if} keyword with the @code{watch} command.
4293 The @code{catch} command does not recognize the @code{if} keyword;
4294 @code{condition} is the only way to impose a further condition on a
4299 @item condition @var{bnum} @var{expression}
4300 Specify @var{expression} as the break condition for breakpoint,
4301 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4302 breakpoint @var{bnum} stops your program only if the value of
4303 @var{expression} is true (nonzero, in C). When you use
4304 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4305 syntactic correctness, and to determine whether symbols in it have
4306 referents in the context of your breakpoint. If @var{expression} uses
4307 symbols not referenced in the context of the breakpoint, @value{GDBN}
4308 prints an error message:
4311 No symbol "foo" in current context.
4316 not actually evaluate @var{expression} at the time the @code{condition}
4317 command (or a command that sets a breakpoint with a condition, like
4318 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4320 @item condition @var{bnum}
4321 Remove the condition from breakpoint number @var{bnum}. It becomes
4322 an ordinary unconditional breakpoint.
4325 @cindex ignore count (of breakpoint)
4326 A special case of a breakpoint condition is to stop only when the
4327 breakpoint has been reached a certain number of times. This is so
4328 useful that there is a special way to do it, using the @dfn{ignore
4329 count} of the breakpoint. Every breakpoint has an ignore count, which
4330 is an integer. Most of the time, the ignore count is zero, and
4331 therefore has no effect. But if your program reaches a breakpoint whose
4332 ignore count is positive, then instead of stopping, it just decrements
4333 the ignore count by one and continues. As a result, if the ignore count
4334 value is @var{n}, the breakpoint does not stop the next @var{n} times
4335 your program reaches it.
4339 @item ignore @var{bnum} @var{count}
4340 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4341 The next @var{count} times the breakpoint is reached, your program's
4342 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4345 To make the breakpoint stop the next time it is reached, specify
4348 When you use @code{continue} to resume execution of your program from a
4349 breakpoint, you can specify an ignore count directly as an argument to
4350 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4351 Stepping,,Continuing and Stepping}.
4353 If a breakpoint has a positive ignore count and a condition, the
4354 condition is not checked. Once the ignore count reaches zero,
4355 @value{GDBN} resumes checking the condition.
4357 You could achieve the effect of the ignore count with a condition such
4358 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4359 is decremented each time. @xref{Convenience Vars, ,Convenience
4363 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4366 @node Break Commands
4367 @subsection Breakpoint Command Lists
4369 @cindex breakpoint commands
4370 You can give any breakpoint (or watchpoint or catchpoint) a series of
4371 commands to execute when your program stops due to that breakpoint. For
4372 example, you might want to print the values of certain expressions, or
4373 enable other breakpoints.
4377 @kindex end@r{ (breakpoint commands)}
4378 @item commands @r{[}@var{range}@dots{}@r{]}
4379 @itemx @dots{} @var{command-list} @dots{}
4381 Specify a list of commands for the given breakpoints. The commands
4382 themselves appear on the following lines. Type a line containing just
4383 @code{end} to terminate the commands.
4385 To remove all commands from a breakpoint, type @code{commands} and
4386 follow it immediately with @code{end}; that is, give no commands.
4388 With no argument, @code{commands} refers to the last breakpoint,
4389 watchpoint, or catchpoint set (not to the breakpoint most recently
4390 encountered). If the most recent breakpoints were set with a single
4391 command, then the @code{commands} will apply to all the breakpoints
4392 set by that command. This applies to breakpoints set by
4393 @code{rbreak}, and also applies when a single @code{break} command
4394 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4398 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4399 disabled within a @var{command-list}.
4401 You can use breakpoint commands to start your program up again. Simply
4402 use the @code{continue} command, or @code{step}, or any other command
4403 that resumes execution.
4405 Any other commands in the command list, after a command that resumes
4406 execution, are ignored. This is because any time you resume execution
4407 (even with a simple @code{next} or @code{step}), you may encounter
4408 another breakpoint---which could have its own command list, leading to
4409 ambiguities about which list to execute.
4412 If the first command you specify in a command list is @code{silent}, the
4413 usual message about stopping at a breakpoint is not printed. This may
4414 be desirable for breakpoints that are to print a specific message and
4415 then continue. If none of the remaining commands print anything, you
4416 see no sign that the breakpoint was reached. @code{silent} is
4417 meaningful only at the beginning of a breakpoint command list.
4419 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4420 print precisely controlled output, and are often useful in silent
4421 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4423 For example, here is how you could use breakpoint commands to print the
4424 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4430 printf "x is %d\n",x
4435 One application for breakpoint commands is to compensate for one bug so
4436 you can test for another. Put a breakpoint just after the erroneous line
4437 of code, give it a condition to detect the case in which something
4438 erroneous has been done, and give it commands to assign correct values
4439 to any variables that need them. End with the @code{continue} command
4440 so that your program does not stop, and start with the @code{silent}
4441 command so that no output is produced. Here is an example:
4452 @node Save Breakpoints
4453 @subsection How to save breakpoints to a file
4455 To save breakpoint definitions to a file use the @w{@code{save
4456 breakpoints}} command.
4459 @kindex save breakpoints
4460 @cindex save breakpoints to a file for future sessions
4461 @item save breakpoints [@var{filename}]
4462 This command saves all current breakpoint definitions together with
4463 their commands and ignore counts, into a file @file{@var{filename}}
4464 suitable for use in a later debugging session. This includes all
4465 types of breakpoints (breakpoints, watchpoints, catchpoints,
4466 tracepoints). To read the saved breakpoint definitions, use the
4467 @code{source} command (@pxref{Command Files}). Note that watchpoints
4468 with expressions involving local variables may fail to be recreated
4469 because it may not be possible to access the context where the
4470 watchpoint is valid anymore. Because the saved breakpoint definitions
4471 are simply a sequence of @value{GDBN} commands that recreate the
4472 breakpoints, you can edit the file in your favorite editing program,
4473 and remove the breakpoint definitions you're not interested in, or
4474 that can no longer be recreated.
4477 @c @ifclear BARETARGET
4478 @node Error in Breakpoints
4479 @subsection ``Cannot insert breakpoints''
4481 If you request too many active hardware-assisted breakpoints and
4482 watchpoints, you will see this error message:
4484 @c FIXME: the precise wording of this message may change; the relevant
4485 @c source change is not committed yet (Sep 3, 1999).
4487 Stopped; cannot insert breakpoints.
4488 You may have requested too many hardware breakpoints and watchpoints.
4492 This message is printed when you attempt to resume the program, since
4493 only then @value{GDBN} knows exactly how many hardware breakpoints and
4494 watchpoints it needs to insert.
4496 When this message is printed, you need to disable or remove some of the
4497 hardware-assisted breakpoints and watchpoints, and then continue.
4499 @node Breakpoint-related Warnings
4500 @subsection ``Breakpoint address adjusted...''
4501 @cindex breakpoint address adjusted
4503 Some processor architectures place constraints on the addresses at
4504 which breakpoints may be placed. For architectures thus constrained,
4505 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4506 with the constraints dictated by the architecture.
4508 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4509 a VLIW architecture in which a number of RISC-like instructions may be
4510 bundled together for parallel execution. The FR-V architecture
4511 constrains the location of a breakpoint instruction within such a
4512 bundle to the instruction with the lowest address. @value{GDBN}
4513 honors this constraint by adjusting a breakpoint's address to the
4514 first in the bundle.
4516 It is not uncommon for optimized code to have bundles which contain
4517 instructions from different source statements, thus it may happen that
4518 a breakpoint's address will be adjusted from one source statement to
4519 another. Since this adjustment may significantly alter @value{GDBN}'s
4520 breakpoint related behavior from what the user expects, a warning is
4521 printed when the breakpoint is first set and also when the breakpoint
4524 A warning like the one below is printed when setting a breakpoint
4525 that's been subject to address adjustment:
4528 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4531 Such warnings are printed both for user settable and @value{GDBN}'s
4532 internal breakpoints. If you see one of these warnings, you should
4533 verify that a breakpoint set at the adjusted address will have the
4534 desired affect. If not, the breakpoint in question may be removed and
4535 other breakpoints may be set which will have the desired behavior.
4536 E.g., it may be sufficient to place the breakpoint at a later
4537 instruction. A conditional breakpoint may also be useful in some
4538 cases to prevent the breakpoint from triggering too often.
4540 @value{GDBN} will also issue a warning when stopping at one of these
4541 adjusted breakpoints:
4544 warning: Breakpoint 1 address previously adjusted from 0x00010414
4548 When this warning is encountered, it may be too late to take remedial
4549 action except in cases where the breakpoint is hit earlier or more
4550 frequently than expected.
4552 @node Continuing and Stepping
4553 @section Continuing and Stepping
4557 @cindex resuming execution
4558 @dfn{Continuing} means resuming program execution until your program
4559 completes normally. In contrast, @dfn{stepping} means executing just
4560 one more ``step'' of your program, where ``step'' may mean either one
4561 line of source code, or one machine instruction (depending on what
4562 particular command you use). Either when continuing or when stepping,
4563 your program may stop even sooner, due to a breakpoint or a signal. (If
4564 it stops due to a signal, you may want to use @code{handle}, or use
4565 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4569 @kindex c @r{(@code{continue})}
4570 @kindex fg @r{(resume foreground execution)}
4571 @item continue @r{[}@var{ignore-count}@r{]}
4572 @itemx c @r{[}@var{ignore-count}@r{]}
4573 @itemx fg @r{[}@var{ignore-count}@r{]}
4574 Resume program execution, at the address where your program last stopped;
4575 any breakpoints set at that address are bypassed. The optional argument
4576 @var{ignore-count} allows you to specify a further number of times to
4577 ignore a breakpoint at this location; its effect is like that of
4578 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4580 The argument @var{ignore-count} is meaningful only when your program
4581 stopped due to a breakpoint. At other times, the argument to
4582 @code{continue} is ignored.
4584 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4585 debugged program is deemed to be the foreground program) are provided
4586 purely for convenience, and have exactly the same behavior as
4590 To resume execution at a different place, you can use @code{return}
4591 (@pxref{Returning, ,Returning from a Function}) to go back to the
4592 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4593 Different Address}) to go to an arbitrary location in your program.
4595 A typical technique for using stepping is to set a breakpoint
4596 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4597 beginning of the function or the section of your program where a problem
4598 is believed to lie, run your program until it stops at that breakpoint,
4599 and then step through the suspect area, examining the variables that are
4600 interesting, until you see the problem happen.
4604 @kindex s @r{(@code{step})}
4606 Continue running your program until control reaches a different source
4607 line, then stop it and return control to @value{GDBN}. This command is
4608 abbreviated @code{s}.
4611 @c "without debugging information" is imprecise; actually "without line
4612 @c numbers in the debugging information". (gcc -g1 has debugging info but
4613 @c not line numbers). But it seems complex to try to make that
4614 @c distinction here.
4615 @emph{Warning:} If you use the @code{step} command while control is
4616 within a function that was compiled without debugging information,
4617 execution proceeds until control reaches a function that does have
4618 debugging information. Likewise, it will not step into a function which
4619 is compiled without debugging information. To step through functions
4620 without debugging information, use the @code{stepi} command, described
4624 The @code{step} command only stops at the first instruction of a source
4625 line. This prevents the multiple stops that could otherwise occur in
4626 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4627 to stop if a function that has debugging information is called within
4628 the line. In other words, @code{step} @emph{steps inside} any functions
4629 called within the line.
4631 Also, the @code{step} command only enters a function if there is line
4632 number information for the function. Otherwise it acts like the
4633 @code{next} command. This avoids problems when using @code{cc -gl}
4634 on MIPS machines. Previously, @code{step} entered subroutines if there
4635 was any debugging information about the routine.
4637 @item step @var{count}
4638 Continue running as in @code{step}, but do so @var{count} times. If a
4639 breakpoint is reached, or a signal not related to stepping occurs before
4640 @var{count} steps, stepping stops right away.
4643 @kindex n @r{(@code{next})}
4644 @item next @r{[}@var{count}@r{]}
4645 Continue to the next source line in the current (innermost) stack frame.
4646 This is similar to @code{step}, but function calls that appear within
4647 the line of code are executed without stopping. Execution stops when
4648 control reaches a different line of code at the original stack level
4649 that was executing when you gave the @code{next} command. This command
4650 is abbreviated @code{n}.
4652 An argument @var{count} is a repeat count, as for @code{step}.
4655 @c FIX ME!! Do we delete this, or is there a way it fits in with
4656 @c the following paragraph? --- Vctoria
4658 @c @code{next} within a function that lacks debugging information acts like
4659 @c @code{step}, but any function calls appearing within the code of the
4660 @c function are executed without stopping.
4662 The @code{next} command only stops at the first instruction of a
4663 source line. This prevents multiple stops that could otherwise occur in
4664 @code{switch} statements, @code{for} loops, etc.
4666 @kindex set step-mode
4668 @cindex functions without line info, and stepping
4669 @cindex stepping into functions with no line info
4670 @itemx set step-mode on
4671 The @code{set step-mode on} command causes the @code{step} command to
4672 stop at the first instruction of a function which contains no debug line
4673 information rather than stepping over it.
4675 This is useful in cases where you may be interested in inspecting the
4676 machine instructions of a function which has no symbolic info and do not
4677 want @value{GDBN} to automatically skip over this function.
4679 @item set step-mode off
4680 Causes the @code{step} command to step over any functions which contains no
4681 debug information. This is the default.
4683 @item show step-mode
4684 Show whether @value{GDBN} will stop in or step over functions without
4685 source line debug information.
4688 @kindex fin @r{(@code{finish})}
4690 Continue running until just after function in the selected stack frame
4691 returns. Print the returned value (if any). This command can be
4692 abbreviated as @code{fin}.
4694 Contrast this with the @code{return} command (@pxref{Returning,
4695 ,Returning from a Function}).
4698 @kindex u @r{(@code{until})}
4699 @cindex run until specified location
4702 Continue running until a source line past the current line, in the
4703 current stack frame, is reached. This command is used to avoid single
4704 stepping through a loop more than once. It is like the @code{next}
4705 command, except that when @code{until} encounters a jump, it
4706 automatically continues execution until the program counter is greater
4707 than the address of the jump.
4709 This means that when you reach the end of a loop after single stepping
4710 though it, @code{until} makes your program continue execution until it
4711 exits the loop. In contrast, a @code{next} command at the end of a loop
4712 simply steps back to the beginning of the loop, which forces you to step
4713 through the next iteration.
4715 @code{until} always stops your program if it attempts to exit the current
4718 @code{until} may produce somewhat counterintuitive results if the order
4719 of machine code does not match the order of the source lines. For
4720 example, in the following excerpt from a debugging session, the @code{f}
4721 (@code{frame}) command shows that execution is stopped at line
4722 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4726 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4728 (@value{GDBP}) until
4729 195 for ( ; argc > 0; NEXTARG) @{
4732 This happened because, for execution efficiency, the compiler had
4733 generated code for the loop closure test at the end, rather than the
4734 start, of the loop---even though the test in a C @code{for}-loop is
4735 written before the body of the loop. The @code{until} command appeared
4736 to step back to the beginning of the loop when it advanced to this
4737 expression; however, it has not really gone to an earlier
4738 statement---not in terms of the actual machine code.
4740 @code{until} with no argument works by means of single
4741 instruction stepping, and hence is slower than @code{until} with an
4744 @item until @var{location}
4745 @itemx u @var{location}
4746 Continue running your program until either the specified location is
4747 reached, or the current stack frame returns. @var{location} is any of
4748 the forms described in @ref{Specify Location}.
4749 This form of the command uses temporary breakpoints, and
4750 hence is quicker than @code{until} without an argument. The specified
4751 location is actually reached only if it is in the current frame. This
4752 implies that @code{until} can be used to skip over recursive function
4753 invocations. For instance in the code below, if the current location is
4754 line @code{96}, issuing @code{until 99} will execute the program up to
4755 line @code{99} in the same invocation of factorial, i.e., after the inner
4756 invocations have returned.
4759 94 int factorial (int value)
4761 96 if (value > 1) @{
4762 97 value *= factorial (value - 1);
4769 @kindex advance @var{location}
4770 @itemx advance @var{location}
4771 Continue running the program up to the given @var{location}. An argument is
4772 required, which should be of one of the forms described in
4773 @ref{Specify Location}.
4774 Execution will also stop upon exit from the current stack
4775 frame. This command is similar to @code{until}, but @code{advance} will
4776 not skip over recursive function calls, and the target location doesn't
4777 have to be in the same frame as the current one.
4781 @kindex si @r{(@code{stepi})}
4783 @itemx stepi @var{arg}
4785 Execute one machine instruction, then stop and return to the debugger.
4787 It is often useful to do @samp{display/i $pc} when stepping by machine
4788 instructions. This makes @value{GDBN} automatically display the next
4789 instruction to be executed, each time your program stops. @xref{Auto
4790 Display,, Automatic Display}.
4792 An argument is a repeat count, as in @code{step}.
4796 @kindex ni @r{(@code{nexti})}
4798 @itemx nexti @var{arg}
4800 Execute one machine instruction, but if it is a function call,
4801 proceed until the function returns.
4803 An argument is a repeat count, as in @code{next}.
4810 A signal is an asynchronous event that can happen in a program. The
4811 operating system defines the possible kinds of signals, and gives each
4812 kind a name and a number. For example, in Unix @code{SIGINT} is the
4813 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4814 @code{SIGSEGV} is the signal a program gets from referencing a place in
4815 memory far away from all the areas in use; @code{SIGALRM} occurs when
4816 the alarm clock timer goes off (which happens only if your program has
4817 requested an alarm).
4819 @cindex fatal signals
4820 Some signals, including @code{SIGALRM}, are a normal part of the
4821 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4822 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4823 program has not specified in advance some other way to handle the signal.
4824 @code{SIGINT} does not indicate an error in your program, but it is normally
4825 fatal so it can carry out the purpose of the interrupt: to kill the program.
4827 @value{GDBN} has the ability to detect any occurrence of a signal in your
4828 program. You can tell @value{GDBN} in advance what to do for each kind of
4831 @cindex handling signals
4832 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4833 @code{SIGALRM} be silently passed to your program
4834 (so as not to interfere with their role in the program's functioning)
4835 but to stop your program immediately whenever an error signal happens.
4836 You can change these settings with the @code{handle} command.
4839 @kindex info signals
4843 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4844 handle each one. You can use this to see the signal numbers of all
4845 the defined types of signals.
4847 @item info signals @var{sig}
4848 Similar, but print information only about the specified signal number.
4850 @code{info handle} is an alias for @code{info signals}.
4853 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4854 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4855 can be the number of a signal or its name (with or without the
4856 @samp{SIG} at the beginning); a list of signal numbers of the form
4857 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4858 known signals. Optional arguments @var{keywords}, described below,
4859 say what change to make.
4863 The keywords allowed by the @code{handle} command can be abbreviated.
4864 Their full names are:
4868 @value{GDBN} should not stop your program when this signal happens. It may
4869 still print a message telling you that the signal has come in.
4872 @value{GDBN} should stop your program when this signal happens. This implies
4873 the @code{print} keyword as well.
4876 @value{GDBN} should print a message when this signal happens.
4879 @value{GDBN} should not mention the occurrence of the signal at all. This
4880 implies the @code{nostop} keyword as well.
4884 @value{GDBN} should allow your program to see this signal; your program
4885 can handle the signal, or else it may terminate if the signal is fatal
4886 and not handled. @code{pass} and @code{noignore} are synonyms.
4890 @value{GDBN} should not allow your program to see this signal.
4891 @code{nopass} and @code{ignore} are synonyms.
4895 When a signal stops your program, the signal is not visible to the
4897 continue. Your program sees the signal then, if @code{pass} is in
4898 effect for the signal in question @emph{at that time}. In other words,
4899 after @value{GDBN} reports a signal, you can use the @code{handle}
4900 command with @code{pass} or @code{nopass} to control whether your
4901 program sees that signal when you continue.
4903 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4904 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4905 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4908 You can also use the @code{signal} command to prevent your program from
4909 seeing a signal, or cause it to see a signal it normally would not see,
4910 or to give it any signal at any time. For example, if your program stopped
4911 due to some sort of memory reference error, you might store correct
4912 values into the erroneous variables and continue, hoping to see more
4913 execution; but your program would probably terminate immediately as
4914 a result of the fatal signal once it saw the signal. To prevent this,
4915 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4918 @cindex extra signal information
4919 @anchor{extra signal information}
4921 On some targets, @value{GDBN} can inspect extra signal information
4922 associated with the intercepted signal, before it is actually
4923 delivered to the program being debugged. This information is exported
4924 by the convenience variable @code{$_siginfo}, and consists of data
4925 that is passed by the kernel to the signal handler at the time of the
4926 receipt of a signal. The data type of the information itself is
4927 target dependent. You can see the data type using the @code{ptype
4928 $_siginfo} command. On Unix systems, it typically corresponds to the
4929 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4932 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4933 referenced address that raised a segmentation fault.
4937 (@value{GDBP}) continue
4938 Program received signal SIGSEGV, Segmentation fault.
4939 0x0000000000400766 in main ()
4941 (@value{GDBP}) ptype $_siginfo
4948 struct @{...@} _kill;
4949 struct @{...@} _timer;
4951 struct @{...@} _sigchld;
4952 struct @{...@} _sigfault;
4953 struct @{...@} _sigpoll;
4956 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4960 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4961 $1 = (void *) 0x7ffff7ff7000
4965 Depending on target support, @code{$_siginfo} may also be writable.
4968 @section Stopping and Starting Multi-thread Programs
4970 @cindex stopped threads
4971 @cindex threads, stopped
4973 @cindex continuing threads
4974 @cindex threads, continuing
4976 @value{GDBN} supports debugging programs with multiple threads
4977 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4978 are two modes of controlling execution of your program within the
4979 debugger. In the default mode, referred to as @dfn{all-stop mode},
4980 when any thread in your program stops (for example, at a breakpoint
4981 or while being stepped), all other threads in the program are also stopped by
4982 @value{GDBN}. On some targets, @value{GDBN} also supports
4983 @dfn{non-stop mode}, in which other threads can continue to run freely while
4984 you examine the stopped thread in the debugger.
4987 * All-Stop Mode:: All threads stop when GDB takes control
4988 * Non-Stop Mode:: Other threads continue to execute
4989 * Background Execution:: Running your program asynchronously
4990 * Thread-Specific Breakpoints:: Controlling breakpoints
4991 * Interrupted System Calls:: GDB may interfere with system calls
4992 * Observer Mode:: GDB does not alter program behavior
4996 @subsection All-Stop Mode
4998 @cindex all-stop mode
5000 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5001 @emph{all} threads of execution stop, not just the current thread. This
5002 allows you to examine the overall state of the program, including
5003 switching between threads, without worrying that things may change
5006 Conversely, whenever you restart the program, @emph{all} threads start
5007 executing. @emph{This is true even when single-stepping} with commands
5008 like @code{step} or @code{next}.
5010 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5011 Since thread scheduling is up to your debugging target's operating
5012 system (not controlled by @value{GDBN}), other threads may
5013 execute more than one statement while the current thread completes a
5014 single step. Moreover, in general other threads stop in the middle of a
5015 statement, rather than at a clean statement boundary, when the program
5018 You might even find your program stopped in another thread after
5019 continuing or even single-stepping. This happens whenever some other
5020 thread runs into a breakpoint, a signal, or an exception before the
5021 first thread completes whatever you requested.
5023 @cindex automatic thread selection
5024 @cindex switching threads automatically
5025 @cindex threads, automatic switching
5026 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5027 signal, it automatically selects the thread where that breakpoint or
5028 signal happened. @value{GDBN} alerts you to the context switch with a
5029 message such as @samp{[Switching to Thread @var{n}]} to identify the
5032 On some OSes, you can modify @value{GDBN}'s default behavior by
5033 locking the OS scheduler to allow only a single thread to run.
5036 @item set scheduler-locking @var{mode}
5037 @cindex scheduler locking mode
5038 @cindex lock scheduler
5039 Set the scheduler locking mode. If it is @code{off}, then there is no
5040 locking and any thread may run at any time. If @code{on}, then only the
5041 current thread may run when the inferior is resumed. The @code{step}
5042 mode optimizes for single-stepping; it prevents other threads
5043 from preempting the current thread while you are stepping, so that
5044 the focus of debugging does not change unexpectedly.
5045 Other threads only rarely (or never) get a chance to run
5046 when you step. They are more likely to run when you @samp{next} over a
5047 function call, and they are completely free to run when you use commands
5048 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5049 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5050 the current thread away from the thread that you are debugging.
5052 @item show scheduler-locking
5053 Display the current scheduler locking mode.
5056 @cindex resume threads of multiple processes simultaneously
5057 By default, when you issue one of the execution commands such as
5058 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5059 threads of the current inferior to run. For example, if @value{GDBN}
5060 is attached to two inferiors, each with two threads, the
5061 @code{continue} command resumes only the two threads of the current
5062 inferior. This is useful, for example, when you debug a program that
5063 forks and you want to hold the parent stopped (so that, for instance,
5064 it doesn't run to exit), while you debug the child. In other
5065 situations, you may not be interested in inspecting the current state
5066 of any of the processes @value{GDBN} is attached to, and you may want
5067 to resume them all until some breakpoint is hit. In the latter case,
5068 you can instruct @value{GDBN} to allow all threads of all the
5069 inferiors to run with the @w{@code{set schedule-multiple}} command.
5072 @kindex set schedule-multiple
5073 @item set schedule-multiple
5074 Set the mode for allowing threads of multiple processes to be resumed
5075 when an execution command is issued. When @code{on}, all threads of
5076 all processes are allowed to run. When @code{off}, only the threads
5077 of the current process are resumed. The default is @code{off}. The
5078 @code{scheduler-locking} mode takes precedence when set to @code{on},
5079 or while you are stepping and set to @code{step}.
5081 @item show schedule-multiple
5082 Display the current mode for resuming the execution of threads of
5087 @subsection Non-Stop Mode
5089 @cindex non-stop mode
5091 @c This section is really only a place-holder, and needs to be expanded
5092 @c with more details.
5094 For some multi-threaded targets, @value{GDBN} supports an optional
5095 mode of operation in which you can examine stopped program threads in
5096 the debugger while other threads continue to execute freely. This
5097 minimizes intrusion when debugging live systems, such as programs
5098 where some threads have real-time constraints or must continue to
5099 respond to external events. This is referred to as @dfn{non-stop} mode.
5101 In non-stop mode, when a thread stops to report a debugging event,
5102 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5103 threads as well, in contrast to the all-stop mode behavior. Additionally,
5104 execution commands such as @code{continue} and @code{step} apply by default
5105 only to the current thread in non-stop mode, rather than all threads as
5106 in all-stop mode. This allows you to control threads explicitly in
5107 ways that are not possible in all-stop mode --- for example, stepping
5108 one thread while allowing others to run freely, stepping
5109 one thread while holding all others stopped, or stepping several threads
5110 independently and simultaneously.
5112 To enter non-stop mode, use this sequence of commands before you run
5113 or attach to your program:
5116 # Enable the async interface.
5119 # If using the CLI, pagination breaks non-stop.
5122 # Finally, turn it on!
5126 You can use these commands to manipulate the non-stop mode setting:
5129 @kindex set non-stop
5130 @item set non-stop on
5131 Enable selection of non-stop mode.
5132 @item set non-stop off
5133 Disable selection of non-stop mode.
5134 @kindex show non-stop
5136 Show the current non-stop enablement setting.
5139 Note these commands only reflect whether non-stop mode is enabled,
5140 not whether the currently-executing program is being run in non-stop mode.
5141 In particular, the @code{set non-stop} preference is only consulted when
5142 @value{GDBN} starts or connects to the target program, and it is generally
5143 not possible to switch modes once debugging has started. Furthermore,
5144 since not all targets support non-stop mode, even when you have enabled
5145 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5148 In non-stop mode, all execution commands apply only to the current thread
5149 by default. That is, @code{continue} only continues one thread.
5150 To continue all threads, issue @code{continue -a} or @code{c -a}.
5152 You can use @value{GDBN}'s background execution commands
5153 (@pxref{Background Execution}) to run some threads in the background
5154 while you continue to examine or step others from @value{GDBN}.
5155 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5156 always executed asynchronously in non-stop mode.
5158 Suspending execution is done with the @code{interrupt} command when
5159 running in the background, or @kbd{Ctrl-c} during foreground execution.
5160 In all-stop mode, this stops the whole process;
5161 but in non-stop mode the interrupt applies only to the current thread.
5162 To stop the whole program, use @code{interrupt -a}.
5164 Other execution commands do not currently support the @code{-a} option.
5166 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5167 that thread current, as it does in all-stop mode. This is because the
5168 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5169 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5170 changed to a different thread just as you entered a command to operate on the
5171 previously current thread.
5173 @node Background Execution
5174 @subsection Background Execution
5176 @cindex foreground execution
5177 @cindex background execution
5178 @cindex asynchronous execution
5179 @cindex execution, foreground, background and asynchronous
5181 @value{GDBN}'s execution commands have two variants: the normal
5182 foreground (synchronous) behavior, and a background
5183 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5184 the program to report that some thread has stopped before prompting for
5185 another command. In background execution, @value{GDBN} immediately gives
5186 a command prompt so that you can issue other commands while your program runs.
5188 You need to explicitly enable asynchronous mode before you can use
5189 background execution commands. You can use these commands to
5190 manipulate the asynchronous mode setting:
5193 @kindex set target-async
5194 @item set target-async on
5195 Enable asynchronous mode.
5196 @item set target-async off
5197 Disable asynchronous mode.
5198 @kindex show target-async
5199 @item show target-async
5200 Show the current target-async setting.
5203 If the target doesn't support async mode, @value{GDBN} issues an error
5204 message if you attempt to use the background execution commands.
5206 To specify background execution, add a @code{&} to the command. For example,
5207 the background form of the @code{continue} command is @code{continue&}, or
5208 just @code{c&}. The execution commands that accept background execution
5214 @xref{Starting, , Starting your Program}.
5218 @xref{Attach, , Debugging an Already-running Process}.
5222 @xref{Continuing and Stepping, step}.
5226 @xref{Continuing and Stepping, stepi}.
5230 @xref{Continuing and Stepping, next}.
5234 @xref{Continuing and Stepping, nexti}.
5238 @xref{Continuing and Stepping, continue}.
5242 @xref{Continuing and Stepping, finish}.
5246 @xref{Continuing and Stepping, until}.
5250 Background execution is especially useful in conjunction with non-stop
5251 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5252 However, you can also use these commands in the normal all-stop mode with
5253 the restriction that you cannot issue another execution command until the
5254 previous one finishes. Examples of commands that are valid in all-stop
5255 mode while the program is running include @code{help} and @code{info break}.
5257 You can interrupt your program while it is running in the background by
5258 using the @code{interrupt} command.
5265 Suspend execution of the running program. In all-stop mode,
5266 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5267 only the current thread. To stop the whole program in non-stop mode,
5268 use @code{interrupt -a}.
5271 @node Thread-Specific Breakpoints
5272 @subsection Thread-Specific Breakpoints
5274 When your program has multiple threads (@pxref{Threads,, Debugging
5275 Programs with Multiple Threads}), you can choose whether to set
5276 breakpoints on all threads, or on a particular thread.
5279 @cindex breakpoints and threads
5280 @cindex thread breakpoints
5281 @kindex break @dots{} thread @var{threadno}
5282 @item break @var{linespec} thread @var{threadno}
5283 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5284 @var{linespec} specifies source lines; there are several ways of
5285 writing them (@pxref{Specify Location}), but the effect is always to
5286 specify some source line.
5288 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5289 to specify that you only want @value{GDBN} to stop the program when a
5290 particular thread reaches this breakpoint. @var{threadno} is one of the
5291 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5292 column of the @samp{info threads} display.
5294 If you do not specify @samp{thread @var{threadno}} when you set a
5295 breakpoint, the breakpoint applies to @emph{all} threads of your
5298 You can use the @code{thread} qualifier on conditional breakpoints as
5299 well; in this case, place @samp{thread @var{threadno}} before or
5300 after the breakpoint condition, like this:
5303 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5308 @node Interrupted System Calls
5309 @subsection Interrupted System Calls
5311 @cindex thread breakpoints and system calls
5312 @cindex system calls and thread breakpoints
5313 @cindex premature return from system calls
5314 There is an unfortunate side effect when using @value{GDBN} to debug
5315 multi-threaded programs. If one thread stops for a
5316 breakpoint, or for some other reason, and another thread is blocked in a
5317 system call, then the system call may return prematurely. This is a
5318 consequence of the interaction between multiple threads and the signals
5319 that @value{GDBN} uses to implement breakpoints and other events that
5322 To handle this problem, your program should check the return value of
5323 each system call and react appropriately. This is good programming
5326 For example, do not write code like this:
5332 The call to @code{sleep} will return early if a different thread stops
5333 at a breakpoint or for some other reason.
5335 Instead, write this:
5340 unslept = sleep (unslept);
5343 A system call is allowed to return early, so the system is still
5344 conforming to its specification. But @value{GDBN} does cause your
5345 multi-threaded program to behave differently than it would without
5348 Also, @value{GDBN} uses internal breakpoints in the thread library to
5349 monitor certain events such as thread creation and thread destruction.
5350 When such an event happens, a system call in another thread may return
5351 prematurely, even though your program does not appear to stop.
5354 @subsection Observer Mode
5356 If you want to build on non-stop mode and observe program behavior
5357 without any chance of disruption by @value{GDBN}, you can set
5358 variables to disable all of the debugger's attempts to modify state,
5359 whether by writing memory, inserting breakpoints, etc. These operate
5360 at a low level, intercepting operations from all commands.
5362 When all of these are set to @code{off}, then @value{GDBN} is said to
5363 be @dfn{observer mode}. As a convenience, the variable
5364 @code{observer} can be set to disable these, plus enable non-stop
5367 Note that @value{GDBN} will not prevent you from making nonsensical
5368 combinations of these settings. For instance, if you have enabled
5369 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5370 then breakpoints that work by writing trap instructions into the code
5371 stream will still not be able to be placed.
5376 @item set observer on
5377 @itemx set observer off
5378 When set to @code{on}, this disables all the permission variables
5379 below (except for @code{insert-fast-tracepoints}), plus enables
5380 non-stop debugging. Setting this to @code{off} switches back to
5381 normal debugging, though remaining in non-stop mode.
5384 Show whether observer mode is on or off.
5386 @kindex may-write-registers
5387 @item set may-write-registers on
5388 @itemx set may-write-registers off
5389 This controls whether @value{GDBN} will attempt to alter the values of
5390 registers, such as with assignment expressions in @code{print}, or the
5391 @code{jump} command. It defaults to @code{on}.
5393 @item show may-write-registers
5394 Show the current permission to write registers.
5396 @kindex may-write-memory
5397 @item set may-write-memory on
5398 @itemx set may-write-memory off
5399 This controls whether @value{GDBN} will attempt to alter the contents
5400 of memory, such as with assignment expressions in @code{print}. It
5401 defaults to @code{on}.
5403 @item show may-write-memory
5404 Show the current permission to write memory.
5406 @kindex may-insert-breakpoints
5407 @item set may-insert-breakpoints on
5408 @itemx set may-insert-breakpoints off
5409 This controls whether @value{GDBN} will attempt to insert breakpoints.
5410 This affects all breakpoints, including internal breakpoints defined
5411 by @value{GDBN}. It defaults to @code{on}.
5413 @item show may-insert-breakpoints
5414 Show the current permission to insert breakpoints.
5416 @kindex may-insert-tracepoints
5417 @item set may-insert-tracepoints on
5418 @itemx set may-insert-tracepoints off
5419 This controls whether @value{GDBN} will attempt to insert (regular)
5420 tracepoints at the beginning of a tracing experiment. It affects only
5421 non-fast tracepoints, fast tracepoints being under the control of
5422 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5424 @item show may-insert-tracepoints
5425 Show the current permission to insert tracepoints.
5427 @kindex may-insert-fast-tracepoints
5428 @item set may-insert-fast-tracepoints on
5429 @itemx set may-insert-fast-tracepoints off
5430 This controls whether @value{GDBN} will attempt to insert fast
5431 tracepoints at the beginning of a tracing experiment. It affects only
5432 fast tracepoints, regular (non-fast) tracepoints being under the
5433 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5435 @item show may-insert-fast-tracepoints
5436 Show the current permission to insert fast tracepoints.
5438 @kindex may-interrupt
5439 @item set may-interrupt on
5440 @itemx set may-interrupt off
5441 This controls whether @value{GDBN} will attempt to interrupt or stop
5442 program execution. When this variable is @code{off}, the
5443 @code{interrupt} command will have no effect, nor will
5444 @kbd{Ctrl-c}. It defaults to @code{on}.
5446 @item show may-interrupt
5447 Show the current permission to interrupt or stop the program.
5451 @node Reverse Execution
5452 @chapter Running programs backward
5453 @cindex reverse execution
5454 @cindex running programs backward
5456 When you are debugging a program, it is not unusual to realize that
5457 you have gone too far, and some event of interest has already happened.
5458 If the target environment supports it, @value{GDBN} can allow you to
5459 ``rewind'' the program by running it backward.
5461 A target environment that supports reverse execution should be able
5462 to ``undo'' the changes in machine state that have taken place as the
5463 program was executing normally. Variables, registers etc.@: should
5464 revert to their previous values. Obviously this requires a great
5465 deal of sophistication on the part of the target environment; not
5466 all target environments can support reverse execution.
5468 When a program is executed in reverse, the instructions that
5469 have most recently been executed are ``un-executed'', in reverse
5470 order. The program counter runs backward, following the previous
5471 thread of execution in reverse. As each instruction is ``un-executed'',
5472 the values of memory and/or registers that were changed by that
5473 instruction are reverted to their previous states. After executing
5474 a piece of source code in reverse, all side effects of that code
5475 should be ``undone'', and all variables should be returned to their
5476 prior values@footnote{
5477 Note that some side effects are easier to undo than others. For instance,
5478 memory and registers are relatively easy, but device I/O is hard. Some
5479 targets may be able undo things like device I/O, and some may not.
5481 The contract between @value{GDBN} and the reverse executing target
5482 requires only that the target do something reasonable when
5483 @value{GDBN} tells it to execute backwards, and then report the
5484 results back to @value{GDBN}. Whatever the target reports back to
5485 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5486 assumes that the memory and registers that the target reports are in a
5487 consistant state, but @value{GDBN} accepts whatever it is given.
5490 If you are debugging in a target environment that supports
5491 reverse execution, @value{GDBN} provides the following commands.
5494 @kindex reverse-continue
5495 @kindex rc @r{(@code{reverse-continue})}
5496 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5497 @itemx rc @r{[}@var{ignore-count}@r{]}
5498 Beginning at the point where your program last stopped, start executing
5499 in reverse. Reverse execution will stop for breakpoints and synchronous
5500 exceptions (signals), just like normal execution. Behavior of
5501 asynchronous signals depends on the target environment.
5503 @kindex reverse-step
5504 @kindex rs @r{(@code{step})}
5505 @item reverse-step @r{[}@var{count}@r{]}
5506 Run the program backward until control reaches the start of a
5507 different source line; then stop it, and return control to @value{GDBN}.
5509 Like the @code{step} command, @code{reverse-step} will only stop
5510 at the beginning of a source line. It ``un-executes'' the previously
5511 executed source line. If the previous source line included calls to
5512 debuggable functions, @code{reverse-step} will step (backward) into
5513 the called function, stopping at the beginning of the @emph{last}
5514 statement in the called function (typically a return statement).
5516 Also, as with the @code{step} command, if non-debuggable functions are
5517 called, @code{reverse-step} will run thru them backward without stopping.
5519 @kindex reverse-stepi
5520 @kindex rsi @r{(@code{reverse-stepi})}
5521 @item reverse-stepi @r{[}@var{count}@r{]}
5522 Reverse-execute one machine instruction. Note that the instruction
5523 to be reverse-executed is @emph{not} the one pointed to by the program
5524 counter, but the instruction executed prior to that one. For instance,
5525 if the last instruction was a jump, @code{reverse-stepi} will take you
5526 back from the destination of the jump to the jump instruction itself.
5528 @kindex reverse-next
5529 @kindex rn @r{(@code{reverse-next})}
5530 @item reverse-next @r{[}@var{count}@r{]}
5531 Run backward to the beginning of the previous line executed in
5532 the current (innermost) stack frame. If the line contains function
5533 calls, they will be ``un-executed'' without stopping. Starting from
5534 the first line of a function, @code{reverse-next} will take you back
5535 to the caller of that function, @emph{before} the function was called,
5536 just as the normal @code{next} command would take you from the last
5537 line of a function back to its return to its caller
5538 @footnote{Unless the code is too heavily optimized.}.
5540 @kindex reverse-nexti
5541 @kindex rni @r{(@code{reverse-nexti})}
5542 @item reverse-nexti @r{[}@var{count}@r{]}
5543 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5544 in reverse, except that called functions are ``un-executed'' atomically.
5545 That is, if the previously executed instruction was a return from
5546 another function, @code{reverse-nexti} will continue to execute
5547 in reverse until the call to that function (from the current stack
5550 @kindex reverse-finish
5551 @item reverse-finish
5552 Just as the @code{finish} command takes you to the point where the
5553 current function returns, @code{reverse-finish} takes you to the point
5554 where it was called. Instead of ending up at the end of the current
5555 function invocation, you end up at the beginning.
5557 @kindex set exec-direction
5558 @item set exec-direction
5559 Set the direction of target execution.
5560 @itemx set exec-direction reverse
5561 @cindex execute forward or backward in time
5562 @value{GDBN} will perform all execution commands in reverse, until the
5563 exec-direction mode is changed to ``forward''. Affected commands include
5564 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5565 command cannot be used in reverse mode.
5566 @item set exec-direction forward
5567 @value{GDBN} will perform all execution commands in the normal fashion.
5568 This is the default.
5572 @node Process Record and Replay
5573 @chapter Recording Inferior's Execution and Replaying It
5574 @cindex process record and replay
5575 @cindex recording inferior's execution and replaying it
5577 On some platforms, @value{GDBN} provides a special @dfn{process record
5578 and replay} target that can record a log of the process execution, and
5579 replay it later with both forward and reverse execution commands.
5582 When this target is in use, if the execution log includes the record
5583 for the next instruction, @value{GDBN} will debug in @dfn{replay
5584 mode}. In the replay mode, the inferior does not really execute code
5585 instructions. Instead, all the events that normally happen during
5586 code execution are taken from the execution log. While code is not
5587 really executed in replay mode, the values of registers (including the
5588 program counter register) and the memory of the inferior are still
5589 changed as they normally would. Their contents are taken from the
5593 If the record for the next instruction is not in the execution log,
5594 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5595 inferior executes normally, and @value{GDBN} records the execution log
5598 The process record and replay target supports reverse execution
5599 (@pxref{Reverse Execution}), even if the platform on which the
5600 inferior runs does not. However, the reverse execution is limited in
5601 this case by the range of the instructions recorded in the execution
5602 log. In other words, reverse execution on platforms that don't
5603 support it directly can only be done in the replay mode.
5605 When debugging in the reverse direction, @value{GDBN} will work in
5606 replay mode as long as the execution log includes the record for the
5607 previous instruction; otherwise, it will work in record mode, if the
5608 platform supports reverse execution, or stop if not.
5610 For architecture environments that support process record and replay,
5611 @value{GDBN} provides the following commands:
5614 @kindex target record
5618 This command starts the process record and replay target. The process
5619 record and replay target can only debug a process that is already
5620 running. Therefore, you need first to start the process with the
5621 @kbd{run} or @kbd{start} commands, and then start the recording with
5622 the @kbd{target record} command.
5624 Both @code{record} and @code{rec} are aliases of @code{target record}.
5626 @cindex displaced stepping, and process record and replay
5627 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5628 will be automatically disabled when process record and replay target
5629 is started. That's because the process record and replay target
5630 doesn't support displaced stepping.
5632 @cindex non-stop mode, and process record and replay
5633 @cindex asynchronous execution, and process record and replay
5634 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5635 the asynchronous execution mode (@pxref{Background Execution}), the
5636 process record and replay target cannot be started because it doesn't
5637 support these two modes.
5642 Stop the process record and replay target. When process record and
5643 replay target stops, the entire execution log will be deleted and the
5644 inferior will either be terminated, or will remain in its final state.
5646 When you stop the process record and replay target in record mode (at
5647 the end of the execution log), the inferior will be stopped at the
5648 next instruction that would have been recorded. In other words, if
5649 you record for a while and then stop recording, the inferior process
5650 will be left in the same state as if the recording never happened.
5652 On the other hand, if the process record and replay target is stopped
5653 while in replay mode (that is, not at the end of the execution log,
5654 but at some earlier point), the inferior process will become ``live''
5655 at that earlier state, and it will then be possible to continue the
5656 usual ``live'' debugging of the process from that state.
5658 When the inferior process exits, or @value{GDBN} detaches from it,
5659 process record and replay target will automatically stop itself.
5662 @item record save @var{filename}
5663 Save the execution log to a file @file{@var{filename}}.
5664 Default filename is @file{gdb_record.@var{process_id}}, where
5665 @var{process_id} is the process ID of the inferior.
5667 @kindex record restore
5668 @item record restore @var{filename}
5669 Restore the execution log from a file @file{@var{filename}}.
5670 File must have been created with @code{record save}.
5672 @kindex set record insn-number-max
5673 @item set record insn-number-max @var{limit}
5674 Set the limit of instructions to be recorded. Default value is 200000.
5676 If @var{limit} is a positive number, then @value{GDBN} will start
5677 deleting instructions from the log once the number of the record
5678 instructions becomes greater than @var{limit}. For every new recorded
5679 instruction, @value{GDBN} will delete the earliest recorded
5680 instruction to keep the number of recorded instructions at the limit.
5681 (Since deleting recorded instructions loses information, @value{GDBN}
5682 lets you control what happens when the limit is reached, by means of
5683 the @code{stop-at-limit} option, described below.)
5685 If @var{limit} is zero, @value{GDBN} will never delete recorded
5686 instructions from the execution log. The number of recorded
5687 instructions is unlimited in this case.
5689 @kindex show record insn-number-max
5690 @item show record insn-number-max
5691 Show the limit of instructions to be recorded.
5693 @kindex set record stop-at-limit
5694 @item set record stop-at-limit
5695 Control the behavior when the number of recorded instructions reaches
5696 the limit. If ON (the default), @value{GDBN} will stop when the limit
5697 is reached for the first time and ask you whether you want to stop the
5698 inferior or continue running it and recording the execution log. If
5699 you decide to continue recording, each new recorded instruction will
5700 cause the oldest one to be deleted.
5702 If this option is OFF, @value{GDBN} will automatically delete the
5703 oldest record to make room for each new one, without asking.
5705 @kindex show record stop-at-limit
5706 @item show record stop-at-limit
5707 Show the current setting of @code{stop-at-limit}.
5709 @kindex set record memory-query
5710 @item set record memory-query
5711 Control the behavior when @value{GDBN} is unable to record memory
5712 changes caused by an instruction. If ON, @value{GDBN} will query
5713 whether to stop the inferior in that case.
5715 If this option is OFF (the default), @value{GDBN} will automatically
5716 ignore the effect of such instructions on memory. Later, when
5717 @value{GDBN} replays this execution log, it will mark the log of this
5718 instruction as not accessible, and it will not affect the replay
5721 @kindex show record memory-query
5722 @item show record memory-query
5723 Show the current setting of @code{memory-query}.
5727 Show various statistics about the state of process record and its
5728 in-memory execution log buffer, including:
5732 Whether in record mode or replay mode.
5734 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5736 Highest recorded instruction number.
5738 Current instruction about to be replayed (if in replay mode).
5740 Number of instructions contained in the execution log.
5742 Maximum number of instructions that may be contained in the execution log.
5745 @kindex record delete
5748 When record target runs in replay mode (``in the past''), delete the
5749 subsequent execution log and begin to record a new execution log starting
5750 from the current address. This means you will abandon the previously
5751 recorded ``future'' and begin recording a new ``future''.
5756 @chapter Examining the Stack
5758 When your program has stopped, the first thing you need to know is where it
5759 stopped and how it got there.
5762 Each time your program performs a function call, information about the call
5764 That information includes the location of the call in your program,
5765 the arguments of the call,
5766 and the local variables of the function being called.
5767 The information is saved in a block of data called a @dfn{stack frame}.
5768 The stack frames are allocated in a region of memory called the @dfn{call
5771 When your program stops, the @value{GDBN} commands for examining the
5772 stack allow you to see all of this information.
5774 @cindex selected frame
5775 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5776 @value{GDBN} commands refer implicitly to the selected frame. In
5777 particular, whenever you ask @value{GDBN} for the value of a variable in
5778 your program, the value is found in the selected frame. There are
5779 special @value{GDBN} commands to select whichever frame you are
5780 interested in. @xref{Selection, ,Selecting a Frame}.
5782 When your program stops, @value{GDBN} automatically selects the
5783 currently executing frame and describes it briefly, similar to the
5784 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5787 * Frames:: Stack frames
5788 * Backtrace:: Backtraces
5789 * Selection:: Selecting a frame
5790 * Frame Info:: Information on a frame
5795 @section Stack Frames
5797 @cindex frame, definition
5799 The call stack is divided up into contiguous pieces called @dfn{stack
5800 frames}, or @dfn{frames} for short; each frame is the data associated
5801 with one call to one function. The frame contains the arguments given
5802 to the function, the function's local variables, and the address at
5803 which the function is executing.
5805 @cindex initial frame
5806 @cindex outermost frame
5807 @cindex innermost frame
5808 When your program is started, the stack has only one frame, that of the
5809 function @code{main}. This is called the @dfn{initial} frame or the
5810 @dfn{outermost} frame. Each time a function is called, a new frame is
5811 made. Each time a function returns, the frame for that function invocation
5812 is eliminated. If a function is recursive, there can be many frames for
5813 the same function. The frame for the function in which execution is
5814 actually occurring is called the @dfn{innermost} frame. This is the most
5815 recently created of all the stack frames that still exist.
5817 @cindex frame pointer
5818 Inside your program, stack frames are identified by their addresses. A
5819 stack frame consists of many bytes, each of which has its own address; each
5820 kind of computer has a convention for choosing one byte whose
5821 address serves as the address of the frame. Usually this address is kept
5822 in a register called the @dfn{frame pointer register}
5823 (@pxref{Registers, $fp}) while execution is going on in that frame.
5825 @cindex frame number
5826 @value{GDBN} assigns numbers to all existing stack frames, starting with
5827 zero for the innermost frame, one for the frame that called it,
5828 and so on upward. These numbers do not really exist in your program;
5829 they are assigned by @value{GDBN} to give you a way of designating stack
5830 frames in @value{GDBN} commands.
5832 @c The -fomit-frame-pointer below perennially causes hbox overflow
5833 @c underflow problems.
5834 @cindex frameless execution
5835 Some compilers provide a way to compile functions so that they operate
5836 without stack frames. (For example, the @value{NGCC} option
5838 @samp{-fomit-frame-pointer}
5840 generates functions without a frame.)
5841 This is occasionally done with heavily used library functions to save
5842 the frame setup time. @value{GDBN} has limited facilities for dealing
5843 with these function invocations. If the innermost function invocation
5844 has no stack frame, @value{GDBN} nevertheless regards it as though
5845 it had a separate frame, which is numbered zero as usual, allowing
5846 correct tracing of the function call chain. However, @value{GDBN} has
5847 no provision for frameless functions elsewhere in the stack.
5850 @kindex frame@r{, command}
5851 @cindex current stack frame
5852 @item frame @var{args}
5853 The @code{frame} command allows you to move from one stack frame to another,
5854 and to print the stack frame you select. @var{args} may be either the
5855 address of the frame or the stack frame number. Without an argument,
5856 @code{frame} prints the current stack frame.
5858 @kindex select-frame
5859 @cindex selecting frame silently
5861 The @code{select-frame} command allows you to move from one stack frame
5862 to another without printing the frame. This is the silent version of
5870 @cindex call stack traces
5871 A backtrace is a summary of how your program got where it is. It shows one
5872 line per frame, for many frames, starting with the currently executing
5873 frame (frame zero), followed by its caller (frame one), and on up the
5878 @kindex bt @r{(@code{backtrace})}
5881 Print a backtrace of the entire stack: one line per frame for all
5882 frames in the stack.
5884 You can stop the backtrace at any time by typing the system interrupt
5885 character, normally @kbd{Ctrl-c}.
5887 @item backtrace @var{n}
5889 Similar, but print only the innermost @var{n} frames.
5891 @item backtrace -@var{n}
5893 Similar, but print only the outermost @var{n} frames.
5895 @item backtrace full
5897 @itemx bt full @var{n}
5898 @itemx bt full -@var{n}
5899 Print the values of the local variables also. @var{n} specifies the
5900 number of frames to print, as described above.
5905 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5906 are additional aliases for @code{backtrace}.
5908 @cindex multiple threads, backtrace
5909 In a multi-threaded program, @value{GDBN} by default shows the
5910 backtrace only for the current thread. To display the backtrace for
5911 several or all of the threads, use the command @code{thread apply}
5912 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5913 apply all backtrace}, @value{GDBN} will display the backtrace for all
5914 the threads; this is handy when you debug a core dump of a
5915 multi-threaded program.
5917 Each line in the backtrace shows the frame number and the function name.
5918 The program counter value is also shown---unless you use @code{set
5919 print address off}. The backtrace also shows the source file name and
5920 line number, as well as the arguments to the function. The program
5921 counter value is omitted if it is at the beginning of the code for that
5924 Here is an example of a backtrace. It was made with the command
5925 @samp{bt 3}, so it shows the innermost three frames.
5929 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5931 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5932 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5934 (More stack frames follow...)
5939 The display for frame zero does not begin with a program counter
5940 value, indicating that your program has stopped at the beginning of the
5941 code for line @code{993} of @code{builtin.c}.
5944 The value of parameter @code{data} in frame 1 has been replaced by
5945 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5946 only if it is a scalar (integer, pointer, enumeration, etc). See command
5947 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5948 on how to configure the way function parameter values are printed.
5950 @cindex value optimized out, in backtrace
5951 @cindex function call arguments, optimized out
5952 If your program was compiled with optimizations, some compilers will
5953 optimize away arguments passed to functions if those arguments are
5954 never used after the call. Such optimizations generate code that
5955 passes arguments through registers, but doesn't store those arguments
5956 in the stack frame. @value{GDBN} has no way of displaying such
5957 arguments in stack frames other than the innermost one. Here's what
5958 such a backtrace might look like:
5962 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5964 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5965 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5967 (More stack frames follow...)
5972 The values of arguments that were not saved in their stack frames are
5973 shown as @samp{<value optimized out>}.
5975 If you need to display the values of such optimized-out arguments,
5976 either deduce that from other variables whose values depend on the one
5977 you are interested in, or recompile without optimizations.
5979 @cindex backtrace beyond @code{main} function
5980 @cindex program entry point
5981 @cindex startup code, and backtrace
5982 Most programs have a standard user entry point---a place where system
5983 libraries and startup code transition into user code. For C this is
5984 @code{main}@footnote{
5985 Note that embedded programs (the so-called ``free-standing''
5986 environment) are not required to have a @code{main} function as the
5987 entry point. They could even have multiple entry points.}.
5988 When @value{GDBN} finds the entry function in a backtrace
5989 it will terminate the backtrace, to avoid tracing into highly
5990 system-specific (and generally uninteresting) code.
5992 If you need to examine the startup code, or limit the number of levels
5993 in a backtrace, you can change this behavior:
5996 @item set backtrace past-main
5997 @itemx set backtrace past-main on
5998 @kindex set backtrace
5999 Backtraces will continue past the user entry point.
6001 @item set backtrace past-main off
6002 Backtraces will stop when they encounter the user entry point. This is the
6005 @item show backtrace past-main
6006 @kindex show backtrace
6007 Display the current user entry point backtrace policy.
6009 @item set backtrace past-entry
6010 @itemx set backtrace past-entry on
6011 Backtraces will continue past the internal entry point of an application.
6012 This entry point is encoded by the linker when the application is built,
6013 and is likely before the user entry point @code{main} (or equivalent) is called.
6015 @item set backtrace past-entry off
6016 Backtraces will stop when they encounter the internal entry point of an
6017 application. This is the default.
6019 @item show backtrace past-entry
6020 Display the current internal entry point backtrace policy.
6022 @item set backtrace limit @var{n}
6023 @itemx set backtrace limit 0
6024 @cindex backtrace limit
6025 Limit the backtrace to @var{n} levels. A value of zero means
6028 @item show backtrace limit
6029 Display the current limit on backtrace levels.
6033 @section Selecting a Frame
6035 Most commands for examining the stack and other data in your program work on
6036 whichever stack frame is selected at the moment. Here are the commands for
6037 selecting a stack frame; all of them finish by printing a brief description
6038 of the stack frame just selected.
6041 @kindex frame@r{, selecting}
6042 @kindex f @r{(@code{frame})}
6045 Select frame number @var{n}. Recall that frame zero is the innermost
6046 (currently executing) frame, frame one is the frame that called the
6047 innermost one, and so on. The highest-numbered frame is the one for
6050 @item frame @var{addr}
6052 Select the frame at address @var{addr}. This is useful mainly if the
6053 chaining of stack frames has been damaged by a bug, making it
6054 impossible for @value{GDBN} to assign numbers properly to all frames. In
6055 addition, this can be useful when your program has multiple stacks and
6056 switches between them.
6058 On the SPARC architecture, @code{frame} needs two addresses to
6059 select an arbitrary frame: a frame pointer and a stack pointer.
6061 On the MIPS and Alpha architecture, it needs two addresses: a stack
6062 pointer and a program counter.
6064 On the 29k architecture, it needs three addresses: a register stack
6065 pointer, a program counter, and a memory stack pointer.
6069 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6070 advances toward the outermost frame, to higher frame numbers, to frames
6071 that have existed longer. @var{n} defaults to one.
6074 @kindex do @r{(@code{down})}
6076 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6077 advances toward the innermost frame, to lower frame numbers, to frames
6078 that were created more recently. @var{n} defaults to one. You may
6079 abbreviate @code{down} as @code{do}.
6082 All of these commands end by printing two lines of output describing the
6083 frame. The first line shows the frame number, the function name, the
6084 arguments, and the source file and line number of execution in that
6085 frame. The second line shows the text of that source line.
6093 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6095 10 read_input_file (argv[i]);
6099 After such a printout, the @code{list} command with no arguments
6100 prints ten lines centered on the point of execution in the frame.
6101 You can also edit the program at the point of execution with your favorite
6102 editing program by typing @code{edit}.
6103 @xref{List, ,Printing Source Lines},
6107 @kindex down-silently
6109 @item up-silently @var{n}
6110 @itemx down-silently @var{n}
6111 These two commands are variants of @code{up} and @code{down},
6112 respectively; they differ in that they do their work silently, without
6113 causing display of the new frame. They are intended primarily for use
6114 in @value{GDBN} command scripts, where the output might be unnecessary and
6119 @section Information About a Frame
6121 There are several other commands to print information about the selected
6127 When used without any argument, this command does not change which
6128 frame is selected, but prints a brief description of the currently
6129 selected stack frame. It can be abbreviated @code{f}. With an
6130 argument, this command is used to select a stack frame.
6131 @xref{Selection, ,Selecting a Frame}.
6134 @kindex info f @r{(@code{info frame})}
6137 This command prints a verbose description of the selected stack frame,
6142 the address of the frame
6144 the address of the next frame down (called by this frame)
6146 the address of the next frame up (caller of this frame)
6148 the language in which the source code corresponding to this frame is written
6150 the address of the frame's arguments
6152 the address of the frame's local variables
6154 the program counter saved in it (the address of execution in the caller frame)
6156 which registers were saved in the frame
6159 @noindent The verbose description is useful when
6160 something has gone wrong that has made the stack format fail to fit
6161 the usual conventions.
6163 @item info frame @var{addr}
6164 @itemx info f @var{addr}
6165 Print a verbose description of the frame at address @var{addr}, without
6166 selecting that frame. The selected frame remains unchanged by this
6167 command. This requires the same kind of address (more than one for some
6168 architectures) that you specify in the @code{frame} command.
6169 @xref{Selection, ,Selecting a Frame}.
6173 Print the arguments of the selected frame, each on a separate line.
6177 Print the local variables of the selected frame, each on a separate
6178 line. These are all variables (declared either static or automatic)
6179 accessible at the point of execution of the selected frame.
6182 @cindex catch exceptions, list active handlers
6183 @cindex exception handlers, how to list
6185 Print a list of all the exception handlers that are active in the
6186 current stack frame at the current point of execution. To see other
6187 exception handlers, visit the associated frame (using the @code{up},
6188 @code{down}, or @code{frame} commands); then type @code{info catch}.
6189 @xref{Set Catchpoints, , Setting Catchpoints}.
6195 @chapter Examining Source Files
6197 @value{GDBN} can print parts of your program's source, since the debugging
6198 information recorded in the program tells @value{GDBN} what source files were
6199 used to build it. When your program stops, @value{GDBN} spontaneously prints
6200 the line where it stopped. Likewise, when you select a stack frame
6201 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6202 execution in that frame has stopped. You can print other portions of
6203 source files by explicit command.
6205 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6206 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6207 @value{GDBN} under @sc{gnu} Emacs}.
6210 * List:: Printing source lines
6211 * Specify Location:: How to specify code locations
6212 * Edit:: Editing source files
6213 * Search:: Searching source files
6214 * Source Path:: Specifying source directories
6215 * Machine Code:: Source and machine code
6219 @section Printing Source Lines
6222 @kindex l @r{(@code{list})}
6223 To print lines from a source file, use the @code{list} command
6224 (abbreviated @code{l}). By default, ten lines are printed.
6225 There are several ways to specify what part of the file you want to
6226 print; see @ref{Specify Location}, for the full list.
6228 Here are the forms of the @code{list} command most commonly used:
6231 @item list @var{linenum}
6232 Print lines centered around line number @var{linenum} in the
6233 current source file.
6235 @item list @var{function}
6236 Print lines centered around the beginning of function
6240 Print more lines. If the last lines printed were printed with a
6241 @code{list} command, this prints lines following the last lines
6242 printed; however, if the last line printed was a solitary line printed
6243 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6244 Stack}), this prints lines centered around that line.
6247 Print lines just before the lines last printed.
6250 @cindex @code{list}, how many lines to display
6251 By default, @value{GDBN} prints ten source lines with any of these forms of
6252 the @code{list} command. You can change this using @code{set listsize}:
6255 @kindex set listsize
6256 @item set listsize @var{count}
6257 Make the @code{list} command display @var{count} source lines (unless
6258 the @code{list} argument explicitly specifies some other number).
6260 @kindex show listsize
6262 Display the number of lines that @code{list} prints.
6265 Repeating a @code{list} command with @key{RET} discards the argument,
6266 so it is equivalent to typing just @code{list}. This is more useful
6267 than listing the same lines again. An exception is made for an
6268 argument of @samp{-}; that argument is preserved in repetition so that
6269 each repetition moves up in the source file.
6271 In general, the @code{list} command expects you to supply zero, one or two
6272 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6273 of writing them (@pxref{Specify Location}), but the effect is always
6274 to specify some source line.
6276 Here is a complete description of the possible arguments for @code{list}:
6279 @item list @var{linespec}
6280 Print lines centered around the line specified by @var{linespec}.
6282 @item list @var{first},@var{last}
6283 Print lines from @var{first} to @var{last}. Both arguments are
6284 linespecs. When a @code{list} command has two linespecs, and the
6285 source file of the second linespec is omitted, this refers to
6286 the same source file as the first linespec.
6288 @item list ,@var{last}
6289 Print lines ending with @var{last}.
6291 @item list @var{first},
6292 Print lines starting with @var{first}.
6295 Print lines just after the lines last printed.
6298 Print lines just before the lines last printed.
6301 As described in the preceding table.
6304 @node Specify Location
6305 @section Specifying a Location
6306 @cindex specifying location
6309 Several @value{GDBN} commands accept arguments that specify a location
6310 of your program's code. Since @value{GDBN} is a source-level
6311 debugger, a location usually specifies some line in the source code;
6312 for that reason, locations are also known as @dfn{linespecs}.
6314 Here are all the different ways of specifying a code location that
6315 @value{GDBN} understands:
6319 Specifies the line number @var{linenum} of the current source file.
6322 @itemx +@var{offset}
6323 Specifies the line @var{offset} lines before or after the @dfn{current
6324 line}. For the @code{list} command, the current line is the last one
6325 printed; for the breakpoint commands, this is the line at which
6326 execution stopped in the currently selected @dfn{stack frame}
6327 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6328 used as the second of the two linespecs in a @code{list} command,
6329 this specifies the line @var{offset} lines up or down from the first
6332 @item @var{filename}:@var{linenum}
6333 Specifies the line @var{linenum} in the source file @var{filename}.
6335 @item @var{function}
6336 Specifies the line that begins the body of the function @var{function}.
6337 For example, in C, this is the line with the open brace.
6339 @item @var{filename}:@var{function}
6340 Specifies the line that begins the body of the function @var{function}
6341 in the file @var{filename}. You only need the file name with a
6342 function name to avoid ambiguity when there are identically named
6343 functions in different source files.
6346 Specifies the line at which the label named @var{label} appears.
6347 @value{GDBN} searches for the label in the function corresponding to
6348 the currently selected stack frame. If there is no current selected
6349 stack frame (for instance, if the inferior is not running), then
6350 @value{GDBN} will not search for a label.
6352 @item *@var{address}
6353 Specifies the program address @var{address}. For line-oriented
6354 commands, such as @code{list} and @code{edit}, this specifies a source
6355 line that contains @var{address}. For @code{break} and other
6356 breakpoint oriented commands, this can be used to set breakpoints in
6357 parts of your program which do not have debugging information or
6360 Here @var{address} may be any expression valid in the current working
6361 language (@pxref{Languages, working language}) that specifies a code
6362 address. In addition, as a convenience, @value{GDBN} extends the
6363 semantics of expressions used in locations to cover the situations
6364 that frequently happen during debugging. Here are the various forms
6368 @item @var{expression}
6369 Any expression valid in the current working language.
6371 @item @var{funcaddr}
6372 An address of a function or procedure derived from its name. In C,
6373 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6374 simply the function's name @var{function} (and actually a special case
6375 of a valid expression). In Pascal and Modula-2, this is
6376 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6377 (although the Pascal form also works).
6379 This form specifies the address of the function's first instruction,
6380 before the stack frame and arguments have been set up.
6382 @item '@var{filename}'::@var{funcaddr}
6383 Like @var{funcaddr} above, but also specifies the name of the source
6384 file explicitly. This is useful if the name of the function does not
6385 specify the function unambiguously, e.g., if there are several
6386 functions with identical names in different source files.
6393 @section Editing Source Files
6394 @cindex editing source files
6397 @kindex e @r{(@code{edit})}
6398 To edit the lines in a source file, use the @code{edit} command.
6399 The editing program of your choice
6400 is invoked with the current line set to
6401 the active line in the program.
6402 Alternatively, there are several ways to specify what part of the file you
6403 want to print if you want to see other parts of the program:
6406 @item edit @var{location}
6407 Edit the source file specified by @code{location}. Editing starts at
6408 that @var{location}, e.g., at the specified source line of the
6409 specified file. @xref{Specify Location}, for all the possible forms
6410 of the @var{location} argument; here are the forms of the @code{edit}
6411 command most commonly used:
6414 @item edit @var{number}
6415 Edit the current source file with @var{number} as the active line number.
6417 @item edit @var{function}
6418 Edit the file containing @var{function} at the beginning of its definition.
6423 @subsection Choosing your Editor
6424 You can customize @value{GDBN} to use any editor you want
6426 The only restriction is that your editor (say @code{ex}), recognizes the
6427 following command-line syntax:
6429 ex +@var{number} file
6431 The optional numeric value +@var{number} specifies the number of the line in
6432 the file where to start editing.}.
6433 By default, it is @file{@value{EDITOR}}, but you can change this
6434 by setting the environment variable @code{EDITOR} before using
6435 @value{GDBN}. For example, to configure @value{GDBN} to use the
6436 @code{vi} editor, you could use these commands with the @code{sh} shell:
6442 or in the @code{csh} shell,
6444 setenv EDITOR /usr/bin/vi
6449 @section Searching Source Files
6450 @cindex searching source files
6452 There are two commands for searching through the current source file for a
6457 @kindex forward-search
6458 @item forward-search @var{regexp}
6459 @itemx search @var{regexp}
6460 The command @samp{forward-search @var{regexp}} checks each line,
6461 starting with the one following the last line listed, for a match for
6462 @var{regexp}. It lists the line that is found. You can use the
6463 synonym @samp{search @var{regexp}} or abbreviate the command name as
6466 @kindex reverse-search
6467 @item reverse-search @var{regexp}
6468 The command @samp{reverse-search @var{regexp}} checks each line, starting
6469 with the one before the last line listed and going backward, for a match
6470 for @var{regexp}. It lists the line that is found. You can abbreviate
6471 this command as @code{rev}.
6475 @section Specifying Source Directories
6478 @cindex directories for source files
6479 Executable programs sometimes do not record the directories of the source
6480 files from which they were compiled, just the names. Even when they do,
6481 the directories could be moved between the compilation and your debugging
6482 session. @value{GDBN} has a list of directories to search for source files;
6483 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6484 it tries all the directories in the list, in the order they are present
6485 in the list, until it finds a file with the desired name.
6487 For example, suppose an executable references the file
6488 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6489 @file{/mnt/cross}. The file is first looked up literally; if this
6490 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6491 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6492 message is printed. @value{GDBN} does not look up the parts of the
6493 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6494 Likewise, the subdirectories of the source path are not searched: if
6495 the source path is @file{/mnt/cross}, and the binary refers to
6496 @file{foo.c}, @value{GDBN} would not find it under
6497 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6499 Plain file names, relative file names with leading directories, file
6500 names containing dots, etc.@: are all treated as described above; for
6501 instance, if the source path is @file{/mnt/cross}, and the source file
6502 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6503 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6504 that---@file{/mnt/cross/foo.c}.
6506 Note that the executable search path is @emph{not} used to locate the
6509 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6510 any information it has cached about where source files are found and where
6511 each line is in the file.
6515 When you start @value{GDBN}, its source path includes only @samp{cdir}
6516 and @samp{cwd}, in that order.
6517 To add other directories, use the @code{directory} command.
6519 The search path is used to find both program source files and @value{GDBN}
6520 script files (read using the @samp{-command} option and @samp{source} command).
6522 In addition to the source path, @value{GDBN} provides a set of commands
6523 that manage a list of source path substitution rules. A @dfn{substitution
6524 rule} specifies how to rewrite source directories stored in the program's
6525 debug information in case the sources were moved to a different
6526 directory between compilation and debugging. A rule is made of
6527 two strings, the first specifying what needs to be rewritten in
6528 the path, and the second specifying how it should be rewritten.
6529 In @ref{set substitute-path}, we name these two parts @var{from} and
6530 @var{to} respectively. @value{GDBN} does a simple string replacement
6531 of @var{from} with @var{to} at the start of the directory part of the
6532 source file name, and uses that result instead of the original file
6533 name to look up the sources.
6535 Using the previous example, suppose the @file{foo-1.0} tree has been
6536 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6537 @value{GDBN} to replace @file{/usr/src} in all source path names with
6538 @file{/mnt/cross}. The first lookup will then be
6539 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6540 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6541 substitution rule, use the @code{set substitute-path} command
6542 (@pxref{set substitute-path}).
6544 To avoid unexpected substitution results, a rule is applied only if the
6545 @var{from} part of the directory name ends at a directory separator.
6546 For instance, a rule substituting @file{/usr/source} into
6547 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6548 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6549 is applied only at the beginning of the directory name, this rule will
6550 not be applied to @file{/root/usr/source/baz.c} either.
6552 In many cases, you can achieve the same result using the @code{directory}
6553 command. However, @code{set substitute-path} can be more efficient in
6554 the case where the sources are organized in a complex tree with multiple
6555 subdirectories. With the @code{directory} command, you need to add each
6556 subdirectory of your project. If you moved the entire tree while
6557 preserving its internal organization, then @code{set substitute-path}
6558 allows you to direct the debugger to all the sources with one single
6561 @code{set substitute-path} is also more than just a shortcut command.
6562 The source path is only used if the file at the original location no
6563 longer exists. On the other hand, @code{set substitute-path} modifies
6564 the debugger behavior to look at the rewritten location instead. So, if
6565 for any reason a source file that is not relevant to your executable is
6566 located at the original location, a substitution rule is the only
6567 method available to point @value{GDBN} at the new location.
6569 @cindex @samp{--with-relocated-sources}
6570 @cindex default source path substitution
6571 You can configure a default source path substitution rule by
6572 configuring @value{GDBN} with the
6573 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6574 should be the name of a directory under @value{GDBN}'s configured
6575 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6576 directory names in debug information under @var{dir} will be adjusted
6577 automatically if the installed @value{GDBN} is moved to a new
6578 location. This is useful if @value{GDBN}, libraries or executables
6579 with debug information and corresponding source code are being moved
6583 @item directory @var{dirname} @dots{}
6584 @item dir @var{dirname} @dots{}
6585 Add directory @var{dirname} to the front of the source path. Several
6586 directory names may be given to this command, separated by @samp{:}
6587 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6588 part of absolute file names) or
6589 whitespace. You may specify a directory that is already in the source
6590 path; this moves it forward, so @value{GDBN} searches it sooner.
6594 @vindex $cdir@r{, convenience variable}
6595 @vindex $cwd@r{, convenience variable}
6596 @cindex compilation directory
6597 @cindex current directory
6598 @cindex working directory
6599 @cindex directory, current
6600 @cindex directory, compilation
6601 You can use the string @samp{$cdir} to refer to the compilation
6602 directory (if one is recorded), and @samp{$cwd} to refer to the current
6603 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6604 tracks the current working directory as it changes during your @value{GDBN}
6605 session, while the latter is immediately expanded to the current
6606 directory at the time you add an entry to the source path.
6609 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6611 @c RET-repeat for @code{directory} is explicitly disabled, but since
6612 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6614 @item show directories
6615 @kindex show directories
6616 Print the source path: show which directories it contains.
6618 @anchor{set substitute-path}
6619 @item set substitute-path @var{from} @var{to}
6620 @kindex set substitute-path
6621 Define a source path substitution rule, and add it at the end of the
6622 current list of existing substitution rules. If a rule with the same
6623 @var{from} was already defined, then the old rule is also deleted.
6625 For example, if the file @file{/foo/bar/baz.c} was moved to
6626 @file{/mnt/cross/baz.c}, then the command
6629 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6633 will tell @value{GDBN} to replace @samp{/usr/src} with
6634 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6635 @file{baz.c} even though it was moved.
6637 In the case when more than one substitution rule have been defined,
6638 the rules are evaluated one by one in the order where they have been
6639 defined. The first one matching, if any, is selected to perform
6642 For instance, if we had entered the following commands:
6645 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6646 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6650 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6651 @file{/mnt/include/defs.h} by using the first rule. However, it would
6652 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6653 @file{/mnt/src/lib/foo.c}.
6656 @item unset substitute-path [path]
6657 @kindex unset substitute-path
6658 If a path is specified, search the current list of substitution rules
6659 for a rule that would rewrite that path. Delete that rule if found.
6660 A warning is emitted by the debugger if no rule could be found.
6662 If no path is specified, then all substitution rules are deleted.
6664 @item show substitute-path [path]
6665 @kindex show substitute-path
6666 If a path is specified, then print the source path substitution rule
6667 which would rewrite that path, if any.
6669 If no path is specified, then print all existing source path substitution
6674 If your source path is cluttered with directories that are no longer of
6675 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6676 versions of source. You can correct the situation as follows:
6680 Use @code{directory} with no argument to reset the source path to its default value.
6683 Use @code{directory} with suitable arguments to reinstall the
6684 directories you want in the source path. You can add all the
6685 directories in one command.
6689 @section Source and Machine Code
6690 @cindex source line and its code address
6692 You can use the command @code{info line} to map source lines to program
6693 addresses (and vice versa), and the command @code{disassemble} to display
6694 a range of addresses as machine instructions. You can use the command
6695 @code{set disassemble-next-line} to set whether to disassemble next
6696 source line when execution stops. When run under @sc{gnu} Emacs
6697 mode, the @code{info line} command causes the arrow to point to the
6698 line specified. Also, @code{info line} prints addresses in symbolic form as
6703 @item info line @var{linespec}
6704 Print the starting and ending addresses of the compiled code for
6705 source line @var{linespec}. You can specify source lines in any of
6706 the ways documented in @ref{Specify Location}.
6709 For example, we can use @code{info line} to discover the location of
6710 the object code for the first line of function
6711 @code{m4_changequote}:
6713 @c FIXME: I think this example should also show the addresses in
6714 @c symbolic form, as they usually would be displayed.
6716 (@value{GDBP}) info line m4_changequote
6717 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6721 @cindex code address and its source line
6722 We can also inquire (using @code{*@var{addr}} as the form for
6723 @var{linespec}) what source line covers a particular address:
6725 (@value{GDBP}) info line *0x63ff
6726 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6729 @cindex @code{$_} and @code{info line}
6730 @cindex @code{x} command, default address
6731 @kindex x@r{(examine), and} info line
6732 After @code{info line}, the default address for the @code{x} command
6733 is changed to the starting address of the line, so that @samp{x/i} is
6734 sufficient to begin examining the machine code (@pxref{Memory,
6735 ,Examining Memory}). Also, this address is saved as the value of the
6736 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6741 @cindex assembly instructions
6742 @cindex instructions, assembly
6743 @cindex machine instructions
6744 @cindex listing machine instructions
6746 @itemx disassemble /m
6747 @itemx disassemble /r
6748 This specialized command dumps a range of memory as machine
6749 instructions. It can also print mixed source+disassembly by specifying
6750 the @code{/m} modifier and print the raw instructions in hex as well as
6751 in symbolic form by specifying the @code{/r}.
6752 The default memory range is the function surrounding the
6753 program counter of the selected frame. A single argument to this
6754 command is a program counter value; @value{GDBN} dumps the function
6755 surrounding this value. When two arguments are given, they should
6756 be separated by a comma, possibly surrounded by whitespace. The
6757 arguments specify a range of addresses to dump, in one of two forms:
6760 @item @var{start},@var{end}
6761 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6762 @item @var{start},+@var{length}
6763 the addresses from @var{start} (inclusive) to
6764 @code{@var{start}+@var{length}} (exclusive).
6768 When 2 arguments are specified, the name of the function is also
6769 printed (since there could be several functions in the given range).
6771 The argument(s) can be any expression yielding a numeric value, such as
6772 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6774 If the range of memory being disassembled contains current program counter,
6775 the instruction at that location is shown with a @code{=>} marker.
6778 The following example shows the disassembly of a range of addresses of
6779 HP PA-RISC 2.0 code:
6782 (@value{GDBP}) disas 0x32c4, 0x32e4
6783 Dump of assembler code from 0x32c4 to 0x32e4:
6784 0x32c4 <main+204>: addil 0,dp
6785 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6786 0x32cc <main+212>: ldil 0x3000,r31
6787 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6788 0x32d4 <main+220>: ldo 0(r31),rp
6789 0x32d8 <main+224>: addil -0x800,dp
6790 0x32dc <main+228>: ldo 0x588(r1),r26
6791 0x32e0 <main+232>: ldil 0x3000,r31
6792 End of assembler dump.
6795 Here is an example showing mixed source+assembly for Intel x86, when the
6796 program is stopped just after function prologue:
6799 (@value{GDBP}) disas /m main
6800 Dump of assembler code for function main:
6802 0x08048330 <+0>: push %ebp
6803 0x08048331 <+1>: mov %esp,%ebp
6804 0x08048333 <+3>: sub $0x8,%esp
6805 0x08048336 <+6>: and $0xfffffff0,%esp
6806 0x08048339 <+9>: sub $0x10,%esp
6808 6 printf ("Hello.\n");
6809 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6810 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6814 0x08048348 <+24>: mov $0x0,%eax
6815 0x0804834d <+29>: leave
6816 0x0804834e <+30>: ret
6818 End of assembler dump.
6821 Here is another example showing raw instructions in hex for AMD x86-64,
6824 (gdb) disas /r 0x400281,+10
6825 Dump of assembler code from 0x400281 to 0x40028b:
6826 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6827 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6828 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6829 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6830 End of assembler dump.
6833 Some architectures have more than one commonly-used set of instruction
6834 mnemonics or other syntax.
6836 For programs that were dynamically linked and use shared libraries,
6837 instructions that call functions or branch to locations in the shared
6838 libraries might show a seemingly bogus location---it's actually a
6839 location of the relocation table. On some architectures, @value{GDBN}
6840 might be able to resolve these to actual function names.
6843 @kindex set disassembly-flavor
6844 @cindex Intel disassembly flavor
6845 @cindex AT&T disassembly flavor
6846 @item set disassembly-flavor @var{instruction-set}
6847 Select the instruction set to use when disassembling the
6848 program via the @code{disassemble} or @code{x/i} commands.
6850 Currently this command is only defined for the Intel x86 family. You
6851 can set @var{instruction-set} to either @code{intel} or @code{att}.
6852 The default is @code{att}, the AT&T flavor used by default by Unix
6853 assemblers for x86-based targets.
6855 @kindex show disassembly-flavor
6856 @item show disassembly-flavor
6857 Show the current setting of the disassembly flavor.
6861 @kindex set disassemble-next-line
6862 @kindex show disassemble-next-line
6863 @item set disassemble-next-line
6864 @itemx show disassemble-next-line
6865 Control whether or not @value{GDBN} will disassemble the next source
6866 line or instruction when execution stops. If ON, @value{GDBN} will
6867 display disassembly of the next source line when execution of the
6868 program being debugged stops. This is @emph{in addition} to
6869 displaying the source line itself, which @value{GDBN} always does if
6870 possible. If the next source line cannot be displayed for some reason
6871 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6872 info in the debug info), @value{GDBN} will display disassembly of the
6873 next @emph{instruction} instead of showing the next source line. If
6874 AUTO, @value{GDBN} will display disassembly of next instruction only
6875 if the source line cannot be displayed. This setting causes
6876 @value{GDBN} to display some feedback when you step through a function
6877 with no line info or whose source file is unavailable. The default is
6878 OFF, which means never display the disassembly of the next line or
6884 @chapter Examining Data
6886 @cindex printing data
6887 @cindex examining data
6890 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6891 @c document because it is nonstandard... Under Epoch it displays in a
6892 @c different window or something like that.
6893 The usual way to examine data in your program is with the @code{print}
6894 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6895 evaluates and prints the value of an expression of the language your
6896 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6897 Different Languages}). It may also print the expression using a
6898 Python-based pretty-printer (@pxref{Pretty Printing}).
6901 @item print @var{expr}
6902 @itemx print /@var{f} @var{expr}
6903 @var{expr} is an expression (in the source language). By default the
6904 value of @var{expr} is printed in a format appropriate to its data type;
6905 you can choose a different format by specifying @samp{/@var{f}}, where
6906 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6910 @itemx print /@var{f}
6911 @cindex reprint the last value
6912 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6913 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6914 conveniently inspect the same value in an alternative format.
6917 A more low-level way of examining data is with the @code{x} command.
6918 It examines data in memory at a specified address and prints it in a
6919 specified format. @xref{Memory, ,Examining Memory}.
6921 If you are interested in information about types, or about how the
6922 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6923 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6927 * Expressions:: Expressions
6928 * Ambiguous Expressions:: Ambiguous Expressions
6929 * Variables:: Program variables
6930 * Arrays:: Artificial arrays
6931 * Output Formats:: Output formats
6932 * Memory:: Examining memory
6933 * Auto Display:: Automatic display
6934 * Print Settings:: Print settings
6935 * Pretty Printing:: Python pretty printing
6936 * Value History:: Value history
6937 * Convenience Vars:: Convenience variables
6938 * Registers:: Registers
6939 * Floating Point Hardware:: Floating point hardware
6940 * Vector Unit:: Vector Unit
6941 * OS Information:: Auxiliary data provided by operating system
6942 * Memory Region Attributes:: Memory region attributes
6943 * Dump/Restore Files:: Copy between memory and a file
6944 * Core File Generation:: Cause a program dump its core
6945 * Character Sets:: Debugging programs that use a different
6946 character set than GDB does
6947 * Caching Remote Data:: Data caching for remote targets
6948 * Searching Memory:: Searching memory for a sequence of bytes
6952 @section Expressions
6955 @code{print} and many other @value{GDBN} commands accept an expression and
6956 compute its value. Any kind of constant, variable or operator defined
6957 by the programming language you are using is valid in an expression in
6958 @value{GDBN}. This includes conditional expressions, function calls,
6959 casts, and string constants. It also includes preprocessor macros, if
6960 you compiled your program to include this information; see
6963 @cindex arrays in expressions
6964 @value{GDBN} supports array constants in expressions input by
6965 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6966 you can use the command @code{print @{1, 2, 3@}} to create an array
6967 of three integers. If you pass an array to a function or assign it
6968 to a program variable, @value{GDBN} copies the array to memory that
6969 is @code{malloc}ed in the target program.
6971 Because C is so widespread, most of the expressions shown in examples in
6972 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6973 Languages}, for information on how to use expressions in other
6976 In this section, we discuss operators that you can use in @value{GDBN}
6977 expressions regardless of your programming language.
6979 @cindex casts, in expressions
6980 Casts are supported in all languages, not just in C, because it is so
6981 useful to cast a number into a pointer in order to examine a structure
6982 at that address in memory.
6983 @c FIXME: casts supported---Mod2 true?
6985 @value{GDBN} supports these operators, in addition to those common
6986 to programming languages:
6990 @samp{@@} is a binary operator for treating parts of memory as arrays.
6991 @xref{Arrays, ,Artificial Arrays}, for more information.
6994 @samp{::} allows you to specify a variable in terms of the file or
6995 function where it is defined. @xref{Variables, ,Program Variables}.
6997 @cindex @{@var{type}@}
6998 @cindex type casting memory
6999 @cindex memory, viewing as typed object
7000 @cindex casts, to view memory
7001 @item @{@var{type}@} @var{addr}
7002 Refers to an object of type @var{type} stored at address @var{addr} in
7003 memory. @var{addr} may be any expression whose value is an integer or
7004 pointer (but parentheses are required around binary operators, just as in
7005 a cast). This construct is allowed regardless of what kind of data is
7006 normally supposed to reside at @var{addr}.
7009 @node Ambiguous Expressions
7010 @section Ambiguous Expressions
7011 @cindex ambiguous expressions
7013 Expressions can sometimes contain some ambiguous elements. For instance,
7014 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7015 a single function name to be defined several times, for application in
7016 different contexts. This is called @dfn{overloading}. Another example
7017 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7018 templates and is typically instantiated several times, resulting in
7019 the same function name being defined in different contexts.
7021 In some cases and depending on the language, it is possible to adjust
7022 the expression to remove the ambiguity. For instance in C@t{++}, you
7023 can specify the signature of the function you want to break on, as in
7024 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7025 qualified name of your function often makes the expression unambiguous
7028 When an ambiguity that needs to be resolved is detected, the debugger
7029 has the capability to display a menu of numbered choices for each
7030 possibility, and then waits for the selection with the prompt @samp{>}.
7031 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7032 aborts the current command. If the command in which the expression was
7033 used allows more than one choice to be selected, the next option in the
7034 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7037 For example, the following session excerpt shows an attempt to set a
7038 breakpoint at the overloaded symbol @code{String::after}.
7039 We choose three particular definitions of that function name:
7041 @c FIXME! This is likely to change to show arg type lists, at least
7044 (@value{GDBP}) b String::after
7047 [2] file:String.cc; line number:867
7048 [3] file:String.cc; line number:860
7049 [4] file:String.cc; line number:875
7050 [5] file:String.cc; line number:853
7051 [6] file:String.cc; line number:846
7052 [7] file:String.cc; line number:735
7054 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7055 Breakpoint 2 at 0xb344: file String.cc, line 875.
7056 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7057 Multiple breakpoints were set.
7058 Use the "delete" command to delete unwanted
7065 @kindex set multiple-symbols
7066 @item set multiple-symbols @var{mode}
7067 @cindex multiple-symbols menu
7069 This option allows you to adjust the debugger behavior when an expression
7072 By default, @var{mode} is set to @code{all}. If the command with which
7073 the expression is used allows more than one choice, then @value{GDBN}
7074 automatically selects all possible choices. For instance, inserting
7075 a breakpoint on a function using an ambiguous name results in a breakpoint
7076 inserted on each possible match. However, if a unique choice must be made,
7077 then @value{GDBN} uses the menu to help you disambiguate the expression.
7078 For instance, printing the address of an overloaded function will result
7079 in the use of the menu.
7081 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7082 when an ambiguity is detected.
7084 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7085 an error due to the ambiguity and the command is aborted.
7087 @kindex show multiple-symbols
7088 @item show multiple-symbols
7089 Show the current value of the @code{multiple-symbols} setting.
7093 @section Program Variables
7095 The most common kind of expression to use is the name of a variable
7098 Variables in expressions are understood in the selected stack frame
7099 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7103 global (or file-static)
7110 visible according to the scope rules of the
7111 programming language from the point of execution in that frame
7114 @noindent This means that in the function
7129 you can examine and use the variable @code{a} whenever your program is
7130 executing within the function @code{foo}, but you can only use or
7131 examine the variable @code{b} while your program is executing inside
7132 the block where @code{b} is declared.
7134 @cindex variable name conflict
7135 There is an exception: you can refer to a variable or function whose
7136 scope is a single source file even if the current execution point is not
7137 in this file. But it is possible to have more than one such variable or
7138 function with the same name (in different source files). If that
7139 happens, referring to that name has unpredictable effects. If you wish,
7140 you can specify a static variable in a particular function or file,
7141 using the colon-colon (@code{::}) notation:
7143 @cindex colon-colon, context for variables/functions
7145 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7146 @cindex @code{::}, context for variables/functions
7149 @var{file}::@var{variable}
7150 @var{function}::@var{variable}
7154 Here @var{file} or @var{function} is the name of the context for the
7155 static @var{variable}. In the case of file names, you can use quotes to
7156 make sure @value{GDBN} parses the file name as a single word---for example,
7157 to print a global value of @code{x} defined in @file{f2.c}:
7160 (@value{GDBP}) p 'f2.c'::x
7163 @cindex C@t{++} scope resolution
7164 This use of @samp{::} is very rarely in conflict with the very similar
7165 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7166 scope resolution operator in @value{GDBN} expressions.
7167 @c FIXME: Um, so what happens in one of those rare cases where it's in
7170 @cindex wrong values
7171 @cindex variable values, wrong
7172 @cindex function entry/exit, wrong values of variables
7173 @cindex optimized code, wrong values of variables
7175 @emph{Warning:} Occasionally, a local variable may appear to have the
7176 wrong value at certain points in a function---just after entry to a new
7177 scope, and just before exit.
7179 You may see this problem when you are stepping by machine instructions.
7180 This is because, on most machines, it takes more than one instruction to
7181 set up a stack frame (including local variable definitions); if you are
7182 stepping by machine instructions, variables may appear to have the wrong
7183 values until the stack frame is completely built. On exit, it usually
7184 also takes more than one machine instruction to destroy a stack frame;
7185 after you begin stepping through that group of instructions, local
7186 variable definitions may be gone.
7188 This may also happen when the compiler does significant optimizations.
7189 To be sure of always seeing accurate values, turn off all optimization
7192 @cindex ``No symbol "foo" in current context''
7193 Another possible effect of compiler optimizations is to optimize
7194 unused variables out of existence, or assign variables to registers (as
7195 opposed to memory addresses). Depending on the support for such cases
7196 offered by the debug info format used by the compiler, @value{GDBN}
7197 might not be able to display values for such local variables. If that
7198 happens, @value{GDBN} will print a message like this:
7201 No symbol "foo" in current context.
7204 To solve such problems, either recompile without optimizations, or use a
7205 different debug info format, if the compiler supports several such
7206 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7207 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7208 produces debug info in a format that is superior to formats such as
7209 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7210 an effective form for debug info. @xref{Debugging Options,,Options
7211 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7212 Compiler Collection (GCC)}.
7213 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7214 that are best suited to C@t{++} programs.
7216 If you ask to print an object whose contents are unknown to
7217 @value{GDBN}, e.g., because its data type is not completely specified
7218 by the debug information, @value{GDBN} will say @samp{<incomplete
7219 type>}. @xref{Symbols, incomplete type}, for more about this.
7221 Strings are identified as arrays of @code{char} values without specified
7222 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7223 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7224 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7225 defines literal string type @code{"char"} as @code{char} without a sign.
7230 signed char var1[] = "A";
7233 You get during debugging
7238 $2 = @{65 'A', 0 '\0'@}
7242 @section Artificial Arrays
7244 @cindex artificial array
7246 @kindex @@@r{, referencing memory as an array}
7247 It is often useful to print out several successive objects of the
7248 same type in memory; a section of an array, or an array of
7249 dynamically determined size for which only a pointer exists in the
7252 You can do this by referring to a contiguous span of memory as an
7253 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7254 operand of @samp{@@} should be the first element of the desired array
7255 and be an individual object. The right operand should be the desired length
7256 of the array. The result is an array value whose elements are all of
7257 the type of the left argument. The first element is actually the left
7258 argument; the second element comes from bytes of memory immediately
7259 following those that hold the first element, and so on. Here is an
7260 example. If a program says
7263 int *array = (int *) malloc (len * sizeof (int));
7267 you can print the contents of @code{array} with
7273 The left operand of @samp{@@} must reside in memory. Array values made
7274 with @samp{@@} in this way behave just like other arrays in terms of
7275 subscripting, and are coerced to pointers when used in expressions.
7276 Artificial arrays most often appear in expressions via the value history
7277 (@pxref{Value History, ,Value History}), after printing one out.
7279 Another way to create an artificial array is to use a cast.
7280 This re-interprets a value as if it were an array.
7281 The value need not be in memory:
7283 (@value{GDBP}) p/x (short[2])0x12345678
7284 $1 = @{0x1234, 0x5678@}
7287 As a convenience, if you leave the array length out (as in
7288 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7289 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7291 (@value{GDBP}) p/x (short[])0x12345678
7292 $2 = @{0x1234, 0x5678@}
7295 Sometimes the artificial array mechanism is not quite enough; in
7296 moderately complex data structures, the elements of interest may not
7297 actually be adjacent---for example, if you are interested in the values
7298 of pointers in an array. One useful work-around in this situation is
7299 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7300 Variables}) as a counter in an expression that prints the first
7301 interesting value, and then repeat that expression via @key{RET}. For
7302 instance, suppose you have an array @code{dtab} of pointers to
7303 structures, and you are interested in the values of a field @code{fv}
7304 in each structure. Here is an example of what you might type:
7314 @node Output Formats
7315 @section Output Formats
7317 @cindex formatted output
7318 @cindex output formats
7319 By default, @value{GDBN} prints a value according to its data type. Sometimes
7320 this is not what you want. For example, you might want to print a number
7321 in hex, or a pointer in decimal. Or you might want to view data in memory
7322 at a certain address as a character string or as an instruction. To do
7323 these things, specify an @dfn{output format} when you print a value.
7325 The simplest use of output formats is to say how to print a value
7326 already computed. This is done by starting the arguments of the
7327 @code{print} command with a slash and a format letter. The format
7328 letters supported are:
7332 Regard the bits of the value as an integer, and print the integer in
7336 Print as integer in signed decimal.
7339 Print as integer in unsigned decimal.
7342 Print as integer in octal.
7345 Print as integer in binary. The letter @samp{t} stands for ``two''.
7346 @footnote{@samp{b} cannot be used because these format letters are also
7347 used with the @code{x} command, where @samp{b} stands for ``byte'';
7348 see @ref{Memory,,Examining Memory}.}
7351 @cindex unknown address, locating
7352 @cindex locate address
7353 Print as an address, both absolute in hexadecimal and as an offset from
7354 the nearest preceding symbol. You can use this format used to discover
7355 where (in what function) an unknown address is located:
7358 (@value{GDBP}) p/a 0x54320
7359 $3 = 0x54320 <_initialize_vx+396>
7363 The command @code{info symbol 0x54320} yields similar results.
7364 @xref{Symbols, info symbol}.
7367 Regard as an integer and print it as a character constant. This
7368 prints both the numerical value and its character representation. The
7369 character representation is replaced with the octal escape @samp{\nnn}
7370 for characters outside the 7-bit @sc{ascii} range.
7372 Without this format, @value{GDBN} displays @code{char},
7373 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7374 constants. Single-byte members of vectors are displayed as integer
7378 Regard the bits of the value as a floating point number and print
7379 using typical floating point syntax.
7382 @cindex printing strings
7383 @cindex printing byte arrays
7384 Regard as a string, if possible. With this format, pointers to single-byte
7385 data are displayed as null-terminated strings and arrays of single-byte data
7386 are displayed as fixed-length strings. Other values are displayed in their
7389 Without this format, @value{GDBN} displays pointers to and arrays of
7390 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7391 strings. Single-byte members of a vector are displayed as an integer
7395 @cindex raw printing
7396 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7397 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7398 Printing}). This typically results in a higher-level display of the
7399 value's contents. The @samp{r} format bypasses any Python
7400 pretty-printer which might exist.
7403 For example, to print the program counter in hex (@pxref{Registers}), type
7410 Note that no space is required before the slash; this is because command
7411 names in @value{GDBN} cannot contain a slash.
7413 To reprint the last value in the value history with a different format,
7414 you can use the @code{print} command with just a format and no
7415 expression. For example, @samp{p/x} reprints the last value in hex.
7418 @section Examining Memory
7420 You can use the command @code{x} (for ``examine'') to examine memory in
7421 any of several formats, independently of your program's data types.
7423 @cindex examining memory
7425 @kindex x @r{(examine memory)}
7426 @item x/@var{nfu} @var{addr}
7429 Use the @code{x} command to examine memory.
7432 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7433 much memory to display and how to format it; @var{addr} is an
7434 expression giving the address where you want to start displaying memory.
7435 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7436 Several commands set convenient defaults for @var{addr}.
7439 @item @var{n}, the repeat count
7440 The repeat count is a decimal integer; the default is 1. It specifies
7441 how much memory (counting by units @var{u}) to display.
7442 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7445 @item @var{f}, the display format
7446 The display format is one of the formats used by @code{print}
7447 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7448 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7449 The default is @samp{x} (hexadecimal) initially. The default changes
7450 each time you use either @code{x} or @code{print}.
7452 @item @var{u}, the unit size
7453 The unit size is any of
7459 Halfwords (two bytes).
7461 Words (four bytes). This is the initial default.
7463 Giant words (eight bytes).
7466 Each time you specify a unit size with @code{x}, that size becomes the
7467 default unit the next time you use @code{x}. For the @samp{i} format,
7468 the unit size is ignored and is normally not written. For the @samp{s} format,
7469 the unit size defaults to @samp{b}, unless it is explicitly given.
7470 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7471 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7472 Note that the results depend on the programming language of the
7473 current compilation unit. If the language is C, the @samp{s}
7474 modifier will use the UTF-16 encoding while @samp{w} will use
7475 UTF-32. The encoding is set by the programming language and cannot
7478 @item @var{addr}, starting display address
7479 @var{addr} is the address where you want @value{GDBN} to begin displaying
7480 memory. The expression need not have a pointer value (though it may);
7481 it is always interpreted as an integer address of a byte of memory.
7482 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7483 @var{addr} is usually just after the last address examined---but several
7484 other commands also set the default address: @code{info breakpoints} (to
7485 the address of the last breakpoint listed), @code{info line} (to the
7486 starting address of a line), and @code{print} (if you use it to display
7487 a value from memory).
7490 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7491 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7492 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7493 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7494 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7496 Since the letters indicating unit sizes are all distinct from the
7497 letters specifying output formats, you do not have to remember whether
7498 unit size or format comes first; either order works. The output
7499 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7500 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7502 Even though the unit size @var{u} is ignored for the formats @samp{s}
7503 and @samp{i}, you might still want to use a count @var{n}; for example,
7504 @samp{3i} specifies that you want to see three machine instructions,
7505 including any operands. For convenience, especially when used with
7506 the @code{display} command, the @samp{i} format also prints branch delay
7507 slot instructions, if any, beyond the count specified, which immediately
7508 follow the last instruction that is within the count. The command
7509 @code{disassemble} gives an alternative way of inspecting machine
7510 instructions; see @ref{Machine Code,,Source and Machine Code}.
7512 All the defaults for the arguments to @code{x} are designed to make it
7513 easy to continue scanning memory with minimal specifications each time
7514 you use @code{x}. For example, after you have inspected three machine
7515 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7516 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7517 the repeat count @var{n} is used again; the other arguments default as
7518 for successive uses of @code{x}.
7520 When examining machine instructions, the instruction at current program
7521 counter is shown with a @code{=>} marker. For example:
7524 (@value{GDBP}) x/5i $pc-6
7525 0x804837f <main+11>: mov %esp,%ebp
7526 0x8048381 <main+13>: push %ecx
7527 0x8048382 <main+14>: sub $0x4,%esp
7528 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7529 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7532 @cindex @code{$_}, @code{$__}, and value history
7533 The addresses and contents printed by the @code{x} command are not saved
7534 in the value history because there is often too much of them and they
7535 would get in the way. Instead, @value{GDBN} makes these values available for
7536 subsequent use in expressions as values of the convenience variables
7537 @code{$_} and @code{$__}. After an @code{x} command, the last address
7538 examined is available for use in expressions in the convenience variable
7539 @code{$_}. The contents of that address, as examined, are available in
7540 the convenience variable @code{$__}.
7542 If the @code{x} command has a repeat count, the address and contents saved
7543 are from the last memory unit printed; this is not the same as the last
7544 address printed if several units were printed on the last line of output.
7546 @cindex remote memory comparison
7547 @cindex verify remote memory image
7548 When you are debugging a program running on a remote target machine
7549 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7550 remote machine's memory against the executable file you downloaded to
7551 the target. The @code{compare-sections} command is provided for such
7555 @kindex compare-sections
7556 @item compare-sections @r{[}@var{section-name}@r{]}
7557 Compare the data of a loadable section @var{section-name} in the
7558 executable file of the program being debugged with the same section in
7559 the remote machine's memory, and report any mismatches. With no
7560 arguments, compares all loadable sections. This command's
7561 availability depends on the target's support for the @code{"qCRC"}
7566 @section Automatic Display
7567 @cindex automatic display
7568 @cindex display of expressions
7570 If you find that you want to print the value of an expression frequently
7571 (to see how it changes), you might want to add it to the @dfn{automatic
7572 display list} so that @value{GDBN} prints its value each time your program stops.
7573 Each expression added to the list is given a number to identify it;
7574 to remove an expression from the list, you specify that number.
7575 The automatic display looks like this:
7579 3: bar[5] = (struct hack *) 0x3804
7583 This display shows item numbers, expressions and their current values. As with
7584 displays you request manually using @code{x} or @code{print}, you can
7585 specify the output format you prefer; in fact, @code{display} decides
7586 whether to use @code{print} or @code{x} depending your format
7587 specification---it uses @code{x} if you specify either the @samp{i}
7588 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7592 @item display @var{expr}
7593 Add the expression @var{expr} to the list of expressions to display
7594 each time your program stops. @xref{Expressions, ,Expressions}.
7596 @code{display} does not repeat if you press @key{RET} again after using it.
7598 @item display/@var{fmt} @var{expr}
7599 For @var{fmt} specifying only a display format and not a size or
7600 count, add the expression @var{expr} to the auto-display list but
7601 arrange to display it each time in the specified format @var{fmt}.
7602 @xref{Output Formats,,Output Formats}.
7604 @item display/@var{fmt} @var{addr}
7605 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7606 number of units, add the expression @var{addr} as a memory address to
7607 be examined each time your program stops. Examining means in effect
7608 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7611 For example, @samp{display/i $pc} can be helpful, to see the machine
7612 instruction about to be executed each time execution stops (@samp{$pc}
7613 is a common name for the program counter; @pxref{Registers, ,Registers}).
7616 @kindex delete display
7618 @item undisplay @var{dnums}@dots{}
7619 @itemx delete display @var{dnums}@dots{}
7620 Remove item numbers @var{dnums} from the list of expressions to display.
7622 @code{undisplay} does not repeat if you press @key{RET} after using it.
7623 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7625 @kindex disable display
7626 @item disable display @var{dnums}@dots{}
7627 Disable the display of item numbers @var{dnums}. A disabled display
7628 item is not printed automatically, but is not forgotten. It may be
7629 enabled again later.
7631 @kindex enable display
7632 @item enable display @var{dnums}@dots{}
7633 Enable display of item numbers @var{dnums}. It becomes effective once
7634 again in auto display of its expression, until you specify otherwise.
7637 Display the current values of the expressions on the list, just as is
7638 done when your program stops.
7640 @kindex info display
7642 Print the list of expressions previously set up to display
7643 automatically, each one with its item number, but without showing the
7644 values. This includes disabled expressions, which are marked as such.
7645 It also includes expressions which would not be displayed right now
7646 because they refer to automatic variables not currently available.
7649 @cindex display disabled out of scope
7650 If a display expression refers to local variables, then it does not make
7651 sense outside the lexical context for which it was set up. Such an
7652 expression is disabled when execution enters a context where one of its
7653 variables is not defined. For example, if you give the command
7654 @code{display last_char} while inside a function with an argument
7655 @code{last_char}, @value{GDBN} displays this argument while your program
7656 continues to stop inside that function. When it stops elsewhere---where
7657 there is no variable @code{last_char}---the display is disabled
7658 automatically. The next time your program stops where @code{last_char}
7659 is meaningful, you can enable the display expression once again.
7661 @node Print Settings
7662 @section Print Settings
7664 @cindex format options
7665 @cindex print settings
7666 @value{GDBN} provides the following ways to control how arrays, structures,
7667 and symbols are printed.
7670 These settings are useful for debugging programs in any language:
7674 @item set print address
7675 @itemx set print address on
7676 @cindex print/don't print memory addresses
7677 @value{GDBN} prints memory addresses showing the location of stack
7678 traces, structure values, pointer values, breakpoints, and so forth,
7679 even when it also displays the contents of those addresses. The default
7680 is @code{on}. For example, this is what a stack frame display looks like with
7681 @code{set print address on}:
7686 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7688 530 if (lquote != def_lquote)
7692 @item set print address off
7693 Do not print addresses when displaying their contents. For example,
7694 this is the same stack frame displayed with @code{set print address off}:
7698 (@value{GDBP}) set print addr off
7700 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7701 530 if (lquote != def_lquote)
7705 You can use @samp{set print address off} to eliminate all machine
7706 dependent displays from the @value{GDBN} interface. For example, with
7707 @code{print address off}, you should get the same text for backtraces on
7708 all machines---whether or not they involve pointer arguments.
7711 @item show print address
7712 Show whether or not addresses are to be printed.
7715 When @value{GDBN} prints a symbolic address, it normally prints the
7716 closest earlier symbol plus an offset. If that symbol does not uniquely
7717 identify the address (for example, it is a name whose scope is a single
7718 source file), you may need to clarify. One way to do this is with
7719 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7720 you can set @value{GDBN} to print the source file and line number when
7721 it prints a symbolic address:
7724 @item set print symbol-filename on
7725 @cindex source file and line of a symbol
7726 @cindex symbol, source file and line
7727 Tell @value{GDBN} to print the source file name and line number of a
7728 symbol in the symbolic form of an address.
7730 @item set print symbol-filename off
7731 Do not print source file name and line number of a symbol. This is the
7734 @item show print symbol-filename
7735 Show whether or not @value{GDBN} will print the source file name and
7736 line number of a symbol in the symbolic form of an address.
7739 Another situation where it is helpful to show symbol filenames and line
7740 numbers is when disassembling code; @value{GDBN} shows you the line
7741 number and source file that corresponds to each instruction.
7743 Also, you may wish to see the symbolic form only if the address being
7744 printed is reasonably close to the closest earlier symbol:
7747 @item set print max-symbolic-offset @var{max-offset}
7748 @cindex maximum value for offset of closest symbol
7749 Tell @value{GDBN} to only display the symbolic form of an address if the
7750 offset between the closest earlier symbol and the address is less than
7751 @var{max-offset}. The default is 0, which tells @value{GDBN}
7752 to always print the symbolic form of an address if any symbol precedes it.
7754 @item show print max-symbolic-offset
7755 Ask how large the maximum offset is that @value{GDBN} prints in a
7759 @cindex wild pointer, interpreting
7760 @cindex pointer, finding referent
7761 If you have a pointer and you are not sure where it points, try
7762 @samp{set print symbol-filename on}. Then you can determine the name
7763 and source file location of the variable where it points, using
7764 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7765 For example, here @value{GDBN} shows that a variable @code{ptt} points
7766 at another variable @code{t}, defined in @file{hi2.c}:
7769 (@value{GDBP}) set print symbol-filename on
7770 (@value{GDBP}) p/a ptt
7771 $4 = 0xe008 <t in hi2.c>
7775 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7776 does not show the symbol name and filename of the referent, even with
7777 the appropriate @code{set print} options turned on.
7780 Other settings control how different kinds of objects are printed:
7783 @item set print array
7784 @itemx set print array on
7785 @cindex pretty print arrays
7786 Pretty print arrays. This format is more convenient to read,
7787 but uses more space. The default is off.
7789 @item set print array off
7790 Return to compressed format for arrays.
7792 @item show print array
7793 Show whether compressed or pretty format is selected for displaying
7796 @cindex print array indexes
7797 @item set print array-indexes
7798 @itemx set print array-indexes on
7799 Print the index of each element when displaying arrays. May be more
7800 convenient to locate a given element in the array or quickly find the
7801 index of a given element in that printed array. The default is off.
7803 @item set print array-indexes off
7804 Stop printing element indexes when displaying arrays.
7806 @item show print array-indexes
7807 Show whether the index of each element is printed when displaying
7810 @item set print elements @var{number-of-elements}
7811 @cindex number of array elements to print
7812 @cindex limit on number of printed array elements
7813 Set a limit on how many elements of an array @value{GDBN} will print.
7814 If @value{GDBN} is printing a large array, it stops printing after it has
7815 printed the number of elements set by the @code{set print elements} command.
7816 This limit also applies to the display of strings.
7817 When @value{GDBN} starts, this limit is set to 200.
7818 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7820 @item show print elements
7821 Display the number of elements of a large array that @value{GDBN} will print.
7822 If the number is 0, then the printing is unlimited.
7824 @item set print frame-arguments @var{value}
7825 @kindex set print frame-arguments
7826 @cindex printing frame argument values
7827 @cindex print all frame argument values
7828 @cindex print frame argument values for scalars only
7829 @cindex do not print frame argument values
7830 This command allows to control how the values of arguments are printed
7831 when the debugger prints a frame (@pxref{Frames}). The possible
7836 The values of all arguments are printed.
7839 Print the value of an argument only if it is a scalar. The value of more
7840 complex arguments such as arrays, structures, unions, etc, is replaced
7841 by @code{@dots{}}. This is the default. Here is an example where
7842 only scalar arguments are shown:
7845 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7850 None of the argument values are printed. Instead, the value of each argument
7851 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7854 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7859 By default, only scalar arguments are printed. This command can be used
7860 to configure the debugger to print the value of all arguments, regardless
7861 of their type. However, it is often advantageous to not print the value
7862 of more complex parameters. For instance, it reduces the amount of
7863 information printed in each frame, making the backtrace more readable.
7864 Also, it improves performance when displaying Ada frames, because
7865 the computation of large arguments can sometimes be CPU-intensive,
7866 especially in large applications. Setting @code{print frame-arguments}
7867 to @code{scalars} (the default) or @code{none} avoids this computation,
7868 thus speeding up the display of each Ada frame.
7870 @item show print frame-arguments
7871 Show how the value of arguments should be displayed when printing a frame.
7873 @item set print repeats
7874 @cindex repeated array elements
7875 Set the threshold for suppressing display of repeated array
7876 elements. When the number of consecutive identical elements of an
7877 array exceeds the threshold, @value{GDBN} prints the string
7878 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7879 identical repetitions, instead of displaying the identical elements
7880 themselves. Setting the threshold to zero will cause all elements to
7881 be individually printed. The default threshold is 10.
7883 @item show print repeats
7884 Display the current threshold for printing repeated identical
7887 @item set print null-stop
7888 @cindex @sc{null} elements in arrays
7889 Cause @value{GDBN} to stop printing the characters of an array when the first
7890 @sc{null} is encountered. This is useful when large arrays actually
7891 contain only short strings.
7894 @item show print null-stop
7895 Show whether @value{GDBN} stops printing an array on the first
7896 @sc{null} character.
7898 @item set print pretty on
7899 @cindex print structures in indented form
7900 @cindex indentation in structure display
7901 Cause @value{GDBN} to print structures in an indented format with one member
7902 per line, like this:
7917 @item set print pretty off
7918 Cause @value{GDBN} to print structures in a compact format, like this:
7922 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7923 meat = 0x54 "Pork"@}
7928 This is the default format.
7930 @item show print pretty
7931 Show which format @value{GDBN} is using to print structures.
7933 @item set print sevenbit-strings on
7934 @cindex eight-bit characters in strings
7935 @cindex octal escapes in strings
7936 Print using only seven-bit characters; if this option is set,
7937 @value{GDBN} displays any eight-bit characters (in strings or
7938 character values) using the notation @code{\}@var{nnn}. This setting is
7939 best if you are working in English (@sc{ascii}) and you use the
7940 high-order bit of characters as a marker or ``meta'' bit.
7942 @item set print sevenbit-strings off
7943 Print full eight-bit characters. This allows the use of more
7944 international character sets, and is the default.
7946 @item show print sevenbit-strings
7947 Show whether or not @value{GDBN} is printing only seven-bit characters.
7949 @item set print union on
7950 @cindex unions in structures, printing
7951 Tell @value{GDBN} to print unions which are contained in structures
7952 and other unions. This is the default setting.
7954 @item set print union off
7955 Tell @value{GDBN} not to print unions which are contained in
7956 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7959 @item show print union
7960 Ask @value{GDBN} whether or not it will print unions which are contained in
7961 structures and other unions.
7963 For example, given the declarations
7966 typedef enum @{Tree, Bug@} Species;
7967 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7968 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7979 struct thing foo = @{Tree, @{Acorn@}@};
7983 with @code{set print union on} in effect @samp{p foo} would print
7986 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7990 and with @code{set print union off} in effect it would print
7993 $1 = @{it = Tree, form = @{...@}@}
7997 @code{set print union} affects programs written in C-like languages
8003 These settings are of interest when debugging C@t{++} programs:
8006 @cindex demangling C@t{++} names
8007 @item set print demangle
8008 @itemx set print demangle on
8009 Print C@t{++} names in their source form rather than in the encoded
8010 (``mangled'') form passed to the assembler and linker for type-safe
8011 linkage. The default is on.
8013 @item show print demangle
8014 Show whether C@t{++} names are printed in mangled or demangled form.
8016 @item set print asm-demangle
8017 @itemx set print asm-demangle on
8018 Print C@t{++} names in their source form rather than their mangled form, even
8019 in assembler code printouts such as instruction disassemblies.
8022 @item show print asm-demangle
8023 Show whether C@t{++} names in assembly listings are printed in mangled
8026 @cindex C@t{++} symbol decoding style
8027 @cindex symbol decoding style, C@t{++}
8028 @kindex set demangle-style
8029 @item set demangle-style @var{style}
8030 Choose among several encoding schemes used by different compilers to
8031 represent C@t{++} names. The choices for @var{style} are currently:
8035 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8038 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8039 This is the default.
8042 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8045 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8048 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8049 @strong{Warning:} this setting alone is not sufficient to allow
8050 debugging @code{cfront}-generated executables. @value{GDBN} would
8051 require further enhancement to permit that.
8054 If you omit @var{style}, you will see a list of possible formats.
8056 @item show demangle-style
8057 Display the encoding style currently in use for decoding C@t{++} symbols.
8059 @item set print object
8060 @itemx set print object on
8061 @cindex derived type of an object, printing
8062 @cindex display derived types
8063 When displaying a pointer to an object, identify the @emph{actual}
8064 (derived) type of the object rather than the @emph{declared} type, using
8065 the virtual function table.
8067 @item set print object off
8068 Display only the declared type of objects, without reference to the
8069 virtual function table. This is the default setting.
8071 @item show print object
8072 Show whether actual, or declared, object types are displayed.
8074 @item set print static-members
8075 @itemx set print static-members on
8076 @cindex static members of C@t{++} objects
8077 Print static members when displaying a C@t{++} object. The default is on.
8079 @item set print static-members off
8080 Do not print static members when displaying a C@t{++} object.
8082 @item show print static-members
8083 Show whether C@t{++} static members are printed or not.
8085 @item set print pascal_static-members
8086 @itemx set print pascal_static-members on
8087 @cindex static members of Pascal objects
8088 @cindex Pascal objects, static members display
8089 Print static members when displaying a Pascal object. The default is on.
8091 @item set print pascal_static-members off
8092 Do not print static members when displaying a Pascal object.
8094 @item show print pascal_static-members
8095 Show whether Pascal static members are printed or not.
8097 @c These don't work with HP ANSI C++ yet.
8098 @item set print vtbl
8099 @itemx set print vtbl on
8100 @cindex pretty print C@t{++} virtual function tables
8101 @cindex virtual functions (C@t{++}) display
8102 @cindex VTBL display
8103 Pretty print C@t{++} virtual function tables. The default is off.
8104 (The @code{vtbl} commands do not work on programs compiled with the HP
8105 ANSI C@t{++} compiler (@code{aCC}).)
8107 @item set print vtbl off
8108 Do not pretty print C@t{++} virtual function tables.
8110 @item show print vtbl
8111 Show whether C@t{++} virtual function tables are pretty printed, or not.
8114 @node Pretty Printing
8115 @section Pretty Printing
8117 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8118 Python code. It greatly simplifies the display of complex objects. This
8119 mechanism works for both MI and the CLI.
8121 For example, here is how a C@t{++} @code{std::string} looks without a
8125 (@value{GDBP}) print s
8127 static npos = 4294967295,
8129 <std::allocator<char>> = @{
8130 <__gnu_cxx::new_allocator<char>> = @{
8131 <No data fields>@}, <No data fields>
8133 members of std::basic_string<char, std::char_traits<char>,
8134 std::allocator<char> >::_Alloc_hider:
8135 _M_p = 0x804a014 "abcd"
8140 With a pretty-printer for @code{std::string} only the contents are printed:
8143 (@value{GDBP}) print s
8147 For implementing pretty printers for new types you should read the Python API
8148 details (@pxref{Pretty Printing API}).
8151 @section Value History
8153 @cindex value history
8154 @cindex history of values printed by @value{GDBN}
8155 Values printed by the @code{print} command are saved in the @value{GDBN}
8156 @dfn{value history}. This allows you to refer to them in other expressions.
8157 Values are kept until the symbol table is re-read or discarded
8158 (for example with the @code{file} or @code{symbol-file} commands).
8159 When the symbol table changes, the value history is discarded,
8160 since the values may contain pointers back to the types defined in the
8165 @cindex history number
8166 The values printed are given @dfn{history numbers} by which you can
8167 refer to them. These are successive integers starting with one.
8168 @code{print} shows you the history number assigned to a value by
8169 printing @samp{$@var{num} = } before the value; here @var{num} is the
8172 To refer to any previous value, use @samp{$} followed by the value's
8173 history number. The way @code{print} labels its output is designed to
8174 remind you of this. Just @code{$} refers to the most recent value in
8175 the history, and @code{$$} refers to the value before that.
8176 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8177 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8178 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8180 For example, suppose you have just printed a pointer to a structure and
8181 want to see the contents of the structure. It suffices to type
8187 If you have a chain of structures where the component @code{next} points
8188 to the next one, you can print the contents of the next one with this:
8195 You can print successive links in the chain by repeating this
8196 command---which you can do by just typing @key{RET}.
8198 Note that the history records values, not expressions. If the value of
8199 @code{x} is 4 and you type these commands:
8207 then the value recorded in the value history by the @code{print} command
8208 remains 4 even though the value of @code{x} has changed.
8213 Print the last ten values in the value history, with their item numbers.
8214 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8215 values} does not change the history.
8217 @item show values @var{n}
8218 Print ten history values centered on history item number @var{n}.
8221 Print ten history values just after the values last printed. If no more
8222 values are available, @code{show values +} produces no display.
8225 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8226 same effect as @samp{show values +}.
8228 @node Convenience Vars
8229 @section Convenience Variables
8231 @cindex convenience variables
8232 @cindex user-defined variables
8233 @value{GDBN} provides @dfn{convenience variables} that you can use within
8234 @value{GDBN} to hold on to a value and refer to it later. These variables
8235 exist entirely within @value{GDBN}; they are not part of your program, and
8236 setting a convenience variable has no direct effect on further execution
8237 of your program. That is why you can use them freely.
8239 Convenience variables are prefixed with @samp{$}. Any name preceded by
8240 @samp{$} can be used for a convenience variable, unless it is one of
8241 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8242 (Value history references, in contrast, are @emph{numbers} preceded
8243 by @samp{$}. @xref{Value History, ,Value History}.)
8245 You can save a value in a convenience variable with an assignment
8246 expression, just as you would set a variable in your program.
8250 set $foo = *object_ptr
8254 would save in @code{$foo} the value contained in the object pointed to by
8257 Using a convenience variable for the first time creates it, but its
8258 value is @code{void} until you assign a new value. You can alter the
8259 value with another assignment at any time.
8261 Convenience variables have no fixed types. You can assign a convenience
8262 variable any type of value, including structures and arrays, even if
8263 that variable already has a value of a different type. The convenience
8264 variable, when used as an expression, has the type of its current value.
8267 @kindex show convenience
8268 @cindex show all user variables
8269 @item show convenience
8270 Print a list of convenience variables used so far, and their values.
8271 Abbreviated @code{show conv}.
8273 @kindex init-if-undefined
8274 @cindex convenience variables, initializing
8275 @item init-if-undefined $@var{variable} = @var{expression}
8276 Set a convenience variable if it has not already been set. This is useful
8277 for user-defined commands that keep some state. It is similar, in concept,
8278 to using local static variables with initializers in C (except that
8279 convenience variables are global). It can also be used to allow users to
8280 override default values used in a command script.
8282 If the variable is already defined then the expression is not evaluated so
8283 any side-effects do not occur.
8286 One of the ways to use a convenience variable is as a counter to be
8287 incremented or a pointer to be advanced. For example, to print
8288 a field from successive elements of an array of structures:
8292 print bar[$i++]->contents
8296 Repeat that command by typing @key{RET}.
8298 Some convenience variables are created automatically by @value{GDBN} and given
8299 values likely to be useful.
8302 @vindex $_@r{, convenience variable}
8304 The variable @code{$_} is automatically set by the @code{x} command to
8305 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8306 commands which provide a default address for @code{x} to examine also
8307 set @code{$_} to that address; these commands include @code{info line}
8308 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8309 except when set by the @code{x} command, in which case it is a pointer
8310 to the type of @code{$__}.
8312 @vindex $__@r{, convenience variable}
8314 The variable @code{$__} is automatically set by the @code{x} command
8315 to the value found in the last address examined. Its type is chosen
8316 to match the format in which the data was printed.
8319 @vindex $_exitcode@r{, convenience variable}
8320 The variable @code{$_exitcode} is automatically set to the exit code when
8321 the program being debugged terminates.
8324 @vindex $_sdata@r{, inspect, convenience variable}
8325 The variable @code{$_sdata} contains extra collected static tracepoint
8326 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8327 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8328 if extra static tracepoint data has not been collected.
8331 @vindex $_siginfo@r{, convenience variable}
8332 The variable @code{$_siginfo} contains extra signal information
8333 (@pxref{extra signal information}). Note that @code{$_siginfo}
8334 could be empty, if the application has not yet received any signals.
8335 For example, it will be empty before you execute the @code{run} command.
8338 @vindex $_tlb@r{, convenience variable}
8339 The variable @code{$_tlb} is automatically set when debugging
8340 applications running on MS-Windows in native mode or connected to
8341 gdbserver that supports the @code{qGetTIBAddr} request.
8342 @xref{General Query Packets}.
8343 This variable contains the address of the thread information block.
8347 On HP-UX systems, if you refer to a function or variable name that
8348 begins with a dollar sign, @value{GDBN} searches for a user or system
8349 name first, before it searches for a convenience variable.
8351 @cindex convenience functions
8352 @value{GDBN} also supplies some @dfn{convenience functions}. These
8353 have a syntax similar to convenience variables. A convenience
8354 function can be used in an expression just like an ordinary function;
8355 however, a convenience function is implemented internally to
8360 @kindex help function
8361 @cindex show all convenience functions
8362 Print a list of all convenience functions.
8369 You can refer to machine register contents, in expressions, as variables
8370 with names starting with @samp{$}. The names of registers are different
8371 for each machine; use @code{info registers} to see the names used on
8375 @kindex info registers
8376 @item info registers
8377 Print the names and values of all registers except floating-point
8378 and vector registers (in the selected stack frame).
8380 @kindex info all-registers
8381 @cindex floating point registers
8382 @item info all-registers
8383 Print the names and values of all registers, including floating-point
8384 and vector registers (in the selected stack frame).
8386 @item info registers @var{regname} @dots{}
8387 Print the @dfn{relativized} value of each specified register @var{regname}.
8388 As discussed in detail below, register values are normally relative to
8389 the selected stack frame. @var{regname} may be any register name valid on
8390 the machine you are using, with or without the initial @samp{$}.
8393 @cindex stack pointer register
8394 @cindex program counter register
8395 @cindex process status register
8396 @cindex frame pointer register
8397 @cindex standard registers
8398 @value{GDBN} has four ``standard'' register names that are available (in
8399 expressions) on most machines---whenever they do not conflict with an
8400 architecture's canonical mnemonics for registers. The register names
8401 @code{$pc} and @code{$sp} are used for the program counter register and
8402 the stack pointer. @code{$fp} is used for a register that contains a
8403 pointer to the current stack frame, and @code{$ps} is used for a
8404 register that contains the processor status. For example,
8405 you could print the program counter in hex with
8412 or print the instruction to be executed next with
8419 or add four to the stack pointer@footnote{This is a way of removing
8420 one word from the stack, on machines where stacks grow downward in
8421 memory (most machines, nowadays). This assumes that the innermost
8422 stack frame is selected; setting @code{$sp} is not allowed when other
8423 stack frames are selected. To pop entire frames off the stack,
8424 regardless of machine architecture, use @code{return};
8425 see @ref{Returning, ,Returning from a Function}.} with
8431 Whenever possible, these four standard register names are available on
8432 your machine even though the machine has different canonical mnemonics,
8433 so long as there is no conflict. The @code{info registers} command
8434 shows the canonical names. For example, on the SPARC, @code{info
8435 registers} displays the processor status register as @code{$psr} but you
8436 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8437 is an alias for the @sc{eflags} register.
8439 @value{GDBN} always considers the contents of an ordinary register as an
8440 integer when the register is examined in this way. Some machines have
8441 special registers which can hold nothing but floating point; these
8442 registers are considered to have floating point values. There is no way
8443 to refer to the contents of an ordinary register as floating point value
8444 (although you can @emph{print} it as a floating point value with
8445 @samp{print/f $@var{regname}}).
8447 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8448 means that the data format in which the register contents are saved by
8449 the operating system is not the same one that your program normally
8450 sees. For example, the registers of the 68881 floating point
8451 coprocessor are always saved in ``extended'' (raw) format, but all C
8452 programs expect to work with ``double'' (virtual) format. In such
8453 cases, @value{GDBN} normally works with the virtual format only (the format
8454 that makes sense for your program), but the @code{info registers} command
8455 prints the data in both formats.
8457 @cindex SSE registers (x86)
8458 @cindex MMX registers (x86)
8459 Some machines have special registers whose contents can be interpreted
8460 in several different ways. For example, modern x86-based machines
8461 have SSE and MMX registers that can hold several values packed
8462 together in several different formats. @value{GDBN} refers to such
8463 registers in @code{struct} notation:
8466 (@value{GDBP}) print $xmm1
8468 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8469 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8470 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8471 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8472 v4_int32 = @{0, 20657912, 11, 13@},
8473 v2_int64 = @{88725056443645952, 55834574859@},
8474 uint128 = 0x0000000d0000000b013b36f800000000
8479 To set values of such registers, you need to tell @value{GDBN} which
8480 view of the register you wish to change, as if you were assigning
8481 value to a @code{struct} member:
8484 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8487 Normally, register values are relative to the selected stack frame
8488 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8489 value that the register would contain if all stack frames farther in
8490 were exited and their saved registers restored. In order to see the
8491 true contents of hardware registers, you must select the innermost
8492 frame (with @samp{frame 0}).
8494 However, @value{GDBN} must deduce where registers are saved, from the machine
8495 code generated by your compiler. If some registers are not saved, or if
8496 @value{GDBN} is unable to locate the saved registers, the selected stack
8497 frame makes no difference.
8499 @node Floating Point Hardware
8500 @section Floating Point Hardware
8501 @cindex floating point
8503 Depending on the configuration, @value{GDBN} may be able to give
8504 you more information about the status of the floating point hardware.
8509 Display hardware-dependent information about the floating
8510 point unit. The exact contents and layout vary depending on the
8511 floating point chip. Currently, @samp{info float} is supported on
8512 the ARM and x86 machines.
8516 @section Vector Unit
8519 Depending on the configuration, @value{GDBN} may be able to give you
8520 more information about the status of the vector unit.
8525 Display information about the vector unit. The exact contents and
8526 layout vary depending on the hardware.
8529 @node OS Information
8530 @section Operating System Auxiliary Information
8531 @cindex OS information
8533 @value{GDBN} provides interfaces to useful OS facilities that can help
8534 you debug your program.
8536 @cindex @code{ptrace} system call
8537 @cindex @code{struct user} contents
8538 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8539 machines), it interfaces with the inferior via the @code{ptrace}
8540 system call. The operating system creates a special sata structure,
8541 called @code{struct user}, for this interface. You can use the
8542 command @code{info udot} to display the contents of this data
8548 Display the contents of the @code{struct user} maintained by the OS
8549 kernel for the program being debugged. @value{GDBN} displays the
8550 contents of @code{struct user} as a list of hex numbers, similar to
8551 the @code{examine} command.
8554 @cindex auxiliary vector
8555 @cindex vector, auxiliary
8556 Some operating systems supply an @dfn{auxiliary vector} to programs at
8557 startup. This is akin to the arguments and environment that you
8558 specify for a program, but contains a system-dependent variety of
8559 binary values that tell system libraries important details about the
8560 hardware, operating system, and process. Each value's purpose is
8561 identified by an integer tag; the meanings are well-known but system-specific.
8562 Depending on the configuration and operating system facilities,
8563 @value{GDBN} may be able to show you this information. For remote
8564 targets, this functionality may further depend on the remote stub's
8565 support of the @samp{qXfer:auxv:read} packet, see
8566 @ref{qXfer auxiliary vector read}.
8571 Display the auxiliary vector of the inferior, which can be either a
8572 live process or a core dump file. @value{GDBN} prints each tag value
8573 numerically, and also shows names and text descriptions for recognized
8574 tags. Some values in the vector are numbers, some bit masks, and some
8575 pointers to strings or other data. @value{GDBN} displays each value in the
8576 most appropriate form for a recognized tag, and in hexadecimal for
8577 an unrecognized tag.
8580 On some targets, @value{GDBN} can access operating-system-specific information
8581 and display it to user, without interpretation. For remote targets,
8582 this functionality depends on the remote stub's support of the
8583 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8588 List the types of OS information available for the target. If the
8589 target does not return a list of possible types, this command will
8592 @kindex info os processes
8593 @item info os processes
8594 Display the list of processes on the target. For each process,
8595 @value{GDBN} prints the process identifier, the name of the user, and
8596 the command corresponding to the process.
8599 @node Memory Region Attributes
8600 @section Memory Region Attributes
8601 @cindex memory region attributes
8603 @dfn{Memory region attributes} allow you to describe special handling
8604 required by regions of your target's memory. @value{GDBN} uses
8605 attributes to determine whether to allow certain types of memory
8606 accesses; whether to use specific width accesses; and whether to cache
8607 target memory. By default the description of memory regions is
8608 fetched from the target (if the current target supports this), but the
8609 user can override the fetched regions.
8611 Defined memory regions can be individually enabled and disabled. When a
8612 memory region is disabled, @value{GDBN} uses the default attributes when
8613 accessing memory in that region. Similarly, if no memory regions have
8614 been defined, @value{GDBN} uses the default attributes when accessing
8617 When a memory region is defined, it is given a number to identify it;
8618 to enable, disable, or remove a memory region, you specify that number.
8622 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8623 Define a memory region bounded by @var{lower} and @var{upper} with
8624 attributes @var{attributes}@dots{}, and add it to the list of regions
8625 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8626 case: it is treated as the target's maximum memory address.
8627 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8630 Discard any user changes to the memory regions and use target-supplied
8631 regions, if available, or no regions if the target does not support.
8634 @item delete mem @var{nums}@dots{}
8635 Remove memory regions @var{nums}@dots{} from the list of regions
8636 monitored by @value{GDBN}.
8639 @item disable mem @var{nums}@dots{}
8640 Disable monitoring of memory regions @var{nums}@dots{}.
8641 A disabled memory region is not forgotten.
8642 It may be enabled again later.
8645 @item enable mem @var{nums}@dots{}
8646 Enable monitoring of memory regions @var{nums}@dots{}.
8650 Print a table of all defined memory regions, with the following columns
8654 @item Memory Region Number
8655 @item Enabled or Disabled.
8656 Enabled memory regions are marked with @samp{y}.
8657 Disabled memory regions are marked with @samp{n}.
8660 The address defining the inclusive lower bound of the memory region.
8663 The address defining the exclusive upper bound of the memory region.
8666 The list of attributes set for this memory region.
8671 @subsection Attributes
8673 @subsubsection Memory Access Mode
8674 The access mode attributes set whether @value{GDBN} may make read or
8675 write accesses to a memory region.
8677 While these attributes prevent @value{GDBN} from performing invalid
8678 memory accesses, they do nothing to prevent the target system, I/O DMA,
8679 etc.@: from accessing memory.
8683 Memory is read only.
8685 Memory is write only.
8687 Memory is read/write. This is the default.
8690 @subsubsection Memory Access Size
8691 The access size attribute tells @value{GDBN} to use specific sized
8692 accesses in the memory region. Often memory mapped device registers
8693 require specific sized accesses. If no access size attribute is
8694 specified, @value{GDBN} may use accesses of any size.
8698 Use 8 bit memory accesses.
8700 Use 16 bit memory accesses.
8702 Use 32 bit memory accesses.
8704 Use 64 bit memory accesses.
8707 @c @subsubsection Hardware/Software Breakpoints
8708 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8709 @c will use hardware or software breakpoints for the internal breakpoints
8710 @c used by the step, next, finish, until, etc. commands.
8714 @c Always use hardware breakpoints
8715 @c @item swbreak (default)
8718 @subsubsection Data Cache
8719 The data cache attributes set whether @value{GDBN} will cache target
8720 memory. While this generally improves performance by reducing debug
8721 protocol overhead, it can lead to incorrect results because @value{GDBN}
8722 does not know about volatile variables or memory mapped device
8727 Enable @value{GDBN} to cache target memory.
8729 Disable @value{GDBN} from caching target memory. This is the default.
8732 @subsection Memory Access Checking
8733 @value{GDBN} can be instructed to refuse accesses to memory that is
8734 not explicitly described. This can be useful if accessing such
8735 regions has undesired effects for a specific target, or to provide
8736 better error checking. The following commands control this behaviour.
8739 @kindex set mem inaccessible-by-default
8740 @item set mem inaccessible-by-default [on|off]
8741 If @code{on} is specified, make @value{GDBN} treat memory not
8742 explicitly described by the memory ranges as non-existent and refuse accesses
8743 to such memory. The checks are only performed if there's at least one
8744 memory range defined. If @code{off} is specified, make @value{GDBN}
8745 treat the memory not explicitly described by the memory ranges as RAM.
8746 The default value is @code{on}.
8747 @kindex show mem inaccessible-by-default
8748 @item show mem inaccessible-by-default
8749 Show the current handling of accesses to unknown memory.
8753 @c @subsubsection Memory Write Verification
8754 @c The memory write verification attributes set whether @value{GDBN}
8755 @c will re-reads data after each write to verify the write was successful.
8759 @c @item noverify (default)
8762 @node Dump/Restore Files
8763 @section Copy Between Memory and a File
8764 @cindex dump/restore files
8765 @cindex append data to a file
8766 @cindex dump data to a file
8767 @cindex restore data from a file
8769 You can use the commands @code{dump}, @code{append}, and
8770 @code{restore} to copy data between target memory and a file. The
8771 @code{dump} and @code{append} commands write data to a file, and the
8772 @code{restore} command reads data from a file back into the inferior's
8773 memory. Files may be in binary, Motorola S-record, Intel hex, or
8774 Tektronix Hex format; however, @value{GDBN} can only append to binary
8780 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8781 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8782 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8783 or the value of @var{expr}, to @var{filename} in the given format.
8785 The @var{format} parameter may be any one of:
8792 Motorola S-record format.
8794 Tektronix Hex format.
8797 @value{GDBN} uses the same definitions of these formats as the
8798 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8799 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8803 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8804 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8805 Append the contents of memory from @var{start_addr} to @var{end_addr},
8806 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8807 (@value{GDBN} can only append data to files in raw binary form.)
8810 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8811 Restore the contents of file @var{filename} into memory. The
8812 @code{restore} command can automatically recognize any known @sc{bfd}
8813 file format, except for raw binary. To restore a raw binary file you
8814 must specify the optional keyword @code{binary} after the filename.
8816 If @var{bias} is non-zero, its value will be added to the addresses
8817 contained in the file. Binary files always start at address zero, so
8818 they will be restored at address @var{bias}. Other bfd files have
8819 a built-in location; they will be restored at offset @var{bias}
8822 If @var{start} and/or @var{end} are non-zero, then only data between
8823 file offset @var{start} and file offset @var{end} will be restored.
8824 These offsets are relative to the addresses in the file, before
8825 the @var{bias} argument is applied.
8829 @node Core File Generation
8830 @section How to Produce a Core File from Your Program
8831 @cindex dump core from inferior
8833 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8834 image of a running process and its process status (register values
8835 etc.). Its primary use is post-mortem debugging of a program that
8836 crashed while it ran outside a debugger. A program that crashes
8837 automatically produces a core file, unless this feature is disabled by
8838 the user. @xref{Files}, for information on invoking @value{GDBN} in
8839 the post-mortem debugging mode.
8841 Occasionally, you may wish to produce a core file of the program you
8842 are debugging in order to preserve a snapshot of its state.
8843 @value{GDBN} has a special command for that.
8847 @kindex generate-core-file
8848 @item generate-core-file [@var{file}]
8849 @itemx gcore [@var{file}]
8850 Produce a core dump of the inferior process. The optional argument
8851 @var{file} specifies the file name where to put the core dump. If not
8852 specified, the file name defaults to @file{core.@var{pid}}, where
8853 @var{pid} is the inferior process ID.
8855 Note that this command is implemented only for some systems (as of
8856 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8859 @node Character Sets
8860 @section Character Sets
8861 @cindex character sets
8863 @cindex translating between character sets
8864 @cindex host character set
8865 @cindex target character set
8867 If the program you are debugging uses a different character set to
8868 represent characters and strings than the one @value{GDBN} uses itself,
8869 @value{GDBN} can automatically translate between the character sets for
8870 you. The character set @value{GDBN} uses we call the @dfn{host
8871 character set}; the one the inferior program uses we call the
8872 @dfn{target character set}.
8874 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8875 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8876 remote protocol (@pxref{Remote Debugging}) to debug a program
8877 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8878 then the host character set is Latin-1, and the target character set is
8879 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8880 target-charset EBCDIC-US}, then @value{GDBN} translates between
8881 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8882 character and string literals in expressions.
8884 @value{GDBN} has no way to automatically recognize which character set
8885 the inferior program uses; you must tell it, using the @code{set
8886 target-charset} command, described below.
8888 Here are the commands for controlling @value{GDBN}'s character set
8892 @item set target-charset @var{charset}
8893 @kindex set target-charset
8894 Set the current target character set to @var{charset}. To display the
8895 list of supported target character sets, type
8896 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8898 @item set host-charset @var{charset}
8899 @kindex set host-charset
8900 Set the current host character set to @var{charset}.
8902 By default, @value{GDBN} uses a host character set appropriate to the
8903 system it is running on; you can override that default using the
8904 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8905 automatically determine the appropriate host character set. In this
8906 case, @value{GDBN} uses @samp{UTF-8}.
8908 @value{GDBN} can only use certain character sets as its host character
8909 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8910 @value{GDBN} will list the host character sets it supports.
8912 @item set charset @var{charset}
8914 Set the current host and target character sets to @var{charset}. As
8915 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8916 @value{GDBN} will list the names of the character sets that can be used
8917 for both host and target.
8920 @kindex show charset
8921 Show the names of the current host and target character sets.
8923 @item show host-charset
8924 @kindex show host-charset
8925 Show the name of the current host character set.
8927 @item show target-charset
8928 @kindex show target-charset
8929 Show the name of the current target character set.
8931 @item set target-wide-charset @var{charset}
8932 @kindex set target-wide-charset
8933 Set the current target's wide character set to @var{charset}. This is
8934 the character set used by the target's @code{wchar_t} type. To
8935 display the list of supported wide character sets, type
8936 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8938 @item show target-wide-charset
8939 @kindex show target-wide-charset
8940 Show the name of the current target's wide character set.
8943 Here is an example of @value{GDBN}'s character set support in action.
8944 Assume that the following source code has been placed in the file
8945 @file{charset-test.c}:
8951 = @{72, 101, 108, 108, 111, 44, 32, 119,
8952 111, 114, 108, 100, 33, 10, 0@};
8953 char ibm1047_hello[]
8954 = @{200, 133, 147, 147, 150, 107, 64, 166,
8955 150, 153, 147, 132, 90, 37, 0@};
8959 printf ("Hello, world!\n");
8963 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8964 containing the string @samp{Hello, world!} followed by a newline,
8965 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8967 We compile the program, and invoke the debugger on it:
8970 $ gcc -g charset-test.c -o charset-test
8971 $ gdb -nw charset-test
8972 GNU gdb 2001-12-19-cvs
8973 Copyright 2001 Free Software Foundation, Inc.
8978 We can use the @code{show charset} command to see what character sets
8979 @value{GDBN} is currently using to interpret and display characters and
8983 (@value{GDBP}) show charset
8984 The current host and target character set is `ISO-8859-1'.
8988 For the sake of printing this manual, let's use @sc{ascii} as our
8989 initial character set:
8991 (@value{GDBP}) set charset ASCII
8992 (@value{GDBP}) show charset
8993 The current host and target character set is `ASCII'.
8997 Let's assume that @sc{ascii} is indeed the correct character set for our
8998 host system --- in other words, let's assume that if @value{GDBN} prints
8999 characters using the @sc{ascii} character set, our terminal will display
9000 them properly. Since our current target character set is also
9001 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9004 (@value{GDBP}) print ascii_hello
9005 $1 = 0x401698 "Hello, world!\n"
9006 (@value{GDBP}) print ascii_hello[0]
9011 @value{GDBN} uses the target character set for character and string
9012 literals you use in expressions:
9015 (@value{GDBP}) print '+'
9020 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9023 @value{GDBN} relies on the user to tell it which character set the
9024 target program uses. If we print @code{ibm1047_hello} while our target
9025 character set is still @sc{ascii}, we get jibberish:
9028 (@value{GDBP}) print ibm1047_hello
9029 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9030 (@value{GDBP}) print ibm1047_hello[0]
9035 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9036 @value{GDBN} tells us the character sets it supports:
9039 (@value{GDBP}) set target-charset
9040 ASCII EBCDIC-US IBM1047 ISO-8859-1
9041 (@value{GDBP}) set target-charset
9044 We can select @sc{ibm1047} as our target character set, and examine the
9045 program's strings again. Now the @sc{ascii} string is wrong, but
9046 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9047 target character set, @sc{ibm1047}, to the host character set,
9048 @sc{ascii}, and they display correctly:
9051 (@value{GDBP}) set target-charset IBM1047
9052 (@value{GDBP}) show charset
9053 The current host character set is `ASCII'.
9054 The current target character set is `IBM1047'.
9055 (@value{GDBP}) print ascii_hello
9056 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9057 (@value{GDBP}) print ascii_hello[0]
9059 (@value{GDBP}) print ibm1047_hello
9060 $8 = 0x4016a8 "Hello, world!\n"
9061 (@value{GDBP}) print ibm1047_hello[0]
9066 As above, @value{GDBN} uses the target character set for character and
9067 string literals you use in expressions:
9070 (@value{GDBP}) print '+'
9075 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9078 @node Caching Remote Data
9079 @section Caching Data of Remote Targets
9080 @cindex caching data of remote targets
9082 @value{GDBN} caches data exchanged between the debugger and a
9083 remote target (@pxref{Remote Debugging}). Such caching generally improves
9084 performance, because it reduces the overhead of the remote protocol by
9085 bundling memory reads and writes into large chunks. Unfortunately, simply
9086 caching everything would lead to incorrect results, since @value{GDBN}
9087 does not necessarily know anything about volatile values, memory-mapped I/O
9088 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9089 memory can be changed @emph{while} a gdb command is executing.
9090 Therefore, by default, @value{GDBN} only caches data
9091 known to be on the stack@footnote{In non-stop mode, it is moderately
9092 rare for a running thread to modify the stack of a stopped thread
9093 in a way that would interfere with a backtrace, and caching of
9094 stack reads provides a significant speed up of remote backtraces.}.
9095 Other regions of memory can be explicitly marked as
9096 cacheable; see @pxref{Memory Region Attributes}.
9099 @kindex set remotecache
9100 @item set remotecache on
9101 @itemx set remotecache off
9102 This option no longer does anything; it exists for compatibility
9105 @kindex show remotecache
9106 @item show remotecache
9107 Show the current state of the obsolete remotecache flag.
9109 @kindex set stack-cache
9110 @item set stack-cache on
9111 @itemx set stack-cache off
9112 Enable or disable caching of stack accesses. When @code{ON}, use
9113 caching. By default, this option is @code{ON}.
9115 @kindex show stack-cache
9116 @item show stack-cache
9117 Show the current state of data caching for memory accesses.
9120 @item info dcache @r{[}line@r{]}
9121 Print the information about the data cache performance. The
9122 information displayed includes the dcache width and depth, and for
9123 each cache line, its number, address, and how many times it was
9124 referenced. This command is useful for debugging the data cache
9127 If a line number is specified, the contents of that line will be
9131 @node Searching Memory
9132 @section Search Memory
9133 @cindex searching memory
9135 Memory can be searched for a particular sequence of bytes with the
9136 @code{find} command.
9140 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9141 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9142 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9143 etc. The search begins at address @var{start_addr} and continues for either
9144 @var{len} bytes or through to @var{end_addr} inclusive.
9147 @var{s} and @var{n} are optional parameters.
9148 They may be specified in either order, apart or together.
9151 @item @var{s}, search query size
9152 The size of each search query value.
9158 halfwords (two bytes)
9162 giant words (eight bytes)
9165 All values are interpreted in the current language.
9166 This means, for example, that if the current source language is C/C@t{++}
9167 then searching for the string ``hello'' includes the trailing '\0'.
9169 If the value size is not specified, it is taken from the
9170 value's type in the current language.
9171 This is useful when one wants to specify the search
9172 pattern as a mixture of types.
9173 Note that this means, for example, that in the case of C-like languages
9174 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9175 which is typically four bytes.
9177 @item @var{n}, maximum number of finds
9178 The maximum number of matches to print. The default is to print all finds.
9181 You can use strings as search values. Quote them with double-quotes
9183 The string value is copied into the search pattern byte by byte,
9184 regardless of the endianness of the target and the size specification.
9186 The address of each match found is printed as well as a count of the
9187 number of matches found.
9189 The address of the last value found is stored in convenience variable
9191 A count of the number of matches is stored in @samp{$numfound}.
9193 For example, if stopped at the @code{printf} in this function:
9199 static char hello[] = "hello-hello";
9200 static struct @{ char c; short s; int i; @}
9201 __attribute__ ((packed)) mixed
9202 = @{ 'c', 0x1234, 0x87654321 @};
9203 printf ("%s\n", hello);
9208 you get during debugging:
9211 (gdb) find &hello[0], +sizeof(hello), "hello"
9212 0x804956d <hello.1620+6>
9214 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9215 0x8049567 <hello.1620>
9216 0x804956d <hello.1620+6>
9218 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9219 0x8049567 <hello.1620>
9221 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9222 0x8049560 <mixed.1625>
9224 (gdb) print $numfound
9227 $2 = (void *) 0x8049560
9230 @node Optimized Code
9231 @chapter Debugging Optimized Code
9232 @cindex optimized code, debugging
9233 @cindex debugging optimized code
9235 Almost all compilers support optimization. With optimization
9236 disabled, the compiler generates assembly code that corresponds
9237 directly to your source code, in a simplistic way. As the compiler
9238 applies more powerful optimizations, the generated assembly code
9239 diverges from your original source code. With help from debugging
9240 information generated by the compiler, @value{GDBN} can map from
9241 the running program back to constructs from your original source.
9243 @value{GDBN} is more accurate with optimization disabled. If you
9244 can recompile without optimization, it is easier to follow the
9245 progress of your program during debugging. But, there are many cases
9246 where you may need to debug an optimized version.
9248 When you debug a program compiled with @samp{-g -O}, remember that the
9249 optimizer has rearranged your code; the debugger shows you what is
9250 really there. Do not be too surprised when the execution path does not
9251 exactly match your source file! An extreme example: if you define a
9252 variable, but never use it, @value{GDBN} never sees that
9253 variable---because the compiler optimizes it out of existence.
9255 Some things do not work as well with @samp{-g -O} as with just
9256 @samp{-g}, particularly on machines with instruction scheduling. If in
9257 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9258 please report it to us as a bug (including a test case!).
9259 @xref{Variables}, for more information about debugging optimized code.
9262 * Inline Functions:: How @value{GDBN} presents inlining
9265 @node Inline Functions
9266 @section Inline Functions
9267 @cindex inline functions, debugging
9269 @dfn{Inlining} is an optimization that inserts a copy of the function
9270 body directly at each call site, instead of jumping to a shared
9271 routine. @value{GDBN} displays inlined functions just like
9272 non-inlined functions. They appear in backtraces. You can view their
9273 arguments and local variables, step into them with @code{step}, skip
9274 them with @code{next}, and escape from them with @code{finish}.
9275 You can check whether a function was inlined by using the
9276 @code{info frame} command.
9278 For @value{GDBN} to support inlined functions, the compiler must
9279 record information about inlining in the debug information ---
9280 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9281 other compilers do also. @value{GDBN} only supports inlined functions
9282 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9283 do not emit two required attributes (@samp{DW_AT_call_file} and
9284 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9285 function calls with earlier versions of @value{NGCC}. It instead
9286 displays the arguments and local variables of inlined functions as
9287 local variables in the caller.
9289 The body of an inlined function is directly included at its call site;
9290 unlike a non-inlined function, there are no instructions devoted to
9291 the call. @value{GDBN} still pretends that the call site and the
9292 start of the inlined function are different instructions. Stepping to
9293 the call site shows the call site, and then stepping again shows
9294 the first line of the inlined function, even though no additional
9295 instructions are executed.
9297 This makes source-level debugging much clearer; you can see both the
9298 context of the call and then the effect of the call. Only stepping by
9299 a single instruction using @code{stepi} or @code{nexti} does not do
9300 this; single instruction steps always show the inlined body.
9302 There are some ways that @value{GDBN} does not pretend that inlined
9303 function calls are the same as normal calls:
9307 You cannot set breakpoints on inlined functions. @value{GDBN}
9308 either reports that there is no symbol with that name, or else sets the
9309 breakpoint only on non-inlined copies of the function. This limitation
9310 will be removed in a future version of @value{GDBN}; until then,
9311 set a breakpoint by line number on the first line of the inlined
9315 Setting breakpoints at the call site of an inlined function may not
9316 work, because the call site does not contain any code. @value{GDBN}
9317 may incorrectly move the breakpoint to the next line of the enclosing
9318 function, after the call. This limitation will be removed in a future
9319 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9320 or inside the inlined function instead.
9323 @value{GDBN} cannot locate the return value of inlined calls after
9324 using the @code{finish} command. This is a limitation of compiler-generated
9325 debugging information; after @code{finish}, you can step to the next line
9326 and print a variable where your program stored the return value.
9332 @chapter C Preprocessor Macros
9334 Some languages, such as C and C@t{++}, provide a way to define and invoke
9335 ``preprocessor macros'' which expand into strings of tokens.
9336 @value{GDBN} can evaluate expressions containing macro invocations, show
9337 the result of macro expansion, and show a macro's definition, including
9338 where it was defined.
9340 You may need to compile your program specially to provide @value{GDBN}
9341 with information about preprocessor macros. Most compilers do not
9342 include macros in their debugging information, even when you compile
9343 with the @option{-g} flag. @xref{Compilation}.
9345 A program may define a macro at one point, remove that definition later,
9346 and then provide a different definition after that. Thus, at different
9347 points in the program, a macro may have different definitions, or have
9348 no definition at all. If there is a current stack frame, @value{GDBN}
9349 uses the macros in scope at that frame's source code line. Otherwise,
9350 @value{GDBN} uses the macros in scope at the current listing location;
9353 Whenever @value{GDBN} evaluates an expression, it always expands any
9354 macro invocations present in the expression. @value{GDBN} also provides
9355 the following commands for working with macros explicitly.
9359 @kindex macro expand
9360 @cindex macro expansion, showing the results of preprocessor
9361 @cindex preprocessor macro expansion, showing the results of
9362 @cindex expanding preprocessor macros
9363 @item macro expand @var{expression}
9364 @itemx macro exp @var{expression}
9365 Show the results of expanding all preprocessor macro invocations in
9366 @var{expression}. Since @value{GDBN} simply expands macros, but does
9367 not parse the result, @var{expression} need not be a valid expression;
9368 it can be any string of tokens.
9371 @item macro expand-once @var{expression}
9372 @itemx macro exp1 @var{expression}
9373 @cindex expand macro once
9374 @i{(This command is not yet implemented.)} Show the results of
9375 expanding those preprocessor macro invocations that appear explicitly in
9376 @var{expression}. Macro invocations appearing in that expansion are
9377 left unchanged. This command allows you to see the effect of a
9378 particular macro more clearly, without being confused by further
9379 expansions. Since @value{GDBN} simply expands macros, but does not
9380 parse the result, @var{expression} need not be a valid expression; it
9381 can be any string of tokens.
9384 @cindex macro definition, showing
9385 @cindex definition, showing a macro's
9386 @item info macro @var{macro}
9387 Show the definition of the macro named @var{macro}, and describe the
9388 source location or compiler command-line where that definition was established.
9390 @kindex macro define
9391 @cindex user-defined macros
9392 @cindex defining macros interactively
9393 @cindex macros, user-defined
9394 @item macro define @var{macro} @var{replacement-list}
9395 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9396 Introduce a definition for a preprocessor macro named @var{macro},
9397 invocations of which are replaced by the tokens given in
9398 @var{replacement-list}. The first form of this command defines an
9399 ``object-like'' macro, which takes no arguments; the second form
9400 defines a ``function-like'' macro, which takes the arguments given in
9403 A definition introduced by this command is in scope in every
9404 expression evaluated in @value{GDBN}, until it is removed with the
9405 @code{macro undef} command, described below. The definition overrides
9406 all definitions for @var{macro} present in the program being debugged,
9407 as well as any previous user-supplied definition.
9410 @item macro undef @var{macro}
9411 Remove any user-supplied definition for the macro named @var{macro}.
9412 This command only affects definitions provided with the @code{macro
9413 define} command, described above; it cannot remove definitions present
9414 in the program being debugged.
9418 List all the macros defined using the @code{macro define} command.
9421 @cindex macros, example of debugging with
9422 Here is a transcript showing the above commands in action. First, we
9423 show our source files:
9431 #define ADD(x) (M + x)
9436 printf ("Hello, world!\n");
9438 printf ("We're so creative.\n");
9440 printf ("Goodbye, world!\n");
9447 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9448 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9449 compiler includes information about preprocessor macros in the debugging
9453 $ gcc -gdwarf-2 -g3 sample.c -o sample
9457 Now, we start @value{GDBN} on our sample program:
9461 GNU gdb 2002-05-06-cvs
9462 Copyright 2002 Free Software Foundation, Inc.
9463 GDB is free software, @dots{}
9467 We can expand macros and examine their definitions, even when the
9468 program is not running. @value{GDBN} uses the current listing position
9469 to decide which macro definitions are in scope:
9472 (@value{GDBP}) list main
9475 5 #define ADD(x) (M + x)
9480 10 printf ("Hello, world!\n");
9482 12 printf ("We're so creative.\n");
9483 (@value{GDBP}) info macro ADD
9484 Defined at /home/jimb/gdb/macros/play/sample.c:5
9485 #define ADD(x) (M + x)
9486 (@value{GDBP}) info macro Q
9487 Defined at /home/jimb/gdb/macros/play/sample.h:1
9488 included at /home/jimb/gdb/macros/play/sample.c:2
9490 (@value{GDBP}) macro expand ADD(1)
9491 expands to: (42 + 1)
9492 (@value{GDBP}) macro expand-once ADD(1)
9493 expands to: once (M + 1)
9497 In the example above, note that @code{macro expand-once} expands only
9498 the macro invocation explicit in the original text --- the invocation of
9499 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9500 which was introduced by @code{ADD}.
9502 Once the program is running, @value{GDBN} uses the macro definitions in
9503 force at the source line of the current stack frame:
9506 (@value{GDBP}) break main
9507 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9509 Starting program: /home/jimb/gdb/macros/play/sample
9511 Breakpoint 1, main () at sample.c:10
9512 10 printf ("Hello, world!\n");
9516 At line 10, the definition of the macro @code{N} at line 9 is in force:
9519 (@value{GDBP}) info macro N
9520 Defined at /home/jimb/gdb/macros/play/sample.c:9
9522 (@value{GDBP}) macro expand N Q M
9524 (@value{GDBP}) print N Q M
9529 As we step over directives that remove @code{N}'s definition, and then
9530 give it a new definition, @value{GDBN} finds the definition (or lack
9531 thereof) in force at each point:
9536 12 printf ("We're so creative.\n");
9537 (@value{GDBP}) info macro N
9538 The symbol `N' has no definition as a C/C++ preprocessor macro
9539 at /home/jimb/gdb/macros/play/sample.c:12
9542 14 printf ("Goodbye, world!\n");
9543 (@value{GDBP}) info macro N
9544 Defined at /home/jimb/gdb/macros/play/sample.c:13
9546 (@value{GDBP}) macro expand N Q M
9547 expands to: 1729 < 42
9548 (@value{GDBP}) print N Q M
9553 In addition to source files, macros can be defined on the compilation command
9554 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9555 such a way, @value{GDBN} displays the location of their definition as line zero
9556 of the source file submitted to the compiler.
9559 (@value{GDBP}) info macro __STDC__
9560 Defined at /home/jimb/gdb/macros/play/sample.c:0
9567 @chapter Tracepoints
9568 @c This chapter is based on the documentation written by Michael
9569 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9572 In some applications, it is not feasible for the debugger to interrupt
9573 the program's execution long enough for the developer to learn
9574 anything helpful about its behavior. If the program's correctness
9575 depends on its real-time behavior, delays introduced by a debugger
9576 might cause the program to change its behavior drastically, or perhaps
9577 fail, even when the code itself is correct. It is useful to be able
9578 to observe the program's behavior without interrupting it.
9580 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9581 specify locations in the program, called @dfn{tracepoints}, and
9582 arbitrary expressions to evaluate when those tracepoints are reached.
9583 Later, using the @code{tfind} command, you can examine the values
9584 those expressions had when the program hit the tracepoints. The
9585 expressions may also denote objects in memory---structures or arrays,
9586 for example---whose values @value{GDBN} should record; while visiting
9587 a particular tracepoint, you may inspect those objects as if they were
9588 in memory at that moment. However, because @value{GDBN} records these
9589 values without interacting with you, it can do so quickly and
9590 unobtrusively, hopefully not disturbing the program's behavior.
9592 The tracepoint facility is currently available only for remote
9593 targets. @xref{Targets}. In addition, your remote target must know
9594 how to collect trace data. This functionality is implemented in the
9595 remote stub; however, none of the stubs distributed with @value{GDBN}
9596 support tracepoints as of this writing. The format of the remote
9597 packets used to implement tracepoints are described in @ref{Tracepoint
9600 It is also possible to get trace data from a file, in a manner reminiscent
9601 of corefiles; you specify the filename, and use @code{tfind} to search
9602 through the file. @xref{Trace Files}, for more details.
9604 This chapter describes the tracepoint commands and features.
9608 * Analyze Collected Data::
9609 * Tracepoint Variables::
9613 @node Set Tracepoints
9614 @section Commands to Set Tracepoints
9616 Before running such a @dfn{trace experiment}, an arbitrary number of
9617 tracepoints can be set. A tracepoint is actually a special type of
9618 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9619 standard breakpoint commands. For instance, as with breakpoints,
9620 tracepoint numbers are successive integers starting from one, and many
9621 of the commands associated with tracepoints take the tracepoint number
9622 as their argument, to identify which tracepoint to work on.
9624 For each tracepoint, you can specify, in advance, some arbitrary set
9625 of data that you want the target to collect in the trace buffer when
9626 it hits that tracepoint. The collected data can include registers,
9627 local variables, or global data. Later, you can use @value{GDBN}
9628 commands to examine the values these data had at the time the
9631 Tracepoints do not support every breakpoint feature. Ignore counts on
9632 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9633 commands when they are hit. Tracepoints may not be thread-specific
9636 @cindex fast tracepoints
9637 Some targets may support @dfn{fast tracepoints}, which are inserted in
9638 a different way (such as with a jump instead of a trap), that is
9639 faster but possibly restricted in where they may be installed.
9641 @cindex static tracepoints
9642 @cindex markers, static tracepoints
9643 @cindex probing markers, static tracepoints
9644 Regular and fast tracepoints are dynamic tracing facilities, meaning
9645 that they can be used to insert tracepoints at (almost) any location
9646 in the target. Some targets may also support controlling @dfn{static
9647 tracepoints} from @value{GDBN}. With static tracing, a set of
9648 instrumentation points, also known as @dfn{markers}, are embedded in
9649 the target program, and can be activated or deactivated by name or
9650 address. These are usually placed at locations which facilitate
9651 investigating what the target is actually doing. @value{GDBN}'s
9652 support for static tracing includes being able to list instrumentation
9653 points, and attach them with @value{GDBN} defined high level
9654 tracepoints that expose the whole range of convenience of
9655 @value{GDBN}'s tracepoints support. Namelly, support for collecting
9656 registers values and values of global or local (to the instrumentation
9657 point) variables; tracepoint conditions and trace state variables.
9658 The act of installing a @value{GDBN} static tracepoint on an
9659 instrumentation point, or marker, is referred to as @dfn{probing} a
9660 static tracepoint marker.
9662 @code{gdbserver} supports tracepoints on some target systems.
9663 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9665 This section describes commands to set tracepoints and associated
9666 conditions and actions.
9669 * Create and Delete Tracepoints::
9670 * Enable and Disable Tracepoints::
9671 * Tracepoint Passcounts::
9672 * Tracepoint Conditions::
9673 * Trace State Variables::
9674 * Tracepoint Actions::
9675 * Listing Tracepoints::
9676 * Listing Static Tracepoint Markers::
9677 * Starting and Stopping Trace Experiments::
9678 * Tracepoint Restrictions::
9681 @node Create and Delete Tracepoints
9682 @subsection Create and Delete Tracepoints
9685 @cindex set tracepoint
9687 @item trace @var{location}
9688 The @code{trace} command is very similar to the @code{break} command.
9689 Its argument @var{location} can be a source line, a function name, or
9690 an address in the target program. @xref{Specify Location}. The
9691 @code{trace} command defines a tracepoint, which is a point in the
9692 target program where the debugger will briefly stop, collect some
9693 data, and then allow the program to continue. Setting a tracepoint or
9694 changing its actions doesn't take effect until the next @code{tstart}
9695 command, and once a trace experiment is running, further changes will
9696 not have any effect until the next trace experiment starts.
9698 Here are some examples of using the @code{trace} command:
9701 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9703 (@value{GDBP}) @b{trace +2} // 2 lines forward
9705 (@value{GDBP}) @b{trace my_function} // first source line of function
9707 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9709 (@value{GDBP}) @b{trace *0x2117c4} // an address
9713 You can abbreviate @code{trace} as @code{tr}.
9715 @item trace @var{location} if @var{cond}
9716 Set a tracepoint with condition @var{cond}; evaluate the expression
9717 @var{cond} each time the tracepoint is reached, and collect data only
9718 if the value is nonzero---that is, if @var{cond} evaluates as true.
9719 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9720 information on tracepoint conditions.
9722 @item ftrace @var{location} [ if @var{cond} ]
9723 @cindex set fast tracepoint
9724 @cindex fast tracepoints, setting
9726 The @code{ftrace} command sets a fast tracepoint. For targets that
9727 support them, fast tracepoints will use a more efficient but possibly
9728 less general technique to trigger data collection, such as a jump
9729 instruction instead of a trap, or some sort of hardware support. It
9730 may not be possible to create a fast tracepoint at the desired
9731 location, in which case the command will exit with an explanatory
9734 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9737 @item strace @var{location} [ if @var{cond} ]
9738 @cindex set static tracepoint
9739 @cindex static tracepoints, setting
9740 @cindex probe static tracepoint marker
9742 The @code{strace} command sets a static tracepoint. For targets that
9743 support it, setting a static tracepoint probes a static
9744 instrumentation point, or marker, found at @var{location}. It may not
9745 be possible to set a static tracepoint at the desired location, in
9746 which case the command will exit with an explanatory message.
9748 @value{GDBN} handles arguments to @code{strace} exactly as for
9749 @code{trace}, with the addition that the user can also specify
9750 @code{-m @var{marker}} as @var{location}. This probes the marker
9751 identified by the @var{marker} string identifier. This identifier
9752 depends on the static tracepoint backend library your program is
9753 using. You can find all the marker identifiers in the @samp{ID} field
9754 of the @code{info static-tracepoint-markers} command output.
9755 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9756 Markers}. For example, in the following small program using the UST
9762 trace_mark(ust, bar33, "str %s", "FOOBAZ");
9767 the marker id is composed of joining the first two arguments to the
9768 @code{trace_mark} call with a slash, which translates to:
9771 (@value{GDBP}) info static-tracepoint-markers
9772 Cnt Enb ID Address What
9773 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
9779 so you may probe the marker above with:
9782 (@value{GDBP}) strace -m ust/bar33
9785 Static tracepoints accept an extra collect action --- @code{collect
9786 $_sdata}. This collects arbitrary user data passed in the probe point
9787 call to the tracing library. In the UST example above, you'll see
9788 that the third argument to @code{trace_mark} is a printf-like format
9789 string. The user data is then the result of running that formating
9790 string against the following arguments. Note that @code{info
9791 static-tracepoint-markers} command output lists that format string in
9792 the @samp{Data:} field.
9794 You can inspect this data when analyzing the trace buffer, by printing
9795 the $_sdata variable like any other variable available to
9796 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
9799 @cindex last tracepoint number
9800 @cindex recent tracepoint number
9801 @cindex tracepoint number
9802 The convenience variable @code{$tpnum} records the tracepoint number
9803 of the most recently set tracepoint.
9805 @kindex delete tracepoint
9806 @cindex tracepoint deletion
9807 @item delete tracepoint @r{[}@var{num}@r{]}
9808 Permanently delete one or more tracepoints. With no argument, the
9809 default is to delete all tracepoints. Note that the regular
9810 @code{delete} command can remove tracepoints also.
9815 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9817 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9821 You can abbreviate this command as @code{del tr}.
9824 @node Enable and Disable Tracepoints
9825 @subsection Enable and Disable Tracepoints
9827 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9830 @kindex disable tracepoint
9831 @item disable tracepoint @r{[}@var{num}@r{]}
9832 Disable tracepoint @var{num}, or all tracepoints if no argument
9833 @var{num} is given. A disabled tracepoint will have no effect during
9834 the next trace experiment, but it is not forgotten. You can re-enable
9835 a disabled tracepoint using the @code{enable tracepoint} command.
9837 @kindex enable tracepoint
9838 @item enable tracepoint @r{[}@var{num}@r{]}
9839 Enable tracepoint @var{num}, or all tracepoints. The enabled
9840 tracepoints will become effective the next time a trace experiment is
9844 @node Tracepoint Passcounts
9845 @subsection Tracepoint Passcounts
9849 @cindex tracepoint pass count
9850 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9851 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9852 automatically stop a trace experiment. If a tracepoint's passcount is
9853 @var{n}, then the trace experiment will be automatically stopped on
9854 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9855 @var{num} is not specified, the @code{passcount} command sets the
9856 passcount of the most recently defined tracepoint. If no passcount is
9857 given, the trace experiment will run until stopped explicitly by the
9863 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9864 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9866 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9867 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9868 (@value{GDBP}) @b{trace foo}
9869 (@value{GDBP}) @b{pass 3}
9870 (@value{GDBP}) @b{trace bar}
9871 (@value{GDBP}) @b{pass 2}
9872 (@value{GDBP}) @b{trace baz}
9873 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9874 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9875 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9876 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9880 @node Tracepoint Conditions
9881 @subsection Tracepoint Conditions
9882 @cindex conditional tracepoints
9883 @cindex tracepoint conditions
9885 The simplest sort of tracepoint collects data every time your program
9886 reaches a specified place. You can also specify a @dfn{condition} for
9887 a tracepoint. A condition is just a Boolean expression in your
9888 programming language (@pxref{Expressions, ,Expressions}). A
9889 tracepoint with a condition evaluates the expression each time your
9890 program reaches it, and data collection happens only if the condition
9893 Tracepoint conditions can be specified when a tracepoint is set, by
9894 using @samp{if} in the arguments to the @code{trace} command.
9895 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9896 also be set or changed at any time with the @code{condition} command,
9897 just as with breakpoints.
9899 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9900 the conditional expression itself. Instead, @value{GDBN} encodes the
9901 expression into an agent expression (@pxref{Agent Expressions}
9902 suitable for execution on the target, independently of @value{GDBN}.
9903 Global variables become raw memory locations, locals become stack
9904 accesses, and so forth.
9906 For instance, suppose you have a function that is usually called
9907 frequently, but should not be called after an error has occurred. You
9908 could use the following tracepoint command to collect data about calls
9909 of that function that happen while the error code is propagating
9910 through the program; an unconditional tracepoint could end up
9911 collecting thousands of useless trace frames that you would have to
9915 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9918 @node Trace State Variables
9919 @subsection Trace State Variables
9920 @cindex trace state variables
9922 A @dfn{trace state variable} is a special type of variable that is
9923 created and managed by target-side code. The syntax is the same as
9924 that for GDB's convenience variables (a string prefixed with ``$''),
9925 but they are stored on the target. They must be created explicitly,
9926 using a @code{tvariable} command. They are always 64-bit signed
9929 Trace state variables are remembered by @value{GDBN}, and downloaded
9930 to the target along with tracepoint information when the trace
9931 experiment starts. There are no intrinsic limits on the number of
9932 trace state variables, beyond memory limitations of the target.
9934 @cindex convenience variables, and trace state variables
9935 Although trace state variables are managed by the target, you can use
9936 them in print commands and expressions as if they were convenience
9937 variables; @value{GDBN} will get the current value from the target
9938 while the trace experiment is running. Trace state variables share
9939 the same namespace as other ``$'' variables, which means that you
9940 cannot have trace state variables with names like @code{$23} or
9941 @code{$pc}, nor can you have a trace state variable and a convenience
9942 variable with the same name.
9946 @item tvariable $@var{name} [ = @var{expression} ]
9948 The @code{tvariable} command creates a new trace state variable named
9949 @code{$@var{name}}, and optionally gives it an initial value of
9950 @var{expression}. @var{expression} is evaluated when this command is
9951 entered; the result will be converted to an integer if possible,
9952 otherwise @value{GDBN} will report an error. A subsequent
9953 @code{tvariable} command specifying the same name does not create a
9954 variable, but instead assigns the supplied initial value to the
9955 existing variable of that name, overwriting any previous initial
9956 value. The default initial value is 0.
9958 @item info tvariables
9959 @kindex info tvariables
9960 List all the trace state variables along with their initial values.
9961 Their current values may also be displayed, if the trace experiment is
9964 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
9965 @kindex delete tvariable
9966 Delete the given trace state variables, or all of them if no arguments
9971 @node Tracepoint Actions
9972 @subsection Tracepoint Action Lists
9976 @cindex tracepoint actions
9977 @item actions @r{[}@var{num}@r{]}
9978 This command will prompt for a list of actions to be taken when the
9979 tracepoint is hit. If the tracepoint number @var{num} is not
9980 specified, this command sets the actions for the one that was most
9981 recently defined (so that you can define a tracepoint and then say
9982 @code{actions} without bothering about its number). You specify the
9983 actions themselves on the following lines, one action at a time, and
9984 terminate the actions list with a line containing just @code{end}. So
9985 far, the only defined actions are @code{collect}, @code{teval}, and
9986 @code{while-stepping}.
9988 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
9989 Commands, ,Breakpoint Command Lists}), except that only the defined
9990 actions are allowed; any other @value{GDBN} command is rejected.
9992 @cindex remove actions from a tracepoint
9993 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9994 and follow it immediately with @samp{end}.
9997 (@value{GDBP}) @b{collect @var{data}} // collect some data
9999 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10001 (@value{GDBP}) @b{end} // signals the end of actions.
10004 In the following example, the action list begins with @code{collect}
10005 commands indicating the things to be collected when the tracepoint is
10006 hit. Then, in order to single-step and collect additional data
10007 following the tracepoint, a @code{while-stepping} command is used,
10008 followed by the list of things to be collected after each step in a
10009 sequence of single steps. The @code{while-stepping} command is
10010 terminated by its own separate @code{end} command. Lastly, the action
10011 list is terminated by an @code{end} command.
10014 (@value{GDBP}) @b{trace foo}
10015 (@value{GDBP}) @b{actions}
10016 Enter actions for tracepoint 1, one per line:
10019 > while-stepping 12
10020 > collect $pc, arr[i]
10025 @kindex collect @r{(tracepoints)}
10026 @item collect @var{expr1}, @var{expr2}, @dots{}
10027 Collect values of the given expressions when the tracepoint is hit.
10028 This command accepts a comma-separated list of any valid expressions.
10029 In addition to global, static, or local variables, the following
10030 special arguments are supported:
10034 Collect all registers.
10037 Collect all function arguments.
10040 Collect all local variables.
10043 @vindex $_sdata@r{, collect}
10044 Collect static tracepoint marker specific data. Only available for
10045 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10046 Lists}. On the UST static tracepoints library backend, an
10047 instrumentation point resembles a @code{printf} function call. The
10048 tracing library is able to collect user specified data formatted to a
10049 character string using the format provided by the programmer that
10050 instrumented the program. Other backends have similar mechanisms.
10051 Here's an example of a UST marker call:
10054 const char master_name[] = "$your_name";
10055 trace_mark(channel1, marker1, "hello %s", master_name)
10058 In this case, collecting @code{$_sdata} collects the string
10059 @samp{hello $yourname}. When analyzing the trace buffer, you can
10060 inspect @samp{$_sdata} like any other variable available to
10064 You can give several consecutive @code{collect} commands, each one
10065 with a single argument, or one @code{collect} command with several
10066 arguments separated by commas; the effect is the same.
10068 The command @code{info scope} (@pxref{Symbols, info scope}) is
10069 particularly useful for figuring out what data to collect.
10071 @kindex teval @r{(tracepoints)}
10072 @item teval @var{expr1}, @var{expr2}, @dots{}
10073 Evaluate the given expressions when the tracepoint is hit. This
10074 command accepts a comma-separated list of expressions. The results
10075 are discarded, so this is mainly useful for assigning values to trace
10076 state variables (@pxref{Trace State Variables}) without adding those
10077 values to the trace buffer, as would be the case if the @code{collect}
10080 @kindex while-stepping @r{(tracepoints)}
10081 @item while-stepping @var{n}
10082 Perform @var{n} single-step instruction traces after the tracepoint,
10083 collecting new data after each step. The @code{while-stepping}
10084 command is followed by the list of what to collect while stepping
10085 (followed by its own @code{end} command):
10088 > while-stepping 12
10089 > collect $regs, myglobal
10095 Note that @code{$pc} is not automatically collected by
10096 @code{while-stepping}; you need to explicitly collect that register if
10097 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10100 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10101 @kindex set default-collect
10102 @cindex default collection action
10103 This variable is a list of expressions to collect at each tracepoint
10104 hit. It is effectively an additional @code{collect} action prepended
10105 to every tracepoint action list. The expressions are parsed
10106 individually for each tracepoint, so for instance a variable named
10107 @code{xyz} may be interpreted as a global for one tracepoint, and a
10108 local for another, as appropriate to the tracepoint's location.
10110 @item show default-collect
10111 @kindex show default-collect
10112 Show the list of expressions that are collected by default at each
10117 @node Listing Tracepoints
10118 @subsection Listing Tracepoints
10121 @kindex info tracepoints
10123 @cindex information about tracepoints
10124 @item info tracepoints @r{[}@var{num}@r{]}
10125 Display information about the tracepoint @var{num}. If you don't
10126 specify a tracepoint number, displays information about all the
10127 tracepoints defined so far. The format is similar to that used for
10128 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10129 command, simply restricting itself to tracepoints.
10131 A tracepoint's listing may include additional information specific to
10136 its passcount as given by the @code{passcount @var{n}} command
10140 (@value{GDBP}) @b{info trace}
10141 Num Type Disp Enb Address What
10142 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10144 collect globfoo, $regs
10153 This command can be abbreviated @code{info tp}.
10156 @node Listing Static Tracepoint Markers
10157 @subsection Listing Static Tracepoint Markers
10160 @kindex info static-tracepoint-markers
10161 @cindex information about static tracepoint markers
10162 @item info static-tracepoint-markers
10163 Display information about all static tracepoint markers defined in the
10166 For each marker, the following columns are printed:
10170 An incrementing counter, output to help readability. This is not a
10173 The marker ID, as reported by the target.
10174 @item Enabled or Disabled
10175 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10176 that are not enabled.
10178 Where the marker is in your program, as a memory address.
10180 Where the marker is in the source for your program, as a file and line
10181 number. If the debug information included in the program does not
10182 allow @value{GDBN} to locate the source of the marker, this column
10183 will be left blank.
10187 In addition, the following information may be printed for each marker:
10191 User data passed to the tracing library by the marker call. In the
10192 UST backend, this is the format string passed as argument to the
10194 @item Static tracepoints probing the marker
10195 The list of static tracepoints attached to the marker.
10199 (@value{GDBP}) info static-tracepoint-markers
10200 Cnt ID Enb Address What
10201 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10202 Data: number1 %d number2 %d
10203 Probed by static tracepoints: #2
10204 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10210 @node Starting and Stopping Trace Experiments
10211 @subsection Starting and Stopping Trace Experiments
10215 @cindex start a new trace experiment
10216 @cindex collected data discarded
10218 This command takes no arguments. It starts the trace experiment, and
10219 begins collecting data. This has the side effect of discarding all
10220 the data collected in the trace buffer during the previous trace
10224 @cindex stop a running trace experiment
10226 This command takes no arguments. It ends the trace experiment, and
10227 stops collecting data.
10229 @strong{Note}: a trace experiment and data collection may stop
10230 automatically if any tracepoint's passcount is reached
10231 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10234 @cindex status of trace data collection
10235 @cindex trace experiment, status of
10237 This command displays the status of the current trace data
10241 Here is an example of the commands we described so far:
10244 (@value{GDBP}) @b{trace gdb_c_test}
10245 (@value{GDBP}) @b{actions}
10246 Enter actions for tracepoint #1, one per line.
10247 > collect $regs,$locals,$args
10248 > while-stepping 11
10252 (@value{GDBP}) @b{tstart}
10253 [time passes @dots{}]
10254 (@value{GDBP}) @b{tstop}
10257 @cindex disconnected tracing
10258 You can choose to continue running the trace experiment even if
10259 @value{GDBN} disconnects from the target, voluntarily or
10260 involuntarily. For commands such as @code{detach}, the debugger will
10261 ask what you want to do with the trace. But for unexpected
10262 terminations (@value{GDBN} crash, network outage), it would be
10263 unfortunate to lose hard-won trace data, so the variable
10264 @code{disconnected-tracing} lets you decide whether the trace should
10265 continue running without @value{GDBN}.
10268 @item set disconnected-tracing on
10269 @itemx set disconnected-tracing off
10270 @kindex set disconnected-tracing
10271 Choose whether a tracing run should continue to run if @value{GDBN}
10272 has disconnected from the target. Note that @code{detach} or
10273 @code{quit} will ask you directly what to do about a running trace no
10274 matter what this variable's setting, so the variable is mainly useful
10275 for handling unexpected situations, such as loss of the network.
10277 @item show disconnected-tracing
10278 @kindex show disconnected-tracing
10279 Show the current choice for disconnected tracing.
10283 When you reconnect to the target, the trace experiment may or may not
10284 still be running; it might have filled the trace buffer in the
10285 meantime, or stopped for one of the other reasons. If it is running,
10286 it will continue after reconnection.
10288 Upon reconnection, the target will upload information about the
10289 tracepoints in effect. @value{GDBN} will then compare that
10290 information to the set of tracepoints currently defined, and attempt
10291 to match them up, allowing for the possibility that the numbers may
10292 have changed due to creation and deletion in the meantime. If one of
10293 the target's tracepoints does not match any in @value{GDBN}, the
10294 debugger will create a new tracepoint, so that you have a number with
10295 which to specify that tracepoint. This matching-up process is
10296 necessarily heuristic, and it may result in useless tracepoints being
10297 created; you may simply delete them if they are of no use.
10299 @cindex circular trace buffer
10300 If your target agent supports a @dfn{circular trace buffer}, then you
10301 can run a trace experiment indefinitely without filling the trace
10302 buffer; when space runs out, the agent deletes already-collected trace
10303 frames, oldest first, until there is enough room to continue
10304 collecting. This is especially useful if your tracepoints are being
10305 hit too often, and your trace gets terminated prematurely because the
10306 buffer is full. To ask for a circular trace buffer, simply set
10307 @samp{circular_trace_buffer} to on. You can set this at any time,
10308 including during tracing; if the agent can do it, it will change
10309 buffer handling on the fly, otherwise it will not take effect until
10313 @item set circular-trace-buffer on
10314 @itemx set circular-trace-buffer off
10315 @kindex set circular-trace-buffer
10316 Choose whether a tracing run should use a linear or circular buffer
10317 for trace data. A linear buffer will not lose any trace data, but may
10318 fill up prematurely, while a circular buffer will discard old trace
10319 data, but it will have always room for the latest tracepoint hits.
10321 @item show circular-trace-buffer
10322 @kindex show circular-trace-buffer
10323 Show the current choice for the trace buffer. Note that this may not
10324 match the agent's current buffer handling, nor is it guaranteed to
10325 match the setting that might have been in effect during a past run,
10326 for instance if you are looking at frames from a trace file.
10330 @node Tracepoint Restrictions
10331 @subsection Tracepoint Restrictions
10333 @cindex tracepoint restrictions
10334 There are a number of restrictions on the use of tracepoints. As
10335 described above, tracepoint data gathering occurs on the target
10336 without interaction from @value{GDBN}. Thus the full capabilities of
10337 the debugger are not available during data gathering, and then at data
10338 examination time, you will be limited by only having what was
10339 collected. The following items describe some common problems, but it
10340 is not exhaustive, and you may run into additional difficulties not
10346 Tracepoint expressions are intended to gather objects (lvalues). Thus
10347 the full flexibility of GDB's expression evaluator is not available.
10348 You cannot call functions, cast objects to aggregate types, access
10349 convenience variables or modify values (except by assignment to trace
10350 state variables). Some language features may implicitly call
10351 functions (for instance Objective-C fields with accessors), and therefore
10352 cannot be collected either.
10355 Collection of local variables, either individually or in bulk with
10356 @code{$locals} or @code{$args}, during @code{while-stepping} may
10357 behave erratically. The stepping action may enter a new scope (for
10358 instance by stepping into a function), or the location of the variable
10359 may change (for instance it is loaded into a register). The
10360 tracepoint data recorded uses the location information for the
10361 variables that is correct for the tracepoint location. When the
10362 tracepoint is created, it is not possible, in general, to determine
10363 where the steps of a @code{while-stepping} sequence will advance the
10364 program---particularly if a conditional branch is stepped.
10367 Collection of an incompletely-initialized or partially-destroyed object
10368 may result in something that @value{GDBN} cannot display, or displays
10369 in a misleading way.
10372 When @value{GDBN} displays a pointer to character it automatically
10373 dereferences the pointer to also display characters of the string
10374 being pointed to. However, collecting the pointer during tracing does
10375 not automatically collect the string. You need to explicitly
10376 dereference the pointer and provide size information if you want to
10377 collect not only the pointer, but the memory pointed to. For example,
10378 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10382 It is not possible to collect a complete stack backtrace at a
10383 tracepoint. Instead, you may collect the registers and a few hundred
10384 bytes from the stack pointer with something like @code{*$esp@@300}
10385 (adjust to use the name of the actual stack pointer register on your
10386 target architecture, and the amount of stack you wish to capture).
10387 Then the @code{backtrace} command will show a partial backtrace when
10388 using a trace frame. The number of stack frames that can be examined
10389 depends on the sizes of the frames in the collected stack. Note that
10390 if you ask for a block so large that it goes past the bottom of the
10391 stack, the target agent may report an error trying to read from an
10395 If you do not collect registers at a tracepoint, @value{GDBN} can
10396 infer that the value of @code{$pc} must be the same as the address of
10397 the tracepoint and use that when you are looking at a trace frame
10398 for that tracepoint. However, this cannot work if the tracepoint has
10399 multiple locations (for instance if it was set in a function that was
10400 inlined), or if it has a @code{while-stepping} loop. In those cases
10401 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10406 @node Analyze Collected Data
10407 @section Using the Collected Data
10409 After the tracepoint experiment ends, you use @value{GDBN} commands
10410 for examining the trace data. The basic idea is that each tracepoint
10411 collects a trace @dfn{snapshot} every time it is hit and another
10412 snapshot every time it single-steps. All these snapshots are
10413 consecutively numbered from zero and go into a buffer, and you can
10414 examine them later. The way you examine them is to @dfn{focus} on a
10415 specific trace snapshot. When the remote stub is focused on a trace
10416 snapshot, it will respond to all @value{GDBN} requests for memory and
10417 registers by reading from the buffer which belongs to that snapshot,
10418 rather than from @emph{real} memory or registers of the program being
10419 debugged. This means that @strong{all} @value{GDBN} commands
10420 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10421 behave as if we were currently debugging the program state as it was
10422 when the tracepoint occurred. Any requests for data that are not in
10423 the buffer will fail.
10426 * tfind:: How to select a trace snapshot
10427 * tdump:: How to display all data for a snapshot
10428 * save tracepoints:: How to save tracepoints for a future run
10432 @subsection @code{tfind @var{n}}
10435 @cindex select trace snapshot
10436 @cindex find trace snapshot
10437 The basic command for selecting a trace snapshot from the buffer is
10438 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10439 counting from zero. If no argument @var{n} is given, the next
10440 snapshot is selected.
10442 Here are the various forms of using the @code{tfind} command.
10446 Find the first snapshot in the buffer. This is a synonym for
10447 @code{tfind 0} (since 0 is the number of the first snapshot).
10450 Stop debugging trace snapshots, resume @emph{live} debugging.
10453 Same as @samp{tfind none}.
10456 No argument means find the next trace snapshot.
10459 Find the previous trace snapshot before the current one. This permits
10460 retracing earlier steps.
10462 @item tfind tracepoint @var{num}
10463 Find the next snapshot associated with tracepoint @var{num}. Search
10464 proceeds forward from the last examined trace snapshot. If no
10465 argument @var{num} is given, it means find the next snapshot collected
10466 for the same tracepoint as the current snapshot.
10468 @item tfind pc @var{addr}
10469 Find the next snapshot associated with the value @var{addr} of the
10470 program counter. Search proceeds forward from the last examined trace
10471 snapshot. If no argument @var{addr} is given, it means find the next
10472 snapshot with the same value of PC as the current snapshot.
10474 @item tfind outside @var{addr1}, @var{addr2}
10475 Find the next snapshot whose PC is outside the given range of
10476 addresses (exclusive).
10478 @item tfind range @var{addr1}, @var{addr2}
10479 Find the next snapshot whose PC is between @var{addr1} and
10480 @var{addr2} (inclusive).
10482 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10483 Find the next snapshot associated with the source line @var{n}. If
10484 the optional argument @var{file} is given, refer to line @var{n} in
10485 that source file. Search proceeds forward from the last examined
10486 trace snapshot. If no argument @var{n} is given, it means find the
10487 next line other than the one currently being examined; thus saying
10488 @code{tfind line} repeatedly can appear to have the same effect as
10489 stepping from line to line in a @emph{live} debugging session.
10492 The default arguments for the @code{tfind} commands are specifically
10493 designed to make it easy to scan through the trace buffer. For
10494 instance, @code{tfind} with no argument selects the next trace
10495 snapshot, and @code{tfind -} with no argument selects the previous
10496 trace snapshot. So, by giving one @code{tfind} command, and then
10497 simply hitting @key{RET} repeatedly you can examine all the trace
10498 snapshots in order. Or, by saying @code{tfind -} and then hitting
10499 @key{RET} repeatedly you can examine the snapshots in reverse order.
10500 The @code{tfind line} command with no argument selects the snapshot
10501 for the next source line executed. The @code{tfind pc} command with
10502 no argument selects the next snapshot with the same program counter
10503 (PC) as the current frame. The @code{tfind tracepoint} command with
10504 no argument selects the next trace snapshot collected by the same
10505 tracepoint as the current one.
10507 In addition to letting you scan through the trace buffer manually,
10508 these commands make it easy to construct @value{GDBN} scripts that
10509 scan through the trace buffer and print out whatever collected data
10510 you are interested in. Thus, if we want to examine the PC, FP, and SP
10511 registers from each trace frame in the buffer, we can say this:
10514 (@value{GDBP}) @b{tfind start}
10515 (@value{GDBP}) @b{while ($trace_frame != -1)}
10516 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10517 $trace_frame, $pc, $sp, $fp
10521 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10522 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10523 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10524 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10525 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10526 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10527 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10528 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10529 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10530 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10531 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10534 Or, if we want to examine the variable @code{X} at each source line in
10538 (@value{GDBP}) @b{tfind start}
10539 (@value{GDBP}) @b{while ($trace_frame != -1)}
10540 > printf "Frame %d, X == %d\n", $trace_frame, X
10550 @subsection @code{tdump}
10552 @cindex dump all data collected at tracepoint
10553 @cindex tracepoint data, display
10555 This command takes no arguments. It prints all the data collected at
10556 the current trace snapshot.
10559 (@value{GDBP}) @b{trace 444}
10560 (@value{GDBP}) @b{actions}
10561 Enter actions for tracepoint #2, one per line:
10562 > collect $regs, $locals, $args, gdb_long_test
10565 (@value{GDBP}) @b{tstart}
10567 (@value{GDBP}) @b{tfind line 444}
10568 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10570 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10572 (@value{GDBP}) @b{tdump}
10573 Data collected at tracepoint 2, trace frame 1:
10574 d0 0xc4aa0085 -995491707
10578 d4 0x71aea3d 119204413
10581 d7 0x380035 3670069
10582 a0 0x19e24a 1696330
10583 a1 0x3000668 50333288
10585 a3 0x322000 3284992
10586 a4 0x3000698 50333336
10587 a5 0x1ad3cc 1758156
10588 fp 0x30bf3c 0x30bf3c
10589 sp 0x30bf34 0x30bf34
10591 pc 0x20b2c8 0x20b2c8
10595 p = 0x20e5b4 "gdb-test"
10602 gdb_long_test = 17 '\021'
10607 @code{tdump} works by scanning the tracepoint's current collection
10608 actions and printing the value of each expression listed. So
10609 @code{tdump} can fail, if after a run, you change the tracepoint's
10610 actions to mention variables that were not collected during the run.
10612 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10613 uses the collected value of @code{$pc} to distinguish between trace
10614 frames that were collected at the tracepoint hit, and frames that were
10615 collected while stepping. This allows it to correctly choose whether
10616 to display the basic list of collections, or the collections from the
10617 body of the while-stepping loop. However, if @code{$pc} was not collected,
10618 then @code{tdump} will always attempt to dump using the basic collection
10619 list, and may fail if a while-stepping frame does not include all the
10620 same data that is collected at the tracepoint hit.
10621 @c This is getting pretty arcane, example would be good.
10623 @node save tracepoints
10624 @subsection @code{save tracepoints @var{filename}}
10625 @kindex save tracepoints
10626 @kindex save-tracepoints
10627 @cindex save tracepoints for future sessions
10629 This command saves all current tracepoint definitions together with
10630 their actions and passcounts, into a file @file{@var{filename}}
10631 suitable for use in a later debugging session. To read the saved
10632 tracepoint definitions, use the @code{source} command (@pxref{Command
10633 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10634 alias for @w{@code{save tracepoints}}
10636 @node Tracepoint Variables
10637 @section Convenience Variables for Tracepoints
10638 @cindex tracepoint variables
10639 @cindex convenience variables for tracepoints
10642 @vindex $trace_frame
10643 @item (int) $trace_frame
10644 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10645 snapshot is selected.
10647 @vindex $tracepoint
10648 @item (int) $tracepoint
10649 The tracepoint for the current trace snapshot.
10651 @vindex $trace_line
10652 @item (int) $trace_line
10653 The line number for the current trace snapshot.
10655 @vindex $trace_file
10656 @item (char []) $trace_file
10657 The source file for the current trace snapshot.
10659 @vindex $trace_func
10660 @item (char []) $trace_func
10661 The name of the function containing @code{$tracepoint}.
10664 Note: @code{$trace_file} is not suitable for use in @code{printf},
10665 use @code{output} instead.
10667 Here's a simple example of using these convenience variables for
10668 stepping through all the trace snapshots and printing some of their
10669 data. Note that these are not the same as trace state variables,
10670 which are managed by the target.
10673 (@value{GDBP}) @b{tfind start}
10675 (@value{GDBP}) @b{while $trace_frame != -1}
10676 > output $trace_file
10677 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10683 @section Using Trace Files
10684 @cindex trace files
10686 In some situations, the target running a trace experiment may no
10687 longer be available; perhaps it crashed, or the hardware was needed
10688 for a different activity. To handle these cases, you can arrange to
10689 dump the trace data into a file, and later use that file as a source
10690 of trace data, via the @code{target tfile} command.
10695 @item tsave [ -r ] @var{filename}
10696 Save the trace data to @var{filename}. By default, this command
10697 assumes that @var{filename} refers to the host filesystem, so if
10698 necessary @value{GDBN} will copy raw trace data up from the target and
10699 then save it. If the target supports it, you can also supply the
10700 optional argument @code{-r} (``remote'') to direct the target to save
10701 the data directly into @var{filename} in its own filesystem, which may be
10702 more efficient if the trace buffer is very large. (Note, however, that
10703 @code{target tfile} can only read from files accessible to the host.)
10705 @kindex target tfile
10707 @item target tfile @var{filename}
10708 Use the file named @var{filename} as a source of trace data. Commands
10709 that examine data work as they do with a live target, but it is not
10710 possible to run any new trace experiments. @code{tstatus} will report
10711 the state of the trace run at the moment the data was saved, as well
10712 as the current trace frame you are examining. @var{filename} must be
10713 on a filesystem accessible to the host.
10718 @chapter Debugging Programs That Use Overlays
10721 If your program is too large to fit completely in your target system's
10722 memory, you can sometimes use @dfn{overlays} to work around this
10723 problem. @value{GDBN} provides some support for debugging programs that
10727 * How Overlays Work:: A general explanation of overlays.
10728 * Overlay Commands:: Managing overlays in @value{GDBN}.
10729 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10730 mapped by asking the inferior.
10731 * Overlay Sample Program:: A sample program using overlays.
10734 @node How Overlays Work
10735 @section How Overlays Work
10736 @cindex mapped overlays
10737 @cindex unmapped overlays
10738 @cindex load address, overlay's
10739 @cindex mapped address
10740 @cindex overlay area
10742 Suppose you have a computer whose instruction address space is only 64
10743 kilobytes long, but which has much more memory which can be accessed by
10744 other means: special instructions, segment registers, or memory
10745 management hardware, for example. Suppose further that you want to
10746 adapt a program which is larger than 64 kilobytes to run on this system.
10748 One solution is to identify modules of your program which are relatively
10749 independent, and need not call each other directly; call these modules
10750 @dfn{overlays}. Separate the overlays from the main program, and place
10751 their machine code in the larger memory. Place your main program in
10752 instruction memory, but leave at least enough space there to hold the
10753 largest overlay as well.
10755 Now, to call a function located in an overlay, you must first copy that
10756 overlay's machine code from the large memory into the space set aside
10757 for it in the instruction memory, and then jump to its entry point
10760 @c NB: In the below the mapped area's size is greater or equal to the
10761 @c size of all overlays. This is intentional to remind the developer
10762 @c that overlays don't necessarily need to be the same size.
10766 Data Instruction Larger
10767 Address Space Address Space Address Space
10768 +-----------+ +-----------+ +-----------+
10770 +-----------+ +-----------+ +-----------+<-- overlay 1
10771 | program | | main | .----| overlay 1 | load address
10772 | variables | | program | | +-----------+
10773 | and heap | | | | | |
10774 +-----------+ | | | +-----------+<-- overlay 2
10775 | | +-----------+ | | | load address
10776 +-----------+ | | | .-| overlay 2 |
10778 mapped --->+-----------+ | | +-----------+
10779 address | | | | | |
10780 | overlay | <-' | | |
10781 | area | <---' +-----------+<-- overlay 3
10782 | | <---. | | load address
10783 +-----------+ `--| overlay 3 |
10790 @anchor{A code overlay}A code overlay
10794 The diagram (@pxref{A code overlay}) shows a system with separate data
10795 and instruction address spaces. To map an overlay, the program copies
10796 its code from the larger address space to the instruction address space.
10797 Since the overlays shown here all use the same mapped address, only one
10798 may be mapped at a time. For a system with a single address space for
10799 data and instructions, the diagram would be similar, except that the
10800 program variables and heap would share an address space with the main
10801 program and the overlay area.
10803 An overlay loaded into instruction memory and ready for use is called a
10804 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10805 instruction memory. An overlay not present (or only partially present)
10806 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10807 is its address in the larger memory. The mapped address is also called
10808 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10809 called the @dfn{load memory address}, or @dfn{LMA}.
10811 Unfortunately, overlays are not a completely transparent way to adapt a
10812 program to limited instruction memory. They introduce a new set of
10813 global constraints you must keep in mind as you design your program:
10818 Before calling or returning to a function in an overlay, your program
10819 must make sure that overlay is actually mapped. Otherwise, the call or
10820 return will transfer control to the right address, but in the wrong
10821 overlay, and your program will probably crash.
10824 If the process of mapping an overlay is expensive on your system, you
10825 will need to choose your overlays carefully to minimize their effect on
10826 your program's performance.
10829 The executable file you load onto your system must contain each
10830 overlay's instructions, appearing at the overlay's load address, not its
10831 mapped address. However, each overlay's instructions must be relocated
10832 and its symbols defined as if the overlay were at its mapped address.
10833 You can use GNU linker scripts to specify different load and relocation
10834 addresses for pieces of your program; see @ref{Overlay Description,,,
10835 ld.info, Using ld: the GNU linker}.
10838 The procedure for loading executable files onto your system must be able
10839 to load their contents into the larger address space as well as the
10840 instruction and data spaces.
10844 The overlay system described above is rather simple, and could be
10845 improved in many ways:
10850 If your system has suitable bank switch registers or memory management
10851 hardware, you could use those facilities to make an overlay's load area
10852 contents simply appear at their mapped address in instruction space.
10853 This would probably be faster than copying the overlay to its mapped
10854 area in the usual way.
10857 If your overlays are small enough, you could set aside more than one
10858 overlay area, and have more than one overlay mapped at a time.
10861 You can use overlays to manage data, as well as instructions. In
10862 general, data overlays are even less transparent to your design than
10863 code overlays: whereas code overlays only require care when you call or
10864 return to functions, data overlays require care every time you access
10865 the data. Also, if you change the contents of a data overlay, you
10866 must copy its contents back out to its load address before you can copy a
10867 different data overlay into the same mapped area.
10872 @node Overlay Commands
10873 @section Overlay Commands
10875 To use @value{GDBN}'s overlay support, each overlay in your program must
10876 correspond to a separate section of the executable file. The section's
10877 virtual memory address and load memory address must be the overlay's
10878 mapped and load addresses. Identifying overlays with sections allows
10879 @value{GDBN} to determine the appropriate address of a function or
10880 variable, depending on whether the overlay is mapped or not.
10882 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10883 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10888 Disable @value{GDBN}'s overlay support. When overlay support is
10889 disabled, @value{GDBN} assumes that all functions and variables are
10890 always present at their mapped addresses. By default, @value{GDBN}'s
10891 overlay support is disabled.
10893 @item overlay manual
10894 @cindex manual overlay debugging
10895 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10896 relies on you to tell it which overlays are mapped, and which are not,
10897 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10898 commands described below.
10900 @item overlay map-overlay @var{overlay}
10901 @itemx overlay map @var{overlay}
10902 @cindex map an overlay
10903 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10904 be the name of the object file section containing the overlay. When an
10905 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10906 functions and variables at their mapped addresses. @value{GDBN} assumes
10907 that any other overlays whose mapped ranges overlap that of
10908 @var{overlay} are now unmapped.
10910 @item overlay unmap-overlay @var{overlay}
10911 @itemx overlay unmap @var{overlay}
10912 @cindex unmap an overlay
10913 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10914 must be the name of the object file section containing the overlay.
10915 When an overlay is unmapped, @value{GDBN} assumes it can find the
10916 overlay's functions and variables at their load addresses.
10919 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10920 consults a data structure the overlay manager maintains in the inferior
10921 to see which overlays are mapped. For details, see @ref{Automatic
10922 Overlay Debugging}.
10924 @item overlay load-target
10925 @itemx overlay load
10926 @cindex reloading the overlay table
10927 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10928 re-reads the table @value{GDBN} automatically each time the inferior
10929 stops, so this command should only be necessary if you have changed the
10930 overlay mapping yourself using @value{GDBN}. This command is only
10931 useful when using automatic overlay debugging.
10933 @item overlay list-overlays
10934 @itemx overlay list
10935 @cindex listing mapped overlays
10936 Display a list of the overlays currently mapped, along with their mapped
10937 addresses, load addresses, and sizes.
10941 Normally, when @value{GDBN} prints a code address, it includes the name
10942 of the function the address falls in:
10945 (@value{GDBP}) print main
10946 $3 = @{int ()@} 0x11a0 <main>
10949 When overlay debugging is enabled, @value{GDBN} recognizes code in
10950 unmapped overlays, and prints the names of unmapped functions with
10951 asterisks around them. For example, if @code{foo} is a function in an
10952 unmapped overlay, @value{GDBN} prints it this way:
10955 (@value{GDBP}) overlay list
10956 No sections are mapped.
10957 (@value{GDBP}) print foo
10958 $5 = @{int (int)@} 0x100000 <*foo*>
10961 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10965 (@value{GDBP}) overlay list
10966 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10967 mapped at 0x1016 - 0x104a
10968 (@value{GDBP}) print foo
10969 $6 = @{int (int)@} 0x1016 <foo>
10972 When overlay debugging is enabled, @value{GDBN} can find the correct
10973 address for functions and variables in an overlay, whether or not the
10974 overlay is mapped. This allows most @value{GDBN} commands, like
10975 @code{break} and @code{disassemble}, to work normally, even on unmapped
10976 code. However, @value{GDBN}'s breakpoint support has some limitations:
10980 @cindex breakpoints in overlays
10981 @cindex overlays, setting breakpoints in
10982 You can set breakpoints in functions in unmapped overlays, as long as
10983 @value{GDBN} can write to the overlay at its load address.
10985 @value{GDBN} can not set hardware or simulator-based breakpoints in
10986 unmapped overlays. However, if you set a breakpoint at the end of your
10987 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10988 you are using manual overlay management), @value{GDBN} will re-set its
10989 breakpoints properly.
10993 @node Automatic Overlay Debugging
10994 @section Automatic Overlay Debugging
10995 @cindex automatic overlay debugging
10997 @value{GDBN} can automatically track which overlays are mapped and which
10998 are not, given some simple co-operation from the overlay manager in the
10999 inferior. If you enable automatic overlay debugging with the
11000 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11001 looks in the inferior's memory for certain variables describing the
11002 current state of the overlays.
11004 Here are the variables your overlay manager must define to support
11005 @value{GDBN}'s automatic overlay debugging:
11009 @item @code{_ovly_table}:
11010 This variable must be an array of the following structures:
11015 /* The overlay's mapped address. */
11018 /* The size of the overlay, in bytes. */
11019 unsigned long size;
11021 /* The overlay's load address. */
11024 /* Non-zero if the overlay is currently mapped;
11026 unsigned long mapped;
11030 @item @code{_novlys}:
11031 This variable must be a four-byte signed integer, holding the total
11032 number of elements in @code{_ovly_table}.
11036 To decide whether a particular overlay is mapped or not, @value{GDBN}
11037 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11038 @code{lma} members equal the VMA and LMA of the overlay's section in the
11039 executable file. When @value{GDBN} finds a matching entry, it consults
11040 the entry's @code{mapped} member to determine whether the overlay is
11043 In addition, your overlay manager may define a function called
11044 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11045 will silently set a breakpoint there. If the overlay manager then
11046 calls this function whenever it has changed the overlay table, this
11047 will enable @value{GDBN} to accurately keep track of which overlays
11048 are in program memory, and update any breakpoints that may be set
11049 in overlays. This will allow breakpoints to work even if the
11050 overlays are kept in ROM or other non-writable memory while they
11051 are not being executed.
11053 @node Overlay Sample Program
11054 @section Overlay Sample Program
11055 @cindex overlay example program
11057 When linking a program which uses overlays, you must place the overlays
11058 at their load addresses, while relocating them to run at their mapped
11059 addresses. To do this, you must write a linker script (@pxref{Overlay
11060 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11061 since linker scripts are specific to a particular host system, target
11062 architecture, and target memory layout, this manual cannot provide
11063 portable sample code demonstrating @value{GDBN}'s overlay support.
11065 However, the @value{GDBN} source distribution does contain an overlaid
11066 program, with linker scripts for a few systems, as part of its test
11067 suite. The program consists of the following files from
11068 @file{gdb/testsuite/gdb.base}:
11072 The main program file.
11074 A simple overlay manager, used by @file{overlays.c}.
11079 Overlay modules, loaded and used by @file{overlays.c}.
11082 Linker scripts for linking the test program on the @code{d10v-elf}
11083 and @code{m32r-elf} targets.
11086 You can build the test program using the @code{d10v-elf} GCC
11087 cross-compiler like this:
11090 $ d10v-elf-gcc -g -c overlays.c
11091 $ d10v-elf-gcc -g -c ovlymgr.c
11092 $ d10v-elf-gcc -g -c foo.c
11093 $ d10v-elf-gcc -g -c bar.c
11094 $ d10v-elf-gcc -g -c baz.c
11095 $ d10v-elf-gcc -g -c grbx.c
11096 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11097 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11100 The build process is identical for any other architecture, except that
11101 you must substitute the appropriate compiler and linker script for the
11102 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11106 @chapter Using @value{GDBN} with Different Languages
11109 Although programming languages generally have common aspects, they are
11110 rarely expressed in the same manner. For instance, in ANSI C,
11111 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11112 Modula-2, it is accomplished by @code{p^}. Values can also be
11113 represented (and displayed) differently. Hex numbers in C appear as
11114 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11116 @cindex working language
11117 Language-specific information is built into @value{GDBN} for some languages,
11118 allowing you to express operations like the above in your program's
11119 native language, and allowing @value{GDBN} to output values in a manner
11120 consistent with the syntax of your program's native language. The
11121 language you use to build expressions is called the @dfn{working
11125 * Setting:: Switching between source languages
11126 * Show:: Displaying the language
11127 * Checks:: Type and range checks
11128 * Supported Languages:: Supported languages
11129 * Unsupported Languages:: Unsupported languages
11133 @section Switching Between Source Languages
11135 There are two ways to control the working language---either have @value{GDBN}
11136 set it automatically, or select it manually yourself. You can use the
11137 @code{set language} command for either purpose. On startup, @value{GDBN}
11138 defaults to setting the language automatically. The working language is
11139 used to determine how expressions you type are interpreted, how values
11142 In addition to the working language, every source file that
11143 @value{GDBN} knows about has its own working language. For some object
11144 file formats, the compiler might indicate which language a particular
11145 source file is in. However, most of the time @value{GDBN} infers the
11146 language from the name of the file. The language of a source file
11147 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11148 show each frame appropriately for its own language. There is no way to
11149 set the language of a source file from within @value{GDBN}, but you can
11150 set the language associated with a filename extension. @xref{Show, ,
11151 Displaying the Language}.
11153 This is most commonly a problem when you use a program, such
11154 as @code{cfront} or @code{f2c}, that generates C but is written in
11155 another language. In that case, make the
11156 program use @code{#line} directives in its C output; that way
11157 @value{GDBN} will know the correct language of the source code of the original
11158 program, and will display that source code, not the generated C code.
11161 * Filenames:: Filename extensions and languages.
11162 * Manually:: Setting the working language manually
11163 * Automatically:: Having @value{GDBN} infer the source language
11167 @subsection List of Filename Extensions and Languages
11169 If a source file name ends in one of the following extensions, then
11170 @value{GDBN} infers that its language is the one indicated.
11188 C@t{++} source file
11194 Objective-C source file
11198 Fortran source file
11201 Modula-2 source file
11205 Assembler source file. This actually behaves almost like C, but
11206 @value{GDBN} does not skip over function prologues when stepping.
11209 In addition, you may set the language associated with a filename
11210 extension. @xref{Show, , Displaying the Language}.
11213 @subsection Setting the Working Language
11215 If you allow @value{GDBN} to set the language automatically,
11216 expressions are interpreted the same way in your debugging session and
11219 @kindex set language
11220 If you wish, you may set the language manually. To do this, issue the
11221 command @samp{set language @var{lang}}, where @var{lang} is the name of
11222 a language, such as
11223 @code{c} or @code{modula-2}.
11224 For a list of the supported languages, type @samp{set language}.
11226 Setting the language manually prevents @value{GDBN} from updating the working
11227 language automatically. This can lead to confusion if you try
11228 to debug a program when the working language is not the same as the
11229 source language, when an expression is acceptable to both
11230 languages---but means different things. For instance, if the current
11231 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11239 might not have the effect you intended. In C, this means to add
11240 @code{b} and @code{c} and place the result in @code{a}. The result
11241 printed would be the value of @code{a}. In Modula-2, this means to compare
11242 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11244 @node Automatically
11245 @subsection Having @value{GDBN} Infer the Source Language
11247 To have @value{GDBN} set the working language automatically, use
11248 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11249 then infers the working language. That is, when your program stops in a
11250 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11251 working language to the language recorded for the function in that
11252 frame. If the language for a frame is unknown (that is, if the function
11253 or block corresponding to the frame was defined in a source file that
11254 does not have a recognized extension), the current working language is
11255 not changed, and @value{GDBN} issues a warning.
11257 This may not seem necessary for most programs, which are written
11258 entirely in one source language. However, program modules and libraries
11259 written in one source language can be used by a main program written in
11260 a different source language. Using @samp{set language auto} in this
11261 case frees you from having to set the working language manually.
11264 @section Displaying the Language
11266 The following commands help you find out which language is the
11267 working language, and also what language source files were written in.
11270 @item show language
11271 @kindex show language
11272 Display the current working language. This is the
11273 language you can use with commands such as @code{print} to
11274 build and compute expressions that may involve variables in your program.
11277 @kindex info frame@r{, show the source language}
11278 Display the source language for this frame. This language becomes the
11279 working language if you use an identifier from this frame.
11280 @xref{Frame Info, ,Information about a Frame}, to identify the other
11281 information listed here.
11284 @kindex info source@r{, show the source language}
11285 Display the source language of this source file.
11286 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11287 information listed here.
11290 In unusual circumstances, you may have source files with extensions
11291 not in the standard list. You can then set the extension associated
11292 with a language explicitly:
11295 @item set extension-language @var{ext} @var{language}
11296 @kindex set extension-language
11297 Tell @value{GDBN} that source files with extension @var{ext} are to be
11298 assumed as written in the source language @var{language}.
11300 @item info extensions
11301 @kindex info extensions
11302 List all the filename extensions and the associated languages.
11306 @section Type and Range Checking
11309 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11310 checking are included, but they do not yet have any effect. This
11311 section documents the intended facilities.
11313 @c FIXME remove warning when type/range code added
11315 Some languages are designed to guard you against making seemingly common
11316 errors through a series of compile- and run-time checks. These include
11317 checking the type of arguments to functions and operators, and making
11318 sure mathematical overflows are caught at run time. Checks such as
11319 these help to ensure a program's correctness once it has been compiled
11320 by eliminating type mismatches, and providing active checks for range
11321 errors when your program is running.
11323 @value{GDBN} can check for conditions like the above if you wish.
11324 Although @value{GDBN} does not check the statements in your program,
11325 it can check expressions entered directly into @value{GDBN} for
11326 evaluation via the @code{print} command, for example. As with the
11327 working language, @value{GDBN} can also decide whether or not to check
11328 automatically based on your program's source language.
11329 @xref{Supported Languages, ,Supported Languages}, for the default
11330 settings of supported languages.
11333 * Type Checking:: An overview of type checking
11334 * Range Checking:: An overview of range checking
11337 @cindex type checking
11338 @cindex checks, type
11339 @node Type Checking
11340 @subsection An Overview of Type Checking
11342 Some languages, such as Modula-2, are strongly typed, meaning that the
11343 arguments to operators and functions have to be of the correct type,
11344 otherwise an error occurs. These checks prevent type mismatch
11345 errors from ever causing any run-time problems. For example,
11353 The second example fails because the @code{CARDINAL} 1 is not
11354 type-compatible with the @code{REAL} 2.3.
11356 For the expressions you use in @value{GDBN} commands, you can tell the
11357 @value{GDBN} type checker to skip checking;
11358 to treat any mismatches as errors and abandon the expression;
11359 or to only issue warnings when type mismatches occur,
11360 but evaluate the expression anyway. When you choose the last of
11361 these, @value{GDBN} evaluates expressions like the second example above, but
11362 also issues a warning.
11364 Even if you turn type checking off, there may be other reasons
11365 related to type that prevent @value{GDBN} from evaluating an expression.
11366 For instance, @value{GDBN} does not know how to add an @code{int} and
11367 a @code{struct foo}. These particular type errors have nothing to do
11368 with the language in use, and usually arise from expressions, such as
11369 the one described above, which make little sense to evaluate anyway.
11371 Each language defines to what degree it is strict about type. For
11372 instance, both Modula-2 and C require the arguments to arithmetical
11373 operators to be numbers. In C, enumerated types and pointers can be
11374 represented as numbers, so that they are valid arguments to mathematical
11375 operators. @xref{Supported Languages, ,Supported Languages}, for further
11376 details on specific languages.
11378 @value{GDBN} provides some additional commands for controlling the type checker:
11380 @kindex set check type
11381 @kindex show check type
11383 @item set check type auto
11384 Set type checking on or off based on the current working language.
11385 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11388 @item set check type on
11389 @itemx set check type off
11390 Set type checking on or off, overriding the default setting for the
11391 current working language. Issue a warning if the setting does not
11392 match the language default. If any type mismatches occur in
11393 evaluating an expression while type checking is on, @value{GDBN} prints a
11394 message and aborts evaluation of the expression.
11396 @item set check type warn
11397 Cause the type checker to issue warnings, but to always attempt to
11398 evaluate the expression. Evaluating the expression may still
11399 be impossible for other reasons. For example, @value{GDBN} cannot add
11400 numbers and structures.
11403 Show the current setting of the type checker, and whether or not @value{GDBN}
11404 is setting it automatically.
11407 @cindex range checking
11408 @cindex checks, range
11409 @node Range Checking
11410 @subsection An Overview of Range Checking
11412 In some languages (such as Modula-2), it is an error to exceed the
11413 bounds of a type; this is enforced with run-time checks. Such range
11414 checking is meant to ensure program correctness by making sure
11415 computations do not overflow, or indices on an array element access do
11416 not exceed the bounds of the array.
11418 For expressions you use in @value{GDBN} commands, you can tell
11419 @value{GDBN} to treat range errors in one of three ways: ignore them,
11420 always treat them as errors and abandon the expression, or issue
11421 warnings but evaluate the expression anyway.
11423 A range error can result from numerical overflow, from exceeding an
11424 array index bound, or when you type a constant that is not a member
11425 of any type. Some languages, however, do not treat overflows as an
11426 error. In many implementations of C, mathematical overflow causes the
11427 result to ``wrap around'' to lower values---for example, if @var{m} is
11428 the largest integer value, and @var{s} is the smallest, then
11431 @var{m} + 1 @result{} @var{s}
11434 This, too, is specific to individual languages, and in some cases
11435 specific to individual compilers or machines. @xref{Supported Languages, ,
11436 Supported Languages}, for further details on specific languages.
11438 @value{GDBN} provides some additional commands for controlling the range checker:
11440 @kindex set check range
11441 @kindex show check range
11443 @item set check range auto
11444 Set range checking on or off based on the current working language.
11445 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11448 @item set check range on
11449 @itemx set check range off
11450 Set range checking on or off, overriding the default setting for the
11451 current working language. A warning is issued if the setting does not
11452 match the language default. If a range error occurs and range checking is on,
11453 then a message is printed and evaluation of the expression is aborted.
11455 @item set check range warn
11456 Output messages when the @value{GDBN} range checker detects a range error,
11457 but attempt to evaluate the expression anyway. Evaluating the
11458 expression may still be impossible for other reasons, such as accessing
11459 memory that the process does not own (a typical example from many Unix
11463 Show the current setting of the range checker, and whether or not it is
11464 being set automatically by @value{GDBN}.
11467 @node Supported Languages
11468 @section Supported Languages
11470 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, Pascal,
11471 assembly, Modula-2, and Ada.
11472 @c This is false ...
11473 Some @value{GDBN} features may be used in expressions regardless of the
11474 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11475 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11476 ,Expressions}) can be used with the constructs of any supported
11479 The following sections detail to what degree each source language is
11480 supported by @value{GDBN}. These sections are not meant to be language
11481 tutorials or references, but serve only as a reference guide to what the
11482 @value{GDBN} expression parser accepts, and what input and output
11483 formats should look like for different languages. There are many good
11484 books written on each of these languages; please look to these for a
11485 language reference or tutorial.
11488 * C:: C and C@t{++}
11490 * Objective-C:: Objective-C
11491 * Fortran:: Fortran
11493 * Modula-2:: Modula-2
11498 @subsection C and C@t{++}
11500 @cindex C and C@t{++}
11501 @cindex expressions in C or C@t{++}
11503 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11504 to both languages. Whenever this is the case, we discuss those languages
11508 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11509 @cindex @sc{gnu} C@t{++}
11510 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11511 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11512 effectively, you must compile your C@t{++} programs with a supported
11513 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11514 compiler (@code{aCC}).
11516 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11517 format; if it doesn't work on your system, try the stabs+ debugging
11518 format. You can select those formats explicitly with the @code{g++}
11519 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11520 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11521 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11524 * C Operators:: C and C@t{++} operators
11525 * C Constants:: C and C@t{++} constants
11526 * C Plus Plus Expressions:: C@t{++} expressions
11527 * C Defaults:: Default settings for C and C@t{++}
11528 * C Checks:: C and C@t{++} type and range checks
11529 * Debugging C:: @value{GDBN} and C
11530 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11531 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11535 @subsubsection C and C@t{++} Operators
11537 @cindex C and C@t{++} operators
11539 Operators must be defined on values of specific types. For instance,
11540 @code{+} is defined on numbers, but not on structures. Operators are
11541 often defined on groups of types.
11543 For the purposes of C and C@t{++}, the following definitions hold:
11548 @emph{Integral types} include @code{int} with any of its storage-class
11549 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11552 @emph{Floating-point types} include @code{float}, @code{double}, and
11553 @code{long double} (if supported by the target platform).
11556 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11559 @emph{Scalar types} include all of the above.
11564 The following operators are supported. They are listed here
11565 in order of increasing precedence:
11569 The comma or sequencing operator. Expressions in a comma-separated list
11570 are evaluated from left to right, with the result of the entire
11571 expression being the last expression evaluated.
11574 Assignment. The value of an assignment expression is the value
11575 assigned. Defined on scalar types.
11578 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11579 and translated to @w{@code{@var{a} = @var{a op b}}}.
11580 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11581 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11582 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11585 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11586 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11590 Logical @sc{or}. Defined on integral types.
11593 Logical @sc{and}. Defined on integral types.
11596 Bitwise @sc{or}. Defined on integral types.
11599 Bitwise exclusive-@sc{or}. Defined on integral types.
11602 Bitwise @sc{and}. Defined on integral types.
11605 Equality and inequality. Defined on scalar types. The value of these
11606 expressions is 0 for false and non-zero for true.
11608 @item <@r{, }>@r{, }<=@r{, }>=
11609 Less than, greater than, less than or equal, greater than or equal.
11610 Defined on scalar types. The value of these expressions is 0 for false
11611 and non-zero for true.
11614 left shift, and right shift. Defined on integral types.
11617 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11620 Addition and subtraction. Defined on integral types, floating-point types and
11623 @item *@r{, }/@r{, }%
11624 Multiplication, division, and modulus. Multiplication and division are
11625 defined on integral and floating-point types. Modulus is defined on
11629 Increment and decrement. When appearing before a variable, the
11630 operation is performed before the variable is used in an expression;
11631 when appearing after it, the variable's value is used before the
11632 operation takes place.
11635 Pointer dereferencing. Defined on pointer types. Same precedence as
11639 Address operator. Defined on variables. Same precedence as @code{++}.
11641 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11642 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11643 to examine the address
11644 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11648 Negative. Defined on integral and floating-point types. Same
11649 precedence as @code{++}.
11652 Logical negation. Defined on integral types. Same precedence as
11656 Bitwise complement operator. Defined on integral types. Same precedence as
11661 Structure member, and pointer-to-structure member. For convenience,
11662 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11663 pointer based on the stored type information.
11664 Defined on @code{struct} and @code{union} data.
11667 Dereferences of pointers to members.
11670 Array indexing. @code{@var{a}[@var{i}]} is defined as
11671 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11674 Function parameter list. Same precedence as @code{->}.
11677 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11678 and @code{class} types.
11681 Doubled colons also represent the @value{GDBN} scope operator
11682 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11686 If an operator is redefined in the user code, @value{GDBN} usually
11687 attempts to invoke the redefined version instead of using the operator's
11688 predefined meaning.
11691 @subsubsection C and C@t{++} Constants
11693 @cindex C and C@t{++} constants
11695 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11700 Integer constants are a sequence of digits. Octal constants are
11701 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11702 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11703 @samp{l}, specifying that the constant should be treated as a
11707 Floating point constants are a sequence of digits, followed by a decimal
11708 point, followed by a sequence of digits, and optionally followed by an
11709 exponent. An exponent is of the form:
11710 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11711 sequence of digits. The @samp{+} is optional for positive exponents.
11712 A floating-point constant may also end with a letter @samp{f} or
11713 @samp{F}, specifying that the constant should be treated as being of
11714 the @code{float} (as opposed to the default @code{double}) type; or with
11715 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11719 Enumerated constants consist of enumerated identifiers, or their
11720 integral equivalents.
11723 Character constants are a single character surrounded by single quotes
11724 (@code{'}), or a number---the ordinal value of the corresponding character
11725 (usually its @sc{ascii} value). Within quotes, the single character may
11726 be represented by a letter or by @dfn{escape sequences}, which are of
11727 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11728 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11729 @samp{@var{x}} is a predefined special character---for example,
11730 @samp{\n} for newline.
11733 String constants are a sequence of character constants surrounded by
11734 double quotes (@code{"}). Any valid character constant (as described
11735 above) may appear. Double quotes within the string must be preceded by
11736 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11740 Pointer constants are an integral value. You can also write pointers
11741 to constants using the C operator @samp{&}.
11744 Array constants are comma-separated lists surrounded by braces @samp{@{}
11745 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11746 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11747 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11750 @node C Plus Plus Expressions
11751 @subsubsection C@t{++} Expressions
11753 @cindex expressions in C@t{++}
11754 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11756 @cindex debugging C@t{++} programs
11757 @cindex C@t{++} compilers
11758 @cindex debug formats and C@t{++}
11759 @cindex @value{NGCC} and C@t{++}
11761 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11762 proper compiler and the proper debug format. Currently, @value{GDBN}
11763 works best when debugging C@t{++} code that is compiled with
11764 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11765 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11766 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11767 stabs+ as their default debug format, so you usually don't need to
11768 specify a debug format explicitly. Other compilers and/or debug formats
11769 are likely to work badly or not at all when using @value{GDBN} to debug
11775 @cindex member functions
11777 Member function calls are allowed; you can use expressions like
11780 count = aml->GetOriginal(x, y)
11783 @vindex this@r{, inside C@t{++} member functions}
11784 @cindex namespace in C@t{++}
11786 While a member function is active (in the selected stack frame), your
11787 expressions have the same namespace available as the member function;
11788 that is, @value{GDBN} allows implicit references to the class instance
11789 pointer @code{this} following the same rules as C@t{++}.
11791 @cindex call overloaded functions
11792 @cindex overloaded functions, calling
11793 @cindex type conversions in C@t{++}
11795 You can call overloaded functions; @value{GDBN} resolves the function
11796 call to the right definition, with some restrictions. @value{GDBN} does not
11797 perform overload resolution involving user-defined type conversions,
11798 calls to constructors, or instantiations of templates that do not exist
11799 in the program. It also cannot handle ellipsis argument lists or
11802 It does perform integral conversions and promotions, floating-point
11803 promotions, arithmetic conversions, pointer conversions, conversions of
11804 class objects to base classes, and standard conversions such as those of
11805 functions or arrays to pointers; it requires an exact match on the
11806 number of function arguments.
11808 Overload resolution is always performed, unless you have specified
11809 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11810 ,@value{GDBN} Features for C@t{++}}.
11812 You must specify @code{set overload-resolution off} in order to use an
11813 explicit function signature to call an overloaded function, as in
11815 p 'foo(char,int)'('x', 13)
11818 The @value{GDBN} command-completion facility can simplify this;
11819 see @ref{Completion, ,Command Completion}.
11821 @cindex reference declarations
11823 @value{GDBN} understands variables declared as C@t{++} references; you can use
11824 them in expressions just as you do in C@t{++} source---they are automatically
11827 In the parameter list shown when @value{GDBN} displays a frame, the values of
11828 reference variables are not displayed (unlike other variables); this
11829 avoids clutter, since references are often used for large structures.
11830 The @emph{address} of a reference variable is always shown, unless
11831 you have specified @samp{set print address off}.
11834 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11835 expressions can use it just as expressions in your program do. Since
11836 one scope may be defined in another, you can use @code{::} repeatedly if
11837 necessary, for example in an expression like
11838 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11839 resolving name scope by reference to source files, in both C and C@t{++}
11840 debugging (@pxref{Variables, ,Program Variables}).
11843 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11844 calling virtual functions correctly, printing out virtual bases of
11845 objects, calling functions in a base subobject, casting objects, and
11846 invoking user-defined operators.
11849 @subsubsection C and C@t{++} Defaults
11851 @cindex C and C@t{++} defaults
11853 If you allow @value{GDBN} to set type and range checking automatically, they
11854 both default to @code{off} whenever the working language changes to
11855 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11856 selects the working language.
11858 If you allow @value{GDBN} to set the language automatically, it
11859 recognizes source files whose names end with @file{.c}, @file{.C}, or
11860 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11861 these files, it sets the working language to C or C@t{++}.
11862 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11863 for further details.
11865 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11866 @c unimplemented. If (b) changes, it might make sense to let this node
11867 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11870 @subsubsection C and C@t{++} Type and Range Checks
11872 @cindex C and C@t{++} checks
11874 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11875 is not used. However, if you turn type checking on, @value{GDBN}
11876 considers two variables type equivalent if:
11880 The two variables are structured and have the same structure, union, or
11884 The two variables have the same type name, or types that have been
11885 declared equivalent through @code{typedef}.
11888 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11891 The two @code{struct}, @code{union}, or @code{enum} variables are
11892 declared in the same declaration. (Note: this may not be true for all C
11897 Range checking, if turned on, is done on mathematical operations. Array
11898 indices are not checked, since they are often used to index a pointer
11899 that is not itself an array.
11902 @subsubsection @value{GDBN} and C
11904 The @code{set print union} and @code{show print union} commands apply to
11905 the @code{union} type. When set to @samp{on}, any @code{union} that is
11906 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11907 appears as @samp{@{...@}}.
11909 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11910 with pointers and a memory allocation function. @xref{Expressions,
11913 @node Debugging C Plus Plus
11914 @subsubsection @value{GDBN} Features for C@t{++}
11916 @cindex commands for C@t{++}
11918 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11919 designed specifically for use with C@t{++}. Here is a summary:
11922 @cindex break in overloaded functions
11923 @item @r{breakpoint menus}
11924 When you want a breakpoint in a function whose name is overloaded,
11925 @value{GDBN} has the capability to display a menu of possible breakpoint
11926 locations to help you specify which function definition you want.
11927 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11929 @cindex overloading in C@t{++}
11930 @item rbreak @var{regex}
11931 Setting breakpoints using regular expressions is helpful for setting
11932 breakpoints on overloaded functions that are not members of any special
11934 @xref{Set Breaks, ,Setting Breakpoints}.
11936 @cindex C@t{++} exception handling
11939 Debug C@t{++} exception handling using these commands. @xref{Set
11940 Catchpoints, , Setting Catchpoints}.
11942 @cindex inheritance
11943 @item ptype @var{typename}
11944 Print inheritance relationships as well as other information for type
11946 @xref{Symbols, ,Examining the Symbol Table}.
11948 @cindex C@t{++} symbol display
11949 @item set print demangle
11950 @itemx show print demangle
11951 @itemx set print asm-demangle
11952 @itemx show print asm-demangle
11953 Control whether C@t{++} symbols display in their source form, both when
11954 displaying code as C@t{++} source and when displaying disassemblies.
11955 @xref{Print Settings, ,Print Settings}.
11957 @item set print object
11958 @itemx show print object
11959 Choose whether to print derived (actual) or declared types of objects.
11960 @xref{Print Settings, ,Print Settings}.
11962 @item set print vtbl
11963 @itemx show print vtbl
11964 Control the format for printing virtual function tables.
11965 @xref{Print Settings, ,Print Settings}.
11966 (The @code{vtbl} commands do not work on programs compiled with the HP
11967 ANSI C@t{++} compiler (@code{aCC}).)
11969 @kindex set overload-resolution
11970 @cindex overloaded functions, overload resolution
11971 @item set overload-resolution on
11972 Enable overload resolution for C@t{++} expression evaluation. The default
11973 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11974 and searches for a function whose signature matches the argument types,
11975 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11976 Expressions, ,C@t{++} Expressions}, for details).
11977 If it cannot find a match, it emits a message.
11979 @item set overload-resolution off
11980 Disable overload resolution for C@t{++} expression evaluation. For
11981 overloaded functions that are not class member functions, @value{GDBN}
11982 chooses the first function of the specified name that it finds in the
11983 symbol table, whether or not its arguments are of the correct type. For
11984 overloaded functions that are class member functions, @value{GDBN}
11985 searches for a function whose signature @emph{exactly} matches the
11988 @kindex show overload-resolution
11989 @item show overload-resolution
11990 Show the current setting of overload resolution.
11992 @item @r{Overloaded symbol names}
11993 You can specify a particular definition of an overloaded symbol, using
11994 the same notation that is used to declare such symbols in C@t{++}: type
11995 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
11996 also use the @value{GDBN} command-line word completion facilities to list the
11997 available choices, or to finish the type list for you.
11998 @xref{Completion,, Command Completion}, for details on how to do this.
12001 @node Decimal Floating Point
12002 @subsubsection Decimal Floating Point format
12003 @cindex decimal floating point format
12005 @value{GDBN} can examine, set and perform computations with numbers in
12006 decimal floating point format, which in the C language correspond to the
12007 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12008 specified by the extension to support decimal floating-point arithmetic.
12010 There are two encodings in use, depending on the architecture: BID (Binary
12011 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12012 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12015 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12016 to manipulate decimal floating point numbers, it is not possible to convert
12017 (using a cast, for example) integers wider than 32-bit to decimal float.
12019 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12020 point computations, error checking in decimal float operations ignores
12021 underflow, overflow and divide by zero exceptions.
12023 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12024 to inspect @code{_Decimal128} values stored in floating point registers.
12025 See @ref{PowerPC,,PowerPC} for more details.
12031 @value{GDBN} can be used to debug programs written in D and compiled with
12032 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12033 specific feature --- dynamic arrays.
12036 @subsection Objective-C
12038 @cindex Objective-C
12039 This section provides information about some commands and command
12040 options that are useful for debugging Objective-C code. See also
12041 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12042 few more commands specific to Objective-C support.
12045 * Method Names in Commands::
12046 * The Print Command with Objective-C::
12049 @node Method Names in Commands
12050 @subsubsection Method Names in Commands
12052 The following commands have been extended to accept Objective-C method
12053 names as line specifications:
12055 @kindex clear@r{, and Objective-C}
12056 @kindex break@r{, and Objective-C}
12057 @kindex info line@r{, and Objective-C}
12058 @kindex jump@r{, and Objective-C}
12059 @kindex list@r{, and Objective-C}
12063 @item @code{info line}
12068 A fully qualified Objective-C method name is specified as
12071 -[@var{Class} @var{methodName}]
12074 where the minus sign is used to indicate an instance method and a
12075 plus sign (not shown) is used to indicate a class method. The class
12076 name @var{Class} and method name @var{methodName} are enclosed in
12077 brackets, similar to the way messages are specified in Objective-C
12078 source code. For example, to set a breakpoint at the @code{create}
12079 instance method of class @code{Fruit} in the program currently being
12083 break -[Fruit create]
12086 To list ten program lines around the @code{initialize} class method,
12090 list +[NSText initialize]
12093 In the current version of @value{GDBN}, the plus or minus sign is
12094 required. In future versions of @value{GDBN}, the plus or minus
12095 sign will be optional, but you can use it to narrow the search. It
12096 is also possible to specify just a method name:
12102 You must specify the complete method name, including any colons. If
12103 your program's source files contain more than one @code{create} method,
12104 you'll be presented with a numbered list of classes that implement that
12105 method. Indicate your choice by number, or type @samp{0} to exit if
12108 As another example, to clear a breakpoint established at the
12109 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12112 clear -[NSWindow makeKeyAndOrderFront:]
12115 @node The Print Command with Objective-C
12116 @subsubsection The Print Command With Objective-C
12117 @cindex Objective-C, print objects
12118 @kindex print-object
12119 @kindex po @r{(@code{print-object})}
12121 The print command has also been extended to accept methods. For example:
12124 print -[@var{object} hash]
12127 @cindex print an Objective-C object description
12128 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12130 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12131 and print the result. Also, an additional command has been added,
12132 @code{print-object} or @code{po} for short, which is meant to print
12133 the description of an object. However, this command may only work
12134 with certain Objective-C libraries that have a particular hook
12135 function, @code{_NSPrintForDebugger}, defined.
12138 @subsection Fortran
12139 @cindex Fortran-specific support in @value{GDBN}
12141 @value{GDBN} can be used to debug programs written in Fortran, but it
12142 currently supports only the features of Fortran 77 language.
12144 @cindex trailing underscore, in Fortran symbols
12145 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12146 among them) append an underscore to the names of variables and
12147 functions. When you debug programs compiled by those compilers, you
12148 will need to refer to variables and functions with a trailing
12152 * Fortran Operators:: Fortran operators and expressions
12153 * Fortran Defaults:: Default settings for Fortran
12154 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12157 @node Fortran Operators
12158 @subsubsection Fortran Operators and Expressions
12160 @cindex Fortran operators and expressions
12162 Operators must be defined on values of specific types. For instance,
12163 @code{+} is defined on numbers, but not on characters or other non-
12164 arithmetic types. Operators are often defined on groups of types.
12168 The exponentiation operator. It raises the first operand to the power
12172 The range operator. Normally used in the form of array(low:high) to
12173 represent a section of array.
12176 The access component operator. Normally used to access elements in derived
12177 types. Also suitable for unions. As unions aren't part of regular Fortran,
12178 this can only happen when accessing a register that uses a gdbarch-defined
12182 @node Fortran Defaults
12183 @subsubsection Fortran Defaults
12185 @cindex Fortran Defaults
12187 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12188 default uses case-insensitive matches for Fortran symbols. You can
12189 change that with the @samp{set case-insensitive} command, see
12190 @ref{Symbols}, for the details.
12192 @node Special Fortran Commands
12193 @subsubsection Special Fortran Commands
12195 @cindex Special Fortran commands
12197 @value{GDBN} has some commands to support Fortran-specific features,
12198 such as displaying common blocks.
12201 @cindex @code{COMMON} blocks, Fortran
12202 @kindex info common
12203 @item info common @r{[}@var{common-name}@r{]}
12204 This command prints the values contained in the Fortran @code{COMMON}
12205 block whose name is @var{common-name}. With no argument, the names of
12206 all @code{COMMON} blocks visible at the current program location are
12213 @cindex Pascal support in @value{GDBN}, limitations
12214 Debugging Pascal programs which use sets, subranges, file variables, or
12215 nested functions does not currently work. @value{GDBN} does not support
12216 entering expressions, printing values, or similar features using Pascal
12219 The Pascal-specific command @code{set print pascal_static-members}
12220 controls whether static members of Pascal objects are displayed.
12221 @xref{Print Settings, pascal_static-members}.
12224 @subsection Modula-2
12226 @cindex Modula-2, @value{GDBN} support
12228 The extensions made to @value{GDBN} to support Modula-2 only support
12229 output from the @sc{gnu} Modula-2 compiler (which is currently being
12230 developed). Other Modula-2 compilers are not currently supported, and
12231 attempting to debug executables produced by them is most likely
12232 to give an error as @value{GDBN} reads in the executable's symbol
12235 @cindex expressions in Modula-2
12237 * M2 Operators:: Built-in operators
12238 * Built-In Func/Proc:: Built-in functions and procedures
12239 * M2 Constants:: Modula-2 constants
12240 * M2 Types:: Modula-2 types
12241 * M2 Defaults:: Default settings for Modula-2
12242 * Deviations:: Deviations from standard Modula-2
12243 * M2 Checks:: Modula-2 type and range checks
12244 * M2 Scope:: The scope operators @code{::} and @code{.}
12245 * GDB/M2:: @value{GDBN} and Modula-2
12249 @subsubsection Operators
12250 @cindex Modula-2 operators
12252 Operators must be defined on values of specific types. For instance,
12253 @code{+} is defined on numbers, but not on structures. Operators are
12254 often defined on groups of types. For the purposes of Modula-2, the
12255 following definitions hold:
12260 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12264 @emph{Character types} consist of @code{CHAR} and its subranges.
12267 @emph{Floating-point types} consist of @code{REAL}.
12270 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12274 @emph{Scalar types} consist of all of the above.
12277 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12280 @emph{Boolean types} consist of @code{BOOLEAN}.
12284 The following operators are supported, and appear in order of
12285 increasing precedence:
12289 Function argument or array index separator.
12292 Assignment. The value of @var{var} @code{:=} @var{value} is
12296 Less than, greater than on integral, floating-point, or enumerated
12300 Less than or equal to, greater than or equal to
12301 on integral, floating-point and enumerated types, or set inclusion on
12302 set types. Same precedence as @code{<}.
12304 @item =@r{, }<>@r{, }#
12305 Equality and two ways of expressing inequality, valid on scalar types.
12306 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12307 available for inequality, since @code{#} conflicts with the script
12311 Set membership. Defined on set types and the types of their members.
12312 Same precedence as @code{<}.
12315 Boolean disjunction. Defined on boolean types.
12318 Boolean conjunction. Defined on boolean types.
12321 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12324 Addition and subtraction on integral and floating-point types, or union
12325 and difference on set types.
12328 Multiplication on integral and floating-point types, or set intersection
12332 Division on floating-point types, or symmetric set difference on set
12333 types. Same precedence as @code{*}.
12336 Integer division and remainder. Defined on integral types. Same
12337 precedence as @code{*}.
12340 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12343 Pointer dereferencing. Defined on pointer types.
12346 Boolean negation. Defined on boolean types. Same precedence as
12350 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12351 precedence as @code{^}.
12354 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12357 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12361 @value{GDBN} and Modula-2 scope operators.
12365 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12366 treats the use of the operator @code{IN}, or the use of operators
12367 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12368 @code{<=}, and @code{>=} on sets as an error.
12372 @node Built-In Func/Proc
12373 @subsubsection Built-in Functions and Procedures
12374 @cindex Modula-2 built-ins
12376 Modula-2 also makes available several built-in procedures and functions.
12377 In describing these, the following metavariables are used:
12382 represents an @code{ARRAY} variable.
12385 represents a @code{CHAR} constant or variable.
12388 represents a variable or constant of integral type.
12391 represents an identifier that belongs to a set. Generally used in the
12392 same function with the metavariable @var{s}. The type of @var{s} should
12393 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12396 represents a variable or constant of integral or floating-point type.
12399 represents a variable or constant of floating-point type.
12405 represents a variable.
12408 represents a variable or constant of one of many types. See the
12409 explanation of the function for details.
12412 All Modula-2 built-in procedures also return a result, described below.
12416 Returns the absolute value of @var{n}.
12419 If @var{c} is a lower case letter, it returns its upper case
12420 equivalent, otherwise it returns its argument.
12423 Returns the character whose ordinal value is @var{i}.
12426 Decrements the value in the variable @var{v} by one. Returns the new value.
12428 @item DEC(@var{v},@var{i})
12429 Decrements the value in the variable @var{v} by @var{i}. Returns the
12432 @item EXCL(@var{m},@var{s})
12433 Removes the element @var{m} from the set @var{s}. Returns the new
12436 @item FLOAT(@var{i})
12437 Returns the floating point equivalent of the integer @var{i}.
12439 @item HIGH(@var{a})
12440 Returns the index of the last member of @var{a}.
12443 Increments the value in the variable @var{v} by one. Returns the new value.
12445 @item INC(@var{v},@var{i})
12446 Increments the value in the variable @var{v} by @var{i}. Returns the
12449 @item INCL(@var{m},@var{s})
12450 Adds the element @var{m} to the set @var{s} if it is not already
12451 there. Returns the new set.
12454 Returns the maximum value of the type @var{t}.
12457 Returns the minimum value of the type @var{t}.
12460 Returns boolean TRUE if @var{i} is an odd number.
12463 Returns the ordinal value of its argument. For example, the ordinal
12464 value of a character is its @sc{ascii} value (on machines supporting the
12465 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12466 integral, character and enumerated types.
12468 @item SIZE(@var{x})
12469 Returns the size of its argument. @var{x} can be a variable or a type.
12471 @item TRUNC(@var{r})
12472 Returns the integral part of @var{r}.
12474 @item TSIZE(@var{x})
12475 Returns the size of its argument. @var{x} can be a variable or a type.
12477 @item VAL(@var{t},@var{i})
12478 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12482 @emph{Warning:} Sets and their operations are not yet supported, so
12483 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12487 @cindex Modula-2 constants
12489 @subsubsection Constants
12491 @value{GDBN} allows you to express the constants of Modula-2 in the following
12497 Integer constants are simply a sequence of digits. When used in an
12498 expression, a constant is interpreted to be type-compatible with the
12499 rest of the expression. Hexadecimal integers are specified by a
12500 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12503 Floating point constants appear as a sequence of digits, followed by a
12504 decimal point and another sequence of digits. An optional exponent can
12505 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12506 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12507 digits of the floating point constant must be valid decimal (base 10)
12511 Character constants consist of a single character enclosed by a pair of
12512 like quotes, either single (@code{'}) or double (@code{"}). They may
12513 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12514 followed by a @samp{C}.
12517 String constants consist of a sequence of characters enclosed by a
12518 pair of like quotes, either single (@code{'}) or double (@code{"}).
12519 Escape sequences in the style of C are also allowed. @xref{C
12520 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12524 Enumerated constants consist of an enumerated identifier.
12527 Boolean constants consist of the identifiers @code{TRUE} and
12531 Pointer constants consist of integral values only.
12534 Set constants are not yet supported.
12538 @subsubsection Modula-2 Types
12539 @cindex Modula-2 types
12541 Currently @value{GDBN} can print the following data types in Modula-2
12542 syntax: array types, record types, set types, pointer types, procedure
12543 types, enumerated types, subrange types and base types. You can also
12544 print the contents of variables declared using these type.
12545 This section gives a number of simple source code examples together with
12546 sample @value{GDBN} sessions.
12548 The first example contains the following section of code:
12557 and you can request @value{GDBN} to interrogate the type and value of
12558 @code{r} and @code{s}.
12561 (@value{GDBP}) print s
12563 (@value{GDBP}) ptype s
12565 (@value{GDBP}) print r
12567 (@value{GDBP}) ptype r
12572 Likewise if your source code declares @code{s} as:
12576 s: SET ['A'..'Z'] ;
12580 then you may query the type of @code{s} by:
12583 (@value{GDBP}) ptype s
12584 type = SET ['A'..'Z']
12588 Note that at present you cannot interactively manipulate set
12589 expressions using the debugger.
12591 The following example shows how you might declare an array in Modula-2
12592 and how you can interact with @value{GDBN} to print its type and contents:
12596 s: ARRAY [-10..10] OF CHAR ;
12600 (@value{GDBP}) ptype s
12601 ARRAY [-10..10] OF CHAR
12604 Note that the array handling is not yet complete and although the type
12605 is printed correctly, expression handling still assumes that all
12606 arrays have a lower bound of zero and not @code{-10} as in the example
12609 Here are some more type related Modula-2 examples:
12613 colour = (blue, red, yellow, green) ;
12614 t = [blue..yellow] ;
12622 The @value{GDBN} interaction shows how you can query the data type
12623 and value of a variable.
12626 (@value{GDBP}) print s
12628 (@value{GDBP}) ptype t
12629 type = [blue..yellow]
12633 In this example a Modula-2 array is declared and its contents
12634 displayed. Observe that the contents are written in the same way as
12635 their @code{C} counterparts.
12639 s: ARRAY [1..5] OF CARDINAL ;
12645 (@value{GDBP}) print s
12646 $1 = @{1, 0, 0, 0, 0@}
12647 (@value{GDBP}) ptype s
12648 type = ARRAY [1..5] OF CARDINAL
12651 The Modula-2 language interface to @value{GDBN} also understands
12652 pointer types as shown in this example:
12656 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12663 and you can request that @value{GDBN} describes the type of @code{s}.
12666 (@value{GDBP}) ptype s
12667 type = POINTER TO ARRAY [1..5] OF CARDINAL
12670 @value{GDBN} handles compound types as we can see in this example.
12671 Here we combine array types, record types, pointer types and subrange
12682 myarray = ARRAY myrange OF CARDINAL ;
12683 myrange = [-2..2] ;
12685 s: POINTER TO ARRAY myrange OF foo ;
12689 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12693 (@value{GDBP}) ptype s
12694 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12697 f3 : ARRAY [-2..2] OF CARDINAL;
12702 @subsubsection Modula-2 Defaults
12703 @cindex Modula-2 defaults
12705 If type and range checking are set automatically by @value{GDBN}, they
12706 both default to @code{on} whenever the working language changes to
12707 Modula-2. This happens regardless of whether you or @value{GDBN}
12708 selected the working language.
12710 If you allow @value{GDBN} to set the language automatically, then entering
12711 code compiled from a file whose name ends with @file{.mod} sets the
12712 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12713 Infer the Source Language}, for further details.
12716 @subsubsection Deviations from Standard Modula-2
12717 @cindex Modula-2, deviations from
12719 A few changes have been made to make Modula-2 programs easier to debug.
12720 This is done primarily via loosening its type strictness:
12724 Unlike in standard Modula-2, pointer constants can be formed by
12725 integers. This allows you to modify pointer variables during
12726 debugging. (In standard Modula-2, the actual address contained in a
12727 pointer variable is hidden from you; it can only be modified
12728 through direct assignment to another pointer variable or expression that
12729 returned a pointer.)
12732 C escape sequences can be used in strings and characters to represent
12733 non-printable characters. @value{GDBN} prints out strings with these
12734 escape sequences embedded. Single non-printable characters are
12735 printed using the @samp{CHR(@var{nnn})} format.
12738 The assignment operator (@code{:=}) returns the value of its right-hand
12742 All built-in procedures both modify @emph{and} return their argument.
12746 @subsubsection Modula-2 Type and Range Checks
12747 @cindex Modula-2 checks
12750 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12753 @c FIXME remove warning when type/range checks added
12755 @value{GDBN} considers two Modula-2 variables type equivalent if:
12759 They are of types that have been declared equivalent via a @code{TYPE
12760 @var{t1} = @var{t2}} statement
12763 They have been declared on the same line. (Note: This is true of the
12764 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12767 As long as type checking is enabled, any attempt to combine variables
12768 whose types are not equivalent is an error.
12770 Range checking is done on all mathematical operations, assignment, array
12771 index bounds, and all built-in functions and procedures.
12774 @subsubsection The Scope Operators @code{::} and @code{.}
12776 @cindex @code{.}, Modula-2 scope operator
12777 @cindex colon, doubled as scope operator
12779 @vindex colon-colon@r{, in Modula-2}
12780 @c Info cannot handle :: but TeX can.
12783 @vindex ::@r{, in Modula-2}
12786 There are a few subtle differences between the Modula-2 scope operator
12787 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12792 @var{module} . @var{id}
12793 @var{scope} :: @var{id}
12797 where @var{scope} is the name of a module or a procedure,
12798 @var{module} the name of a module, and @var{id} is any declared
12799 identifier within your program, except another module.
12801 Using the @code{::} operator makes @value{GDBN} search the scope
12802 specified by @var{scope} for the identifier @var{id}. If it is not
12803 found in the specified scope, then @value{GDBN} searches all scopes
12804 enclosing the one specified by @var{scope}.
12806 Using the @code{.} operator makes @value{GDBN} search the current scope for
12807 the identifier specified by @var{id} that was imported from the
12808 definition module specified by @var{module}. With this operator, it is
12809 an error if the identifier @var{id} was not imported from definition
12810 module @var{module}, or if @var{id} is not an identifier in
12814 @subsubsection @value{GDBN} and Modula-2
12816 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12817 Five subcommands of @code{set print} and @code{show print} apply
12818 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12819 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12820 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12821 analogue in Modula-2.
12823 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12824 with any language, is not useful with Modula-2. Its
12825 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12826 created in Modula-2 as they can in C or C@t{++}. However, because an
12827 address can be specified by an integral constant, the construct
12828 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12830 @cindex @code{#} in Modula-2
12831 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12832 interpreted as the beginning of a comment. Use @code{<>} instead.
12838 The extensions made to @value{GDBN} for Ada only support
12839 output from the @sc{gnu} Ada (GNAT) compiler.
12840 Other Ada compilers are not currently supported, and
12841 attempting to debug executables produced by them is most likely
12845 @cindex expressions in Ada
12847 * Ada Mode Intro:: General remarks on the Ada syntax
12848 and semantics supported by Ada mode
12850 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12851 * Additions to Ada:: Extensions of the Ada expression syntax.
12852 * Stopping Before Main Program:: Debugging the program during elaboration.
12853 * Ada Tasks:: Listing and setting breakpoints in tasks.
12854 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12855 * Ada Glitches:: Known peculiarities of Ada mode.
12858 @node Ada Mode Intro
12859 @subsubsection Introduction
12860 @cindex Ada mode, general
12862 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12863 syntax, with some extensions.
12864 The philosophy behind the design of this subset is
12868 That @value{GDBN} should provide basic literals and access to operations for
12869 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12870 leaving more sophisticated computations to subprograms written into the
12871 program (which therefore may be called from @value{GDBN}).
12874 That type safety and strict adherence to Ada language restrictions
12875 are not particularly important to the @value{GDBN} user.
12878 That brevity is important to the @value{GDBN} user.
12881 Thus, for brevity, the debugger acts as if all names declared in
12882 user-written packages are directly visible, even if they are not visible
12883 according to Ada rules, thus making it unnecessary to fully qualify most
12884 names with their packages, regardless of context. Where this causes
12885 ambiguity, @value{GDBN} asks the user's intent.
12887 The debugger will start in Ada mode if it detects an Ada main program.
12888 As for other languages, it will enter Ada mode when stopped in a program that
12889 was translated from an Ada source file.
12891 While in Ada mode, you may use `@t{--}' for comments. This is useful
12892 mostly for documenting command files. The standard @value{GDBN} comment
12893 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12894 middle (to allow based literals).
12896 The debugger supports limited overloading. Given a subprogram call in which
12897 the function symbol has multiple definitions, it will use the number of
12898 actual parameters and some information about their types to attempt to narrow
12899 the set of definitions. It also makes very limited use of context, preferring
12900 procedures to functions in the context of the @code{call} command, and
12901 functions to procedures elsewhere.
12903 @node Omissions from Ada
12904 @subsubsection Omissions from Ada
12905 @cindex Ada, omissions from
12907 Here are the notable omissions from the subset:
12911 Only a subset of the attributes are supported:
12915 @t{'First}, @t{'Last}, and @t{'Length}
12916 on array objects (not on types and subtypes).
12919 @t{'Min} and @t{'Max}.
12922 @t{'Pos} and @t{'Val}.
12928 @t{'Range} on array objects (not subtypes), but only as the right
12929 operand of the membership (@code{in}) operator.
12932 @t{'Access}, @t{'Unchecked_Access}, and
12933 @t{'Unrestricted_Access} (a GNAT extension).
12941 @code{Characters.Latin_1} are not available and
12942 concatenation is not implemented. Thus, escape characters in strings are
12943 not currently available.
12946 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12947 equality of representations. They will generally work correctly
12948 for strings and arrays whose elements have integer or enumeration types.
12949 They may not work correctly for arrays whose element
12950 types have user-defined equality, for arrays of real values
12951 (in particular, IEEE-conformant floating point, because of negative
12952 zeroes and NaNs), and for arrays whose elements contain unused bits with
12953 indeterminate values.
12956 The other component-by-component array operations (@code{and}, @code{or},
12957 @code{xor}, @code{not}, and relational tests other than equality)
12958 are not implemented.
12961 @cindex array aggregates (Ada)
12962 @cindex record aggregates (Ada)
12963 @cindex aggregates (Ada)
12964 There is limited support for array and record aggregates. They are
12965 permitted only on the right sides of assignments, as in these examples:
12968 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12969 (@value{GDBP}) set An_Array := (1, others => 0)
12970 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12971 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12972 (@value{GDBP}) set A_Record := (1, "Peter", True);
12973 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12977 discriminant's value by assigning an aggregate has an
12978 undefined effect if that discriminant is used within the record.
12979 However, you can first modify discriminants by directly assigning to
12980 them (which normally would not be allowed in Ada), and then performing an
12981 aggregate assignment. For example, given a variable @code{A_Rec}
12982 declared to have a type such as:
12985 type Rec (Len : Small_Integer := 0) is record
12987 Vals : IntArray (1 .. Len);
12991 you can assign a value with a different size of @code{Vals} with two
12995 (@value{GDBP}) set A_Rec.Len := 4
12996 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
12999 As this example also illustrates, @value{GDBN} is very loose about the usual
13000 rules concerning aggregates. You may leave out some of the
13001 components of an array or record aggregate (such as the @code{Len}
13002 component in the assignment to @code{A_Rec} above); they will retain their
13003 original values upon assignment. You may freely use dynamic values as
13004 indices in component associations. You may even use overlapping or
13005 redundant component associations, although which component values are
13006 assigned in such cases is not defined.
13009 Calls to dispatching subprograms are not implemented.
13012 The overloading algorithm is much more limited (i.e., less selective)
13013 than that of real Ada. It makes only limited use of the context in
13014 which a subexpression appears to resolve its meaning, and it is much
13015 looser in its rules for allowing type matches. As a result, some
13016 function calls will be ambiguous, and the user will be asked to choose
13017 the proper resolution.
13020 The @code{new} operator is not implemented.
13023 Entry calls are not implemented.
13026 Aside from printing, arithmetic operations on the native VAX floating-point
13027 formats are not supported.
13030 It is not possible to slice a packed array.
13033 The names @code{True} and @code{False}, when not part of a qualified name,
13034 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13036 Should your program
13037 redefine these names in a package or procedure (at best a dubious practice),
13038 you will have to use fully qualified names to access their new definitions.
13041 @node Additions to Ada
13042 @subsubsection Additions to Ada
13043 @cindex Ada, deviations from
13045 As it does for other languages, @value{GDBN} makes certain generic
13046 extensions to Ada (@pxref{Expressions}):
13050 If the expression @var{E} is a variable residing in memory (typically
13051 a local variable or array element) and @var{N} is a positive integer,
13052 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13053 @var{N}-1 adjacent variables following it in memory as an array. In
13054 Ada, this operator is generally not necessary, since its prime use is
13055 in displaying parts of an array, and slicing will usually do this in
13056 Ada. However, there are occasional uses when debugging programs in
13057 which certain debugging information has been optimized away.
13060 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13061 appears in function or file @var{B}.'' When @var{B} is a file name,
13062 you must typically surround it in single quotes.
13065 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13066 @var{type} that appears at address @var{addr}.''
13069 A name starting with @samp{$} is a convenience variable
13070 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13073 In addition, @value{GDBN} provides a few other shortcuts and outright
13074 additions specific to Ada:
13078 The assignment statement is allowed as an expression, returning
13079 its right-hand operand as its value. Thus, you may enter
13082 (@value{GDBP}) set x := y + 3
13083 (@value{GDBP}) print A(tmp := y + 1)
13087 The semicolon is allowed as an ``operator,'' returning as its value
13088 the value of its right-hand operand.
13089 This allows, for example,
13090 complex conditional breaks:
13093 (@value{GDBP}) break f
13094 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13098 Rather than use catenation and symbolic character names to introduce special
13099 characters into strings, one may instead use a special bracket notation,
13100 which is also used to print strings. A sequence of characters of the form
13101 @samp{["@var{XX}"]} within a string or character literal denotes the
13102 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13103 sequence of characters @samp{["""]} also denotes a single quotation mark
13104 in strings. For example,
13106 "One line.["0a"]Next line.["0a"]"
13109 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13113 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13114 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13118 (@value{GDBP}) print 'max(x, y)
13122 When printing arrays, @value{GDBN} uses positional notation when the
13123 array has a lower bound of 1, and uses a modified named notation otherwise.
13124 For example, a one-dimensional array of three integers with a lower bound
13125 of 3 might print as
13132 That is, in contrast to valid Ada, only the first component has a @code{=>}
13136 You may abbreviate attributes in expressions with any unique,
13137 multi-character subsequence of
13138 their names (an exact match gets preference).
13139 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13140 in place of @t{a'length}.
13143 @cindex quoting Ada internal identifiers
13144 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13145 to lower case. The GNAT compiler uses upper-case characters for
13146 some of its internal identifiers, which are normally of no interest to users.
13147 For the rare occasions when you actually have to look at them,
13148 enclose them in angle brackets to avoid the lower-case mapping.
13151 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13155 Printing an object of class-wide type or dereferencing an
13156 access-to-class-wide value will display all the components of the object's
13157 specific type (as indicated by its run-time tag). Likewise, component
13158 selection on such a value will operate on the specific type of the
13163 @node Stopping Before Main Program
13164 @subsubsection Stopping at the Very Beginning
13166 @cindex breakpointing Ada elaboration code
13167 It is sometimes necessary to debug the program during elaboration, and
13168 before reaching the main procedure.
13169 As defined in the Ada Reference
13170 Manual, the elaboration code is invoked from a procedure called
13171 @code{adainit}. To run your program up to the beginning of
13172 elaboration, simply use the following two commands:
13173 @code{tbreak adainit} and @code{run}.
13176 @subsubsection Extensions for Ada Tasks
13177 @cindex Ada, tasking
13179 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13180 @value{GDBN} provides the following task-related commands:
13185 This command shows a list of current Ada tasks, as in the following example:
13192 (@value{GDBP}) info tasks
13193 ID TID P-ID Pri State Name
13194 1 8088000 0 15 Child Activation Wait main_task
13195 2 80a4000 1 15 Accept Statement b
13196 3 809a800 1 15 Child Activation Wait a
13197 * 4 80ae800 3 15 Runnable c
13202 In this listing, the asterisk before the last task indicates it to be the
13203 task currently being inspected.
13207 Represents @value{GDBN}'s internal task number.
13213 The parent's task ID (@value{GDBN}'s internal task number).
13216 The base priority of the task.
13219 Current state of the task.
13223 The task has been created but has not been activated. It cannot be
13227 The task is not blocked for any reason known to Ada. (It may be waiting
13228 for a mutex, though.) It is conceptually "executing" in normal mode.
13231 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13232 that were waiting on terminate alternatives have been awakened and have
13233 terminated themselves.
13235 @item Child Activation Wait
13236 The task is waiting for created tasks to complete activation.
13238 @item Accept Statement
13239 The task is waiting on an accept or selective wait statement.
13241 @item Waiting on entry call
13242 The task is waiting on an entry call.
13244 @item Async Select Wait
13245 The task is waiting to start the abortable part of an asynchronous
13249 The task is waiting on a select statement with only a delay
13252 @item Child Termination Wait
13253 The task is sleeping having completed a master within itself, and is
13254 waiting for the tasks dependent on that master to become terminated or
13255 waiting on a terminate Phase.
13257 @item Wait Child in Term Alt
13258 The task is sleeping waiting for tasks on terminate alternatives to
13259 finish terminating.
13261 @item Accepting RV with @var{taskno}
13262 The task is accepting a rendez-vous with the task @var{taskno}.
13266 Name of the task in the program.
13270 @kindex info task @var{taskno}
13271 @item info task @var{taskno}
13272 This command shows detailled informations on the specified task, as in
13273 the following example:
13278 (@value{GDBP}) info tasks
13279 ID TID P-ID Pri State Name
13280 1 8077880 0 15 Child Activation Wait main_task
13281 * 2 807c468 1 15 Runnable task_1
13282 (@value{GDBP}) info task 2
13283 Ada Task: 0x807c468
13286 Parent: 1 (main_task)
13292 @kindex task@r{ (Ada)}
13293 @cindex current Ada task ID
13294 This command prints the ID of the current task.
13300 (@value{GDBP}) info tasks
13301 ID TID P-ID Pri State Name
13302 1 8077870 0 15 Child Activation Wait main_task
13303 * 2 807c458 1 15 Runnable t
13304 (@value{GDBP}) task
13305 [Current task is 2]
13308 @item task @var{taskno}
13309 @cindex Ada task switching
13310 This command is like the @code{thread @var{threadno}}
13311 command (@pxref{Threads}). It switches the context of debugging
13312 from the current task to the given task.
13318 (@value{GDBP}) info tasks
13319 ID TID P-ID Pri State Name
13320 1 8077870 0 15 Child Activation Wait main_task
13321 * 2 807c458 1 15 Runnable t
13322 (@value{GDBP}) task 1
13323 [Switching to task 1]
13324 #0 0x8067726 in pthread_cond_wait ()
13326 #0 0x8067726 in pthread_cond_wait ()
13327 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13328 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13329 #3 0x806153e in system.tasking.stages.activate_tasks ()
13330 #4 0x804aacc in un () at un.adb:5
13333 @item break @var{linespec} task @var{taskno}
13334 @itemx break @var{linespec} task @var{taskno} if @dots{}
13335 @cindex breakpoints and tasks, in Ada
13336 @cindex task breakpoints, in Ada
13337 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13338 These commands are like the @code{break @dots{} thread @dots{}}
13339 command (@pxref{Thread Stops}).
13340 @var{linespec} specifies source lines, as described
13341 in @ref{Specify Location}.
13343 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13344 to specify that you only want @value{GDBN} to stop the program when a
13345 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13346 numeric task identifiers assigned by @value{GDBN}, shown in the first
13347 column of the @samp{info tasks} display.
13349 If you do not specify @samp{task @var{taskno}} when you set a
13350 breakpoint, the breakpoint applies to @emph{all} tasks of your
13353 You can use the @code{task} qualifier on conditional breakpoints as
13354 well; in this case, place @samp{task @var{taskno}} before the
13355 breakpoint condition (before the @code{if}).
13363 (@value{GDBP}) info tasks
13364 ID TID P-ID Pri State Name
13365 1 140022020 0 15 Child Activation Wait main_task
13366 2 140045060 1 15 Accept/Select Wait t2
13367 3 140044840 1 15 Runnable t1
13368 * 4 140056040 1 15 Runnable t3
13369 (@value{GDBP}) b 15 task 2
13370 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13371 (@value{GDBP}) cont
13376 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13378 (@value{GDBP}) info tasks
13379 ID TID P-ID Pri State Name
13380 1 140022020 0 15 Child Activation Wait main_task
13381 * 2 140045060 1 15 Runnable t2
13382 3 140044840 1 15 Runnable t1
13383 4 140056040 1 15 Delay Sleep t3
13387 @node Ada Tasks and Core Files
13388 @subsubsection Tasking Support when Debugging Core Files
13389 @cindex Ada tasking and core file debugging
13391 When inspecting a core file, as opposed to debugging a live program,
13392 tasking support may be limited or even unavailable, depending on
13393 the platform being used.
13394 For instance, on x86-linux, the list of tasks is available, but task
13395 switching is not supported. On Tru64, however, task switching will work
13398 On certain platforms, including Tru64, the debugger needs to perform some
13399 memory writes in order to provide Ada tasking support. When inspecting
13400 a core file, this means that the core file must be opened with read-write
13401 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13402 Under these circumstances, you should make a backup copy of the core
13403 file before inspecting it with @value{GDBN}.
13406 @subsubsection Known Peculiarities of Ada Mode
13407 @cindex Ada, problems
13409 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13410 we know of several problems with and limitations of Ada mode in
13412 some of which will be fixed with planned future releases of the debugger
13413 and the GNU Ada compiler.
13417 Currently, the debugger
13418 has insufficient information to determine whether certain pointers represent
13419 pointers to objects or the objects themselves.
13420 Thus, the user may have to tack an extra @code{.all} after an expression
13421 to get it printed properly.
13424 Static constants that the compiler chooses not to materialize as objects in
13425 storage are invisible to the debugger.
13428 Named parameter associations in function argument lists are ignored (the
13429 argument lists are treated as positional).
13432 Many useful library packages are currently invisible to the debugger.
13435 Fixed-point arithmetic, conversions, input, and output is carried out using
13436 floating-point arithmetic, and may give results that only approximate those on
13440 The GNAT compiler never generates the prefix @code{Standard} for any of
13441 the standard symbols defined by the Ada language. @value{GDBN} knows about
13442 this: it will strip the prefix from names when you use it, and will never
13443 look for a name you have so qualified among local symbols, nor match against
13444 symbols in other packages or subprograms. If you have
13445 defined entities anywhere in your program other than parameters and
13446 local variables whose simple names match names in @code{Standard},
13447 GNAT's lack of qualification here can cause confusion. When this happens,
13448 you can usually resolve the confusion
13449 by qualifying the problematic names with package
13450 @code{Standard} explicitly.
13453 Older versions of the compiler sometimes generate erroneous debugging
13454 information, resulting in the debugger incorrectly printing the value
13455 of affected entities. In some cases, the debugger is able to work
13456 around an issue automatically. In other cases, the debugger is able
13457 to work around the issue, but the work-around has to be specifically
13460 @kindex set ada trust-PAD-over-XVS
13461 @kindex show ada trust-PAD-over-XVS
13464 @item set ada trust-PAD-over-XVS on
13465 Configure GDB to strictly follow the GNAT encoding when computing the
13466 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13467 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13468 a complete description of the encoding used by the GNAT compiler).
13469 This is the default.
13471 @item set ada trust-PAD-over-XVS off
13472 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13473 sometimes prints the wrong value for certain entities, changing @code{ada
13474 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13475 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13476 @code{off}, but this incurs a slight performance penalty, so it is
13477 recommended to leave this setting to @code{on} unless necessary.
13481 @node Unsupported Languages
13482 @section Unsupported Languages
13484 @cindex unsupported languages
13485 @cindex minimal language
13486 In addition to the other fully-supported programming languages,
13487 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13488 It does not represent a real programming language, but provides a set
13489 of capabilities close to what the C or assembly languages provide.
13490 This should allow most simple operations to be performed while debugging
13491 an application that uses a language currently not supported by @value{GDBN}.
13493 If the language is set to @code{auto}, @value{GDBN} will automatically
13494 select this language if the current frame corresponds to an unsupported
13498 @chapter Examining the Symbol Table
13500 The commands described in this chapter allow you to inquire about the
13501 symbols (names of variables, functions and types) defined in your
13502 program. This information is inherent in the text of your program and
13503 does not change as your program executes. @value{GDBN} finds it in your
13504 program's symbol table, in the file indicated when you started @value{GDBN}
13505 (@pxref{File Options, ,Choosing Files}), or by one of the
13506 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13508 @cindex symbol names
13509 @cindex names of symbols
13510 @cindex quoting names
13511 Occasionally, you may need to refer to symbols that contain unusual
13512 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13513 most frequent case is in referring to static variables in other
13514 source files (@pxref{Variables,,Program Variables}). File names
13515 are recorded in object files as debugging symbols, but @value{GDBN} would
13516 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13517 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13518 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13525 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13528 @cindex case-insensitive symbol names
13529 @cindex case sensitivity in symbol names
13530 @kindex set case-sensitive
13531 @item set case-sensitive on
13532 @itemx set case-sensitive off
13533 @itemx set case-sensitive auto
13534 Normally, when @value{GDBN} looks up symbols, it matches their names
13535 with case sensitivity determined by the current source language.
13536 Occasionally, you may wish to control that. The command @code{set
13537 case-sensitive} lets you do that by specifying @code{on} for
13538 case-sensitive matches or @code{off} for case-insensitive ones. If
13539 you specify @code{auto}, case sensitivity is reset to the default
13540 suitable for the source language. The default is case-sensitive
13541 matches for all languages except for Fortran, for which the default is
13542 case-insensitive matches.
13544 @kindex show case-sensitive
13545 @item show case-sensitive
13546 This command shows the current setting of case sensitivity for symbols
13549 @kindex info address
13550 @cindex address of a symbol
13551 @item info address @var{symbol}
13552 Describe where the data for @var{symbol} is stored. For a register
13553 variable, this says which register it is kept in. For a non-register
13554 local variable, this prints the stack-frame offset at which the variable
13557 Note the contrast with @samp{print &@var{symbol}}, which does not work
13558 at all for a register variable, and for a stack local variable prints
13559 the exact address of the current instantiation of the variable.
13561 @kindex info symbol
13562 @cindex symbol from address
13563 @cindex closest symbol and offset for an address
13564 @item info symbol @var{addr}
13565 Print the name of a symbol which is stored at the address @var{addr}.
13566 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13567 nearest symbol and an offset from it:
13570 (@value{GDBP}) info symbol 0x54320
13571 _initialize_vx + 396 in section .text
13575 This is the opposite of the @code{info address} command. You can use
13576 it to find out the name of a variable or a function given its address.
13578 For dynamically linked executables, the name of executable or shared
13579 library containing the symbol is also printed:
13582 (@value{GDBP}) info symbol 0x400225
13583 _start + 5 in section .text of /tmp/a.out
13584 (@value{GDBP}) info symbol 0x2aaaac2811cf
13585 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13589 @item whatis [@var{arg}]
13590 Print the data type of @var{arg}, which can be either an expression or
13591 a data type. With no argument, print the data type of @code{$}, the
13592 last value in the value history. If @var{arg} is an expression, it is
13593 not actually evaluated, and any side-effecting operations (such as
13594 assignments or function calls) inside it do not take place. If
13595 @var{arg} is a type name, it may be the name of a type or typedef, or
13596 for C code it may have the form @samp{class @var{class-name}},
13597 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13598 @samp{enum @var{enum-tag}}.
13599 @xref{Expressions, ,Expressions}.
13602 @item ptype [@var{arg}]
13603 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13604 detailed description of the type, instead of just the name of the type.
13605 @xref{Expressions, ,Expressions}.
13607 For example, for this variable declaration:
13610 struct complex @{double real; double imag;@} v;
13614 the two commands give this output:
13618 (@value{GDBP}) whatis v
13619 type = struct complex
13620 (@value{GDBP}) ptype v
13621 type = struct complex @{
13629 As with @code{whatis}, using @code{ptype} without an argument refers to
13630 the type of @code{$}, the last value in the value history.
13632 @cindex incomplete type
13633 Sometimes, programs use opaque data types or incomplete specifications
13634 of complex data structure. If the debug information included in the
13635 program does not allow @value{GDBN} to display a full declaration of
13636 the data type, it will say @samp{<incomplete type>}. For example,
13637 given these declarations:
13641 struct foo *fooptr;
13645 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13648 (@value{GDBP}) ptype foo
13649 $1 = <incomplete type>
13653 ``Incomplete type'' is C terminology for data types that are not
13654 completely specified.
13657 @item info types @var{regexp}
13659 Print a brief description of all types whose names match the regular
13660 expression @var{regexp} (or all types in your program, if you supply
13661 no argument). Each complete typename is matched as though it were a
13662 complete line; thus, @samp{i type value} gives information on all
13663 types in your program whose names include the string @code{value}, but
13664 @samp{i type ^value$} gives information only on types whose complete
13665 name is @code{value}.
13667 This command differs from @code{ptype} in two ways: first, like
13668 @code{whatis}, it does not print a detailed description; second, it
13669 lists all source files where a type is defined.
13672 @cindex local variables
13673 @item info scope @var{location}
13674 List all the variables local to a particular scope. This command
13675 accepts a @var{location} argument---a function name, a source line, or
13676 an address preceded by a @samp{*}, and prints all the variables local
13677 to the scope defined by that location. (@xref{Specify Location}, for
13678 details about supported forms of @var{location}.) For example:
13681 (@value{GDBP}) @b{info scope command_line_handler}
13682 Scope for command_line_handler:
13683 Symbol rl is an argument at stack/frame offset 8, length 4.
13684 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13685 Symbol linelength is in static storage at address 0x150a1c, length 4.
13686 Symbol p is a local variable in register $esi, length 4.
13687 Symbol p1 is a local variable in register $ebx, length 4.
13688 Symbol nline is a local variable in register $edx, length 4.
13689 Symbol repeat is a local variable at frame offset -8, length 4.
13693 This command is especially useful for determining what data to collect
13694 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13697 @kindex info source
13699 Show information about the current source file---that is, the source file for
13700 the function containing the current point of execution:
13703 the name of the source file, and the directory containing it,
13705 the directory it was compiled in,
13707 its length, in lines,
13709 which programming language it is written in,
13711 whether the executable includes debugging information for that file, and
13712 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13714 whether the debugging information includes information about
13715 preprocessor macros.
13719 @kindex info sources
13721 Print the names of all source files in your program for which there is
13722 debugging information, organized into two lists: files whose symbols
13723 have already been read, and files whose symbols will be read when needed.
13725 @kindex info functions
13726 @item info functions
13727 Print the names and data types of all defined functions.
13729 @item info functions @var{regexp}
13730 Print the names and data types of all defined functions
13731 whose names contain a match for regular expression @var{regexp}.
13732 Thus, @samp{info fun step} finds all functions whose names
13733 include @code{step}; @samp{info fun ^step} finds those whose names
13734 start with @code{step}. If a function name contains characters
13735 that conflict with the regular expression language (e.g.@:
13736 @samp{operator*()}), they may be quoted with a backslash.
13738 @kindex info variables
13739 @item info variables
13740 Print the names and data types of all variables that are defined
13741 outside of functions (i.e.@: excluding local variables).
13743 @item info variables @var{regexp}
13744 Print the names and data types of all variables (except for local
13745 variables) whose names contain a match for regular expression
13748 @kindex info classes
13749 @cindex Objective-C, classes and selectors
13751 @itemx info classes @var{regexp}
13752 Display all Objective-C classes in your program, or
13753 (with the @var{regexp} argument) all those matching a particular regular
13756 @kindex info selectors
13757 @item info selectors
13758 @itemx info selectors @var{regexp}
13759 Display all Objective-C selectors in your program, or
13760 (with the @var{regexp} argument) all those matching a particular regular
13764 This was never implemented.
13765 @kindex info methods
13767 @itemx info methods @var{regexp}
13768 The @code{info methods} command permits the user to examine all defined
13769 methods within C@t{++} program, or (with the @var{regexp} argument) a
13770 specific set of methods found in the various C@t{++} classes. Many
13771 C@t{++} classes provide a large number of methods. Thus, the output
13772 from the @code{ptype} command can be overwhelming and hard to use. The
13773 @code{info-methods} command filters the methods, printing only those
13774 which match the regular-expression @var{regexp}.
13777 @cindex reloading symbols
13778 Some systems allow individual object files that make up your program to
13779 be replaced without stopping and restarting your program. For example,
13780 in VxWorks you can simply recompile a defective object file and keep on
13781 running. If you are running on one of these systems, you can allow
13782 @value{GDBN} to reload the symbols for automatically relinked modules:
13785 @kindex set symbol-reloading
13786 @item set symbol-reloading on
13787 Replace symbol definitions for the corresponding source file when an
13788 object file with a particular name is seen again.
13790 @item set symbol-reloading off
13791 Do not replace symbol definitions when encountering object files of the
13792 same name more than once. This is the default state; if you are not
13793 running on a system that permits automatic relinking of modules, you
13794 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13795 may discard symbols when linking large programs, that may contain
13796 several modules (from different directories or libraries) with the same
13799 @kindex show symbol-reloading
13800 @item show symbol-reloading
13801 Show the current @code{on} or @code{off} setting.
13804 @cindex opaque data types
13805 @kindex set opaque-type-resolution
13806 @item set opaque-type-resolution on
13807 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13808 declared as a pointer to a @code{struct}, @code{class}, or
13809 @code{union}---for example, @code{struct MyType *}---that is used in one
13810 source file although the full declaration of @code{struct MyType} is in
13811 another source file. The default is on.
13813 A change in the setting of this subcommand will not take effect until
13814 the next time symbols for a file are loaded.
13816 @item set opaque-type-resolution off
13817 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13818 is printed as follows:
13820 @{<no data fields>@}
13823 @kindex show opaque-type-resolution
13824 @item show opaque-type-resolution
13825 Show whether opaque types are resolved or not.
13827 @kindex maint print symbols
13828 @cindex symbol dump
13829 @kindex maint print psymbols
13830 @cindex partial symbol dump
13831 @item maint print symbols @var{filename}
13832 @itemx maint print psymbols @var{filename}
13833 @itemx maint print msymbols @var{filename}
13834 Write a dump of debugging symbol data into the file @var{filename}.
13835 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13836 symbols with debugging data are included. If you use @samp{maint print
13837 symbols}, @value{GDBN} includes all the symbols for which it has already
13838 collected full details: that is, @var{filename} reflects symbols for
13839 only those files whose symbols @value{GDBN} has read. You can use the
13840 command @code{info sources} to find out which files these are. If you
13841 use @samp{maint print psymbols} instead, the dump shows information about
13842 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13843 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13844 @samp{maint print msymbols} dumps just the minimal symbol information
13845 required for each object file from which @value{GDBN} has read some symbols.
13846 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13847 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13849 @kindex maint info symtabs
13850 @kindex maint info psymtabs
13851 @cindex listing @value{GDBN}'s internal symbol tables
13852 @cindex symbol tables, listing @value{GDBN}'s internal
13853 @cindex full symbol tables, listing @value{GDBN}'s internal
13854 @cindex partial symbol tables, listing @value{GDBN}'s internal
13855 @item maint info symtabs @r{[} @var{regexp} @r{]}
13856 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13858 List the @code{struct symtab} or @code{struct partial_symtab}
13859 structures whose names match @var{regexp}. If @var{regexp} is not
13860 given, list them all. The output includes expressions which you can
13861 copy into a @value{GDBN} debugging this one to examine a particular
13862 structure in more detail. For example:
13865 (@value{GDBP}) maint info psymtabs dwarf2read
13866 @{ objfile /home/gnu/build/gdb/gdb
13867 ((struct objfile *) 0x82e69d0)
13868 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13869 ((struct partial_symtab *) 0x8474b10)
13872 text addresses 0x814d3c8 -- 0x8158074
13873 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13874 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13875 dependencies (none)
13878 (@value{GDBP}) maint info symtabs
13882 We see that there is one partial symbol table whose filename contains
13883 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13884 and we see that @value{GDBN} has not read in any symtabs yet at all.
13885 If we set a breakpoint on a function, that will cause @value{GDBN} to
13886 read the symtab for the compilation unit containing that function:
13889 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13890 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13892 (@value{GDBP}) maint info symtabs
13893 @{ objfile /home/gnu/build/gdb/gdb
13894 ((struct objfile *) 0x82e69d0)
13895 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13896 ((struct symtab *) 0x86c1f38)
13899 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13900 linetable ((struct linetable *) 0x8370fa0)
13901 debugformat DWARF 2
13910 @chapter Altering Execution
13912 Once you think you have found an error in your program, you might want to
13913 find out for certain whether correcting the apparent error would lead to
13914 correct results in the rest of the run. You can find the answer by
13915 experiment, using the @value{GDBN} features for altering execution of the
13918 For example, you can store new values into variables or memory
13919 locations, give your program a signal, restart it at a different
13920 address, or even return prematurely from a function.
13923 * Assignment:: Assignment to variables
13924 * Jumping:: Continuing at a different address
13925 * Signaling:: Giving your program a signal
13926 * Returning:: Returning from a function
13927 * Calling:: Calling your program's functions
13928 * Patching:: Patching your program
13932 @section Assignment to Variables
13935 @cindex setting variables
13936 To alter the value of a variable, evaluate an assignment expression.
13937 @xref{Expressions, ,Expressions}. For example,
13944 stores the value 4 into the variable @code{x}, and then prints the
13945 value of the assignment expression (which is 4).
13946 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13947 information on operators in supported languages.
13949 @kindex set variable
13950 @cindex variables, setting
13951 If you are not interested in seeing the value of the assignment, use the
13952 @code{set} command instead of the @code{print} command. @code{set} is
13953 really the same as @code{print} except that the expression's value is
13954 not printed and is not put in the value history (@pxref{Value History,
13955 ,Value History}). The expression is evaluated only for its effects.
13957 If the beginning of the argument string of the @code{set} command
13958 appears identical to a @code{set} subcommand, use the @code{set
13959 variable} command instead of just @code{set}. This command is identical
13960 to @code{set} except for its lack of subcommands. For example, if your
13961 program has a variable @code{width}, you get an error if you try to set
13962 a new value with just @samp{set width=13}, because @value{GDBN} has the
13963 command @code{set width}:
13966 (@value{GDBP}) whatis width
13968 (@value{GDBP}) p width
13970 (@value{GDBP}) set width=47
13971 Invalid syntax in expression.
13975 The invalid expression, of course, is @samp{=47}. In
13976 order to actually set the program's variable @code{width}, use
13979 (@value{GDBP}) set var width=47
13982 Because the @code{set} command has many subcommands that can conflict
13983 with the names of program variables, it is a good idea to use the
13984 @code{set variable} command instead of just @code{set}. For example, if
13985 your program has a variable @code{g}, you run into problems if you try
13986 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13987 the command @code{set gnutarget}, abbreviated @code{set g}:
13991 (@value{GDBP}) whatis g
13995 (@value{GDBP}) set g=4
13999 The program being debugged has been started already.
14000 Start it from the beginning? (y or n) y
14001 Starting program: /home/smith/cc_progs/a.out
14002 "/home/smith/cc_progs/a.out": can't open to read symbols:
14003 Invalid bfd target.
14004 (@value{GDBP}) show g
14005 The current BFD target is "=4".
14010 The program variable @code{g} did not change, and you silently set the
14011 @code{gnutarget} to an invalid value. In order to set the variable
14015 (@value{GDBP}) set var g=4
14018 @value{GDBN} allows more implicit conversions in assignments than C; you can
14019 freely store an integer value into a pointer variable or vice versa,
14020 and you can convert any structure to any other structure that is the
14021 same length or shorter.
14022 @comment FIXME: how do structs align/pad in these conversions?
14023 @comment /doc@cygnus.com 18dec1990
14025 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14026 construct to generate a value of specified type at a specified address
14027 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14028 to memory location @code{0x83040} as an integer (which implies a certain size
14029 and representation in memory), and
14032 set @{int@}0x83040 = 4
14036 stores the value 4 into that memory location.
14039 @section Continuing at a Different Address
14041 Ordinarily, when you continue your program, you do so at the place where
14042 it stopped, with the @code{continue} command. You can instead continue at
14043 an address of your own choosing, with the following commands:
14047 @item jump @var{linespec}
14048 @itemx jump @var{location}
14049 Resume execution at line @var{linespec} or at address given by
14050 @var{location}. Execution stops again immediately if there is a
14051 breakpoint there. @xref{Specify Location}, for a description of the
14052 different forms of @var{linespec} and @var{location}. It is common
14053 practice to use the @code{tbreak} command in conjunction with
14054 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14056 The @code{jump} command does not change the current stack frame, or
14057 the stack pointer, or the contents of any memory location or any
14058 register other than the program counter. If line @var{linespec} is in
14059 a different function from the one currently executing, the results may
14060 be bizarre if the two functions expect different patterns of arguments or
14061 of local variables. For this reason, the @code{jump} command requests
14062 confirmation if the specified line is not in the function currently
14063 executing. However, even bizarre results are predictable if you are
14064 well acquainted with the machine-language code of your program.
14067 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14068 On many systems, you can get much the same effect as the @code{jump}
14069 command by storing a new value into the register @code{$pc}. The
14070 difference is that this does not start your program running; it only
14071 changes the address of where it @emph{will} run when you continue. For
14079 makes the next @code{continue} command or stepping command execute at
14080 address @code{0x485}, rather than at the address where your program stopped.
14081 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14083 The most common occasion to use the @code{jump} command is to back
14084 up---perhaps with more breakpoints set---over a portion of a program
14085 that has already executed, in order to examine its execution in more
14090 @section Giving your Program a Signal
14091 @cindex deliver a signal to a program
14095 @item signal @var{signal}
14096 Resume execution where your program stopped, but immediately give it the
14097 signal @var{signal}. @var{signal} can be the name or the number of a
14098 signal. For example, on many systems @code{signal 2} and @code{signal
14099 SIGINT} are both ways of sending an interrupt signal.
14101 Alternatively, if @var{signal} is zero, continue execution without
14102 giving a signal. This is useful when your program stopped on account of
14103 a signal and would ordinary see the signal when resumed with the
14104 @code{continue} command; @samp{signal 0} causes it to resume without a
14107 @code{signal} does not repeat when you press @key{RET} a second time
14108 after executing the command.
14112 Invoking the @code{signal} command is not the same as invoking the
14113 @code{kill} utility from the shell. Sending a signal with @code{kill}
14114 causes @value{GDBN} to decide what to do with the signal depending on
14115 the signal handling tables (@pxref{Signals}). The @code{signal} command
14116 passes the signal directly to your program.
14120 @section Returning from a Function
14123 @cindex returning from a function
14126 @itemx return @var{expression}
14127 You can cancel execution of a function call with the @code{return}
14128 command. If you give an
14129 @var{expression} argument, its value is used as the function's return
14133 When you use @code{return}, @value{GDBN} discards the selected stack frame
14134 (and all frames within it). You can think of this as making the
14135 discarded frame return prematurely. If you wish to specify a value to
14136 be returned, give that value as the argument to @code{return}.
14138 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14139 Frame}), and any other frames inside of it, leaving its caller as the
14140 innermost remaining frame. That frame becomes selected. The
14141 specified value is stored in the registers used for returning values
14144 The @code{return} command does not resume execution; it leaves the
14145 program stopped in the state that would exist if the function had just
14146 returned. In contrast, the @code{finish} command (@pxref{Continuing
14147 and Stepping, ,Continuing and Stepping}) resumes execution until the
14148 selected stack frame returns naturally.
14150 @value{GDBN} needs to know how the @var{expression} argument should be set for
14151 the inferior. The concrete registers assignment depends on the OS ABI and the
14152 type being returned by the selected stack frame. For example it is common for
14153 OS ABI to return floating point values in FPU registers while integer values in
14154 CPU registers. Still some ABIs return even floating point values in CPU
14155 registers. Larger integer widths (such as @code{long long int}) also have
14156 specific placement rules. @value{GDBN} already knows the OS ABI from its
14157 current target so it needs to find out also the type being returned to make the
14158 assignment into the right register(s).
14160 Normally, the selected stack frame has debug info. @value{GDBN} will always
14161 use the debug info instead of the implicit type of @var{expression} when the
14162 debug info is available. For example, if you type @kbd{return -1}, and the
14163 function in the current stack frame is declared to return a @code{long long
14164 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14165 into a @code{long long int}:
14168 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14170 (@value{GDBP}) return -1
14171 Make func return now? (y or n) y
14172 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14173 43 printf ("result=%lld\n", func ());
14177 However, if the selected stack frame does not have a debug info, e.g., if the
14178 function was compiled without debug info, @value{GDBN} has to find out the type
14179 to return from user. Specifying a different type by mistake may set the value
14180 in different inferior registers than the caller code expects. For example,
14181 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14182 of a @code{long long int} result for a debug info less function (on 32-bit
14183 architectures). Therefore the user is required to specify the return type by
14184 an appropriate cast explicitly:
14187 Breakpoint 2, 0x0040050b in func ()
14188 (@value{GDBP}) return -1
14189 Return value type not available for selected stack frame.
14190 Please use an explicit cast of the value to return.
14191 (@value{GDBP}) return (long long int) -1
14192 Make selected stack frame return now? (y or n) y
14193 #0 0x00400526 in main ()
14198 @section Calling Program Functions
14201 @cindex calling functions
14202 @cindex inferior functions, calling
14203 @item print @var{expr}
14204 Evaluate the expression @var{expr} and display the resulting value.
14205 @var{expr} may include calls to functions in the program being
14209 @item call @var{expr}
14210 Evaluate the expression @var{expr} without displaying @code{void}
14213 You can use this variant of the @code{print} command if you want to
14214 execute a function from your program that does not return anything
14215 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14216 with @code{void} returned values that @value{GDBN} will otherwise
14217 print. If the result is not void, it is printed and saved in the
14221 It is possible for the function you call via the @code{print} or
14222 @code{call} command to generate a signal (e.g., if there's a bug in
14223 the function, or if you passed it incorrect arguments). What happens
14224 in that case is controlled by the @code{set unwindonsignal} command.
14226 Similarly, with a C@t{++} program it is possible for the function you
14227 call via the @code{print} or @code{call} command to generate an
14228 exception that is not handled due to the constraints of the dummy
14229 frame. In this case, any exception that is raised in the frame, but has
14230 an out-of-frame exception handler will not be found. GDB builds a
14231 dummy-frame for the inferior function call, and the unwinder cannot
14232 seek for exception handlers outside of this dummy-frame. What happens
14233 in that case is controlled by the
14234 @code{set unwind-on-terminating-exception} command.
14237 @item set unwindonsignal
14238 @kindex set unwindonsignal
14239 @cindex unwind stack in called functions
14240 @cindex call dummy stack unwinding
14241 Set unwinding of the stack if a signal is received while in a function
14242 that @value{GDBN} called in the program being debugged. If set to on,
14243 @value{GDBN} unwinds the stack it created for the call and restores
14244 the context to what it was before the call. If set to off (the
14245 default), @value{GDBN} stops in the frame where the signal was
14248 @item show unwindonsignal
14249 @kindex show unwindonsignal
14250 Show the current setting of stack unwinding in the functions called by
14253 @item set unwind-on-terminating-exception
14254 @kindex set unwind-on-terminating-exception
14255 @cindex unwind stack in called functions with unhandled exceptions
14256 @cindex call dummy stack unwinding on unhandled exception.
14257 Set unwinding of the stack if a C@t{++} exception is raised, but left
14258 unhandled while in a function that @value{GDBN} called in the program being
14259 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14260 it created for the call and restores the context to what it was before
14261 the call. If set to off, @value{GDBN} the exception is delivered to
14262 the default C@t{++} exception handler and the inferior terminated.
14264 @item show unwind-on-terminating-exception
14265 @kindex show unwind-on-terminating-exception
14266 Show the current setting of stack unwinding in the functions called by
14271 @cindex weak alias functions
14272 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14273 for another function. In such case, @value{GDBN} might not pick up
14274 the type information, including the types of the function arguments,
14275 which causes @value{GDBN} to call the inferior function incorrectly.
14276 As a result, the called function will function erroneously and may
14277 even crash. A solution to that is to use the name of the aliased
14281 @section Patching Programs
14283 @cindex patching binaries
14284 @cindex writing into executables
14285 @cindex writing into corefiles
14287 By default, @value{GDBN} opens the file containing your program's
14288 executable code (or the corefile) read-only. This prevents accidental
14289 alterations to machine code; but it also prevents you from intentionally
14290 patching your program's binary.
14292 If you'd like to be able to patch the binary, you can specify that
14293 explicitly with the @code{set write} command. For example, you might
14294 want to turn on internal debugging flags, or even to make emergency
14300 @itemx set write off
14301 If you specify @samp{set write on}, @value{GDBN} opens executable and
14302 core files for both reading and writing; if you specify @kbd{set write
14303 off} (the default), @value{GDBN} opens them read-only.
14305 If you have already loaded a file, you must load it again (using the
14306 @code{exec-file} or @code{core-file} command) after changing @code{set
14307 write}, for your new setting to take effect.
14311 Display whether executable files and core files are opened for writing
14312 as well as reading.
14316 @chapter @value{GDBN} Files
14318 @value{GDBN} needs to know the file name of the program to be debugged,
14319 both in order to read its symbol table and in order to start your
14320 program. To debug a core dump of a previous run, you must also tell
14321 @value{GDBN} the name of the core dump file.
14324 * Files:: Commands to specify files
14325 * Separate Debug Files:: Debugging information in separate files
14326 * Index Files:: Index files speed up GDB
14327 * Symbol Errors:: Errors reading symbol files
14328 * Data Files:: GDB data files
14332 @section Commands to Specify Files
14334 @cindex symbol table
14335 @cindex core dump file
14337 You may want to specify executable and core dump file names. The usual
14338 way to do this is at start-up time, using the arguments to
14339 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14340 Out of @value{GDBN}}).
14342 Occasionally it is necessary to change to a different file during a
14343 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14344 specify a file you want to use. Or you are debugging a remote target
14345 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14346 Program}). In these situations the @value{GDBN} commands to specify
14347 new files are useful.
14350 @cindex executable file
14352 @item file @var{filename}
14353 Use @var{filename} as the program to be debugged. It is read for its
14354 symbols and for the contents of pure memory. It is also the program
14355 executed when you use the @code{run} command. If you do not specify a
14356 directory and the file is not found in the @value{GDBN} working directory,
14357 @value{GDBN} uses the environment variable @code{PATH} as a list of
14358 directories to search, just as the shell does when looking for a program
14359 to run. You can change the value of this variable, for both @value{GDBN}
14360 and your program, using the @code{path} command.
14362 @cindex unlinked object files
14363 @cindex patching object files
14364 You can load unlinked object @file{.o} files into @value{GDBN} using
14365 the @code{file} command. You will not be able to ``run'' an object
14366 file, but you can disassemble functions and inspect variables. Also,
14367 if the underlying BFD functionality supports it, you could use
14368 @kbd{gdb -write} to patch object files using this technique. Note
14369 that @value{GDBN} can neither interpret nor modify relocations in this
14370 case, so branches and some initialized variables will appear to go to
14371 the wrong place. But this feature is still handy from time to time.
14374 @code{file} with no argument makes @value{GDBN} discard any information it
14375 has on both executable file and the symbol table.
14378 @item exec-file @r{[} @var{filename} @r{]}
14379 Specify that the program to be run (but not the symbol table) is found
14380 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14381 if necessary to locate your program. Omitting @var{filename} means to
14382 discard information on the executable file.
14384 @kindex symbol-file
14385 @item symbol-file @r{[} @var{filename} @r{]}
14386 Read symbol table information from file @var{filename}. @code{PATH} is
14387 searched when necessary. Use the @code{file} command to get both symbol
14388 table and program to run from the same file.
14390 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14391 program's symbol table.
14393 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14394 some breakpoints and auto-display expressions. This is because they may
14395 contain pointers to the internal data recording symbols and data types,
14396 which are part of the old symbol table data being discarded inside
14399 @code{symbol-file} does not repeat if you press @key{RET} again after
14402 When @value{GDBN} is configured for a particular environment, it
14403 understands debugging information in whatever format is the standard
14404 generated for that environment; you may use either a @sc{gnu} compiler, or
14405 other compilers that adhere to the local conventions.
14406 Best results are usually obtained from @sc{gnu} compilers; for example,
14407 using @code{@value{NGCC}} you can generate debugging information for
14410 For most kinds of object files, with the exception of old SVR3 systems
14411 using COFF, the @code{symbol-file} command does not normally read the
14412 symbol table in full right away. Instead, it scans the symbol table
14413 quickly to find which source files and which symbols are present. The
14414 details are read later, one source file at a time, as they are needed.
14416 The purpose of this two-stage reading strategy is to make @value{GDBN}
14417 start up faster. For the most part, it is invisible except for
14418 occasional pauses while the symbol table details for a particular source
14419 file are being read. (The @code{set verbose} command can turn these
14420 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14421 Warnings and Messages}.)
14423 We have not implemented the two-stage strategy for COFF yet. When the
14424 symbol table is stored in COFF format, @code{symbol-file} reads the
14425 symbol table data in full right away. Note that ``stabs-in-COFF''
14426 still does the two-stage strategy, since the debug info is actually
14430 @cindex reading symbols immediately
14431 @cindex symbols, reading immediately
14432 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14433 @itemx file @r{[} -readnow @r{]} @var{filename}
14434 You can override the @value{GDBN} two-stage strategy for reading symbol
14435 tables by using the @samp{-readnow} option with any of the commands that
14436 load symbol table information, if you want to be sure @value{GDBN} has the
14437 entire symbol table available.
14439 @c FIXME: for now no mention of directories, since this seems to be in
14440 @c flux. 13mar1992 status is that in theory GDB would look either in
14441 @c current dir or in same dir as myprog; but issues like competing
14442 @c GDB's, or clutter in system dirs, mean that in practice right now
14443 @c only current dir is used. FFish says maybe a special GDB hierarchy
14444 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14448 @item core-file @r{[}@var{filename}@r{]}
14450 Specify the whereabouts of a core dump file to be used as the ``contents
14451 of memory''. Traditionally, core files contain only some parts of the
14452 address space of the process that generated them; @value{GDBN} can access the
14453 executable file itself for other parts.
14455 @code{core-file} with no argument specifies that no core file is
14458 Note that the core file is ignored when your program is actually running
14459 under @value{GDBN}. So, if you have been running your program and you
14460 wish to debug a core file instead, you must kill the subprocess in which
14461 the program is running. To do this, use the @code{kill} command
14462 (@pxref{Kill Process, ,Killing the Child Process}).
14464 @kindex add-symbol-file
14465 @cindex dynamic linking
14466 @item add-symbol-file @var{filename} @var{address}
14467 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14468 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14469 The @code{add-symbol-file} command reads additional symbol table
14470 information from the file @var{filename}. You would use this command
14471 when @var{filename} has been dynamically loaded (by some other means)
14472 into the program that is running. @var{address} should be the memory
14473 address at which the file has been loaded; @value{GDBN} cannot figure
14474 this out for itself. You can additionally specify an arbitrary number
14475 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14476 section name and base address for that section. You can specify any
14477 @var{address} as an expression.
14479 The symbol table of the file @var{filename} is added to the symbol table
14480 originally read with the @code{symbol-file} command. You can use the
14481 @code{add-symbol-file} command any number of times; the new symbol data
14482 thus read keeps adding to the old. To discard all old symbol data
14483 instead, use the @code{symbol-file} command without any arguments.
14485 @cindex relocatable object files, reading symbols from
14486 @cindex object files, relocatable, reading symbols from
14487 @cindex reading symbols from relocatable object files
14488 @cindex symbols, reading from relocatable object files
14489 @cindex @file{.o} files, reading symbols from
14490 Although @var{filename} is typically a shared library file, an
14491 executable file, or some other object file which has been fully
14492 relocated for loading into a process, you can also load symbolic
14493 information from relocatable @file{.o} files, as long as:
14497 the file's symbolic information refers only to linker symbols defined in
14498 that file, not to symbols defined by other object files,
14500 every section the file's symbolic information refers to has actually
14501 been loaded into the inferior, as it appears in the file, and
14503 you can determine the address at which every section was loaded, and
14504 provide these to the @code{add-symbol-file} command.
14508 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14509 relocatable files into an already running program; such systems
14510 typically make the requirements above easy to meet. However, it's
14511 important to recognize that many native systems use complex link
14512 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14513 assembly, for example) that make the requirements difficult to meet. In
14514 general, one cannot assume that using @code{add-symbol-file} to read a
14515 relocatable object file's symbolic information will have the same effect
14516 as linking the relocatable object file into the program in the normal
14519 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14521 @kindex add-symbol-file-from-memory
14522 @cindex @code{syscall DSO}
14523 @cindex load symbols from memory
14524 @item add-symbol-file-from-memory @var{address}
14525 Load symbols from the given @var{address} in a dynamically loaded
14526 object file whose image is mapped directly into the inferior's memory.
14527 For example, the Linux kernel maps a @code{syscall DSO} into each
14528 process's address space; this DSO provides kernel-specific code for
14529 some system calls. The argument can be any expression whose
14530 evaluation yields the address of the file's shared object file header.
14531 For this command to work, you must have used @code{symbol-file} or
14532 @code{exec-file} commands in advance.
14534 @kindex add-shared-symbol-files
14536 @item add-shared-symbol-files @var{library-file}
14537 @itemx assf @var{library-file}
14538 The @code{add-shared-symbol-files} command can currently be used only
14539 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14540 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14541 @value{GDBN} automatically looks for shared libraries, however if
14542 @value{GDBN} does not find yours, you can invoke
14543 @code{add-shared-symbol-files}. It takes one argument: the shared
14544 library's file name. @code{assf} is a shorthand alias for
14545 @code{add-shared-symbol-files}.
14548 @item section @var{section} @var{addr}
14549 The @code{section} command changes the base address of the named
14550 @var{section} of the exec file to @var{addr}. This can be used if the
14551 exec file does not contain section addresses, (such as in the
14552 @code{a.out} format), or when the addresses specified in the file
14553 itself are wrong. Each section must be changed separately. The
14554 @code{info files} command, described below, lists all the sections and
14558 @kindex info target
14561 @code{info files} and @code{info target} are synonymous; both print the
14562 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14563 including the names of the executable and core dump files currently in
14564 use by @value{GDBN}, and the files from which symbols were loaded. The
14565 command @code{help target} lists all possible targets rather than
14568 @kindex maint info sections
14569 @item maint info sections
14570 Another command that can give you extra information about program sections
14571 is @code{maint info sections}. In addition to the section information
14572 displayed by @code{info files}, this command displays the flags and file
14573 offset of each section in the executable and core dump files. In addition,
14574 @code{maint info sections} provides the following command options (which
14575 may be arbitrarily combined):
14579 Display sections for all loaded object files, including shared libraries.
14580 @item @var{sections}
14581 Display info only for named @var{sections}.
14582 @item @var{section-flags}
14583 Display info only for sections for which @var{section-flags} are true.
14584 The section flags that @value{GDBN} currently knows about are:
14587 Section will have space allocated in the process when loaded.
14588 Set for all sections except those containing debug information.
14590 Section will be loaded from the file into the child process memory.
14591 Set for pre-initialized code and data, clear for @code{.bss} sections.
14593 Section needs to be relocated before loading.
14595 Section cannot be modified by the child process.
14597 Section contains executable code only.
14599 Section contains data only (no executable code).
14601 Section will reside in ROM.
14603 Section contains data for constructor/destructor lists.
14605 Section is not empty.
14607 An instruction to the linker to not output the section.
14608 @item COFF_SHARED_LIBRARY
14609 A notification to the linker that the section contains
14610 COFF shared library information.
14612 Section contains common symbols.
14615 @kindex set trust-readonly-sections
14616 @cindex read-only sections
14617 @item set trust-readonly-sections on
14618 Tell @value{GDBN} that readonly sections in your object file
14619 really are read-only (i.e.@: that their contents will not change).
14620 In that case, @value{GDBN} can fetch values from these sections
14621 out of the object file, rather than from the target program.
14622 For some targets (notably embedded ones), this can be a significant
14623 enhancement to debugging performance.
14625 The default is off.
14627 @item set trust-readonly-sections off
14628 Tell @value{GDBN} not to trust readonly sections. This means that
14629 the contents of the section might change while the program is running,
14630 and must therefore be fetched from the target when needed.
14632 @item show trust-readonly-sections
14633 Show the current setting of trusting readonly sections.
14636 All file-specifying commands allow both absolute and relative file names
14637 as arguments. @value{GDBN} always converts the file name to an absolute file
14638 name and remembers it that way.
14640 @cindex shared libraries
14641 @anchor{Shared Libraries}
14642 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14643 and IBM RS/6000 AIX shared libraries.
14645 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14646 shared libraries. @xref{Expat}.
14648 @value{GDBN} automatically loads symbol definitions from shared libraries
14649 when you use the @code{run} command, or when you examine a core file.
14650 (Before you issue the @code{run} command, @value{GDBN} does not understand
14651 references to a function in a shared library, however---unless you are
14652 debugging a core file).
14654 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14655 automatically loads the symbols at the time of the @code{shl_load} call.
14657 @c FIXME: some @value{GDBN} release may permit some refs to undef
14658 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14659 @c FIXME...lib; check this from time to time when updating manual
14661 There are times, however, when you may wish to not automatically load
14662 symbol definitions from shared libraries, such as when they are
14663 particularly large or there are many of them.
14665 To control the automatic loading of shared library symbols, use the
14669 @kindex set auto-solib-add
14670 @item set auto-solib-add @var{mode}
14671 If @var{mode} is @code{on}, symbols from all shared object libraries
14672 will be loaded automatically when the inferior begins execution, you
14673 attach to an independently started inferior, or when the dynamic linker
14674 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14675 is @code{off}, symbols must be loaded manually, using the
14676 @code{sharedlibrary} command. The default value is @code{on}.
14678 @cindex memory used for symbol tables
14679 If your program uses lots of shared libraries with debug info that
14680 takes large amounts of memory, you can decrease the @value{GDBN}
14681 memory footprint by preventing it from automatically loading the
14682 symbols from shared libraries. To that end, type @kbd{set
14683 auto-solib-add off} before running the inferior, then load each
14684 library whose debug symbols you do need with @kbd{sharedlibrary
14685 @var{regexp}}, where @var{regexp} is a regular expression that matches
14686 the libraries whose symbols you want to be loaded.
14688 @kindex show auto-solib-add
14689 @item show auto-solib-add
14690 Display the current autoloading mode.
14693 @cindex load shared library
14694 To explicitly load shared library symbols, use the @code{sharedlibrary}
14698 @kindex info sharedlibrary
14700 @item info share @var{regex}
14701 @itemx info sharedlibrary @var{regex}
14702 Print the names of the shared libraries which are currently loaded
14703 that match @var{regex}. If @var{regex} is omitted then print
14704 all shared libraries that are loaded.
14706 @kindex sharedlibrary
14708 @item sharedlibrary @var{regex}
14709 @itemx share @var{regex}
14710 Load shared object library symbols for files matching a
14711 Unix regular expression.
14712 As with files loaded automatically, it only loads shared libraries
14713 required by your program for a core file or after typing @code{run}. If
14714 @var{regex} is omitted all shared libraries required by your program are
14717 @item nosharedlibrary
14718 @kindex nosharedlibrary
14719 @cindex unload symbols from shared libraries
14720 Unload all shared object library symbols. This discards all symbols
14721 that have been loaded from all shared libraries. Symbols from shared
14722 libraries that were loaded by explicit user requests are not
14726 Sometimes you may wish that @value{GDBN} stops and gives you control
14727 when any of shared library events happen. Use the @code{set
14728 stop-on-solib-events} command for this:
14731 @item set stop-on-solib-events
14732 @kindex set stop-on-solib-events
14733 This command controls whether @value{GDBN} should give you control
14734 when the dynamic linker notifies it about some shared library event.
14735 The most common event of interest is loading or unloading of a new
14738 @item show stop-on-solib-events
14739 @kindex show stop-on-solib-events
14740 Show whether @value{GDBN} stops and gives you control when shared
14741 library events happen.
14744 Shared libraries are also supported in many cross or remote debugging
14745 configurations. @value{GDBN} needs to have access to the target's libraries;
14746 this can be accomplished either by providing copies of the libraries
14747 on the host system, or by asking @value{GDBN} to automatically retrieve the
14748 libraries from the target. If copies of the target libraries are
14749 provided, they need to be the same as the target libraries, although the
14750 copies on the target can be stripped as long as the copies on the host are
14753 @cindex where to look for shared libraries
14754 For remote debugging, you need to tell @value{GDBN} where the target
14755 libraries are, so that it can load the correct copies---otherwise, it
14756 may try to load the host's libraries. @value{GDBN} has two variables
14757 to specify the search directories for target libraries.
14760 @cindex prefix for shared library file names
14761 @cindex system root, alternate
14762 @kindex set solib-absolute-prefix
14763 @kindex set sysroot
14764 @item set sysroot @var{path}
14765 Use @var{path} as the system root for the program being debugged. Any
14766 absolute shared library paths will be prefixed with @var{path}; many
14767 runtime loaders store the absolute paths to the shared library in the
14768 target program's memory. If you use @code{set sysroot} to find shared
14769 libraries, they need to be laid out in the same way that they are on
14770 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14773 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14774 retrieve the target libraries from the remote system. This is only
14775 supported when using a remote target that supports the @code{remote get}
14776 command (@pxref{File Transfer,,Sending files to a remote system}).
14777 The part of @var{path} following the initial @file{remote:}
14778 (if present) is used as system root prefix on the remote file system.
14779 @footnote{If you want to specify a local system root using a directory
14780 that happens to be named @file{remote:}, you need to use some equivalent
14781 variant of the name like @file{./remote:}.}
14783 For targets with an MS-DOS based filesystem, such as MS-Windows and
14784 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
14785 absolute file name with @var{path}. But first, on Unix hosts,
14786 @value{GDBN} converts all backslash directory separators into forward
14787 slashes, because the backslash is not a directory separator on Unix:
14790 c:\foo\bar.dll @result{} c:/foo/bar.dll
14793 Then, @value{GDBN} attempts prefixing the target file name with
14794 @var{path}, and looks for the resulting file name in the host file
14798 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
14801 If that does not find the shared library, @value{GDBN} tries removing
14802 the @samp{:} character from the drive spec, both for convenience, and,
14803 for the case of the host file system not supporting file names with
14807 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
14810 This makes it possible to have a system root that mirrors a target
14811 with more than one drive. E.g., you may want to setup your local
14812 copies of the target system shared libraries like so (note @samp{c} vs
14816 @file{/path/to/sysroot/c/sys/bin/foo.dll}
14817 @file{/path/to/sysroot/c/sys/bin/bar.dll}
14818 @file{/path/to/sysroot/z/sys/bin/bar.dll}
14822 and point the system root at @file{/path/to/sysroot}, so that
14823 @value{GDBN} can find the correct copies of both
14824 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
14826 If that still does not find the shared library, @value{GDBN} tries
14827 removing the whole drive spec from the target file name:
14830 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
14833 This last lookup makes it possible to not care about the drive name,
14834 if you don't want or need to.
14836 The @code{set solib-absolute-prefix} command is an alias for @code{set
14839 @cindex default system root
14840 @cindex @samp{--with-sysroot}
14841 You can set the default system root by using the configure-time
14842 @samp{--with-sysroot} option. If the system root is inside
14843 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14844 @samp{--exec-prefix}), then the default system root will be updated
14845 automatically if the installed @value{GDBN} is moved to a new
14848 @kindex show sysroot
14850 Display the current shared library prefix.
14852 @kindex set solib-search-path
14853 @item set solib-search-path @var{path}
14854 If this variable is set, @var{path} is a colon-separated list of
14855 directories to search for shared libraries. @samp{solib-search-path}
14856 is used after @samp{sysroot} fails to locate the library, or if the
14857 path to the library is relative instead of absolute. If you want to
14858 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
14859 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
14860 finding your host's libraries. @samp{sysroot} is preferred; setting
14861 it to a nonexistent directory may interfere with automatic loading
14862 of shared library symbols.
14864 @kindex show solib-search-path
14865 @item show solib-search-path
14866 Display the current shared library search path.
14868 @cindex DOS file-name semantics of file names.
14869 @kindex set target-file-system-kind (unix|dos-based|auto)
14870 @kindex show target-file-system-kind
14871 @item set target-file-system-kind @var{kind}
14872 Set assumed file system kind for target reported file names.
14874 Shared library file names as reported by the target system may not
14875 make sense as is on the system @value{GDBN} is running on. For
14876 example, when remote debugging a target that has MS-DOS based file
14877 system semantics, from a Unix host, the target may be reporting to
14878 @value{GDBN} a list of loaded shared libraries with file names such as
14879 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
14880 drive letters, so the @samp{c:\} prefix is not normally understood as
14881 indicating an absolute file name, and neither is the backslash
14882 normally considered a directory separator character. In that case,
14883 the native file system would interpret this whole absolute file name
14884 as a relative file name with no directory components. This would make
14885 it impossible to point @value{GDBN} at a copy of the remote target's
14886 shared libraries on the host using @code{set sysroot}, and impractical
14887 with @code{set solib-search-path}. Setting
14888 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
14889 to interpret such file names similarly to how the target would, and to
14890 map them to file names valid on @value{GDBN}'s native file system
14891 semantics. The value of @var{kind} can be @code{"auto"}, in addition
14892 to one of the supported file system kinds. In that case, @value{GDBN}
14893 tries to determine the appropriate file system variant based on the
14894 current target's operating system (@pxref{ABI, ,Configuring the
14895 Current ABI}). The supported file system settings are:
14899 Instruct @value{GDBN} to assume the target file system is of Unix
14900 kind. Only file names starting the forward slash (@samp{/}) character
14901 are considered absolute, and the directory separator character is also
14905 Instruct @value{GDBN} to assume the target file system is DOS based.
14906 File names starting with either a forward slash, or a drive letter
14907 followed by a colon (e.g., @samp{c:}), are considered absolute, and
14908 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
14909 considered directory separators.
14912 Instruct @value{GDBN} to use the file system kind associated with the
14913 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
14914 This is the default.
14919 @node Separate Debug Files
14920 @section Debugging Information in Separate Files
14921 @cindex separate debugging information files
14922 @cindex debugging information in separate files
14923 @cindex @file{.debug} subdirectories
14924 @cindex debugging information directory, global
14925 @cindex global debugging information directory
14926 @cindex build ID, and separate debugging files
14927 @cindex @file{.build-id} directory
14929 @value{GDBN} allows you to put a program's debugging information in a
14930 file separate from the executable itself, in a way that allows
14931 @value{GDBN} to find and load the debugging information automatically.
14932 Since debugging information can be very large---sometimes larger
14933 than the executable code itself---some systems distribute debugging
14934 information for their executables in separate files, which users can
14935 install only when they need to debug a problem.
14937 @value{GDBN} supports two ways of specifying the separate debug info
14942 The executable contains a @dfn{debug link} that specifies the name of
14943 the separate debug info file. The separate debug file's name is
14944 usually @file{@var{executable}.debug}, where @var{executable} is the
14945 name of the corresponding executable file without leading directories
14946 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14947 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14948 checksum for the debug file, which @value{GDBN} uses to validate that
14949 the executable and the debug file came from the same build.
14952 The executable contains a @dfn{build ID}, a unique bit string that is
14953 also present in the corresponding debug info file. (This is supported
14954 only on some operating systems, notably those which use the ELF format
14955 for binary files and the @sc{gnu} Binutils.) For more details about
14956 this feature, see the description of the @option{--build-id}
14957 command-line option in @ref{Options, , Command Line Options, ld.info,
14958 The GNU Linker}. The debug info file's name is not specified
14959 explicitly by the build ID, but can be computed from the build ID, see
14963 Depending on the way the debug info file is specified, @value{GDBN}
14964 uses two different methods of looking for the debug file:
14968 For the ``debug link'' method, @value{GDBN} looks up the named file in
14969 the directory of the executable file, then in a subdirectory of that
14970 directory named @file{.debug}, and finally under the global debug
14971 directory, in a subdirectory whose name is identical to the leading
14972 directories of the executable's absolute file name.
14975 For the ``build ID'' method, @value{GDBN} looks in the
14976 @file{.build-id} subdirectory of the global debug directory for a file
14977 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14978 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14979 are the rest of the bit string. (Real build ID strings are 32 or more
14980 hex characters, not 10.)
14983 So, for example, suppose you ask @value{GDBN} to debug
14984 @file{/usr/bin/ls}, which has a debug link that specifies the
14985 file @file{ls.debug}, and a build ID whose value in hex is
14986 @code{abcdef1234}. If the global debug directory is
14987 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14988 debug information files, in the indicated order:
14992 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
14994 @file{/usr/bin/ls.debug}
14996 @file{/usr/bin/.debug/ls.debug}
14998 @file{/usr/lib/debug/usr/bin/ls.debug}.
15001 You can set the global debugging info directory's name, and view the
15002 name @value{GDBN} is currently using.
15006 @kindex set debug-file-directory
15007 @item set debug-file-directory @var{directories}
15008 Set the directories which @value{GDBN} searches for separate debugging
15009 information files to @var{directory}. Multiple directory components can be set
15010 concatenating them by a directory separator.
15012 @kindex show debug-file-directory
15013 @item show debug-file-directory
15014 Show the directories @value{GDBN} searches for separate debugging
15019 @cindex @code{.gnu_debuglink} sections
15020 @cindex debug link sections
15021 A debug link is a special section of the executable file named
15022 @code{.gnu_debuglink}. The section must contain:
15026 A filename, with any leading directory components removed, followed by
15029 zero to three bytes of padding, as needed to reach the next four-byte
15030 boundary within the section, and
15032 a four-byte CRC checksum, stored in the same endianness used for the
15033 executable file itself. The checksum is computed on the debugging
15034 information file's full contents by the function given below, passing
15035 zero as the @var{crc} argument.
15038 Any executable file format can carry a debug link, as long as it can
15039 contain a section named @code{.gnu_debuglink} with the contents
15042 @cindex @code{.note.gnu.build-id} sections
15043 @cindex build ID sections
15044 The build ID is a special section in the executable file (and in other
15045 ELF binary files that @value{GDBN} may consider). This section is
15046 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15047 It contains unique identification for the built files---the ID remains
15048 the same across multiple builds of the same build tree. The default
15049 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15050 content for the build ID string. The same section with an identical
15051 value is present in the original built binary with symbols, in its
15052 stripped variant, and in the separate debugging information file.
15054 The debugging information file itself should be an ordinary
15055 executable, containing a full set of linker symbols, sections, and
15056 debugging information. The sections of the debugging information file
15057 should have the same names, addresses, and sizes as the original file,
15058 but they need not contain any data---much like a @code{.bss} section
15059 in an ordinary executable.
15061 The @sc{gnu} binary utilities (Binutils) package includes the
15062 @samp{objcopy} utility that can produce
15063 the separated executable / debugging information file pairs using the
15064 following commands:
15067 @kbd{objcopy --only-keep-debug foo foo.debug}
15072 These commands remove the debugging
15073 information from the executable file @file{foo} and place it in the file
15074 @file{foo.debug}. You can use the first, second or both methods to link the
15079 The debug link method needs the following additional command to also leave
15080 behind a debug link in @file{foo}:
15083 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15086 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15087 a version of the @code{strip} command such that the command @kbd{strip foo -f
15088 foo.debug} has the same functionality as the two @code{objcopy} commands and
15089 the @code{ln -s} command above, together.
15092 Build ID gets embedded into the main executable using @code{ld --build-id} or
15093 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15094 compatibility fixes for debug files separation are present in @sc{gnu} binary
15095 utilities (Binutils) package since version 2.18.
15100 @cindex CRC algorithm definition
15101 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15102 IEEE 802.3 using the polynomial:
15104 @c TexInfo requires naked braces for multi-digit exponents for Tex
15105 @c output, but this causes HTML output to barf. HTML has to be set using
15106 @c raw commands. So we end up having to specify this equation in 2
15111 <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>
15112 + <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
15118 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15119 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15123 The function is computed byte at a time, taking the least
15124 significant bit of each byte first. The initial pattern
15125 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15126 the final result is inverted to ensure trailing zeros also affect the
15129 @emph{Note:} This is the same CRC polynomial as used in handling the
15130 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15131 , @value{GDBN} Remote Serial Protocol}). However in the
15132 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15133 significant bit first, and the result is not inverted, so trailing
15134 zeros have no effect on the CRC value.
15136 To complete the description, we show below the code of the function
15137 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15138 initially supplied @code{crc} argument means that an initial call to
15139 this function passing in zero will start computing the CRC using
15142 @kindex gnu_debuglink_crc32
15145 gnu_debuglink_crc32 (unsigned long crc,
15146 unsigned char *buf, size_t len)
15148 static const unsigned long crc32_table[256] =
15150 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15151 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15152 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15153 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15154 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15155 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15156 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15157 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15158 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15159 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15160 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15161 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15162 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15163 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15164 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15165 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15166 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15167 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15168 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15169 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15170 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15171 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15172 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15173 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15174 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15175 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15176 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15177 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15178 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15179 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15180 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15181 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15182 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15183 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15184 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15185 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15186 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15187 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15188 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15189 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15190 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15191 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15192 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15193 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15194 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15195 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15196 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15197 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15198 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15199 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15200 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15203 unsigned char *end;
15205 crc = ~crc & 0xffffffff;
15206 for (end = buf + len; buf < end; ++buf)
15207 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15208 return ~crc & 0xffffffff;
15213 This computation does not apply to the ``build ID'' method.
15217 @section Index Files Speed Up @value{GDBN}
15218 @cindex index files
15219 @cindex @samp{.gdb_index} section
15221 When @value{GDBN} finds a symbol file, it scans the symbols in the
15222 file in order to construct an internal symbol table. This lets most
15223 @value{GDBN} operations work quickly---at the cost of a delay early
15224 on. For large programs, this delay can be quite lengthy, so
15225 @value{GDBN} provides a way to build an index, which speeds up
15228 The index is stored as a section in the symbol file. @value{GDBN} can
15229 write the index to a file, then you can put it into the symbol file
15230 using @command{objcopy}.
15232 To create an index file, use the @code{save gdb-index} command:
15235 @item save gdb-index @var{directory}
15236 @kindex save gdb-index
15237 Create an index file for each symbol file currently known by
15238 @value{GDBN}. Each file is named after its corresponding symbol file,
15239 with @samp{.gdb-index} appended, and is written into the given
15243 Once you have created an index file you can merge it into your symbol
15244 file, here named @file{symfile}, using @command{objcopy}:
15247 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15248 --set-section-flags .gdb_index=readonly symfile symfile
15251 There are currently some limitation on indices. They only work when
15252 for DWARF debugging information, not stabs. And, they do not
15253 currently work for programs using Ada.
15255 @pindex gdb-add-index
15256 @value{GDBN} comes with a program, @command{gdb-add-index}, which can
15257 be used to add the index to a symbol file. It takes the symbol file
15258 as its only argument:
15261 $ gdb-add-index symfile
15265 @node Symbol Errors
15266 @section Errors Reading Symbol Files
15268 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15269 such as symbol types it does not recognize, or known bugs in compiler
15270 output. By default, @value{GDBN} does not notify you of such problems, since
15271 they are relatively common and primarily of interest to people
15272 debugging compilers. If you are interested in seeing information
15273 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15274 only one message about each such type of problem, no matter how many
15275 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15276 to see how many times the problems occur, with the @code{set
15277 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15280 The messages currently printed, and their meanings, include:
15283 @item inner block not inside outer block in @var{symbol}
15285 The symbol information shows where symbol scopes begin and end
15286 (such as at the start of a function or a block of statements). This
15287 error indicates that an inner scope block is not fully contained
15288 in its outer scope blocks.
15290 @value{GDBN} circumvents the problem by treating the inner block as if it had
15291 the same scope as the outer block. In the error message, @var{symbol}
15292 may be shown as ``@code{(don't know)}'' if the outer block is not a
15295 @item block at @var{address} out of order
15297 The symbol information for symbol scope blocks should occur in
15298 order of increasing addresses. This error indicates that it does not
15301 @value{GDBN} does not circumvent this problem, and has trouble
15302 locating symbols in the source file whose symbols it is reading. (You
15303 can often determine what source file is affected by specifying
15304 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15307 @item bad block start address patched
15309 The symbol information for a symbol scope block has a start address
15310 smaller than the address of the preceding source line. This is known
15311 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15313 @value{GDBN} circumvents the problem by treating the symbol scope block as
15314 starting on the previous source line.
15316 @item bad string table offset in symbol @var{n}
15319 Symbol number @var{n} contains a pointer into the string table which is
15320 larger than the size of the string table.
15322 @value{GDBN} circumvents the problem by considering the symbol to have the
15323 name @code{foo}, which may cause other problems if many symbols end up
15326 @item unknown symbol type @code{0x@var{nn}}
15328 The symbol information contains new data types that @value{GDBN} does
15329 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15330 uncomprehended information, in hexadecimal.
15332 @value{GDBN} circumvents the error by ignoring this symbol information.
15333 This usually allows you to debug your program, though certain symbols
15334 are not accessible. If you encounter such a problem and feel like
15335 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15336 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15337 and examine @code{*bufp} to see the symbol.
15339 @item stub type has NULL name
15341 @value{GDBN} could not find the full definition for a struct or class.
15343 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15344 The symbol information for a C@t{++} member function is missing some
15345 information that recent versions of the compiler should have output for
15348 @item info mismatch between compiler and debugger
15350 @value{GDBN} could not parse a type specification output by the compiler.
15355 @section GDB Data Files
15357 @cindex prefix for data files
15358 @value{GDBN} will sometimes read an auxiliary data file. These files
15359 are kept in a directory known as the @dfn{data directory}.
15361 You can set the data directory's name, and view the name @value{GDBN}
15362 is currently using.
15365 @kindex set data-directory
15366 @item set data-directory @var{directory}
15367 Set the directory which @value{GDBN} searches for auxiliary data files
15368 to @var{directory}.
15370 @kindex show data-directory
15371 @item show data-directory
15372 Show the directory @value{GDBN} searches for auxiliary data files.
15375 @cindex default data directory
15376 @cindex @samp{--with-gdb-datadir}
15377 You can set the default data directory by using the configure-time
15378 @samp{--with-gdb-datadir} option. If the data directory is inside
15379 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15380 @samp{--exec-prefix}), then the default data directory will be updated
15381 automatically if the installed @value{GDBN} is moved to a new
15385 @chapter Specifying a Debugging Target
15387 @cindex debugging target
15388 A @dfn{target} is the execution environment occupied by your program.
15390 Often, @value{GDBN} runs in the same host environment as your program;
15391 in that case, the debugging target is specified as a side effect when
15392 you use the @code{file} or @code{core} commands. When you need more
15393 flexibility---for example, running @value{GDBN} on a physically separate
15394 host, or controlling a standalone system over a serial port or a
15395 realtime system over a TCP/IP connection---you can use the @code{target}
15396 command to specify one of the target types configured for @value{GDBN}
15397 (@pxref{Target Commands, ,Commands for Managing Targets}).
15399 @cindex target architecture
15400 It is possible to build @value{GDBN} for several different @dfn{target
15401 architectures}. When @value{GDBN} is built like that, you can choose
15402 one of the available architectures with the @kbd{set architecture}
15406 @kindex set architecture
15407 @kindex show architecture
15408 @item set architecture @var{arch}
15409 This command sets the current target architecture to @var{arch}. The
15410 value of @var{arch} can be @code{"auto"}, in addition to one of the
15411 supported architectures.
15413 @item show architecture
15414 Show the current target architecture.
15416 @item set processor
15418 @kindex set processor
15419 @kindex show processor
15420 These are alias commands for, respectively, @code{set architecture}
15421 and @code{show architecture}.
15425 * Active Targets:: Active targets
15426 * Target Commands:: Commands for managing targets
15427 * Byte Order:: Choosing target byte order
15430 @node Active Targets
15431 @section Active Targets
15433 @cindex stacking targets
15434 @cindex active targets
15435 @cindex multiple targets
15437 There are multiple classes of targets such as: processes, executable files or
15438 recording sessions. Core files belong to the process class, making core file
15439 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
15440 on multiple active targets, one in each class. This allows you to (for
15441 example) start a process and inspect its activity, while still having access to
15442 the executable file after the process finishes. Or if you start process
15443 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
15444 presented a virtual layer of the recording target, while the process target
15445 remains stopped at the chronologically last point of the process execution.
15447 Use the @code{core-file} and @code{exec-file} commands to select a new core
15448 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
15449 specify as a target a process that is already running, use the @code{attach}
15450 command (@pxref{Attach, ,Debugging an Already-running Process}).
15452 @node Target Commands
15453 @section Commands for Managing Targets
15456 @item target @var{type} @var{parameters}
15457 Connects the @value{GDBN} host environment to a target machine or
15458 process. A target is typically a protocol for talking to debugging
15459 facilities. You use the argument @var{type} to specify the type or
15460 protocol of the target machine.
15462 Further @var{parameters} are interpreted by the target protocol, but
15463 typically include things like device names or host names to connect
15464 with, process numbers, and baud rates.
15466 The @code{target} command does not repeat if you press @key{RET} again
15467 after executing the command.
15469 @kindex help target
15471 Displays the names of all targets available. To display targets
15472 currently selected, use either @code{info target} or @code{info files}
15473 (@pxref{Files, ,Commands to Specify Files}).
15475 @item help target @var{name}
15476 Describe a particular target, including any parameters necessary to
15479 @kindex set gnutarget
15480 @item set gnutarget @var{args}
15481 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15482 knows whether it is reading an @dfn{executable},
15483 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15484 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15485 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15488 @emph{Warning:} To specify a file format with @code{set gnutarget},
15489 you must know the actual BFD name.
15493 @xref{Files, , Commands to Specify Files}.
15495 @kindex show gnutarget
15496 @item show gnutarget
15497 Use the @code{show gnutarget} command to display what file format
15498 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15499 @value{GDBN} will determine the file format for each file automatically,
15500 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15503 @cindex common targets
15504 Here are some common targets (available, or not, depending on the GDB
15509 @item target exec @var{program}
15510 @cindex executable file target
15511 An executable file. @samp{target exec @var{program}} is the same as
15512 @samp{exec-file @var{program}}.
15514 @item target core @var{filename}
15515 @cindex core dump file target
15516 A core dump file. @samp{target core @var{filename}} is the same as
15517 @samp{core-file @var{filename}}.
15519 @item target remote @var{medium}
15520 @cindex remote target
15521 A remote system connected to @value{GDBN} via a serial line or network
15522 connection. This command tells @value{GDBN} to use its own remote
15523 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15525 For example, if you have a board connected to @file{/dev/ttya} on the
15526 machine running @value{GDBN}, you could say:
15529 target remote /dev/ttya
15532 @code{target remote} supports the @code{load} command. This is only
15533 useful if you have some other way of getting the stub to the target
15534 system, and you can put it somewhere in memory where it won't get
15535 clobbered by the download.
15537 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15538 @cindex built-in simulator target
15539 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15547 works; however, you cannot assume that a specific memory map, device
15548 drivers, or even basic I/O is available, although some simulators do
15549 provide these. For info about any processor-specific simulator details,
15550 see the appropriate section in @ref{Embedded Processors, ,Embedded
15555 Some configurations may include these targets as well:
15559 @item target nrom @var{dev}
15560 @cindex NetROM ROM emulator target
15561 NetROM ROM emulator. This target only supports downloading.
15565 Different targets are available on different configurations of @value{GDBN};
15566 your configuration may have more or fewer targets.
15568 Many remote targets require you to download the executable's code once
15569 you've successfully established a connection. You may wish to control
15570 various aspects of this process.
15575 @kindex set hash@r{, for remote monitors}
15576 @cindex hash mark while downloading
15577 This command controls whether a hash mark @samp{#} is displayed while
15578 downloading a file to the remote monitor. If on, a hash mark is
15579 displayed after each S-record is successfully downloaded to the
15583 @kindex show hash@r{, for remote monitors}
15584 Show the current status of displaying the hash mark.
15586 @item set debug monitor
15587 @kindex set debug monitor
15588 @cindex display remote monitor communications
15589 Enable or disable display of communications messages between
15590 @value{GDBN} and the remote monitor.
15592 @item show debug monitor
15593 @kindex show debug monitor
15594 Show the current status of displaying communications between
15595 @value{GDBN} and the remote monitor.
15600 @kindex load @var{filename}
15601 @item load @var{filename}
15603 Depending on what remote debugging facilities are configured into
15604 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15605 is meant to make @var{filename} (an executable) available for debugging
15606 on the remote system---by downloading, or dynamic linking, for example.
15607 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15608 the @code{add-symbol-file} command.
15610 If your @value{GDBN} does not have a @code{load} command, attempting to
15611 execute it gets the error message ``@code{You can't do that when your
15612 target is @dots{}}''
15614 The file is loaded at whatever address is specified in the executable.
15615 For some object file formats, you can specify the load address when you
15616 link the program; for other formats, like a.out, the object file format
15617 specifies a fixed address.
15618 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15620 Depending on the remote side capabilities, @value{GDBN} may be able to
15621 load programs into flash memory.
15623 @code{load} does not repeat if you press @key{RET} again after using it.
15627 @section Choosing Target Byte Order
15629 @cindex choosing target byte order
15630 @cindex target byte order
15632 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15633 offer the ability to run either big-endian or little-endian byte
15634 orders. Usually the executable or symbol will include a bit to
15635 designate the endian-ness, and you will not need to worry about
15636 which to use. However, you may still find it useful to adjust
15637 @value{GDBN}'s idea of processor endian-ness manually.
15641 @item set endian big
15642 Instruct @value{GDBN} to assume the target is big-endian.
15644 @item set endian little
15645 Instruct @value{GDBN} to assume the target is little-endian.
15647 @item set endian auto
15648 Instruct @value{GDBN} to use the byte order associated with the
15652 Display @value{GDBN}'s current idea of the target byte order.
15656 Note that these commands merely adjust interpretation of symbolic
15657 data on the host, and that they have absolutely no effect on the
15661 @node Remote Debugging
15662 @chapter Debugging Remote Programs
15663 @cindex remote debugging
15665 If you are trying to debug a program running on a machine that cannot run
15666 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15667 For example, you might use remote debugging on an operating system kernel,
15668 or on a small system which does not have a general purpose operating system
15669 powerful enough to run a full-featured debugger.
15671 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15672 to make this work with particular debugging targets. In addition,
15673 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15674 but not specific to any particular target system) which you can use if you
15675 write the remote stubs---the code that runs on the remote system to
15676 communicate with @value{GDBN}.
15678 Other remote targets may be available in your
15679 configuration of @value{GDBN}; use @code{help target} to list them.
15682 * Connecting:: Connecting to a remote target
15683 * File Transfer:: Sending files to a remote system
15684 * Server:: Using the gdbserver program
15685 * Remote Configuration:: Remote configuration
15686 * Remote Stub:: Implementing a remote stub
15690 @section Connecting to a Remote Target
15692 On the @value{GDBN} host machine, you will need an unstripped copy of
15693 your program, since @value{GDBN} needs symbol and debugging information.
15694 Start up @value{GDBN} as usual, using the name of the local copy of your
15695 program as the first argument.
15697 @cindex @code{target remote}
15698 @value{GDBN} can communicate with the target over a serial line, or
15699 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15700 each case, @value{GDBN} uses the same protocol for debugging your
15701 program; only the medium carrying the debugging packets varies. The
15702 @code{target remote} command establishes a connection to the target.
15703 Its arguments indicate which medium to use:
15707 @item target remote @var{serial-device}
15708 @cindex serial line, @code{target remote}
15709 Use @var{serial-device} to communicate with the target. For example,
15710 to use a serial line connected to the device named @file{/dev/ttyb}:
15713 target remote /dev/ttyb
15716 If you're using a serial line, you may want to give @value{GDBN} the
15717 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15718 (@pxref{Remote Configuration, set remotebaud}) before the
15719 @code{target} command.
15721 @item target remote @code{@var{host}:@var{port}}
15722 @itemx target remote @code{tcp:@var{host}:@var{port}}
15723 @cindex @acronym{TCP} port, @code{target remote}
15724 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15725 The @var{host} may be either a host name or a numeric @acronym{IP}
15726 address; @var{port} must be a decimal number. The @var{host} could be
15727 the target machine itself, if it is directly connected to the net, or
15728 it might be a terminal server which in turn has a serial line to the
15731 For example, to connect to port 2828 on a terminal server named
15735 target remote manyfarms:2828
15738 If your remote target is actually running on the same machine as your
15739 debugger session (e.g.@: a simulator for your target running on the
15740 same host), you can omit the hostname. For example, to connect to
15741 port 1234 on your local machine:
15744 target remote :1234
15748 Note that the colon is still required here.
15750 @item target remote @code{udp:@var{host}:@var{port}}
15751 @cindex @acronym{UDP} port, @code{target remote}
15752 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15753 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15756 target remote udp:manyfarms:2828
15759 When using a @acronym{UDP} connection for remote debugging, you should
15760 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15761 can silently drop packets on busy or unreliable networks, which will
15762 cause havoc with your debugging session.
15764 @item target remote | @var{command}
15765 @cindex pipe, @code{target remote} to
15766 Run @var{command} in the background and communicate with it using a
15767 pipe. The @var{command} is a shell command, to be parsed and expanded
15768 by the system's command shell, @code{/bin/sh}; it should expect remote
15769 protocol packets on its standard input, and send replies on its
15770 standard output. You could use this to run a stand-alone simulator
15771 that speaks the remote debugging protocol, to make net connections
15772 using programs like @code{ssh}, or for other similar tricks.
15774 If @var{command} closes its standard output (perhaps by exiting),
15775 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15776 program has already exited, this will have no effect.)
15780 Once the connection has been established, you can use all the usual
15781 commands to examine and change data. The remote program is already
15782 running; you can use @kbd{step} and @kbd{continue}, and you do not
15783 need to use @kbd{run}.
15785 @cindex interrupting remote programs
15786 @cindex remote programs, interrupting
15787 Whenever @value{GDBN} is waiting for the remote program, if you type the
15788 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15789 program. This may or may not succeed, depending in part on the hardware
15790 and the serial drivers the remote system uses. If you type the
15791 interrupt character once again, @value{GDBN} displays this prompt:
15794 Interrupted while waiting for the program.
15795 Give up (and stop debugging it)? (y or n)
15798 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15799 (If you decide you want to try again later, you can use @samp{target
15800 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15801 goes back to waiting.
15804 @kindex detach (remote)
15806 When you have finished debugging the remote program, you can use the
15807 @code{detach} command to release it from @value{GDBN} control.
15808 Detaching from the target normally resumes its execution, but the results
15809 will depend on your particular remote stub. After the @code{detach}
15810 command, @value{GDBN} is free to connect to another target.
15814 The @code{disconnect} command behaves like @code{detach}, except that
15815 the target is generally not resumed. It will wait for @value{GDBN}
15816 (this instance or another one) to connect and continue debugging. After
15817 the @code{disconnect} command, @value{GDBN} is again free to connect to
15820 @cindex send command to remote monitor
15821 @cindex extend @value{GDBN} for remote targets
15822 @cindex add new commands for external monitor
15824 @item monitor @var{cmd}
15825 This command allows you to send arbitrary commands directly to the
15826 remote monitor. Since @value{GDBN} doesn't care about the commands it
15827 sends like this, this command is the way to extend @value{GDBN}---you
15828 can add new commands that only the external monitor will understand
15832 @node File Transfer
15833 @section Sending files to a remote system
15834 @cindex remote target, file transfer
15835 @cindex file transfer
15836 @cindex sending files to remote systems
15838 Some remote targets offer the ability to transfer files over the same
15839 connection used to communicate with @value{GDBN}. This is convenient
15840 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
15841 running @code{gdbserver} over a network interface. For other targets,
15842 e.g.@: embedded devices with only a single serial port, this may be
15843 the only way to upload or download files.
15845 Not all remote targets support these commands.
15849 @item remote put @var{hostfile} @var{targetfile}
15850 Copy file @var{hostfile} from the host system (the machine running
15851 @value{GDBN}) to @var{targetfile} on the target system.
15854 @item remote get @var{targetfile} @var{hostfile}
15855 Copy file @var{targetfile} from the target system to @var{hostfile}
15856 on the host system.
15858 @kindex remote delete
15859 @item remote delete @var{targetfile}
15860 Delete @var{targetfile} from the target system.
15865 @section Using the @code{gdbserver} Program
15868 @cindex remote connection without stubs
15869 @code{gdbserver} is a control program for Unix-like systems, which
15870 allows you to connect your program with a remote @value{GDBN} via
15871 @code{target remote}---but without linking in the usual debugging stub.
15873 @code{gdbserver} is not a complete replacement for the debugging stubs,
15874 because it requires essentially the same operating-system facilities
15875 that @value{GDBN} itself does. In fact, a system that can run
15876 @code{gdbserver} to connect to a remote @value{GDBN} could also run
15877 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
15878 because it is a much smaller program than @value{GDBN} itself. It is
15879 also easier to port than all of @value{GDBN}, so you may be able to get
15880 started more quickly on a new system by using @code{gdbserver}.
15881 Finally, if you develop code for real-time systems, you may find that
15882 the tradeoffs involved in real-time operation make it more convenient to
15883 do as much development work as possible on another system, for example
15884 by cross-compiling. You can use @code{gdbserver} to make a similar
15885 choice for debugging.
15887 @value{GDBN} and @code{gdbserver} communicate via either a serial line
15888 or a TCP connection, using the standard @value{GDBN} remote serial
15892 @emph{Warning:} @code{gdbserver} does not have any built-in security.
15893 Do not run @code{gdbserver} connected to any public network; a
15894 @value{GDBN} connection to @code{gdbserver} provides access to the
15895 target system with the same privileges as the user running
15899 @subsection Running @code{gdbserver}
15900 @cindex arguments, to @code{gdbserver}
15902 Run @code{gdbserver} on the target system. You need a copy of the
15903 program you want to debug, including any libraries it requires.
15904 @code{gdbserver} does not need your program's symbol table, so you can
15905 strip the program if necessary to save space. @value{GDBN} on the host
15906 system does all the symbol handling.
15908 To use the server, you must tell it how to communicate with @value{GDBN};
15909 the name of your program; and the arguments for your program. The usual
15913 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
15916 @var{comm} is either a device name (to use a serial line) or a TCP
15917 hostname and portnumber. For example, to debug Emacs with the argument
15918 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
15922 target> gdbserver /dev/com1 emacs foo.txt
15925 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
15928 To use a TCP connection instead of a serial line:
15931 target> gdbserver host:2345 emacs foo.txt
15934 The only difference from the previous example is the first argument,
15935 specifying that you are communicating with the host @value{GDBN} via
15936 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
15937 expect a TCP connection from machine @samp{host} to local TCP port 2345.
15938 (Currently, the @samp{host} part is ignored.) You can choose any number
15939 you want for the port number as long as it does not conflict with any
15940 TCP ports already in use on the target system (for example, @code{23} is
15941 reserved for @code{telnet}).@footnote{If you choose a port number that
15942 conflicts with another service, @code{gdbserver} prints an error message
15943 and exits.} You must use the same port number with the host @value{GDBN}
15944 @code{target remote} command.
15946 @subsubsection Attaching to a Running Program
15948 On some targets, @code{gdbserver} can also attach to running programs.
15949 This is accomplished via the @code{--attach} argument. The syntax is:
15952 target> gdbserver --attach @var{comm} @var{pid}
15955 @var{pid} is the process ID of a currently running process. It isn't necessary
15956 to point @code{gdbserver} at a binary for the running process.
15959 @cindex attach to a program by name
15960 You can debug processes by name instead of process ID if your target has the
15961 @code{pidof} utility:
15964 target> gdbserver --attach @var{comm} `pidof @var{program}`
15967 In case more than one copy of @var{program} is running, or @var{program}
15968 has multiple threads, most versions of @code{pidof} support the
15969 @code{-s} option to only return the first process ID.
15971 @subsubsection Multi-Process Mode for @code{gdbserver}
15972 @cindex gdbserver, multiple processes
15973 @cindex multiple processes with gdbserver
15975 When you connect to @code{gdbserver} using @code{target remote},
15976 @code{gdbserver} debugs the specified program only once. When the
15977 program exits, or you detach from it, @value{GDBN} closes the connection
15978 and @code{gdbserver} exits.
15980 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15981 enters multi-process mode. When the debugged program exits, or you
15982 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15983 though no program is running. The @code{run} and @code{attach}
15984 commands instruct @code{gdbserver} to run or attach to a new program.
15985 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15986 remote exec-file}) to select the program to run. Command line
15987 arguments are supported, except for wildcard expansion and I/O
15988 redirection (@pxref{Arguments}).
15990 To start @code{gdbserver} without supplying an initial command to run
15991 or process ID to attach, use the @option{--multi} command line option.
15992 Then you can connect using @kbd{target extended-remote} and start
15993 the program you want to debug.
15995 @code{gdbserver} does not automatically exit in multi-process mode.
15996 You can terminate it by using @code{monitor exit}
15997 (@pxref{Monitor Commands for gdbserver}).
15999 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16001 The @option{--debug} option tells @code{gdbserver} to display extra
16002 status information about the debugging process. The
16003 @option{--remote-debug} option tells @code{gdbserver} to display
16004 remote protocol debug output. These options are intended for
16005 @code{gdbserver} development and for bug reports to the developers.
16007 The @option{--wrapper} option specifies a wrapper to launch programs
16008 for debugging. The option should be followed by the name of the
16009 wrapper, then any command-line arguments to pass to the wrapper, then
16010 @kbd{--} indicating the end of the wrapper arguments.
16012 @code{gdbserver} runs the specified wrapper program with a combined
16013 command line including the wrapper arguments, then the name of the
16014 program to debug, then any arguments to the program. The wrapper
16015 runs until it executes your program, and then @value{GDBN} gains control.
16017 You can use any program that eventually calls @code{execve} with
16018 its arguments as a wrapper. Several standard Unix utilities do
16019 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16020 with @code{exec "$@@"} will also work.
16022 For example, you can use @code{env} to pass an environment variable to
16023 the debugged program, without setting the variable in @code{gdbserver}'s
16027 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16030 @subsection Connecting to @code{gdbserver}
16032 Run @value{GDBN} on the host system.
16034 First make sure you have the necessary symbol files. Load symbols for
16035 your application using the @code{file} command before you connect. Use
16036 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16037 was compiled with the correct sysroot using @code{--with-sysroot}).
16039 The symbol file and target libraries must exactly match the executable
16040 and libraries on the target, with one exception: the files on the host
16041 system should not be stripped, even if the files on the target system
16042 are. Mismatched or missing files will lead to confusing results
16043 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16044 files may also prevent @code{gdbserver} from debugging multi-threaded
16047 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16048 For TCP connections, you must start up @code{gdbserver} prior to using
16049 the @code{target remote} command. Otherwise you may get an error whose
16050 text depends on the host system, but which usually looks something like
16051 @samp{Connection refused}. Don't use the @code{load}
16052 command in @value{GDBN} when using @code{gdbserver}, since the program is
16053 already on the target.
16055 @subsection Monitor Commands for @code{gdbserver}
16056 @cindex monitor commands, for @code{gdbserver}
16057 @anchor{Monitor Commands for gdbserver}
16059 During a @value{GDBN} session using @code{gdbserver}, you can use the
16060 @code{monitor} command to send special requests to @code{gdbserver}.
16061 Here are the available commands.
16065 List the available monitor commands.
16067 @item monitor set debug 0
16068 @itemx monitor set debug 1
16069 Disable or enable general debugging messages.
16071 @item monitor set remote-debug 0
16072 @itemx monitor set remote-debug 1
16073 Disable or enable specific debugging messages associated with the remote
16074 protocol (@pxref{Remote Protocol}).
16076 @item monitor set libthread-db-search-path [PATH]
16077 @cindex gdbserver, search path for @code{libthread_db}
16078 When this command is issued, @var{path} is a colon-separated list of
16079 directories to search for @code{libthread_db} (@pxref{Threads,,set
16080 libthread-db-search-path}). If you omit @var{path},
16081 @samp{libthread-db-search-path} will be reset to an empty list.
16084 Tell gdbserver to exit immediately. This command should be followed by
16085 @code{disconnect} to close the debugging session. @code{gdbserver} will
16086 detach from any attached processes and kill any processes it created.
16087 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16088 of a multi-process mode debug session.
16092 @subsection Tracepoints support in @code{gdbserver}
16093 @cindex tracepoints support in @code{gdbserver}
16095 On some targets, @code{gdbserver} supports tracepoints, fast
16096 tracepoints and static tracepoints.
16098 For fast or static tracepoints to work, a special library called the
16099 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16100 This library is built and distributed as an integral part of
16101 @code{gdbserver}. In addition, support for static tracepoints
16102 requires building the in-process agent library with static tracepoints
16103 support. At present, the UST (LTTng Userspace Tracer,
16104 @url{http://lttng.org/ust}) tracing engine is supported. This support
16105 is automatically available if UST development headers are found in the
16106 standard include path when @code{gdbserver} is built, or if
16107 @code{gdbserver} was explicitly configured using @option{--with-ust}
16108 to point at such headers. You can explicitly disable the support
16109 using @option{--with-ust=no}.
16111 There are several ways to load the in-process agent in your program:
16114 @item Specifying it as dependency at link time
16116 You can link your program dynamically with the in-process agent
16117 library. On most systems, this is accomplished by adding
16118 @code{-linproctrace} to the link command.
16120 @item Using the system's preloading mechanisms
16122 You can force loading the in-process agent at startup time by using
16123 your system's support for preloading shared libraries. Many Unixes
16124 support the concept of preloading user defined libraries. In most
16125 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16126 in the environment. See also the description of @code{gdbserver}'s
16127 @option{--wrapper} command line option.
16129 @item Using @value{GDBN} to force loading the agent at run time
16131 On some systems, you can force the inferior to load a shared library,
16132 by calling a dynamic loader function in the inferior that takes care
16133 of dynamically looking up and loading a shared library. On most Unix
16134 systems, the function is @code{dlopen}. You'll use the @code{call}
16135 command for that. For example:
16138 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16141 Note that on most Unix systems, for the @code{dlopen} function to be
16142 available, the program needs to be linked with @code{-ldl}.
16145 On systems that have a userspace dynamic loader, like most Unix
16146 systems, when you connect to @code{gdbserver} using @code{target
16147 remote}, you'll find that the program is stopped at the dynamic
16148 loader's entry point, and no shared library has been loaded in the
16149 program's address space yet, including the in-process agent. In that
16150 case, before being able to use any of the fast or static tracepoints
16151 features, you need to let the loader run and load the shared
16152 libraries. The simplest way to do that is to run the program to the
16153 main procedure. E.g., if debugging a C or C@t{++} program, start
16154 @code{gdbserver} like so:
16157 $ gdbserver :9999 myprogram
16160 Start GDB and connect to @code{gdbserver} like so, and run to main:
16164 (@value{GDBP}) target remote myhost:9999
16165 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16166 (@value{GDBP}) b main
16167 (@value{GDBP}) continue
16170 The in-process tracing agent library should now be loaded into the
16171 process; you can confirm it with the @code{info sharedlibrary}
16172 command, which will list @file{libinproctrace.so} as loaded in the
16173 process. You are now ready to install fast tracepoints, list static
16174 tracepoint markers, probe static tracepoints markers, and start
16177 @node Remote Configuration
16178 @section Remote Configuration
16181 @kindex show remote
16182 This section documents the configuration options available when
16183 debugging remote programs. For the options related to the File I/O
16184 extensions of the remote protocol, see @ref{system,
16185 system-call-allowed}.
16188 @item set remoteaddresssize @var{bits}
16189 @cindex address size for remote targets
16190 @cindex bits in remote address
16191 Set the maximum size of address in a memory packet to the specified
16192 number of bits. @value{GDBN} will mask off the address bits above
16193 that number, when it passes addresses to the remote target. The
16194 default value is the number of bits in the target's address.
16196 @item show remoteaddresssize
16197 Show the current value of remote address size in bits.
16199 @item set remotebaud @var{n}
16200 @cindex baud rate for remote targets
16201 Set the baud rate for the remote serial I/O to @var{n} baud. The
16202 value is used to set the speed of the serial port used for debugging
16205 @item show remotebaud
16206 Show the current speed of the remote connection.
16208 @item set remotebreak
16209 @cindex interrupt remote programs
16210 @cindex BREAK signal instead of Ctrl-C
16211 @anchor{set remotebreak}
16212 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16213 when you type @kbd{Ctrl-c} to interrupt the program running
16214 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16215 character instead. The default is off, since most remote systems
16216 expect to see @samp{Ctrl-C} as the interrupt signal.
16218 @item show remotebreak
16219 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16220 interrupt the remote program.
16222 @item set remoteflow on
16223 @itemx set remoteflow off
16224 @kindex set remoteflow
16225 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16226 on the serial port used to communicate to the remote target.
16228 @item show remoteflow
16229 @kindex show remoteflow
16230 Show the current setting of hardware flow control.
16232 @item set remotelogbase @var{base}
16233 Set the base (a.k.a.@: radix) of logging serial protocol
16234 communications to @var{base}. Supported values of @var{base} are:
16235 @code{ascii}, @code{octal}, and @code{hex}. The default is
16238 @item show remotelogbase
16239 Show the current setting of the radix for logging remote serial
16242 @item set remotelogfile @var{file}
16243 @cindex record serial communications on file
16244 Record remote serial communications on the named @var{file}. The
16245 default is not to record at all.
16247 @item show remotelogfile.
16248 Show the current setting of the file name on which to record the
16249 serial communications.
16251 @item set remotetimeout @var{num}
16252 @cindex timeout for serial communications
16253 @cindex remote timeout
16254 Set the timeout limit to wait for the remote target to respond to
16255 @var{num} seconds. The default is 2 seconds.
16257 @item show remotetimeout
16258 Show the current number of seconds to wait for the remote target
16261 @cindex limit hardware breakpoints and watchpoints
16262 @cindex remote target, limit break- and watchpoints
16263 @anchor{set remote hardware-watchpoint-limit}
16264 @anchor{set remote hardware-breakpoint-limit}
16265 @item set remote hardware-watchpoint-limit @var{limit}
16266 @itemx set remote hardware-breakpoint-limit @var{limit}
16267 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16268 watchpoints. A limit of -1, the default, is treated as unlimited.
16270 @item set remote exec-file @var{filename}
16271 @itemx show remote exec-file
16272 @anchor{set remote exec-file}
16273 @cindex executable file, for remote target
16274 Select the file used for @code{run} with @code{target
16275 extended-remote}. This should be set to a filename valid on the
16276 target system. If it is not set, the target will use a default
16277 filename (e.g.@: the last program run).
16279 @item set remote interrupt-sequence
16280 @cindex interrupt remote programs
16281 @cindex select Ctrl-C, BREAK or BREAK-g
16282 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16283 @samp{BREAK-g} as the
16284 sequence to the remote target in order to interrupt the execution.
16285 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16286 is high level of serial line for some certain time.
16287 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16288 It is @code{BREAK} signal followed by character @code{g}.
16290 @item show interrupt-sequence
16291 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16292 is sent by @value{GDBN} to interrupt the remote program.
16293 @code{BREAK-g} is BREAK signal followed by @code{g} and
16294 also known as Magic SysRq g.
16296 @item set remote interrupt-on-connect
16297 @cindex send interrupt-sequence on start
16298 Specify whether interrupt-sequence is sent to remote target when
16299 @value{GDBN} connects to it. This is mostly needed when you debug
16300 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16301 which is known as Magic SysRq g in order to connect @value{GDBN}.
16303 @item show interrupt-on-connect
16304 Show whether interrupt-sequence is sent
16305 to remote target when @value{GDBN} connects to it.
16309 @item set tcp auto-retry on
16310 @cindex auto-retry, for remote TCP target
16311 Enable auto-retry for remote TCP connections. This is useful if the remote
16312 debugging agent is launched in parallel with @value{GDBN}; there is a race
16313 condition because the agent may not become ready to accept the connection
16314 before @value{GDBN} attempts to connect. When auto-retry is
16315 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16316 to establish the connection using the timeout specified by
16317 @code{set tcp connect-timeout}.
16319 @item set tcp auto-retry off
16320 Do not auto-retry failed TCP connections.
16322 @item show tcp auto-retry
16323 Show the current auto-retry setting.
16325 @item set tcp connect-timeout @var{seconds}
16326 @cindex connection timeout, for remote TCP target
16327 @cindex timeout, for remote target connection
16328 Set the timeout for establishing a TCP connection to the remote target to
16329 @var{seconds}. The timeout affects both polling to retry failed connections
16330 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16331 that are merely slow to complete, and represents an approximate cumulative
16334 @item show tcp connect-timeout
16335 Show the current connection timeout setting.
16338 @cindex remote packets, enabling and disabling
16339 The @value{GDBN} remote protocol autodetects the packets supported by
16340 your debugging stub. If you need to override the autodetection, you
16341 can use these commands to enable or disable individual packets. Each
16342 packet can be set to @samp{on} (the remote target supports this
16343 packet), @samp{off} (the remote target does not support this packet),
16344 or @samp{auto} (detect remote target support for this packet). They
16345 all default to @samp{auto}. For more information about each packet,
16346 see @ref{Remote Protocol}.
16348 During normal use, you should not have to use any of these commands.
16349 If you do, that may be a bug in your remote debugging stub, or a bug
16350 in @value{GDBN}. You may want to report the problem to the
16351 @value{GDBN} developers.
16353 For each packet @var{name}, the command to enable or disable the
16354 packet is @code{set remote @var{name}-packet}. The available settings
16357 @multitable @columnfractions 0.28 0.32 0.25
16360 @tab Related Features
16362 @item @code{fetch-register}
16364 @tab @code{info registers}
16366 @item @code{set-register}
16370 @item @code{binary-download}
16372 @tab @code{load}, @code{set}
16374 @item @code{read-aux-vector}
16375 @tab @code{qXfer:auxv:read}
16376 @tab @code{info auxv}
16378 @item @code{symbol-lookup}
16379 @tab @code{qSymbol}
16380 @tab Detecting multiple threads
16382 @item @code{attach}
16383 @tab @code{vAttach}
16386 @item @code{verbose-resume}
16388 @tab Stepping or resuming multiple threads
16394 @item @code{software-breakpoint}
16398 @item @code{hardware-breakpoint}
16402 @item @code{write-watchpoint}
16406 @item @code{read-watchpoint}
16410 @item @code{access-watchpoint}
16414 @item @code{target-features}
16415 @tab @code{qXfer:features:read}
16416 @tab @code{set architecture}
16418 @item @code{library-info}
16419 @tab @code{qXfer:libraries:read}
16420 @tab @code{info sharedlibrary}
16422 @item @code{memory-map}
16423 @tab @code{qXfer:memory-map:read}
16424 @tab @code{info mem}
16426 @item @code{read-sdata-object}
16427 @tab @code{qXfer:sdata:read}
16428 @tab @code{print $_sdata}
16430 @item @code{read-spu-object}
16431 @tab @code{qXfer:spu:read}
16432 @tab @code{info spu}
16434 @item @code{write-spu-object}
16435 @tab @code{qXfer:spu:write}
16436 @tab @code{info spu}
16438 @item @code{read-siginfo-object}
16439 @tab @code{qXfer:siginfo:read}
16440 @tab @code{print $_siginfo}
16442 @item @code{write-siginfo-object}
16443 @tab @code{qXfer:siginfo:write}
16444 @tab @code{set $_siginfo}
16446 @item @code{threads}
16447 @tab @code{qXfer:threads:read}
16448 @tab @code{info threads}
16450 @item @code{get-thread-local-@*storage-address}
16451 @tab @code{qGetTLSAddr}
16452 @tab Displaying @code{__thread} variables
16454 @item @code{get-thread-information-block-address}
16455 @tab @code{qGetTIBAddr}
16456 @tab Display MS-Windows Thread Information Block.
16458 @item @code{search-memory}
16459 @tab @code{qSearch:memory}
16462 @item @code{supported-packets}
16463 @tab @code{qSupported}
16464 @tab Remote communications parameters
16466 @item @code{pass-signals}
16467 @tab @code{QPassSignals}
16468 @tab @code{handle @var{signal}}
16470 @item @code{hostio-close-packet}
16471 @tab @code{vFile:close}
16472 @tab @code{remote get}, @code{remote put}
16474 @item @code{hostio-open-packet}
16475 @tab @code{vFile:open}
16476 @tab @code{remote get}, @code{remote put}
16478 @item @code{hostio-pread-packet}
16479 @tab @code{vFile:pread}
16480 @tab @code{remote get}, @code{remote put}
16482 @item @code{hostio-pwrite-packet}
16483 @tab @code{vFile:pwrite}
16484 @tab @code{remote get}, @code{remote put}
16486 @item @code{hostio-unlink-packet}
16487 @tab @code{vFile:unlink}
16488 @tab @code{remote delete}
16490 @item @code{noack-packet}
16491 @tab @code{QStartNoAckMode}
16492 @tab Packet acknowledgment
16494 @item @code{osdata}
16495 @tab @code{qXfer:osdata:read}
16496 @tab @code{info os}
16498 @item @code{query-attached}
16499 @tab @code{qAttached}
16500 @tab Querying remote process attach state.
16504 @section Implementing a Remote Stub
16506 @cindex debugging stub, example
16507 @cindex remote stub, example
16508 @cindex stub example, remote debugging
16509 The stub files provided with @value{GDBN} implement the target side of the
16510 communication protocol, and the @value{GDBN} side is implemented in the
16511 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16512 these subroutines to communicate, and ignore the details. (If you're
16513 implementing your own stub file, you can still ignore the details: start
16514 with one of the existing stub files. @file{sparc-stub.c} is the best
16515 organized, and therefore the easiest to read.)
16517 @cindex remote serial debugging, overview
16518 To debug a program running on another machine (the debugging
16519 @dfn{target} machine), you must first arrange for all the usual
16520 prerequisites for the program to run by itself. For example, for a C
16525 A startup routine to set up the C runtime environment; these usually
16526 have a name like @file{crt0}. The startup routine may be supplied by
16527 your hardware supplier, or you may have to write your own.
16530 A C subroutine library to support your program's
16531 subroutine calls, notably managing input and output.
16534 A way of getting your program to the other machine---for example, a
16535 download program. These are often supplied by the hardware
16536 manufacturer, but you may have to write your own from hardware
16540 The next step is to arrange for your program to use a serial port to
16541 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16542 machine). In general terms, the scheme looks like this:
16546 @value{GDBN} already understands how to use this protocol; when everything
16547 else is set up, you can simply use the @samp{target remote} command
16548 (@pxref{Targets,,Specifying a Debugging Target}).
16550 @item On the target,
16551 you must link with your program a few special-purpose subroutines that
16552 implement the @value{GDBN} remote serial protocol. The file containing these
16553 subroutines is called a @dfn{debugging stub}.
16555 On certain remote targets, you can use an auxiliary program
16556 @code{gdbserver} instead of linking a stub into your program.
16557 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16560 The debugging stub is specific to the architecture of the remote
16561 machine; for example, use @file{sparc-stub.c} to debug programs on
16564 @cindex remote serial stub list
16565 These working remote stubs are distributed with @value{GDBN}:
16570 @cindex @file{i386-stub.c}
16573 For Intel 386 and compatible architectures.
16576 @cindex @file{m68k-stub.c}
16577 @cindex Motorola 680x0
16579 For Motorola 680x0 architectures.
16582 @cindex @file{sh-stub.c}
16585 For Renesas SH architectures.
16588 @cindex @file{sparc-stub.c}
16590 For @sc{sparc} architectures.
16592 @item sparcl-stub.c
16593 @cindex @file{sparcl-stub.c}
16596 For Fujitsu @sc{sparclite} architectures.
16600 The @file{README} file in the @value{GDBN} distribution may list other
16601 recently added stubs.
16604 * Stub Contents:: What the stub can do for you
16605 * Bootstrapping:: What you must do for the stub
16606 * Debug Session:: Putting it all together
16609 @node Stub Contents
16610 @subsection What the Stub Can Do for You
16612 @cindex remote serial stub
16613 The debugging stub for your architecture supplies these three
16617 @item set_debug_traps
16618 @findex set_debug_traps
16619 @cindex remote serial stub, initialization
16620 This routine arranges for @code{handle_exception} to run when your
16621 program stops. You must call this subroutine explicitly near the
16622 beginning of your program.
16624 @item handle_exception
16625 @findex handle_exception
16626 @cindex remote serial stub, main routine
16627 This is the central workhorse, but your program never calls it
16628 explicitly---the setup code arranges for @code{handle_exception} to
16629 run when a trap is triggered.
16631 @code{handle_exception} takes control when your program stops during
16632 execution (for example, on a breakpoint), and mediates communications
16633 with @value{GDBN} on the host machine. This is where the communications
16634 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16635 representative on the target machine. It begins by sending summary
16636 information on the state of your program, then continues to execute,
16637 retrieving and transmitting any information @value{GDBN} needs, until you
16638 execute a @value{GDBN} command that makes your program resume; at that point,
16639 @code{handle_exception} returns control to your own code on the target
16643 @cindex @code{breakpoint} subroutine, remote
16644 Use this auxiliary subroutine to make your program contain a
16645 breakpoint. Depending on the particular situation, this may be the only
16646 way for @value{GDBN} to get control. For instance, if your target
16647 machine has some sort of interrupt button, you won't need to call this;
16648 pressing the interrupt button transfers control to
16649 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16650 simply receiving characters on the serial port may also trigger a trap;
16651 again, in that situation, you don't need to call @code{breakpoint} from
16652 your own program---simply running @samp{target remote} from the host
16653 @value{GDBN} session gets control.
16655 Call @code{breakpoint} if none of these is true, or if you simply want
16656 to make certain your program stops at a predetermined point for the
16657 start of your debugging session.
16660 @node Bootstrapping
16661 @subsection What You Must Do for the Stub
16663 @cindex remote stub, support routines
16664 The debugging stubs that come with @value{GDBN} are set up for a particular
16665 chip architecture, but they have no information about the rest of your
16666 debugging target machine.
16668 First of all you need to tell the stub how to communicate with the
16672 @item int getDebugChar()
16673 @findex getDebugChar
16674 Write this subroutine to read a single character from the serial port.
16675 It may be identical to @code{getchar} for your target system; a
16676 different name is used to allow you to distinguish the two if you wish.
16678 @item void putDebugChar(int)
16679 @findex putDebugChar
16680 Write this subroutine to write a single character to the serial port.
16681 It may be identical to @code{putchar} for your target system; a
16682 different name is used to allow you to distinguish the two if you wish.
16685 @cindex control C, and remote debugging
16686 @cindex interrupting remote targets
16687 If you want @value{GDBN} to be able to stop your program while it is
16688 running, you need to use an interrupt-driven serial driver, and arrange
16689 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16690 character). That is the character which @value{GDBN} uses to tell the
16691 remote system to stop.
16693 Getting the debugging target to return the proper status to @value{GDBN}
16694 probably requires changes to the standard stub; one quick and dirty way
16695 is to just execute a breakpoint instruction (the ``dirty'' part is that
16696 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16698 Other routines you need to supply are:
16701 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16702 @findex exceptionHandler
16703 Write this function to install @var{exception_address} in the exception
16704 handling tables. You need to do this because the stub does not have any
16705 way of knowing what the exception handling tables on your target system
16706 are like (for example, the processor's table might be in @sc{rom},
16707 containing entries which point to a table in @sc{ram}).
16708 @var{exception_number} is the exception number which should be changed;
16709 its meaning is architecture-dependent (for example, different numbers
16710 might represent divide by zero, misaligned access, etc). When this
16711 exception occurs, control should be transferred directly to
16712 @var{exception_address}, and the processor state (stack, registers,
16713 and so on) should be just as it is when a processor exception occurs. So if
16714 you want to use a jump instruction to reach @var{exception_address}, it
16715 should be a simple jump, not a jump to subroutine.
16717 For the 386, @var{exception_address} should be installed as an interrupt
16718 gate so that interrupts are masked while the handler runs. The gate
16719 should be at privilege level 0 (the most privileged level). The
16720 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16721 help from @code{exceptionHandler}.
16723 @item void flush_i_cache()
16724 @findex flush_i_cache
16725 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16726 instruction cache, if any, on your target machine. If there is no
16727 instruction cache, this subroutine may be a no-op.
16729 On target machines that have instruction caches, @value{GDBN} requires this
16730 function to make certain that the state of your program is stable.
16734 You must also make sure this library routine is available:
16737 @item void *memset(void *, int, int)
16739 This is the standard library function @code{memset} that sets an area of
16740 memory to a known value. If you have one of the free versions of
16741 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16742 either obtain it from your hardware manufacturer, or write your own.
16745 If you do not use the GNU C compiler, you may need other standard
16746 library subroutines as well; this varies from one stub to another,
16747 but in general the stubs are likely to use any of the common library
16748 subroutines which @code{@value{NGCC}} generates as inline code.
16751 @node Debug Session
16752 @subsection Putting it All Together
16754 @cindex remote serial debugging summary
16755 In summary, when your program is ready to debug, you must follow these
16760 Make sure you have defined the supporting low-level routines
16761 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16763 @code{getDebugChar}, @code{putDebugChar},
16764 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16768 Insert these lines near the top of your program:
16776 For the 680x0 stub only, you need to provide a variable called
16777 @code{exceptionHook}. Normally you just use:
16780 void (*exceptionHook)() = 0;
16784 but if before calling @code{set_debug_traps}, you set it to point to a
16785 function in your program, that function is called when
16786 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16787 error). The function indicated by @code{exceptionHook} is called with
16788 one parameter: an @code{int} which is the exception number.
16791 Compile and link together: your program, the @value{GDBN} debugging stub for
16792 your target architecture, and the supporting subroutines.
16795 Make sure you have a serial connection between your target machine and
16796 the @value{GDBN} host, and identify the serial port on the host.
16799 @c The "remote" target now provides a `load' command, so we should
16800 @c document that. FIXME.
16801 Download your program to your target machine (or get it there by
16802 whatever means the manufacturer provides), and start it.
16805 Start @value{GDBN} on the host, and connect to the target
16806 (@pxref{Connecting,,Connecting to a Remote Target}).
16810 @node Configurations
16811 @chapter Configuration-Specific Information
16813 While nearly all @value{GDBN} commands are available for all native and
16814 cross versions of the debugger, there are some exceptions. This chapter
16815 describes things that are only available in certain configurations.
16817 There are three major categories of configurations: native
16818 configurations, where the host and target are the same, embedded
16819 operating system configurations, which are usually the same for several
16820 different processor architectures, and bare embedded processors, which
16821 are quite different from each other.
16826 * Embedded Processors::
16833 This section describes details specific to particular native
16838 * BSD libkvm Interface:: Debugging BSD kernel memory images
16839 * SVR4 Process Information:: SVR4 process information
16840 * DJGPP Native:: Features specific to the DJGPP port
16841 * Cygwin Native:: Features specific to the Cygwin port
16842 * Hurd Native:: Features specific to @sc{gnu} Hurd
16843 * Neutrino:: Features specific to QNX Neutrino
16844 * Darwin:: Features specific to Darwin
16850 On HP-UX systems, if you refer to a function or variable name that
16851 begins with a dollar sign, @value{GDBN} searches for a user or system
16852 name first, before it searches for a convenience variable.
16855 @node BSD libkvm Interface
16856 @subsection BSD libkvm Interface
16859 @cindex kernel memory image
16860 @cindex kernel crash dump
16862 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
16863 interface that provides a uniform interface for accessing kernel virtual
16864 memory images, including live systems and crash dumps. @value{GDBN}
16865 uses this interface to allow you to debug live kernels and kernel crash
16866 dumps on many native BSD configurations. This is implemented as a
16867 special @code{kvm} debugging target. For debugging a live system, load
16868 the currently running kernel into @value{GDBN} and connect to the
16872 (@value{GDBP}) @b{target kvm}
16875 For debugging crash dumps, provide the file name of the crash dump as an
16879 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
16882 Once connected to the @code{kvm} target, the following commands are
16888 Set current context from the @dfn{Process Control Block} (PCB) address.
16891 Set current context from proc address. This command isn't available on
16892 modern FreeBSD systems.
16895 @node SVR4 Process Information
16896 @subsection SVR4 Process Information
16898 @cindex examine process image
16899 @cindex process info via @file{/proc}
16901 Many versions of SVR4 and compatible systems provide a facility called
16902 @samp{/proc} that can be used to examine the image of a running
16903 process using file-system subroutines. If @value{GDBN} is configured
16904 for an operating system with this facility, the command @code{info
16905 proc} is available to report information about the process running
16906 your program, or about any process running on your system. @code{info
16907 proc} works only on SVR4 systems that include the @code{procfs} code.
16908 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
16909 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
16915 @itemx info proc @var{process-id}
16916 Summarize available information about any running process. If a
16917 process ID is specified by @var{process-id}, display information about
16918 that process; otherwise display information about the program being
16919 debugged. The summary includes the debugged process ID, the command
16920 line used to invoke it, its current working directory, and its
16921 executable file's absolute file name.
16923 On some systems, @var{process-id} can be of the form
16924 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
16925 within a process. If the optional @var{pid} part is missing, it means
16926 a thread from the process being debugged (the leading @samp{/} still
16927 needs to be present, or else @value{GDBN} will interpret the number as
16928 a process ID rather than a thread ID).
16930 @item info proc mappings
16931 @cindex memory address space mappings
16932 Report the memory address space ranges accessible in the program, with
16933 information on whether the process has read, write, or execute access
16934 rights to each range. On @sc{gnu}/Linux systems, each memory range
16935 includes the object file which is mapped to that range, instead of the
16936 memory access rights to that range.
16938 @item info proc stat
16939 @itemx info proc status
16940 @cindex process detailed status information
16941 These subcommands are specific to @sc{gnu}/Linux systems. They show
16942 the process-related information, including the user ID and group ID;
16943 how many threads are there in the process; its virtual memory usage;
16944 the signals that are pending, blocked, and ignored; its TTY; its
16945 consumption of system and user time; its stack size; its @samp{nice}
16946 value; etc. For more information, see the @samp{proc} man page
16947 (type @kbd{man 5 proc} from your shell prompt).
16949 @item info proc all
16950 Show all the information about the process described under all of the
16951 above @code{info proc} subcommands.
16954 @comment These sub-options of 'info proc' were not included when
16955 @comment procfs.c was re-written. Keep their descriptions around
16956 @comment against the day when someone finds the time to put them back in.
16957 @kindex info proc times
16958 @item info proc times
16959 Starting time, user CPU time, and system CPU time for your program and
16962 @kindex info proc id
16964 Report on the process IDs related to your program: its own process ID,
16965 the ID of its parent, the process group ID, and the session ID.
16968 @item set procfs-trace
16969 @kindex set procfs-trace
16970 @cindex @code{procfs} API calls
16971 This command enables and disables tracing of @code{procfs} API calls.
16973 @item show procfs-trace
16974 @kindex show procfs-trace
16975 Show the current state of @code{procfs} API call tracing.
16977 @item set procfs-file @var{file}
16978 @kindex set procfs-file
16979 Tell @value{GDBN} to write @code{procfs} API trace to the named
16980 @var{file}. @value{GDBN} appends the trace info to the previous
16981 contents of the file. The default is to display the trace on the
16984 @item show procfs-file
16985 @kindex show procfs-file
16986 Show the file to which @code{procfs} API trace is written.
16988 @item proc-trace-entry
16989 @itemx proc-trace-exit
16990 @itemx proc-untrace-entry
16991 @itemx proc-untrace-exit
16992 @kindex proc-trace-entry
16993 @kindex proc-trace-exit
16994 @kindex proc-untrace-entry
16995 @kindex proc-untrace-exit
16996 These commands enable and disable tracing of entries into and exits
16997 from the @code{syscall} interface.
17000 @kindex info pidlist
17001 @cindex process list, QNX Neutrino
17002 For QNX Neutrino only, this command displays the list of all the
17003 processes and all the threads within each process.
17006 @kindex info meminfo
17007 @cindex mapinfo list, QNX Neutrino
17008 For QNX Neutrino only, this command displays the list of all mapinfos.
17012 @subsection Features for Debugging @sc{djgpp} Programs
17013 @cindex @sc{djgpp} debugging
17014 @cindex native @sc{djgpp} debugging
17015 @cindex MS-DOS-specific commands
17018 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17019 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17020 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17021 top of real-mode DOS systems and their emulations.
17023 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17024 defines a few commands specific to the @sc{djgpp} port. This
17025 subsection describes those commands.
17030 This is a prefix of @sc{djgpp}-specific commands which print
17031 information about the target system and important OS structures.
17034 @cindex MS-DOS system info
17035 @cindex free memory information (MS-DOS)
17036 @item info dos sysinfo
17037 This command displays assorted information about the underlying
17038 platform: the CPU type and features, the OS version and flavor, the
17039 DPMI version, and the available conventional and DPMI memory.
17044 @cindex segment descriptor tables
17045 @cindex descriptor tables display
17047 @itemx info dos ldt
17048 @itemx info dos idt
17049 These 3 commands display entries from, respectively, Global, Local,
17050 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17051 tables are data structures which store a descriptor for each segment
17052 that is currently in use. The segment's selector is an index into a
17053 descriptor table; the table entry for that index holds the
17054 descriptor's base address and limit, and its attributes and access
17057 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17058 segment (used for both data and the stack), and a DOS segment (which
17059 allows access to DOS/BIOS data structures and absolute addresses in
17060 conventional memory). However, the DPMI host will usually define
17061 additional segments in order to support the DPMI environment.
17063 @cindex garbled pointers
17064 These commands allow to display entries from the descriptor tables.
17065 Without an argument, all entries from the specified table are
17066 displayed. An argument, which should be an integer expression, means
17067 display a single entry whose index is given by the argument. For
17068 example, here's a convenient way to display information about the
17069 debugged program's data segment:
17072 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17073 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17077 This comes in handy when you want to see whether a pointer is outside
17078 the data segment's limit (i.e.@: @dfn{garbled}).
17080 @cindex page tables display (MS-DOS)
17082 @itemx info dos pte
17083 These two commands display entries from, respectively, the Page
17084 Directory and the Page Tables. Page Directories and Page Tables are
17085 data structures which control how virtual memory addresses are mapped
17086 into physical addresses. A Page Table includes an entry for every
17087 page of memory that is mapped into the program's address space; there
17088 may be several Page Tables, each one holding up to 4096 entries. A
17089 Page Directory has up to 4096 entries, one each for every Page Table
17090 that is currently in use.
17092 Without an argument, @kbd{info dos pde} displays the entire Page
17093 Directory, and @kbd{info dos pte} displays all the entries in all of
17094 the Page Tables. An argument, an integer expression, given to the
17095 @kbd{info dos pde} command means display only that entry from the Page
17096 Directory table. An argument given to the @kbd{info dos pte} command
17097 means display entries from a single Page Table, the one pointed to by
17098 the specified entry in the Page Directory.
17100 @cindex direct memory access (DMA) on MS-DOS
17101 These commands are useful when your program uses @dfn{DMA} (Direct
17102 Memory Access), which needs physical addresses to program the DMA
17105 These commands are supported only with some DPMI servers.
17107 @cindex physical address from linear address
17108 @item info dos address-pte @var{addr}
17109 This command displays the Page Table entry for a specified linear
17110 address. The argument @var{addr} is a linear address which should
17111 already have the appropriate segment's base address added to it,
17112 because this command accepts addresses which may belong to @emph{any}
17113 segment. For example, here's how to display the Page Table entry for
17114 the page where a variable @code{i} is stored:
17117 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17118 @exdent @code{Page Table entry for address 0x11a00d30:}
17119 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17123 This says that @code{i} is stored at offset @code{0xd30} from the page
17124 whose physical base address is @code{0x02698000}, and shows all the
17125 attributes of that page.
17127 Note that you must cast the addresses of variables to a @code{char *},
17128 since otherwise the value of @code{__djgpp_base_address}, the base
17129 address of all variables and functions in a @sc{djgpp} program, will
17130 be added using the rules of C pointer arithmetics: if @code{i} is
17131 declared an @code{int}, @value{GDBN} will add 4 times the value of
17132 @code{__djgpp_base_address} to the address of @code{i}.
17134 Here's another example, it displays the Page Table entry for the
17138 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17139 @exdent @code{Page Table entry for address 0x29110:}
17140 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17144 (The @code{+ 3} offset is because the transfer buffer's address is the
17145 3rd member of the @code{_go32_info_block} structure.) The output
17146 clearly shows that this DPMI server maps the addresses in conventional
17147 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17148 linear (@code{0x29110}) addresses are identical.
17150 This command is supported only with some DPMI servers.
17153 @cindex DOS serial data link, remote debugging
17154 In addition to native debugging, the DJGPP port supports remote
17155 debugging via a serial data link. The following commands are specific
17156 to remote serial debugging in the DJGPP port of @value{GDBN}.
17159 @kindex set com1base
17160 @kindex set com1irq
17161 @kindex set com2base
17162 @kindex set com2irq
17163 @kindex set com3base
17164 @kindex set com3irq
17165 @kindex set com4base
17166 @kindex set com4irq
17167 @item set com1base @var{addr}
17168 This command sets the base I/O port address of the @file{COM1} serial
17171 @item set com1irq @var{irq}
17172 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17173 for the @file{COM1} serial port.
17175 There are similar commands @samp{set com2base}, @samp{set com3irq},
17176 etc.@: for setting the port address and the @code{IRQ} lines for the
17179 @kindex show com1base
17180 @kindex show com1irq
17181 @kindex show com2base
17182 @kindex show com2irq
17183 @kindex show com3base
17184 @kindex show com3irq
17185 @kindex show com4base
17186 @kindex show com4irq
17187 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17188 display the current settings of the base address and the @code{IRQ}
17189 lines used by the COM ports.
17192 @kindex info serial
17193 @cindex DOS serial port status
17194 This command prints the status of the 4 DOS serial ports. For each
17195 port, it prints whether it's active or not, its I/O base address and
17196 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17197 counts of various errors encountered so far.
17201 @node Cygwin Native
17202 @subsection Features for Debugging MS Windows PE Executables
17203 @cindex MS Windows debugging
17204 @cindex native Cygwin debugging
17205 @cindex Cygwin-specific commands
17207 @value{GDBN} supports native debugging of MS Windows programs, including
17208 DLLs with and without symbolic debugging information.
17210 @cindex Ctrl-BREAK, MS-Windows
17211 @cindex interrupt debuggee on MS-Windows
17212 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17213 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17214 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17215 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17216 sequence, which can be used to interrupt the debuggee even if it
17219 There are various additional Cygwin-specific commands, described in
17220 this section. Working with DLLs that have no debugging symbols is
17221 described in @ref{Non-debug DLL Symbols}.
17226 This is a prefix of MS Windows-specific commands which print
17227 information about the target system and important OS structures.
17229 @item info w32 selector
17230 This command displays information returned by
17231 the Win32 API @code{GetThreadSelectorEntry} function.
17232 It takes an optional argument that is evaluated to
17233 a long value to give the information about this given selector.
17234 Without argument, this command displays information
17235 about the six segment registers.
17237 @item info w32 thread-information-block
17238 This command displays thread specific information stored in the
17239 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17240 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17244 This is a Cygwin-specific alias of @code{info shared}.
17246 @kindex dll-symbols
17248 This command loads symbols from a dll similarly to
17249 add-sym command but without the need to specify a base address.
17251 @kindex set cygwin-exceptions
17252 @cindex debugging the Cygwin DLL
17253 @cindex Cygwin DLL, debugging
17254 @item set cygwin-exceptions @var{mode}
17255 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17256 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17257 @value{GDBN} will delay recognition of exceptions, and may ignore some
17258 exceptions which seem to be caused by internal Cygwin DLL
17259 ``bookkeeping''. This option is meant primarily for debugging the
17260 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17261 @value{GDBN} users with false @code{SIGSEGV} signals.
17263 @kindex show cygwin-exceptions
17264 @item show cygwin-exceptions
17265 Displays whether @value{GDBN} will break on exceptions that happen
17266 inside the Cygwin DLL itself.
17268 @kindex set new-console
17269 @item set new-console @var{mode}
17270 If @var{mode} is @code{on} the debuggee will
17271 be started in a new console on next start.
17272 If @var{mode} is @code{off}, the debuggee will
17273 be started in the same console as the debugger.
17275 @kindex show new-console
17276 @item show new-console
17277 Displays whether a new console is used
17278 when the debuggee is started.
17280 @kindex set new-group
17281 @item set new-group @var{mode}
17282 This boolean value controls whether the debuggee should
17283 start a new group or stay in the same group as the debugger.
17284 This affects the way the Windows OS handles
17287 @kindex show new-group
17288 @item show new-group
17289 Displays current value of new-group boolean.
17291 @kindex set debugevents
17292 @item set debugevents
17293 This boolean value adds debug output concerning kernel events related
17294 to the debuggee seen by the debugger. This includes events that
17295 signal thread and process creation and exit, DLL loading and
17296 unloading, console interrupts, and debugging messages produced by the
17297 Windows @code{OutputDebugString} API call.
17299 @kindex set debugexec
17300 @item set debugexec
17301 This boolean value adds debug output concerning execute events
17302 (such as resume thread) seen by the debugger.
17304 @kindex set debugexceptions
17305 @item set debugexceptions
17306 This boolean value adds debug output concerning exceptions in the
17307 debuggee seen by the debugger.
17309 @kindex set debugmemory
17310 @item set debugmemory
17311 This boolean value adds debug output concerning debuggee memory reads
17312 and writes by the debugger.
17316 This boolean values specifies whether the debuggee is called
17317 via a shell or directly (default value is on).
17321 Displays if the debuggee will be started with a shell.
17326 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17329 @node Non-debug DLL Symbols
17330 @subsubsection Support for DLLs without Debugging Symbols
17331 @cindex DLLs with no debugging symbols
17332 @cindex Minimal symbols and DLLs
17334 Very often on windows, some of the DLLs that your program relies on do
17335 not include symbolic debugging information (for example,
17336 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17337 symbols in a DLL, it relies on the minimal amount of symbolic
17338 information contained in the DLL's export table. This section
17339 describes working with such symbols, known internally to @value{GDBN} as
17340 ``minimal symbols''.
17342 Note that before the debugged program has started execution, no DLLs
17343 will have been loaded. The easiest way around this problem is simply to
17344 start the program --- either by setting a breakpoint or letting the
17345 program run once to completion. It is also possible to force
17346 @value{GDBN} to load a particular DLL before starting the executable ---
17347 see the shared library information in @ref{Files}, or the
17348 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17349 explicitly loading symbols from a DLL with no debugging information will
17350 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17351 which may adversely affect symbol lookup performance.
17353 @subsubsection DLL Name Prefixes
17355 In keeping with the naming conventions used by the Microsoft debugging
17356 tools, DLL export symbols are made available with a prefix based on the
17357 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17358 also entered into the symbol table, so @code{CreateFileA} is often
17359 sufficient. In some cases there will be name clashes within a program
17360 (particularly if the executable itself includes full debugging symbols)
17361 necessitating the use of the fully qualified name when referring to the
17362 contents of the DLL. Use single-quotes around the name to avoid the
17363 exclamation mark (``!'') being interpreted as a language operator.
17365 Note that the internal name of the DLL may be all upper-case, even
17366 though the file name of the DLL is lower-case, or vice-versa. Since
17367 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17368 some confusion. If in doubt, try the @code{info functions} and
17369 @code{info variables} commands or even @code{maint print msymbols}
17370 (@pxref{Symbols}). Here's an example:
17373 (@value{GDBP}) info function CreateFileA
17374 All functions matching regular expression "CreateFileA":
17376 Non-debugging symbols:
17377 0x77e885f4 CreateFileA
17378 0x77e885f4 KERNEL32!CreateFileA
17382 (@value{GDBP}) info function !
17383 All functions matching regular expression "!":
17385 Non-debugging symbols:
17386 0x6100114c cygwin1!__assert
17387 0x61004034 cygwin1!_dll_crt0@@0
17388 0x61004240 cygwin1!dll_crt0(per_process *)
17392 @subsubsection Working with Minimal Symbols
17394 Symbols extracted from a DLL's export table do not contain very much
17395 type information. All that @value{GDBN} can do is guess whether a symbol
17396 refers to a function or variable depending on the linker section that
17397 contains the symbol. Also note that the actual contents of the memory
17398 contained in a DLL are not available unless the program is running. This
17399 means that you cannot examine the contents of a variable or disassemble
17400 a function within a DLL without a running program.
17402 Variables are generally treated as pointers and dereferenced
17403 automatically. For this reason, it is often necessary to prefix a
17404 variable name with the address-of operator (``&'') and provide explicit
17405 type information in the command. Here's an example of the type of
17409 (@value{GDBP}) print 'cygwin1!__argv'
17414 (@value{GDBP}) x 'cygwin1!__argv'
17415 0x10021610: "\230y\""
17418 And two possible solutions:
17421 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17422 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17426 (@value{GDBP}) x/2x &'cygwin1!__argv'
17427 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17428 (@value{GDBP}) x/x 0x10021608
17429 0x10021608: 0x0022fd98
17430 (@value{GDBP}) x/s 0x0022fd98
17431 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17434 Setting a break point within a DLL is possible even before the program
17435 starts execution. However, under these circumstances, @value{GDBN} can't
17436 examine the initial instructions of the function in order to skip the
17437 function's frame set-up code. You can work around this by using ``*&''
17438 to set the breakpoint at a raw memory address:
17441 (@value{GDBP}) break *&'python22!PyOS_Readline'
17442 Breakpoint 1 at 0x1e04eff0
17445 The author of these extensions is not entirely convinced that setting a
17446 break point within a shared DLL like @file{kernel32.dll} is completely
17450 @subsection Commands Specific to @sc{gnu} Hurd Systems
17451 @cindex @sc{gnu} Hurd debugging
17453 This subsection describes @value{GDBN} commands specific to the
17454 @sc{gnu} Hurd native debugging.
17459 @kindex set signals@r{, Hurd command}
17460 @kindex set sigs@r{, Hurd command}
17461 This command toggles the state of inferior signal interception by
17462 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17463 affected by this command. @code{sigs} is a shorthand alias for
17468 @kindex show signals@r{, Hurd command}
17469 @kindex show sigs@r{, Hurd command}
17470 Show the current state of intercepting inferior's signals.
17472 @item set signal-thread
17473 @itemx set sigthread
17474 @kindex set signal-thread
17475 @kindex set sigthread
17476 This command tells @value{GDBN} which thread is the @code{libc} signal
17477 thread. That thread is run when a signal is delivered to a running
17478 process. @code{set sigthread} is the shorthand alias of @code{set
17481 @item show signal-thread
17482 @itemx show sigthread
17483 @kindex show signal-thread
17484 @kindex show sigthread
17485 These two commands show which thread will run when the inferior is
17486 delivered a signal.
17489 @kindex set stopped@r{, Hurd command}
17490 This commands tells @value{GDBN} that the inferior process is stopped,
17491 as with the @code{SIGSTOP} signal. The stopped process can be
17492 continued by delivering a signal to it.
17495 @kindex show stopped@r{, Hurd command}
17496 This command shows whether @value{GDBN} thinks the debuggee is
17499 @item set exceptions
17500 @kindex set exceptions@r{, Hurd command}
17501 Use this command to turn off trapping of exceptions in the inferior.
17502 When exception trapping is off, neither breakpoints nor
17503 single-stepping will work. To restore the default, set exception
17506 @item show exceptions
17507 @kindex show exceptions@r{, Hurd command}
17508 Show the current state of trapping exceptions in the inferior.
17510 @item set task pause
17511 @kindex set task@r{, Hurd commands}
17512 @cindex task attributes (@sc{gnu} Hurd)
17513 @cindex pause current task (@sc{gnu} Hurd)
17514 This command toggles task suspension when @value{GDBN} has control.
17515 Setting it to on takes effect immediately, and the task is suspended
17516 whenever @value{GDBN} gets control. Setting it to off will take
17517 effect the next time the inferior is continued. If this option is set
17518 to off, you can use @code{set thread default pause on} or @code{set
17519 thread pause on} (see below) to pause individual threads.
17521 @item show task pause
17522 @kindex show task@r{, Hurd commands}
17523 Show the current state of task suspension.
17525 @item set task detach-suspend-count
17526 @cindex task suspend count
17527 @cindex detach from task, @sc{gnu} Hurd
17528 This command sets the suspend count the task will be left with when
17529 @value{GDBN} detaches from it.
17531 @item show task detach-suspend-count
17532 Show the suspend count the task will be left with when detaching.
17534 @item set task exception-port
17535 @itemx set task excp
17536 @cindex task exception port, @sc{gnu} Hurd
17537 This command sets the task exception port to which @value{GDBN} will
17538 forward exceptions. The argument should be the value of the @dfn{send
17539 rights} of the task. @code{set task excp} is a shorthand alias.
17541 @item set noninvasive
17542 @cindex noninvasive task options
17543 This command switches @value{GDBN} to a mode that is the least
17544 invasive as far as interfering with the inferior is concerned. This
17545 is the same as using @code{set task pause}, @code{set exceptions}, and
17546 @code{set signals} to values opposite to the defaults.
17548 @item info send-rights
17549 @itemx info receive-rights
17550 @itemx info port-rights
17551 @itemx info port-sets
17552 @itemx info dead-names
17555 @cindex send rights, @sc{gnu} Hurd
17556 @cindex receive rights, @sc{gnu} Hurd
17557 @cindex port rights, @sc{gnu} Hurd
17558 @cindex port sets, @sc{gnu} Hurd
17559 @cindex dead names, @sc{gnu} Hurd
17560 These commands display information about, respectively, send rights,
17561 receive rights, port rights, port sets, and dead names of a task.
17562 There are also shorthand aliases: @code{info ports} for @code{info
17563 port-rights} and @code{info psets} for @code{info port-sets}.
17565 @item set thread pause
17566 @kindex set thread@r{, Hurd command}
17567 @cindex thread properties, @sc{gnu} Hurd
17568 @cindex pause current thread (@sc{gnu} Hurd)
17569 This command toggles current thread suspension when @value{GDBN} has
17570 control. Setting it to on takes effect immediately, and the current
17571 thread is suspended whenever @value{GDBN} gets control. Setting it to
17572 off will take effect the next time the inferior is continued.
17573 Normally, this command has no effect, since when @value{GDBN} has
17574 control, the whole task is suspended. However, if you used @code{set
17575 task pause off} (see above), this command comes in handy to suspend
17576 only the current thread.
17578 @item show thread pause
17579 @kindex show thread@r{, Hurd command}
17580 This command shows the state of current thread suspension.
17582 @item set thread run
17583 This command sets whether the current thread is allowed to run.
17585 @item show thread run
17586 Show whether the current thread is allowed to run.
17588 @item set thread detach-suspend-count
17589 @cindex thread suspend count, @sc{gnu} Hurd
17590 @cindex detach from thread, @sc{gnu} Hurd
17591 This command sets the suspend count @value{GDBN} will leave on a
17592 thread when detaching. This number is relative to the suspend count
17593 found by @value{GDBN} when it notices the thread; use @code{set thread
17594 takeover-suspend-count} to force it to an absolute value.
17596 @item show thread detach-suspend-count
17597 Show the suspend count @value{GDBN} will leave on the thread when
17600 @item set thread exception-port
17601 @itemx set thread excp
17602 Set the thread exception port to which to forward exceptions. This
17603 overrides the port set by @code{set task exception-port} (see above).
17604 @code{set thread excp} is the shorthand alias.
17606 @item set thread takeover-suspend-count
17607 Normally, @value{GDBN}'s thread suspend counts are relative to the
17608 value @value{GDBN} finds when it notices each thread. This command
17609 changes the suspend counts to be absolute instead.
17611 @item set thread default
17612 @itemx show thread default
17613 @cindex thread default settings, @sc{gnu} Hurd
17614 Each of the above @code{set thread} commands has a @code{set thread
17615 default} counterpart (e.g., @code{set thread default pause}, @code{set
17616 thread default exception-port}, etc.). The @code{thread default}
17617 variety of commands sets the default thread properties for all
17618 threads; you can then change the properties of individual threads with
17619 the non-default commands.
17624 @subsection QNX Neutrino
17625 @cindex QNX Neutrino
17627 @value{GDBN} provides the following commands specific to the QNX
17631 @item set debug nto-debug
17632 @kindex set debug nto-debug
17633 When set to on, enables debugging messages specific to the QNX
17636 @item show debug nto-debug
17637 @kindex show debug nto-debug
17638 Show the current state of QNX Neutrino messages.
17645 @value{GDBN} provides the following commands specific to the Darwin target:
17648 @item set debug darwin @var{num}
17649 @kindex set debug darwin
17650 When set to a non zero value, enables debugging messages specific to
17651 the Darwin support. Higher values produce more verbose output.
17653 @item show debug darwin
17654 @kindex show debug darwin
17655 Show the current state of Darwin messages.
17657 @item set debug mach-o @var{num}
17658 @kindex set debug mach-o
17659 When set to a non zero value, enables debugging messages while
17660 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17661 file format used on Darwin for object and executable files.) Higher
17662 values produce more verbose output. This is a command to diagnose
17663 problems internal to @value{GDBN} and should not be needed in normal
17666 @item show debug mach-o
17667 @kindex show debug mach-o
17668 Show the current state of Mach-O file messages.
17670 @item set mach-exceptions on
17671 @itemx set mach-exceptions off
17672 @kindex set mach-exceptions
17673 On Darwin, faults are first reported as a Mach exception and are then
17674 mapped to a Posix signal. Use this command to turn on trapping of
17675 Mach exceptions in the inferior. This might be sometimes useful to
17676 better understand the cause of a fault. The default is off.
17678 @item show mach-exceptions
17679 @kindex show mach-exceptions
17680 Show the current state of exceptions trapping.
17685 @section Embedded Operating Systems
17687 This section describes configurations involving the debugging of
17688 embedded operating systems that are available for several different
17692 * VxWorks:: Using @value{GDBN} with VxWorks
17695 @value{GDBN} includes the ability to debug programs running on
17696 various real-time operating systems.
17699 @subsection Using @value{GDBN} with VxWorks
17705 @kindex target vxworks
17706 @item target vxworks @var{machinename}
17707 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17708 is the target system's machine name or IP address.
17712 On VxWorks, @code{load} links @var{filename} dynamically on the
17713 current target system as well as adding its symbols in @value{GDBN}.
17715 @value{GDBN} enables developers to spawn and debug tasks running on networked
17716 VxWorks targets from a Unix host. Already-running tasks spawned from
17717 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17718 both the Unix host and on the VxWorks target. The program
17719 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17720 installed with the name @code{vxgdb}, to distinguish it from a
17721 @value{GDBN} for debugging programs on the host itself.)
17724 @item VxWorks-timeout @var{args}
17725 @kindex vxworks-timeout
17726 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17727 This option is set by the user, and @var{args} represents the number of
17728 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17729 your VxWorks target is a slow software simulator or is on the far side
17730 of a thin network line.
17733 The following information on connecting to VxWorks was current when
17734 this manual was produced; newer releases of VxWorks may use revised
17737 @findex INCLUDE_RDB
17738 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17739 to include the remote debugging interface routines in the VxWorks
17740 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17741 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17742 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17743 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17744 information on configuring and remaking VxWorks, see the manufacturer's
17746 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17748 Once you have included @file{rdb.a} in your VxWorks system image and set
17749 your Unix execution search path to find @value{GDBN}, you are ready to
17750 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17751 @code{vxgdb}, depending on your installation).
17753 @value{GDBN} comes up showing the prompt:
17760 * VxWorks Connection:: Connecting to VxWorks
17761 * VxWorks Download:: VxWorks download
17762 * VxWorks Attach:: Running tasks
17765 @node VxWorks Connection
17766 @subsubsection Connecting to VxWorks
17768 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17769 network. To connect to a target whose host name is ``@code{tt}'', type:
17772 (vxgdb) target vxworks tt
17776 @value{GDBN} displays messages like these:
17779 Attaching remote machine across net...
17784 @value{GDBN} then attempts to read the symbol tables of any object modules
17785 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17786 these files by searching the directories listed in the command search
17787 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17788 to find an object file, it displays a message such as:
17791 prog.o: No such file or directory.
17794 When this happens, add the appropriate directory to the search path with
17795 the @value{GDBN} command @code{path}, and execute the @code{target}
17798 @node VxWorks Download
17799 @subsubsection VxWorks Download
17801 @cindex download to VxWorks
17802 If you have connected to the VxWorks target and you want to debug an
17803 object that has not yet been loaded, you can use the @value{GDBN}
17804 @code{load} command to download a file from Unix to VxWorks
17805 incrementally. The object file given as an argument to the @code{load}
17806 command is actually opened twice: first by the VxWorks target in order
17807 to download the code, then by @value{GDBN} in order to read the symbol
17808 table. This can lead to problems if the current working directories on
17809 the two systems differ. If both systems have NFS mounted the same
17810 filesystems, you can avoid these problems by using absolute paths.
17811 Otherwise, it is simplest to set the working directory on both systems
17812 to the directory in which the object file resides, and then to reference
17813 the file by its name, without any path. For instance, a program
17814 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17815 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17816 program, type this on VxWorks:
17819 -> cd "@var{vxpath}/vw/demo/rdb"
17823 Then, in @value{GDBN}, type:
17826 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17827 (vxgdb) load prog.o
17830 @value{GDBN} displays a response similar to this:
17833 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
17836 You can also use the @code{load} command to reload an object module
17837 after editing and recompiling the corresponding source file. Note that
17838 this makes @value{GDBN} delete all currently-defined breakpoints,
17839 auto-displays, and convenience variables, and to clear the value
17840 history. (This is necessary in order to preserve the integrity of
17841 debugger's data structures that reference the target system's symbol
17844 @node VxWorks Attach
17845 @subsubsection Running Tasks
17847 @cindex running VxWorks tasks
17848 You can also attach to an existing task using the @code{attach} command as
17852 (vxgdb) attach @var{task}
17856 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
17857 or suspended when you attach to it. Running tasks are suspended at
17858 the time of attachment.
17860 @node Embedded Processors
17861 @section Embedded Processors
17863 This section goes into details specific to particular embedded
17866 @cindex send command to simulator
17867 Whenever a specific embedded processor has a simulator, @value{GDBN}
17868 allows to send an arbitrary command to the simulator.
17871 @item sim @var{command}
17872 @kindex sim@r{, a command}
17873 Send an arbitrary @var{command} string to the simulator. Consult the
17874 documentation for the specific simulator in use for information about
17875 acceptable commands.
17881 * M32R/D:: Renesas M32R/D
17882 * M68K:: Motorola M68K
17883 * MicroBlaze:: Xilinx MicroBlaze
17884 * MIPS Embedded:: MIPS Embedded
17885 * OpenRISC 1000:: OpenRisc 1000
17886 * PA:: HP PA Embedded
17887 * PowerPC Embedded:: PowerPC Embedded
17888 * Sparclet:: Tsqware Sparclet
17889 * Sparclite:: Fujitsu Sparclite
17890 * Z8000:: Zilog Z8000
17893 * Super-H:: Renesas Super-H
17902 @item target rdi @var{dev}
17903 ARM Angel monitor, via RDI library interface to ADP protocol. You may
17904 use this target to communicate with both boards running the Angel
17905 monitor, or with the EmbeddedICE JTAG debug device.
17908 @item target rdp @var{dev}
17913 @value{GDBN} provides the following ARM-specific commands:
17916 @item set arm disassembler
17918 This commands selects from a list of disassembly styles. The
17919 @code{"std"} style is the standard style.
17921 @item show arm disassembler
17923 Show the current disassembly style.
17925 @item set arm apcs32
17926 @cindex ARM 32-bit mode
17927 This command toggles ARM operation mode between 32-bit and 26-bit.
17929 @item show arm apcs32
17930 Display the current usage of the ARM 32-bit mode.
17932 @item set arm fpu @var{fputype}
17933 This command sets the ARM floating-point unit (FPU) type. The
17934 argument @var{fputype} can be one of these:
17938 Determine the FPU type by querying the OS ABI.
17940 Software FPU, with mixed-endian doubles on little-endian ARM
17943 GCC-compiled FPA co-processor.
17945 Software FPU with pure-endian doubles.
17951 Show the current type of the FPU.
17954 This command forces @value{GDBN} to use the specified ABI.
17957 Show the currently used ABI.
17959 @item set arm fallback-mode (arm|thumb|auto)
17960 @value{GDBN} uses the symbol table, when available, to determine
17961 whether instructions are ARM or Thumb. This command controls
17962 @value{GDBN}'s default behavior when the symbol table is not
17963 available. The default is @samp{auto}, which causes @value{GDBN} to
17964 use the current execution mode (from the @code{T} bit in the @code{CPSR}
17967 @item show arm fallback-mode
17968 Show the current fallback instruction mode.
17970 @item set arm force-mode (arm|thumb|auto)
17971 This command overrides use of the symbol table to determine whether
17972 instructions are ARM or Thumb. The default is @samp{auto}, which
17973 causes @value{GDBN} to use the symbol table and then the setting
17974 of @samp{set arm fallback-mode}.
17976 @item show arm force-mode
17977 Show the current forced instruction mode.
17979 @item set debug arm
17980 Toggle whether to display ARM-specific debugging messages from the ARM
17981 target support subsystem.
17983 @item show debug arm
17984 Show whether ARM-specific debugging messages are enabled.
17987 The following commands are available when an ARM target is debugged
17988 using the RDI interface:
17991 @item rdilogfile @r{[}@var{file}@r{]}
17993 @cindex ADP (Angel Debugger Protocol) logging
17994 Set the filename for the ADP (Angel Debugger Protocol) packet log.
17995 With an argument, sets the log file to the specified @var{file}. With
17996 no argument, show the current log file name. The default log file is
17999 @item rdilogenable @r{[}@var{arg}@r{]}
18000 @kindex rdilogenable
18001 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18002 enables logging, with an argument 0 or @code{"no"} disables it. With
18003 no arguments displays the current setting. When logging is enabled,
18004 ADP packets exchanged between @value{GDBN} and the RDI target device
18005 are logged to a file.
18007 @item set rdiromatzero
18008 @kindex set rdiromatzero
18009 @cindex ROM at zero address, RDI
18010 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18011 vector catching is disabled, so that zero address can be used. If off
18012 (the default), vector catching is enabled. For this command to take
18013 effect, it needs to be invoked prior to the @code{target rdi} command.
18015 @item show rdiromatzero
18016 @kindex show rdiromatzero
18017 Show the current setting of ROM at zero address.
18019 @item set rdiheartbeat
18020 @kindex set rdiheartbeat
18021 @cindex RDI heartbeat
18022 Enable or disable RDI heartbeat packets. It is not recommended to
18023 turn on this option, since it confuses ARM and EPI JTAG interface, as
18024 well as the Angel monitor.
18026 @item show rdiheartbeat
18027 @kindex show rdiheartbeat
18028 Show the setting of RDI heartbeat packets.
18032 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18033 The @value{GDBN} ARM simulator accepts the following optional arguments.
18036 @item --swi-support=@var{type}
18037 Tell the simulator which SWI interfaces to support.
18038 @var{type} may be a comma separated list of the following values.
18039 The default value is @code{all}.
18052 @subsection Renesas M32R/D and M32R/SDI
18055 @kindex target m32r
18056 @item target m32r @var{dev}
18057 Renesas M32R/D ROM monitor.
18059 @kindex target m32rsdi
18060 @item target m32rsdi @var{dev}
18061 Renesas M32R SDI server, connected via parallel port to the board.
18064 The following @value{GDBN} commands are specific to the M32R monitor:
18067 @item set download-path @var{path}
18068 @kindex set download-path
18069 @cindex find downloadable @sc{srec} files (M32R)
18070 Set the default path for finding downloadable @sc{srec} files.
18072 @item show download-path
18073 @kindex show download-path
18074 Show the default path for downloadable @sc{srec} files.
18076 @item set board-address @var{addr}
18077 @kindex set board-address
18078 @cindex M32-EVA target board address
18079 Set the IP address for the M32R-EVA target board.
18081 @item show board-address
18082 @kindex show board-address
18083 Show the current IP address of the target board.
18085 @item set server-address @var{addr}
18086 @kindex set server-address
18087 @cindex download server address (M32R)
18088 Set the IP address for the download server, which is the @value{GDBN}'s
18091 @item show server-address
18092 @kindex show server-address
18093 Display the IP address of the download server.
18095 @item upload @r{[}@var{file}@r{]}
18096 @kindex upload@r{, M32R}
18097 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18098 upload capability. If no @var{file} argument is given, the current
18099 executable file is uploaded.
18101 @item tload @r{[}@var{file}@r{]}
18102 @kindex tload@r{, M32R}
18103 Test the @code{upload} command.
18106 The following commands are available for M32R/SDI:
18111 @cindex reset SDI connection, M32R
18112 This command resets the SDI connection.
18116 This command shows the SDI connection status.
18119 @kindex debug_chaos
18120 @cindex M32R/Chaos debugging
18121 Instructs the remote that M32R/Chaos debugging is to be used.
18123 @item use_debug_dma
18124 @kindex use_debug_dma
18125 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18128 @kindex use_mon_code
18129 Instructs the remote to use the MON_CODE method of accessing memory.
18132 @kindex use_ib_break
18133 Instructs the remote to set breakpoints by IB break.
18135 @item use_dbt_break
18136 @kindex use_dbt_break
18137 Instructs the remote to set breakpoints by DBT.
18143 The Motorola m68k configuration includes ColdFire support, and a
18144 target command for the following ROM monitor.
18148 @kindex target dbug
18149 @item target dbug @var{dev}
18150 dBUG ROM monitor for Motorola ColdFire.
18155 @subsection MicroBlaze
18156 @cindex Xilinx MicroBlaze
18157 @cindex XMD, Xilinx Microprocessor Debugger
18159 The MicroBlaze is a soft-core processor supported on various Xilinx
18160 FPGAs, such as Spartan or Virtex series. Boards with these processors
18161 usually have JTAG ports which connect to a host system running the Xilinx
18162 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18163 This host system is used to download the configuration bitstream to
18164 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18165 communicates with the target board using the JTAG interface and
18166 presents a @code{gdbserver} interface to the board. By default
18167 @code{xmd} uses port @code{1234}. (While it is possible to change
18168 this default port, it requires the use of undocumented @code{xmd}
18169 commands. Contact Xilinx support if you need to do this.)
18171 Use these GDB commands to connect to the MicroBlaze target processor.
18174 @item target remote :1234
18175 Use this command to connect to the target if you are running @value{GDBN}
18176 on the same system as @code{xmd}.
18178 @item target remote @var{xmd-host}:1234
18179 Use this command to connect to the target if it is connected to @code{xmd}
18180 running on a different system named @var{xmd-host}.
18183 Use this command to download a program to the MicroBlaze target.
18185 @item set debug microblaze @var{n}
18186 Enable MicroBlaze-specific debugging messages if non-zero.
18188 @item show debug microblaze @var{n}
18189 Show MicroBlaze-specific debugging level.
18192 @node MIPS Embedded
18193 @subsection MIPS Embedded
18195 @cindex MIPS boards
18196 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18197 MIPS board attached to a serial line. This is available when
18198 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18201 Use these @value{GDBN} commands to specify the connection to your target board:
18204 @item target mips @var{port}
18205 @kindex target mips @var{port}
18206 To run a program on the board, start up @code{@value{GDBP}} with the
18207 name of your program as the argument. To connect to the board, use the
18208 command @samp{target mips @var{port}}, where @var{port} is the name of
18209 the serial port connected to the board. If the program has not already
18210 been downloaded to the board, you may use the @code{load} command to
18211 download it. You can then use all the usual @value{GDBN} commands.
18213 For example, this sequence connects to the target board through a serial
18214 port, and loads and runs a program called @var{prog} through the
18218 host$ @value{GDBP} @var{prog}
18219 @value{GDBN} is free software and @dots{}
18220 (@value{GDBP}) target mips /dev/ttyb
18221 (@value{GDBP}) load @var{prog}
18225 @item target mips @var{hostname}:@var{portnumber}
18226 On some @value{GDBN} host configurations, you can specify a TCP
18227 connection (for instance, to a serial line managed by a terminal
18228 concentrator) instead of a serial port, using the syntax
18229 @samp{@var{hostname}:@var{portnumber}}.
18231 @item target pmon @var{port}
18232 @kindex target pmon @var{port}
18235 @item target ddb @var{port}
18236 @kindex target ddb @var{port}
18237 NEC's DDB variant of PMON for Vr4300.
18239 @item target lsi @var{port}
18240 @kindex target lsi @var{port}
18241 LSI variant of PMON.
18243 @kindex target r3900
18244 @item target r3900 @var{dev}
18245 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18247 @kindex target array
18248 @item target array @var{dev}
18249 Array Tech LSI33K RAID controller board.
18255 @value{GDBN} also supports these special commands for MIPS targets:
18258 @item set mipsfpu double
18259 @itemx set mipsfpu single
18260 @itemx set mipsfpu none
18261 @itemx set mipsfpu auto
18262 @itemx show mipsfpu
18263 @kindex set mipsfpu
18264 @kindex show mipsfpu
18265 @cindex MIPS remote floating point
18266 @cindex floating point, MIPS remote
18267 If your target board does not support the MIPS floating point
18268 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18269 need this, you may wish to put the command in your @value{GDBN} init
18270 file). This tells @value{GDBN} how to find the return value of
18271 functions which return floating point values. It also allows
18272 @value{GDBN} to avoid saving the floating point registers when calling
18273 functions on the board. If you are using a floating point coprocessor
18274 with only single precision floating point support, as on the @sc{r4650}
18275 processor, use the command @samp{set mipsfpu single}. The default
18276 double precision floating point coprocessor may be selected using
18277 @samp{set mipsfpu double}.
18279 In previous versions the only choices were double precision or no
18280 floating point, so @samp{set mipsfpu on} will select double precision
18281 and @samp{set mipsfpu off} will select no floating point.
18283 As usual, you can inquire about the @code{mipsfpu} variable with
18284 @samp{show mipsfpu}.
18286 @item set timeout @var{seconds}
18287 @itemx set retransmit-timeout @var{seconds}
18288 @itemx show timeout
18289 @itemx show retransmit-timeout
18290 @cindex @code{timeout}, MIPS protocol
18291 @cindex @code{retransmit-timeout}, MIPS protocol
18292 @kindex set timeout
18293 @kindex show timeout
18294 @kindex set retransmit-timeout
18295 @kindex show retransmit-timeout
18296 You can control the timeout used while waiting for a packet, in the MIPS
18297 remote protocol, with the @code{set timeout @var{seconds}} command. The
18298 default is 5 seconds. Similarly, you can control the timeout used while
18299 waiting for an acknowledgment of a packet with the @code{set
18300 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18301 You can inspect both values with @code{show timeout} and @code{show
18302 retransmit-timeout}. (These commands are @emph{only} available when
18303 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18305 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18306 is waiting for your program to stop. In that case, @value{GDBN} waits
18307 forever because it has no way of knowing how long the program is going
18308 to run before stopping.
18310 @item set syn-garbage-limit @var{num}
18311 @kindex set syn-garbage-limit@r{, MIPS remote}
18312 @cindex synchronize with remote MIPS target
18313 Limit the maximum number of characters @value{GDBN} should ignore when
18314 it tries to synchronize with the remote target. The default is 10
18315 characters. Setting the limit to -1 means there's no limit.
18317 @item show syn-garbage-limit
18318 @kindex show syn-garbage-limit@r{, MIPS remote}
18319 Show the current limit on the number of characters to ignore when
18320 trying to synchronize with the remote system.
18322 @item set monitor-prompt @var{prompt}
18323 @kindex set monitor-prompt@r{, MIPS remote}
18324 @cindex remote monitor prompt
18325 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18326 remote monitor. The default depends on the target:
18336 @item show monitor-prompt
18337 @kindex show monitor-prompt@r{, MIPS remote}
18338 Show the current strings @value{GDBN} expects as the prompt from the
18341 @item set monitor-warnings
18342 @kindex set monitor-warnings@r{, MIPS remote}
18343 Enable or disable monitor warnings about hardware breakpoints. This
18344 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18345 display warning messages whose codes are returned by the @code{lsi}
18346 PMON monitor for breakpoint commands.
18348 @item show monitor-warnings
18349 @kindex show monitor-warnings@r{, MIPS remote}
18350 Show the current setting of printing monitor warnings.
18352 @item pmon @var{command}
18353 @kindex pmon@r{, MIPS remote}
18354 @cindex send PMON command
18355 This command allows sending an arbitrary @var{command} string to the
18356 monitor. The monitor must be in debug mode for this to work.
18359 @node OpenRISC 1000
18360 @subsection OpenRISC 1000
18361 @cindex OpenRISC 1000
18363 @cindex or1k boards
18364 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18365 about platform and commands.
18369 @kindex target jtag
18370 @item target jtag jtag://@var{host}:@var{port}
18372 Connects to remote JTAG server.
18373 JTAG remote server can be either an or1ksim or JTAG server,
18374 connected via parallel port to the board.
18376 Example: @code{target jtag jtag://localhost:9999}
18379 @item or1ksim @var{command}
18380 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18381 Simulator, proprietary commands can be executed.
18383 @kindex info or1k spr
18384 @item info or1k spr
18385 Displays spr groups.
18387 @item info or1k spr @var{group}
18388 @itemx info or1k spr @var{groupno}
18389 Displays register names in selected group.
18391 @item info or1k spr @var{group} @var{register}
18392 @itemx info or1k spr @var{register}
18393 @itemx info or1k spr @var{groupno} @var{registerno}
18394 @itemx info or1k spr @var{registerno}
18395 Shows information about specified spr register.
18398 @item spr @var{group} @var{register} @var{value}
18399 @itemx spr @var{register @var{value}}
18400 @itemx spr @var{groupno} @var{registerno @var{value}}
18401 @itemx spr @var{registerno @var{value}}
18402 Writes @var{value} to specified spr register.
18405 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18406 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18407 program execution and is thus much faster. Hardware breakpoints/watchpoint
18408 triggers can be set using:
18411 Load effective address/data
18413 Store effective address/data
18415 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18420 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18421 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18423 @code{htrace} commands:
18424 @cindex OpenRISC 1000 htrace
18427 @item hwatch @var{conditional}
18428 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18429 or Data. For example:
18431 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18433 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18437 Display information about current HW trace configuration.
18439 @item htrace trigger @var{conditional}
18440 Set starting criteria for HW trace.
18442 @item htrace qualifier @var{conditional}
18443 Set acquisition qualifier for HW trace.
18445 @item htrace stop @var{conditional}
18446 Set HW trace stopping criteria.
18448 @item htrace record [@var{data}]*
18449 Selects the data to be recorded, when qualifier is met and HW trace was
18452 @item htrace enable
18453 @itemx htrace disable
18454 Enables/disables the HW trace.
18456 @item htrace rewind [@var{filename}]
18457 Clears currently recorded trace data.
18459 If filename is specified, new trace file is made and any newly collected data
18460 will be written there.
18462 @item htrace print [@var{start} [@var{len}]]
18463 Prints trace buffer, using current record configuration.
18465 @item htrace mode continuous
18466 Set continuous trace mode.
18468 @item htrace mode suspend
18469 Set suspend trace mode.
18473 @node PowerPC Embedded
18474 @subsection PowerPC Embedded
18476 @value{GDBN} provides the following PowerPC-specific commands:
18479 @kindex set powerpc
18480 @item set powerpc soft-float
18481 @itemx show powerpc soft-float
18482 Force @value{GDBN} to use (or not use) a software floating point calling
18483 convention. By default, @value{GDBN} selects the calling convention based
18484 on the selected architecture and the provided executable file.
18486 @item set powerpc vector-abi
18487 @itemx show powerpc vector-abi
18488 Force @value{GDBN} to use the specified calling convention for vector
18489 arguments and return values. The valid options are @samp{auto};
18490 @samp{generic}, to avoid vector registers even if they are present;
18491 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18492 registers. By default, @value{GDBN} selects the calling convention
18493 based on the selected architecture and the provided executable file.
18495 @kindex target dink32
18496 @item target dink32 @var{dev}
18497 DINK32 ROM monitor.
18499 @kindex target ppcbug
18500 @item target ppcbug @var{dev}
18501 @kindex target ppcbug1
18502 @item target ppcbug1 @var{dev}
18503 PPCBUG ROM monitor for PowerPC.
18506 @item target sds @var{dev}
18507 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18510 @cindex SDS protocol
18511 The following commands specific to the SDS protocol are supported
18515 @item set sdstimeout @var{nsec}
18516 @kindex set sdstimeout
18517 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18518 default is 2 seconds.
18520 @item show sdstimeout
18521 @kindex show sdstimeout
18522 Show the current value of the SDS timeout.
18524 @item sds @var{command}
18525 @kindex sds@r{, a command}
18526 Send the specified @var{command} string to the SDS monitor.
18531 @subsection HP PA Embedded
18535 @kindex target op50n
18536 @item target op50n @var{dev}
18537 OP50N monitor, running on an OKI HPPA board.
18539 @kindex target w89k
18540 @item target w89k @var{dev}
18541 W89K monitor, running on a Winbond HPPA board.
18546 @subsection Tsqware Sparclet
18550 @value{GDBN} enables developers to debug tasks running on
18551 Sparclet targets from a Unix host.
18552 @value{GDBN} uses code that runs on
18553 both the Unix host and on the Sparclet target. The program
18554 @code{@value{GDBP}} is installed and executed on the Unix host.
18557 @item remotetimeout @var{args}
18558 @kindex remotetimeout
18559 @value{GDBN} supports the option @code{remotetimeout}.
18560 This option is set by the user, and @var{args} represents the number of
18561 seconds @value{GDBN} waits for responses.
18564 @cindex compiling, on Sparclet
18565 When compiling for debugging, include the options @samp{-g} to get debug
18566 information and @samp{-Ttext} to relocate the program to where you wish to
18567 load it on the target. You may also want to add the options @samp{-n} or
18568 @samp{-N} in order to reduce the size of the sections. Example:
18571 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18574 You can use @code{objdump} to verify that the addresses are what you intended:
18577 sparclet-aout-objdump --headers --syms prog
18580 @cindex running, on Sparclet
18582 your Unix execution search path to find @value{GDBN}, you are ready to
18583 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18584 (or @code{sparclet-aout-gdb}, depending on your installation).
18586 @value{GDBN} comes up showing the prompt:
18593 * Sparclet File:: Setting the file to debug
18594 * Sparclet Connection:: Connecting to Sparclet
18595 * Sparclet Download:: Sparclet download
18596 * Sparclet Execution:: Running and debugging
18599 @node Sparclet File
18600 @subsubsection Setting File to Debug
18602 The @value{GDBN} command @code{file} lets you choose with program to debug.
18605 (gdbslet) file prog
18609 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18610 @value{GDBN} locates
18611 the file by searching the directories listed in the command search
18613 If the file was compiled with debug information (option @samp{-g}), source
18614 files will be searched as well.
18615 @value{GDBN} locates
18616 the source files by searching the directories listed in the directory search
18617 path (@pxref{Environment, ,Your Program's Environment}).
18619 to find a file, it displays a message such as:
18622 prog: No such file or directory.
18625 When this happens, add the appropriate directories to the search paths with
18626 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18627 @code{target} command again.
18629 @node Sparclet Connection
18630 @subsubsection Connecting to Sparclet
18632 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18633 To connect to a target on serial port ``@code{ttya}'', type:
18636 (gdbslet) target sparclet /dev/ttya
18637 Remote target sparclet connected to /dev/ttya
18638 main () at ../prog.c:3
18642 @value{GDBN} displays messages like these:
18648 @node Sparclet Download
18649 @subsubsection Sparclet Download
18651 @cindex download to Sparclet
18652 Once connected to the Sparclet target,
18653 you can use the @value{GDBN}
18654 @code{load} command to download the file from the host to the target.
18655 The file name and load offset should be given as arguments to the @code{load}
18657 Since the file format is aout, the program must be loaded to the starting
18658 address. You can use @code{objdump} to find out what this value is. The load
18659 offset is an offset which is added to the VMA (virtual memory address)
18660 of each of the file's sections.
18661 For instance, if the program
18662 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18663 and bss at 0x12010170, in @value{GDBN}, type:
18666 (gdbslet) load prog 0x12010000
18667 Loading section .text, size 0xdb0 vma 0x12010000
18670 If the code is loaded at a different address then what the program was linked
18671 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18672 to tell @value{GDBN} where to map the symbol table.
18674 @node Sparclet Execution
18675 @subsubsection Running and Debugging
18677 @cindex running and debugging Sparclet programs
18678 You can now begin debugging the task using @value{GDBN}'s execution control
18679 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18680 manual for the list of commands.
18684 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18686 Starting program: prog
18687 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18688 3 char *symarg = 0;
18690 4 char *execarg = "hello!";
18695 @subsection Fujitsu Sparclite
18699 @kindex target sparclite
18700 @item target sparclite @var{dev}
18701 Fujitsu sparclite boards, used only for the purpose of loading.
18702 You must use an additional command to debug the program.
18703 For example: target remote @var{dev} using @value{GDBN} standard
18709 @subsection Zilog Z8000
18712 @cindex simulator, Z8000
18713 @cindex Zilog Z8000 simulator
18715 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18718 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18719 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18720 segmented variant). The simulator recognizes which architecture is
18721 appropriate by inspecting the object code.
18724 @item target sim @var{args}
18726 @kindex target sim@r{, with Z8000}
18727 Debug programs on a simulated CPU. If the simulator supports setup
18728 options, specify them via @var{args}.
18732 After specifying this target, you can debug programs for the simulated
18733 CPU in the same style as programs for your host computer; use the
18734 @code{file} command to load a new program image, the @code{run} command
18735 to run your program, and so on.
18737 As well as making available all the usual machine registers
18738 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18739 additional items of information as specially named registers:
18744 Counts clock-ticks in the simulator.
18747 Counts instructions run in the simulator.
18750 Execution time in 60ths of a second.
18754 You can refer to these values in @value{GDBN} expressions with the usual
18755 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18756 conditional breakpoint that suspends only after at least 5000
18757 simulated clock ticks.
18760 @subsection Atmel AVR
18763 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18764 following AVR-specific commands:
18767 @item info io_registers
18768 @kindex info io_registers@r{, AVR}
18769 @cindex I/O registers (Atmel AVR)
18770 This command displays information about the AVR I/O registers. For
18771 each register, @value{GDBN} prints its number and value.
18778 When configured for debugging CRIS, @value{GDBN} provides the
18779 following CRIS-specific commands:
18782 @item set cris-version @var{ver}
18783 @cindex CRIS version
18784 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18785 The CRIS version affects register names and sizes. This command is useful in
18786 case autodetection of the CRIS version fails.
18788 @item show cris-version
18789 Show the current CRIS version.
18791 @item set cris-dwarf2-cfi
18792 @cindex DWARF-2 CFI and CRIS
18793 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18794 Change to @samp{off} when using @code{gcc-cris} whose version is below
18797 @item show cris-dwarf2-cfi
18798 Show the current state of using DWARF-2 CFI.
18800 @item set cris-mode @var{mode}
18802 Set the current CRIS mode to @var{mode}. It should only be changed when
18803 debugging in guru mode, in which case it should be set to
18804 @samp{guru} (the default is @samp{normal}).
18806 @item show cris-mode
18807 Show the current CRIS mode.
18811 @subsection Renesas Super-H
18814 For the Renesas Super-H processor, @value{GDBN} provides these
18819 @kindex regs@r{, Super-H}
18820 Show the values of all Super-H registers.
18822 @item set sh calling-convention @var{convention}
18823 @kindex set sh calling-convention
18824 Set the calling-convention used when calling functions from @value{GDBN}.
18825 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
18826 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
18827 convention. If the DWARF-2 information of the called function specifies
18828 that the function follows the Renesas calling convention, the function
18829 is called using the Renesas calling convention. If the calling convention
18830 is set to @samp{renesas}, the Renesas calling convention is always used,
18831 regardless of the DWARF-2 information. This can be used to override the
18832 default of @samp{gcc} if debug information is missing, or the compiler
18833 does not emit the DWARF-2 calling convention entry for a function.
18835 @item show sh calling-convention
18836 @kindex show sh calling-convention
18837 Show the current calling convention setting.
18842 @node Architectures
18843 @section Architectures
18845 This section describes characteristics of architectures that affect
18846 all uses of @value{GDBN} with the architecture, both native and cross.
18853 * HPPA:: HP PA architecture
18854 * SPU:: Cell Broadband Engine SPU architecture
18859 @subsection x86 Architecture-specific Issues
18862 @item set struct-convention @var{mode}
18863 @kindex set struct-convention
18864 @cindex struct return convention
18865 @cindex struct/union returned in registers
18866 Set the convention used by the inferior to return @code{struct}s and
18867 @code{union}s from functions to @var{mode}. Possible values of
18868 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
18869 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
18870 are returned on the stack, while @code{"reg"} means that a
18871 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
18872 be returned in a register.
18874 @item show struct-convention
18875 @kindex show struct-convention
18876 Show the current setting of the convention to return @code{struct}s
18885 @kindex set rstack_high_address
18886 @cindex AMD 29K register stack
18887 @cindex register stack, AMD29K
18888 @item set rstack_high_address @var{address}
18889 On AMD 29000 family processors, registers are saved in a separate
18890 @dfn{register stack}. There is no way for @value{GDBN} to determine the
18891 extent of this stack. Normally, @value{GDBN} just assumes that the
18892 stack is ``large enough''. This may result in @value{GDBN} referencing
18893 memory locations that do not exist. If necessary, you can get around
18894 this problem by specifying the ending address of the register stack with
18895 the @code{set rstack_high_address} command. The argument should be an
18896 address, which you probably want to precede with @samp{0x} to specify in
18899 @kindex show rstack_high_address
18900 @item show rstack_high_address
18901 Display the current limit of the register stack, on AMD 29000 family
18909 See the following section.
18914 @cindex stack on Alpha
18915 @cindex stack on MIPS
18916 @cindex Alpha stack
18918 Alpha- and MIPS-based computers use an unusual stack frame, which
18919 sometimes requires @value{GDBN} to search backward in the object code to
18920 find the beginning of a function.
18922 @cindex response time, MIPS debugging
18923 To improve response time (especially for embedded applications, where
18924 @value{GDBN} may be restricted to a slow serial line for this search)
18925 you may want to limit the size of this search, using one of these
18929 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
18930 @item set heuristic-fence-post @var{limit}
18931 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
18932 search for the beginning of a function. A value of @var{0} (the
18933 default) means there is no limit. However, except for @var{0}, the
18934 larger the limit the more bytes @code{heuristic-fence-post} must search
18935 and therefore the longer it takes to run. You should only need to use
18936 this command when debugging a stripped executable.
18938 @item show heuristic-fence-post
18939 Display the current limit.
18943 These commands are available @emph{only} when @value{GDBN} is configured
18944 for debugging programs on Alpha or MIPS processors.
18946 Several MIPS-specific commands are available when debugging MIPS
18950 @item set mips abi @var{arg}
18951 @kindex set mips abi
18952 @cindex set ABI for MIPS
18953 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
18954 values of @var{arg} are:
18958 The default ABI associated with the current binary (this is the
18969 @item show mips abi
18970 @kindex show mips abi
18971 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
18974 @itemx show mipsfpu
18975 @xref{MIPS Embedded, set mipsfpu}.
18977 @item set mips mask-address @var{arg}
18978 @kindex set mips mask-address
18979 @cindex MIPS addresses, masking
18980 This command determines whether the most-significant 32 bits of 64-bit
18981 MIPS addresses are masked off. The argument @var{arg} can be
18982 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
18983 setting, which lets @value{GDBN} determine the correct value.
18985 @item show mips mask-address
18986 @kindex show mips mask-address
18987 Show whether the upper 32 bits of MIPS addresses are masked off or
18990 @item set remote-mips64-transfers-32bit-regs
18991 @kindex set remote-mips64-transfers-32bit-regs
18992 This command controls compatibility with 64-bit MIPS targets that
18993 transfer data in 32-bit quantities. If you have an old MIPS 64 target
18994 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
18995 and 64 bits for other registers, set this option to @samp{on}.
18997 @item show remote-mips64-transfers-32bit-regs
18998 @kindex show remote-mips64-transfers-32bit-regs
18999 Show the current setting of compatibility with older MIPS 64 targets.
19001 @item set debug mips
19002 @kindex set debug mips
19003 This command turns on and off debugging messages for the MIPS-specific
19004 target code in @value{GDBN}.
19006 @item show debug mips
19007 @kindex show debug mips
19008 Show the current setting of MIPS debugging messages.
19014 @cindex HPPA support
19016 When @value{GDBN} is debugging the HP PA architecture, it provides the
19017 following special commands:
19020 @item set debug hppa
19021 @kindex set debug hppa
19022 This command determines whether HPPA architecture-specific debugging
19023 messages are to be displayed.
19025 @item show debug hppa
19026 Show whether HPPA debugging messages are displayed.
19028 @item maint print unwind @var{address}
19029 @kindex maint print unwind@r{, HPPA}
19030 This command displays the contents of the unwind table entry at the
19031 given @var{address}.
19037 @subsection Cell Broadband Engine SPU architecture
19038 @cindex Cell Broadband Engine
19041 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19042 it provides the following special commands:
19045 @item info spu event
19047 Display SPU event facility status. Shows current event mask
19048 and pending event status.
19050 @item info spu signal
19051 Display SPU signal notification facility status. Shows pending
19052 signal-control word and signal notification mode of both signal
19053 notification channels.
19055 @item info spu mailbox
19056 Display SPU mailbox facility status. Shows all pending entries,
19057 in order of processing, in each of the SPU Write Outbound,
19058 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19061 Display MFC DMA status. Shows all pending commands in the MFC
19062 DMA queue. For each entry, opcode, tag, class IDs, effective
19063 and local store addresses and transfer size are shown.
19065 @item info spu proxydma
19066 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19067 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19068 and local store addresses and transfer size are shown.
19072 When @value{GDBN} is debugging a combined PowerPC/SPU application
19073 on the Cell Broadband Engine, it provides in addition the following
19077 @item set spu stop-on-load @var{arg}
19079 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19080 will give control to the user when a new SPE thread enters its @code{main}
19081 function. The default is @code{off}.
19083 @item show spu stop-on-load
19085 Show whether to stop for new SPE threads.
19087 @item set spu auto-flush-cache @var{arg}
19088 Set whether to automatically flush the software-managed cache. When set to
19089 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19090 cache to be flushed whenever SPE execution stops. This provides a consistent
19091 view of PowerPC memory that is accessed via the cache. If an application
19092 does not use the software-managed cache, this option has no effect.
19094 @item show spu auto-flush-cache
19095 Show whether to automatically flush the software-managed cache.
19100 @subsection PowerPC
19101 @cindex PowerPC architecture
19103 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19104 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19105 numbers stored in the floating point registers. These values must be stored
19106 in two consecutive registers, always starting at an even register like
19107 @code{f0} or @code{f2}.
19109 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19110 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19111 @code{f2} and @code{f3} for @code{$dl1} and so on.
19113 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19114 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19117 @node Controlling GDB
19118 @chapter Controlling @value{GDBN}
19120 You can alter the way @value{GDBN} interacts with you by using the
19121 @code{set} command. For commands controlling how @value{GDBN} displays
19122 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19127 * Editing:: Command editing
19128 * Command History:: Command history
19129 * Screen Size:: Screen size
19130 * Numbers:: Numbers
19131 * ABI:: Configuring the current ABI
19132 * Messages/Warnings:: Optional warnings and messages
19133 * Debugging Output:: Optional messages about internal happenings
19134 * Other Misc Settings:: Other Miscellaneous Settings
19142 @value{GDBN} indicates its readiness to read a command by printing a string
19143 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19144 can change the prompt string with the @code{set prompt} command. For
19145 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19146 the prompt in one of the @value{GDBN} sessions so that you can always tell
19147 which one you are talking to.
19149 @emph{Note:} @code{set prompt} does not add a space for you after the
19150 prompt you set. This allows you to set a prompt which ends in a space
19151 or a prompt that does not.
19155 @item set prompt @var{newprompt}
19156 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19158 @kindex show prompt
19160 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19164 @section Command Editing
19166 @cindex command line editing
19168 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19169 @sc{gnu} library provides consistent behavior for programs which provide a
19170 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19171 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19172 substitution, and a storage and recall of command history across
19173 debugging sessions.
19175 You may control the behavior of command line editing in @value{GDBN} with the
19176 command @code{set}.
19179 @kindex set editing
19182 @itemx set editing on
19183 Enable command line editing (enabled by default).
19185 @item set editing off
19186 Disable command line editing.
19188 @kindex show editing
19190 Show whether command line editing is enabled.
19193 @xref{Command Line Editing}, for more details about the Readline
19194 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19195 encouraged to read that chapter.
19197 @node Command History
19198 @section Command History
19199 @cindex command history
19201 @value{GDBN} can keep track of the commands you type during your
19202 debugging sessions, so that you can be certain of precisely what
19203 happened. Use these commands to manage the @value{GDBN} command
19206 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19207 package, to provide the history facility. @xref{Using History
19208 Interactively}, for the detailed description of the History library.
19210 To issue a command to @value{GDBN} without affecting certain aspects of
19211 the state which is seen by users, prefix it with @samp{server }
19212 (@pxref{Server Prefix}). This
19213 means that this command will not affect the command history, nor will it
19214 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19215 pressed on a line by itself.
19217 @cindex @code{server}, command prefix
19218 The server prefix does not affect the recording of values into the value
19219 history; to print a value without recording it into the value history,
19220 use the @code{output} command instead of the @code{print} command.
19222 Here is the description of @value{GDBN} commands related to command
19226 @cindex history substitution
19227 @cindex history file
19228 @kindex set history filename
19229 @cindex @env{GDBHISTFILE}, environment variable
19230 @item set history filename @var{fname}
19231 Set the name of the @value{GDBN} command history file to @var{fname}.
19232 This is the file where @value{GDBN} reads an initial command history
19233 list, and where it writes the command history from this session when it
19234 exits. You can access this list through history expansion or through
19235 the history command editing characters listed below. This file defaults
19236 to the value of the environment variable @code{GDBHISTFILE}, or to
19237 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19240 @cindex save command history
19241 @kindex set history save
19242 @item set history save
19243 @itemx set history save on
19244 Record command history in a file, whose name may be specified with the
19245 @code{set history filename} command. By default, this option is disabled.
19247 @item set history save off
19248 Stop recording command history in a file.
19250 @cindex history size
19251 @kindex set history size
19252 @cindex @env{HISTSIZE}, environment variable
19253 @item set history size @var{size}
19254 Set the number of commands which @value{GDBN} keeps in its history list.
19255 This defaults to the value of the environment variable
19256 @code{HISTSIZE}, or to 256 if this variable is not set.
19259 History expansion assigns special meaning to the character @kbd{!}.
19260 @xref{Event Designators}, for more details.
19262 @cindex history expansion, turn on/off
19263 Since @kbd{!} is also the logical not operator in C, history expansion
19264 is off by default. If you decide to enable history expansion with the
19265 @code{set history expansion on} command, you may sometimes need to
19266 follow @kbd{!} (when it is used as logical not, in an expression) with
19267 a space or a tab to prevent it from being expanded. The readline
19268 history facilities do not attempt substitution on the strings
19269 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19271 The commands to control history expansion are:
19274 @item set history expansion on
19275 @itemx set history expansion
19276 @kindex set history expansion
19277 Enable history expansion. History expansion is off by default.
19279 @item set history expansion off
19280 Disable history expansion.
19283 @kindex show history
19285 @itemx show history filename
19286 @itemx show history save
19287 @itemx show history size
19288 @itemx show history expansion
19289 These commands display the state of the @value{GDBN} history parameters.
19290 @code{show history} by itself displays all four states.
19295 @kindex show commands
19296 @cindex show last commands
19297 @cindex display command history
19298 @item show commands
19299 Display the last ten commands in the command history.
19301 @item show commands @var{n}
19302 Print ten commands centered on command number @var{n}.
19304 @item show commands +
19305 Print ten commands just after the commands last printed.
19309 @section Screen Size
19310 @cindex size of screen
19311 @cindex pauses in output
19313 Certain commands to @value{GDBN} may produce large amounts of
19314 information output to the screen. To help you read all of it,
19315 @value{GDBN} pauses and asks you for input at the end of each page of
19316 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19317 to discard the remaining output. Also, the screen width setting
19318 determines when to wrap lines of output. Depending on what is being
19319 printed, @value{GDBN} tries to break the line at a readable place,
19320 rather than simply letting it overflow onto the following line.
19322 Normally @value{GDBN} knows the size of the screen from the terminal
19323 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19324 together with the value of the @code{TERM} environment variable and the
19325 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19326 you can override it with the @code{set height} and @code{set
19333 @kindex show height
19334 @item set height @var{lpp}
19336 @itemx set width @var{cpl}
19338 These @code{set} commands specify a screen height of @var{lpp} lines and
19339 a screen width of @var{cpl} characters. The associated @code{show}
19340 commands display the current settings.
19342 If you specify a height of zero lines, @value{GDBN} does not pause during
19343 output no matter how long the output is. This is useful if output is to a
19344 file or to an editor buffer.
19346 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19347 from wrapping its output.
19349 @item set pagination on
19350 @itemx set pagination off
19351 @kindex set pagination
19352 Turn the output pagination on or off; the default is on. Turning
19353 pagination off is the alternative to @code{set height 0}. Note that
19354 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19355 Options, -batch}) also automatically disables pagination.
19357 @item show pagination
19358 @kindex show pagination
19359 Show the current pagination mode.
19364 @cindex number representation
19365 @cindex entering numbers
19367 You can always enter numbers in octal, decimal, or hexadecimal in
19368 @value{GDBN} by the usual conventions: octal numbers begin with
19369 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19370 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19371 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19372 10; likewise, the default display for numbers---when no particular
19373 format is specified---is base 10. You can change the default base for
19374 both input and output with the commands described below.
19377 @kindex set input-radix
19378 @item set input-radix @var{base}
19379 Set the default base for numeric input. Supported choices
19380 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19381 specified either unambiguously or using the current input radix; for
19385 set input-radix 012
19386 set input-radix 10.
19387 set input-radix 0xa
19391 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19392 leaves the input radix unchanged, no matter what it was, since
19393 @samp{10}, being without any leading or trailing signs of its base, is
19394 interpreted in the current radix. Thus, if the current radix is 16,
19395 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19398 @kindex set output-radix
19399 @item set output-radix @var{base}
19400 Set the default base for numeric display. Supported choices
19401 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19402 specified either unambiguously or using the current input radix.
19404 @kindex show input-radix
19405 @item show input-radix
19406 Display the current default base for numeric input.
19408 @kindex show output-radix
19409 @item show output-radix
19410 Display the current default base for numeric display.
19412 @item set radix @r{[}@var{base}@r{]}
19416 These commands set and show the default base for both input and output
19417 of numbers. @code{set radix} sets the radix of input and output to
19418 the same base; without an argument, it resets the radix back to its
19419 default value of 10.
19424 @section Configuring the Current ABI
19426 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19427 application automatically. However, sometimes you need to override its
19428 conclusions. Use these commands to manage @value{GDBN}'s view of the
19435 One @value{GDBN} configuration can debug binaries for multiple operating
19436 system targets, either via remote debugging or native emulation.
19437 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19438 but you can override its conclusion using the @code{set osabi} command.
19439 One example where this is useful is in debugging of binaries which use
19440 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19441 not have the same identifying marks that the standard C library for your
19446 Show the OS ABI currently in use.
19449 With no argument, show the list of registered available OS ABI's.
19451 @item set osabi @var{abi}
19452 Set the current OS ABI to @var{abi}.
19455 @cindex float promotion
19457 Generally, the way that an argument of type @code{float} is passed to a
19458 function depends on whether the function is prototyped. For a prototyped
19459 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19460 according to the architecture's convention for @code{float}. For unprototyped
19461 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19462 @code{double} and then passed.
19464 Unfortunately, some forms of debug information do not reliably indicate whether
19465 a function is prototyped. If @value{GDBN} calls a function that is not marked
19466 as prototyped, it consults @kbd{set coerce-float-to-double}.
19469 @kindex set coerce-float-to-double
19470 @item set coerce-float-to-double
19471 @itemx set coerce-float-to-double on
19472 Arguments of type @code{float} will be promoted to @code{double} when passed
19473 to an unprototyped function. This is the default setting.
19475 @item set coerce-float-to-double off
19476 Arguments of type @code{float} will be passed directly to unprototyped
19479 @kindex show coerce-float-to-double
19480 @item show coerce-float-to-double
19481 Show the current setting of promoting @code{float} to @code{double}.
19485 @kindex show cp-abi
19486 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19487 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19488 used to build your application. @value{GDBN} only fully supports
19489 programs with a single C@t{++} ABI; if your program contains code using
19490 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19491 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19492 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19493 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19494 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19495 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19500 Show the C@t{++} ABI currently in use.
19503 With no argument, show the list of supported C@t{++} ABI's.
19505 @item set cp-abi @var{abi}
19506 @itemx set cp-abi auto
19507 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19510 @node Messages/Warnings
19511 @section Optional Warnings and Messages
19513 @cindex verbose operation
19514 @cindex optional warnings
19515 By default, @value{GDBN} is silent about its inner workings. If you are
19516 running on a slow machine, you may want to use the @code{set verbose}
19517 command. This makes @value{GDBN} tell you when it does a lengthy
19518 internal operation, so you will not think it has crashed.
19520 Currently, the messages controlled by @code{set verbose} are those
19521 which announce that the symbol table for a source file is being read;
19522 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19525 @kindex set verbose
19526 @item set verbose on
19527 Enables @value{GDBN} output of certain informational messages.
19529 @item set verbose off
19530 Disables @value{GDBN} output of certain informational messages.
19532 @kindex show verbose
19534 Displays whether @code{set verbose} is on or off.
19537 By default, if @value{GDBN} encounters bugs in the symbol table of an
19538 object file, it is silent; but if you are debugging a compiler, you may
19539 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19544 @kindex set complaints
19545 @item set complaints @var{limit}
19546 Permits @value{GDBN} to output @var{limit} complaints about each type of
19547 unusual symbols before becoming silent about the problem. Set
19548 @var{limit} to zero to suppress all complaints; set it to a large number
19549 to prevent complaints from being suppressed.
19551 @kindex show complaints
19552 @item show complaints
19553 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19557 @anchor{confirmation requests}
19558 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19559 lot of stupid questions to confirm certain commands. For example, if
19560 you try to run a program which is already running:
19564 The program being debugged has been started already.
19565 Start it from the beginning? (y or n)
19568 If you are willing to unflinchingly face the consequences of your own
19569 commands, you can disable this ``feature'':
19573 @kindex set confirm
19575 @cindex confirmation
19576 @cindex stupid questions
19577 @item set confirm off
19578 Disables confirmation requests. Note that running @value{GDBN} with
19579 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19580 automatically disables confirmation requests.
19582 @item set confirm on
19583 Enables confirmation requests (the default).
19585 @kindex show confirm
19587 Displays state of confirmation requests.
19591 @cindex command tracing
19592 If you need to debug user-defined commands or sourced files you may find it
19593 useful to enable @dfn{command tracing}. In this mode each command will be
19594 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19595 quantity denoting the call depth of each command.
19598 @kindex set trace-commands
19599 @cindex command scripts, debugging
19600 @item set trace-commands on
19601 Enable command tracing.
19602 @item set trace-commands off
19603 Disable command tracing.
19604 @item show trace-commands
19605 Display the current state of command tracing.
19608 @node Debugging Output
19609 @section Optional Messages about Internal Happenings
19610 @cindex optional debugging messages
19612 @value{GDBN} has commands that enable optional debugging messages from
19613 various @value{GDBN} subsystems; normally these commands are of
19614 interest to @value{GDBN} maintainers, or when reporting a bug. This
19615 section documents those commands.
19618 @kindex set exec-done-display
19619 @item set exec-done-display
19620 Turns on or off the notification of asynchronous commands'
19621 completion. When on, @value{GDBN} will print a message when an
19622 asynchronous command finishes its execution. The default is off.
19623 @kindex show exec-done-display
19624 @item show exec-done-display
19625 Displays the current setting of asynchronous command completion
19628 @cindex gdbarch debugging info
19629 @cindex architecture debugging info
19630 @item set debug arch
19631 Turns on or off display of gdbarch debugging info. The default is off
19633 @item show debug arch
19634 Displays the current state of displaying gdbarch debugging info.
19635 @item set debug aix-thread
19636 @cindex AIX threads
19637 Display debugging messages about inner workings of the AIX thread
19639 @item show debug aix-thread
19640 Show the current state of AIX thread debugging info display.
19641 @item set debug dwarf2-die
19642 @cindex DWARF2 DIEs
19643 Dump DWARF2 DIEs after they are read in.
19644 The value is the number of nesting levels to print.
19645 A value of zero turns off the display.
19646 @item show debug dwarf2-die
19647 Show the current state of DWARF2 DIE debugging.
19648 @item set debug displaced
19649 @cindex displaced stepping debugging info
19650 Turns on or off display of @value{GDBN} debugging info for the
19651 displaced stepping support. The default is off.
19652 @item show debug displaced
19653 Displays the current state of displaying @value{GDBN} debugging info
19654 related to displaced stepping.
19655 @item set debug event
19656 @cindex event debugging info
19657 Turns on or off display of @value{GDBN} event debugging info. The
19659 @item show debug event
19660 Displays the current state of displaying @value{GDBN} event debugging
19662 @item set debug expression
19663 @cindex expression debugging info
19664 Turns on or off display of debugging info about @value{GDBN}
19665 expression parsing. The default is off.
19666 @item show debug expression
19667 Displays the current state of displaying debugging info about
19668 @value{GDBN} expression parsing.
19669 @item set debug frame
19670 @cindex frame debugging info
19671 Turns on or off display of @value{GDBN} frame debugging info. The
19673 @item show debug frame
19674 Displays the current state of displaying @value{GDBN} frame debugging
19676 @item set debug gnu-nat
19677 @cindex @sc{gnu}/Hurd debug messages
19678 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19679 @item show debug gnu-nat
19680 Show the current state of @sc{gnu}/Hurd debugging messages.
19681 @item set debug infrun
19682 @cindex inferior debugging info
19683 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19684 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19685 for implementing operations such as single-stepping the inferior.
19686 @item show debug infrun
19687 Displays the current state of @value{GDBN} inferior debugging.
19688 @item set debug lin-lwp
19689 @cindex @sc{gnu}/Linux LWP debug messages
19690 @cindex Linux lightweight processes
19691 Turns on or off debugging messages from the Linux LWP debug support.
19692 @item show debug lin-lwp
19693 Show the current state of Linux LWP debugging messages.
19694 @item set debug lin-lwp-async
19695 @cindex @sc{gnu}/Linux LWP async debug messages
19696 @cindex Linux lightweight processes
19697 Turns on or off debugging messages from the Linux LWP async debug support.
19698 @item show debug lin-lwp-async
19699 Show the current state of Linux LWP async debugging messages.
19700 @item set debug observer
19701 @cindex observer debugging info
19702 Turns on or off display of @value{GDBN} observer debugging. This
19703 includes info such as the notification of observable events.
19704 @item show debug observer
19705 Displays the current state of observer debugging.
19706 @item set debug overload
19707 @cindex C@t{++} overload debugging info
19708 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19709 info. This includes info such as ranking of functions, etc. The default
19711 @item show debug overload
19712 Displays the current state of displaying @value{GDBN} C@t{++} overload
19714 @cindex expression parser, debugging info
19715 @cindex debug expression parser
19716 @item set debug parser
19717 Turns on or off the display of expression parser debugging output.
19718 Internally, this sets the @code{yydebug} variable in the expression
19719 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
19720 details. The default is off.
19721 @item show debug parser
19722 Show the current state of expression parser debugging.
19723 @cindex packets, reporting on stdout
19724 @cindex serial connections, debugging
19725 @cindex debug remote protocol
19726 @cindex remote protocol debugging
19727 @cindex display remote packets
19728 @item set debug remote
19729 Turns on or off display of reports on all packets sent back and forth across
19730 the serial line to the remote machine. The info is printed on the
19731 @value{GDBN} standard output stream. The default is off.
19732 @item show debug remote
19733 Displays the state of display of remote packets.
19734 @item set debug serial
19735 Turns on or off display of @value{GDBN} serial debugging info. The
19737 @item show debug serial
19738 Displays the current state of displaying @value{GDBN} serial debugging
19740 @item set debug solib-frv
19741 @cindex FR-V shared-library debugging
19742 Turns on or off debugging messages for FR-V shared-library code.
19743 @item show debug solib-frv
19744 Display the current state of FR-V shared-library code debugging
19746 @item set debug target
19747 @cindex target debugging info
19748 Turns on or off display of @value{GDBN} target debugging info. This info
19749 includes what is going on at the target level of GDB, as it happens. The
19750 default is 0. Set it to 1 to track events, and to 2 to also track the
19751 value of large memory transfers. Changes to this flag do not take effect
19752 until the next time you connect to a target or use the @code{run} command.
19753 @item show debug target
19754 Displays the current state of displaying @value{GDBN} target debugging
19756 @item set debug timestamp
19757 @cindex timestampping debugging info
19758 Turns on or off display of timestamps with @value{GDBN} debugging info.
19759 When enabled, seconds and microseconds are displayed before each debugging
19761 @item show debug timestamp
19762 Displays the current state of displaying timestamps with @value{GDBN}
19764 @item set debugvarobj
19765 @cindex variable object debugging info
19766 Turns on or off display of @value{GDBN} variable object debugging
19767 info. The default is off.
19768 @item show debugvarobj
19769 Displays the current state of displaying @value{GDBN} variable object
19771 @item set debug xml
19772 @cindex XML parser debugging
19773 Turns on or off debugging messages for built-in XML parsers.
19774 @item show debug xml
19775 Displays the current state of XML debugging messages.
19778 @node Other Misc Settings
19779 @section Other Miscellaneous Settings
19780 @cindex miscellaneous settings
19783 @kindex set interactive-mode
19784 @item set interactive-mode
19785 If @code{on}, forces @value{GDBN} to operate interactively.
19786 If @code{off}, forces @value{GDBN} to operate non-interactively,
19787 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19788 based on whether the debugger was started in a terminal or not.
19790 In the vast majority of cases, the debugger should be able to guess
19791 correctly which mode should be used. But this setting can be useful
19792 in certain specific cases, such as running a MinGW @value{GDBN}
19793 inside a cygwin window.
19795 @kindex show interactive-mode
19796 @item show interactive-mode
19797 Displays whether the debugger is operating in interactive mode or not.
19800 @node Extending GDB
19801 @chapter Extending @value{GDBN}
19802 @cindex extending GDB
19804 @value{GDBN} provides two mechanisms for extension. The first is based
19805 on composition of @value{GDBN} commands, and the second is based on the
19806 Python scripting language.
19808 To facilitate the use of these extensions, @value{GDBN} is capable
19809 of evaluating the contents of a file. When doing so, @value{GDBN}
19810 can recognize which scripting language is being used by looking at
19811 the filename extension. Files with an unrecognized filename extension
19812 are always treated as a @value{GDBN} Command Files.
19813 @xref{Command Files,, Command files}.
19815 You can control how @value{GDBN} evaluates these files with the following
19819 @kindex set script-extension
19820 @kindex show script-extension
19821 @item set script-extension off
19822 All scripts are always evaluated as @value{GDBN} Command Files.
19824 @item set script-extension soft
19825 The debugger determines the scripting language based on filename
19826 extension. If this scripting language is supported, @value{GDBN}
19827 evaluates the script using that language. Otherwise, it evaluates
19828 the file as a @value{GDBN} Command File.
19830 @item set script-extension strict
19831 The debugger determines the scripting language based on filename
19832 extension, and evaluates the script using that language. If the
19833 language is not supported, then the evaluation fails.
19835 @item show script-extension
19836 Display the current value of the @code{script-extension} option.
19841 * Sequences:: Canned Sequences of Commands
19842 * Python:: Scripting @value{GDBN} using Python
19846 @section Canned Sequences of Commands
19848 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
19849 Command Lists}), @value{GDBN} provides two ways to store sequences of
19850 commands for execution as a unit: user-defined commands and command
19854 * Define:: How to define your own commands
19855 * Hooks:: Hooks for user-defined commands
19856 * Command Files:: How to write scripts of commands to be stored in a file
19857 * Output:: Commands for controlled output
19861 @subsection User-defined Commands
19863 @cindex user-defined command
19864 @cindex arguments, to user-defined commands
19865 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
19866 which you assign a new name as a command. This is done with the
19867 @code{define} command. User commands may accept up to 10 arguments
19868 separated by whitespace. Arguments are accessed within the user command
19869 via @code{$arg0@dots{}$arg9}. A trivial example:
19873 print $arg0 + $arg1 + $arg2
19878 To execute the command use:
19885 This defines the command @code{adder}, which prints the sum of
19886 its three arguments. Note the arguments are text substitutions, so they may
19887 reference variables, use complex expressions, or even perform inferior
19890 @cindex argument count in user-defined commands
19891 @cindex how many arguments (user-defined commands)
19892 In addition, @code{$argc} may be used to find out how many arguments have
19893 been passed. This expands to a number in the range 0@dots{}10.
19898 print $arg0 + $arg1
19901 print $arg0 + $arg1 + $arg2
19909 @item define @var{commandname}
19910 Define a command named @var{commandname}. If there is already a command
19911 by that name, you are asked to confirm that you want to redefine it.
19912 @var{commandname} may be a bare command name consisting of letters,
19913 numbers, dashes, and underscores. It may also start with any predefined
19914 prefix command. For example, @samp{define target my-target} creates
19915 a user-defined @samp{target my-target} command.
19917 The definition of the command is made up of other @value{GDBN} command lines,
19918 which are given following the @code{define} command. The end of these
19919 commands is marked by a line containing @code{end}.
19922 @kindex end@r{ (user-defined commands)}
19923 @item document @var{commandname}
19924 Document the user-defined command @var{commandname}, so that it can be
19925 accessed by @code{help}. The command @var{commandname} must already be
19926 defined. This command reads lines of documentation just as @code{define}
19927 reads the lines of the command definition, ending with @code{end}.
19928 After the @code{document} command is finished, @code{help} on command
19929 @var{commandname} displays the documentation you have written.
19931 You may use the @code{document} command again to change the
19932 documentation of a command. Redefining the command with @code{define}
19933 does not change the documentation.
19935 @kindex dont-repeat
19936 @cindex don't repeat command
19938 Used inside a user-defined command, this tells @value{GDBN} that this
19939 command should not be repeated when the user hits @key{RET}
19940 (@pxref{Command Syntax, repeat last command}).
19942 @kindex help user-defined
19943 @item help user-defined
19944 List all user-defined commands, with the first line of the documentation
19949 @itemx show user @var{commandname}
19950 Display the @value{GDBN} commands used to define @var{commandname} (but
19951 not its documentation). If no @var{commandname} is given, display the
19952 definitions for all user-defined commands.
19954 @cindex infinite recursion in user-defined commands
19955 @kindex show max-user-call-depth
19956 @kindex set max-user-call-depth
19957 @item show max-user-call-depth
19958 @itemx set max-user-call-depth
19959 The value of @code{max-user-call-depth} controls how many recursion
19960 levels are allowed in user-defined commands before @value{GDBN} suspects an
19961 infinite recursion and aborts the command.
19964 In addition to the above commands, user-defined commands frequently
19965 use control flow commands, described in @ref{Command Files}.
19967 When user-defined commands are executed, the
19968 commands of the definition are not printed. An error in any command
19969 stops execution of the user-defined command.
19971 If used interactively, commands that would ask for confirmation proceed
19972 without asking when used inside a user-defined command. Many @value{GDBN}
19973 commands that normally print messages to say what they are doing omit the
19974 messages when used in a user-defined command.
19977 @subsection User-defined Command Hooks
19978 @cindex command hooks
19979 @cindex hooks, for commands
19980 @cindex hooks, pre-command
19983 You may define @dfn{hooks}, which are a special kind of user-defined
19984 command. Whenever you run the command @samp{foo}, if the user-defined
19985 command @samp{hook-foo} exists, it is executed (with no arguments)
19986 before that command.
19988 @cindex hooks, post-command
19990 A hook may also be defined which is run after the command you executed.
19991 Whenever you run the command @samp{foo}, if the user-defined command
19992 @samp{hookpost-foo} exists, it is executed (with no arguments) after
19993 that command. Post-execution hooks may exist simultaneously with
19994 pre-execution hooks, for the same command.
19996 It is valid for a hook to call the command which it hooks. If this
19997 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
19999 @c It would be nice if hookpost could be passed a parameter indicating
20000 @c if the command it hooks executed properly or not. FIXME!
20002 @kindex stop@r{, a pseudo-command}
20003 In addition, a pseudo-command, @samp{stop} exists. Defining
20004 (@samp{hook-stop}) makes the associated commands execute every time
20005 execution stops in your program: before breakpoint commands are run,
20006 displays are printed, or the stack frame is printed.
20008 For example, to ignore @code{SIGALRM} signals while
20009 single-stepping, but treat them normally during normal execution,
20014 handle SIGALRM nopass
20018 handle SIGALRM pass
20021 define hook-continue
20022 handle SIGALRM pass
20026 As a further example, to hook at the beginning and end of the @code{echo}
20027 command, and to add extra text to the beginning and end of the message,
20035 define hookpost-echo
20039 (@value{GDBP}) echo Hello World
20040 <<<---Hello World--->>>
20045 You can define a hook for any single-word command in @value{GDBN}, but
20046 not for command aliases; you should define a hook for the basic command
20047 name, e.g.@: @code{backtrace} rather than @code{bt}.
20048 @c FIXME! So how does Joe User discover whether a command is an alias
20050 You can hook a multi-word command by adding @code{hook-} or
20051 @code{hookpost-} to the last word of the command, e.g.@:
20052 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20054 If an error occurs during the execution of your hook, execution of
20055 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20056 (before the command that you actually typed had a chance to run).
20058 If you try to define a hook which does not match any known command, you
20059 get a warning from the @code{define} command.
20061 @node Command Files
20062 @subsection Command Files
20064 @cindex command files
20065 @cindex scripting commands
20066 A command file for @value{GDBN} is a text file made of lines that are
20067 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20068 also be included. An empty line in a command file does nothing; it
20069 does not mean to repeat the last command, as it would from the
20072 You can request the execution of a command file with the @code{source}
20073 command. Note that the @code{source} command is also used to evaluate
20074 scripts that are not Command Files. The exact behavior can be configured
20075 using the @code{script-extension} setting.
20076 @xref{Extending GDB,, Extending GDB}.
20080 @cindex execute commands from a file
20081 @item source [-s] [-v] @var{filename}
20082 Execute the command file @var{filename}.
20085 The lines in a command file are generally executed sequentially,
20086 unless the order of execution is changed by one of the
20087 @emph{flow-control commands} described below. The commands are not
20088 printed as they are executed. An error in any command terminates
20089 execution of the command file and control is returned to the console.
20091 @value{GDBN} first searches for @var{filename} in the current directory.
20092 If the file is not found there, and @var{filename} does not specify a
20093 directory, then @value{GDBN} also looks for the file on the source search path
20094 (specified with the @samp{directory} command);
20095 except that @file{$cdir} is not searched because the compilation directory
20096 is not relevant to scripts.
20098 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20099 on the search path even if @var{filename} specifies a directory.
20100 The search is done by appending @var{filename} to each element of the
20101 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20102 and the search path contains @file{/home/user} then @value{GDBN} will
20103 look for the script @file{/home/user/mylib/myscript}.
20104 The search is also done if @var{filename} is an absolute path.
20105 For example, if @var{filename} is @file{/tmp/myscript} and
20106 the search path contains @file{/home/user} then @value{GDBN} will
20107 look for the script @file{/home/user/tmp/myscript}.
20108 For DOS-like systems, if @var{filename} contains a drive specification,
20109 it is stripped before concatenation. For example, if @var{filename} is
20110 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20111 will look for the script @file{c:/tmp/myscript}.
20113 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20114 each command as it is executed. The option must be given before
20115 @var{filename}, and is interpreted as part of the filename anywhere else.
20117 Commands that would ask for confirmation if used interactively proceed
20118 without asking when used in a command file. Many @value{GDBN} commands that
20119 normally print messages to say what they are doing omit the messages
20120 when called from command files.
20122 @value{GDBN} also accepts command input from standard input. In this
20123 mode, normal output goes to standard output and error output goes to
20124 standard error. Errors in a command file supplied on standard input do
20125 not terminate execution of the command file---execution continues with
20129 gdb < cmds > log 2>&1
20132 (The syntax above will vary depending on the shell used.) This example
20133 will execute commands from the file @file{cmds}. All output and errors
20134 would be directed to @file{log}.
20136 Since commands stored on command files tend to be more general than
20137 commands typed interactively, they frequently need to deal with
20138 complicated situations, such as different or unexpected values of
20139 variables and symbols, changes in how the program being debugged is
20140 built, etc. @value{GDBN} provides a set of flow-control commands to
20141 deal with these complexities. Using these commands, you can write
20142 complex scripts that loop over data structures, execute commands
20143 conditionally, etc.
20150 This command allows to include in your script conditionally executed
20151 commands. The @code{if} command takes a single argument, which is an
20152 expression to evaluate. It is followed by a series of commands that
20153 are executed only if the expression is true (its value is nonzero).
20154 There can then optionally be an @code{else} line, followed by a series
20155 of commands that are only executed if the expression was false. The
20156 end of the list is marked by a line containing @code{end}.
20160 This command allows to write loops. Its syntax is similar to
20161 @code{if}: the command takes a single argument, which is an expression
20162 to evaluate, and must be followed by the commands to execute, one per
20163 line, terminated by an @code{end}. These commands are called the
20164 @dfn{body} of the loop. The commands in the body of @code{while} are
20165 executed repeatedly as long as the expression evaluates to true.
20169 This command exits the @code{while} loop in whose body it is included.
20170 Execution of the script continues after that @code{while}s @code{end}
20173 @kindex loop_continue
20174 @item loop_continue
20175 This command skips the execution of the rest of the body of commands
20176 in the @code{while} loop in whose body it is included. Execution
20177 branches to the beginning of the @code{while} loop, where it evaluates
20178 the controlling expression.
20180 @kindex end@r{ (if/else/while commands)}
20182 Terminate the block of commands that are the body of @code{if},
20183 @code{else}, or @code{while} flow-control commands.
20188 @subsection Commands for Controlled Output
20190 During the execution of a command file or a user-defined command, normal
20191 @value{GDBN} output is suppressed; the only output that appears is what is
20192 explicitly printed by the commands in the definition. This section
20193 describes three commands useful for generating exactly the output you
20198 @item echo @var{text}
20199 @c I do not consider backslash-space a standard C escape sequence
20200 @c because it is not in ANSI.
20201 Print @var{text}. Nonprinting characters can be included in
20202 @var{text} using C escape sequences, such as @samp{\n} to print a
20203 newline. @strong{No newline is printed unless you specify one.}
20204 In addition to the standard C escape sequences, a backslash followed
20205 by a space stands for a space. This is useful for displaying a
20206 string with spaces at the beginning or the end, since leading and
20207 trailing spaces are otherwise trimmed from all arguments.
20208 To print @samp{@w{ }and foo =@w{ }}, use the command
20209 @samp{echo \@w{ }and foo = \@w{ }}.
20211 A backslash at the end of @var{text} can be used, as in C, to continue
20212 the command onto subsequent lines. For example,
20215 echo This is some text\n\
20216 which is continued\n\
20217 onto several lines.\n
20220 produces the same output as
20223 echo This is some text\n
20224 echo which is continued\n
20225 echo onto several lines.\n
20229 @item output @var{expression}
20230 Print the value of @var{expression} and nothing but that value: no
20231 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20232 value history either. @xref{Expressions, ,Expressions}, for more information
20235 @item output/@var{fmt} @var{expression}
20236 Print the value of @var{expression} in format @var{fmt}. You can use
20237 the same formats as for @code{print}. @xref{Output Formats,,Output
20238 Formats}, for more information.
20241 @item printf @var{template}, @var{expressions}@dots{}
20242 Print the values of one or more @var{expressions} under the control of
20243 the string @var{template}. To print several values, make
20244 @var{expressions} be a comma-separated list of individual expressions,
20245 which may be either numbers or pointers. Their values are printed as
20246 specified by @var{template}, exactly as a C program would do by
20247 executing the code below:
20250 printf (@var{template}, @var{expressions}@dots{});
20253 As in @code{C} @code{printf}, ordinary characters in @var{template}
20254 are printed verbatim, while @dfn{conversion specification} introduced
20255 by the @samp{%} character cause subsequent @var{expressions} to be
20256 evaluated, their values converted and formatted according to type and
20257 style information encoded in the conversion specifications, and then
20260 For example, you can print two values in hex like this:
20263 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20266 @code{printf} supports all the standard @code{C} conversion
20267 specifications, including the flags and modifiers between the @samp{%}
20268 character and the conversion letter, with the following exceptions:
20272 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20275 The modifier @samp{*} is not supported for specifying precision or
20279 The @samp{'} flag (for separation of digits into groups according to
20280 @code{LC_NUMERIC'}) is not supported.
20283 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20287 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20290 The conversion letters @samp{a} and @samp{A} are not supported.
20294 Note that the @samp{ll} type modifier is supported only if the
20295 underlying @code{C} implementation used to build @value{GDBN} supports
20296 the @code{long long int} type, and the @samp{L} type modifier is
20297 supported only if @code{long double} type is available.
20299 As in @code{C}, @code{printf} supports simple backslash-escape
20300 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20301 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20302 single character. Octal and hexadecimal escape sequences are not
20305 Additionally, @code{printf} supports conversion specifications for DFP
20306 (@dfn{Decimal Floating Point}) types using the following length modifiers
20307 together with a floating point specifier.
20312 @samp{H} for printing @code{Decimal32} types.
20315 @samp{D} for printing @code{Decimal64} types.
20318 @samp{DD} for printing @code{Decimal128} types.
20321 If the underlying @code{C} implementation used to build @value{GDBN} has
20322 support for the three length modifiers for DFP types, other modifiers
20323 such as width and precision will also be available for @value{GDBN} to use.
20325 In case there is no such @code{C} support, no additional modifiers will be
20326 available and the value will be printed in the standard way.
20328 Here's an example of printing DFP types using the above conversion letters:
20330 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20334 @item eval @var{template}, @var{expressions}@dots{}
20335 Convert the values of one or more @var{expressions} under the control of
20336 the string @var{template} to a command line, and call it.
20341 @section Scripting @value{GDBN} using Python
20342 @cindex python scripting
20343 @cindex scripting with python
20345 You can script @value{GDBN} using the @uref{http://www.python.org/,
20346 Python programming language}. This feature is available only if
20347 @value{GDBN} was configured using @option{--with-python}.
20349 @cindex python directory
20350 Python scripts used by @value{GDBN} should be installed in
20351 @file{@var{data-directory}/python}, where @var{data-directory} is
20352 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}). This directory, known as the @dfn{python directory},
20353 is automatically added to the Python Search Path in order to allow
20354 the Python interpreter to locate all scripts installed at this location.
20357 * Python Commands:: Accessing Python from @value{GDBN}.
20358 * Python API:: Accessing @value{GDBN} from Python.
20359 * Auto-loading:: Automatically loading Python code.
20362 @node Python Commands
20363 @subsection Python Commands
20364 @cindex python commands
20365 @cindex commands to access python
20367 @value{GDBN} provides one command for accessing the Python interpreter,
20368 and one related setting:
20372 @item python @r{[}@var{code}@r{]}
20373 The @code{python} command can be used to evaluate Python code.
20375 If given an argument, the @code{python} command will evaluate the
20376 argument as a Python command. For example:
20379 (@value{GDBP}) python print 23
20383 If you do not provide an argument to @code{python}, it will act as a
20384 multi-line command, like @code{define}. In this case, the Python
20385 script is made up of subsequent command lines, given after the
20386 @code{python} command. This command list is terminated using a line
20387 containing @code{end}. For example:
20390 (@value{GDBP}) python
20392 End with a line saying just "end".
20398 @kindex maint set python print-stack
20399 @item maint set python print-stack
20400 By default, @value{GDBN} will print a stack trace when an error occurs
20401 in a Python script. This can be controlled using @code{maint set
20402 python print-stack}: if @code{on}, the default, then Python stack
20403 printing is enabled; if @code{off}, then Python stack printing is
20407 It is also possible to execute a Python script from the @value{GDBN}
20411 @item source @file{script-name}
20412 The script name must end with @samp{.py} and @value{GDBN} must be configured
20413 to recognize the script language based on filename extension using
20414 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20416 @item python execfile ("script-name")
20417 This method is based on the @code{execfile} Python built-in function,
20418 and thus is always available.
20422 @subsection Python API
20424 @cindex programming in python
20426 @cindex python stdout
20427 @cindex python pagination
20428 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20429 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20430 A Python program which outputs to one of these streams may have its
20431 output interrupted by the user (@pxref{Screen Size}). In this
20432 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20435 * Basic Python:: Basic Python Functions.
20436 * Exception Handling::
20437 * Values From Inferior::
20438 * Types In Python:: Python representation of types.
20439 * Pretty Printing API:: Pretty-printing values.
20440 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20441 * Disabling Pretty-Printers:: Disabling broken printers.
20442 * Inferiors In Python:: Python representation of inferiors (processes)
20443 * Threads In Python:: Accessing inferior threads from Python.
20444 * Commands In Python:: Implementing new commands in Python.
20445 * Parameters In Python:: Adding new @value{GDBN} parameters.
20446 * Functions In Python:: Writing new convenience functions.
20447 * Progspaces In Python:: Program spaces.
20448 * Objfiles In Python:: Object files.
20449 * Frames In Python:: Accessing inferior stack frames from Python.
20450 * Blocks In Python:: Accessing frame blocks from Python.
20451 * Symbols In Python:: Python representation of symbols.
20452 * Symbol Tables In Python:: Python representation of symbol tables.
20453 * Lazy Strings In Python:: Python representation of lazy strings.
20454 * Breakpoints In Python:: Manipulating breakpoints using Python.
20458 @subsubsection Basic Python
20460 @cindex python functions
20461 @cindex python module
20463 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20464 methods and classes added by @value{GDBN} are placed in this module.
20465 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20466 use in all scripts evaluated by the @code{python} command.
20468 @findex gdb.PYTHONDIR
20470 A string containing the python directory (@pxref{Python}).
20473 @findex gdb.execute
20474 @defun execute command [from_tty] [to_string]
20475 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20476 If a GDB exception happens while @var{command} runs, it is
20477 translated as described in @ref{Exception Handling,,Exception Handling}.
20479 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20480 command as having originated from the user invoking it interactively.
20481 It must be a boolean value. If omitted, it defaults to @code{False}.
20483 By default, any output produced by @var{command} is sent to
20484 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20485 @code{True}, then output will be collected by @code{gdb.execute} and
20486 returned as a string. The default is @code{False}, in which case the
20487 return value is @code{None}. If @var{to_string} is @code{True}, the
20488 @value{GDBN} virtual terminal will be temporarily set to unlimited width
20489 and height, and its pagination will be disabled; @pxref{Screen Size}.
20492 @findex gdb.breakpoints
20494 Return a sequence holding all of @value{GDBN}'s breakpoints.
20495 @xref{Breakpoints In Python}, for more information.
20498 @findex gdb.parameter
20499 @defun parameter parameter
20500 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20501 string naming the parameter to look up; @var{parameter} may contain
20502 spaces if the parameter has a multi-part name. For example,
20503 @samp{print object} is a valid parameter name.
20505 If the named parameter does not exist, this function throws a
20506 @code{RuntimeError}. Otherwise, the parameter's value is converted to
20507 a Python value of the appropriate type, and returned.
20510 @findex gdb.history
20511 @defun history number
20512 Return a value from @value{GDBN}'s value history (@pxref{Value
20513 History}). @var{number} indicates which history element to return.
20514 If @var{number} is negative, then @value{GDBN} will take its absolute value
20515 and count backward from the last element (i.e., the most recent element) to
20516 find the value to return. If @var{number} is zero, then @value{GDBN} will
20517 return the most recent element. If the element specified by @var{number}
20518 doesn't exist in the value history, a @code{RuntimeError} exception will be
20521 If no exception is raised, the return value is always an instance of
20522 @code{gdb.Value} (@pxref{Values From Inferior}).
20525 @findex gdb.parse_and_eval
20526 @defun parse_and_eval expression
20527 Parse @var{expression} as an expression in the current language,
20528 evaluate it, and return the result as a @code{gdb.Value}.
20529 @var{expression} must be a string.
20531 This function can be useful when implementing a new command
20532 (@pxref{Commands In Python}), as it provides a way to parse the
20533 command's argument as an expression. It is also useful simply to
20534 compute values, for example, it is the only way to get the value of a
20535 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20539 @defun write string
20540 Print a string to @value{GDBN}'s paginated standard output stream.
20541 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20542 call this function.
20547 Flush @value{GDBN}'s paginated standard output stream. Flushing
20548 @code{sys.stdout} or @code{sys.stderr} will automatically call this
20552 @findex gdb.target_charset
20553 @defun target_charset
20554 Return the name of the current target character set (@pxref{Character
20555 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20556 that @samp{auto} is never returned.
20559 @findex gdb.target_wide_charset
20560 @defun target_wide_charset
20561 Return the name of the current target wide character set
20562 (@pxref{Character Sets}). This differs from
20563 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20567 @node Exception Handling
20568 @subsubsection Exception Handling
20569 @cindex python exceptions
20570 @cindex exceptions, python
20572 When executing the @code{python} command, Python exceptions
20573 uncaught within the Python code are translated to calls to
20574 @value{GDBN} error-reporting mechanism. If the command that called
20575 @code{python} does not handle the error, @value{GDBN} will
20576 terminate it and print an error message containing the Python
20577 exception name, the associated value, and the Python call stack
20578 backtrace at the point where the exception was raised. Example:
20581 (@value{GDBP}) python print foo
20582 Traceback (most recent call last):
20583 File "<string>", line 1, in <module>
20584 NameError: name 'foo' is not defined
20587 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
20588 code are converted to Python @code{RuntimeError} exceptions. User
20589 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
20590 prompt) is translated to a Python @code{KeyboardInterrupt}
20591 exception. If you catch these exceptions in your Python code, your
20592 exception handler will see @code{RuntimeError} or
20593 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
20594 message as its value, and the Python call stack backtrace at the
20595 Python statement closest to where the @value{GDBN} error occured as the
20598 @findex gdb.GdbError
20599 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
20600 it is useful to be able to throw an exception that doesn't cause a
20601 traceback to be printed. For example, the user may have invoked the
20602 command incorrectly. Use the @code{gdb.GdbError} exception
20603 to handle this case. Example:
20607 >class HelloWorld (gdb.Command):
20608 > """Greet the whole world."""
20609 > def __init__ (self):
20610 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20611 > def invoke (self, args, from_tty):
20612 > argv = gdb.string_to_argv (args)
20613 > if len (argv) != 0:
20614 > raise gdb.GdbError ("hello-world takes no arguments")
20615 > print "Hello, World!"
20618 (gdb) hello-world 42
20619 hello-world takes no arguments
20622 @node Values From Inferior
20623 @subsubsection Values From Inferior
20624 @cindex values from inferior, with Python
20625 @cindex python, working with values from inferior
20627 @cindex @code{gdb.Value}
20628 @value{GDBN} provides values it obtains from the inferior program in
20629 an object of type @code{gdb.Value}. @value{GDBN} uses this object
20630 for its internal bookkeeping of the inferior's values, and for
20631 fetching values when necessary.
20633 Inferior values that are simple scalars can be used directly in
20634 Python expressions that are valid for the value's data type. Here's
20635 an example for an integer or floating-point value @code{some_val}:
20642 As result of this, @code{bar} will also be a @code{gdb.Value} object
20643 whose values are of the same type as those of @code{some_val}.
20645 Inferior values that are structures or instances of some class can
20646 be accessed using the Python @dfn{dictionary syntax}. For example, if
20647 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
20648 can access its @code{foo} element with:
20651 bar = some_val['foo']
20654 Again, @code{bar} will also be a @code{gdb.Value} object.
20656 A @code{gdb.Value} that represents a function can be executed via
20657 inferior function call. Any arguments provided to the call must match
20658 the function's prototype, and must be provided in the order specified
20661 For example, @code{some_val} is a @code{gdb.Value} instance
20662 representing a function that takes two integers as arguments. To
20663 execute this function, call it like so:
20666 result = some_val (10,20)
20669 Any values returned from a function call will be stored as a
20672 The following attributes are provided:
20675 @defivar Value address
20676 If this object is addressable, this read-only attribute holds a
20677 @code{gdb.Value} object representing the address. Otherwise,
20678 this attribute holds @code{None}.
20681 @cindex optimized out value in Python
20682 @defivar Value is_optimized_out
20683 This read-only boolean attribute is true if the compiler optimized out
20684 this value, thus it is not available for fetching from the inferior.
20687 @defivar Value type
20688 The type of this @code{gdb.Value}. The value of this attribute is a
20689 @code{gdb.Type} object.
20693 The following methods are provided:
20696 @defmethod Value cast type
20697 Return a new instance of @code{gdb.Value} that is the result of
20698 casting this instance to the type described by @var{type}, which must
20699 be a @code{gdb.Type} object. If the cast cannot be performed for some
20700 reason, this method throws an exception.
20703 @defmethod Value dereference
20704 For pointer data types, this method returns a new @code{gdb.Value} object
20705 whose contents is the object pointed to by the pointer. For example, if
20706 @code{foo} is a C pointer to an @code{int}, declared in your C program as
20713 then you can use the corresponding @code{gdb.Value} to access what
20714 @code{foo} points to like this:
20717 bar = foo.dereference ()
20720 The result @code{bar} will be a @code{gdb.Value} object holding the
20721 value pointed to by @code{foo}.
20724 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
20725 If this @code{gdb.Value} represents a string, then this method
20726 converts the contents to a Python string. Otherwise, this method will
20727 throw an exception.
20729 Strings are recognized in a language-specific way; whether a given
20730 @code{gdb.Value} represents a string is determined by the current
20733 For C-like languages, a value is a string if it is a pointer to or an
20734 array of characters or ints. The string is assumed to be terminated
20735 by a zero of the appropriate width. However if the optional length
20736 argument is given, the string will be converted to that given length,
20737 ignoring any embedded zeros that the string may contain.
20739 If the optional @var{encoding} argument is given, it must be a string
20740 naming the encoding of the string in the @code{gdb.Value}, such as
20741 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
20742 the same encodings as the corresponding argument to Python's
20743 @code{string.decode} method, and the Python codec machinery will be used
20744 to convert the string. If @var{encoding} is not given, or if
20745 @var{encoding} is the empty string, then either the @code{target-charset}
20746 (@pxref{Character Sets}) will be used, or a language-specific encoding
20747 will be used, if the current language is able to supply one.
20749 The optional @var{errors} argument is the same as the corresponding
20750 argument to Python's @code{string.decode} method.
20752 If the optional @var{length} argument is given, the string will be
20753 fetched and converted to the given length.
20756 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
20757 If this @code{gdb.Value} represents a string, then this method
20758 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
20759 In Python}). Otherwise, this method will throw an exception.
20761 If the optional @var{encoding} argument is given, it must be a string
20762 naming the encoding of the @code{gdb.LazyString}. Some examples are:
20763 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
20764 @var{encoding} argument is an encoding that @value{GDBN} does
20765 recognize, @value{GDBN} will raise an error.
20767 When a lazy string is printed, the @value{GDBN} encoding machinery is
20768 used to convert the string during printing. If the optional
20769 @var{encoding} argument is not provided, or is an empty string,
20770 @value{GDBN} will automatically select the encoding most suitable for
20771 the string type. For further information on encoding in @value{GDBN}
20772 please see @ref{Character Sets}.
20774 If the optional @var{length} argument is given, the string will be
20775 fetched and encoded to the length of characters specified. If
20776 the @var{length} argument is not provided, the string will be fetched
20777 and encoded until a null of appropriate width is found.
20781 @node Types In Python
20782 @subsubsection Types In Python
20783 @cindex types in Python
20784 @cindex Python, working with types
20787 @value{GDBN} represents types from the inferior using the class
20790 The following type-related functions are available in the @code{gdb}
20793 @findex gdb.lookup_type
20794 @defun lookup_type name [block]
20795 This function looks up a type by name. @var{name} is the name of the
20796 type to look up. It must be a string.
20798 If @var{block} is given, then @var{name} is looked up in that scope.
20799 Otherwise, it is searched for globally.
20801 Ordinarily, this function will return an instance of @code{gdb.Type}.
20802 If the named type cannot be found, it will throw an exception.
20805 An instance of @code{Type} has the following attributes:
20809 The type code for this type. The type code will be one of the
20810 @code{TYPE_CODE_} constants defined below.
20813 @defivar Type sizeof
20814 The size of this type, in target @code{char} units. Usually, a
20815 target's @code{char} type will be an 8-bit byte. However, on some
20816 unusual platforms, this type may have a different size.
20820 The tag name for this type. The tag name is the name after
20821 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
20822 languages have this concept. If this type has no tag name, then
20823 @code{None} is returned.
20827 The following methods are provided:
20830 @defmethod Type fields
20831 For structure and union types, this method returns the fields. Range
20832 types have two fields, the minimum and maximum values. Enum types
20833 have one field per enum constant. Function and method types have one
20834 field per parameter. The base types of C@t{++} classes are also
20835 represented as fields. If the type has no fields, or does not fit
20836 into one of these categories, an empty sequence will be returned.
20838 Each field is an object, with some pre-defined attributes:
20841 This attribute is not available for @code{static} fields (as in
20842 C@t{++} or Java). For non-@code{static} fields, the value is the bit
20843 position of the field.
20846 The name of the field, or @code{None} for anonymous fields.
20849 This is @code{True} if the field is artificial, usually meaning that
20850 it was provided by the compiler and not the user. This attribute is
20851 always provided, and is @code{False} if the field is not artificial.
20853 @item is_base_class
20854 This is @code{True} if the field represents a base class of a C@t{++}
20855 structure. This attribute is always provided, and is @code{False}
20856 if the field is not a base class of the type that is the argument of
20857 @code{fields}, or if that type was not a C@t{++} class.
20860 If the field is packed, or is a bitfield, then this will have a
20861 non-zero value, which is the size of the field in bits. Otherwise,
20862 this will be zero; in this case the field's size is given by its type.
20865 The type of the field. This is usually an instance of @code{Type},
20866 but it can be @code{None} in some situations.
20870 @defmethod Type const
20871 Return a new @code{gdb.Type} object which represents a
20872 @code{const}-qualified variant of this type.
20875 @defmethod Type volatile
20876 Return a new @code{gdb.Type} object which represents a
20877 @code{volatile}-qualified variant of this type.
20880 @defmethod Type unqualified
20881 Return a new @code{gdb.Type} object which represents an unqualified
20882 variant of this type. That is, the result is neither @code{const} nor
20886 @defmethod Type range
20887 Return a Python @code{Tuple} object that contains two elements: the
20888 low bound of the argument type and the high bound of that type. If
20889 the type does not have a range, @value{GDBN} will raise a
20890 @code{RuntimeError} exception.
20893 @defmethod Type reference
20894 Return a new @code{gdb.Type} object which represents a reference to this
20898 @defmethod Type pointer
20899 Return a new @code{gdb.Type} object which represents a pointer to this
20903 @defmethod Type strip_typedefs
20904 Return a new @code{gdb.Type} that represents the real type,
20905 after removing all layers of typedefs.
20908 @defmethod Type target
20909 Return a new @code{gdb.Type} object which represents the target type
20912 For a pointer type, the target type is the type of the pointed-to
20913 object. For an array type (meaning C-like arrays), the target type is
20914 the type of the elements of the array. For a function or method type,
20915 the target type is the type of the return value. For a complex type,
20916 the target type is the type of the elements. For a typedef, the
20917 target type is the aliased type.
20919 If the type does not have a target, this method will throw an
20923 @defmethod Type template_argument n [block]
20924 If this @code{gdb.Type} is an instantiation of a template, this will
20925 return a new @code{gdb.Type} which represents the type of the
20926 @var{n}th template argument.
20928 If this @code{gdb.Type} is not a template type, this will throw an
20929 exception. Ordinarily, only C@t{++} code will have template types.
20931 If @var{block} is given, then @var{name} is looked up in that scope.
20932 Otherwise, it is searched for globally.
20937 Each type has a code, which indicates what category this type falls
20938 into. The available type categories are represented by constants
20939 defined in the @code{gdb} module:
20942 @findex TYPE_CODE_PTR
20943 @findex gdb.TYPE_CODE_PTR
20944 @item TYPE_CODE_PTR
20945 The type is a pointer.
20947 @findex TYPE_CODE_ARRAY
20948 @findex gdb.TYPE_CODE_ARRAY
20949 @item TYPE_CODE_ARRAY
20950 The type is an array.
20952 @findex TYPE_CODE_STRUCT
20953 @findex gdb.TYPE_CODE_STRUCT
20954 @item TYPE_CODE_STRUCT
20955 The type is a structure.
20957 @findex TYPE_CODE_UNION
20958 @findex gdb.TYPE_CODE_UNION
20959 @item TYPE_CODE_UNION
20960 The type is a union.
20962 @findex TYPE_CODE_ENUM
20963 @findex gdb.TYPE_CODE_ENUM
20964 @item TYPE_CODE_ENUM
20965 The type is an enum.
20967 @findex TYPE_CODE_FLAGS
20968 @findex gdb.TYPE_CODE_FLAGS
20969 @item TYPE_CODE_FLAGS
20970 A bit flags type, used for things such as status registers.
20972 @findex TYPE_CODE_FUNC
20973 @findex gdb.TYPE_CODE_FUNC
20974 @item TYPE_CODE_FUNC
20975 The type is a function.
20977 @findex TYPE_CODE_INT
20978 @findex gdb.TYPE_CODE_INT
20979 @item TYPE_CODE_INT
20980 The type is an integer type.
20982 @findex TYPE_CODE_FLT
20983 @findex gdb.TYPE_CODE_FLT
20984 @item TYPE_CODE_FLT
20985 A floating point type.
20987 @findex TYPE_CODE_VOID
20988 @findex gdb.TYPE_CODE_VOID
20989 @item TYPE_CODE_VOID
20990 The special type @code{void}.
20992 @findex TYPE_CODE_SET
20993 @findex gdb.TYPE_CODE_SET
20994 @item TYPE_CODE_SET
20997 @findex TYPE_CODE_RANGE
20998 @findex gdb.TYPE_CODE_RANGE
20999 @item TYPE_CODE_RANGE
21000 A range type, that is, an integer type with bounds.
21002 @findex TYPE_CODE_STRING
21003 @findex gdb.TYPE_CODE_STRING
21004 @item TYPE_CODE_STRING
21005 A string type. Note that this is only used for certain languages with
21006 language-defined string types; C strings are not represented this way.
21008 @findex TYPE_CODE_BITSTRING
21009 @findex gdb.TYPE_CODE_BITSTRING
21010 @item TYPE_CODE_BITSTRING
21013 @findex TYPE_CODE_ERROR
21014 @findex gdb.TYPE_CODE_ERROR
21015 @item TYPE_CODE_ERROR
21016 An unknown or erroneous type.
21018 @findex TYPE_CODE_METHOD
21019 @findex gdb.TYPE_CODE_METHOD
21020 @item TYPE_CODE_METHOD
21021 A method type, as found in C@t{++} or Java.
21023 @findex TYPE_CODE_METHODPTR
21024 @findex gdb.TYPE_CODE_METHODPTR
21025 @item TYPE_CODE_METHODPTR
21026 A pointer-to-member-function.
21028 @findex TYPE_CODE_MEMBERPTR
21029 @findex gdb.TYPE_CODE_MEMBERPTR
21030 @item TYPE_CODE_MEMBERPTR
21031 A pointer-to-member.
21033 @findex TYPE_CODE_REF
21034 @findex gdb.TYPE_CODE_REF
21035 @item TYPE_CODE_REF
21038 @findex TYPE_CODE_CHAR
21039 @findex gdb.TYPE_CODE_CHAR
21040 @item TYPE_CODE_CHAR
21043 @findex TYPE_CODE_BOOL
21044 @findex gdb.TYPE_CODE_BOOL
21045 @item TYPE_CODE_BOOL
21048 @findex TYPE_CODE_COMPLEX
21049 @findex gdb.TYPE_CODE_COMPLEX
21050 @item TYPE_CODE_COMPLEX
21051 A complex float type.
21053 @findex TYPE_CODE_TYPEDEF
21054 @findex gdb.TYPE_CODE_TYPEDEF
21055 @item TYPE_CODE_TYPEDEF
21056 A typedef to some other type.
21058 @findex TYPE_CODE_NAMESPACE
21059 @findex gdb.TYPE_CODE_NAMESPACE
21060 @item TYPE_CODE_NAMESPACE
21061 A C@t{++} namespace.
21063 @findex TYPE_CODE_DECFLOAT
21064 @findex gdb.TYPE_CODE_DECFLOAT
21065 @item TYPE_CODE_DECFLOAT
21066 A decimal floating point type.
21068 @findex TYPE_CODE_INTERNAL_FUNCTION
21069 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
21070 @item TYPE_CODE_INTERNAL_FUNCTION
21071 A function internal to @value{GDBN}. This is the type used to represent
21072 convenience functions.
21075 @node Pretty Printing API
21076 @subsubsection Pretty Printing API
21078 An example output is provided (@pxref{Pretty Printing}).
21080 A pretty-printer is just an object that holds a value and implements a
21081 specific interface, defined here.
21083 @defop Operation {pretty printer} children (self)
21084 @value{GDBN} will call this method on a pretty-printer to compute the
21085 children of the pretty-printer's value.
21087 This method must return an object conforming to the Python iterator
21088 protocol. Each item returned by the iterator must be a tuple holding
21089 two elements. The first element is the ``name'' of the child; the
21090 second element is the child's value. The value can be any Python
21091 object which is convertible to a @value{GDBN} value.
21093 This method is optional. If it does not exist, @value{GDBN} will act
21094 as though the value has no children.
21097 @defop Operation {pretty printer} display_hint (self)
21098 The CLI may call this method and use its result to change the
21099 formatting of a value. The result will also be supplied to an MI
21100 consumer as a @samp{displayhint} attribute of the variable being
21103 This method is optional. If it does exist, this method must return a
21106 Some display hints are predefined by @value{GDBN}:
21110 Indicate that the object being printed is ``array-like''. The CLI
21111 uses this to respect parameters such as @code{set print elements} and
21112 @code{set print array}.
21115 Indicate that the object being printed is ``map-like'', and that the
21116 children of this value can be assumed to alternate between keys and
21120 Indicate that the object being printed is ``string-like''. If the
21121 printer's @code{to_string} method returns a Python string of some
21122 kind, then @value{GDBN} will call its internal language-specific
21123 string-printing function to format the string. For the CLI this means
21124 adding quotation marks, possibly escaping some characters, respecting
21125 @code{set print elements}, and the like.
21129 @defop Operation {pretty printer} to_string (self)
21130 @value{GDBN} will call this method to display the string
21131 representation of the value passed to the object's constructor.
21133 When printing from the CLI, if the @code{to_string} method exists,
21134 then @value{GDBN} will prepend its result to the values returned by
21135 @code{children}. Exactly how this formatting is done is dependent on
21136 the display hint, and may change as more hints are added. Also,
21137 depending on the print settings (@pxref{Print Settings}), the CLI may
21138 print just the result of @code{to_string} in a stack trace, omitting
21139 the result of @code{children}.
21141 If this method returns a string, it is printed verbatim.
21143 Otherwise, if this method returns an instance of @code{gdb.Value},
21144 then @value{GDBN} prints this value. This may result in a call to
21145 another pretty-printer.
21147 If instead the method returns a Python value which is convertible to a
21148 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21149 the resulting value. Again, this may result in a call to another
21150 pretty-printer. Python scalars (integers, floats, and booleans) and
21151 strings are convertible to @code{gdb.Value}; other types are not.
21153 Finally, if this method returns @code{None} then no further operations
21154 are peformed in this method and nothing is printed.
21156 If the result is not one of these types, an exception is raised.
21159 @node Selecting Pretty-Printers
21160 @subsubsection Selecting Pretty-Printers
21162 The Python list @code{gdb.pretty_printers} contains an array of
21163 functions or callable objects that have been registered via addition
21164 as a pretty-printer.
21165 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21166 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21169 A function on one of these lists is passed a single @code{gdb.Value}
21170 argument and should return a pretty-printer object conforming to the
21171 interface definition above (@pxref{Pretty Printing API}). If a function
21172 cannot create a pretty-printer for the value, it should return
21175 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21176 @code{gdb.Objfile} in the current program space and iteratively calls
21177 each enabled function (@pxref{Disabling Pretty-Printers})
21178 in the list for that @code{gdb.Objfile} until it receives
21179 a pretty-printer object.
21180 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21181 searches the pretty-printer list of the current program space,
21182 calling each enabled function until an object is returned.
21183 After these lists have been exhausted, it tries the global
21184 @code{gdb.pretty_printers} list, again calling each enabled function until an
21185 object is returned.
21187 The order in which the objfiles are searched is not specified. For a
21188 given list, functions are always invoked from the head of the list,
21189 and iterated over sequentially until the end of the list, or a printer
21190 object is returned.
21192 Here is an example showing how a @code{std::string} printer might be
21196 class StdStringPrinter:
21197 "Print a std::string"
21199 def __init__ (self, val):
21202 def to_string (self):
21203 return self.val['_M_dataplus']['_M_p']
21205 def display_hint (self):
21209 And here is an example showing how a lookup function for the printer
21210 example above might be written.
21213 def str_lookup_function (val):
21215 lookup_tag = val.type.tag
21216 regex = re.compile ("^std::basic_string<char,.*>$")
21217 if lookup_tag == None:
21219 if regex.match (lookup_tag):
21220 return StdStringPrinter (val)
21225 The example lookup function extracts the value's type, and attempts to
21226 match it to a type that it can pretty-print. If it is a type the
21227 printer can pretty-print, it will return a printer object. If not, it
21228 returns @code{None}.
21230 We recommend that you put your core pretty-printers into a Python
21231 package. If your pretty-printers are for use with a library, we
21232 further recommend embedding a version number into the package name.
21233 This practice will enable @value{GDBN} to load multiple versions of
21234 your pretty-printers at the same time, because they will have
21237 You should write auto-loaded code (@pxref{Auto-loading}) such that it
21238 can be evaluated multiple times without changing its meaning. An
21239 ideal auto-load file will consist solely of @code{import}s of your
21240 printer modules, followed by a call to a register pretty-printers with
21241 the current objfile.
21243 Taken as a whole, this approach will scale nicely to multiple
21244 inferiors, each potentially using a different library version.
21245 Embedding a version number in the Python package name will ensure that
21246 @value{GDBN} is able to load both sets of printers simultaneously.
21247 Then, because the search for pretty-printers is done by objfile, and
21248 because your auto-loaded code took care to register your library's
21249 printers with a specific objfile, @value{GDBN} will find the correct
21250 printers for the specific version of the library used by each
21253 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
21254 this code might appear in @code{gdb.libstdcxx.v6}:
21257 def register_printers (objfile):
21258 objfile.pretty_printers.add (str_lookup_function)
21262 And then the corresponding contents of the auto-load file would be:
21265 import gdb.libstdcxx.v6
21266 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
21269 @node Disabling Pretty-Printers
21270 @subsubsection Disabling Pretty-Printers
21271 @cindex disabling pretty-printers
21273 For various reasons a pretty-printer may not work.
21274 For example, the underlying data structure may have changed and
21275 the pretty-printer is out of date.
21277 The consequences of a broken pretty-printer are severe enough that
21278 @value{GDBN} provides support for enabling and disabling individual
21279 printers. For example, if @code{print frame-arguments} is on,
21280 a backtrace can become highly illegible if any argument is printed
21281 with a broken printer.
21283 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21284 attribute to the registered function or callable object. If this attribute
21285 is present and its value is @code{False}, the printer is disabled, otherwise
21286 the printer is enabled.
21288 @node Inferiors In Python
21289 @subsubsection Inferiors In Python
21290 @cindex inferiors in python
21292 @findex gdb.Inferior
21293 Programs which are being run under @value{GDBN} are called inferiors
21294 (@pxref{Inferiors and Programs}). Python scripts can access
21295 information about and manipulate inferiors controlled by @value{GDBN}
21296 via objects of the @code{gdb.Inferior} class.
21298 The following inferior-related functions are available in the @code{gdb}
21302 Return a tuple containing all inferior objects.
21305 A @code{gdb.Inferior} object has the following attributes:
21308 @defivar Inferior num
21309 ID of inferior, as assigned by GDB.
21312 @defivar Inferior pid
21313 Process ID of the inferior, as assigned by the underlying operating
21317 @defivar Inferior was_attached
21318 Boolean signaling whether the inferior was created using `attach', or
21319 started by @value{GDBN} itself.
21323 A @code{gdb.Inferior} object has the following methods:
21326 @defmethod Inferior threads
21327 This method returns a tuple holding all the threads which are valid
21328 when it is called. If there are no valid threads, the method will
21329 return an empty tuple.
21332 @findex gdb.read_memory
21333 @defmethod Inferior read_memory address length
21334 Read @var{length} bytes of memory from the inferior, starting at
21335 @var{address}. Returns a buffer object, which behaves much like an array
21336 or a string. It can be modified and given to the @code{gdb.write_memory}
21340 @findex gdb.write_memory
21341 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
21342 Write the contents of @var{buffer} to the inferior, starting at
21343 @var{address}. The @var{buffer} parameter must be a Python object
21344 which supports the buffer protocol, i.e., a string, an array or the
21345 object returned from @code{gdb.read_memory}. If given, @var{length}
21346 determines the number of bytes from @var{buffer} to be written.
21349 @findex gdb.search_memory
21350 @defmethod Inferior search_memory address length pattern
21351 Search a region of the inferior memory starting at @var{address} with
21352 the given @var{length} using the search pattern supplied in
21353 @var{pattern}. The @var{pattern} parameter must be a Python object
21354 which supports the buffer protocol, i.e., a string, an array or the
21355 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
21356 containing the address where the pattern was found, or @code{None} if
21357 the pattern could not be found.
21361 @node Threads In Python
21362 @subsubsection Threads In Python
21363 @cindex threads in python
21365 @findex gdb.InferiorThread
21366 Python scripts can access information about, and manipulate inferior threads
21367 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
21369 The following thread-related functions are available in the @code{gdb}
21372 @findex gdb.selected_thread
21373 @defun selected_thread
21374 This function returns the thread object for the selected thread. If there
21375 is no selected thread, this will return @code{None}.
21378 A @code{gdb.InferiorThread} object has the following attributes:
21381 @defivar InferiorThread num
21382 ID of the thread, as assigned by GDB.
21385 @defivar InferiorThread ptid
21386 ID of the thread, as assigned by the operating system. This attribute is a
21387 tuple containing three integers. The first is the Process ID (PID); the second
21388 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
21389 Either the LWPID or TID may be 0, which indicates that the operating system
21390 does not use that identifier.
21394 A @code{gdb.InferiorThread} object has the following methods:
21397 @defmethod InferiorThread switch
21398 This changes @value{GDBN}'s currently selected thread to the one represented
21402 @defmethod InferiorThread is_stopped
21403 Return a Boolean indicating whether the thread is stopped.
21406 @defmethod InferiorThread is_running
21407 Return a Boolean indicating whether the thread is running.
21410 @defmethod InferiorThread is_exited
21411 Return a Boolean indicating whether the thread is exited.
21415 @node Commands In Python
21416 @subsubsection Commands In Python
21418 @cindex commands in python
21419 @cindex python commands
21420 You can implement new @value{GDBN} CLI commands in Python. A CLI
21421 command is implemented using an instance of the @code{gdb.Command}
21422 class, most commonly using a subclass.
21424 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
21425 The object initializer for @code{Command} registers the new command
21426 with @value{GDBN}. This initializer is normally invoked from the
21427 subclass' own @code{__init__} method.
21429 @var{name} is the name of the command. If @var{name} consists of
21430 multiple words, then the initial words are looked for as prefix
21431 commands. In this case, if one of the prefix commands does not exist,
21432 an exception is raised.
21434 There is no support for multi-line commands.
21436 @var{command_class} should be one of the @samp{COMMAND_} constants
21437 defined below. This argument tells @value{GDBN} how to categorize the
21438 new command in the help system.
21440 @var{completer_class} is an optional argument. If given, it should be
21441 one of the @samp{COMPLETE_} constants defined below. This argument
21442 tells @value{GDBN} how to perform completion for this command. If not
21443 given, @value{GDBN} will attempt to complete using the object's
21444 @code{complete} method (see below); if no such method is found, an
21445 error will occur when completion is attempted.
21447 @var{prefix} is an optional argument. If @code{True}, then the new
21448 command is a prefix command; sub-commands of this command may be
21451 The help text for the new command is taken from the Python
21452 documentation string for the command's class, if there is one. If no
21453 documentation string is provided, the default value ``This command is
21454 not documented.'' is used.
21457 @cindex don't repeat Python command
21458 @defmethod Command dont_repeat
21459 By default, a @value{GDBN} command is repeated when the user enters a
21460 blank line at the command prompt. A command can suppress this
21461 behavior by invoking the @code{dont_repeat} method. This is similar
21462 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
21465 @defmethod Command invoke argument from_tty
21466 This method is called by @value{GDBN} when this command is invoked.
21468 @var{argument} is a string. It is the argument to the command, after
21469 leading and trailing whitespace has been stripped.
21471 @var{from_tty} is a boolean argument. When true, this means that the
21472 command was entered by the user at the terminal; when false it means
21473 that the command came from elsewhere.
21475 If this method throws an exception, it is turned into a @value{GDBN}
21476 @code{error} call. Otherwise, the return value is ignored.
21478 @findex gdb.string_to_argv
21479 To break @var{argument} up into an argv-like string use
21480 @code{gdb.string_to_argv}. This function behaves identically to
21481 @value{GDBN}'s internal argument lexer @code{buildargv}.
21482 It is recommended to use this for consistency.
21483 Arguments are separated by spaces and may be quoted.
21487 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
21488 ['1', '2 "3', '4 "5', "6 '7"]
21493 @cindex completion of Python commands
21494 @defmethod Command complete text word
21495 This method is called by @value{GDBN} when the user attempts
21496 completion on this command. All forms of completion are handled by
21497 this method, that is, the @key{TAB} and @key{M-?} key bindings
21498 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
21501 The arguments @var{text} and @var{word} are both strings. @var{text}
21502 holds the complete command line up to the cursor's location.
21503 @var{word} holds the last word of the command line; this is computed
21504 using a word-breaking heuristic.
21506 The @code{complete} method can return several values:
21509 If the return value is a sequence, the contents of the sequence are
21510 used as the completions. It is up to @code{complete} to ensure that the
21511 contents actually do complete the word. A zero-length sequence is
21512 allowed, it means that there were no completions available. Only
21513 string elements of the sequence are used; other elements in the
21514 sequence are ignored.
21517 If the return value is one of the @samp{COMPLETE_} constants defined
21518 below, then the corresponding @value{GDBN}-internal completion
21519 function is invoked, and its result is used.
21522 All other results are treated as though there were no available
21527 When a new command is registered, it must be declared as a member of
21528 some general class of commands. This is used to classify top-level
21529 commands in the on-line help system; note that prefix commands are not
21530 listed under their own category but rather that of their top-level
21531 command. The available classifications are represented by constants
21532 defined in the @code{gdb} module:
21535 @findex COMMAND_NONE
21536 @findex gdb.COMMAND_NONE
21538 The command does not belong to any particular class. A command in
21539 this category will not be displayed in any of the help categories.
21541 @findex COMMAND_RUNNING
21542 @findex gdb.COMMAND_RUNNING
21543 @item COMMAND_RUNNING
21544 The command is related to running the inferior. For example,
21545 @code{start}, @code{step}, and @code{continue} are in this category.
21546 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
21547 commands in this category.
21549 @findex COMMAND_DATA
21550 @findex gdb.COMMAND_DATA
21552 The command is related to data or variables. For example,
21553 @code{call}, @code{find}, and @code{print} are in this category. Type
21554 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
21557 @findex COMMAND_STACK
21558 @findex gdb.COMMAND_STACK
21559 @item COMMAND_STACK
21560 The command has to do with manipulation of the stack. For example,
21561 @code{backtrace}, @code{frame}, and @code{return} are in this
21562 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
21563 list of commands in this category.
21565 @findex COMMAND_FILES
21566 @findex gdb.COMMAND_FILES
21567 @item COMMAND_FILES
21568 This class is used for file-related commands. For example,
21569 @code{file}, @code{list} and @code{section} are in this category.
21570 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
21571 commands in this category.
21573 @findex COMMAND_SUPPORT
21574 @findex gdb.COMMAND_SUPPORT
21575 @item COMMAND_SUPPORT
21576 This should be used for ``support facilities'', generally meaning
21577 things that are useful to the user when interacting with @value{GDBN},
21578 but not related to the state of the inferior. For example,
21579 @code{help}, @code{make}, and @code{shell} are in this category. Type
21580 @kbd{help support} at the @value{GDBN} prompt to see a list of
21581 commands in this category.
21583 @findex COMMAND_STATUS
21584 @findex gdb.COMMAND_STATUS
21585 @item COMMAND_STATUS
21586 The command is an @samp{info}-related command, that is, related to the
21587 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
21588 and @code{show} are in this category. Type @kbd{help status} at the
21589 @value{GDBN} prompt to see a list of commands in this category.
21591 @findex COMMAND_BREAKPOINTS
21592 @findex gdb.COMMAND_BREAKPOINTS
21593 @item COMMAND_BREAKPOINTS
21594 The command has to do with breakpoints. For example, @code{break},
21595 @code{clear}, and @code{delete} are in this category. Type @kbd{help
21596 breakpoints} at the @value{GDBN} prompt to see a list of commands in
21599 @findex COMMAND_TRACEPOINTS
21600 @findex gdb.COMMAND_TRACEPOINTS
21601 @item COMMAND_TRACEPOINTS
21602 The command has to do with tracepoints. For example, @code{trace},
21603 @code{actions}, and @code{tfind} are in this category. Type
21604 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
21605 commands in this category.
21607 @findex COMMAND_OBSCURE
21608 @findex gdb.COMMAND_OBSCURE
21609 @item COMMAND_OBSCURE
21610 The command is only used in unusual circumstances, or is not of
21611 general interest to users. For example, @code{checkpoint},
21612 @code{fork}, and @code{stop} are in this category. Type @kbd{help
21613 obscure} at the @value{GDBN} prompt to see a list of commands in this
21616 @findex COMMAND_MAINTENANCE
21617 @findex gdb.COMMAND_MAINTENANCE
21618 @item COMMAND_MAINTENANCE
21619 The command is only useful to @value{GDBN} maintainers. The
21620 @code{maintenance} and @code{flushregs} commands are in this category.
21621 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
21622 commands in this category.
21625 A new command can use a predefined completion function, either by
21626 specifying it via an argument at initialization, or by returning it
21627 from the @code{complete} method. These predefined completion
21628 constants are all defined in the @code{gdb} module:
21631 @findex COMPLETE_NONE
21632 @findex gdb.COMPLETE_NONE
21633 @item COMPLETE_NONE
21634 This constant means that no completion should be done.
21636 @findex COMPLETE_FILENAME
21637 @findex gdb.COMPLETE_FILENAME
21638 @item COMPLETE_FILENAME
21639 This constant means that filename completion should be performed.
21641 @findex COMPLETE_LOCATION
21642 @findex gdb.COMPLETE_LOCATION
21643 @item COMPLETE_LOCATION
21644 This constant means that location completion should be done.
21645 @xref{Specify Location}.
21647 @findex COMPLETE_COMMAND
21648 @findex gdb.COMPLETE_COMMAND
21649 @item COMPLETE_COMMAND
21650 This constant means that completion should examine @value{GDBN}
21653 @findex COMPLETE_SYMBOL
21654 @findex gdb.COMPLETE_SYMBOL
21655 @item COMPLETE_SYMBOL
21656 This constant means that completion should be done using symbol names
21660 The following code snippet shows how a trivial CLI command can be
21661 implemented in Python:
21664 class HelloWorld (gdb.Command):
21665 """Greet the whole world."""
21667 def __init__ (self):
21668 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21670 def invoke (self, arg, from_tty):
21671 print "Hello, World!"
21676 The last line instantiates the class, and is necessary to trigger the
21677 registration of the command with @value{GDBN}. Depending on how the
21678 Python code is read into @value{GDBN}, you may need to import the
21679 @code{gdb} module explicitly.
21681 @node Parameters In Python
21682 @subsubsection Parameters In Python
21684 @cindex parameters in python
21685 @cindex python parameters
21686 @tindex gdb.Parameter
21688 You can implement new @value{GDBN} parameters using Python. A new
21689 parameter is implemented as an instance of the @code{gdb.Parameter}
21692 Parameters are exposed to the user via the @code{set} and
21693 @code{show} commands. @xref{Help}.
21695 There are many parameters that already exist and can be set in
21696 @value{GDBN}. Two examples are: @code{set follow fork} and
21697 @code{set charset}. Setting these parameters influences certain
21698 behavior in @value{GDBN}. Similarly, you can define parameters that
21699 can be used to influence behavior in custom Python scripts and commands.
21701 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
21702 The object initializer for @code{Parameter} registers the new
21703 parameter with @value{GDBN}. This initializer is normally invoked
21704 from the subclass' own @code{__init__} method.
21706 @var{name} is the name of the new parameter. If @var{name} consists
21707 of multiple words, then the initial words are looked for as prefix
21708 parameters. An example of this can be illustrated with the
21709 @code{set print} set of parameters. If @var{name} is
21710 @code{print foo}, then @code{print} will be searched as the prefix
21711 parameter. In this case the parameter can subsequently be accessed in
21712 @value{GDBN} as @code{set print foo}.
21714 If @var{name} consists of multiple words, and no prefix parameter group
21715 can be found, an exception is raised.
21717 @var{command-class} should be one of the @samp{COMMAND_} constants
21718 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
21719 categorize the new parameter in the help system.
21721 @var{parameter-class} should be one of the @samp{PARAM_} constants
21722 defined below. This argument tells @value{GDBN} the type of the new
21723 parameter; this information is used for input validation and
21726 If @var{parameter-class} is @code{PARAM_ENUM}, then
21727 @var{enum-sequence} must be a sequence of strings. These strings
21728 represent the possible values for the parameter.
21730 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
21731 of a fourth argument will cause an exception to be thrown.
21733 The help text for the new parameter is taken from the Python
21734 documentation string for the parameter's class, if there is one. If
21735 there is no documentation string, a default value is used.
21738 @defivar Parameter set_doc
21739 If this attribute exists, and is a string, then its value is used as
21740 the help text for this parameter's @code{set} command. The value is
21741 examined when @code{Parameter.__init__} is invoked; subsequent changes
21745 @defivar Parameter show_doc
21746 If this attribute exists, and is a string, then its value is used as
21747 the help text for this parameter's @code{show} command. The value is
21748 examined when @code{Parameter.__init__} is invoked; subsequent changes
21752 @defivar Parameter value
21753 The @code{value} attribute holds the underlying value of the
21754 parameter. It can be read and assigned to just as any other
21755 attribute. @value{GDBN} does validation when assignments are made.
21759 When a new parameter is defined, its type must be specified. The
21760 available types are represented by constants defined in the @code{gdb}
21764 @findex PARAM_BOOLEAN
21765 @findex gdb.PARAM_BOOLEAN
21766 @item PARAM_BOOLEAN
21767 The value is a plain boolean. The Python boolean values, @code{True}
21768 and @code{False} are the only valid values.
21770 @findex PARAM_AUTO_BOOLEAN
21771 @findex gdb.PARAM_AUTO_BOOLEAN
21772 @item PARAM_AUTO_BOOLEAN
21773 The value has three possible states: true, false, and @samp{auto}. In
21774 Python, true and false are represented using boolean constants, and
21775 @samp{auto} is represented using @code{None}.
21777 @findex PARAM_UINTEGER
21778 @findex gdb.PARAM_UINTEGER
21779 @item PARAM_UINTEGER
21780 The value is an unsigned integer. The value of 0 should be
21781 interpreted to mean ``unlimited''.
21783 @findex PARAM_INTEGER
21784 @findex gdb.PARAM_INTEGER
21785 @item PARAM_INTEGER
21786 The value is a signed integer. The value of 0 should be interpreted
21787 to mean ``unlimited''.
21789 @findex PARAM_STRING
21790 @findex gdb.PARAM_STRING
21792 The value is a string. When the user modifies the string, any escape
21793 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
21794 translated into corresponding characters and encoded into the current
21797 @findex PARAM_STRING_NOESCAPE
21798 @findex gdb.PARAM_STRING_NOESCAPE
21799 @item PARAM_STRING_NOESCAPE
21800 The value is a string. When the user modifies the string, escapes are
21801 passed through untranslated.
21803 @findex PARAM_OPTIONAL_FILENAME
21804 @findex gdb.PARAM_OPTIONAL_FILENAME
21805 @item PARAM_OPTIONAL_FILENAME
21806 The value is a either a filename (a string), or @code{None}.
21808 @findex PARAM_FILENAME
21809 @findex gdb.PARAM_FILENAME
21810 @item PARAM_FILENAME
21811 The value is a filename. This is just like
21812 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
21814 @findex PARAM_ZINTEGER
21815 @findex gdb.PARAM_ZINTEGER
21816 @item PARAM_ZINTEGER
21817 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
21818 is interpreted as itself.
21821 @findex gdb.PARAM_ENUM
21823 The value is a string, which must be one of a collection string
21824 constants provided when the parameter is created.
21827 @node Functions In Python
21828 @subsubsection Writing new convenience functions
21830 @cindex writing convenience functions
21831 @cindex convenience functions in python
21832 @cindex python convenience functions
21833 @tindex gdb.Function
21835 You can implement new convenience functions (@pxref{Convenience Vars})
21836 in Python. A convenience function is an instance of a subclass of the
21837 class @code{gdb.Function}.
21839 @defmethod Function __init__ name
21840 The initializer for @code{Function} registers the new function with
21841 @value{GDBN}. The argument @var{name} is the name of the function,
21842 a string. The function will be visible to the user as a convenience
21843 variable of type @code{internal function}, whose name is the same as
21844 the given @var{name}.
21846 The documentation for the new function is taken from the documentation
21847 string for the new class.
21850 @defmethod Function invoke @var{*args}
21851 When a convenience function is evaluated, its arguments are converted
21852 to instances of @code{gdb.Value}, and then the function's
21853 @code{invoke} method is called. Note that @value{GDBN} does not
21854 predetermine the arity of convenience functions. Instead, all
21855 available arguments are passed to @code{invoke}, following the
21856 standard Python calling convention. In particular, a convenience
21857 function can have default values for parameters without ill effect.
21859 The return value of this method is used as its value in the enclosing
21860 expression. If an ordinary Python value is returned, it is converted
21861 to a @code{gdb.Value} following the usual rules.
21864 The following code snippet shows how a trivial convenience function can
21865 be implemented in Python:
21868 class Greet (gdb.Function):
21869 """Return string to greet someone.
21870 Takes a name as argument."""
21872 def __init__ (self):
21873 super (Greet, self).__init__ ("greet")
21875 def invoke (self, name):
21876 return "Hello, %s!" % name.string ()
21881 The last line instantiates the class, and is necessary to trigger the
21882 registration of the function with @value{GDBN}. Depending on how the
21883 Python code is read into @value{GDBN}, you may need to import the
21884 @code{gdb} module explicitly.
21886 @node Progspaces In Python
21887 @subsubsection Program Spaces In Python
21889 @cindex progspaces in python
21890 @tindex gdb.Progspace
21892 A program space, or @dfn{progspace}, represents a symbolic view
21893 of an address space.
21894 It consists of all of the objfiles of the program.
21895 @xref{Objfiles In Python}.
21896 @xref{Inferiors and Programs, program spaces}, for more details
21897 about program spaces.
21899 The following progspace-related functions are available in the
21902 @findex gdb.current_progspace
21903 @defun current_progspace
21904 This function returns the program space of the currently selected inferior.
21905 @xref{Inferiors and Programs}.
21908 @findex gdb.progspaces
21910 Return a sequence of all the progspaces currently known to @value{GDBN}.
21913 Each progspace is represented by an instance of the @code{gdb.Progspace}
21916 @defivar Progspace filename
21917 The file name of the progspace as a string.
21920 @defivar Progspace pretty_printers
21921 The @code{pretty_printers} attribute is a list of functions. It is
21922 used to look up pretty-printers. A @code{Value} is passed to each
21923 function in order; if the function returns @code{None}, then the
21924 search continues. Otherwise, the return value should be an object
21925 which is used to format the value. @xref{Pretty Printing API}, for more
21929 @node Objfiles In Python
21930 @subsubsection Objfiles In Python
21932 @cindex objfiles in python
21933 @tindex gdb.Objfile
21935 @value{GDBN} loads symbols for an inferior from various
21936 symbol-containing files (@pxref{Files}). These include the primary
21937 executable file, any shared libraries used by the inferior, and any
21938 separate debug info files (@pxref{Separate Debug Files}).
21939 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
21941 The following objfile-related functions are available in the
21944 @findex gdb.current_objfile
21945 @defun current_objfile
21946 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
21947 sets the ``current objfile'' to the corresponding objfile. This
21948 function returns the current objfile. If there is no current objfile,
21949 this function returns @code{None}.
21952 @findex gdb.objfiles
21954 Return a sequence of all the objfiles current known to @value{GDBN}.
21955 @xref{Objfiles In Python}.
21958 Each objfile is represented by an instance of the @code{gdb.Objfile}
21961 @defivar Objfile filename
21962 The file name of the objfile as a string.
21965 @defivar Objfile pretty_printers
21966 The @code{pretty_printers} attribute is a list of functions. It is
21967 used to look up pretty-printers. A @code{Value} is passed to each
21968 function in order; if the function returns @code{None}, then the
21969 search continues. Otherwise, the return value should be an object
21970 which is used to format the value. @xref{Pretty Printing API}, for more
21974 @node Frames In Python
21975 @subsubsection Accessing inferior stack frames from Python.
21977 @cindex frames in python
21978 When the debugged program stops, @value{GDBN} is able to analyze its call
21979 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
21980 represents a frame in the stack. A @code{gdb.Frame} object is only valid
21981 while its corresponding frame exists in the inferior's stack. If you try
21982 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
21985 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
21989 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
21993 The following frame-related functions are available in the @code{gdb} module:
21995 @findex gdb.selected_frame
21996 @defun selected_frame
21997 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
22000 @defun frame_stop_reason_string reason
22001 Return a string explaining the reason why @value{GDBN} stopped unwinding
22002 frames, as expressed by the given @var{reason} code (an integer, see the
22003 @code{unwind_stop_reason} method further down in this section).
22006 A @code{gdb.Frame} object has the following methods:
22009 @defmethod Frame is_valid
22010 Returns true if the @code{gdb.Frame} object is valid, false if not.
22011 A frame object can become invalid if the frame it refers to doesn't
22012 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
22013 an exception if it is invalid at the time the method is called.
22016 @defmethod Frame name
22017 Returns the function name of the frame, or @code{None} if it can't be
22021 @defmethod Frame type
22022 Returns the type of the frame. The value can be one of
22023 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
22024 or @code{gdb.SENTINEL_FRAME}.
22027 @defmethod Frame unwind_stop_reason
22028 Return an integer representing the reason why it's not possible to find
22029 more frames toward the outermost frame. Use
22030 @code{gdb.frame_stop_reason_string} to convert the value returned by this
22031 function to a string.
22034 @defmethod Frame pc
22035 Returns the frame's resume address.
22038 @defmethod Frame block
22039 Return the frame's code block. @xref{Blocks In Python}.
22042 @defmethod Frame function
22043 Return the symbol for the function corresponding to this frame.
22044 @xref{Symbols In Python}.
22047 @defmethod Frame older
22048 Return the frame that called this frame.
22051 @defmethod Frame newer
22052 Return the frame called by this frame.
22055 @defmethod Frame find_sal
22056 Return the frame's symtab and line object.
22057 @xref{Symbol Tables In Python}.
22060 @defmethod Frame read_var variable @r{[}block@r{]}
22061 Return the value of @var{variable} in this frame. If the optional
22062 argument @var{block} is provided, search for the variable from that
22063 block; otherwise start at the frame's current block (which is
22064 determined by the frame's current program counter). @var{variable}
22065 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
22066 @code{gdb.Block} object.
22069 @defmethod Frame select
22070 Set this frame to be the selected frame. @xref{Stack, ,Examining the
22075 @node Blocks In Python
22076 @subsubsection Accessing frame blocks from Python.
22078 @cindex blocks in python
22081 Within each frame, @value{GDBN} maintains information on each block
22082 stored in that frame. These blocks are organized hierarchically, and
22083 are represented individually in Python as a @code{gdb.Block}.
22084 Please see @ref{Frames In Python}, for a more in-depth discussion on
22085 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
22086 detailed technical information on @value{GDBN}'s book-keeping of the
22089 The following block-related functions are available in the @code{gdb}
22092 @findex gdb.block_for_pc
22093 @defun block_for_pc pc
22094 Return the @code{gdb.Block} containing the given @var{pc} value. If the
22095 block cannot be found for the @var{pc} value specified, the function
22096 will return @code{None}.
22099 A @code{gdb.Block} object has the following attributes:
22102 @defivar Block start
22103 The start address of the block. This attribute is not writable.
22107 The end address of the block. This attribute is not writable.
22110 @defivar Block function
22111 The name of the block represented as a @code{gdb.Symbol}. If the
22112 block is not named, then this attribute holds @code{None}. This
22113 attribute is not writable.
22116 @defivar Block superblock
22117 The block containing this block. If this parent block does not exist,
22118 this attribute holds @code{None}. This attribute is not writable.
22122 @node Symbols In Python
22123 @subsubsection Python representation of Symbols.
22125 @cindex symbols in python
22128 @value{GDBN} represents every variable, function and type as an
22129 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
22130 Similarly, Python represents these symbols in @value{GDBN} with the
22131 @code{gdb.Symbol} object.
22133 The following symbol-related functions are available in the @code{gdb}
22136 @findex gdb.lookup_symbol
22137 @defun lookup_symbol name [block] [domain]
22138 This function searches for a symbol by name. The search scope can be
22139 restricted to the parameters defined in the optional domain and block
22142 @var{name} is the name of the symbol. It must be a string. The
22143 optional @var{block} argument restricts the search to symbols visible
22144 in that @var{block}. The @var{block} argument must be a
22145 @code{gdb.Block} object. The optional @var{domain} argument restricts
22146 the search to the domain type. The @var{domain} argument must be a
22147 domain constant defined in the @code{gdb} module and described later
22151 A @code{gdb.Symbol} object has the following attributes:
22154 @defivar Symbol symtab
22155 The symbol table in which the symbol appears. This attribute is
22156 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
22157 Python}. This attribute is not writable.
22160 @defivar Symbol name
22161 The name of the symbol as a string. This attribute is not writable.
22164 @defivar Symbol linkage_name
22165 The name of the symbol, as used by the linker (i.e., may be mangled).
22166 This attribute is not writable.
22169 @defivar Symbol print_name
22170 The name of the symbol in a form suitable for output. This is either
22171 @code{name} or @code{linkage_name}, depending on whether the user
22172 asked @value{GDBN} to display demangled or mangled names.
22175 @defivar Symbol addr_class
22176 The address class of the symbol. This classifies how to find the value
22177 of a symbol. Each address class is a constant defined in the
22178 @code{gdb} module and described later in this chapter.
22181 @defivar Symbol is_argument
22182 @code{True} if the symbol is an argument of a function.
22185 @defivar Symbol is_constant
22186 @code{True} if the symbol is a constant.
22189 @defivar Symbol is_function
22190 @code{True} if the symbol is a function or a method.
22193 @defivar Symbol is_variable
22194 @code{True} if the symbol is a variable.
22198 The available domain categories in @code{gdb.Symbol} are represented
22199 as constants in the @code{gdb} module:
22202 @findex SYMBOL_UNDEF_DOMAIN
22203 @findex gdb.SYMBOL_UNDEF_DOMAIN
22204 @item SYMBOL_UNDEF_DOMAIN
22205 This is used when a domain has not been discovered or none of the
22206 following domains apply. This usually indicates an error either
22207 in the symbol information or in @value{GDBN}'s handling of symbols.
22208 @findex SYMBOL_VAR_DOMAIN
22209 @findex gdb.SYMBOL_VAR_DOMAIN
22210 @item SYMBOL_VAR_DOMAIN
22211 This domain contains variables, function names, typedef names and enum
22213 @findex SYMBOL_STRUCT_DOMAIN
22214 @findex gdb.SYMBOL_STRUCT_DOMAIN
22215 @item SYMBOL_STRUCT_DOMAIN
22216 This domain holds struct, union and enum type names.
22217 @findex SYMBOL_LABEL_DOMAIN
22218 @findex gdb.SYMBOL_LABEL_DOMAIN
22219 @item SYMBOL_LABEL_DOMAIN
22220 This domain contains names of labels (for gotos).
22221 @findex SYMBOL_VARIABLES_DOMAIN
22222 @findex gdb.SYMBOL_VARIABLES_DOMAIN
22223 @item SYMBOL_VARIABLES_DOMAIN
22224 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
22225 contains everything minus functions and types.
22226 @findex SYMBOL_FUNCTIONS_DOMAIN
22227 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
22228 @item SYMBOL_FUNCTION_DOMAIN
22229 This domain contains all functions.
22230 @findex SYMBOL_TYPES_DOMAIN
22231 @findex gdb.SYMBOL_TYPES_DOMAIN
22232 @item SYMBOL_TYPES_DOMAIN
22233 This domain contains all types.
22236 The available address class categories in @code{gdb.Symbol} are represented
22237 as constants in the @code{gdb} module:
22240 @findex SYMBOL_LOC_UNDEF
22241 @findex gdb.SYMBOL_LOC_UNDEF
22242 @item SYMBOL_LOC_UNDEF
22243 If this is returned by address class, it indicates an error either in
22244 the symbol information or in @value{GDBN}'s handling of symbols.
22245 @findex SYMBOL_LOC_CONST
22246 @findex gdb.SYMBOL_LOC_CONST
22247 @item SYMBOL_LOC_CONST
22248 Value is constant int.
22249 @findex SYMBOL_LOC_STATIC
22250 @findex gdb.SYMBOL_LOC_STATIC
22251 @item SYMBOL_LOC_STATIC
22252 Value is at a fixed address.
22253 @findex SYMBOL_LOC_REGISTER
22254 @findex gdb.SYMBOL_LOC_REGISTER
22255 @item SYMBOL_LOC_REGISTER
22256 Value is in a register.
22257 @findex SYMBOL_LOC_ARG
22258 @findex gdb.SYMBOL_LOC_ARG
22259 @item SYMBOL_LOC_ARG
22260 Value is an argument. This value is at the offset stored within the
22261 symbol inside the frame's argument list.
22262 @findex SYMBOL_LOC_REF_ARG
22263 @findex gdb.SYMBOL_LOC_REF_ARG
22264 @item SYMBOL_LOC_REF_ARG
22265 Value address is stored in the frame's argument list. Just like
22266 @code{LOC_ARG} except that the value's address is stored at the
22267 offset, not the value itself.
22268 @findex SYMBOL_LOC_REGPARM_ADDR
22269 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
22270 @item SYMBOL_LOC_REGPARM_ADDR
22271 Value is a specified register. Just like @code{LOC_REGISTER} except
22272 the register holds the address of the argument instead of the argument
22274 @findex SYMBOL_LOC_LOCAL
22275 @findex gdb.SYMBOL_LOC_LOCAL
22276 @item SYMBOL_LOC_LOCAL
22277 Value is a local variable.
22278 @findex SYMBOL_LOC_TYPEDEF
22279 @findex gdb.SYMBOL_LOC_TYPEDEF
22280 @item SYMBOL_LOC_TYPEDEF
22281 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
22283 @findex SYMBOL_LOC_BLOCK
22284 @findex gdb.SYMBOL_LOC_BLOCK
22285 @item SYMBOL_LOC_BLOCK
22287 @findex SYMBOL_LOC_CONST_BYTES
22288 @findex gdb.SYMBOL_LOC_CONST_BYTES
22289 @item SYMBOL_LOC_CONST_BYTES
22290 Value is a byte-sequence.
22291 @findex SYMBOL_LOC_UNRESOLVED
22292 @findex gdb.SYMBOL_LOC_UNRESOLVED
22293 @item SYMBOL_LOC_UNRESOLVED
22294 Value is at a fixed address, but the address of the variable has to be
22295 determined from the minimal symbol table whenever the variable is
22297 @findex SYMBOL_LOC_OPTIMIZED_OUT
22298 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
22299 @item SYMBOL_LOC_OPTIMIZED_OUT
22300 The value does not actually exist in the program.
22301 @findex SYMBOL_LOC_COMPUTED
22302 @findex gdb.SYMBOL_LOC_COMPUTED
22303 @item SYMBOL_LOC_COMPUTED
22304 The value's address is a computed location.
22307 @node Symbol Tables In Python
22308 @subsubsection Symbol table representation in Python.
22310 @cindex symbol tables in python
22312 @tindex gdb.Symtab_and_line
22314 Access to symbol table data maintained by @value{GDBN} on the inferior
22315 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
22316 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
22317 from the @code{find_sal} method in @code{gdb.Frame} object.
22318 @xref{Frames In Python}.
22320 For more information on @value{GDBN}'s symbol table management, see
22321 @ref{Symbols, ,Examining the Symbol Table}, for more information.
22323 A @code{gdb.Symtab_and_line} object has the following attributes:
22326 @defivar Symtab_and_line symtab
22327 The symbol table object (@code{gdb.Symtab}) for this frame.
22328 This attribute is not writable.
22331 @defivar Symtab_and_line pc
22332 Indicates the current program counter address. This attribute is not
22336 @defivar Symtab_and_line line
22337 Indicates the current line number for this object. This
22338 attribute is not writable.
22342 A @code{gdb.Symtab} object has the following attributes:
22345 @defivar Symtab filename
22346 The symbol table's source filename. This attribute is not writable.
22349 @defivar Symtab objfile
22350 The symbol table's backing object file. @xref{Objfiles In Python}.
22351 This attribute is not writable.
22355 The following methods are provided:
22358 @defmethod Symtab fullname
22359 Return the symbol table's source absolute file name.
22363 @node Breakpoints In Python
22364 @subsubsection Manipulating breakpoints using Python
22366 @cindex breakpoints in python
22367 @tindex gdb.Breakpoint
22369 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
22372 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]}
22373 Create a new breakpoint. @var{spec} is a string naming the
22374 location of the breakpoint, or an expression that defines a
22375 watchpoint. The contents can be any location recognized by the
22376 @code{break} command, or in the case of a watchpoint, by the @code{watch}
22377 command. The optional @var{type} denotes the breakpoint to create
22378 from the types defined later in this chapter. This argument can be
22379 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
22380 defaults to @code{BP_BREAKPOINT}. The optional @var{wp_class}
22381 argument defines the class of watchpoint to create, if @var{type} is
22382 defined as @code{BP_WATCHPOINT}. If a watchpoint class is not
22383 provided, it is assumed to be a @var{WP_WRITE} class.
22386 The available watchpoint types represented by constants are defined in the
22391 @findex gdb.WP_READ
22393 Read only watchpoint.
22396 @findex gdb.WP_WRITE
22398 Write only watchpoint.
22401 @findex gdb.WP_ACCESS
22403 Read/Write watchpoint.
22406 @defmethod Breakpoint is_valid
22407 Return @code{True} if this @code{Breakpoint} object is valid,
22408 @code{False} otherwise. A @code{Breakpoint} object can become invalid
22409 if the user deletes the breakpoint. In this case, the object still
22410 exists, but the underlying breakpoint does not. In the cases of
22411 watchpoint scope, the watchpoint remains valid even if execution of the
22412 inferior leaves the scope of that watchpoint.
22415 @defivar Breakpoint enabled
22416 This attribute is @code{True} if the breakpoint is enabled, and
22417 @code{False} otherwise. This attribute is writable.
22420 @defivar Breakpoint silent
22421 This attribute is @code{True} if the breakpoint is silent, and
22422 @code{False} otherwise. This attribute is writable.
22424 Note that a breakpoint can also be silent if it has commands and the
22425 first command is @code{silent}. This is not reported by the
22426 @code{silent} attribute.
22429 @defivar Breakpoint thread
22430 If the breakpoint is thread-specific, this attribute holds the thread
22431 id. If the breakpoint is not thread-specific, this attribute is
22432 @code{None}. This attribute is writable.
22435 @defivar Breakpoint task
22436 If the breakpoint is Ada task-specific, this attribute holds the Ada task
22437 id. If the breakpoint is not task-specific (or the underlying
22438 language is not Ada), this attribute is @code{None}. This attribute
22442 @defivar Breakpoint ignore_count
22443 This attribute holds the ignore count for the breakpoint, an integer.
22444 This attribute is writable.
22447 @defivar Breakpoint number
22448 This attribute holds the breakpoint's number --- the identifier used by
22449 the user to manipulate the breakpoint. This attribute is not writable.
22452 @defivar Breakpoint type
22453 This attribute holds the breakpoint's type --- the identifier used to
22454 determine the actual breakpoint type or use-case. This attribute is not
22458 The available types are represented by constants defined in the @code{gdb}
22462 @findex BP_BREAKPOINT
22463 @findex gdb.BP_BREAKPOINT
22464 @item BP_BREAKPOINT
22465 Normal code breakpoint.
22467 @findex BP_WATCHPOINT
22468 @findex gdb.BP_WATCHPOINT
22469 @item BP_WATCHPOINT
22470 Watchpoint breakpoint.
22472 @findex BP_HARDWARE_WATCHPOINT
22473 @findex gdb.BP_HARDWARE_WATCHPOINT
22474 @item BP_HARDWARE_WATCHPOINT
22475 Hardware assisted watchpoint.
22477 @findex BP_READ_WATCHPOINT
22478 @findex gdb.BP_READ_WATCHPOINT
22479 @item BP_READ_WATCHPOINT
22480 Hardware assisted read watchpoint.
22482 @findex BP_ACCESS_WATCHPOINT
22483 @findex gdb.BP_ACCESS_WATCHPOINT
22484 @item BP_ACCESS_WATCHPOINT
22485 Hardware assisted access watchpoint.
22488 @defivar Breakpoint hit_count
22489 This attribute holds the hit count for the breakpoint, an integer.
22490 This attribute is writable, but currently it can only be set to zero.
22493 @defivar Breakpoint location
22494 This attribute holds the location of the breakpoint, as specified by
22495 the user. It is a string. If the breakpoint does not have a location
22496 (that is, it is a watchpoint) the attribute's value is @code{None}. This
22497 attribute is not writable.
22500 @defivar Breakpoint expression
22501 This attribute holds a breakpoint expression, as specified by
22502 the user. It is a string. If the breakpoint does not have an
22503 expression (the breakpoint is not a watchpoint) the attribute's value
22504 is @code{None}. This attribute is not writable.
22507 @defivar Breakpoint condition
22508 This attribute holds the condition of the breakpoint, as specified by
22509 the user. It is a string. If there is no condition, this attribute's
22510 value is @code{None}. This attribute is writable.
22513 @defivar Breakpoint commands
22514 This attribute holds the commands attached to the breakpoint. If
22515 there are commands, this attribute's value is a string holding all the
22516 commands, separated by newlines. If there are no commands, this
22517 attribute is @code{None}. This attribute is not writable.
22520 @node Lazy Strings In Python
22521 @subsubsection Python representation of lazy strings.
22523 @cindex lazy strings in python
22524 @tindex gdb.LazyString
22526 A @dfn{lazy string} is a string whose contents is not retrieved or
22527 encoded until it is needed.
22529 A @code{gdb.LazyString} is represented in @value{GDBN} as an
22530 @code{address} that points to a region of memory, an @code{encoding}
22531 that will be used to encode that region of memory, and a @code{length}
22532 to delimit the region of memory that represents the string. The
22533 difference between a @code{gdb.LazyString} and a string wrapped within
22534 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
22535 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
22536 retrieved and encoded during printing, while a @code{gdb.Value}
22537 wrapping a string is immediately retrieved and encoded on creation.
22539 A @code{gdb.LazyString} object has the following functions:
22541 @defmethod LazyString value
22542 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
22543 will point to the string in memory, but will lose all the delayed
22544 retrieval, encoding and handling that @value{GDBN} applies to a
22545 @code{gdb.LazyString}.
22548 @defivar LazyString address
22549 This attribute holds the address of the string. This attribute is not
22553 @defivar LazyString length
22554 This attribute holds the length of the string in characters. If the
22555 length is -1, then the string will be fetched and encoded up to the
22556 first null of appropriate width. This attribute is not writable.
22559 @defivar LazyString encoding
22560 This attribute holds the encoding that will be applied to the string
22561 when the string is printed by @value{GDBN}. If the encoding is not
22562 set, or contains an empty string, then @value{GDBN} will select the
22563 most appropriate encoding when the string is printed. This attribute
22567 @defivar LazyString type
22568 This attribute holds the type that is represented by the lazy string's
22569 type. For a lazy string this will always be a pointer type. To
22570 resolve this to the lazy string's character type, use the type's
22571 @code{target} method. @xref{Types In Python}. This attribute is not
22576 @subsection Auto-loading
22577 @cindex auto-loading, Python
22579 When a new object file is read (for example, due to the @code{file}
22580 command, or because the inferior has loaded a shared library),
22581 @value{GDBN} will look for Python support scripts in several ways:
22582 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
22585 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
22586 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
22587 * Which flavor to choose?::
22590 The auto-loading feature is useful for supplying application-specific
22591 debugging commands and scripts.
22593 Auto-loading can be enabled or disabled.
22596 @kindex maint set python auto-load
22597 @item maint set python auto-load [yes|no]
22598 Enable or disable the Python auto-loading feature.
22600 @kindex maint show python auto-load
22601 @item maint show python auto-load
22602 Show whether Python auto-loading is enabled or disabled.
22605 When reading an auto-loaded file, @value{GDBN} sets the
22606 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
22607 function (@pxref{Objfiles In Python}). This can be useful for
22608 registering objfile-specific pretty-printers.
22610 @node objfile-gdb.py file
22611 @subsubsection The @file{@var{objfile}-gdb.py} file
22612 @cindex @file{@var{objfile}-gdb.py}
22614 When a new object file is read, @value{GDBN} looks for
22615 a file named @file{@var{objfile}-gdb.py},
22616 where @var{objfile} is the object file's real name, formed by ensuring
22617 that the file name is absolute, following all symlinks, and resolving
22618 @code{.} and @code{..} components. If this file exists and is
22619 readable, @value{GDBN} will evaluate it as a Python script.
22621 If this file does not exist, and if the parameter
22622 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
22623 then @value{GDBN} will look for @var{real-name} in all of the
22624 directories mentioned in the value of @code{debug-file-directory}.
22626 Finally, if this file does not exist, then @value{GDBN} will look for
22627 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
22628 @var{data-directory} is @value{GDBN}'s data directory (available via
22629 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
22630 is the object file's real name, as described above.
22632 @value{GDBN} does not track which files it has already auto-loaded this way.
22633 @value{GDBN} will load the associated script every time the corresponding
22634 @var{objfile} is opened.
22635 So your @file{-gdb.py} file should be careful to avoid errors if it
22636 is evaluated more than once.
22638 @node .debug_gdb_scripts section
22639 @subsubsection The @code{.debug_gdb_scripts} section
22640 @cindex @code{.debug_gdb_scripts} section
22642 For systems using file formats like ELF and COFF,
22643 when @value{GDBN} loads a new object file
22644 it will look for a special section named @samp{.debug_gdb_scripts}.
22645 If this section exists, its contents is a list of names of scripts to load.
22647 @value{GDBN} will look for each specified script file first in the
22648 current directory and then along the source search path
22649 (@pxref{Source Path, ,Specifying Source Directories}),
22650 except that @file{$cdir} is not searched, since the compilation
22651 directory is not relevant to scripts.
22653 Entries can be placed in section @code{.debug_gdb_scripts} with,
22654 for example, this GCC macro:
22657 /* Note: The "MS" section flags are to remote duplicates. */
22658 #define DEFINE_GDB_SCRIPT(script_name) \
22660 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
22662 .asciz \"" script_name "\"\n\
22668 Then one can reference the macro in a header or source file like this:
22671 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
22674 The script name may include directories if desired.
22676 If the macro is put in a header, any application or library
22677 using this header will get a reference to the specified script.
22679 @node Which flavor to choose?
22680 @subsubsection Which flavor to choose?
22682 Given the multiple ways of auto-loading Python scripts, it might not always
22683 be clear which one to choose. This section provides some guidance.
22685 Benefits of the @file{-gdb.py} way:
22689 Can be used with file formats that don't support multiple sections.
22692 Ease of finding scripts for public libraries.
22694 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
22695 in the source search path.
22696 For publicly installed libraries, e.g., @file{libstdc++}, there typically
22697 isn't a source directory in which to find the script.
22700 Doesn't require source code additions.
22703 Benefits of the @code{.debug_gdb_scripts} way:
22707 Works with static linking.
22709 Scripts for libraries done the @file{-gdb.py} way require an objfile to
22710 trigger their loading. When an application is statically linked the only
22711 objfile available is the executable, and it is cumbersome to attach all the
22712 scripts from all the input libraries to the executable's @file{-gdb.py} script.
22715 Works with classes that are entirely inlined.
22717 Some classes can be entirely inlined, and thus there may not be an associated
22718 shared library to attach a @file{-gdb.py} script to.
22721 Scripts needn't be copied out of the source tree.
22723 In some circumstances, apps can be built out of large collections of internal
22724 libraries, and the build infrastructure necessary to install the
22725 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
22726 cumbersome. It may be easier to specify the scripts in the
22727 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
22728 top of the source tree to the source search path.
22732 @chapter Command Interpreters
22733 @cindex command interpreters
22735 @value{GDBN} supports multiple command interpreters, and some command
22736 infrastructure to allow users or user interface writers to switch
22737 between interpreters or run commands in other interpreters.
22739 @value{GDBN} currently supports two command interpreters, the console
22740 interpreter (sometimes called the command-line interpreter or @sc{cli})
22741 and the machine interface interpreter (or @sc{gdb/mi}). This manual
22742 describes both of these interfaces in great detail.
22744 By default, @value{GDBN} will start with the console interpreter.
22745 However, the user may choose to start @value{GDBN} with another
22746 interpreter by specifying the @option{-i} or @option{--interpreter}
22747 startup options. Defined interpreters include:
22751 @cindex console interpreter
22752 The traditional console or command-line interpreter. This is the most often
22753 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
22754 @value{GDBN} will use this interpreter.
22757 @cindex mi interpreter
22758 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
22759 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
22760 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
22764 @cindex mi2 interpreter
22765 The current @sc{gdb/mi} interface.
22768 @cindex mi1 interpreter
22769 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
22773 @cindex invoke another interpreter
22774 The interpreter being used by @value{GDBN} may not be dynamically
22775 switched at runtime. Although possible, this could lead to a very
22776 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
22777 enters the command "interpreter-set console" in a console view,
22778 @value{GDBN} would switch to using the console interpreter, rendering
22779 the IDE inoperable!
22781 @kindex interpreter-exec
22782 Although you may only choose a single interpreter at startup, you may execute
22783 commands in any interpreter from the current interpreter using the appropriate
22784 command. If you are running the console interpreter, simply use the
22785 @code{interpreter-exec} command:
22788 interpreter-exec mi "-data-list-register-names"
22791 @sc{gdb/mi} has a similar command, although it is only available in versions of
22792 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
22795 @chapter @value{GDBN} Text User Interface
22797 @cindex Text User Interface
22800 * TUI Overview:: TUI overview
22801 * TUI Keys:: TUI key bindings
22802 * TUI Single Key Mode:: TUI single key mode
22803 * TUI Commands:: TUI-specific commands
22804 * TUI Configuration:: TUI configuration variables
22807 The @value{GDBN} Text User Interface (TUI) is a terminal
22808 interface which uses the @code{curses} library to show the source
22809 file, the assembly output, the program registers and @value{GDBN}
22810 commands in separate text windows. The TUI mode is supported only
22811 on platforms where a suitable version of the @code{curses} library
22814 @pindex @value{GDBTUI}
22815 The TUI mode is enabled by default when you invoke @value{GDBN} as
22816 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
22817 You can also switch in and out of TUI mode while @value{GDBN} runs by
22818 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
22819 @xref{TUI Keys, ,TUI Key Bindings}.
22822 @section TUI Overview
22824 In TUI mode, @value{GDBN} can display several text windows:
22828 This window is the @value{GDBN} command window with the @value{GDBN}
22829 prompt and the @value{GDBN} output. The @value{GDBN} input is still
22830 managed using readline.
22833 The source window shows the source file of the program. The current
22834 line and active breakpoints are displayed in this window.
22837 The assembly window shows the disassembly output of the program.
22840 This window shows the processor registers. Registers are highlighted
22841 when their values change.
22844 The source and assembly windows show the current program position
22845 by highlighting the current line and marking it with a @samp{>} marker.
22846 Breakpoints are indicated with two markers. The first marker
22847 indicates the breakpoint type:
22851 Breakpoint which was hit at least once.
22854 Breakpoint which was never hit.
22857 Hardware breakpoint which was hit at least once.
22860 Hardware breakpoint which was never hit.
22863 The second marker indicates whether the breakpoint is enabled or not:
22867 Breakpoint is enabled.
22870 Breakpoint is disabled.
22873 The source, assembly and register windows are updated when the current
22874 thread changes, when the frame changes, or when the program counter
22877 These windows are not all visible at the same time. The command
22878 window is always visible. The others can be arranged in several
22889 source and assembly,
22892 source and registers, or
22895 assembly and registers.
22898 A status line above the command window shows the following information:
22902 Indicates the current @value{GDBN} target.
22903 (@pxref{Targets, ,Specifying a Debugging Target}).
22906 Gives the current process or thread number.
22907 When no process is being debugged, this field is set to @code{No process}.
22910 Gives the current function name for the selected frame.
22911 The name is demangled if demangling is turned on (@pxref{Print Settings}).
22912 When there is no symbol corresponding to the current program counter,
22913 the string @code{??} is displayed.
22916 Indicates the current line number for the selected frame.
22917 When the current line number is not known, the string @code{??} is displayed.
22920 Indicates the current program counter address.
22924 @section TUI Key Bindings
22925 @cindex TUI key bindings
22927 The TUI installs several key bindings in the readline keymaps
22928 (@pxref{Command Line Editing}). The following key bindings
22929 are installed for both TUI mode and the @value{GDBN} standard mode.
22938 Enter or leave the TUI mode. When leaving the TUI mode,
22939 the curses window management stops and @value{GDBN} operates using
22940 its standard mode, writing on the terminal directly. When reentering
22941 the TUI mode, control is given back to the curses windows.
22942 The screen is then refreshed.
22946 Use a TUI layout with only one window. The layout will
22947 either be @samp{source} or @samp{assembly}. When the TUI mode
22948 is not active, it will switch to the TUI mode.
22950 Think of this key binding as the Emacs @kbd{C-x 1} binding.
22954 Use a TUI layout with at least two windows. When the current
22955 layout already has two windows, the next layout with two windows is used.
22956 When a new layout is chosen, one window will always be common to the
22957 previous layout and the new one.
22959 Think of it as the Emacs @kbd{C-x 2} binding.
22963 Change the active window. The TUI associates several key bindings
22964 (like scrolling and arrow keys) with the active window. This command
22965 gives the focus to the next TUI window.
22967 Think of it as the Emacs @kbd{C-x o} binding.
22971 Switch in and out of the TUI SingleKey mode that binds single
22972 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
22975 The following key bindings only work in the TUI mode:
22980 Scroll the active window one page up.
22984 Scroll the active window one page down.
22988 Scroll the active window one line up.
22992 Scroll the active window one line down.
22996 Scroll the active window one column left.
23000 Scroll the active window one column right.
23004 Refresh the screen.
23007 Because the arrow keys scroll the active window in the TUI mode, they
23008 are not available for their normal use by readline unless the command
23009 window has the focus. When another window is active, you must use
23010 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
23011 and @kbd{C-f} to control the command window.
23013 @node TUI Single Key Mode
23014 @section TUI Single Key Mode
23015 @cindex TUI single key mode
23017 The TUI also provides a @dfn{SingleKey} mode, which binds several
23018 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
23019 switch into this mode, where the following key bindings are used:
23022 @kindex c @r{(SingleKey TUI key)}
23026 @kindex d @r{(SingleKey TUI key)}
23030 @kindex f @r{(SingleKey TUI key)}
23034 @kindex n @r{(SingleKey TUI key)}
23038 @kindex q @r{(SingleKey TUI key)}
23040 exit the SingleKey mode.
23042 @kindex r @r{(SingleKey TUI key)}
23046 @kindex s @r{(SingleKey TUI key)}
23050 @kindex u @r{(SingleKey TUI key)}
23054 @kindex v @r{(SingleKey TUI key)}
23058 @kindex w @r{(SingleKey TUI key)}
23063 Other keys temporarily switch to the @value{GDBN} command prompt.
23064 The key that was pressed is inserted in the editing buffer so that
23065 it is possible to type most @value{GDBN} commands without interaction
23066 with the TUI SingleKey mode. Once the command is entered the TUI
23067 SingleKey mode is restored. The only way to permanently leave
23068 this mode is by typing @kbd{q} or @kbd{C-x s}.
23072 @section TUI-specific Commands
23073 @cindex TUI commands
23075 The TUI has specific commands to control the text windows.
23076 These commands are always available, even when @value{GDBN} is not in
23077 the TUI mode. When @value{GDBN} is in the standard mode, most
23078 of these commands will automatically switch to the TUI mode.
23080 Note that if @value{GDBN}'s @code{stdout} is not connected to a
23081 terminal, or @value{GDBN} has been started with the machine interface
23082 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
23083 these commands will fail with an error, because it would not be
23084 possible or desirable to enable curses window management.
23089 List and give the size of all displayed windows.
23093 Display the next layout.
23096 Display the previous layout.
23099 Display the source window only.
23102 Display the assembly window only.
23105 Display the source and assembly window.
23108 Display the register window together with the source or assembly window.
23112 Make the next window active for scrolling.
23115 Make the previous window active for scrolling.
23118 Make the source window active for scrolling.
23121 Make the assembly window active for scrolling.
23124 Make the register window active for scrolling.
23127 Make the command window active for scrolling.
23131 Refresh the screen. This is similar to typing @kbd{C-L}.
23133 @item tui reg float
23135 Show the floating point registers in the register window.
23137 @item tui reg general
23138 Show the general registers in the register window.
23141 Show the next register group. The list of register groups as well as
23142 their order is target specific. The predefined register groups are the
23143 following: @code{general}, @code{float}, @code{system}, @code{vector},
23144 @code{all}, @code{save}, @code{restore}.
23146 @item tui reg system
23147 Show the system registers in the register window.
23151 Update the source window and the current execution point.
23153 @item winheight @var{name} +@var{count}
23154 @itemx winheight @var{name} -@var{count}
23156 Change the height of the window @var{name} by @var{count}
23157 lines. Positive counts increase the height, while negative counts
23160 @item tabset @var{nchars}
23162 Set the width of tab stops to be @var{nchars} characters.
23165 @node TUI Configuration
23166 @section TUI Configuration Variables
23167 @cindex TUI configuration variables
23169 Several configuration variables control the appearance of TUI windows.
23172 @item set tui border-kind @var{kind}
23173 @kindex set tui border-kind
23174 Select the border appearance for the source, assembly and register windows.
23175 The possible values are the following:
23178 Use a space character to draw the border.
23181 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
23184 Use the Alternate Character Set to draw the border. The border is
23185 drawn using character line graphics if the terminal supports them.
23188 @item set tui border-mode @var{mode}
23189 @kindex set tui border-mode
23190 @itemx set tui active-border-mode @var{mode}
23191 @kindex set tui active-border-mode
23192 Select the display attributes for the borders of the inactive windows
23193 or the active window. The @var{mode} can be one of the following:
23196 Use normal attributes to display the border.
23202 Use reverse video mode.
23205 Use half bright mode.
23207 @item half-standout
23208 Use half bright and standout mode.
23211 Use extra bright or bold mode.
23213 @item bold-standout
23214 Use extra bright or bold and standout mode.
23219 @chapter Using @value{GDBN} under @sc{gnu} Emacs
23222 @cindex @sc{gnu} Emacs
23223 A special interface allows you to use @sc{gnu} Emacs to view (and
23224 edit) the source files for the program you are debugging with
23227 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
23228 executable file you want to debug as an argument. This command starts
23229 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
23230 created Emacs buffer.
23231 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
23233 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
23238 All ``terminal'' input and output goes through an Emacs buffer, called
23241 This applies both to @value{GDBN} commands and their output, and to the input
23242 and output done by the program you are debugging.
23244 This is useful because it means that you can copy the text of previous
23245 commands and input them again; you can even use parts of the output
23248 All the facilities of Emacs' Shell mode are available for interacting
23249 with your program. In particular, you can send signals the usual
23250 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
23254 @value{GDBN} displays source code through Emacs.
23256 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
23257 source file for that frame and puts an arrow (@samp{=>}) at the
23258 left margin of the current line. Emacs uses a separate buffer for
23259 source display, and splits the screen to show both your @value{GDBN} session
23262 Explicit @value{GDBN} @code{list} or search commands still produce output as
23263 usual, but you probably have no reason to use them from Emacs.
23266 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
23267 a graphical mode, enabled by default, which provides further buffers
23268 that can control the execution and describe the state of your program.
23269 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
23271 If you specify an absolute file name when prompted for the @kbd{M-x
23272 gdb} argument, then Emacs sets your current working directory to where
23273 your program resides. If you only specify the file name, then Emacs
23274 sets your current working directory to to the directory associated
23275 with the previous buffer. In this case, @value{GDBN} may find your
23276 program by searching your environment's @code{PATH} variable, but on
23277 some operating systems it might not find the source. So, although the
23278 @value{GDBN} input and output session proceeds normally, the auxiliary
23279 buffer does not display the current source and line of execution.
23281 The initial working directory of @value{GDBN} is printed on the top
23282 line of the GUD buffer and this serves as a default for the commands
23283 that specify files for @value{GDBN} to operate on. @xref{Files,
23284 ,Commands to Specify Files}.
23286 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
23287 need to call @value{GDBN} by a different name (for example, if you
23288 keep several configurations around, with different names) you can
23289 customize the Emacs variable @code{gud-gdb-command-name} to run the
23292 In the GUD buffer, you can use these special Emacs commands in
23293 addition to the standard Shell mode commands:
23297 Describe the features of Emacs' GUD Mode.
23300 Execute to another source line, like the @value{GDBN} @code{step} command; also
23301 update the display window to show the current file and location.
23304 Execute to next source line in this function, skipping all function
23305 calls, like the @value{GDBN} @code{next} command. Then update the display window
23306 to show the current file and location.
23309 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
23310 display window accordingly.
23313 Execute until exit from the selected stack frame, like the @value{GDBN}
23314 @code{finish} command.
23317 Continue execution of your program, like the @value{GDBN} @code{continue}
23321 Go up the number of frames indicated by the numeric argument
23322 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
23323 like the @value{GDBN} @code{up} command.
23326 Go down the number of frames indicated by the numeric argument, like the
23327 @value{GDBN} @code{down} command.
23330 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
23331 tells @value{GDBN} to set a breakpoint on the source line point is on.
23333 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
23334 separate frame which shows a backtrace when the GUD buffer is current.
23335 Move point to any frame in the stack and type @key{RET} to make it
23336 become the current frame and display the associated source in the
23337 source buffer. Alternatively, click @kbd{Mouse-2} to make the
23338 selected frame become the current one. In graphical mode, the
23339 speedbar displays watch expressions.
23341 If you accidentally delete the source-display buffer, an easy way to get
23342 it back is to type the command @code{f} in the @value{GDBN} buffer, to
23343 request a frame display; when you run under Emacs, this recreates
23344 the source buffer if necessary to show you the context of the current
23347 The source files displayed in Emacs are in ordinary Emacs buffers
23348 which are visiting the source files in the usual way. You can edit
23349 the files with these buffers if you wish; but keep in mind that @value{GDBN}
23350 communicates with Emacs in terms of line numbers. If you add or
23351 delete lines from the text, the line numbers that @value{GDBN} knows cease
23352 to correspond properly with the code.
23354 A more detailed description of Emacs' interaction with @value{GDBN} is
23355 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
23358 @c The following dropped because Epoch is nonstandard. Reactivate
23359 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
23361 @kindex Emacs Epoch environment
23365 Version 18 of @sc{gnu} Emacs has a built-in window system
23366 called the @code{epoch}
23367 environment. Users of this environment can use a new command,
23368 @code{inspect} which performs identically to @code{print} except that
23369 each value is printed in its own window.
23374 @chapter The @sc{gdb/mi} Interface
23376 @unnumberedsec Function and Purpose
23378 @cindex @sc{gdb/mi}, its purpose
23379 @sc{gdb/mi} is a line based machine oriented text interface to
23380 @value{GDBN} and is activated by specifying using the
23381 @option{--interpreter} command line option (@pxref{Mode Options}). It
23382 is specifically intended to support the development of systems which
23383 use the debugger as just one small component of a larger system.
23385 This chapter is a specification of the @sc{gdb/mi} interface. It is written
23386 in the form of a reference manual.
23388 Note that @sc{gdb/mi} is still under construction, so some of the
23389 features described below are incomplete and subject to change
23390 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
23392 @unnumberedsec Notation and Terminology
23394 @cindex notational conventions, for @sc{gdb/mi}
23395 This chapter uses the following notation:
23399 @code{|} separates two alternatives.
23402 @code{[ @var{something} ]} indicates that @var{something} is optional:
23403 it may or may not be given.
23406 @code{( @var{group} )*} means that @var{group} inside the parentheses
23407 may repeat zero or more times.
23410 @code{( @var{group} )+} means that @var{group} inside the parentheses
23411 may repeat one or more times.
23414 @code{"@var{string}"} means a literal @var{string}.
23418 @heading Dependencies
23422 * GDB/MI General Design::
23423 * GDB/MI Command Syntax::
23424 * GDB/MI Compatibility with CLI::
23425 * GDB/MI Development and Front Ends::
23426 * GDB/MI Output Records::
23427 * GDB/MI Simple Examples::
23428 * GDB/MI Command Description Format::
23429 * GDB/MI Breakpoint Commands::
23430 * GDB/MI Program Context::
23431 * GDB/MI Thread Commands::
23432 * GDB/MI Program Execution::
23433 * GDB/MI Stack Manipulation::
23434 * GDB/MI Variable Objects::
23435 * GDB/MI Data Manipulation::
23436 * GDB/MI Tracepoint Commands::
23437 * GDB/MI Symbol Query::
23438 * GDB/MI File Commands::
23440 * GDB/MI Kod Commands::
23441 * GDB/MI Memory Overlay Commands::
23442 * GDB/MI Signal Handling Commands::
23444 * GDB/MI Target Manipulation::
23445 * GDB/MI File Transfer Commands::
23446 * GDB/MI Miscellaneous Commands::
23449 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23450 @node GDB/MI General Design
23451 @section @sc{gdb/mi} General Design
23452 @cindex GDB/MI General Design
23454 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
23455 parts---commands sent to @value{GDBN}, responses to those commands
23456 and notifications. Each command results in exactly one response,
23457 indicating either successful completion of the command, or an error.
23458 For the commands that do not resume the target, the response contains the
23459 requested information. For the commands that resume the target, the
23460 response only indicates whether the target was successfully resumed.
23461 Notifications is the mechanism for reporting changes in the state of the
23462 target, or in @value{GDBN} state, that cannot conveniently be associated with
23463 a command and reported as part of that command response.
23465 The important examples of notifications are:
23469 Exec notifications. These are used to report changes in
23470 target state---when a target is resumed, or stopped. It would not
23471 be feasible to include this information in response of resuming
23472 commands, because one resume commands can result in multiple events in
23473 different threads. Also, quite some time may pass before any event
23474 happens in the target, while a frontend needs to know whether the resuming
23475 command itself was successfully executed.
23478 Console output, and status notifications. Console output
23479 notifications are used to report output of CLI commands, as well as
23480 diagnostics for other commands. Status notifications are used to
23481 report the progress of a long-running operation. Naturally, including
23482 this information in command response would mean no output is produced
23483 until the command is finished, which is undesirable.
23486 General notifications. Commands may have various side effects on
23487 the @value{GDBN} or target state beyond their official purpose. For example,
23488 a command may change the selected thread. Although such changes can
23489 be included in command response, using notification allows for more
23490 orthogonal frontend design.
23494 There's no guarantee that whenever an MI command reports an error,
23495 @value{GDBN} or the target are in any specific state, and especially,
23496 the state is not reverted to the state before the MI command was
23497 processed. Therefore, whenever an MI command results in an error,
23498 we recommend that the frontend refreshes all the information shown in
23499 the user interface.
23503 * Context management::
23504 * Asynchronous and non-stop modes::
23508 @node Context management
23509 @subsection Context management
23511 In most cases when @value{GDBN} accesses the target, this access is
23512 done in context of a specific thread and frame (@pxref{Frames}).
23513 Often, even when accessing global data, the target requires that a thread
23514 be specified. The CLI interface maintains the selected thread and frame,
23515 and supplies them to target on each command. This is convenient,
23516 because a command line user would not want to specify that information
23517 explicitly on each command, and because user interacts with
23518 @value{GDBN} via a single terminal, so no confusion is possible as
23519 to what thread and frame are the current ones.
23521 In the case of MI, the concept of selected thread and frame is less
23522 useful. First, a frontend can easily remember this information
23523 itself. Second, a graphical frontend can have more than one window,
23524 each one used for debugging a different thread, and the frontend might
23525 want to access additional threads for internal purposes. This
23526 increases the risk that by relying on implicitly selected thread, the
23527 frontend may be operating on a wrong one. Therefore, each MI command
23528 should explicitly specify which thread and frame to operate on. To
23529 make it possible, each MI command accepts the @samp{--thread} and
23530 @samp{--frame} options, the value to each is @value{GDBN} identifier
23531 for thread and frame to operate on.
23533 Usually, each top-level window in a frontend allows the user to select
23534 a thread and a frame, and remembers the user selection for further
23535 operations. However, in some cases @value{GDBN} may suggest that the
23536 current thread be changed. For example, when stopping on a breakpoint
23537 it is reasonable to switch to the thread where breakpoint is hit. For
23538 another example, if the user issues the CLI @samp{thread} command via
23539 the frontend, it is desirable to change the frontend's selected thread to the
23540 one specified by user. @value{GDBN} communicates the suggestion to
23541 change current thread using the @samp{=thread-selected} notification.
23542 No such notification is available for the selected frame at the moment.
23544 Note that historically, MI shares the selected thread with CLI, so
23545 frontends used the @code{-thread-select} to execute commands in the
23546 right context. However, getting this to work right is cumbersome. The
23547 simplest way is for frontend to emit @code{-thread-select} command
23548 before every command. This doubles the number of commands that need
23549 to be sent. The alternative approach is to suppress @code{-thread-select}
23550 if the selected thread in @value{GDBN} is supposed to be identical to the
23551 thread the frontend wants to operate on. However, getting this
23552 optimization right can be tricky. In particular, if the frontend
23553 sends several commands to @value{GDBN}, and one of the commands changes the
23554 selected thread, then the behaviour of subsequent commands will
23555 change. So, a frontend should either wait for response from such
23556 problematic commands, or explicitly add @code{-thread-select} for
23557 all subsequent commands. No frontend is known to do this exactly
23558 right, so it is suggested to just always pass the @samp{--thread} and
23559 @samp{--frame} options.
23561 @node Asynchronous and non-stop modes
23562 @subsection Asynchronous command execution and non-stop mode
23564 On some targets, @value{GDBN} is capable of processing MI commands
23565 even while the target is running. This is called @dfn{asynchronous
23566 command execution} (@pxref{Background Execution}). The frontend may
23567 specify a preferrence for asynchronous execution using the
23568 @code{-gdb-set target-async 1} command, which should be emitted before
23569 either running the executable or attaching to the target. After the
23570 frontend has started the executable or attached to the target, it can
23571 find if asynchronous execution is enabled using the
23572 @code{-list-target-features} command.
23574 Even if @value{GDBN} can accept a command while target is running,
23575 many commands that access the target do not work when the target is
23576 running. Therefore, asynchronous command execution is most useful
23577 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
23578 it is possible to examine the state of one thread, while other threads
23581 When a given thread is running, MI commands that try to access the
23582 target in the context of that thread may not work, or may work only on
23583 some targets. In particular, commands that try to operate on thread's
23584 stack will not work, on any target. Commands that read memory, or
23585 modify breakpoints, may work or not work, depending on the target. Note
23586 that even commands that operate on global state, such as @code{print},
23587 @code{set}, and breakpoint commands, still access the target in the
23588 context of a specific thread, so frontend should try to find a
23589 stopped thread and perform the operation on that thread (using the
23590 @samp{--thread} option).
23592 Which commands will work in the context of a running thread is
23593 highly target dependent. However, the two commands
23594 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
23595 to find the state of a thread, will always work.
23597 @node Thread groups
23598 @subsection Thread groups
23599 @value{GDBN} may be used to debug several processes at the same time.
23600 On some platfroms, @value{GDBN} may support debugging of several
23601 hardware systems, each one having several cores with several different
23602 processes running on each core. This section describes the MI
23603 mechanism to support such debugging scenarios.
23605 The key observation is that regardless of the structure of the
23606 target, MI can have a global list of threads, because most commands that
23607 accept the @samp{--thread} option do not need to know what process that
23608 thread belongs to. Therefore, it is not necessary to introduce
23609 neither additional @samp{--process} option, nor an notion of the
23610 current process in the MI interface. The only strictly new feature
23611 that is required is the ability to find how the threads are grouped
23614 To allow the user to discover such grouping, and to support arbitrary
23615 hierarchy of machines/cores/processes, MI introduces the concept of a
23616 @dfn{thread group}. Thread group is a collection of threads and other
23617 thread groups. A thread group always has a string identifier, a type,
23618 and may have additional attributes specific to the type. A new
23619 command, @code{-list-thread-groups}, returns the list of top-level
23620 thread groups, which correspond to processes that @value{GDBN} is
23621 debugging at the moment. By passing an identifier of a thread group
23622 to the @code{-list-thread-groups} command, it is possible to obtain
23623 the members of specific thread group.
23625 To allow the user to easily discover processes, and other objects, he
23626 wishes to debug, a concept of @dfn{available thread group} is
23627 introduced. Available thread group is an thread group that
23628 @value{GDBN} is not debugging, but that can be attached to, using the
23629 @code{-target-attach} command. The list of available top-level thread
23630 groups can be obtained using @samp{-list-thread-groups --available}.
23631 In general, the content of a thread group may be only retrieved only
23632 after attaching to that thread group.
23634 Thread groups are related to inferiors (@pxref{Inferiors and
23635 Programs}). Each inferior corresponds to a thread group of a special
23636 type @samp{process}, and some additional operations are permitted on
23637 such thread groups.
23639 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23640 @node GDB/MI Command Syntax
23641 @section @sc{gdb/mi} Command Syntax
23644 * GDB/MI Input Syntax::
23645 * GDB/MI Output Syntax::
23648 @node GDB/MI Input Syntax
23649 @subsection @sc{gdb/mi} Input Syntax
23651 @cindex input syntax for @sc{gdb/mi}
23652 @cindex @sc{gdb/mi}, input syntax
23654 @item @var{command} @expansion{}
23655 @code{@var{cli-command} | @var{mi-command}}
23657 @item @var{cli-command} @expansion{}
23658 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
23659 @var{cli-command} is any existing @value{GDBN} CLI command.
23661 @item @var{mi-command} @expansion{}
23662 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
23663 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
23665 @item @var{token} @expansion{}
23666 "any sequence of digits"
23668 @item @var{option} @expansion{}
23669 @code{"-" @var{parameter} [ " " @var{parameter} ]}
23671 @item @var{parameter} @expansion{}
23672 @code{@var{non-blank-sequence} | @var{c-string}}
23674 @item @var{operation} @expansion{}
23675 @emph{any of the operations described in this chapter}
23677 @item @var{non-blank-sequence} @expansion{}
23678 @emph{anything, provided it doesn't contain special characters such as
23679 "-", @var{nl}, """ and of course " "}
23681 @item @var{c-string} @expansion{}
23682 @code{""" @var{seven-bit-iso-c-string-content} """}
23684 @item @var{nl} @expansion{}
23693 The CLI commands are still handled by the @sc{mi} interpreter; their
23694 output is described below.
23697 The @code{@var{token}}, when present, is passed back when the command
23701 Some @sc{mi} commands accept optional arguments as part of the parameter
23702 list. Each option is identified by a leading @samp{-} (dash) and may be
23703 followed by an optional argument parameter. Options occur first in the
23704 parameter list and can be delimited from normal parameters using
23705 @samp{--} (this is useful when some parameters begin with a dash).
23712 We want easy access to the existing CLI syntax (for debugging).
23715 We want it to be easy to spot a @sc{mi} operation.
23718 @node GDB/MI Output Syntax
23719 @subsection @sc{gdb/mi} Output Syntax
23721 @cindex output syntax of @sc{gdb/mi}
23722 @cindex @sc{gdb/mi}, output syntax
23723 The output from @sc{gdb/mi} consists of zero or more out-of-band records
23724 followed, optionally, by a single result record. This result record
23725 is for the most recent command. The sequence of output records is
23726 terminated by @samp{(gdb)}.
23728 If an input command was prefixed with a @code{@var{token}} then the
23729 corresponding output for that command will also be prefixed by that same
23733 @item @var{output} @expansion{}
23734 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
23736 @item @var{result-record} @expansion{}
23737 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
23739 @item @var{out-of-band-record} @expansion{}
23740 @code{@var{async-record} | @var{stream-record}}
23742 @item @var{async-record} @expansion{}
23743 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
23745 @item @var{exec-async-output} @expansion{}
23746 @code{[ @var{token} ] "*" @var{async-output}}
23748 @item @var{status-async-output} @expansion{}
23749 @code{[ @var{token} ] "+" @var{async-output}}
23751 @item @var{notify-async-output} @expansion{}
23752 @code{[ @var{token} ] "=" @var{async-output}}
23754 @item @var{async-output} @expansion{}
23755 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
23757 @item @var{result-class} @expansion{}
23758 @code{"done" | "running" | "connected" | "error" | "exit"}
23760 @item @var{async-class} @expansion{}
23761 @code{"stopped" | @var{others}} (where @var{others} will be added
23762 depending on the needs---this is still in development).
23764 @item @var{result} @expansion{}
23765 @code{ @var{variable} "=" @var{value}}
23767 @item @var{variable} @expansion{}
23768 @code{ @var{string} }
23770 @item @var{value} @expansion{}
23771 @code{ @var{const} | @var{tuple} | @var{list} }
23773 @item @var{const} @expansion{}
23774 @code{@var{c-string}}
23776 @item @var{tuple} @expansion{}
23777 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
23779 @item @var{list} @expansion{}
23780 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
23781 @var{result} ( "," @var{result} )* "]" }
23783 @item @var{stream-record} @expansion{}
23784 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
23786 @item @var{console-stream-output} @expansion{}
23787 @code{"~" @var{c-string}}
23789 @item @var{target-stream-output} @expansion{}
23790 @code{"@@" @var{c-string}}
23792 @item @var{log-stream-output} @expansion{}
23793 @code{"&" @var{c-string}}
23795 @item @var{nl} @expansion{}
23798 @item @var{token} @expansion{}
23799 @emph{any sequence of digits}.
23807 All output sequences end in a single line containing a period.
23810 The @code{@var{token}} is from the corresponding request. Note that
23811 for all async output, while the token is allowed by the grammar and
23812 may be output by future versions of @value{GDBN} for select async
23813 output messages, it is generally omitted. Frontends should treat
23814 all async output as reporting general changes in the state of the
23815 target and there should be no need to associate async output to any
23819 @cindex status output in @sc{gdb/mi}
23820 @var{status-async-output} contains on-going status information about the
23821 progress of a slow operation. It can be discarded. All status output is
23822 prefixed by @samp{+}.
23825 @cindex async output in @sc{gdb/mi}
23826 @var{exec-async-output} contains asynchronous state change on the target
23827 (stopped, started, disappeared). All async output is prefixed by
23831 @cindex notify output in @sc{gdb/mi}
23832 @var{notify-async-output} contains supplementary information that the
23833 client should handle (e.g., a new breakpoint information). All notify
23834 output is prefixed by @samp{=}.
23837 @cindex console output in @sc{gdb/mi}
23838 @var{console-stream-output} is output that should be displayed as is in the
23839 console. It is the textual response to a CLI command. All the console
23840 output is prefixed by @samp{~}.
23843 @cindex target output in @sc{gdb/mi}
23844 @var{target-stream-output} is the output produced by the target program.
23845 All the target output is prefixed by @samp{@@}.
23848 @cindex log output in @sc{gdb/mi}
23849 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
23850 instance messages that should be displayed as part of an error log. All
23851 the log output is prefixed by @samp{&}.
23854 @cindex list output in @sc{gdb/mi}
23855 New @sc{gdb/mi} commands should only output @var{lists} containing
23861 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
23862 details about the various output records.
23864 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23865 @node GDB/MI Compatibility with CLI
23866 @section @sc{gdb/mi} Compatibility with CLI
23868 @cindex compatibility, @sc{gdb/mi} and CLI
23869 @cindex @sc{gdb/mi}, compatibility with CLI
23871 For the developers convenience CLI commands can be entered directly,
23872 but there may be some unexpected behaviour. For example, commands
23873 that query the user will behave as if the user replied yes, breakpoint
23874 command lists are not executed and some CLI commands, such as
23875 @code{if}, @code{when} and @code{define}, prompt for further input with
23876 @samp{>}, which is not valid MI output.
23878 This feature may be removed at some stage in the future and it is
23879 recommended that front ends use the @code{-interpreter-exec} command
23880 (@pxref{-interpreter-exec}).
23882 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23883 @node GDB/MI Development and Front Ends
23884 @section @sc{gdb/mi} Development and Front Ends
23885 @cindex @sc{gdb/mi} development
23887 The application which takes the MI output and presents the state of the
23888 program being debugged to the user is called a @dfn{front end}.
23890 Although @sc{gdb/mi} is still incomplete, it is currently being used
23891 by a variety of front ends to @value{GDBN}. This makes it difficult
23892 to introduce new functionality without breaking existing usage. This
23893 section tries to minimize the problems by describing how the protocol
23896 Some changes in MI need not break a carefully designed front end, and
23897 for these the MI version will remain unchanged. The following is a
23898 list of changes that may occur within one level, so front ends should
23899 parse MI output in a way that can handle them:
23903 New MI commands may be added.
23906 New fields may be added to the output of any MI command.
23909 The range of values for fields with specified values, e.g.,
23910 @code{in_scope} (@pxref{-var-update}) may be extended.
23912 @c The format of field's content e.g type prefix, may change so parse it
23913 @c at your own risk. Yes, in general?
23915 @c The order of fields may change? Shouldn't really matter but it might
23916 @c resolve inconsistencies.
23919 If the changes are likely to break front ends, the MI version level
23920 will be increased by one. This will allow the front end to parse the
23921 output according to the MI version. Apart from mi0, new versions of
23922 @value{GDBN} will not support old versions of MI and it will be the
23923 responsibility of the front end to work with the new one.
23925 @c Starting with mi3, add a new command -mi-version that prints the MI
23928 The best way to avoid unexpected changes in MI that might break your front
23929 end is to make your project known to @value{GDBN} developers and
23930 follow development on @email{gdb@@sourceware.org} and
23931 @email{gdb-patches@@sourceware.org}.
23932 @cindex mailing lists
23934 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23935 @node GDB/MI Output Records
23936 @section @sc{gdb/mi} Output Records
23939 * GDB/MI Result Records::
23940 * GDB/MI Stream Records::
23941 * GDB/MI Async Records::
23942 * GDB/MI Frame Information::
23943 * GDB/MI Thread Information::
23946 @node GDB/MI Result Records
23947 @subsection @sc{gdb/mi} Result Records
23949 @cindex result records in @sc{gdb/mi}
23950 @cindex @sc{gdb/mi}, result records
23951 In addition to a number of out-of-band notifications, the response to a
23952 @sc{gdb/mi} command includes one of the following result indications:
23956 @item "^done" [ "," @var{results} ]
23957 The synchronous operation was successful, @code{@var{results}} are the return
23962 This result record is equivalent to @samp{^done}. Historically, it
23963 was output instead of @samp{^done} if the command has resumed the
23964 target. This behaviour is maintained for backward compatibility, but
23965 all frontends should treat @samp{^done} and @samp{^running}
23966 identically and rely on the @samp{*running} output record to determine
23967 which threads are resumed.
23971 @value{GDBN} has connected to a remote target.
23973 @item "^error" "," @var{c-string}
23975 The operation failed. The @code{@var{c-string}} contains the corresponding
23980 @value{GDBN} has terminated.
23984 @node GDB/MI Stream Records
23985 @subsection @sc{gdb/mi} Stream Records
23987 @cindex @sc{gdb/mi}, stream records
23988 @cindex stream records in @sc{gdb/mi}
23989 @value{GDBN} internally maintains a number of output streams: the console, the
23990 target, and the log. The output intended for each of these streams is
23991 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
23993 Each stream record begins with a unique @dfn{prefix character} which
23994 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
23995 Syntax}). In addition to the prefix, each stream record contains a
23996 @code{@var{string-output}}. This is either raw text (with an implicit new
23997 line) or a quoted C string (which does not contain an implicit newline).
24000 @item "~" @var{string-output}
24001 The console output stream contains text that should be displayed in the
24002 CLI console window. It contains the textual responses to CLI commands.
24004 @item "@@" @var{string-output}
24005 The target output stream contains any textual output from the running
24006 target. This is only present when GDB's event loop is truly
24007 asynchronous, which is currently only the case for remote targets.
24009 @item "&" @var{string-output}
24010 The log stream contains debugging messages being produced by @value{GDBN}'s
24014 @node GDB/MI Async Records
24015 @subsection @sc{gdb/mi} Async Records
24017 @cindex async records in @sc{gdb/mi}
24018 @cindex @sc{gdb/mi}, async records
24019 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
24020 additional changes that have occurred. Those changes can either be a
24021 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
24022 target activity (e.g., target stopped).
24024 The following is the list of possible async records:
24028 @item *running,thread-id="@var{thread}"
24029 The target is now running. The @var{thread} field tells which
24030 specific thread is now running, and can be @samp{all} if all threads
24031 are running. The frontend should assume that no interaction with a
24032 running thread is possible after this notification is produced.
24033 The frontend should not assume that this notification is output
24034 only once for any command. @value{GDBN} may emit this notification
24035 several times, either for different threads, because it cannot resume
24036 all threads together, or even for a single thread, if the thread must
24037 be stepped though some code before letting it run freely.
24039 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
24040 The target has stopped. The @var{reason} field can have one of the
24044 @item breakpoint-hit
24045 A breakpoint was reached.
24046 @item watchpoint-trigger
24047 A watchpoint was triggered.
24048 @item read-watchpoint-trigger
24049 A read watchpoint was triggered.
24050 @item access-watchpoint-trigger
24051 An access watchpoint was triggered.
24052 @item function-finished
24053 An -exec-finish or similar CLI command was accomplished.
24054 @item location-reached
24055 An -exec-until or similar CLI command was accomplished.
24056 @item watchpoint-scope
24057 A watchpoint has gone out of scope.
24058 @item end-stepping-range
24059 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
24060 similar CLI command was accomplished.
24061 @item exited-signalled
24062 The inferior exited because of a signal.
24064 The inferior exited.
24065 @item exited-normally
24066 The inferior exited normally.
24067 @item signal-received
24068 A signal was received by the inferior.
24071 The @var{id} field identifies the thread that directly caused the stop
24072 -- for example by hitting a breakpoint. Depending on whether all-stop
24073 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
24074 stop all threads, or only the thread that directly triggered the stop.
24075 If all threads are stopped, the @var{stopped} field will have the
24076 value of @code{"all"}. Otherwise, the value of the @var{stopped}
24077 field will be a list of thread identifiers. Presently, this list will
24078 always include a single thread, but frontend should be prepared to see
24079 several threads in the list. The @var{core} field reports the
24080 processor core on which the stop event has happened. This field may be absent
24081 if such information is not available.
24083 @item =thread-group-added,id="@var{id}"
24084 @itemx =thread-group-removed,id="@var{id}"
24085 A thread group was either added or removed. The @var{id} field
24086 contains the @value{GDBN} identifier of the thread group. When a thread
24087 group is added, it generally might not be associated with a running
24088 process. When a thread group is removed, its id becomes invalid and
24089 cannot be used in any way.
24091 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
24092 A thread group became associated with a running program,
24093 either because the program was just started or the thread group
24094 was attached to a program. The @var{id} field contains the
24095 @value{GDBN} identifier of the thread group. The @var{pid} field
24096 contains process identifier, specific to the operating system.
24098 @itemx =thread-group-exited,id="@var{id}"
24099 A thread group is no longer associated with a running program,
24100 either because the program has exited, or because it was detached
24101 from. The @var{id} field contains the @value{GDBN} identifier of the
24104 @item =thread-created,id="@var{id}",group-id="@var{gid}"
24105 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
24106 A thread either was created, or has exited. The @var{id} field
24107 contains the @value{GDBN} identifier of the thread. The @var{gid}
24108 field identifies the thread group this thread belongs to.
24110 @item =thread-selected,id="@var{id}"
24111 Informs that the selected thread was changed as result of the last
24112 command. This notification is not emitted as result of @code{-thread-select}
24113 command but is emitted whenever an MI command that is not documented
24114 to change the selected thread actually changes it. In particular,
24115 invoking, directly or indirectly (via user-defined command), the CLI
24116 @code{thread} command, will generate this notification.
24118 We suggest that in response to this notification, front ends
24119 highlight the selected thread and cause subsequent commands to apply to
24122 @item =library-loaded,...
24123 Reports that a new library file was loaded by the program. This
24124 notification has 4 fields---@var{id}, @var{target-name},
24125 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
24126 opaque identifier of the library. For remote debugging case,
24127 @var{target-name} and @var{host-name} fields give the name of the
24128 library file on the target, and on the host respectively. For native
24129 debugging, both those fields have the same value. The
24130 @var{symbols-loaded} field reports if the debug symbols for this
24131 library are loaded. The @var{thread-group} field, if present,
24132 specifies the id of the thread group in whose context the library was loaded.
24133 If the field is absent, it means the library was loaded in the context
24134 of all present thread groups.
24136 @item =library-unloaded,...
24137 Reports that a library was unloaded by the program. This notification
24138 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
24139 the same meaning as for the @code{=library-loaded} notification.
24140 The @var{thread-group} field, if present, specifies the id of the
24141 thread group in whose context the library was unloaded. If the field is
24142 absent, it means the library was unloaded in the context of all present
24147 @node GDB/MI Frame Information
24148 @subsection @sc{gdb/mi} Frame Information
24150 Response from many MI commands includes an information about stack
24151 frame. This information is a tuple that may have the following
24156 The level of the stack frame. The innermost frame has the level of
24157 zero. This field is always present.
24160 The name of the function corresponding to the frame. This field may
24161 be absent if @value{GDBN} is unable to determine the function name.
24164 The code address for the frame. This field is always present.
24167 The name of the source files that correspond to the frame's code
24168 address. This field may be absent.
24171 The source line corresponding to the frames' code address. This field
24175 The name of the binary file (either executable or shared library) the
24176 corresponds to the frame's code address. This field may be absent.
24180 @node GDB/MI Thread Information
24181 @subsection @sc{gdb/mi} Thread Information
24183 Whenever @value{GDBN} has to report an information about a thread, it
24184 uses a tuple with the following fields:
24188 The numeric id assigned to the thread by @value{GDBN}. This field is
24192 Target-specific string identifying the thread. This field is always present.
24195 Additional information about the thread provided by the target.
24196 It is supposed to be human-readable and not interpreted by the
24197 frontend. This field is optional.
24200 Either @samp{stopped} or @samp{running}, depending on whether the
24201 thread is presently running. This field is always present.
24204 The value of this field is an integer number of the processor core the
24205 thread was last seen on. This field is optional.
24209 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24210 @node GDB/MI Simple Examples
24211 @section Simple Examples of @sc{gdb/mi} Interaction
24212 @cindex @sc{gdb/mi}, simple examples
24214 This subsection presents several simple examples of interaction using
24215 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
24216 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
24217 the output received from @sc{gdb/mi}.
24219 Note the line breaks shown in the examples are here only for
24220 readability, they don't appear in the real output.
24222 @subheading Setting a Breakpoint
24224 Setting a breakpoint generates synchronous output which contains detailed
24225 information of the breakpoint.
24228 -> -break-insert main
24229 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24230 enabled="y",addr="0x08048564",func="main",file="myprog.c",
24231 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
24235 @subheading Program Execution
24237 Program execution generates asynchronous records and MI gives the
24238 reason that execution stopped.
24244 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24245 frame=@{addr="0x08048564",func="main",
24246 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
24247 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
24252 <- *stopped,reason="exited-normally"
24256 @subheading Quitting @value{GDBN}
24258 Quitting @value{GDBN} just prints the result class @samp{^exit}.
24266 Please note that @samp{^exit} is printed immediately, but it might
24267 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
24268 performs necessary cleanups, including killing programs being debugged
24269 or disconnecting from debug hardware, so the frontend should wait till
24270 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
24271 fails to exit in reasonable time.
24273 @subheading A Bad Command
24275 Here's what happens if you pass a non-existent command:
24279 <- ^error,msg="Undefined MI command: rubbish"
24284 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24285 @node GDB/MI Command Description Format
24286 @section @sc{gdb/mi} Command Description Format
24288 The remaining sections describe blocks of commands. Each block of
24289 commands is laid out in a fashion similar to this section.
24291 @subheading Motivation
24293 The motivation for this collection of commands.
24295 @subheading Introduction
24297 A brief introduction to this collection of commands as a whole.
24299 @subheading Commands
24301 For each command in the block, the following is described:
24303 @subsubheading Synopsis
24306 -command @var{args}@dots{}
24309 @subsubheading Result
24311 @subsubheading @value{GDBN} Command
24313 The corresponding @value{GDBN} CLI command(s), if any.
24315 @subsubheading Example
24317 Example(s) formatted for readability. Some of the described commands have
24318 not been implemented yet and these are labeled N.A.@: (not available).
24321 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24322 @node GDB/MI Breakpoint Commands
24323 @section @sc{gdb/mi} Breakpoint Commands
24325 @cindex breakpoint commands for @sc{gdb/mi}
24326 @cindex @sc{gdb/mi}, breakpoint commands
24327 This section documents @sc{gdb/mi} commands for manipulating
24330 @subheading The @code{-break-after} Command
24331 @findex -break-after
24333 @subsubheading Synopsis
24336 -break-after @var{number} @var{count}
24339 The breakpoint number @var{number} is not in effect until it has been
24340 hit @var{count} times. To see how this is reflected in the output of
24341 the @samp{-break-list} command, see the description of the
24342 @samp{-break-list} command below.
24344 @subsubheading @value{GDBN} Command
24346 The corresponding @value{GDBN} command is @samp{ignore}.
24348 @subsubheading Example
24353 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24354 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24355 fullname="/home/foo/hello.c",line="5",times="0"@}
24362 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24363 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24364 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24365 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24366 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24367 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24368 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24369 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24370 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24371 line="5",times="0",ignore="3"@}]@}
24376 @subheading The @code{-break-catch} Command
24377 @findex -break-catch
24380 @subheading The @code{-break-commands} Command
24381 @findex -break-commands
24383 @subsubheading Synopsis
24386 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
24389 Specifies the CLI commands that should be executed when breakpoint
24390 @var{number} is hit. The parameters @var{command1} to @var{commandN}
24391 are the commands. If no command is specified, any previously-set
24392 commands are cleared. @xref{Break Commands}. Typical use of this
24393 functionality is tracing a program, that is, printing of values of
24394 some variables whenever breakpoint is hit and then continuing.
24396 @subsubheading @value{GDBN} Command
24398 The corresponding @value{GDBN} command is @samp{commands}.
24400 @subsubheading Example
24405 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24406 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24407 fullname="/home/foo/hello.c",line="5",times="0"@}
24409 -break-commands 1 "print v" "continue"
24414 @subheading The @code{-break-condition} Command
24415 @findex -break-condition
24417 @subsubheading Synopsis
24420 -break-condition @var{number} @var{expr}
24423 Breakpoint @var{number} will stop the program only if the condition in
24424 @var{expr} is true. The condition becomes part of the
24425 @samp{-break-list} output (see the description of the @samp{-break-list}
24428 @subsubheading @value{GDBN} Command
24430 The corresponding @value{GDBN} command is @samp{condition}.
24432 @subsubheading Example
24436 -break-condition 1 1
24440 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24441 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24442 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24443 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24444 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24445 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24446 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24447 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24448 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24449 line="5",cond="1",times="0",ignore="3"@}]@}
24453 @subheading The @code{-break-delete} Command
24454 @findex -break-delete
24456 @subsubheading Synopsis
24459 -break-delete ( @var{breakpoint} )+
24462 Delete the breakpoint(s) whose number(s) are specified in the argument
24463 list. This is obviously reflected in the breakpoint list.
24465 @subsubheading @value{GDBN} Command
24467 The corresponding @value{GDBN} command is @samp{delete}.
24469 @subsubheading Example
24477 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24478 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24479 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24480 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24481 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24482 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24483 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24488 @subheading The @code{-break-disable} Command
24489 @findex -break-disable
24491 @subsubheading Synopsis
24494 -break-disable ( @var{breakpoint} )+
24497 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
24498 break list is now set to @samp{n} for the named @var{breakpoint}(s).
24500 @subsubheading @value{GDBN} Command
24502 The corresponding @value{GDBN} command is @samp{disable}.
24504 @subsubheading Example
24512 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24513 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24514 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24515 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24516 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24517 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24518 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24519 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
24520 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24521 line="5",times="0"@}]@}
24525 @subheading The @code{-break-enable} Command
24526 @findex -break-enable
24528 @subsubheading Synopsis
24531 -break-enable ( @var{breakpoint} )+
24534 Enable (previously disabled) @var{breakpoint}(s).
24536 @subsubheading @value{GDBN} Command
24538 The corresponding @value{GDBN} command is @samp{enable}.
24540 @subsubheading Example
24548 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24549 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24550 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24551 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24552 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24553 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24554 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24555 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24556 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24557 line="5",times="0"@}]@}
24561 @subheading The @code{-break-info} Command
24562 @findex -break-info
24564 @subsubheading Synopsis
24567 -break-info @var{breakpoint}
24571 Get information about a single breakpoint.
24573 @subsubheading @value{GDBN} Command
24575 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
24577 @subsubheading Example
24580 @subheading The @code{-break-insert} Command
24581 @findex -break-insert
24583 @subsubheading Synopsis
24586 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
24587 [ -c @var{condition} ] [ -i @var{ignore-count} ]
24588 [ -p @var{thread} ] [ @var{location} ]
24592 If specified, @var{location}, can be one of:
24599 @item filename:linenum
24600 @item filename:function
24604 The possible optional parameters of this command are:
24608 Insert a temporary breakpoint.
24610 Insert a hardware breakpoint.
24611 @item -c @var{condition}
24612 Make the breakpoint conditional on @var{condition}.
24613 @item -i @var{ignore-count}
24614 Initialize the @var{ignore-count}.
24616 If @var{location} cannot be parsed (for example if it
24617 refers to unknown files or functions), create a pending
24618 breakpoint. Without this flag, @value{GDBN} will report
24619 an error, and won't create a breakpoint, if @var{location}
24622 Create a disabled breakpoint.
24624 Create a tracepoint. @xref{Tracepoints}. When this parameter
24625 is used together with @samp{-h}, a fast tracepoint is created.
24628 @subsubheading Result
24630 The result is in the form:
24633 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
24634 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
24635 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
24636 times="@var{times}"@}
24640 where @var{number} is the @value{GDBN} number for this breakpoint,
24641 @var{funcname} is the name of the function where the breakpoint was
24642 inserted, @var{filename} is the name of the source file which contains
24643 this function, @var{lineno} is the source line number within that file
24644 and @var{times} the number of times that the breakpoint has been hit
24645 (always 0 for -break-insert but may be greater for -break-info or -break-list
24646 which use the same output).
24648 Note: this format is open to change.
24649 @c An out-of-band breakpoint instead of part of the result?
24651 @subsubheading @value{GDBN} Command
24653 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
24654 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
24656 @subsubheading Example
24661 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
24662 fullname="/home/foo/recursive2.c,line="4",times="0"@}
24664 -break-insert -t foo
24665 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
24666 fullname="/home/foo/recursive2.c,line="11",times="0"@}
24669 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24670 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24671 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24672 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24673 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24674 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24675 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24676 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24677 addr="0x0001072c", func="main",file="recursive2.c",
24678 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
24679 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
24680 addr="0x00010774",func="foo",file="recursive2.c",
24681 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
24683 -break-insert -r foo.*
24684 ~int foo(int, int);
24685 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
24686 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
24690 @subheading The @code{-break-list} Command
24691 @findex -break-list
24693 @subsubheading Synopsis
24699 Displays the list of inserted breakpoints, showing the following fields:
24703 number of the breakpoint
24705 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
24707 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
24710 is the breakpoint enabled or no: @samp{y} or @samp{n}
24712 memory location at which the breakpoint is set
24714 logical location of the breakpoint, expressed by function name, file
24717 number of times the breakpoint has been hit
24720 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
24721 @code{body} field is an empty list.
24723 @subsubheading @value{GDBN} Command
24725 The corresponding @value{GDBN} command is @samp{info break}.
24727 @subsubheading Example
24732 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24733 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24734 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24735 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24736 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24737 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24738 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24739 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24740 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
24741 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24742 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
24743 line="13",times="0"@}]@}
24747 Here's an example of the result when there are no breakpoints:
24752 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24753 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24754 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24755 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24756 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24757 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24758 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24763 @subheading The @code{-break-passcount} Command
24764 @findex -break-passcount
24766 @subsubheading Synopsis
24769 -break-passcount @var{tracepoint-number} @var{passcount}
24772 Set the passcount for tracepoint @var{tracepoint-number} to
24773 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
24774 is not a tracepoint, error is emitted. This corresponds to CLI
24775 command @samp{passcount}.
24777 @subheading The @code{-break-watch} Command
24778 @findex -break-watch
24780 @subsubheading Synopsis
24783 -break-watch [ -a | -r ]
24786 Create a watchpoint. With the @samp{-a} option it will create an
24787 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
24788 read from or on a write to the memory location. With the @samp{-r}
24789 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
24790 trigger only when the memory location is accessed for reading. Without
24791 either of the options, the watchpoint created is a regular watchpoint,
24792 i.e., it will trigger when the memory location is accessed for writing.
24793 @xref{Set Watchpoints, , Setting Watchpoints}.
24795 Note that @samp{-break-list} will report a single list of watchpoints and
24796 breakpoints inserted.
24798 @subsubheading @value{GDBN} Command
24800 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
24803 @subsubheading Example
24805 Setting a watchpoint on a variable in the @code{main} function:
24810 ^done,wpt=@{number="2",exp="x"@}
24815 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
24816 value=@{old="-268439212",new="55"@},
24817 frame=@{func="main",args=[],file="recursive2.c",
24818 fullname="/home/foo/bar/recursive2.c",line="5"@}
24822 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
24823 the program execution twice: first for the variable changing value, then
24824 for the watchpoint going out of scope.
24829 ^done,wpt=@{number="5",exp="C"@}
24834 *stopped,reason="watchpoint-trigger",
24835 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
24836 frame=@{func="callee4",args=[],
24837 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24838 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24843 *stopped,reason="watchpoint-scope",wpnum="5",
24844 frame=@{func="callee3",args=[@{name="strarg",
24845 value="0x11940 \"A string argument.\""@}],
24846 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24847 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24851 Listing breakpoints and watchpoints, at different points in the program
24852 execution. Note that once the watchpoint goes out of scope, it is
24858 ^done,wpt=@{number="2",exp="C"@}
24861 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24862 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24863 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24864 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24865 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24866 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24867 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24868 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24869 addr="0x00010734",func="callee4",
24870 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24871 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
24872 bkpt=@{number="2",type="watchpoint",disp="keep",
24873 enabled="y",addr="",what="C",times="0"@}]@}
24878 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
24879 value=@{old="-276895068",new="3"@},
24880 frame=@{func="callee4",args=[],
24881 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24882 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24885 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24886 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24887 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24888 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24889 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24890 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24891 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24892 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24893 addr="0x00010734",func="callee4",
24894 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24895 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
24896 bkpt=@{number="2",type="watchpoint",disp="keep",
24897 enabled="y",addr="",what="C",times="-5"@}]@}
24901 ^done,reason="watchpoint-scope",wpnum="2",
24902 frame=@{func="callee3",args=[@{name="strarg",
24903 value="0x11940 \"A string argument.\""@}],
24904 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24905 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24908 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24909 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24910 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24911 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24912 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24913 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24914 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24915 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24916 addr="0x00010734",func="callee4",
24917 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24918 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
24923 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24924 @node GDB/MI Program Context
24925 @section @sc{gdb/mi} Program Context
24927 @subheading The @code{-exec-arguments} Command
24928 @findex -exec-arguments
24931 @subsubheading Synopsis
24934 -exec-arguments @var{args}
24937 Set the inferior program arguments, to be used in the next
24940 @subsubheading @value{GDBN} Command
24942 The corresponding @value{GDBN} command is @samp{set args}.
24944 @subsubheading Example
24948 -exec-arguments -v word
24955 @subheading The @code{-exec-show-arguments} Command
24956 @findex -exec-show-arguments
24958 @subsubheading Synopsis
24961 -exec-show-arguments
24964 Print the arguments of the program.
24966 @subsubheading @value{GDBN} Command
24968 The corresponding @value{GDBN} command is @samp{show args}.
24970 @subsubheading Example
24975 @subheading The @code{-environment-cd} Command
24976 @findex -environment-cd
24978 @subsubheading Synopsis
24981 -environment-cd @var{pathdir}
24984 Set @value{GDBN}'s working directory.
24986 @subsubheading @value{GDBN} Command
24988 The corresponding @value{GDBN} command is @samp{cd}.
24990 @subsubheading Example
24994 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
25000 @subheading The @code{-environment-directory} Command
25001 @findex -environment-directory
25003 @subsubheading Synopsis
25006 -environment-directory [ -r ] [ @var{pathdir} ]+
25009 Add directories @var{pathdir} to beginning of search path for source files.
25010 If the @samp{-r} option is used, the search path is reset to the default
25011 search path. If directories @var{pathdir} are supplied in addition to the
25012 @samp{-r} option, the search path is first reset and then addition
25014 Multiple directories may be specified, separated by blanks. Specifying
25015 multiple directories in a single command
25016 results in the directories added to the beginning of the
25017 search path in the same order they were presented in the command.
25018 If blanks are needed as
25019 part of a directory name, double-quotes should be used around
25020 the name. In the command output, the path will show up separated
25021 by the system directory-separator character. The directory-separator
25022 character must not be used
25023 in any directory name.
25024 If no directories are specified, the current search path is displayed.
25026 @subsubheading @value{GDBN} Command
25028 The corresponding @value{GDBN} command is @samp{dir}.
25030 @subsubheading Example
25034 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
25035 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25037 -environment-directory ""
25038 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25040 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
25041 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
25043 -environment-directory -r
25044 ^done,source-path="$cdir:$cwd"
25049 @subheading The @code{-environment-path} Command
25050 @findex -environment-path
25052 @subsubheading Synopsis
25055 -environment-path [ -r ] [ @var{pathdir} ]+
25058 Add directories @var{pathdir} to beginning of search path for object files.
25059 If the @samp{-r} option is used, the search path is reset to the original
25060 search path that existed at gdb start-up. If directories @var{pathdir} are
25061 supplied in addition to the
25062 @samp{-r} option, the search path is first reset and then addition
25064 Multiple directories may be specified, separated by blanks. Specifying
25065 multiple directories in a single command
25066 results in the directories added to the beginning of the
25067 search path in the same order they were presented in the command.
25068 If blanks are needed as
25069 part of a directory name, double-quotes should be used around
25070 the name. In the command output, the path will show up separated
25071 by the system directory-separator character. The directory-separator
25072 character must not be used
25073 in any directory name.
25074 If no directories are specified, the current path is displayed.
25077 @subsubheading @value{GDBN} Command
25079 The corresponding @value{GDBN} command is @samp{path}.
25081 @subsubheading Example
25086 ^done,path="/usr/bin"
25088 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
25089 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
25091 -environment-path -r /usr/local/bin
25092 ^done,path="/usr/local/bin:/usr/bin"
25097 @subheading The @code{-environment-pwd} Command
25098 @findex -environment-pwd
25100 @subsubheading Synopsis
25106 Show the current working directory.
25108 @subsubheading @value{GDBN} Command
25110 The corresponding @value{GDBN} command is @samp{pwd}.
25112 @subsubheading Example
25117 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
25121 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25122 @node GDB/MI Thread Commands
25123 @section @sc{gdb/mi} Thread Commands
25126 @subheading The @code{-thread-info} Command
25127 @findex -thread-info
25129 @subsubheading Synopsis
25132 -thread-info [ @var{thread-id} ]
25135 Reports information about either a specific thread, if
25136 the @var{thread-id} parameter is present, or about all
25137 threads. When printing information about all threads,
25138 also reports the current thread.
25140 @subsubheading @value{GDBN} Command
25142 The @samp{info thread} command prints the same information
25145 @subsubheading Example
25150 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
25151 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
25152 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
25153 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
25154 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
25155 current-thread-id="1"
25159 The @samp{state} field may have the following values:
25163 The thread is stopped. Frame information is available for stopped
25167 The thread is running. There's no frame information for running
25172 @subheading The @code{-thread-list-ids} Command
25173 @findex -thread-list-ids
25175 @subsubheading Synopsis
25181 Produces a list of the currently known @value{GDBN} thread ids. At the
25182 end of the list it also prints the total number of such threads.
25184 This command is retained for historical reasons, the
25185 @code{-thread-info} command should be used instead.
25187 @subsubheading @value{GDBN} Command
25189 Part of @samp{info threads} supplies the same information.
25191 @subsubheading Example
25196 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25197 current-thread-id="1",number-of-threads="3"
25202 @subheading The @code{-thread-select} Command
25203 @findex -thread-select
25205 @subsubheading Synopsis
25208 -thread-select @var{threadnum}
25211 Make @var{threadnum} the current thread. It prints the number of the new
25212 current thread, and the topmost frame for that thread.
25214 This command is deprecated in favor of explicitly using the
25215 @samp{--thread} option to each command.
25217 @subsubheading @value{GDBN} Command
25219 The corresponding @value{GDBN} command is @samp{thread}.
25221 @subsubheading Example
25228 *stopped,reason="end-stepping-range",thread-id="2",line="187",
25229 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
25233 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25234 number-of-threads="3"
25237 ^done,new-thread-id="3",
25238 frame=@{level="0",func="vprintf",
25239 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
25240 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
25244 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25245 @node GDB/MI Program Execution
25246 @section @sc{gdb/mi} Program Execution
25248 These are the asynchronous commands which generate the out-of-band
25249 record @samp{*stopped}. Currently @value{GDBN} only really executes
25250 asynchronously with remote targets and this interaction is mimicked in
25253 @subheading The @code{-exec-continue} Command
25254 @findex -exec-continue
25256 @subsubheading Synopsis
25259 -exec-continue [--reverse] [--all|--thread-group N]
25262 Resumes the execution of the inferior program, which will continue
25263 to execute until it reaches a debugger stop event. If the
25264 @samp{--reverse} option is specified, execution resumes in reverse until
25265 it reaches a stop event. Stop events may include
25268 breakpoints or watchpoints
25270 signals or exceptions
25272 the end of the process (or its beginning under @samp{--reverse})
25274 the end or beginning of a replay log if one is being used.
25276 In all-stop mode (@pxref{All-Stop
25277 Mode}), may resume only one thread, or all threads, depending on the
25278 value of the @samp{scheduler-locking} variable. If @samp{--all} is
25279 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
25280 ignored in all-stop mode. If the @samp{--thread-group} options is
25281 specified, then all threads in that thread group are resumed.
25283 @subsubheading @value{GDBN} Command
25285 The corresponding @value{GDBN} corresponding is @samp{continue}.
25287 @subsubheading Example
25294 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
25295 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
25301 @subheading The @code{-exec-finish} Command
25302 @findex -exec-finish
25304 @subsubheading Synopsis
25307 -exec-finish [--reverse]
25310 Resumes the execution of the inferior program until the current
25311 function is exited. Displays the results returned by the function.
25312 If the @samp{--reverse} option is specified, resumes the reverse
25313 execution of the inferior program until the point where current
25314 function was called.
25316 @subsubheading @value{GDBN} Command
25318 The corresponding @value{GDBN} command is @samp{finish}.
25320 @subsubheading Example
25322 Function returning @code{void}.
25329 *stopped,reason="function-finished",frame=@{func="main",args=[],
25330 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
25334 Function returning other than @code{void}. The name of the internal
25335 @value{GDBN} variable storing the result is printed, together with the
25342 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
25343 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
25344 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25345 gdb-result-var="$1",return-value="0"
25350 @subheading The @code{-exec-interrupt} Command
25351 @findex -exec-interrupt
25353 @subsubheading Synopsis
25356 -exec-interrupt [--all|--thread-group N]
25359 Interrupts the background execution of the target. Note how the token
25360 associated with the stop message is the one for the execution command
25361 that has been interrupted. The token for the interrupt itself only
25362 appears in the @samp{^done} output. If the user is trying to
25363 interrupt a non-running program, an error message will be printed.
25365 Note that when asynchronous execution is enabled, this command is
25366 asynchronous just like other execution commands. That is, first the
25367 @samp{^done} response will be printed, and the target stop will be
25368 reported after that using the @samp{*stopped} notification.
25370 In non-stop mode, only the context thread is interrupted by default.
25371 All threads (in all inferiors) will be interrupted if the
25372 @samp{--all} option is specified. If the @samp{--thread-group}
25373 option is specified, all threads in that group will be interrupted.
25375 @subsubheading @value{GDBN} Command
25377 The corresponding @value{GDBN} command is @samp{interrupt}.
25379 @subsubheading Example
25390 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
25391 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
25392 fullname="/home/foo/bar/try.c",line="13"@}
25397 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
25401 @subheading The @code{-exec-jump} Command
25404 @subsubheading Synopsis
25407 -exec-jump @var{location}
25410 Resumes execution of the inferior program at the location specified by
25411 parameter. @xref{Specify Location}, for a description of the
25412 different forms of @var{location}.
25414 @subsubheading @value{GDBN} Command
25416 The corresponding @value{GDBN} command is @samp{jump}.
25418 @subsubheading Example
25421 -exec-jump foo.c:10
25422 *running,thread-id="all"
25427 @subheading The @code{-exec-next} Command
25430 @subsubheading Synopsis
25433 -exec-next [--reverse]
25436 Resumes execution of the inferior program, stopping when the beginning
25437 of the next source line is reached.
25439 If the @samp{--reverse} option is specified, resumes reverse execution
25440 of the inferior program, stopping at the beginning of the previous
25441 source line. If you issue this command on the first line of a
25442 function, it will take you back to the caller of that function, to the
25443 source line where the function was called.
25446 @subsubheading @value{GDBN} Command
25448 The corresponding @value{GDBN} command is @samp{next}.
25450 @subsubheading Example
25456 *stopped,reason="end-stepping-range",line="8",file="hello.c"
25461 @subheading The @code{-exec-next-instruction} Command
25462 @findex -exec-next-instruction
25464 @subsubheading Synopsis
25467 -exec-next-instruction [--reverse]
25470 Executes one machine instruction. If the instruction is a function
25471 call, continues until the function returns. If the program stops at an
25472 instruction in the middle of a source line, the address will be
25475 If the @samp{--reverse} option is specified, resumes reverse execution
25476 of the inferior program, stopping at the previous instruction. If the
25477 previously executed instruction was a return from another function,
25478 it will continue to execute in reverse until the call to that function
25479 (from the current stack frame) is reached.
25481 @subsubheading @value{GDBN} Command
25483 The corresponding @value{GDBN} command is @samp{nexti}.
25485 @subsubheading Example
25489 -exec-next-instruction
25493 *stopped,reason="end-stepping-range",
25494 addr="0x000100d4",line="5",file="hello.c"
25499 @subheading The @code{-exec-return} Command
25500 @findex -exec-return
25502 @subsubheading Synopsis
25508 Makes current function return immediately. Doesn't execute the inferior.
25509 Displays the new current frame.
25511 @subsubheading @value{GDBN} Command
25513 The corresponding @value{GDBN} command is @samp{return}.
25515 @subsubheading Example
25519 200-break-insert callee4
25520 200^done,bkpt=@{number="1",addr="0x00010734",
25521 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25526 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25527 frame=@{func="callee4",args=[],
25528 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25529 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25535 111^done,frame=@{level="0",func="callee3",
25536 args=[@{name="strarg",
25537 value="0x11940 \"A string argument.\""@}],
25538 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25539 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25544 @subheading The @code{-exec-run} Command
25547 @subsubheading Synopsis
25550 -exec-run [--all | --thread-group N]
25553 Starts execution of the inferior from the beginning. The inferior
25554 executes until either a breakpoint is encountered or the program
25555 exits. In the latter case the output will include an exit code, if
25556 the program has exited exceptionally.
25558 When no option is specified, the current inferior is started. If the
25559 @samp{--thread-group} option is specified, it should refer to a thread
25560 group of type @samp{process}, and that thread group will be started.
25561 If the @samp{--all} option is specified, then all inferiors will be started.
25563 @subsubheading @value{GDBN} Command
25565 The corresponding @value{GDBN} command is @samp{run}.
25567 @subsubheading Examples
25572 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
25577 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25578 frame=@{func="main",args=[],file="recursive2.c",
25579 fullname="/home/foo/bar/recursive2.c",line="4"@}
25584 Program exited normally:
25592 *stopped,reason="exited-normally"
25597 Program exited exceptionally:
25605 *stopped,reason="exited",exit-code="01"
25609 Another way the program can terminate is if it receives a signal such as
25610 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
25614 *stopped,reason="exited-signalled",signal-name="SIGINT",
25615 signal-meaning="Interrupt"
25619 @c @subheading -exec-signal
25622 @subheading The @code{-exec-step} Command
25625 @subsubheading Synopsis
25628 -exec-step [--reverse]
25631 Resumes execution of the inferior program, stopping when the beginning
25632 of the next source line is reached, if the next source line is not a
25633 function call. If it is, stop at the first instruction of the called
25634 function. If the @samp{--reverse} option is specified, resumes reverse
25635 execution of the inferior program, stopping at the beginning of the
25636 previously executed source line.
25638 @subsubheading @value{GDBN} Command
25640 The corresponding @value{GDBN} command is @samp{step}.
25642 @subsubheading Example
25644 Stepping into a function:
25650 *stopped,reason="end-stepping-range",
25651 frame=@{func="foo",args=[@{name="a",value="10"@},
25652 @{name="b",value="0"@}],file="recursive2.c",
25653 fullname="/home/foo/bar/recursive2.c",line="11"@}
25663 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
25668 @subheading The @code{-exec-step-instruction} Command
25669 @findex -exec-step-instruction
25671 @subsubheading Synopsis
25674 -exec-step-instruction [--reverse]
25677 Resumes the inferior which executes one machine instruction. If the
25678 @samp{--reverse} option is specified, resumes reverse execution of the
25679 inferior program, stopping at the previously executed instruction.
25680 The output, once @value{GDBN} has stopped, will vary depending on
25681 whether we have stopped in the middle of a source line or not. In the
25682 former case, the address at which the program stopped will be printed
25685 @subsubheading @value{GDBN} Command
25687 The corresponding @value{GDBN} command is @samp{stepi}.
25689 @subsubheading Example
25693 -exec-step-instruction
25697 *stopped,reason="end-stepping-range",
25698 frame=@{func="foo",args=[],file="try.c",
25699 fullname="/home/foo/bar/try.c",line="10"@}
25701 -exec-step-instruction
25705 *stopped,reason="end-stepping-range",
25706 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
25707 fullname="/home/foo/bar/try.c",line="10"@}
25712 @subheading The @code{-exec-until} Command
25713 @findex -exec-until
25715 @subsubheading Synopsis
25718 -exec-until [ @var{location} ]
25721 Executes the inferior until the @var{location} specified in the
25722 argument is reached. If there is no argument, the inferior executes
25723 until a source line greater than the current one is reached. The
25724 reason for stopping in this case will be @samp{location-reached}.
25726 @subsubheading @value{GDBN} Command
25728 The corresponding @value{GDBN} command is @samp{until}.
25730 @subsubheading Example
25734 -exec-until recursive2.c:6
25738 *stopped,reason="location-reached",frame=@{func="main",args=[],
25739 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
25744 @subheading -file-clear
25745 Is this going away????
25748 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25749 @node GDB/MI Stack Manipulation
25750 @section @sc{gdb/mi} Stack Manipulation Commands
25753 @subheading The @code{-stack-info-frame} Command
25754 @findex -stack-info-frame
25756 @subsubheading Synopsis
25762 Get info on the selected frame.
25764 @subsubheading @value{GDBN} Command
25766 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
25767 (without arguments).
25769 @subsubheading Example
25774 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
25775 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25776 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
25780 @subheading The @code{-stack-info-depth} Command
25781 @findex -stack-info-depth
25783 @subsubheading Synopsis
25786 -stack-info-depth [ @var{max-depth} ]
25789 Return the depth of the stack. If the integer argument @var{max-depth}
25790 is specified, do not count beyond @var{max-depth} frames.
25792 @subsubheading @value{GDBN} Command
25794 There's no equivalent @value{GDBN} command.
25796 @subsubheading Example
25798 For a stack with frame levels 0 through 11:
25805 -stack-info-depth 4
25808 -stack-info-depth 12
25811 -stack-info-depth 11
25814 -stack-info-depth 13
25819 @subheading The @code{-stack-list-arguments} Command
25820 @findex -stack-list-arguments
25822 @subsubheading Synopsis
25825 -stack-list-arguments @var{print-values}
25826 [ @var{low-frame} @var{high-frame} ]
25829 Display a list of the arguments for the frames between @var{low-frame}
25830 and @var{high-frame} (inclusive). If @var{low-frame} and
25831 @var{high-frame} are not provided, list the arguments for the whole
25832 call stack. If the two arguments are equal, show the single frame
25833 at the corresponding level. It is an error if @var{low-frame} is
25834 larger than the actual number of frames. On the other hand,
25835 @var{high-frame} may be larger than the actual number of frames, in
25836 which case only existing frames will be returned.
25838 If @var{print-values} is 0 or @code{--no-values}, print only the names of
25839 the variables; if it is 1 or @code{--all-values}, print also their
25840 values; and if it is 2 or @code{--simple-values}, print the name,
25841 type and value for simple data types, and the name and type for arrays,
25842 structures and unions.
25844 Use of this command to obtain arguments in a single frame is
25845 deprecated in favor of the @samp{-stack-list-variables} command.
25847 @subsubheading @value{GDBN} Command
25849 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
25850 @samp{gdb_get_args} command which partially overlaps with the
25851 functionality of @samp{-stack-list-arguments}.
25853 @subsubheading Example
25860 frame=@{level="0",addr="0x00010734",func="callee4",
25861 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25862 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
25863 frame=@{level="1",addr="0x0001076c",func="callee3",
25864 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25865 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
25866 frame=@{level="2",addr="0x0001078c",func="callee2",
25867 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25868 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
25869 frame=@{level="3",addr="0x000107b4",func="callee1",
25870 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25871 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
25872 frame=@{level="4",addr="0x000107e0",func="main",
25873 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25874 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
25876 -stack-list-arguments 0
25879 frame=@{level="0",args=[]@},
25880 frame=@{level="1",args=[name="strarg"]@},
25881 frame=@{level="2",args=[name="intarg",name="strarg"]@},
25882 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
25883 frame=@{level="4",args=[]@}]
25885 -stack-list-arguments 1
25888 frame=@{level="0",args=[]@},
25890 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25891 frame=@{level="2",args=[
25892 @{name="intarg",value="2"@},
25893 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25894 @{frame=@{level="3",args=[
25895 @{name="intarg",value="2"@},
25896 @{name="strarg",value="0x11940 \"A string argument.\""@},
25897 @{name="fltarg",value="3.5"@}]@},
25898 frame=@{level="4",args=[]@}]
25900 -stack-list-arguments 0 2 2
25901 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
25903 -stack-list-arguments 1 2 2
25904 ^done,stack-args=[frame=@{level="2",
25905 args=[@{name="intarg",value="2"@},
25906 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
25910 @c @subheading -stack-list-exception-handlers
25913 @subheading The @code{-stack-list-frames} Command
25914 @findex -stack-list-frames
25916 @subsubheading Synopsis
25919 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
25922 List the frames currently on the stack. For each frame it displays the
25927 The frame number, 0 being the topmost frame, i.e., the innermost function.
25929 The @code{$pc} value for that frame.
25933 File name of the source file where the function lives.
25935 Line number corresponding to the @code{$pc}.
25938 If invoked without arguments, this command prints a backtrace for the
25939 whole stack. If given two integer arguments, it shows the frames whose
25940 levels are between the two arguments (inclusive). If the two arguments
25941 are equal, it shows the single frame at the corresponding level. It is
25942 an error if @var{low-frame} is larger than the actual number of
25943 frames. On the other hand, @var{high-frame} may be larger than the
25944 actual number of frames, in which case only existing frames will be returned.
25946 @subsubheading @value{GDBN} Command
25948 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
25950 @subsubheading Example
25952 Full stack backtrace:
25958 [frame=@{level="0",addr="0x0001076c",func="foo",
25959 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
25960 frame=@{level="1",addr="0x000107a4",func="foo",
25961 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25962 frame=@{level="2",addr="0x000107a4",func="foo",
25963 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25964 frame=@{level="3",addr="0x000107a4",func="foo",
25965 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25966 frame=@{level="4",addr="0x000107a4",func="foo",
25967 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25968 frame=@{level="5",addr="0x000107a4",func="foo",
25969 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25970 frame=@{level="6",addr="0x000107a4",func="foo",
25971 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25972 frame=@{level="7",addr="0x000107a4",func="foo",
25973 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25974 frame=@{level="8",addr="0x000107a4",func="foo",
25975 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25976 frame=@{level="9",addr="0x000107a4",func="foo",
25977 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25978 frame=@{level="10",addr="0x000107a4",func="foo",
25979 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25980 frame=@{level="11",addr="0x00010738",func="main",
25981 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
25985 Show frames between @var{low_frame} and @var{high_frame}:
25989 -stack-list-frames 3 5
25991 [frame=@{level="3",addr="0x000107a4",func="foo",
25992 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25993 frame=@{level="4",addr="0x000107a4",func="foo",
25994 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25995 frame=@{level="5",addr="0x000107a4",func="foo",
25996 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
26000 Show a single frame:
26004 -stack-list-frames 3 3
26006 [frame=@{level="3",addr="0x000107a4",func="foo",
26007 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
26012 @subheading The @code{-stack-list-locals} Command
26013 @findex -stack-list-locals
26015 @subsubheading Synopsis
26018 -stack-list-locals @var{print-values}
26021 Display the local variable names for the selected frame. If
26022 @var{print-values} is 0 or @code{--no-values}, print only the names of
26023 the variables; if it is 1 or @code{--all-values}, print also their
26024 values; and if it is 2 or @code{--simple-values}, print the name,
26025 type and value for simple data types, and the name and type for arrays,
26026 structures and unions. In this last case, a frontend can immediately
26027 display the value of simple data types and create variable objects for
26028 other data types when the user wishes to explore their values in
26031 This command is deprecated in favor of the
26032 @samp{-stack-list-variables} command.
26034 @subsubheading @value{GDBN} Command
26036 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
26038 @subsubheading Example
26042 -stack-list-locals 0
26043 ^done,locals=[name="A",name="B",name="C"]
26045 -stack-list-locals --all-values
26046 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
26047 @{name="C",value="@{1, 2, 3@}"@}]
26048 -stack-list-locals --simple-values
26049 ^done,locals=[@{name="A",type="int",value="1"@},
26050 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
26054 @subheading The @code{-stack-list-variables} Command
26055 @findex -stack-list-variables
26057 @subsubheading Synopsis
26060 -stack-list-variables @var{print-values}
26063 Display the names of local variables and function arguments for the selected frame. If
26064 @var{print-values} is 0 or @code{--no-values}, print only the names of
26065 the variables; if it is 1 or @code{--all-values}, print also their
26066 values; and if it is 2 or @code{--simple-values}, print the name,
26067 type and value for simple data types, and the name and type for arrays,
26068 structures and unions.
26070 @subsubheading Example
26074 -stack-list-variables --thread 1 --frame 0 --all-values
26075 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
26080 @subheading The @code{-stack-select-frame} Command
26081 @findex -stack-select-frame
26083 @subsubheading Synopsis
26086 -stack-select-frame @var{framenum}
26089 Change the selected frame. Select a different frame @var{framenum} on
26092 This command in deprecated in favor of passing the @samp{--frame}
26093 option to every command.
26095 @subsubheading @value{GDBN} Command
26097 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
26098 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
26100 @subsubheading Example
26104 -stack-select-frame 2
26109 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26110 @node GDB/MI Variable Objects
26111 @section @sc{gdb/mi} Variable Objects
26115 @subheading Motivation for Variable Objects in @sc{gdb/mi}
26117 For the implementation of a variable debugger window (locals, watched
26118 expressions, etc.), we are proposing the adaptation of the existing code
26119 used by @code{Insight}.
26121 The two main reasons for that are:
26125 It has been proven in practice (it is already on its second generation).
26128 It will shorten development time (needless to say how important it is
26132 The original interface was designed to be used by Tcl code, so it was
26133 slightly changed so it could be used through @sc{gdb/mi}. This section
26134 describes the @sc{gdb/mi} operations that will be available and gives some
26135 hints about their use.
26137 @emph{Note}: In addition to the set of operations described here, we
26138 expect the @sc{gui} implementation of a variable window to require, at
26139 least, the following operations:
26142 @item @code{-gdb-show} @code{output-radix}
26143 @item @code{-stack-list-arguments}
26144 @item @code{-stack-list-locals}
26145 @item @code{-stack-select-frame}
26150 @subheading Introduction to Variable Objects
26152 @cindex variable objects in @sc{gdb/mi}
26154 Variable objects are "object-oriented" MI interface for examining and
26155 changing values of expressions. Unlike some other MI interfaces that
26156 work with expressions, variable objects are specifically designed for
26157 simple and efficient presentation in the frontend. A variable object
26158 is identified by string name. When a variable object is created, the
26159 frontend specifies the expression for that variable object. The
26160 expression can be a simple variable, or it can be an arbitrary complex
26161 expression, and can even involve CPU registers. After creating a
26162 variable object, the frontend can invoke other variable object
26163 operations---for example to obtain or change the value of a variable
26164 object, or to change display format.
26166 Variable objects have hierarchical tree structure. Any variable object
26167 that corresponds to a composite type, such as structure in C, has
26168 a number of child variable objects, for example corresponding to each
26169 element of a structure. A child variable object can itself have
26170 children, recursively. Recursion ends when we reach
26171 leaf variable objects, which always have built-in types. Child variable
26172 objects are created only by explicit request, so if a frontend
26173 is not interested in the children of a particular variable object, no
26174 child will be created.
26176 For a leaf variable object it is possible to obtain its value as a
26177 string, or set the value from a string. String value can be also
26178 obtained for a non-leaf variable object, but it's generally a string
26179 that only indicates the type of the object, and does not list its
26180 contents. Assignment to a non-leaf variable object is not allowed.
26182 A frontend does not need to read the values of all variable objects each time
26183 the program stops. Instead, MI provides an update command that lists all
26184 variable objects whose values has changed since the last update
26185 operation. This considerably reduces the amount of data that must
26186 be transferred to the frontend. As noted above, children variable
26187 objects are created on demand, and only leaf variable objects have a
26188 real value. As result, gdb will read target memory only for leaf
26189 variables that frontend has created.
26191 The automatic update is not always desirable. For example, a frontend
26192 might want to keep a value of some expression for future reference,
26193 and never update it. For another example, fetching memory is
26194 relatively slow for embedded targets, so a frontend might want
26195 to disable automatic update for the variables that are either not
26196 visible on the screen, or ``closed''. This is possible using so
26197 called ``frozen variable objects''. Such variable objects are never
26198 implicitly updated.
26200 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
26201 fixed variable object, the expression is parsed when the variable
26202 object is created, including associating identifiers to specific
26203 variables. The meaning of expression never changes. For a floating
26204 variable object the values of variables whose names appear in the
26205 expressions are re-evaluated every time in the context of the current
26206 frame. Consider this example:
26211 struct work_state state;
26218 If a fixed variable object for the @code{state} variable is created in
26219 this function, and we enter the recursive call, the the variable
26220 object will report the value of @code{state} in the top-level
26221 @code{do_work} invocation. On the other hand, a floating variable
26222 object will report the value of @code{state} in the current frame.
26224 If an expression specified when creating a fixed variable object
26225 refers to a local variable, the variable object becomes bound to the
26226 thread and frame in which the variable object is created. When such
26227 variable object is updated, @value{GDBN} makes sure that the
26228 thread/frame combination the variable object is bound to still exists,
26229 and re-evaluates the variable object in context of that thread/frame.
26231 The following is the complete set of @sc{gdb/mi} operations defined to
26232 access this functionality:
26234 @multitable @columnfractions .4 .6
26235 @item @strong{Operation}
26236 @tab @strong{Description}
26238 @item @code{-enable-pretty-printing}
26239 @tab enable Python-based pretty-printing
26240 @item @code{-var-create}
26241 @tab create a variable object
26242 @item @code{-var-delete}
26243 @tab delete the variable object and/or its children
26244 @item @code{-var-set-format}
26245 @tab set the display format of this variable
26246 @item @code{-var-show-format}
26247 @tab show the display format of this variable
26248 @item @code{-var-info-num-children}
26249 @tab tells how many children this object has
26250 @item @code{-var-list-children}
26251 @tab return a list of the object's children
26252 @item @code{-var-info-type}
26253 @tab show the type of this variable object
26254 @item @code{-var-info-expression}
26255 @tab print parent-relative expression that this variable object represents
26256 @item @code{-var-info-path-expression}
26257 @tab print full expression that this variable object represents
26258 @item @code{-var-show-attributes}
26259 @tab is this variable editable? does it exist here?
26260 @item @code{-var-evaluate-expression}
26261 @tab get the value of this variable
26262 @item @code{-var-assign}
26263 @tab set the value of this variable
26264 @item @code{-var-update}
26265 @tab update the variable and its children
26266 @item @code{-var-set-frozen}
26267 @tab set frozeness attribute
26268 @item @code{-var-set-update-range}
26269 @tab set range of children to display on update
26272 In the next subsection we describe each operation in detail and suggest
26273 how it can be used.
26275 @subheading Description And Use of Operations on Variable Objects
26277 @subheading The @code{-enable-pretty-printing} Command
26278 @findex -enable-pretty-printing
26281 -enable-pretty-printing
26284 @value{GDBN} allows Python-based visualizers to affect the output of the
26285 MI variable object commands. However, because there was no way to
26286 implement this in a fully backward-compatible way, a front end must
26287 request that this functionality be enabled.
26289 Once enabled, this feature cannot be disabled.
26291 Note that if Python support has not been compiled into @value{GDBN},
26292 this command will still succeed (and do nothing).
26294 This feature is currently (as of @value{GDBN} 7.0) experimental, and
26295 may work differently in future versions of @value{GDBN}.
26297 @subheading The @code{-var-create} Command
26298 @findex -var-create
26300 @subsubheading Synopsis
26303 -var-create @{@var{name} | "-"@}
26304 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
26307 This operation creates a variable object, which allows the monitoring of
26308 a variable, the result of an expression, a memory cell or a CPU
26311 The @var{name} parameter is the string by which the object can be
26312 referenced. It must be unique. If @samp{-} is specified, the varobj
26313 system will generate a string ``varNNNNNN'' automatically. It will be
26314 unique provided that one does not specify @var{name} of that format.
26315 The command fails if a duplicate name is found.
26317 The frame under which the expression should be evaluated can be
26318 specified by @var{frame-addr}. A @samp{*} indicates that the current
26319 frame should be used. A @samp{@@} indicates that a floating variable
26320 object must be created.
26322 @var{expression} is any expression valid on the current language set (must not
26323 begin with a @samp{*}), or one of the following:
26327 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
26330 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
26333 @samp{$@var{regname}} --- a CPU register name
26336 @cindex dynamic varobj
26337 A varobj's contents may be provided by a Python-based pretty-printer. In this
26338 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
26339 have slightly different semantics in some cases. If the
26340 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
26341 will never create a dynamic varobj. This ensures backward
26342 compatibility for existing clients.
26344 @subsubheading Result
26346 This operation returns attributes of the newly-created varobj. These
26351 The name of the varobj.
26354 The number of children of the varobj. This number is not necessarily
26355 reliable for a dynamic varobj. Instead, you must examine the
26356 @samp{has_more} attribute.
26359 The varobj's scalar value. For a varobj whose type is some sort of
26360 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
26361 will not be interesting.
26364 The varobj's type. This is a string representation of the type, as
26365 would be printed by the @value{GDBN} CLI.
26368 If a variable object is bound to a specific thread, then this is the
26369 thread's identifier.
26372 For a dynamic varobj, this indicates whether there appear to be any
26373 children available. For a non-dynamic varobj, this will be 0.
26376 This attribute will be present and have the value @samp{1} if the
26377 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26378 then this attribute will not be present.
26381 A dynamic varobj can supply a display hint to the front end. The
26382 value comes directly from the Python pretty-printer object's
26383 @code{display_hint} method. @xref{Pretty Printing API}.
26386 Typical output will look like this:
26389 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
26390 has_more="@var{has_more}"
26394 @subheading The @code{-var-delete} Command
26395 @findex -var-delete
26397 @subsubheading Synopsis
26400 -var-delete [ -c ] @var{name}
26403 Deletes a previously created variable object and all of its children.
26404 With the @samp{-c} option, just deletes the children.
26406 Returns an error if the object @var{name} is not found.
26409 @subheading The @code{-var-set-format} Command
26410 @findex -var-set-format
26412 @subsubheading Synopsis
26415 -var-set-format @var{name} @var{format-spec}
26418 Sets the output format for the value of the object @var{name} to be
26421 @anchor{-var-set-format}
26422 The syntax for the @var{format-spec} is as follows:
26425 @var{format-spec} @expansion{}
26426 @{binary | decimal | hexadecimal | octal | natural@}
26429 The natural format is the default format choosen automatically
26430 based on the variable type (like decimal for an @code{int}, hex
26431 for pointers, etc.).
26433 For a variable with children, the format is set only on the
26434 variable itself, and the children are not affected.
26436 @subheading The @code{-var-show-format} Command
26437 @findex -var-show-format
26439 @subsubheading Synopsis
26442 -var-show-format @var{name}
26445 Returns the format used to display the value of the object @var{name}.
26448 @var{format} @expansion{}
26453 @subheading The @code{-var-info-num-children} Command
26454 @findex -var-info-num-children
26456 @subsubheading Synopsis
26459 -var-info-num-children @var{name}
26462 Returns the number of children of a variable object @var{name}:
26468 Note that this number is not completely reliable for a dynamic varobj.
26469 It will return the current number of children, but more children may
26473 @subheading The @code{-var-list-children} Command
26474 @findex -var-list-children
26476 @subsubheading Synopsis
26479 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
26481 @anchor{-var-list-children}
26483 Return a list of the children of the specified variable object and
26484 create variable objects for them, if they do not already exist. With
26485 a single argument or if @var{print-values} has a value of 0 or
26486 @code{--no-values}, print only the names of the variables; if
26487 @var{print-values} is 1 or @code{--all-values}, also print their
26488 values; and if it is 2 or @code{--simple-values} print the name and
26489 value for simple data types and just the name for arrays, structures
26492 @var{from} and @var{to}, if specified, indicate the range of children
26493 to report. If @var{from} or @var{to} is less than zero, the range is
26494 reset and all children will be reported. Otherwise, children starting
26495 at @var{from} (zero-based) and up to and excluding @var{to} will be
26498 If a child range is requested, it will only affect the current call to
26499 @code{-var-list-children}, but not future calls to @code{-var-update}.
26500 For this, you must instead use @code{-var-set-update-range}. The
26501 intent of this approach is to enable a front end to implement any
26502 update approach it likes; for example, scrolling a view may cause the
26503 front end to request more children with @code{-var-list-children}, and
26504 then the front end could call @code{-var-set-update-range} with a
26505 different range to ensure that future updates are restricted to just
26508 For each child the following results are returned:
26513 Name of the variable object created for this child.
26516 The expression to be shown to the user by the front end to designate this child.
26517 For example this may be the name of a structure member.
26519 For a dynamic varobj, this value cannot be used to form an
26520 expression. There is no way to do this at all with a dynamic varobj.
26522 For C/C@t{++} structures there are several pseudo children returned to
26523 designate access qualifiers. For these pseudo children @var{exp} is
26524 @samp{public}, @samp{private}, or @samp{protected}. In this case the
26525 type and value are not present.
26527 A dynamic varobj will not report the access qualifying
26528 pseudo-children, regardless of the language. This information is not
26529 available at all with a dynamic varobj.
26532 Number of children this child has. For a dynamic varobj, this will be
26536 The type of the child.
26539 If values were requested, this is the value.
26542 If this variable object is associated with a thread, this is the thread id.
26543 Otherwise this result is not present.
26546 If the variable object is frozen, this variable will be present with a value of 1.
26549 The result may have its own attributes:
26553 A dynamic varobj can supply a display hint to the front end. The
26554 value comes directly from the Python pretty-printer object's
26555 @code{display_hint} method. @xref{Pretty Printing API}.
26558 This is an integer attribute which is nonzero if there are children
26559 remaining after the end of the selected range.
26562 @subsubheading Example
26566 -var-list-children n
26567 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26568 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
26570 -var-list-children --all-values n
26571 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26572 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
26576 @subheading The @code{-var-info-type} Command
26577 @findex -var-info-type
26579 @subsubheading Synopsis
26582 -var-info-type @var{name}
26585 Returns the type of the specified variable @var{name}. The type is
26586 returned as a string in the same format as it is output by the
26590 type=@var{typename}
26594 @subheading The @code{-var-info-expression} Command
26595 @findex -var-info-expression
26597 @subsubheading Synopsis
26600 -var-info-expression @var{name}
26603 Returns a string that is suitable for presenting this
26604 variable object in user interface. The string is generally
26605 not valid expression in the current language, and cannot be evaluated.
26607 For example, if @code{a} is an array, and variable object
26608 @code{A} was created for @code{a}, then we'll get this output:
26611 (gdb) -var-info-expression A.1
26612 ^done,lang="C",exp="1"
26616 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
26618 Note that the output of the @code{-var-list-children} command also
26619 includes those expressions, so the @code{-var-info-expression} command
26622 @subheading The @code{-var-info-path-expression} Command
26623 @findex -var-info-path-expression
26625 @subsubheading Synopsis
26628 -var-info-path-expression @var{name}
26631 Returns an expression that can be evaluated in the current
26632 context and will yield the same value that a variable object has.
26633 Compare this with the @code{-var-info-expression} command, which
26634 result can be used only for UI presentation. Typical use of
26635 the @code{-var-info-path-expression} command is creating a
26636 watchpoint from a variable object.
26638 This command is currently not valid for children of a dynamic varobj,
26639 and will give an error when invoked on one.
26641 For example, suppose @code{C} is a C@t{++} class, derived from class
26642 @code{Base}, and that the @code{Base} class has a member called
26643 @code{m_size}. Assume a variable @code{c} is has the type of
26644 @code{C} and a variable object @code{C} was created for variable
26645 @code{c}. Then, we'll get this output:
26647 (gdb) -var-info-path-expression C.Base.public.m_size
26648 ^done,path_expr=((Base)c).m_size)
26651 @subheading The @code{-var-show-attributes} Command
26652 @findex -var-show-attributes
26654 @subsubheading Synopsis
26657 -var-show-attributes @var{name}
26660 List attributes of the specified variable object @var{name}:
26663 status=@var{attr} [ ( ,@var{attr} )* ]
26667 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
26669 @subheading The @code{-var-evaluate-expression} Command
26670 @findex -var-evaluate-expression
26672 @subsubheading Synopsis
26675 -var-evaluate-expression [-f @var{format-spec}] @var{name}
26678 Evaluates the expression that is represented by the specified variable
26679 object and returns its value as a string. The format of the string
26680 can be specified with the @samp{-f} option. The possible values of
26681 this option are the same as for @code{-var-set-format}
26682 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
26683 the current display format will be used. The current display format
26684 can be changed using the @code{-var-set-format} command.
26690 Note that one must invoke @code{-var-list-children} for a variable
26691 before the value of a child variable can be evaluated.
26693 @subheading The @code{-var-assign} Command
26694 @findex -var-assign
26696 @subsubheading Synopsis
26699 -var-assign @var{name} @var{expression}
26702 Assigns the value of @var{expression} to the variable object specified
26703 by @var{name}. The object must be @samp{editable}. If the variable's
26704 value is altered by the assign, the variable will show up in any
26705 subsequent @code{-var-update} list.
26707 @subsubheading Example
26715 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
26719 @subheading The @code{-var-update} Command
26720 @findex -var-update
26722 @subsubheading Synopsis
26725 -var-update [@var{print-values}] @{@var{name} | "*"@}
26728 Reevaluate the expressions corresponding to the variable object
26729 @var{name} and all its direct and indirect children, and return the
26730 list of variable objects whose values have changed; @var{name} must
26731 be a root variable object. Here, ``changed'' means that the result of
26732 @code{-var-evaluate-expression} before and after the
26733 @code{-var-update} is different. If @samp{*} is used as the variable
26734 object names, all existing variable objects are updated, except
26735 for frozen ones (@pxref{-var-set-frozen}). The option
26736 @var{print-values} determines whether both names and values, or just
26737 names are printed. The possible values of this option are the same
26738 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
26739 recommended to use the @samp{--all-values} option, to reduce the
26740 number of MI commands needed on each program stop.
26742 With the @samp{*} parameter, if a variable object is bound to a
26743 currently running thread, it will not be updated, without any
26746 If @code{-var-set-update-range} was previously used on a varobj, then
26747 only the selected range of children will be reported.
26749 @code{-var-update} reports all the changed varobjs in a tuple named
26752 Each item in the change list is itself a tuple holding:
26756 The name of the varobj.
26759 If values were requested for this update, then this field will be
26760 present and will hold the value of the varobj.
26763 @anchor{-var-update}
26764 This field is a string which may take one of three values:
26768 The variable object's current value is valid.
26771 The variable object does not currently hold a valid value but it may
26772 hold one in the future if its associated expression comes back into
26776 The variable object no longer holds a valid value.
26777 This can occur when the executable file being debugged has changed,
26778 either through recompilation or by using the @value{GDBN} @code{file}
26779 command. The front end should normally choose to delete these variable
26783 In the future new values may be added to this list so the front should
26784 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
26787 This is only present if the varobj is still valid. If the type
26788 changed, then this will be the string @samp{true}; otherwise it will
26792 If the varobj's type changed, then this field will be present and will
26795 @item new_num_children
26796 For a dynamic varobj, if the number of children changed, or if the
26797 type changed, this will be the new number of children.
26799 The @samp{numchild} field in other varobj responses is generally not
26800 valid for a dynamic varobj -- it will show the number of children that
26801 @value{GDBN} knows about, but because dynamic varobjs lazily
26802 instantiate their children, this will not reflect the number of
26803 children which may be available.
26805 The @samp{new_num_children} attribute only reports changes to the
26806 number of children known by @value{GDBN}. This is the only way to
26807 detect whether an update has removed children (which necessarily can
26808 only happen at the end of the update range).
26811 The display hint, if any.
26814 This is an integer value, which will be 1 if there are more children
26815 available outside the varobj's update range.
26818 This attribute will be present and have the value @samp{1} if the
26819 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26820 then this attribute will not be present.
26823 If new children were added to a dynamic varobj within the selected
26824 update range (as set by @code{-var-set-update-range}), then they will
26825 be listed in this attribute.
26828 @subsubheading Example
26835 -var-update --all-values var1
26836 ^done,changelist=[@{name="var1",value="3",in_scope="true",
26837 type_changed="false"@}]
26841 @subheading The @code{-var-set-frozen} Command
26842 @findex -var-set-frozen
26843 @anchor{-var-set-frozen}
26845 @subsubheading Synopsis
26848 -var-set-frozen @var{name} @var{flag}
26851 Set the frozenness flag on the variable object @var{name}. The
26852 @var{flag} parameter should be either @samp{1} to make the variable
26853 frozen or @samp{0} to make it unfrozen. If a variable object is
26854 frozen, then neither itself, nor any of its children, are
26855 implicitly updated by @code{-var-update} of
26856 a parent variable or by @code{-var-update *}. Only
26857 @code{-var-update} of the variable itself will update its value and
26858 values of its children. After a variable object is unfrozen, it is
26859 implicitly updated by all subsequent @code{-var-update} operations.
26860 Unfreezing a variable does not update it, only subsequent
26861 @code{-var-update} does.
26863 @subsubheading Example
26867 -var-set-frozen V 1
26872 @subheading The @code{-var-set-update-range} command
26873 @findex -var-set-update-range
26874 @anchor{-var-set-update-range}
26876 @subsubheading Synopsis
26879 -var-set-update-range @var{name} @var{from} @var{to}
26882 Set the range of children to be returned by future invocations of
26883 @code{-var-update}.
26885 @var{from} and @var{to} indicate the range of children to report. If
26886 @var{from} or @var{to} is less than zero, the range is reset and all
26887 children will be reported. Otherwise, children starting at @var{from}
26888 (zero-based) and up to and excluding @var{to} will be reported.
26890 @subsubheading Example
26894 -var-set-update-range V 1 2
26898 @subheading The @code{-var-set-visualizer} command
26899 @findex -var-set-visualizer
26900 @anchor{-var-set-visualizer}
26902 @subsubheading Synopsis
26905 -var-set-visualizer @var{name} @var{visualizer}
26908 Set a visualizer for the variable object @var{name}.
26910 @var{visualizer} is the visualizer to use. The special value
26911 @samp{None} means to disable any visualizer in use.
26913 If not @samp{None}, @var{visualizer} must be a Python expression.
26914 This expression must evaluate to a callable object which accepts a
26915 single argument. @value{GDBN} will call this object with the value of
26916 the varobj @var{name} as an argument (this is done so that the same
26917 Python pretty-printing code can be used for both the CLI and MI).
26918 When called, this object must return an object which conforms to the
26919 pretty-printing interface (@pxref{Pretty Printing API}).
26921 The pre-defined function @code{gdb.default_visualizer} may be used to
26922 select a visualizer by following the built-in process
26923 (@pxref{Selecting Pretty-Printers}). This is done automatically when
26924 a varobj is created, and so ordinarily is not needed.
26926 This feature is only available if Python support is enabled. The MI
26927 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
26928 can be used to check this.
26930 @subsubheading Example
26932 Resetting the visualizer:
26936 -var-set-visualizer V None
26940 Reselecting the default (type-based) visualizer:
26944 -var-set-visualizer V gdb.default_visualizer
26948 Suppose @code{SomeClass} is a visualizer class. A lambda expression
26949 can be used to instantiate this class for a varobj:
26953 -var-set-visualizer V "lambda val: SomeClass()"
26957 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26958 @node GDB/MI Data Manipulation
26959 @section @sc{gdb/mi} Data Manipulation
26961 @cindex data manipulation, in @sc{gdb/mi}
26962 @cindex @sc{gdb/mi}, data manipulation
26963 This section describes the @sc{gdb/mi} commands that manipulate data:
26964 examine memory and registers, evaluate expressions, etc.
26966 @c REMOVED FROM THE INTERFACE.
26967 @c @subheading -data-assign
26968 @c Change the value of a program variable. Plenty of side effects.
26969 @c @subsubheading GDB Command
26971 @c @subsubheading Example
26974 @subheading The @code{-data-disassemble} Command
26975 @findex -data-disassemble
26977 @subsubheading Synopsis
26981 [ -s @var{start-addr} -e @var{end-addr} ]
26982 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
26990 @item @var{start-addr}
26991 is the beginning address (or @code{$pc})
26992 @item @var{end-addr}
26994 @item @var{filename}
26995 is the name of the file to disassemble
26996 @item @var{linenum}
26997 is the line number to disassemble around
26999 is the number of disassembly lines to be produced. If it is -1,
27000 the whole function will be disassembled, in case no @var{end-addr} is
27001 specified. If @var{end-addr} is specified as a non-zero value, and
27002 @var{lines} is lower than the number of disassembly lines between
27003 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
27004 displayed; if @var{lines} is higher than the number of lines between
27005 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
27008 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
27012 @subsubheading Result
27014 The output for each instruction is composed of four fields:
27023 Note that whatever included in the instruction field, is not manipulated
27024 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
27026 @subsubheading @value{GDBN} Command
27028 There's no direct mapping from this command to the CLI.
27030 @subsubheading Example
27032 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
27036 -data-disassemble -s $pc -e "$pc + 20" -- 0
27039 @{address="0x000107c0",func-name="main",offset="4",
27040 inst="mov 2, %o0"@},
27041 @{address="0x000107c4",func-name="main",offset="8",
27042 inst="sethi %hi(0x11800), %o2"@},
27043 @{address="0x000107c8",func-name="main",offset="12",
27044 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
27045 @{address="0x000107cc",func-name="main",offset="16",
27046 inst="sethi %hi(0x11800), %o2"@},
27047 @{address="0x000107d0",func-name="main",offset="20",
27048 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
27052 Disassemble the whole @code{main} function. Line 32 is part of
27056 -data-disassemble -f basics.c -l 32 -- 0
27058 @{address="0x000107bc",func-name="main",offset="0",
27059 inst="save %sp, -112, %sp"@},
27060 @{address="0x000107c0",func-name="main",offset="4",
27061 inst="mov 2, %o0"@},
27062 @{address="0x000107c4",func-name="main",offset="8",
27063 inst="sethi %hi(0x11800), %o2"@},
27065 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
27066 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
27070 Disassemble 3 instructions from the start of @code{main}:
27074 -data-disassemble -f basics.c -l 32 -n 3 -- 0
27076 @{address="0x000107bc",func-name="main",offset="0",
27077 inst="save %sp, -112, %sp"@},
27078 @{address="0x000107c0",func-name="main",offset="4",
27079 inst="mov 2, %o0"@},
27080 @{address="0x000107c4",func-name="main",offset="8",
27081 inst="sethi %hi(0x11800), %o2"@}]
27085 Disassemble 3 instructions from the start of @code{main} in mixed mode:
27089 -data-disassemble -f basics.c -l 32 -n 3 -- 1
27091 src_and_asm_line=@{line="31",
27092 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27093 testsuite/gdb.mi/basics.c",line_asm_insn=[
27094 @{address="0x000107bc",func-name="main",offset="0",
27095 inst="save %sp, -112, %sp"@}]@},
27096 src_and_asm_line=@{line="32",
27097 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27098 testsuite/gdb.mi/basics.c",line_asm_insn=[
27099 @{address="0x000107c0",func-name="main",offset="4",
27100 inst="mov 2, %o0"@},
27101 @{address="0x000107c4",func-name="main",offset="8",
27102 inst="sethi %hi(0x11800), %o2"@}]@}]
27107 @subheading The @code{-data-evaluate-expression} Command
27108 @findex -data-evaluate-expression
27110 @subsubheading Synopsis
27113 -data-evaluate-expression @var{expr}
27116 Evaluate @var{expr} as an expression. The expression could contain an
27117 inferior function call. The function call will execute synchronously.
27118 If the expression contains spaces, it must be enclosed in double quotes.
27120 @subsubheading @value{GDBN} Command
27122 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
27123 @samp{call}. In @code{gdbtk} only, there's a corresponding
27124 @samp{gdb_eval} command.
27126 @subsubheading Example
27128 In the following example, the numbers that precede the commands are the
27129 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
27130 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
27134 211-data-evaluate-expression A
27137 311-data-evaluate-expression &A
27138 311^done,value="0xefffeb7c"
27140 411-data-evaluate-expression A+3
27143 511-data-evaluate-expression "A + 3"
27149 @subheading The @code{-data-list-changed-registers} Command
27150 @findex -data-list-changed-registers
27152 @subsubheading Synopsis
27155 -data-list-changed-registers
27158 Display a list of the registers that have changed.
27160 @subsubheading @value{GDBN} Command
27162 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
27163 has the corresponding command @samp{gdb_changed_register_list}.
27165 @subsubheading Example
27167 On a PPC MBX board:
27175 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
27176 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
27179 -data-list-changed-registers
27180 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
27181 "10","11","13","14","15","16","17","18","19","20","21","22","23",
27182 "24","25","26","27","28","30","31","64","65","66","67","69"]
27187 @subheading The @code{-data-list-register-names} Command
27188 @findex -data-list-register-names
27190 @subsubheading Synopsis
27193 -data-list-register-names [ ( @var{regno} )+ ]
27196 Show a list of register names for the current target. If no arguments
27197 are given, it shows a list of the names of all the registers. If
27198 integer numbers are given as arguments, it will print a list of the
27199 names of the registers corresponding to the arguments. To ensure
27200 consistency between a register name and its number, the output list may
27201 include empty register names.
27203 @subsubheading @value{GDBN} Command
27205 @value{GDBN} does not have a command which corresponds to
27206 @samp{-data-list-register-names}. In @code{gdbtk} there is a
27207 corresponding command @samp{gdb_regnames}.
27209 @subsubheading Example
27211 For the PPC MBX board:
27214 -data-list-register-names
27215 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
27216 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
27217 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
27218 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
27219 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
27220 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
27221 "", "pc","ps","cr","lr","ctr","xer"]
27223 -data-list-register-names 1 2 3
27224 ^done,register-names=["r1","r2","r3"]
27228 @subheading The @code{-data-list-register-values} Command
27229 @findex -data-list-register-values
27231 @subsubheading Synopsis
27234 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
27237 Display the registers' contents. @var{fmt} is the format according to
27238 which the registers' contents are to be returned, followed by an optional
27239 list of numbers specifying the registers to display. A missing list of
27240 numbers indicates that the contents of all the registers must be returned.
27242 Allowed formats for @var{fmt} are:
27259 @subsubheading @value{GDBN} Command
27261 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
27262 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
27264 @subsubheading Example
27266 For a PPC MBX board (note: line breaks are for readability only, they
27267 don't appear in the actual output):
27271 -data-list-register-values r 64 65
27272 ^done,register-values=[@{number="64",value="0xfe00a300"@},
27273 @{number="65",value="0x00029002"@}]
27275 -data-list-register-values x
27276 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
27277 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
27278 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
27279 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
27280 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
27281 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
27282 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
27283 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
27284 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
27285 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
27286 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
27287 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
27288 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
27289 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
27290 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
27291 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
27292 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
27293 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
27294 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
27295 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
27296 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
27297 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
27298 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
27299 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
27300 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
27301 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
27302 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
27303 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
27304 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
27305 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
27306 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
27307 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
27308 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
27309 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
27310 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
27311 @{number="69",value="0x20002b03"@}]
27316 @subheading The @code{-data-read-memory} Command
27317 @findex -data-read-memory
27319 @subsubheading Synopsis
27322 -data-read-memory [ -o @var{byte-offset} ]
27323 @var{address} @var{word-format} @var{word-size}
27324 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
27331 @item @var{address}
27332 An expression specifying the address of the first memory word to be
27333 read. Complex expressions containing embedded white space should be
27334 quoted using the C convention.
27336 @item @var{word-format}
27337 The format to be used to print the memory words. The notation is the
27338 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
27341 @item @var{word-size}
27342 The size of each memory word in bytes.
27344 @item @var{nr-rows}
27345 The number of rows in the output table.
27347 @item @var{nr-cols}
27348 The number of columns in the output table.
27351 If present, indicates that each row should include an @sc{ascii} dump. The
27352 value of @var{aschar} is used as a padding character when a byte is not a
27353 member of the printable @sc{ascii} character set (printable @sc{ascii}
27354 characters are those whose code is between 32 and 126, inclusively).
27356 @item @var{byte-offset}
27357 An offset to add to the @var{address} before fetching memory.
27360 This command displays memory contents as a table of @var{nr-rows} by
27361 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
27362 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
27363 (returned as @samp{total-bytes}). Should less than the requested number
27364 of bytes be returned by the target, the missing words are identified
27365 using @samp{N/A}. The number of bytes read from the target is returned
27366 in @samp{nr-bytes} and the starting address used to read memory in
27369 The address of the next/previous row or page is available in
27370 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
27373 @subsubheading @value{GDBN} Command
27375 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
27376 @samp{gdb_get_mem} memory read command.
27378 @subsubheading Example
27380 Read six bytes of memory starting at @code{bytes+6} but then offset by
27381 @code{-6} bytes. Format as three rows of two columns. One byte per
27382 word. Display each word in hex.
27386 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
27387 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
27388 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
27389 prev-page="0x0000138a",memory=[
27390 @{addr="0x00001390",data=["0x00","0x01"]@},
27391 @{addr="0x00001392",data=["0x02","0x03"]@},
27392 @{addr="0x00001394",data=["0x04","0x05"]@}]
27396 Read two bytes of memory starting at address @code{shorts + 64} and
27397 display as a single word formatted in decimal.
27401 5-data-read-memory shorts+64 d 2 1 1
27402 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
27403 next-row="0x00001512",prev-row="0x0000150e",
27404 next-page="0x00001512",prev-page="0x0000150e",memory=[
27405 @{addr="0x00001510",data=["128"]@}]
27409 Read thirty two bytes of memory starting at @code{bytes+16} and format
27410 as eight rows of four columns. Include a string encoding with @samp{x}
27411 used as the non-printable character.
27415 4-data-read-memory bytes+16 x 1 8 4 x
27416 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
27417 next-row="0x000013c0",prev-row="0x0000139c",
27418 next-page="0x000013c0",prev-page="0x00001380",memory=[
27419 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
27420 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
27421 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
27422 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
27423 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
27424 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
27425 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
27426 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
27430 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27431 @node GDB/MI Tracepoint Commands
27432 @section @sc{gdb/mi} Tracepoint Commands
27434 The commands defined in this section implement MI support for
27435 tracepoints. For detailed introduction, see @ref{Tracepoints}.
27437 @subheading The @code{-trace-find} Command
27438 @findex -trace-find
27440 @subsubheading Synopsis
27443 -trace-find @var{mode} [@var{parameters}@dots{}]
27446 Find a trace frame using criteria defined by @var{mode} and
27447 @var{parameters}. The following table lists permissible
27448 modes and their parameters. For details of operation, see @ref{tfind}.
27453 No parameters are required. Stops examining trace frames.
27456 An integer is required as parameter. Selects tracepoint frame with
27459 @item tracepoint-number
27460 An integer is required as parameter. Finds next
27461 trace frame that corresponds to tracepoint with the specified number.
27464 An address is required as parameter. Finds
27465 next trace frame that corresponds to any tracepoint at the specified
27468 @item pc-inside-range
27469 Two addresses are required as parameters. Finds next trace
27470 frame that corresponds to a tracepoint at an address inside the
27471 specified range. Both bounds are considered to be inside the range.
27473 @item pc-outside-range
27474 Two addresses are required as parameters. Finds
27475 next trace frame that corresponds to a tracepoint at an address outside
27476 the specified range. Both bounds are considered to be inside the range.
27479 Line specification is required as parameter. @xref{Specify Location}.
27480 Finds next trace frame that corresponds to a tracepoint at
27481 the specified location.
27485 If @samp{none} was passed as @var{mode}, the response does not
27486 have fields. Otherwise, the response may have the following fields:
27490 This field has either @samp{0} or @samp{1} as the value, depending
27491 on whether a matching tracepoint was found.
27494 The index of the found traceframe. This field is present iff
27495 the @samp{found} field has value of @samp{1}.
27498 The index of the found tracepoint. This field is present iff
27499 the @samp{found} field has value of @samp{1}.
27502 The information about the frame corresponding to the found trace
27503 frame. This field is present only if a trace frame was found.
27504 @xref{GDB/MI Frame Information}, for description of this field.
27508 @subsubheading @value{GDBN} Command
27510 The corresponding @value{GDBN} command is @samp{tfind}.
27512 @subheading -trace-define-variable
27513 @findex -trace-define-variable
27515 @subsubheading Synopsis
27518 -trace-define-variable @var{name} [ @var{value} ]
27521 Create trace variable @var{name} if it does not exist. If
27522 @var{value} is specified, sets the initial value of the specified
27523 trace variable to that value. Note that the @var{name} should start
27524 with the @samp{$} character.
27526 @subsubheading @value{GDBN} Command
27528 The corresponding @value{GDBN} command is @samp{tvariable}.
27530 @subheading -trace-list-variables
27531 @findex -trace-list-variables
27533 @subsubheading Synopsis
27536 -trace-list-variables
27539 Return a table of all defined trace variables. Each element of the
27540 table has the following fields:
27544 The name of the trace variable. This field is always present.
27547 The initial value. This is a 64-bit signed integer. This
27548 field is always present.
27551 The value the trace variable has at the moment. This is a 64-bit
27552 signed integer. This field is absent iff current value is
27553 not defined, for example if the trace was never run, or is
27558 @subsubheading @value{GDBN} Command
27560 The corresponding @value{GDBN} command is @samp{tvariables}.
27562 @subsubheading Example
27566 -trace-list-variables
27567 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
27568 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
27569 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
27570 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
27571 body=[variable=@{name="$trace_timestamp",initial="0"@}
27572 variable=@{name="$foo",initial="10",current="15"@}]@}
27576 @subheading -trace-save
27577 @findex -trace-save
27579 @subsubheading Synopsis
27582 -trace-save [-r ] @var{filename}
27585 Saves the collected trace data to @var{filename}. Without the
27586 @samp{-r} option, the data is downloaded from the target and saved
27587 in a local file. With the @samp{-r} option the target is asked
27588 to perform the save.
27590 @subsubheading @value{GDBN} Command
27592 The corresponding @value{GDBN} command is @samp{tsave}.
27595 @subheading -trace-start
27596 @findex -trace-start
27598 @subsubheading Synopsis
27604 Starts a tracing experiments. The result of this command does not
27607 @subsubheading @value{GDBN} Command
27609 The corresponding @value{GDBN} command is @samp{tstart}.
27611 @subheading -trace-status
27612 @findex -trace-status
27614 @subsubheading Synopsis
27620 Obtains the status of a tracing experiment. The result may include
27621 the following fields:
27626 May have a value of either @samp{0}, when no tracing operations are
27627 supported, @samp{1}, when all tracing operations are supported, or
27628 @samp{file} when examining trace file. In the latter case, examining
27629 of trace frame is possible but new tracing experiement cannot be
27630 started. This field is always present.
27633 May have a value of either @samp{0} or @samp{1} depending on whether
27634 tracing experiement is in progress on target. This field is present
27635 if @samp{supported} field is not @samp{0}.
27638 Report the reason why the tracing was stopped last time. This field
27639 may be absent iff tracing was never stopped on target yet. The
27640 value of @samp{request} means the tracing was stopped as result of
27641 the @code{-trace-stop} command. The value of @samp{overflow} means
27642 the tracing buffer is full. The value of @samp{disconnection} means
27643 tracing was automatically stopped when @value{GDBN} has disconnected.
27644 The value of @samp{passcount} means tracing was stopped when a
27645 tracepoint was passed a maximal number of times for that tracepoint.
27646 This field is present if @samp{supported} field is not @samp{0}.
27648 @item stopping-tracepoint
27649 The number of tracepoint whose passcount as exceeded. This field is
27650 present iff the @samp{stop-reason} field has the value of
27654 @itemx frames-created
27655 The @samp{frames} field is a count of the total number of trace frames
27656 in the trace buffer, while @samp{frames-created} is the total created
27657 during the run, including ones that were discarded, such as when a
27658 circular trace buffer filled up. Both fields are optional.
27662 These fields tell the current size of the tracing buffer and the
27663 remaining space. These fields are optional.
27666 The value of the circular trace buffer flag. @code{1} means that the
27667 trace buffer is circular and old trace frames will be discarded if
27668 necessary to make room, @code{0} means that the trace buffer is linear
27672 The value of the disconnected tracing flag. @code{1} means that
27673 tracing will continue after @value{GDBN} disconnects, @code{0} means
27674 that the trace run will stop.
27678 @subsubheading @value{GDBN} Command
27680 The corresponding @value{GDBN} command is @samp{tstatus}.
27682 @subheading -trace-stop
27683 @findex -trace-stop
27685 @subsubheading Synopsis
27691 Stops a tracing experiment. The result of this command has the same
27692 fields as @code{-trace-status}, except that the @samp{supported} and
27693 @samp{running} fields are not output.
27695 @subsubheading @value{GDBN} Command
27697 The corresponding @value{GDBN} command is @samp{tstop}.
27700 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27701 @node GDB/MI Symbol Query
27702 @section @sc{gdb/mi} Symbol Query Commands
27706 @subheading The @code{-symbol-info-address} Command
27707 @findex -symbol-info-address
27709 @subsubheading Synopsis
27712 -symbol-info-address @var{symbol}
27715 Describe where @var{symbol} is stored.
27717 @subsubheading @value{GDBN} Command
27719 The corresponding @value{GDBN} command is @samp{info address}.
27721 @subsubheading Example
27725 @subheading The @code{-symbol-info-file} Command
27726 @findex -symbol-info-file
27728 @subsubheading Synopsis
27734 Show the file for the symbol.
27736 @subsubheading @value{GDBN} Command
27738 There's no equivalent @value{GDBN} command. @code{gdbtk} has
27739 @samp{gdb_find_file}.
27741 @subsubheading Example
27745 @subheading The @code{-symbol-info-function} Command
27746 @findex -symbol-info-function
27748 @subsubheading Synopsis
27751 -symbol-info-function
27754 Show which function the symbol lives in.
27756 @subsubheading @value{GDBN} Command
27758 @samp{gdb_get_function} in @code{gdbtk}.
27760 @subsubheading Example
27764 @subheading The @code{-symbol-info-line} Command
27765 @findex -symbol-info-line
27767 @subsubheading Synopsis
27773 Show the core addresses of the code for a source line.
27775 @subsubheading @value{GDBN} Command
27777 The corresponding @value{GDBN} command is @samp{info line}.
27778 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
27780 @subsubheading Example
27784 @subheading The @code{-symbol-info-symbol} Command
27785 @findex -symbol-info-symbol
27787 @subsubheading Synopsis
27790 -symbol-info-symbol @var{addr}
27793 Describe what symbol is at location @var{addr}.
27795 @subsubheading @value{GDBN} Command
27797 The corresponding @value{GDBN} command is @samp{info symbol}.
27799 @subsubheading Example
27803 @subheading The @code{-symbol-list-functions} Command
27804 @findex -symbol-list-functions
27806 @subsubheading Synopsis
27809 -symbol-list-functions
27812 List the functions in the executable.
27814 @subsubheading @value{GDBN} Command
27816 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
27817 @samp{gdb_search} in @code{gdbtk}.
27819 @subsubheading Example
27824 @subheading The @code{-symbol-list-lines} Command
27825 @findex -symbol-list-lines
27827 @subsubheading Synopsis
27830 -symbol-list-lines @var{filename}
27833 Print the list of lines that contain code and their associated program
27834 addresses for the given source filename. The entries are sorted in
27835 ascending PC order.
27837 @subsubheading @value{GDBN} Command
27839 There is no corresponding @value{GDBN} command.
27841 @subsubheading Example
27844 -symbol-list-lines basics.c
27845 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
27851 @subheading The @code{-symbol-list-types} Command
27852 @findex -symbol-list-types
27854 @subsubheading Synopsis
27860 List all the type names.
27862 @subsubheading @value{GDBN} Command
27864 The corresponding commands are @samp{info types} in @value{GDBN},
27865 @samp{gdb_search} in @code{gdbtk}.
27867 @subsubheading Example
27871 @subheading The @code{-symbol-list-variables} Command
27872 @findex -symbol-list-variables
27874 @subsubheading Synopsis
27877 -symbol-list-variables
27880 List all the global and static variable names.
27882 @subsubheading @value{GDBN} Command
27884 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
27886 @subsubheading Example
27890 @subheading The @code{-symbol-locate} Command
27891 @findex -symbol-locate
27893 @subsubheading Synopsis
27899 @subsubheading @value{GDBN} Command
27901 @samp{gdb_loc} in @code{gdbtk}.
27903 @subsubheading Example
27907 @subheading The @code{-symbol-type} Command
27908 @findex -symbol-type
27910 @subsubheading Synopsis
27913 -symbol-type @var{variable}
27916 Show type of @var{variable}.
27918 @subsubheading @value{GDBN} Command
27920 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
27921 @samp{gdb_obj_variable}.
27923 @subsubheading Example
27928 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27929 @node GDB/MI File Commands
27930 @section @sc{gdb/mi} File Commands
27932 This section describes the GDB/MI commands to specify executable file names
27933 and to read in and obtain symbol table information.
27935 @subheading The @code{-file-exec-and-symbols} Command
27936 @findex -file-exec-and-symbols
27938 @subsubheading Synopsis
27941 -file-exec-and-symbols @var{file}
27944 Specify the executable file to be debugged. This file is the one from
27945 which the symbol table is also read. If no file is specified, the
27946 command clears the executable and symbol information. If breakpoints
27947 are set when using this command with no arguments, @value{GDBN} will produce
27948 error messages. Otherwise, no output is produced, except a completion
27951 @subsubheading @value{GDBN} Command
27953 The corresponding @value{GDBN} command is @samp{file}.
27955 @subsubheading Example
27959 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27965 @subheading The @code{-file-exec-file} Command
27966 @findex -file-exec-file
27968 @subsubheading Synopsis
27971 -file-exec-file @var{file}
27974 Specify the executable file to be debugged. Unlike
27975 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
27976 from this file. If used without argument, @value{GDBN} clears the information
27977 about the executable file. No output is produced, except a completion
27980 @subsubheading @value{GDBN} Command
27982 The corresponding @value{GDBN} command is @samp{exec-file}.
27984 @subsubheading Example
27988 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27995 @subheading The @code{-file-list-exec-sections} Command
27996 @findex -file-list-exec-sections
27998 @subsubheading Synopsis
28001 -file-list-exec-sections
28004 List the sections of the current executable file.
28006 @subsubheading @value{GDBN} Command
28008 The @value{GDBN} command @samp{info file} shows, among the rest, the same
28009 information as this command. @code{gdbtk} has a corresponding command
28010 @samp{gdb_load_info}.
28012 @subsubheading Example
28017 @subheading The @code{-file-list-exec-source-file} Command
28018 @findex -file-list-exec-source-file
28020 @subsubheading Synopsis
28023 -file-list-exec-source-file
28026 List the line number, the current source file, and the absolute path
28027 to the current source file for the current executable. The macro
28028 information field has a value of @samp{1} or @samp{0} depending on
28029 whether or not the file includes preprocessor macro information.
28031 @subsubheading @value{GDBN} Command
28033 The @value{GDBN} equivalent is @samp{info source}
28035 @subsubheading Example
28039 123-file-list-exec-source-file
28040 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
28045 @subheading The @code{-file-list-exec-source-files} Command
28046 @findex -file-list-exec-source-files
28048 @subsubheading Synopsis
28051 -file-list-exec-source-files
28054 List the source files for the current executable.
28056 It will always output the filename, but only when @value{GDBN} can find
28057 the absolute file name of a source file, will it output the fullname.
28059 @subsubheading @value{GDBN} Command
28061 The @value{GDBN} equivalent is @samp{info sources}.
28062 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
28064 @subsubheading Example
28067 -file-list-exec-source-files
28069 @{file=foo.c,fullname=/home/foo.c@},
28070 @{file=/home/bar.c,fullname=/home/bar.c@},
28071 @{file=gdb_could_not_find_fullpath.c@}]
28076 @subheading The @code{-file-list-shared-libraries} Command
28077 @findex -file-list-shared-libraries
28079 @subsubheading Synopsis
28082 -file-list-shared-libraries
28085 List the shared libraries in the program.
28087 @subsubheading @value{GDBN} Command
28089 The corresponding @value{GDBN} command is @samp{info shared}.
28091 @subsubheading Example
28095 @subheading The @code{-file-list-symbol-files} Command
28096 @findex -file-list-symbol-files
28098 @subsubheading Synopsis
28101 -file-list-symbol-files
28106 @subsubheading @value{GDBN} Command
28108 The corresponding @value{GDBN} command is @samp{info file} (part of it).
28110 @subsubheading Example
28115 @subheading The @code{-file-symbol-file} Command
28116 @findex -file-symbol-file
28118 @subsubheading Synopsis
28121 -file-symbol-file @var{file}
28124 Read symbol table info from the specified @var{file} argument. When
28125 used without arguments, clears @value{GDBN}'s symbol table info. No output is
28126 produced, except for a completion notification.
28128 @subsubheading @value{GDBN} Command
28130 The corresponding @value{GDBN} command is @samp{symbol-file}.
28132 @subsubheading Example
28136 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28142 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28143 @node GDB/MI Memory Overlay Commands
28144 @section @sc{gdb/mi} Memory Overlay Commands
28146 The memory overlay commands are not implemented.
28148 @c @subheading -overlay-auto
28150 @c @subheading -overlay-list-mapping-state
28152 @c @subheading -overlay-list-overlays
28154 @c @subheading -overlay-map
28156 @c @subheading -overlay-off
28158 @c @subheading -overlay-on
28160 @c @subheading -overlay-unmap
28162 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28163 @node GDB/MI Signal Handling Commands
28164 @section @sc{gdb/mi} Signal Handling Commands
28166 Signal handling commands are not implemented.
28168 @c @subheading -signal-handle
28170 @c @subheading -signal-list-handle-actions
28172 @c @subheading -signal-list-signal-types
28176 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28177 @node GDB/MI Target Manipulation
28178 @section @sc{gdb/mi} Target Manipulation Commands
28181 @subheading The @code{-target-attach} Command
28182 @findex -target-attach
28184 @subsubheading Synopsis
28187 -target-attach @var{pid} | @var{gid} | @var{file}
28190 Attach to a process @var{pid} or a file @var{file} outside of
28191 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
28192 group, the id previously returned by
28193 @samp{-list-thread-groups --available} must be used.
28195 @subsubheading @value{GDBN} Command
28197 The corresponding @value{GDBN} command is @samp{attach}.
28199 @subsubheading Example
28203 =thread-created,id="1"
28204 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
28210 @subheading The @code{-target-compare-sections} Command
28211 @findex -target-compare-sections
28213 @subsubheading Synopsis
28216 -target-compare-sections [ @var{section} ]
28219 Compare data of section @var{section} on target to the exec file.
28220 Without the argument, all sections are compared.
28222 @subsubheading @value{GDBN} Command
28224 The @value{GDBN} equivalent is @samp{compare-sections}.
28226 @subsubheading Example
28231 @subheading The @code{-target-detach} Command
28232 @findex -target-detach
28234 @subsubheading Synopsis
28237 -target-detach [ @var{pid} | @var{gid} ]
28240 Detach from the remote target which normally resumes its execution.
28241 If either @var{pid} or @var{gid} is specified, detaches from either
28242 the specified process, or specified thread group. There's no output.
28244 @subsubheading @value{GDBN} Command
28246 The corresponding @value{GDBN} command is @samp{detach}.
28248 @subsubheading Example
28258 @subheading The @code{-target-disconnect} Command
28259 @findex -target-disconnect
28261 @subsubheading Synopsis
28267 Disconnect from the remote target. There's no output and the target is
28268 generally not resumed.
28270 @subsubheading @value{GDBN} Command
28272 The corresponding @value{GDBN} command is @samp{disconnect}.
28274 @subsubheading Example
28284 @subheading The @code{-target-download} Command
28285 @findex -target-download
28287 @subsubheading Synopsis
28293 Loads the executable onto the remote target.
28294 It prints out an update message every half second, which includes the fields:
28298 The name of the section.
28300 The size of what has been sent so far for that section.
28302 The size of the section.
28304 The total size of what was sent so far (the current and the previous sections).
28306 The size of the overall executable to download.
28310 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
28311 @sc{gdb/mi} Output Syntax}).
28313 In addition, it prints the name and size of the sections, as they are
28314 downloaded. These messages include the following fields:
28318 The name of the section.
28320 The size of the section.
28322 The size of the overall executable to download.
28326 At the end, a summary is printed.
28328 @subsubheading @value{GDBN} Command
28330 The corresponding @value{GDBN} command is @samp{load}.
28332 @subsubheading Example
28334 Note: each status message appears on a single line. Here the messages
28335 have been broken down so that they can fit onto a page.
28340 +download,@{section=".text",section-size="6668",total-size="9880"@}
28341 +download,@{section=".text",section-sent="512",section-size="6668",
28342 total-sent="512",total-size="9880"@}
28343 +download,@{section=".text",section-sent="1024",section-size="6668",
28344 total-sent="1024",total-size="9880"@}
28345 +download,@{section=".text",section-sent="1536",section-size="6668",
28346 total-sent="1536",total-size="9880"@}
28347 +download,@{section=".text",section-sent="2048",section-size="6668",
28348 total-sent="2048",total-size="9880"@}
28349 +download,@{section=".text",section-sent="2560",section-size="6668",
28350 total-sent="2560",total-size="9880"@}
28351 +download,@{section=".text",section-sent="3072",section-size="6668",
28352 total-sent="3072",total-size="9880"@}
28353 +download,@{section=".text",section-sent="3584",section-size="6668",
28354 total-sent="3584",total-size="9880"@}
28355 +download,@{section=".text",section-sent="4096",section-size="6668",
28356 total-sent="4096",total-size="9880"@}
28357 +download,@{section=".text",section-sent="4608",section-size="6668",
28358 total-sent="4608",total-size="9880"@}
28359 +download,@{section=".text",section-sent="5120",section-size="6668",
28360 total-sent="5120",total-size="9880"@}
28361 +download,@{section=".text",section-sent="5632",section-size="6668",
28362 total-sent="5632",total-size="9880"@}
28363 +download,@{section=".text",section-sent="6144",section-size="6668",
28364 total-sent="6144",total-size="9880"@}
28365 +download,@{section=".text",section-sent="6656",section-size="6668",
28366 total-sent="6656",total-size="9880"@}
28367 +download,@{section=".init",section-size="28",total-size="9880"@}
28368 +download,@{section=".fini",section-size="28",total-size="9880"@}
28369 +download,@{section=".data",section-size="3156",total-size="9880"@}
28370 +download,@{section=".data",section-sent="512",section-size="3156",
28371 total-sent="7236",total-size="9880"@}
28372 +download,@{section=".data",section-sent="1024",section-size="3156",
28373 total-sent="7748",total-size="9880"@}
28374 +download,@{section=".data",section-sent="1536",section-size="3156",
28375 total-sent="8260",total-size="9880"@}
28376 +download,@{section=".data",section-sent="2048",section-size="3156",
28377 total-sent="8772",total-size="9880"@}
28378 +download,@{section=".data",section-sent="2560",section-size="3156",
28379 total-sent="9284",total-size="9880"@}
28380 +download,@{section=".data",section-sent="3072",section-size="3156",
28381 total-sent="9796",total-size="9880"@}
28382 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
28389 @subheading The @code{-target-exec-status} Command
28390 @findex -target-exec-status
28392 @subsubheading Synopsis
28395 -target-exec-status
28398 Provide information on the state of the target (whether it is running or
28399 not, for instance).
28401 @subsubheading @value{GDBN} Command
28403 There's no equivalent @value{GDBN} command.
28405 @subsubheading Example
28409 @subheading The @code{-target-list-available-targets} Command
28410 @findex -target-list-available-targets
28412 @subsubheading Synopsis
28415 -target-list-available-targets
28418 List the possible targets to connect to.
28420 @subsubheading @value{GDBN} Command
28422 The corresponding @value{GDBN} command is @samp{help target}.
28424 @subsubheading Example
28428 @subheading The @code{-target-list-current-targets} Command
28429 @findex -target-list-current-targets
28431 @subsubheading Synopsis
28434 -target-list-current-targets
28437 Describe the current target.
28439 @subsubheading @value{GDBN} Command
28441 The corresponding information is printed by @samp{info file} (among
28444 @subsubheading Example
28448 @subheading The @code{-target-list-parameters} Command
28449 @findex -target-list-parameters
28451 @subsubheading Synopsis
28454 -target-list-parameters
28460 @subsubheading @value{GDBN} Command
28464 @subsubheading Example
28468 @subheading The @code{-target-select} Command
28469 @findex -target-select
28471 @subsubheading Synopsis
28474 -target-select @var{type} @var{parameters @dots{}}
28477 Connect @value{GDBN} to the remote target. This command takes two args:
28481 The type of target, for instance @samp{remote}, etc.
28482 @item @var{parameters}
28483 Device names, host names and the like. @xref{Target Commands, ,
28484 Commands for Managing Targets}, for more details.
28487 The output is a connection notification, followed by the address at
28488 which the target program is, in the following form:
28491 ^connected,addr="@var{address}",func="@var{function name}",
28492 args=[@var{arg list}]
28495 @subsubheading @value{GDBN} Command
28497 The corresponding @value{GDBN} command is @samp{target}.
28499 @subsubheading Example
28503 -target-select remote /dev/ttya
28504 ^connected,addr="0xfe00a300",func="??",args=[]
28508 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28509 @node GDB/MI File Transfer Commands
28510 @section @sc{gdb/mi} File Transfer Commands
28513 @subheading The @code{-target-file-put} Command
28514 @findex -target-file-put
28516 @subsubheading Synopsis
28519 -target-file-put @var{hostfile} @var{targetfile}
28522 Copy file @var{hostfile} from the host system (the machine running
28523 @value{GDBN}) to @var{targetfile} on the target system.
28525 @subsubheading @value{GDBN} Command
28527 The corresponding @value{GDBN} command is @samp{remote put}.
28529 @subsubheading Example
28533 -target-file-put localfile remotefile
28539 @subheading The @code{-target-file-get} Command
28540 @findex -target-file-get
28542 @subsubheading Synopsis
28545 -target-file-get @var{targetfile} @var{hostfile}
28548 Copy file @var{targetfile} from the target system to @var{hostfile}
28549 on the host system.
28551 @subsubheading @value{GDBN} Command
28553 The corresponding @value{GDBN} command is @samp{remote get}.
28555 @subsubheading Example
28559 -target-file-get remotefile localfile
28565 @subheading The @code{-target-file-delete} Command
28566 @findex -target-file-delete
28568 @subsubheading Synopsis
28571 -target-file-delete @var{targetfile}
28574 Delete @var{targetfile} from the target system.
28576 @subsubheading @value{GDBN} Command
28578 The corresponding @value{GDBN} command is @samp{remote delete}.
28580 @subsubheading Example
28584 -target-file-delete remotefile
28590 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28591 @node GDB/MI Miscellaneous Commands
28592 @section Miscellaneous @sc{gdb/mi} Commands
28594 @c @subheading -gdb-complete
28596 @subheading The @code{-gdb-exit} Command
28599 @subsubheading Synopsis
28605 Exit @value{GDBN} immediately.
28607 @subsubheading @value{GDBN} Command
28609 Approximately corresponds to @samp{quit}.
28611 @subsubheading Example
28621 @subheading The @code{-exec-abort} Command
28622 @findex -exec-abort
28624 @subsubheading Synopsis
28630 Kill the inferior running program.
28632 @subsubheading @value{GDBN} Command
28634 The corresponding @value{GDBN} command is @samp{kill}.
28636 @subsubheading Example
28641 @subheading The @code{-gdb-set} Command
28644 @subsubheading Synopsis
28650 Set an internal @value{GDBN} variable.
28651 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
28653 @subsubheading @value{GDBN} Command
28655 The corresponding @value{GDBN} command is @samp{set}.
28657 @subsubheading Example
28667 @subheading The @code{-gdb-show} Command
28670 @subsubheading Synopsis
28676 Show the current value of a @value{GDBN} variable.
28678 @subsubheading @value{GDBN} Command
28680 The corresponding @value{GDBN} command is @samp{show}.
28682 @subsubheading Example
28691 @c @subheading -gdb-source
28694 @subheading The @code{-gdb-version} Command
28695 @findex -gdb-version
28697 @subsubheading Synopsis
28703 Show version information for @value{GDBN}. Used mostly in testing.
28705 @subsubheading @value{GDBN} Command
28707 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
28708 default shows this information when you start an interactive session.
28710 @subsubheading Example
28712 @c This example modifies the actual output from GDB to avoid overfull
28718 ~Copyright 2000 Free Software Foundation, Inc.
28719 ~GDB is free software, covered by the GNU General Public License, and
28720 ~you are welcome to change it and/or distribute copies of it under
28721 ~ certain conditions.
28722 ~Type "show copying" to see the conditions.
28723 ~There is absolutely no warranty for GDB. Type "show warranty" for
28725 ~This GDB was configured as
28726 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
28731 @subheading The @code{-list-features} Command
28732 @findex -list-features
28734 Returns a list of particular features of the MI protocol that
28735 this version of gdb implements. A feature can be a command,
28736 or a new field in an output of some command, or even an
28737 important bugfix. While a frontend can sometimes detect presence
28738 of a feature at runtime, it is easier to perform detection at debugger
28741 The command returns a list of strings, with each string naming an
28742 available feature. Each returned string is just a name, it does not
28743 have any internal structure. The list of possible feature names
28749 (gdb) -list-features
28750 ^done,result=["feature1","feature2"]
28753 The current list of features is:
28756 @item frozen-varobjs
28757 Indicates presence of the @code{-var-set-frozen} command, as well
28758 as possible presense of the @code{frozen} field in the output
28759 of @code{-varobj-create}.
28760 @item pending-breakpoints
28761 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
28763 Indicates presence of Python scripting support, Python-based
28764 pretty-printing commands, and possible presence of the
28765 @samp{display_hint} field in the output of @code{-var-list-children}
28767 Indicates presence of the @code{-thread-info} command.
28771 @subheading The @code{-list-target-features} Command
28772 @findex -list-target-features
28774 Returns a list of particular features that are supported by the
28775 target. Those features affect the permitted MI commands, but
28776 unlike the features reported by the @code{-list-features} command, the
28777 features depend on which target GDB is using at the moment. Whenever
28778 a target can change, due to commands such as @code{-target-select},
28779 @code{-target-attach} or @code{-exec-run}, the list of target features
28780 may change, and the frontend should obtain it again.
28784 (gdb) -list-features
28785 ^done,result=["async"]
28788 The current list of features is:
28792 Indicates that the target is capable of asynchronous command
28793 execution, which means that @value{GDBN} will accept further commands
28794 while the target is running.
28798 @subheading The @code{-list-thread-groups} Command
28799 @findex -list-thread-groups
28801 @subheading Synopsis
28804 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
28807 Lists thread groups (@pxref{Thread groups}). When a single thread
28808 group is passed as the argument, lists the children of that group.
28809 When several thread group are passed, lists information about those
28810 thread groups. Without any parameters, lists information about all
28811 top-level thread groups.
28813 Normally, thread groups that are being debugged are reported.
28814 With the @samp{--available} option, @value{GDBN} reports thread groups
28815 available on the target.
28817 The output of this command may have either a @samp{threads} result or
28818 a @samp{groups} result. The @samp{thread} result has a list of tuples
28819 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
28820 Information}). The @samp{groups} result has a list of tuples as value,
28821 each tuple describing a thread group. If top-level groups are
28822 requested (that is, no parameter is passed), or when several groups
28823 are passed, the output always has a @samp{groups} result. The format
28824 of the @samp{group} result is described below.
28826 To reduce the number of roundtrips it's possible to list thread groups
28827 together with their children, by passing the @samp{--recurse} option
28828 and the recursion depth. Presently, only recursion depth of 1 is
28829 permitted. If this option is present, then every reported thread group
28830 will also include its children, either as @samp{group} or
28831 @samp{threads} field.
28833 In general, any combination of option and parameters is permitted, with
28834 the following caveats:
28838 When a single thread group is passed, the output will typically
28839 be the @samp{threads} result. Because threads may not contain
28840 anything, the @samp{recurse} option will be ignored.
28843 When the @samp{--available} option is passed, limited information may
28844 be available. In particular, the list of threads of a process might
28845 be inaccessible. Further, specifying specific thread groups might
28846 not give any performance advantage over listing all thread groups.
28847 The frontend should assume that @samp{-list-thread-groups --available}
28848 is always an expensive operation and cache the results.
28852 The @samp{groups} result is a list of tuples, where each tuple may
28853 have the following fields:
28857 Identifier of the thread group. This field is always present.
28858 The identifier is an opaque string; frontends should not try to
28859 convert it to an integer, even though it might look like one.
28862 The type of the thread group. At present, only @samp{process} is a
28866 The target-specific process identifier. This field is only present
28867 for thread groups of type @samp{process} and only if the process exists.
28870 The number of children this thread group has. This field may be
28871 absent for an available thread group.
28874 This field has a list of tuples as value, each tuple describing a
28875 thread. It may be present if the @samp{--recurse} option is
28876 specified, and it's actually possible to obtain the threads.
28879 This field is a list of integers, each identifying a core that one
28880 thread of the group is running on. This field may be absent if
28881 such information is not available.
28884 The name of the executable file that corresponds to this thread group.
28885 The field is only present for thread groups of type @samp{process},
28886 and only if there is a corresponding executable file.
28890 @subheading Example
28894 -list-thread-groups
28895 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
28896 -list-thread-groups 17
28897 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28898 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
28899 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28900 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
28901 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
28902 -list-thread-groups --available
28903 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
28904 -list-thread-groups --available --recurse 1
28905 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28906 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28907 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
28908 -list-thread-groups --available --recurse 1 17 18
28909 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28910 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28911 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
28915 @subheading The @code{-add-inferior} Command
28916 @findex -add-inferior
28918 @subheading Synopsis
28924 Creates a new inferior (@pxref{Inferiors and Programs}). The created
28925 inferior is not associated with any executable. Such association may
28926 be established with the @samp{-file-exec-and-symbols} command
28927 (@pxref{GDB/MI File Commands}). The command response has a single
28928 field, @samp{thread-group}, whose value is the identifier of the
28929 thread group corresponding to the new inferior.
28931 @subheading Example
28936 ^done,thread-group="i3"
28939 @subheading The @code{-interpreter-exec} Command
28940 @findex -interpreter-exec
28942 @subheading Synopsis
28945 -interpreter-exec @var{interpreter} @var{command}
28947 @anchor{-interpreter-exec}
28949 Execute the specified @var{command} in the given @var{interpreter}.
28951 @subheading @value{GDBN} Command
28953 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
28955 @subheading Example
28959 -interpreter-exec console "break main"
28960 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
28961 &"During symbol reading, bad structure-type format.\n"
28962 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
28967 @subheading The @code{-inferior-tty-set} Command
28968 @findex -inferior-tty-set
28970 @subheading Synopsis
28973 -inferior-tty-set /dev/pts/1
28976 Set terminal for future runs of the program being debugged.
28978 @subheading @value{GDBN} Command
28980 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
28982 @subheading Example
28986 -inferior-tty-set /dev/pts/1
28991 @subheading The @code{-inferior-tty-show} Command
28992 @findex -inferior-tty-show
28994 @subheading Synopsis
29000 Show terminal for future runs of program being debugged.
29002 @subheading @value{GDBN} Command
29004 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
29006 @subheading Example
29010 -inferior-tty-set /dev/pts/1
29014 ^done,inferior_tty_terminal="/dev/pts/1"
29018 @subheading The @code{-enable-timings} Command
29019 @findex -enable-timings
29021 @subheading Synopsis
29024 -enable-timings [yes | no]
29027 Toggle the printing of the wallclock, user and system times for an MI
29028 command as a field in its output. This command is to help frontend
29029 developers optimize the performance of their code. No argument is
29030 equivalent to @samp{yes}.
29032 @subheading @value{GDBN} Command
29036 @subheading Example
29044 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29045 addr="0x080484ed",func="main",file="myprog.c",
29046 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
29047 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
29055 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29056 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
29057 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
29058 fullname="/home/nickrob/myprog.c",line="73"@}
29063 @chapter @value{GDBN} Annotations
29065 This chapter describes annotations in @value{GDBN}. Annotations were
29066 designed to interface @value{GDBN} to graphical user interfaces or other
29067 similar programs which want to interact with @value{GDBN} at a
29068 relatively high level.
29070 The annotation mechanism has largely been superseded by @sc{gdb/mi}
29074 This is Edition @value{EDITION}, @value{DATE}.
29078 * Annotations Overview:: What annotations are; the general syntax.
29079 * Server Prefix:: Issuing a command without affecting user state.
29080 * Prompting:: Annotations marking @value{GDBN}'s need for input.
29081 * Errors:: Annotations for error messages.
29082 * Invalidation:: Some annotations describe things now invalid.
29083 * Annotations for Running::
29084 Whether the program is running, how it stopped, etc.
29085 * Source Annotations:: Annotations describing source code.
29088 @node Annotations Overview
29089 @section What is an Annotation?
29090 @cindex annotations
29092 Annotations start with a newline character, two @samp{control-z}
29093 characters, and the name of the annotation. If there is no additional
29094 information associated with this annotation, the name of the annotation
29095 is followed immediately by a newline. If there is additional
29096 information, the name of the annotation is followed by a space, the
29097 additional information, and a newline. The additional information
29098 cannot contain newline characters.
29100 Any output not beginning with a newline and two @samp{control-z}
29101 characters denotes literal output from @value{GDBN}. Currently there is
29102 no need for @value{GDBN} to output a newline followed by two
29103 @samp{control-z} characters, but if there was such a need, the
29104 annotations could be extended with an @samp{escape} annotation which
29105 means those three characters as output.
29107 The annotation @var{level}, which is specified using the
29108 @option{--annotate} command line option (@pxref{Mode Options}), controls
29109 how much information @value{GDBN} prints together with its prompt,
29110 values of expressions, source lines, and other types of output. Level 0
29111 is for no annotations, level 1 is for use when @value{GDBN} is run as a
29112 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
29113 for programs that control @value{GDBN}, and level 2 annotations have
29114 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
29115 Interface, annotate, GDB's Obsolete Annotations}).
29118 @kindex set annotate
29119 @item set annotate @var{level}
29120 The @value{GDBN} command @code{set annotate} sets the level of
29121 annotations to the specified @var{level}.
29123 @item show annotate
29124 @kindex show annotate
29125 Show the current annotation level.
29128 This chapter describes level 3 annotations.
29130 A simple example of starting up @value{GDBN} with annotations is:
29133 $ @kbd{gdb --annotate=3}
29135 Copyright 2003 Free Software Foundation, Inc.
29136 GDB is free software, covered by the GNU General Public License,
29137 and you are welcome to change it and/or distribute copies of it
29138 under certain conditions.
29139 Type "show copying" to see the conditions.
29140 There is absolutely no warranty for GDB. Type "show warranty"
29142 This GDB was configured as "i386-pc-linux-gnu"
29153 Here @samp{quit} is input to @value{GDBN}; the rest is output from
29154 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
29155 denotes a @samp{control-z} character) are annotations; the rest is
29156 output from @value{GDBN}.
29158 @node Server Prefix
29159 @section The Server Prefix
29160 @cindex server prefix
29162 If you prefix a command with @samp{server } then it will not affect
29163 the command history, nor will it affect @value{GDBN}'s notion of which
29164 command to repeat if @key{RET} is pressed on a line by itself. This
29165 means that commands can be run behind a user's back by a front-end in
29166 a transparent manner.
29168 The @code{server } prefix does not affect the recording of values into
29169 the value history; to print a value without recording it into the
29170 value history, use the @code{output} command instead of the
29171 @code{print} command.
29173 Using this prefix also disables confirmation requests
29174 (@pxref{confirmation requests}).
29177 @section Annotation for @value{GDBN} Input
29179 @cindex annotations for prompts
29180 When @value{GDBN} prompts for input, it annotates this fact so it is possible
29181 to know when to send output, when the output from a given command is
29184 Different kinds of input each have a different @dfn{input type}. Each
29185 input type has three annotations: a @code{pre-} annotation, which
29186 denotes the beginning of any prompt which is being output, a plain
29187 annotation, which denotes the end of the prompt, and then a @code{post-}
29188 annotation which denotes the end of any echo which may (or may not) be
29189 associated with the input. For example, the @code{prompt} input type
29190 features the following annotations:
29198 The input types are
29201 @findex pre-prompt annotation
29202 @findex prompt annotation
29203 @findex post-prompt annotation
29205 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
29207 @findex pre-commands annotation
29208 @findex commands annotation
29209 @findex post-commands annotation
29211 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
29212 command. The annotations are repeated for each command which is input.
29214 @findex pre-overload-choice annotation
29215 @findex overload-choice annotation
29216 @findex post-overload-choice annotation
29217 @item overload-choice
29218 When @value{GDBN} wants the user to select between various overloaded functions.
29220 @findex pre-query annotation
29221 @findex query annotation
29222 @findex post-query annotation
29224 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
29226 @findex pre-prompt-for-continue annotation
29227 @findex prompt-for-continue annotation
29228 @findex post-prompt-for-continue annotation
29229 @item prompt-for-continue
29230 When @value{GDBN} is asking the user to press return to continue. Note: Don't
29231 expect this to work well; instead use @code{set height 0} to disable
29232 prompting. This is because the counting of lines is buggy in the
29233 presence of annotations.
29238 @cindex annotations for errors, warnings and interrupts
29240 @findex quit annotation
29245 This annotation occurs right before @value{GDBN} responds to an interrupt.
29247 @findex error annotation
29252 This annotation occurs right before @value{GDBN} responds to an error.
29254 Quit and error annotations indicate that any annotations which @value{GDBN} was
29255 in the middle of may end abruptly. For example, if a
29256 @code{value-history-begin} annotation is followed by a @code{error}, one
29257 cannot expect to receive the matching @code{value-history-end}. One
29258 cannot expect not to receive it either, however; an error annotation
29259 does not necessarily mean that @value{GDBN} is immediately returning all the way
29262 @findex error-begin annotation
29263 A quit or error annotation may be preceded by
29269 Any output between that and the quit or error annotation is the error
29272 Warning messages are not yet annotated.
29273 @c If we want to change that, need to fix warning(), type_error(),
29274 @c range_error(), and possibly other places.
29277 @section Invalidation Notices
29279 @cindex annotations for invalidation messages
29280 The following annotations say that certain pieces of state may have
29284 @findex frames-invalid annotation
29285 @item ^Z^Zframes-invalid
29287 The frames (for example, output from the @code{backtrace} command) may
29290 @findex breakpoints-invalid annotation
29291 @item ^Z^Zbreakpoints-invalid
29293 The breakpoints may have changed. For example, the user just added or
29294 deleted a breakpoint.
29297 @node Annotations for Running
29298 @section Running the Program
29299 @cindex annotations for running programs
29301 @findex starting annotation
29302 @findex stopping annotation
29303 When the program starts executing due to a @value{GDBN} command such as
29304 @code{step} or @code{continue},
29310 is output. When the program stops,
29316 is output. Before the @code{stopped} annotation, a variety of
29317 annotations describe how the program stopped.
29320 @findex exited annotation
29321 @item ^Z^Zexited @var{exit-status}
29322 The program exited, and @var{exit-status} is the exit status (zero for
29323 successful exit, otherwise nonzero).
29325 @findex signalled annotation
29326 @findex signal-name annotation
29327 @findex signal-name-end annotation
29328 @findex signal-string annotation
29329 @findex signal-string-end annotation
29330 @item ^Z^Zsignalled
29331 The program exited with a signal. After the @code{^Z^Zsignalled}, the
29332 annotation continues:
29338 ^Z^Zsignal-name-end
29342 ^Z^Zsignal-string-end
29347 where @var{name} is the name of the signal, such as @code{SIGILL} or
29348 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
29349 as @code{Illegal Instruction} or @code{Segmentation fault}.
29350 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
29351 user's benefit and have no particular format.
29353 @findex signal annotation
29355 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
29356 just saying that the program received the signal, not that it was
29357 terminated with it.
29359 @findex breakpoint annotation
29360 @item ^Z^Zbreakpoint @var{number}
29361 The program hit breakpoint number @var{number}.
29363 @findex watchpoint annotation
29364 @item ^Z^Zwatchpoint @var{number}
29365 The program hit watchpoint number @var{number}.
29368 @node Source Annotations
29369 @section Displaying Source
29370 @cindex annotations for source display
29372 @findex source annotation
29373 The following annotation is used instead of displaying source code:
29376 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
29379 where @var{filename} is an absolute file name indicating which source
29380 file, @var{line} is the line number within that file (where 1 is the
29381 first line in the file), @var{character} is the character position
29382 within the file (where 0 is the first character in the file) (for most
29383 debug formats this will necessarily point to the beginning of a line),
29384 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
29385 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
29386 @var{addr} is the address in the target program associated with the
29387 source which is being displayed. @var{addr} is in the form @samp{0x}
29388 followed by one or more lowercase hex digits (note that this does not
29389 depend on the language).
29391 @node JIT Interface
29392 @chapter JIT Compilation Interface
29393 @cindex just-in-time compilation
29394 @cindex JIT compilation interface
29396 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
29397 interface. A JIT compiler is a program or library that generates native
29398 executable code at runtime and executes it, usually in order to achieve good
29399 performance while maintaining platform independence.
29401 Programs that use JIT compilation are normally difficult to debug because
29402 portions of their code are generated at runtime, instead of being loaded from
29403 object files, which is where @value{GDBN} normally finds the program's symbols
29404 and debug information. In order to debug programs that use JIT compilation,
29405 @value{GDBN} has an interface that allows the program to register in-memory
29406 symbol files with @value{GDBN} at runtime.
29408 If you are using @value{GDBN} to debug a program that uses this interface, then
29409 it should work transparently so long as you have not stripped the binary. If
29410 you are developing a JIT compiler, then the interface is documented in the rest
29411 of this chapter. At this time, the only known client of this interface is the
29414 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
29415 JIT compiler communicates with @value{GDBN} by writing data into a global
29416 variable and calling a fuction at a well-known symbol. When @value{GDBN}
29417 attaches, it reads a linked list of symbol files from the global variable to
29418 find existing code, and puts a breakpoint in the function so that it can find
29419 out about additional code.
29422 * Declarations:: Relevant C struct declarations
29423 * Registering Code:: Steps to register code
29424 * Unregistering Code:: Steps to unregister code
29428 @section JIT Declarations
29430 These are the relevant struct declarations that a C program should include to
29431 implement the interface:
29441 struct jit_code_entry
29443 struct jit_code_entry *next_entry;
29444 struct jit_code_entry *prev_entry;
29445 const char *symfile_addr;
29446 uint64_t symfile_size;
29449 struct jit_descriptor
29452 /* This type should be jit_actions_t, but we use uint32_t
29453 to be explicit about the bitwidth. */
29454 uint32_t action_flag;
29455 struct jit_code_entry *relevant_entry;
29456 struct jit_code_entry *first_entry;
29459 /* GDB puts a breakpoint in this function. */
29460 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
29462 /* Make sure to specify the version statically, because the
29463 debugger may check the version before we can set it. */
29464 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
29467 If the JIT is multi-threaded, then it is important that the JIT synchronize any
29468 modifications to this global data properly, which can easily be done by putting
29469 a global mutex around modifications to these structures.
29471 @node Registering Code
29472 @section Registering Code
29474 To register code with @value{GDBN}, the JIT should follow this protocol:
29478 Generate an object file in memory with symbols and other desired debug
29479 information. The file must include the virtual addresses of the sections.
29482 Create a code entry for the file, which gives the start and size of the symbol
29486 Add it to the linked list in the JIT descriptor.
29489 Point the relevant_entry field of the descriptor at the entry.
29492 Set @code{action_flag} to @code{JIT_REGISTER} and call
29493 @code{__jit_debug_register_code}.
29496 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
29497 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
29498 new code. However, the linked list must still be maintained in order to allow
29499 @value{GDBN} to attach to a running process and still find the symbol files.
29501 @node Unregistering Code
29502 @section Unregistering Code
29504 If code is freed, then the JIT should use the following protocol:
29508 Remove the code entry corresponding to the code from the linked list.
29511 Point the @code{relevant_entry} field of the descriptor at the code entry.
29514 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
29515 @code{__jit_debug_register_code}.
29518 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
29519 and the JIT will leak the memory used for the associated symbol files.
29522 @chapter Reporting Bugs in @value{GDBN}
29523 @cindex bugs in @value{GDBN}
29524 @cindex reporting bugs in @value{GDBN}
29526 Your bug reports play an essential role in making @value{GDBN} reliable.
29528 Reporting a bug may help you by bringing a solution to your problem, or it
29529 may not. But in any case the principal function of a bug report is to help
29530 the entire community by making the next version of @value{GDBN} work better. Bug
29531 reports are your contribution to the maintenance of @value{GDBN}.
29533 In order for a bug report to serve its purpose, you must include the
29534 information that enables us to fix the bug.
29537 * Bug Criteria:: Have you found a bug?
29538 * Bug Reporting:: How to report bugs
29542 @section Have You Found a Bug?
29543 @cindex bug criteria
29545 If you are not sure whether you have found a bug, here are some guidelines:
29548 @cindex fatal signal
29549 @cindex debugger crash
29550 @cindex crash of debugger
29552 If the debugger gets a fatal signal, for any input whatever, that is a
29553 @value{GDBN} bug. Reliable debuggers never crash.
29555 @cindex error on valid input
29557 If @value{GDBN} produces an error message for valid input, that is a
29558 bug. (Note that if you're cross debugging, the problem may also be
29559 somewhere in the connection to the target.)
29561 @cindex invalid input
29563 If @value{GDBN} does not produce an error message for invalid input,
29564 that is a bug. However, you should note that your idea of
29565 ``invalid input'' might be our idea of ``an extension'' or ``support
29566 for traditional practice''.
29569 If you are an experienced user of debugging tools, your suggestions
29570 for improvement of @value{GDBN} are welcome in any case.
29573 @node Bug Reporting
29574 @section How to Report Bugs
29575 @cindex bug reports
29576 @cindex @value{GDBN} bugs, reporting
29578 A number of companies and individuals offer support for @sc{gnu} products.
29579 If you obtained @value{GDBN} from a support organization, we recommend you
29580 contact that organization first.
29582 You can find contact information for many support companies and
29583 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
29585 @c should add a web page ref...
29588 @ifset BUGURL_DEFAULT
29589 In any event, we also recommend that you submit bug reports for
29590 @value{GDBN}. The preferred method is to submit them directly using
29591 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
29592 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
29595 @strong{Do not send bug reports to @samp{info-gdb}, or to
29596 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
29597 not want to receive bug reports. Those that do have arranged to receive
29600 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
29601 serves as a repeater. The mailing list and the newsgroup carry exactly
29602 the same messages. Often people think of posting bug reports to the
29603 newsgroup instead of mailing them. This appears to work, but it has one
29604 problem which can be crucial: a newsgroup posting often lacks a mail
29605 path back to the sender. Thus, if we need to ask for more information,
29606 we may be unable to reach you. For this reason, it is better to send
29607 bug reports to the mailing list.
29609 @ifclear BUGURL_DEFAULT
29610 In any event, we also recommend that you submit bug reports for
29611 @value{GDBN} to @value{BUGURL}.
29615 The fundamental principle of reporting bugs usefully is this:
29616 @strong{report all the facts}. If you are not sure whether to state a
29617 fact or leave it out, state it!
29619 Often people omit facts because they think they know what causes the
29620 problem and assume that some details do not matter. Thus, you might
29621 assume that the name of the variable you use in an example does not matter.
29622 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
29623 stray memory reference which happens to fetch from the location where that
29624 name is stored in memory; perhaps, if the name were different, the contents
29625 of that location would fool the debugger into doing the right thing despite
29626 the bug. Play it safe and give a specific, complete example. That is the
29627 easiest thing for you to do, and the most helpful.
29629 Keep in mind that the purpose of a bug report is to enable us to fix the
29630 bug. It may be that the bug has been reported previously, but neither
29631 you nor we can know that unless your bug report is complete and
29634 Sometimes people give a few sketchy facts and ask, ``Does this ring a
29635 bell?'' Those bug reports are useless, and we urge everyone to
29636 @emph{refuse to respond to them} except to chide the sender to report
29639 To enable us to fix the bug, you should include all these things:
29643 The version of @value{GDBN}. @value{GDBN} announces it if you start
29644 with no arguments; you can also print it at any time using @code{show
29647 Without this, we will not know whether there is any point in looking for
29648 the bug in the current version of @value{GDBN}.
29651 The type of machine you are using, and the operating system name and
29655 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
29656 ``@value{GCC}--2.8.1''.
29659 What compiler (and its version) was used to compile the program you are
29660 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
29661 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
29662 to get this information; for other compilers, see the documentation for
29666 The command arguments you gave the compiler to compile your example and
29667 observe the bug. For example, did you use @samp{-O}? To guarantee
29668 you will not omit something important, list them all. A copy of the
29669 Makefile (or the output from make) is sufficient.
29671 If we were to try to guess the arguments, we would probably guess wrong
29672 and then we might not encounter the bug.
29675 A complete input script, and all necessary source files, that will
29679 A description of what behavior you observe that you believe is
29680 incorrect. For example, ``It gets a fatal signal.''
29682 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
29683 will certainly notice it. But if the bug is incorrect output, we might
29684 not notice unless it is glaringly wrong. You might as well not give us
29685 a chance to make a mistake.
29687 Even if the problem you experience is a fatal signal, you should still
29688 say so explicitly. Suppose something strange is going on, such as, your
29689 copy of @value{GDBN} is out of synch, or you have encountered a bug in
29690 the C library on your system. (This has happened!) Your copy might
29691 crash and ours would not. If you told us to expect a crash, then when
29692 ours fails to crash, we would know that the bug was not happening for
29693 us. If you had not told us to expect a crash, then we would not be able
29694 to draw any conclusion from our observations.
29697 @cindex recording a session script
29698 To collect all this information, you can use a session recording program
29699 such as @command{script}, which is available on many Unix systems.
29700 Just run your @value{GDBN} session inside @command{script} and then
29701 include the @file{typescript} file with your bug report.
29703 Another way to record a @value{GDBN} session is to run @value{GDBN}
29704 inside Emacs and then save the entire buffer to a file.
29707 If you wish to suggest changes to the @value{GDBN} source, send us context
29708 diffs. If you even discuss something in the @value{GDBN} source, refer to
29709 it by context, not by line number.
29711 The line numbers in our development sources will not match those in your
29712 sources. Your line numbers would convey no useful information to us.
29716 Here are some things that are not necessary:
29720 A description of the envelope of the bug.
29722 Often people who encounter a bug spend a lot of time investigating
29723 which changes to the input file will make the bug go away and which
29724 changes will not affect it.
29726 This is often time consuming and not very useful, because the way we
29727 will find the bug is by running a single example under the debugger
29728 with breakpoints, not by pure deduction from a series of examples.
29729 We recommend that you save your time for something else.
29731 Of course, if you can find a simpler example to report @emph{instead}
29732 of the original one, that is a convenience for us. Errors in the
29733 output will be easier to spot, running under the debugger will take
29734 less time, and so on.
29736 However, simplification is not vital; if you do not want to do this,
29737 report the bug anyway and send us the entire test case you used.
29740 A patch for the bug.
29742 A patch for the bug does help us if it is a good one. But do not omit
29743 the necessary information, such as the test case, on the assumption that
29744 a patch is all we need. We might see problems with your patch and decide
29745 to fix the problem another way, or we might not understand it at all.
29747 Sometimes with a program as complicated as @value{GDBN} it is very hard to
29748 construct an example that will make the program follow a certain path
29749 through the code. If you do not send us the example, we will not be able
29750 to construct one, so we will not be able to verify that the bug is fixed.
29752 And if we cannot understand what bug you are trying to fix, or why your
29753 patch should be an improvement, we will not install it. A test case will
29754 help us to understand.
29757 A guess about what the bug is or what it depends on.
29759 Such guesses are usually wrong. Even we cannot guess right about such
29760 things without first using the debugger to find the facts.
29763 @c The readline documentation is distributed with the readline code
29764 @c and consists of the two following files:
29766 @c inc-hist.texinfo
29767 @c Use -I with makeinfo to point to the appropriate directory,
29768 @c environment var TEXINPUTS with TeX.
29769 @include rluser.texi
29770 @include inc-hist.texinfo
29773 @node Formatting Documentation
29774 @appendix Formatting Documentation
29776 @cindex @value{GDBN} reference card
29777 @cindex reference card
29778 The @value{GDBN} 4 release includes an already-formatted reference card, ready
29779 for printing with PostScript or Ghostscript, in the @file{gdb}
29780 subdirectory of the main source directory@footnote{In
29781 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
29782 release.}. If you can use PostScript or Ghostscript with your printer,
29783 you can print the reference card immediately with @file{refcard.ps}.
29785 The release also includes the source for the reference card. You
29786 can format it, using @TeX{}, by typing:
29792 The @value{GDBN} reference card is designed to print in @dfn{landscape}
29793 mode on US ``letter'' size paper;
29794 that is, on a sheet 11 inches wide by 8.5 inches
29795 high. You will need to specify this form of printing as an option to
29796 your @sc{dvi} output program.
29798 @cindex documentation
29800 All the documentation for @value{GDBN} comes as part of the machine-readable
29801 distribution. The documentation is written in Texinfo format, which is
29802 a documentation system that uses a single source file to produce both
29803 on-line information and a printed manual. You can use one of the Info
29804 formatting commands to create the on-line version of the documentation
29805 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
29807 @value{GDBN} includes an already formatted copy of the on-line Info
29808 version of this manual in the @file{gdb} subdirectory. The main Info
29809 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
29810 subordinate files matching @samp{gdb.info*} in the same directory. If
29811 necessary, you can print out these files, or read them with any editor;
29812 but they are easier to read using the @code{info} subsystem in @sc{gnu}
29813 Emacs or the standalone @code{info} program, available as part of the
29814 @sc{gnu} Texinfo distribution.
29816 If you want to format these Info files yourself, you need one of the
29817 Info formatting programs, such as @code{texinfo-format-buffer} or
29820 If you have @code{makeinfo} installed, and are in the top level
29821 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
29822 version @value{GDBVN}), you can make the Info file by typing:
29829 If you want to typeset and print copies of this manual, you need @TeX{},
29830 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
29831 Texinfo definitions file.
29833 @TeX{} is a typesetting program; it does not print files directly, but
29834 produces output files called @sc{dvi} files. To print a typeset
29835 document, you need a program to print @sc{dvi} files. If your system
29836 has @TeX{} installed, chances are it has such a program. The precise
29837 command to use depends on your system; @kbd{lpr -d} is common; another
29838 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
29839 require a file name without any extension or a @samp{.dvi} extension.
29841 @TeX{} also requires a macro definitions file called
29842 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
29843 written in Texinfo format. On its own, @TeX{} cannot either read or
29844 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
29845 and is located in the @file{gdb-@var{version-number}/texinfo}
29848 If you have @TeX{} and a @sc{dvi} printer program installed, you can
29849 typeset and print this manual. First switch to the @file{gdb}
29850 subdirectory of the main source directory (for example, to
29851 @file{gdb-@value{GDBVN}/gdb}) and type:
29857 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
29859 @node Installing GDB
29860 @appendix Installing @value{GDBN}
29861 @cindex installation
29864 * Requirements:: Requirements for building @value{GDBN}
29865 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
29866 * Separate Objdir:: Compiling @value{GDBN} in another directory
29867 * Config Names:: Specifying names for hosts and targets
29868 * Configure Options:: Summary of options for configure
29869 * System-wide configuration:: Having a system-wide init file
29873 @section Requirements for Building @value{GDBN}
29874 @cindex building @value{GDBN}, requirements for
29876 Building @value{GDBN} requires various tools and packages to be available.
29877 Other packages will be used only if they are found.
29879 @heading Tools/Packages Necessary for Building @value{GDBN}
29881 @item ISO C90 compiler
29882 @value{GDBN} is written in ISO C90. It should be buildable with any
29883 working C90 compiler, e.g.@: GCC.
29887 @heading Tools/Packages Optional for Building @value{GDBN}
29891 @value{GDBN} can use the Expat XML parsing library. This library may be
29892 included with your operating system distribution; if it is not, you
29893 can get the latest version from @url{http://expat.sourceforge.net}.
29894 The @file{configure} script will search for this library in several
29895 standard locations; if it is installed in an unusual path, you can
29896 use the @option{--with-libexpat-prefix} option to specify its location.
29902 Remote protocol memory maps (@pxref{Memory Map Format})
29904 Target descriptions (@pxref{Target Descriptions})
29906 Remote shared library lists (@pxref{Library List Format})
29908 MS-Windows shared libraries (@pxref{Shared Libraries})
29912 @cindex compressed debug sections
29913 @value{GDBN} will use the @samp{zlib} library, if available, to read
29914 compressed debug sections. Some linkers, such as GNU gold, are capable
29915 of producing binaries with compressed debug sections. If @value{GDBN}
29916 is compiled with @samp{zlib}, it will be able to read the debug
29917 information in such binaries.
29919 The @samp{zlib} library is likely included with your operating system
29920 distribution; if it is not, you can get the latest version from
29921 @url{http://zlib.net}.
29924 @value{GDBN}'s features related to character sets (@pxref{Character
29925 Sets}) require a functioning @code{iconv} implementation. If you are
29926 on a GNU system, then this is provided by the GNU C Library. Some
29927 other systems also provide a working @code{iconv}.
29929 On systems with @code{iconv}, you can install GNU Libiconv. If you
29930 have previously installed Libiconv, you can use the
29931 @option{--with-libiconv-prefix} option to configure.
29933 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
29934 arrange to build Libiconv if a directory named @file{libiconv} appears
29935 in the top-most source directory. If Libiconv is built this way, and
29936 if the operating system does not provide a suitable @code{iconv}
29937 implementation, then the just-built library will automatically be used
29938 by @value{GDBN}. One easy way to set this up is to download GNU
29939 Libiconv, unpack it, and then rename the directory holding the
29940 Libiconv source code to @samp{libiconv}.
29943 @node Running Configure
29944 @section Invoking the @value{GDBN} @file{configure} Script
29945 @cindex configuring @value{GDBN}
29946 @value{GDBN} comes with a @file{configure} script that automates the process
29947 of preparing @value{GDBN} for installation; you can then use @code{make} to
29948 build the @code{gdb} program.
29950 @c irrelevant in info file; it's as current as the code it lives with.
29951 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
29952 look at the @file{README} file in the sources; we may have improved the
29953 installation procedures since publishing this manual.}
29956 The @value{GDBN} distribution includes all the source code you need for
29957 @value{GDBN} in a single directory, whose name is usually composed by
29958 appending the version number to @samp{gdb}.
29960 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
29961 @file{gdb-@value{GDBVN}} directory. That directory contains:
29964 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
29965 script for configuring @value{GDBN} and all its supporting libraries
29967 @item gdb-@value{GDBVN}/gdb
29968 the source specific to @value{GDBN} itself
29970 @item gdb-@value{GDBVN}/bfd
29971 source for the Binary File Descriptor library
29973 @item gdb-@value{GDBVN}/include
29974 @sc{gnu} include files
29976 @item gdb-@value{GDBVN}/libiberty
29977 source for the @samp{-liberty} free software library
29979 @item gdb-@value{GDBVN}/opcodes
29980 source for the library of opcode tables and disassemblers
29982 @item gdb-@value{GDBVN}/readline
29983 source for the @sc{gnu} command-line interface
29985 @item gdb-@value{GDBVN}/glob
29986 source for the @sc{gnu} filename pattern-matching subroutine
29988 @item gdb-@value{GDBVN}/mmalloc
29989 source for the @sc{gnu} memory-mapped malloc package
29992 The simplest way to configure and build @value{GDBN} is to run @file{configure}
29993 from the @file{gdb-@var{version-number}} source directory, which in
29994 this example is the @file{gdb-@value{GDBVN}} directory.
29996 First switch to the @file{gdb-@var{version-number}} source directory
29997 if you are not already in it; then run @file{configure}. Pass the
29998 identifier for the platform on which @value{GDBN} will run as an
30004 cd gdb-@value{GDBVN}
30005 ./configure @var{host}
30010 where @var{host} is an identifier such as @samp{sun4} or
30011 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
30012 (You can often leave off @var{host}; @file{configure} tries to guess the
30013 correct value by examining your system.)
30015 Running @samp{configure @var{host}} and then running @code{make} builds the
30016 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
30017 libraries, then @code{gdb} itself. The configured source files, and the
30018 binaries, are left in the corresponding source directories.
30021 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
30022 system does not recognize this automatically when you run a different
30023 shell, you may need to run @code{sh} on it explicitly:
30026 sh configure @var{host}
30029 If you run @file{configure} from a directory that contains source
30030 directories for multiple libraries or programs, such as the
30031 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
30033 creates configuration files for every directory level underneath (unless
30034 you tell it not to, with the @samp{--norecursion} option).
30036 You should run the @file{configure} script from the top directory in the
30037 source tree, the @file{gdb-@var{version-number}} directory. If you run
30038 @file{configure} from one of the subdirectories, you will configure only
30039 that subdirectory. That is usually not what you want. In particular,
30040 if you run the first @file{configure} from the @file{gdb} subdirectory
30041 of the @file{gdb-@var{version-number}} directory, you will omit the
30042 configuration of @file{bfd}, @file{readline}, and other sibling
30043 directories of the @file{gdb} subdirectory. This leads to build errors
30044 about missing include files such as @file{bfd/bfd.h}.
30046 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
30047 However, you should make sure that the shell on your path (named by
30048 the @samp{SHELL} environment variable) is publicly readable. Remember
30049 that @value{GDBN} uses the shell to start your program---some systems refuse to
30050 let @value{GDBN} debug child processes whose programs are not readable.
30052 @node Separate Objdir
30053 @section Compiling @value{GDBN} in Another Directory
30055 If you want to run @value{GDBN} versions for several host or target machines,
30056 you need a different @code{gdb} compiled for each combination of
30057 host and target. @file{configure} is designed to make this easy by
30058 allowing you to generate each configuration in a separate subdirectory,
30059 rather than in the source directory. If your @code{make} program
30060 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
30061 @code{make} in each of these directories builds the @code{gdb}
30062 program specified there.
30064 To build @code{gdb} in a separate directory, run @file{configure}
30065 with the @samp{--srcdir} option to specify where to find the source.
30066 (You also need to specify a path to find @file{configure}
30067 itself from your working directory. If the path to @file{configure}
30068 would be the same as the argument to @samp{--srcdir}, you can leave out
30069 the @samp{--srcdir} option; it is assumed.)
30071 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
30072 separate directory for a Sun 4 like this:
30076 cd gdb-@value{GDBVN}
30079 ../gdb-@value{GDBVN}/configure sun4
30084 When @file{configure} builds a configuration using a remote source
30085 directory, it creates a tree for the binaries with the same structure
30086 (and using the same names) as the tree under the source directory. In
30087 the example, you'd find the Sun 4 library @file{libiberty.a} in the
30088 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
30089 @file{gdb-sun4/gdb}.
30091 Make sure that your path to the @file{configure} script has just one
30092 instance of @file{gdb} in it. If your path to @file{configure} looks
30093 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
30094 one subdirectory of @value{GDBN}, not the whole package. This leads to
30095 build errors about missing include files such as @file{bfd/bfd.h}.
30097 One popular reason to build several @value{GDBN} configurations in separate
30098 directories is to configure @value{GDBN} for cross-compiling (where
30099 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
30100 programs that run on another machine---the @dfn{target}).
30101 You specify a cross-debugging target by
30102 giving the @samp{--target=@var{target}} option to @file{configure}.
30104 When you run @code{make} to build a program or library, you must run
30105 it in a configured directory---whatever directory you were in when you
30106 called @file{configure} (or one of its subdirectories).
30108 The @code{Makefile} that @file{configure} generates in each source
30109 directory also runs recursively. If you type @code{make} in a source
30110 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
30111 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
30112 will build all the required libraries, and then build GDB.
30114 When you have multiple hosts or targets configured in separate
30115 directories, you can run @code{make} on them in parallel (for example,
30116 if they are NFS-mounted on each of the hosts); they will not interfere
30120 @section Specifying Names for Hosts and Targets
30122 The specifications used for hosts and targets in the @file{configure}
30123 script are based on a three-part naming scheme, but some short predefined
30124 aliases are also supported. The full naming scheme encodes three pieces
30125 of information in the following pattern:
30128 @var{architecture}-@var{vendor}-@var{os}
30131 For example, you can use the alias @code{sun4} as a @var{host} argument,
30132 or as the value for @var{target} in a @code{--target=@var{target}}
30133 option. The equivalent full name is @samp{sparc-sun-sunos4}.
30135 The @file{configure} script accompanying @value{GDBN} does not provide
30136 any query facility to list all supported host and target names or
30137 aliases. @file{configure} calls the Bourne shell script
30138 @code{config.sub} to map abbreviations to full names; you can read the
30139 script, if you wish, or you can use it to test your guesses on
30140 abbreviations---for example:
30143 % sh config.sub i386-linux
30145 % sh config.sub alpha-linux
30146 alpha-unknown-linux-gnu
30147 % sh config.sub hp9k700
30149 % sh config.sub sun4
30150 sparc-sun-sunos4.1.1
30151 % sh config.sub sun3
30152 m68k-sun-sunos4.1.1
30153 % sh config.sub i986v
30154 Invalid configuration `i986v': machine `i986v' not recognized
30158 @code{config.sub} is also distributed in the @value{GDBN} source
30159 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
30161 @node Configure Options
30162 @section @file{configure} Options
30164 Here is a summary of the @file{configure} options and arguments that
30165 are most often useful for building @value{GDBN}. @file{configure} also has
30166 several other options not listed here. @inforef{What Configure
30167 Does,,configure.info}, for a full explanation of @file{configure}.
30170 configure @r{[}--help@r{]}
30171 @r{[}--prefix=@var{dir}@r{]}
30172 @r{[}--exec-prefix=@var{dir}@r{]}
30173 @r{[}--srcdir=@var{dirname}@r{]}
30174 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
30175 @r{[}--target=@var{target}@r{]}
30180 You may introduce options with a single @samp{-} rather than
30181 @samp{--} if you prefer; but you may abbreviate option names if you use
30186 Display a quick summary of how to invoke @file{configure}.
30188 @item --prefix=@var{dir}
30189 Configure the source to install programs and files under directory
30192 @item --exec-prefix=@var{dir}
30193 Configure the source to install programs under directory
30196 @c avoid splitting the warning from the explanation:
30198 @item --srcdir=@var{dirname}
30199 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
30200 @code{make} that implements the @code{VPATH} feature.}@*
30201 Use this option to make configurations in directories separate from the
30202 @value{GDBN} source directories. Among other things, you can use this to
30203 build (or maintain) several configurations simultaneously, in separate
30204 directories. @file{configure} writes configuration-specific files in
30205 the current directory, but arranges for them to use the source in the
30206 directory @var{dirname}. @file{configure} creates directories under
30207 the working directory in parallel to the source directories below
30210 @item --norecursion
30211 Configure only the directory level where @file{configure} is executed; do not
30212 propagate configuration to subdirectories.
30214 @item --target=@var{target}
30215 Configure @value{GDBN} for cross-debugging programs running on the specified
30216 @var{target}. Without this option, @value{GDBN} is configured to debug
30217 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
30219 There is no convenient way to generate a list of all available targets.
30221 @item @var{host} @dots{}
30222 Configure @value{GDBN} to run on the specified @var{host}.
30224 There is no convenient way to generate a list of all available hosts.
30227 There are many other options available as well, but they are generally
30228 needed for special purposes only.
30230 @node System-wide configuration
30231 @section System-wide configuration and settings
30232 @cindex system-wide init file
30234 @value{GDBN} can be configured to have a system-wide init file;
30235 this file will be read and executed at startup (@pxref{Startup, , What
30236 @value{GDBN} does during startup}).
30238 Here is the corresponding configure option:
30241 @item --with-system-gdbinit=@var{file}
30242 Specify that the default location of the system-wide init file is
30246 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
30247 it may be subject to relocation. Two possible cases:
30251 If the default location of this init file contains @file{$prefix},
30252 it will be subject to relocation. Suppose that the configure options
30253 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
30254 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
30255 init file is looked for as @file{$install/etc/gdbinit} instead of
30256 @file{$prefix/etc/gdbinit}.
30259 By contrast, if the default location does not contain the prefix,
30260 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
30261 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
30262 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
30263 wherever @value{GDBN} is installed.
30266 @node Maintenance Commands
30267 @appendix Maintenance Commands
30268 @cindex maintenance commands
30269 @cindex internal commands
30271 In addition to commands intended for @value{GDBN} users, @value{GDBN}
30272 includes a number of commands intended for @value{GDBN} developers,
30273 that are not documented elsewhere in this manual. These commands are
30274 provided here for reference. (For commands that turn on debugging
30275 messages, see @ref{Debugging Output}.)
30278 @kindex maint agent
30279 @kindex maint agent-eval
30280 @item maint agent @var{expression}
30281 @itemx maint agent-eval @var{expression}
30282 Translate the given @var{expression} into remote agent bytecodes.
30283 This command is useful for debugging the Agent Expression mechanism
30284 (@pxref{Agent Expressions}). The @samp{agent} version produces an
30285 expression useful for data collection, such as by tracepoints, while
30286 @samp{maint agent-eval} produces an expression that evaluates directly
30287 to a result. For instance, a collection expression for @code{globa +
30288 globb} will include bytecodes to record four bytes of memory at each
30289 of the addresses of @code{globa} and @code{globb}, while discarding
30290 the result of the addition, while an evaluation expression will do the
30291 addition and return the sum.
30293 @kindex maint info breakpoints
30294 @item @anchor{maint info breakpoints}maint info breakpoints
30295 Using the same format as @samp{info breakpoints}, display both the
30296 breakpoints you've set explicitly, and those @value{GDBN} is using for
30297 internal purposes. Internal breakpoints are shown with negative
30298 breakpoint numbers. The type column identifies what kind of breakpoint
30303 Normal, explicitly set breakpoint.
30306 Normal, explicitly set watchpoint.
30309 Internal breakpoint, used to handle correctly stepping through
30310 @code{longjmp} calls.
30312 @item longjmp resume
30313 Internal breakpoint at the target of a @code{longjmp}.
30316 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
30319 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
30322 Shared library events.
30326 @kindex set displaced-stepping
30327 @kindex show displaced-stepping
30328 @cindex displaced stepping support
30329 @cindex out-of-line single-stepping
30330 @item set displaced-stepping
30331 @itemx show displaced-stepping
30332 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
30333 if the target supports it. Displaced stepping is a way to single-step
30334 over breakpoints without removing them from the inferior, by executing
30335 an out-of-line copy of the instruction that was originally at the
30336 breakpoint location. It is also known as out-of-line single-stepping.
30339 @item set displaced-stepping on
30340 If the target architecture supports it, @value{GDBN} will use
30341 displaced stepping to step over breakpoints.
30343 @item set displaced-stepping off
30344 @value{GDBN} will not use displaced stepping to step over breakpoints,
30345 even if such is supported by the target architecture.
30347 @cindex non-stop mode, and @samp{set displaced-stepping}
30348 @item set displaced-stepping auto
30349 This is the default mode. @value{GDBN} will use displaced stepping
30350 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
30351 architecture supports displaced stepping.
30354 @kindex maint check-symtabs
30355 @item maint check-symtabs
30356 Check the consistency of psymtabs and symtabs.
30358 @kindex maint cplus first_component
30359 @item maint cplus first_component @var{name}
30360 Print the first C@t{++} class/namespace component of @var{name}.
30362 @kindex maint cplus namespace
30363 @item maint cplus namespace
30364 Print the list of possible C@t{++} namespaces.
30366 @kindex maint demangle
30367 @item maint demangle @var{name}
30368 Demangle a C@t{++} or Objective-C mangled @var{name}.
30370 @kindex maint deprecate
30371 @kindex maint undeprecate
30372 @cindex deprecated commands
30373 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
30374 @itemx maint undeprecate @var{command}
30375 Deprecate or undeprecate the named @var{command}. Deprecated commands
30376 cause @value{GDBN} to issue a warning when you use them. The optional
30377 argument @var{replacement} says which newer command should be used in
30378 favor of the deprecated one; if it is given, @value{GDBN} will mention
30379 the replacement as part of the warning.
30381 @kindex maint dump-me
30382 @item maint dump-me
30383 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
30384 Cause a fatal signal in the debugger and force it to dump its core.
30385 This is supported only on systems which support aborting a program
30386 with the @code{SIGQUIT} signal.
30388 @kindex maint internal-error
30389 @kindex maint internal-warning
30390 @item maint internal-error @r{[}@var{message-text}@r{]}
30391 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
30392 Cause @value{GDBN} to call the internal function @code{internal_error}
30393 or @code{internal_warning} and hence behave as though an internal error
30394 or internal warning has been detected. In addition to reporting the
30395 internal problem, these functions give the user the opportunity to
30396 either quit @value{GDBN} or create a core file of the current
30397 @value{GDBN} session.
30399 These commands take an optional parameter @var{message-text} that is
30400 used as the text of the error or warning message.
30402 Here's an example of using @code{internal-error}:
30405 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
30406 @dots{}/maint.c:121: internal-error: testing, 1, 2
30407 A problem internal to GDB has been detected. Further
30408 debugging may prove unreliable.
30409 Quit this debugging session? (y or n) @kbd{n}
30410 Create a core file? (y or n) @kbd{n}
30414 @cindex @value{GDBN} internal error
30415 @cindex internal errors, control of @value{GDBN} behavior
30417 @kindex maint set internal-error
30418 @kindex maint show internal-error
30419 @kindex maint set internal-warning
30420 @kindex maint show internal-warning
30421 @item maint set internal-error @var{action} [ask|yes|no]
30422 @itemx maint show internal-error @var{action}
30423 @itemx maint set internal-warning @var{action} [ask|yes|no]
30424 @itemx maint show internal-warning @var{action}
30425 When @value{GDBN} reports an internal problem (error or warning) it
30426 gives the user the opportunity to both quit @value{GDBN} and create a
30427 core file of the current @value{GDBN} session. These commands let you
30428 override the default behaviour for each particular @var{action},
30429 described in the table below.
30433 You can specify that @value{GDBN} should always (yes) or never (no)
30434 quit. The default is to ask the user what to do.
30437 You can specify that @value{GDBN} should always (yes) or never (no)
30438 create a core file. The default is to ask the user what to do.
30441 @kindex maint packet
30442 @item maint packet @var{text}
30443 If @value{GDBN} is talking to an inferior via the serial protocol,
30444 then this command sends the string @var{text} to the inferior, and
30445 displays the response packet. @value{GDBN} supplies the initial
30446 @samp{$} character, the terminating @samp{#} character, and the
30449 @kindex maint print architecture
30450 @item maint print architecture @r{[}@var{file}@r{]}
30451 Print the entire architecture configuration. The optional argument
30452 @var{file} names the file where the output goes.
30454 @kindex maint print c-tdesc
30455 @item maint print c-tdesc
30456 Print the current target description (@pxref{Target Descriptions}) as
30457 a C source file. The created source file can be used in @value{GDBN}
30458 when an XML parser is not available to parse the description.
30460 @kindex maint print dummy-frames
30461 @item maint print dummy-frames
30462 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
30465 (@value{GDBP}) @kbd{b add}
30467 (@value{GDBP}) @kbd{print add(2,3)}
30468 Breakpoint 2, add (a=2, b=3) at @dots{}
30470 The program being debugged stopped while in a function called from GDB.
30472 (@value{GDBP}) @kbd{maint print dummy-frames}
30473 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
30474 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
30475 call_lo=0x01014000 call_hi=0x01014001
30479 Takes an optional file parameter.
30481 @kindex maint print registers
30482 @kindex maint print raw-registers
30483 @kindex maint print cooked-registers
30484 @kindex maint print register-groups
30485 @item maint print registers @r{[}@var{file}@r{]}
30486 @itemx maint print raw-registers @r{[}@var{file}@r{]}
30487 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
30488 @itemx maint print register-groups @r{[}@var{file}@r{]}
30489 Print @value{GDBN}'s internal register data structures.
30491 The command @code{maint print raw-registers} includes the contents of
30492 the raw register cache; the command @code{maint print cooked-registers}
30493 includes the (cooked) value of all registers, including registers which
30494 aren't available on the target nor visible to user; and the
30495 command @code{maint print register-groups} includes the groups that each
30496 register is a member of. @xref{Registers,, Registers, gdbint,
30497 @value{GDBN} Internals}.
30499 These commands take an optional parameter, a file name to which to
30500 write the information.
30502 @kindex maint print reggroups
30503 @item maint print reggroups @r{[}@var{file}@r{]}
30504 Print @value{GDBN}'s internal register group data structures. The
30505 optional argument @var{file} tells to what file to write the
30508 The register groups info looks like this:
30511 (@value{GDBP}) @kbd{maint print reggroups}
30524 This command forces @value{GDBN} to flush its internal register cache.
30526 @kindex maint print objfiles
30527 @cindex info for known object files
30528 @item maint print objfiles
30529 Print a dump of all known object files. For each object file, this
30530 command prints its name, address in memory, and all of its psymtabs
30533 @kindex maint print section-scripts
30534 @cindex info for known .debug_gdb_scripts-loaded scripts
30535 @item maint print section-scripts [@var{regexp}]
30536 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
30537 If @var{regexp} is specified, only print scripts loaded by object files
30538 matching @var{regexp}.
30539 For each script, this command prints its name as specified in the objfile,
30540 and the full path if known.
30541 @xref{.debug_gdb_scripts section}.
30543 @kindex maint print statistics
30544 @cindex bcache statistics
30545 @item maint print statistics
30546 This command prints, for each object file in the program, various data
30547 about that object file followed by the byte cache (@dfn{bcache})
30548 statistics for the object file. The objfile data includes the number
30549 of minimal, partial, full, and stabs symbols, the number of types
30550 defined by the objfile, the number of as yet unexpanded psym tables,
30551 the number of line tables and string tables, and the amount of memory
30552 used by the various tables. The bcache statistics include the counts,
30553 sizes, and counts of duplicates of all and unique objects, max,
30554 average, and median entry size, total memory used and its overhead and
30555 savings, and various measures of the hash table size and chain
30558 @kindex maint print target-stack
30559 @cindex target stack description
30560 @item maint print target-stack
30561 A @dfn{target} is an interface between the debugger and a particular
30562 kind of file or process. Targets can be stacked in @dfn{strata},
30563 so that more than one target can potentially respond to a request.
30564 In particular, memory accesses will walk down the stack of targets
30565 until they find a target that is interested in handling that particular
30568 This command prints a short description of each layer that was pushed on
30569 the @dfn{target stack}, starting from the top layer down to the bottom one.
30571 @kindex maint print type
30572 @cindex type chain of a data type
30573 @item maint print type @var{expr}
30574 Print the type chain for a type specified by @var{expr}. The argument
30575 can be either a type name or a symbol. If it is a symbol, the type of
30576 that symbol is described. The type chain produced by this command is
30577 a recursive definition of the data type as stored in @value{GDBN}'s
30578 data structures, including its flags and contained types.
30580 @kindex maint set dwarf2 always-disassemble
30581 @kindex maint show dwarf2 always-disassemble
30582 @item maint set dwarf2 always-disassemble
30583 @item maint show dwarf2 always-disassemble
30584 Control the behavior of @code{info address} when using DWARF debugging
30587 The default is @code{off}, which means that @value{GDBN} should try to
30588 describe a variable's location in an easily readable format. When
30589 @code{on}, @value{GDBN} will instead display the DWARF location
30590 expression in an assembly-like format. Note that some locations are
30591 too complex for @value{GDBN} to describe simply; in this case you will
30592 always see the disassembly form.
30594 Here is an example of the resulting disassembly:
30597 (gdb) info addr argc
30598 Symbol "argc" is a complex DWARF expression:
30602 For more information on these expressions, see
30603 @uref{http://www.dwarfstd.org/, the DWARF standard}.
30605 @kindex maint set dwarf2 max-cache-age
30606 @kindex maint show dwarf2 max-cache-age
30607 @item maint set dwarf2 max-cache-age
30608 @itemx maint show dwarf2 max-cache-age
30609 Control the DWARF 2 compilation unit cache.
30611 @cindex DWARF 2 compilation units cache
30612 In object files with inter-compilation-unit references, such as those
30613 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
30614 reader needs to frequently refer to previously read compilation units.
30615 This setting controls how long a compilation unit will remain in the
30616 cache if it is not referenced. A higher limit means that cached
30617 compilation units will be stored in memory longer, and more total
30618 memory will be used. Setting it to zero disables caching, which will
30619 slow down @value{GDBN} startup, but reduce memory consumption.
30621 @kindex maint set profile
30622 @kindex maint show profile
30623 @cindex profiling GDB
30624 @item maint set profile
30625 @itemx maint show profile
30626 Control profiling of @value{GDBN}.
30628 Profiling will be disabled until you use the @samp{maint set profile}
30629 command to enable it. When you enable profiling, the system will begin
30630 collecting timing and execution count data; when you disable profiling or
30631 exit @value{GDBN}, the results will be written to a log file. Remember that
30632 if you use profiling, @value{GDBN} will overwrite the profiling log file
30633 (often called @file{gmon.out}). If you have a record of important profiling
30634 data in a @file{gmon.out} file, be sure to move it to a safe location.
30636 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
30637 compiled with the @samp{-pg} compiler option.
30639 @kindex maint set show-debug-regs
30640 @kindex maint show show-debug-regs
30641 @cindex hardware debug registers
30642 @item maint set show-debug-regs
30643 @itemx maint show show-debug-regs
30644 Control whether to show variables that mirror the hardware debug
30645 registers. Use @code{ON} to enable, @code{OFF} to disable. If
30646 enabled, the debug registers values are shown when @value{GDBN} inserts or
30647 removes a hardware breakpoint or watchpoint, and when the inferior
30648 triggers a hardware-assisted breakpoint or watchpoint.
30650 @kindex maint set show-all-tib
30651 @kindex maint show show-all-tib
30652 @item maint set show-all-tib
30653 @itemx maint show show-all-tib
30654 Control whether to show all non zero areas within a 1k block starting
30655 at thread local base, when using the @samp{info w32 thread-information-block}
30658 @kindex maint space
30659 @cindex memory used by commands
30661 Control whether to display memory usage for each command. If set to a
30662 nonzero value, @value{GDBN} will display how much memory each command
30663 took, following the command's own output. This can also be requested
30664 by invoking @value{GDBN} with the @option{--statistics} command-line
30665 switch (@pxref{Mode Options}).
30668 @cindex time of command execution
30670 Control whether to display the execution time for each command. If
30671 set to a nonzero value, @value{GDBN} will display how much time it
30672 took to execute each command, following the command's own output.
30673 The time is not printed for the commands that run the target, since
30674 there's no mechanism currently to compute how much time was spend
30675 by @value{GDBN} and how much time was spend by the program been debugged.
30676 it's not possibly currently
30677 This can also be requested by invoking @value{GDBN} with the
30678 @option{--statistics} command-line switch (@pxref{Mode Options}).
30680 @kindex maint translate-address
30681 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
30682 Find the symbol stored at the location specified by the address
30683 @var{addr} and an optional section name @var{section}. If found,
30684 @value{GDBN} prints the name of the closest symbol and an offset from
30685 the symbol's location to the specified address. This is similar to
30686 the @code{info address} command (@pxref{Symbols}), except that this
30687 command also allows to find symbols in other sections.
30689 If section was not specified, the section in which the symbol was found
30690 is also printed. For dynamically linked executables, the name of
30691 executable or shared library containing the symbol is printed as well.
30695 The following command is useful for non-interactive invocations of
30696 @value{GDBN}, such as in the test suite.
30699 @item set watchdog @var{nsec}
30700 @kindex set watchdog
30701 @cindex watchdog timer
30702 @cindex timeout for commands
30703 Set the maximum number of seconds @value{GDBN} will wait for the
30704 target operation to finish. If this time expires, @value{GDBN}
30705 reports and error and the command is aborted.
30707 @item show watchdog
30708 Show the current setting of the target wait timeout.
30711 @node Remote Protocol
30712 @appendix @value{GDBN} Remote Serial Protocol
30717 * Stop Reply Packets::
30718 * General Query Packets::
30719 * Architecture-Specific Protocol Details::
30720 * Tracepoint Packets::
30721 * Host I/O Packets::
30723 * Notification Packets::
30724 * Remote Non-Stop::
30725 * Packet Acknowledgment::
30727 * File-I/O Remote Protocol Extension::
30728 * Library List Format::
30729 * Memory Map Format::
30730 * Thread List Format::
30736 There may be occasions when you need to know something about the
30737 protocol---for example, if there is only one serial port to your target
30738 machine, you might want your program to do something special if it
30739 recognizes a packet meant for @value{GDBN}.
30741 In the examples below, @samp{->} and @samp{<-} are used to indicate
30742 transmitted and received data, respectively.
30744 @cindex protocol, @value{GDBN} remote serial
30745 @cindex serial protocol, @value{GDBN} remote
30746 @cindex remote serial protocol
30747 All @value{GDBN} commands and responses (other than acknowledgments
30748 and notifications, see @ref{Notification Packets}) are sent as a
30749 @var{packet}. A @var{packet} is introduced with the character
30750 @samp{$}, the actual @var{packet-data}, and the terminating character
30751 @samp{#} followed by a two-digit @var{checksum}:
30754 @code{$}@var{packet-data}@code{#}@var{checksum}
30758 @cindex checksum, for @value{GDBN} remote
30760 The two-digit @var{checksum} is computed as the modulo 256 sum of all
30761 characters between the leading @samp{$} and the trailing @samp{#} (an
30762 eight bit unsigned checksum).
30764 Implementors should note that prior to @value{GDBN} 5.0 the protocol
30765 specification also included an optional two-digit @var{sequence-id}:
30768 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
30771 @cindex sequence-id, for @value{GDBN} remote
30773 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
30774 has never output @var{sequence-id}s. Stubs that handle packets added
30775 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
30777 When either the host or the target machine receives a packet, the first
30778 response expected is an acknowledgment: either @samp{+} (to indicate
30779 the package was received correctly) or @samp{-} (to request
30783 -> @code{$}@var{packet-data}@code{#}@var{checksum}
30788 The @samp{+}/@samp{-} acknowledgments can be disabled
30789 once a connection is established.
30790 @xref{Packet Acknowledgment}, for details.
30792 The host (@value{GDBN}) sends @var{command}s, and the target (the
30793 debugging stub incorporated in your program) sends a @var{response}. In
30794 the case of step and continue @var{command}s, the response is only sent
30795 when the operation has completed, and the target has again stopped all
30796 threads in all attached processes. This is the default all-stop mode
30797 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
30798 execution mode; see @ref{Remote Non-Stop}, for details.
30800 @var{packet-data} consists of a sequence of characters with the
30801 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
30804 @cindex remote protocol, field separator
30805 Fields within the packet should be separated using @samp{,} @samp{;} or
30806 @samp{:}. Except where otherwise noted all numbers are represented in
30807 @sc{hex} with leading zeros suppressed.
30809 Implementors should note that prior to @value{GDBN} 5.0, the character
30810 @samp{:} could not appear as the third character in a packet (as it
30811 would potentially conflict with the @var{sequence-id}).
30813 @cindex remote protocol, binary data
30814 @anchor{Binary Data}
30815 Binary data in most packets is encoded either as two hexadecimal
30816 digits per byte of binary data. This allowed the traditional remote
30817 protocol to work over connections which were only seven-bit clean.
30818 Some packets designed more recently assume an eight-bit clean
30819 connection, and use a more efficient encoding to send and receive
30822 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
30823 as an escape character. Any escaped byte is transmitted as the escape
30824 character followed by the original character XORed with @code{0x20}.
30825 For example, the byte @code{0x7d} would be transmitted as the two
30826 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
30827 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
30828 @samp{@}}) must always be escaped. Responses sent by the stub
30829 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
30830 is not interpreted as the start of a run-length encoded sequence
30833 Response @var{data} can be run-length encoded to save space.
30834 Run-length encoding replaces runs of identical characters with one
30835 instance of the repeated character, followed by a @samp{*} and a
30836 repeat count. The repeat count is itself sent encoded, to avoid
30837 binary characters in @var{data}: a value of @var{n} is sent as
30838 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
30839 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
30840 code 32) for a repeat count of 3. (This is because run-length
30841 encoding starts to win for counts 3 or more.) Thus, for example,
30842 @samp{0* } is a run-length encoding of ``0000'': the space character
30843 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
30846 The printable characters @samp{#} and @samp{$} or with a numeric value
30847 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
30848 seven repeats (@samp{$}) can be expanded using a repeat count of only
30849 five (@samp{"}). For example, @samp{00000000} can be encoded as
30852 The error response returned for some packets includes a two character
30853 error number. That number is not well defined.
30855 @cindex empty response, for unsupported packets
30856 For any @var{command} not supported by the stub, an empty response
30857 (@samp{$#00}) should be returned. That way it is possible to extend the
30858 protocol. A newer @value{GDBN} can tell if a packet is supported based
30861 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
30862 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
30868 The following table provides a complete list of all currently defined
30869 @var{command}s and their corresponding response @var{data}.
30870 @xref{File-I/O Remote Protocol Extension}, for details about the File
30871 I/O extension of the remote protocol.
30873 Each packet's description has a template showing the packet's overall
30874 syntax, followed by an explanation of the packet's meaning. We
30875 include spaces in some of the templates for clarity; these are not
30876 part of the packet's syntax. No @value{GDBN} packet uses spaces to
30877 separate its components. For example, a template like @samp{foo
30878 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
30879 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
30880 @var{baz}. @value{GDBN} does not transmit a space character between the
30881 @samp{foo} and the @var{bar}, or between the @var{bar} and the
30884 @cindex @var{thread-id}, in remote protocol
30885 @anchor{thread-id syntax}
30886 Several packets and replies include a @var{thread-id} field to identify
30887 a thread. Normally these are positive numbers with a target-specific
30888 interpretation, formatted as big-endian hex strings. A @var{thread-id}
30889 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
30892 In addition, the remote protocol supports a multiprocess feature in
30893 which the @var{thread-id} syntax is extended to optionally include both
30894 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
30895 The @var{pid} (process) and @var{tid} (thread) components each have the
30896 format described above: a positive number with target-specific
30897 interpretation formatted as a big-endian hex string, literal @samp{-1}
30898 to indicate all processes or threads (respectively), or @samp{0} to
30899 indicate an arbitrary process or thread. Specifying just a process, as
30900 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
30901 error to specify all processes but a specific thread, such as
30902 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
30903 for those packets and replies explicitly documented to include a process
30904 ID, rather than a @var{thread-id}.
30906 The multiprocess @var{thread-id} syntax extensions are only used if both
30907 @value{GDBN} and the stub report support for the @samp{multiprocess}
30908 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
30911 Note that all packet forms beginning with an upper- or lower-case
30912 letter, other than those described here, are reserved for future use.
30914 Here are the packet descriptions.
30919 @cindex @samp{!} packet
30920 @anchor{extended mode}
30921 Enable extended mode. In extended mode, the remote server is made
30922 persistent. The @samp{R} packet is used to restart the program being
30928 The remote target both supports and has enabled extended mode.
30932 @cindex @samp{?} packet
30933 Indicate the reason the target halted. The reply is the same as for
30934 step and continue. This packet has a special interpretation when the
30935 target is in non-stop mode; see @ref{Remote Non-Stop}.
30938 @xref{Stop Reply Packets}, for the reply specifications.
30940 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
30941 @cindex @samp{A} packet
30942 Initialized @code{argv[]} array passed into program. @var{arglen}
30943 specifies the number of bytes in the hex encoded byte stream
30944 @var{arg}. See @code{gdbserver} for more details.
30949 The arguments were set.
30955 @cindex @samp{b} packet
30956 (Don't use this packet; its behavior is not well-defined.)
30957 Change the serial line speed to @var{baud}.
30959 JTC: @emph{When does the transport layer state change? When it's
30960 received, or after the ACK is transmitted. In either case, there are
30961 problems if the command or the acknowledgment packet is dropped.}
30963 Stan: @emph{If people really wanted to add something like this, and get
30964 it working for the first time, they ought to modify ser-unix.c to send
30965 some kind of out-of-band message to a specially-setup stub and have the
30966 switch happen "in between" packets, so that from remote protocol's point
30967 of view, nothing actually happened.}
30969 @item B @var{addr},@var{mode}
30970 @cindex @samp{B} packet
30971 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
30972 breakpoint at @var{addr}.
30974 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
30975 (@pxref{insert breakpoint or watchpoint packet}).
30977 @cindex @samp{bc} packet
30980 Backward continue. Execute the target system in reverse. No parameter.
30981 @xref{Reverse Execution}, for more information.
30984 @xref{Stop Reply Packets}, for the reply specifications.
30986 @cindex @samp{bs} packet
30989 Backward single step. Execute one instruction in reverse. No parameter.
30990 @xref{Reverse Execution}, for more information.
30993 @xref{Stop Reply Packets}, for the reply specifications.
30995 @item c @r{[}@var{addr}@r{]}
30996 @cindex @samp{c} packet
30997 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
30998 resume at current address.
31001 @xref{Stop Reply Packets}, for the reply specifications.
31003 @item C @var{sig}@r{[};@var{addr}@r{]}
31004 @cindex @samp{C} packet
31005 Continue with signal @var{sig} (hex signal number). If
31006 @samp{;@var{addr}} is omitted, resume at same address.
31009 @xref{Stop Reply Packets}, for the reply specifications.
31012 @cindex @samp{d} packet
31015 Don't use this packet; instead, define a general set packet
31016 (@pxref{General Query Packets}).
31020 @cindex @samp{D} packet
31021 The first form of the packet is used to detach @value{GDBN} from the
31022 remote system. It is sent to the remote target
31023 before @value{GDBN} disconnects via the @code{detach} command.
31025 The second form, including a process ID, is used when multiprocess
31026 protocol extensions are enabled (@pxref{multiprocess extensions}), to
31027 detach only a specific process. The @var{pid} is specified as a
31028 big-endian hex string.
31038 @item F @var{RC},@var{EE},@var{CF};@var{XX}
31039 @cindex @samp{F} packet
31040 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
31041 This is part of the File-I/O protocol extension. @xref{File-I/O
31042 Remote Protocol Extension}, for the specification.
31045 @anchor{read registers packet}
31046 @cindex @samp{g} packet
31047 Read general registers.
31051 @item @var{XX@dots{}}
31052 Each byte of register data is described by two hex digits. The bytes
31053 with the register are transmitted in target byte order. The size of
31054 each register and their position within the @samp{g} packet are
31055 determined by the @value{GDBN} internal gdbarch functions
31056 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
31057 specification of several standard @samp{g} packets is specified below.
31062 @item G @var{XX@dots{}}
31063 @cindex @samp{G} packet
31064 Write general registers. @xref{read registers packet}, for a
31065 description of the @var{XX@dots{}} data.
31075 @item H @var{c} @var{thread-id}
31076 @cindex @samp{H} packet
31077 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
31078 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
31079 should be @samp{c} for step and continue operations, @samp{g} for other
31080 operations. The thread designator @var{thread-id} has the format and
31081 interpretation described in @ref{thread-id syntax}.
31092 @c 'H': How restrictive (or permissive) is the thread model. If a
31093 @c thread is selected and stopped, are other threads allowed
31094 @c to continue to execute? As I mentioned above, I think the
31095 @c semantics of each command when a thread is selected must be
31096 @c described. For example:
31098 @c 'g': If the stub supports threads and a specific thread is
31099 @c selected, returns the register block from that thread;
31100 @c otherwise returns current registers.
31102 @c 'G' If the stub supports threads and a specific thread is
31103 @c selected, sets the registers of the register block of
31104 @c that thread; otherwise sets current registers.
31106 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
31107 @anchor{cycle step packet}
31108 @cindex @samp{i} packet
31109 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
31110 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
31111 step starting at that address.
31114 @cindex @samp{I} packet
31115 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
31119 @cindex @samp{k} packet
31122 FIXME: @emph{There is no description of how to operate when a specific
31123 thread context has been selected (i.e.@: does 'k' kill only that
31126 @item m @var{addr},@var{length}
31127 @cindex @samp{m} packet
31128 Read @var{length} bytes of memory starting at address @var{addr}.
31129 Note that @var{addr} may not be aligned to any particular boundary.
31131 The stub need not use any particular size or alignment when gathering
31132 data from memory for the response; even if @var{addr} is word-aligned
31133 and @var{length} is a multiple of the word size, the stub is free to
31134 use byte accesses, or not. For this reason, this packet may not be
31135 suitable for accessing memory-mapped I/O devices.
31136 @cindex alignment of remote memory accesses
31137 @cindex size of remote memory accesses
31138 @cindex memory, alignment and size of remote accesses
31142 @item @var{XX@dots{}}
31143 Memory contents; each byte is transmitted as a two-digit hexadecimal
31144 number. The reply may contain fewer bytes than requested if the
31145 server was able to read only part of the region of memory.
31150 @item M @var{addr},@var{length}:@var{XX@dots{}}
31151 @cindex @samp{M} packet
31152 Write @var{length} bytes of memory starting at address @var{addr}.
31153 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
31154 hexadecimal number.
31161 for an error (this includes the case where only part of the data was
31166 @cindex @samp{p} packet
31167 Read the value of register @var{n}; @var{n} is in hex.
31168 @xref{read registers packet}, for a description of how the returned
31169 register value is encoded.
31173 @item @var{XX@dots{}}
31174 the register's value
31178 Indicating an unrecognized @var{query}.
31181 @item P @var{n@dots{}}=@var{r@dots{}}
31182 @anchor{write register packet}
31183 @cindex @samp{P} packet
31184 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
31185 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
31186 digits for each byte in the register (target byte order).
31196 @item q @var{name} @var{params}@dots{}
31197 @itemx Q @var{name} @var{params}@dots{}
31198 @cindex @samp{q} packet
31199 @cindex @samp{Q} packet
31200 General query (@samp{q}) and set (@samp{Q}). These packets are
31201 described fully in @ref{General Query Packets}.
31204 @cindex @samp{r} packet
31205 Reset the entire system.
31207 Don't use this packet; use the @samp{R} packet instead.
31210 @cindex @samp{R} packet
31211 Restart the program being debugged. @var{XX}, while needed, is ignored.
31212 This packet is only available in extended mode (@pxref{extended mode}).
31214 The @samp{R} packet has no reply.
31216 @item s @r{[}@var{addr}@r{]}
31217 @cindex @samp{s} packet
31218 Single step. @var{addr} is the address at which to resume. If
31219 @var{addr} is omitted, resume at same address.
31222 @xref{Stop Reply Packets}, for the reply specifications.
31224 @item S @var{sig}@r{[};@var{addr}@r{]}
31225 @anchor{step with signal packet}
31226 @cindex @samp{S} packet
31227 Step with signal. This is analogous to the @samp{C} packet, but
31228 requests a single-step, rather than a normal resumption of execution.
31231 @xref{Stop Reply Packets}, for the reply specifications.
31233 @item t @var{addr}:@var{PP},@var{MM}
31234 @cindex @samp{t} packet
31235 Search backwards starting at address @var{addr} for a match with pattern
31236 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
31237 @var{addr} must be at least 3 digits.
31239 @item T @var{thread-id}
31240 @cindex @samp{T} packet
31241 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
31246 thread is still alive
31252 Packets starting with @samp{v} are identified by a multi-letter name,
31253 up to the first @samp{;} or @samp{?} (or the end of the packet).
31255 @item vAttach;@var{pid}
31256 @cindex @samp{vAttach} packet
31257 Attach to a new process with the specified process ID @var{pid}.
31258 The process ID is a
31259 hexadecimal integer identifying the process. In all-stop mode, all
31260 threads in the attached process are stopped; in non-stop mode, it may be
31261 attached without being stopped if that is supported by the target.
31263 @c In non-stop mode, on a successful vAttach, the stub should set the
31264 @c current thread to a thread of the newly-attached process. After
31265 @c attaching, GDB queries for the attached process's thread ID with qC.
31266 @c Also note that, from a user perspective, whether or not the
31267 @c target is stopped on attach in non-stop mode depends on whether you
31268 @c use the foreground or background version of the attach command, not
31269 @c on what vAttach does; GDB does the right thing with respect to either
31270 @c stopping or restarting threads.
31272 This packet is only available in extended mode (@pxref{extended mode}).
31278 @item @r{Any stop packet}
31279 for success in all-stop mode (@pxref{Stop Reply Packets})
31281 for success in non-stop mode (@pxref{Remote Non-Stop})
31284 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
31285 @cindex @samp{vCont} packet
31286 Resume the inferior, specifying different actions for each thread.
31287 If an action is specified with no @var{thread-id}, then it is applied to any
31288 threads that don't have a specific action specified; if no default action is
31289 specified then other threads should remain stopped in all-stop mode and
31290 in their current state in non-stop mode.
31291 Specifying multiple
31292 default actions is an error; specifying no actions is also an error.
31293 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
31295 Currently supported actions are:
31301 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
31305 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
31310 The optional argument @var{addr} normally associated with the
31311 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
31312 not supported in @samp{vCont}.
31314 The @samp{t} action is only relevant in non-stop mode
31315 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
31316 A stop reply should be generated for any affected thread not already stopped.
31317 When a thread is stopped by means of a @samp{t} action,
31318 the corresponding stop reply should indicate that the thread has stopped with
31319 signal @samp{0}, regardless of whether the target uses some other signal
31320 as an implementation detail.
31323 @xref{Stop Reply Packets}, for the reply specifications.
31326 @cindex @samp{vCont?} packet
31327 Request a list of actions supported by the @samp{vCont} packet.
31331 @item vCont@r{[};@var{action}@dots{}@r{]}
31332 The @samp{vCont} packet is supported. Each @var{action} is a supported
31333 command in the @samp{vCont} packet.
31335 The @samp{vCont} packet is not supported.
31338 @item vFile:@var{operation}:@var{parameter}@dots{}
31339 @cindex @samp{vFile} packet
31340 Perform a file operation on the target system. For details,
31341 see @ref{Host I/O Packets}.
31343 @item vFlashErase:@var{addr},@var{length}
31344 @cindex @samp{vFlashErase} packet
31345 Direct the stub to erase @var{length} bytes of flash starting at
31346 @var{addr}. The region may enclose any number of flash blocks, but
31347 its start and end must fall on block boundaries, as indicated by the
31348 flash block size appearing in the memory map (@pxref{Memory Map
31349 Format}). @value{GDBN} groups flash memory programming operations
31350 together, and sends a @samp{vFlashDone} request after each group; the
31351 stub is allowed to delay erase operation until the @samp{vFlashDone}
31352 packet is received.
31354 The stub must support @samp{vCont} if it reports support for
31355 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
31356 this case @samp{vCont} actions can be specified to apply to all threads
31357 in a process by using the @samp{p@var{pid}.-1} form of the
31368 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
31369 @cindex @samp{vFlashWrite} packet
31370 Direct the stub to write data to flash address @var{addr}. The data
31371 is passed in binary form using the same encoding as for the @samp{X}
31372 packet (@pxref{Binary Data}). The memory ranges specified by
31373 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
31374 not overlap, and must appear in order of increasing addresses
31375 (although @samp{vFlashErase} packets for higher addresses may already
31376 have been received; the ordering is guaranteed only between
31377 @samp{vFlashWrite} packets). If a packet writes to an address that was
31378 neither erased by a preceding @samp{vFlashErase} packet nor by some other
31379 target-specific method, the results are unpredictable.
31387 for vFlashWrite addressing non-flash memory
31393 @cindex @samp{vFlashDone} packet
31394 Indicate to the stub that flash programming operation is finished.
31395 The stub is permitted to delay or batch the effects of a group of
31396 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
31397 @samp{vFlashDone} packet is received. The contents of the affected
31398 regions of flash memory are unpredictable until the @samp{vFlashDone}
31399 request is completed.
31401 @item vKill;@var{pid}
31402 @cindex @samp{vKill} packet
31403 Kill the process with the specified process ID. @var{pid} is a
31404 hexadecimal integer identifying the process. This packet is used in
31405 preference to @samp{k} when multiprocess protocol extensions are
31406 supported; see @ref{multiprocess extensions}.
31416 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
31417 @cindex @samp{vRun} packet
31418 Run the program @var{filename}, passing it each @var{argument} on its
31419 command line. The file and arguments are hex-encoded strings. If
31420 @var{filename} is an empty string, the stub may use a default program
31421 (e.g.@: the last program run). The program is created in the stopped
31424 @c FIXME: What about non-stop mode?
31426 This packet is only available in extended mode (@pxref{extended mode}).
31432 @item @r{Any stop packet}
31433 for success (@pxref{Stop Reply Packets})
31437 @anchor{vStopped packet}
31438 @cindex @samp{vStopped} packet
31440 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
31441 reply and prompt for the stub to report another one.
31445 @item @r{Any stop packet}
31446 if there is another unreported stop event (@pxref{Stop Reply Packets})
31448 if there are no unreported stop events
31451 @item X @var{addr},@var{length}:@var{XX@dots{}}
31453 @cindex @samp{X} packet
31454 Write data to memory, where the data is transmitted in binary.
31455 @var{addr} is address, @var{length} is number of bytes,
31456 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
31466 @item z @var{type},@var{addr},@var{kind}
31467 @itemx Z @var{type},@var{addr},@var{kind}
31468 @anchor{insert breakpoint or watchpoint packet}
31469 @cindex @samp{z} packet
31470 @cindex @samp{Z} packets
31471 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
31472 watchpoint starting at address @var{address} of kind @var{kind}.
31474 Each breakpoint and watchpoint packet @var{type} is documented
31477 @emph{Implementation notes: A remote target shall return an empty string
31478 for an unrecognized breakpoint or watchpoint packet @var{type}. A
31479 remote target shall support either both or neither of a given
31480 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
31481 avoid potential problems with duplicate packets, the operations should
31482 be implemented in an idempotent way.}
31484 @item z0,@var{addr},@var{kind}
31485 @itemx Z0,@var{addr},@var{kind}
31486 @cindex @samp{z0} packet
31487 @cindex @samp{Z0} packet
31488 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
31489 @var{addr} of type @var{kind}.
31491 A memory breakpoint is implemented by replacing the instruction at
31492 @var{addr} with a software breakpoint or trap instruction. The
31493 @var{kind} is target-specific and typically indicates the size of
31494 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
31495 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
31496 architectures have additional meanings for @var{kind};
31497 see @ref{Architecture-Specific Protocol Details}.
31499 @emph{Implementation note: It is possible for a target to copy or move
31500 code that contains memory breakpoints (e.g., when implementing
31501 overlays). The behavior of this packet, in the presence of such a
31502 target, is not defined.}
31514 @item z1,@var{addr},@var{kind}
31515 @itemx Z1,@var{addr},@var{kind}
31516 @cindex @samp{z1} packet
31517 @cindex @samp{Z1} packet
31518 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
31519 address @var{addr}.
31521 A hardware breakpoint is implemented using a mechanism that is not
31522 dependant on being able to modify the target's memory. @var{kind}
31523 has the same meaning as in @samp{Z0} packets.
31525 @emph{Implementation note: A hardware breakpoint is not affected by code
31538 @item z2,@var{addr},@var{kind}
31539 @itemx Z2,@var{addr},@var{kind}
31540 @cindex @samp{z2} packet
31541 @cindex @samp{Z2} packet
31542 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
31543 @var{kind} is interpreted as the number of bytes to watch.
31555 @item z3,@var{addr},@var{kind}
31556 @itemx Z3,@var{addr},@var{kind}
31557 @cindex @samp{z3} packet
31558 @cindex @samp{Z3} packet
31559 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
31560 @var{kind} is interpreted as the number of bytes to watch.
31572 @item z4,@var{addr},@var{kind}
31573 @itemx Z4,@var{addr},@var{kind}
31574 @cindex @samp{z4} packet
31575 @cindex @samp{Z4} packet
31576 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
31577 @var{kind} is interpreted as the number of bytes to watch.
31591 @node Stop Reply Packets
31592 @section Stop Reply Packets
31593 @cindex stop reply packets
31595 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
31596 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
31597 receive any of the below as a reply. Except for @samp{?}
31598 and @samp{vStopped}, that reply is only returned
31599 when the target halts. In the below the exact meaning of @dfn{signal
31600 number} is defined by the header @file{include/gdb/signals.h} in the
31601 @value{GDBN} source code.
31603 As in the description of request packets, we include spaces in the
31604 reply templates for clarity; these are not part of the reply packet's
31605 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
31611 The program received signal number @var{AA} (a two-digit hexadecimal
31612 number). This is equivalent to a @samp{T} response with no
31613 @var{n}:@var{r} pairs.
31615 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
31616 @cindex @samp{T} packet reply
31617 The program received signal number @var{AA} (a two-digit hexadecimal
31618 number). This is equivalent to an @samp{S} response, except that the
31619 @samp{@var{n}:@var{r}} pairs can carry values of important registers
31620 and other information directly in the stop reply packet, reducing
31621 round-trip latency. Single-step and breakpoint traps are reported
31622 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
31626 If @var{n} is a hexadecimal number, it is a register number, and the
31627 corresponding @var{r} gives that register's value. @var{r} is a
31628 series of bytes in target byte order, with each byte given by a
31629 two-digit hex number.
31632 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
31633 the stopped thread, as specified in @ref{thread-id syntax}.
31636 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
31637 the core on which the stop event was detected.
31640 If @var{n} is a recognized @dfn{stop reason}, it describes a more
31641 specific event that stopped the target. The currently defined stop
31642 reasons are listed below. @var{aa} should be @samp{05}, the trap
31643 signal. At most one stop reason should be present.
31646 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
31647 and go on to the next; this allows us to extend the protocol in the
31651 The currently defined stop reasons are:
31657 The packet indicates a watchpoint hit, and @var{r} is the data address, in
31660 @cindex shared library events, remote reply
31662 The packet indicates that the loaded libraries have changed.
31663 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
31664 list of loaded libraries. @var{r} is ignored.
31666 @cindex replay log events, remote reply
31668 The packet indicates that the target cannot continue replaying
31669 logged execution events, because it has reached the end (or the
31670 beginning when executing backward) of the log. The value of @var{r}
31671 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
31672 for more information.
31676 @itemx W @var{AA} ; process:@var{pid}
31677 The process exited, and @var{AA} is the exit status. This is only
31678 applicable to certain targets.
31680 The second form of the response, including the process ID of the exited
31681 process, can be used only when @value{GDBN} has reported support for
31682 multiprocess protocol extensions; see @ref{multiprocess extensions}.
31683 The @var{pid} is formatted as a big-endian hex string.
31686 @itemx X @var{AA} ; process:@var{pid}
31687 The process terminated with signal @var{AA}.
31689 The second form of the response, including the process ID of the
31690 terminated process, can be used only when @value{GDBN} has reported
31691 support for multiprocess protocol extensions; see @ref{multiprocess
31692 extensions}. The @var{pid} is formatted as a big-endian hex string.
31694 @item O @var{XX}@dots{}
31695 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
31696 written as the program's console output. This can happen at any time
31697 while the program is running and the debugger should continue to wait
31698 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
31700 @item F @var{call-id},@var{parameter}@dots{}
31701 @var{call-id} is the identifier which says which host system call should
31702 be called. This is just the name of the function. Translation into the
31703 correct system call is only applicable as it's defined in @value{GDBN}.
31704 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
31707 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
31708 this very system call.
31710 The target replies with this packet when it expects @value{GDBN} to
31711 call a host system call on behalf of the target. @value{GDBN} replies
31712 with an appropriate @samp{F} packet and keeps up waiting for the next
31713 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
31714 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
31715 Protocol Extension}, for more details.
31719 @node General Query Packets
31720 @section General Query Packets
31721 @cindex remote query requests
31723 Packets starting with @samp{q} are @dfn{general query packets};
31724 packets starting with @samp{Q} are @dfn{general set packets}. General
31725 query and set packets are a semi-unified form for retrieving and
31726 sending information to and from the stub.
31728 The initial letter of a query or set packet is followed by a name
31729 indicating what sort of thing the packet applies to. For example,
31730 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
31731 definitions with the stub. These packet names follow some
31736 The name must not contain commas, colons or semicolons.
31738 Most @value{GDBN} query and set packets have a leading upper case
31741 The names of custom vendor packets should use a company prefix, in
31742 lower case, followed by a period. For example, packets designed at
31743 the Acme Corporation might begin with @samp{qacme.foo} (for querying
31744 foos) or @samp{Qacme.bar} (for setting bars).
31747 The name of a query or set packet should be separated from any
31748 parameters by a @samp{:}; the parameters themselves should be
31749 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
31750 full packet name, and check for a separator or the end of the packet,
31751 in case two packet names share a common prefix. New packets should not begin
31752 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
31753 packets predate these conventions, and have arguments without any terminator
31754 for the packet name; we suspect they are in widespread use in places that
31755 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
31756 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
31759 Like the descriptions of the other packets, each description here
31760 has a template showing the packet's overall syntax, followed by an
31761 explanation of the packet's meaning. We include spaces in some of the
31762 templates for clarity; these are not part of the packet's syntax. No
31763 @value{GDBN} packet uses spaces to separate its components.
31765 Here are the currently defined query and set packets:
31769 @item QAllow:@var{op}:@var{val}@dots{}
31770 @cindex @samp{QAllow} packet
31771 Specify which operations @value{GDBN} expects to request of the
31772 target, as a semicolon-separated list of operation name and value
31773 pairs. Possible values for @var{op} include @samp{WriteReg},
31774 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
31775 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
31776 indicating that @value{GDBN} will not request the operation, or 1,
31777 indicating that it may. (The target can then use this to set up its
31778 own internals optimally, for instance if the debugger never expects to
31779 insert breakpoints, it may not need to install its own trap handler.)
31782 @cindex current thread, remote request
31783 @cindex @samp{qC} packet
31784 Return the current thread ID.
31788 @item QC @var{thread-id}
31789 Where @var{thread-id} is a thread ID as documented in
31790 @ref{thread-id syntax}.
31791 @item @r{(anything else)}
31792 Any other reply implies the old thread ID.
31795 @item qCRC:@var{addr},@var{length}
31796 @cindex CRC of memory block, remote request
31797 @cindex @samp{qCRC} packet
31798 Compute the CRC checksum of a block of memory using CRC-32 defined in
31799 IEEE 802.3. The CRC is computed byte at a time, taking the most
31800 significant bit of each byte first. The initial pattern code
31801 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
31803 @emph{Note:} This is the same CRC used in validating separate debug
31804 files (@pxref{Separate Debug Files, , Debugging Information in Separate
31805 Files}). However the algorithm is slightly different. When validating
31806 separate debug files, the CRC is computed taking the @emph{least}
31807 significant bit of each byte first, and the final result is inverted to
31808 detect trailing zeros.
31813 An error (such as memory fault)
31814 @item C @var{crc32}
31815 The specified memory region's checksum is @var{crc32}.
31819 @itemx qsThreadInfo
31820 @cindex list active threads, remote request
31821 @cindex @samp{qfThreadInfo} packet
31822 @cindex @samp{qsThreadInfo} packet
31823 Obtain a list of all active thread IDs from the target (OS). Since there
31824 may be too many active threads to fit into one reply packet, this query
31825 works iteratively: it may require more than one query/reply sequence to
31826 obtain the entire list of threads. The first query of the sequence will
31827 be the @samp{qfThreadInfo} query; subsequent queries in the
31828 sequence will be the @samp{qsThreadInfo} query.
31830 NOTE: This packet replaces the @samp{qL} query (see below).
31834 @item m @var{thread-id}
31836 @item m @var{thread-id},@var{thread-id}@dots{}
31837 a comma-separated list of thread IDs
31839 (lower case letter @samp{L}) denotes end of list.
31842 In response to each query, the target will reply with a list of one or
31843 more thread IDs, separated by commas.
31844 @value{GDBN} will respond to each reply with a request for more thread
31845 ids (using the @samp{qs} form of the query), until the target responds
31846 with @samp{l} (lower-case ell, for @dfn{last}).
31847 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
31850 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
31851 @cindex get thread-local storage address, remote request
31852 @cindex @samp{qGetTLSAddr} packet
31853 Fetch the address associated with thread local storage specified
31854 by @var{thread-id}, @var{offset}, and @var{lm}.
31856 @var{thread-id} is the thread ID associated with the
31857 thread for which to fetch the TLS address. @xref{thread-id syntax}.
31859 @var{offset} is the (big endian, hex encoded) offset associated with the
31860 thread local variable. (This offset is obtained from the debug
31861 information associated with the variable.)
31863 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
31864 the load module associated with the thread local storage. For example,
31865 a @sc{gnu}/Linux system will pass the link map address of the shared
31866 object associated with the thread local storage under consideration.
31867 Other operating environments may choose to represent the load module
31868 differently, so the precise meaning of this parameter will vary.
31872 @item @var{XX}@dots{}
31873 Hex encoded (big endian) bytes representing the address of the thread
31874 local storage requested.
31877 An error occurred. @var{nn} are hex digits.
31880 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
31883 @item qGetTIBAddr:@var{thread-id}
31884 @cindex get thread information block address
31885 @cindex @samp{qGetTIBAddr} packet
31886 Fetch address of the Windows OS specific Thread Information Block.
31888 @var{thread-id} is the thread ID associated with the thread.
31892 @item @var{XX}@dots{}
31893 Hex encoded (big endian) bytes representing the linear address of the
31894 thread information block.
31897 An error occured. This means that either the thread was not found, or the
31898 address could not be retrieved.
31901 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
31904 @item qL @var{startflag} @var{threadcount} @var{nextthread}
31905 Obtain thread information from RTOS. Where: @var{startflag} (one hex
31906 digit) is one to indicate the first query and zero to indicate a
31907 subsequent query; @var{threadcount} (two hex digits) is the maximum
31908 number of threads the response packet can contain; and @var{nextthread}
31909 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
31910 returned in the response as @var{argthread}.
31912 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
31916 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
31917 Where: @var{count} (two hex digits) is the number of threads being
31918 returned; @var{done} (one hex digit) is zero to indicate more threads
31919 and one indicates no further threads; @var{argthreadid} (eight hex
31920 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
31921 is a sequence of thread IDs from the target. @var{threadid} (eight hex
31922 digits). See @code{remote.c:parse_threadlist_response()}.
31926 @cindex section offsets, remote request
31927 @cindex @samp{qOffsets} packet
31928 Get section offsets that the target used when relocating the downloaded
31933 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
31934 Relocate the @code{Text} section by @var{xxx} from its original address.
31935 Relocate the @code{Data} section by @var{yyy} from its original address.
31936 If the object file format provides segment information (e.g.@: @sc{elf}
31937 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
31938 segments by the supplied offsets.
31940 @emph{Note: while a @code{Bss} offset may be included in the response,
31941 @value{GDBN} ignores this and instead applies the @code{Data} offset
31942 to the @code{Bss} section.}
31944 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
31945 Relocate the first segment of the object file, which conventionally
31946 contains program code, to a starting address of @var{xxx}. If
31947 @samp{DataSeg} is specified, relocate the second segment, which
31948 conventionally contains modifiable data, to a starting address of
31949 @var{yyy}. @value{GDBN} will report an error if the object file
31950 does not contain segment information, or does not contain at least
31951 as many segments as mentioned in the reply. Extra segments are
31952 kept at fixed offsets relative to the last relocated segment.
31955 @item qP @var{mode} @var{thread-id}
31956 @cindex thread information, remote request
31957 @cindex @samp{qP} packet
31958 Returns information on @var{thread-id}. Where: @var{mode} is a hex
31959 encoded 32 bit mode; @var{thread-id} is a thread ID
31960 (@pxref{thread-id syntax}).
31962 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
31965 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
31969 @cindex non-stop mode, remote request
31970 @cindex @samp{QNonStop} packet
31972 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
31973 @xref{Remote Non-Stop}, for more information.
31978 The request succeeded.
31981 An error occurred. @var{nn} are hex digits.
31984 An empty reply indicates that @samp{QNonStop} is not supported by
31988 This packet is not probed by default; the remote stub must request it,
31989 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31990 Use of this packet is controlled by the @code{set non-stop} command;
31991 @pxref{Non-Stop Mode}.
31993 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
31994 @cindex pass signals to inferior, remote request
31995 @cindex @samp{QPassSignals} packet
31996 @anchor{QPassSignals}
31997 Each listed @var{signal} should be passed directly to the inferior process.
31998 Signals are numbered identically to continue packets and stop replies
31999 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
32000 strictly greater than the previous item. These signals do not need to stop
32001 the inferior, or be reported to @value{GDBN}. All other signals should be
32002 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
32003 combine; any earlier @samp{QPassSignals} list is completely replaced by the
32004 new list. This packet improves performance when using @samp{handle
32005 @var{signal} nostop noprint pass}.
32010 The request succeeded.
32013 An error occurred. @var{nn} are hex digits.
32016 An empty reply indicates that @samp{QPassSignals} is not supported by
32020 Use of this packet is controlled by the @code{set remote pass-signals}
32021 command (@pxref{Remote Configuration, set remote pass-signals}).
32022 This packet is not probed by default; the remote stub must request it,
32023 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32025 @item qRcmd,@var{command}
32026 @cindex execute remote command, remote request
32027 @cindex @samp{qRcmd} packet
32028 @var{command} (hex encoded) is passed to the local interpreter for
32029 execution. Invalid commands should be reported using the output
32030 string. Before the final result packet, the target may also respond
32031 with a number of intermediate @samp{O@var{output}} console output
32032 packets. @emph{Implementors should note that providing access to a
32033 stubs's interpreter may have security implications}.
32038 A command response with no output.
32040 A command response with the hex encoded output string @var{OUTPUT}.
32042 Indicate a badly formed request.
32044 An empty reply indicates that @samp{qRcmd} is not recognized.
32047 (Note that the @code{qRcmd} packet's name is separated from the
32048 command by a @samp{,}, not a @samp{:}, contrary to the naming
32049 conventions above. Please don't use this packet as a model for new
32052 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
32053 @cindex searching memory, in remote debugging
32054 @cindex @samp{qSearch:memory} packet
32055 @anchor{qSearch memory}
32056 Search @var{length} bytes at @var{address} for @var{search-pattern}.
32057 @var{address} and @var{length} are encoded in hex.
32058 @var{search-pattern} is a sequence of bytes, hex encoded.
32063 The pattern was not found.
32065 The pattern was found at @var{address}.
32067 A badly formed request or an error was encountered while searching memory.
32069 An empty reply indicates that @samp{qSearch:memory} is not recognized.
32072 @item QStartNoAckMode
32073 @cindex @samp{QStartNoAckMode} packet
32074 @anchor{QStartNoAckMode}
32075 Request that the remote stub disable the normal @samp{+}/@samp{-}
32076 protocol acknowledgments (@pxref{Packet Acknowledgment}).
32081 The stub has switched to no-acknowledgment mode.
32082 @value{GDBN} acknowledges this reponse,
32083 but neither the stub nor @value{GDBN} shall send or expect further
32084 @samp{+}/@samp{-} acknowledgments in the current connection.
32086 An empty reply indicates that the stub does not support no-acknowledgment mode.
32089 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
32090 @cindex supported packets, remote query
32091 @cindex features of the remote protocol
32092 @cindex @samp{qSupported} packet
32093 @anchor{qSupported}
32094 Tell the remote stub about features supported by @value{GDBN}, and
32095 query the stub for features it supports. This packet allows
32096 @value{GDBN} and the remote stub to take advantage of each others'
32097 features. @samp{qSupported} also consolidates multiple feature probes
32098 at startup, to improve @value{GDBN} performance---a single larger
32099 packet performs better than multiple smaller probe packets on
32100 high-latency links. Some features may enable behavior which must not
32101 be on by default, e.g.@: because it would confuse older clients or
32102 stubs. Other features may describe packets which could be
32103 automatically probed for, but are not. These features must be
32104 reported before @value{GDBN} will use them. This ``default
32105 unsupported'' behavior is not appropriate for all packets, but it
32106 helps to keep the initial connection time under control with new
32107 versions of @value{GDBN} which support increasing numbers of packets.
32111 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
32112 The stub supports or does not support each returned @var{stubfeature},
32113 depending on the form of each @var{stubfeature} (see below for the
32116 An empty reply indicates that @samp{qSupported} is not recognized,
32117 or that no features needed to be reported to @value{GDBN}.
32120 The allowed forms for each feature (either a @var{gdbfeature} in the
32121 @samp{qSupported} packet, or a @var{stubfeature} in the response)
32125 @item @var{name}=@var{value}
32126 The remote protocol feature @var{name} is supported, and associated
32127 with the specified @var{value}. The format of @var{value} depends
32128 on the feature, but it must not include a semicolon.
32130 The remote protocol feature @var{name} is supported, and does not
32131 need an associated value.
32133 The remote protocol feature @var{name} is not supported.
32135 The remote protocol feature @var{name} may be supported, and
32136 @value{GDBN} should auto-detect support in some other way when it is
32137 needed. This form will not be used for @var{gdbfeature} notifications,
32138 but may be used for @var{stubfeature} responses.
32141 Whenever the stub receives a @samp{qSupported} request, the
32142 supplied set of @value{GDBN} features should override any previous
32143 request. This allows @value{GDBN} to put the stub in a known
32144 state, even if the stub had previously been communicating with
32145 a different version of @value{GDBN}.
32147 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
32152 This feature indicates whether @value{GDBN} supports multiprocess
32153 extensions to the remote protocol. @value{GDBN} does not use such
32154 extensions unless the stub also reports that it supports them by
32155 including @samp{multiprocess+} in its @samp{qSupported} reply.
32156 @xref{multiprocess extensions}, for details.
32159 This feature indicates that @value{GDBN} supports the XML target
32160 description. If the stub sees @samp{xmlRegisters=} with target
32161 specific strings separated by a comma, it will report register
32165 This feature indicates whether @value{GDBN} supports the
32166 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
32167 instruction reply packet}).
32170 Stubs should ignore any unknown values for
32171 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
32172 packet supports receiving packets of unlimited length (earlier
32173 versions of @value{GDBN} may reject overly long responses). Additional values
32174 for @var{gdbfeature} may be defined in the future to let the stub take
32175 advantage of new features in @value{GDBN}, e.g.@: incompatible
32176 improvements in the remote protocol---the @samp{multiprocess} feature is
32177 an example of such a feature. The stub's reply should be independent
32178 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
32179 describes all the features it supports, and then the stub replies with
32180 all the features it supports.
32182 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
32183 responses, as long as each response uses one of the standard forms.
32185 Some features are flags. A stub which supports a flag feature
32186 should respond with a @samp{+} form response. Other features
32187 require values, and the stub should respond with an @samp{=}
32190 Each feature has a default value, which @value{GDBN} will use if
32191 @samp{qSupported} is not available or if the feature is not mentioned
32192 in the @samp{qSupported} response. The default values are fixed; a
32193 stub is free to omit any feature responses that match the defaults.
32195 Not all features can be probed, but for those which can, the probing
32196 mechanism is useful: in some cases, a stub's internal
32197 architecture may not allow the protocol layer to know some information
32198 about the underlying target in advance. This is especially common in
32199 stubs which may be configured for multiple targets.
32201 These are the currently defined stub features and their properties:
32203 @multitable @columnfractions 0.35 0.2 0.12 0.2
32204 @c NOTE: The first row should be @headitem, but we do not yet require
32205 @c a new enough version of Texinfo (4.7) to use @headitem.
32207 @tab Value Required
32211 @item @samp{PacketSize}
32216 @item @samp{qXfer:auxv:read}
32221 @item @samp{qXfer:features:read}
32226 @item @samp{qXfer:libraries:read}
32231 @item @samp{qXfer:memory-map:read}
32236 @item @samp{qXfer:sdata:read}
32241 @item @samp{qXfer:spu:read}
32246 @item @samp{qXfer:spu:write}
32251 @item @samp{qXfer:siginfo:read}
32256 @item @samp{qXfer:siginfo:write}
32261 @item @samp{qXfer:threads:read}
32267 @item @samp{QNonStop}
32272 @item @samp{QPassSignals}
32277 @item @samp{QStartNoAckMode}
32282 @item @samp{multiprocess}
32287 @item @samp{ConditionalTracepoints}
32292 @item @samp{ReverseContinue}
32297 @item @samp{ReverseStep}
32302 @item @samp{TracepointSource}
32307 @item @samp{QAllow}
32314 These are the currently defined stub features, in more detail:
32317 @cindex packet size, remote protocol
32318 @item PacketSize=@var{bytes}
32319 The remote stub can accept packets up to at least @var{bytes} in
32320 length. @value{GDBN} will send packets up to this size for bulk
32321 transfers, and will never send larger packets. This is a limit on the
32322 data characters in the packet, including the frame and checksum.
32323 There is no trailing NUL byte in a remote protocol packet; if the stub
32324 stores packets in a NUL-terminated format, it should allow an extra
32325 byte in its buffer for the NUL. If this stub feature is not supported,
32326 @value{GDBN} guesses based on the size of the @samp{g} packet response.
32328 @item qXfer:auxv:read
32329 The remote stub understands the @samp{qXfer:auxv:read} packet
32330 (@pxref{qXfer auxiliary vector read}).
32332 @item qXfer:features:read
32333 The remote stub understands the @samp{qXfer:features:read} packet
32334 (@pxref{qXfer target description read}).
32336 @item qXfer:libraries:read
32337 The remote stub understands the @samp{qXfer:libraries:read} packet
32338 (@pxref{qXfer library list read}).
32340 @item qXfer:memory-map:read
32341 The remote stub understands the @samp{qXfer:memory-map:read} packet
32342 (@pxref{qXfer memory map read}).
32344 @item qXfer:sdata:read
32345 The remote stub understands the @samp{qXfer:sdata:read} packet
32346 (@pxref{qXfer sdata read}).
32348 @item qXfer:spu:read
32349 The remote stub understands the @samp{qXfer:spu:read} packet
32350 (@pxref{qXfer spu read}).
32352 @item qXfer:spu:write
32353 The remote stub understands the @samp{qXfer:spu:write} packet
32354 (@pxref{qXfer spu write}).
32356 @item qXfer:siginfo:read
32357 The remote stub understands the @samp{qXfer:siginfo:read} packet
32358 (@pxref{qXfer siginfo read}).
32360 @item qXfer:siginfo:write
32361 The remote stub understands the @samp{qXfer:siginfo:write} packet
32362 (@pxref{qXfer siginfo write}).
32364 @item qXfer:threads:read
32365 The remote stub understands the @samp{qXfer:threads:read} packet
32366 (@pxref{qXfer threads read}).
32369 The remote stub understands the @samp{QNonStop} packet
32370 (@pxref{QNonStop}).
32373 The remote stub understands the @samp{QPassSignals} packet
32374 (@pxref{QPassSignals}).
32376 @item QStartNoAckMode
32377 The remote stub understands the @samp{QStartNoAckMode} packet and
32378 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
32381 @anchor{multiprocess extensions}
32382 @cindex multiprocess extensions, in remote protocol
32383 The remote stub understands the multiprocess extensions to the remote
32384 protocol syntax. The multiprocess extensions affect the syntax of
32385 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
32386 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
32387 replies. Note that reporting this feature indicates support for the
32388 syntactic extensions only, not that the stub necessarily supports
32389 debugging of more than one process at a time. The stub must not use
32390 multiprocess extensions in packet replies unless @value{GDBN} has also
32391 indicated it supports them in its @samp{qSupported} request.
32393 @item qXfer:osdata:read
32394 The remote stub understands the @samp{qXfer:osdata:read} packet
32395 ((@pxref{qXfer osdata read}).
32397 @item ConditionalTracepoints
32398 The remote stub accepts and implements conditional expressions defined
32399 for tracepoints (@pxref{Tracepoint Conditions}).
32401 @item ReverseContinue
32402 The remote stub accepts and implements the reverse continue packet
32406 The remote stub accepts and implements the reverse step packet
32409 @item TracepointSource
32410 The remote stub understands the @samp{QTDPsrc} packet that supplies
32411 the source form of tracepoint definitions.
32414 The remote stub understands the @samp{QAllow} packet.
32416 @item StaticTracepoint
32417 @cindex static tracepoints, in remote protocol
32418 The remote stub supports static tracepoints.
32423 @cindex symbol lookup, remote request
32424 @cindex @samp{qSymbol} packet
32425 Notify the target that @value{GDBN} is prepared to serve symbol lookup
32426 requests. Accept requests from the target for the values of symbols.
32431 The target does not need to look up any (more) symbols.
32432 @item qSymbol:@var{sym_name}
32433 The target requests the value of symbol @var{sym_name} (hex encoded).
32434 @value{GDBN} may provide the value by using the
32435 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
32439 @item qSymbol:@var{sym_value}:@var{sym_name}
32440 Set the value of @var{sym_name} to @var{sym_value}.
32442 @var{sym_name} (hex encoded) is the name of a symbol whose value the
32443 target has previously requested.
32445 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
32446 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
32452 The target does not need to look up any (more) symbols.
32453 @item qSymbol:@var{sym_name}
32454 The target requests the value of a new symbol @var{sym_name} (hex
32455 encoded). @value{GDBN} will continue to supply the values of symbols
32456 (if available), until the target ceases to request them.
32461 @item QTDisconnected
32468 @xref{Tracepoint Packets}.
32470 @item qThreadExtraInfo,@var{thread-id}
32471 @cindex thread attributes info, remote request
32472 @cindex @samp{qThreadExtraInfo} packet
32473 Obtain a printable string description of a thread's attributes from
32474 the target OS. @var{thread-id} is a thread ID;
32475 see @ref{thread-id syntax}. This
32476 string may contain anything that the target OS thinks is interesting
32477 for @value{GDBN} to tell the user about the thread. The string is
32478 displayed in @value{GDBN}'s @code{info threads} display. Some
32479 examples of possible thread extra info strings are @samp{Runnable}, or
32480 @samp{Blocked on Mutex}.
32484 @item @var{XX}@dots{}
32485 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
32486 comprising the printable string containing the extra information about
32487 the thread's attributes.
32490 (Note that the @code{qThreadExtraInfo} packet's name is separated from
32491 the command by a @samp{,}, not a @samp{:}, contrary to the naming
32492 conventions above. Please don't use this packet as a model for new
32507 @xref{Tracepoint Packets}.
32509 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
32510 @cindex read special object, remote request
32511 @cindex @samp{qXfer} packet
32512 @anchor{qXfer read}
32513 Read uninterpreted bytes from the target's special data area
32514 identified by the keyword @var{object}. Request @var{length} bytes
32515 starting at @var{offset} bytes into the data. The content and
32516 encoding of @var{annex} is specific to @var{object}; it can supply
32517 additional details about what data to access.
32519 Here are the specific requests of this form defined so far. All
32520 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
32521 formats, listed below.
32524 @item qXfer:auxv:read::@var{offset},@var{length}
32525 @anchor{qXfer auxiliary vector read}
32526 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
32527 auxiliary vector}. Note @var{annex} must be empty.
32529 This packet is not probed by default; the remote stub must request it,
32530 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32532 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
32533 @anchor{qXfer target description read}
32534 Access the @dfn{target description}. @xref{Target Descriptions}. The
32535 annex specifies which XML document to access. The main description is
32536 always loaded from the @samp{target.xml} annex.
32538 This packet is not probed by default; the remote stub must request it,
32539 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32541 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
32542 @anchor{qXfer library list read}
32543 Access the target's list of loaded libraries. @xref{Library List Format}.
32544 The annex part of the generic @samp{qXfer} packet must be empty
32545 (@pxref{qXfer read}).
32547 Targets which maintain a list of libraries in the program's memory do
32548 not need to implement this packet; it is designed for platforms where
32549 the operating system manages the list of loaded libraries.
32551 This packet is not probed by default; the remote stub must request it,
32552 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32554 @item qXfer:memory-map:read::@var{offset},@var{length}
32555 @anchor{qXfer memory map read}
32556 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
32557 annex part of the generic @samp{qXfer} packet must be empty
32558 (@pxref{qXfer read}).
32560 This packet is not probed by default; the remote stub must request it,
32561 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32563 @item qXfer:sdata:read::@var{offset},@var{length}
32564 @anchor{qXfer sdata read}
32566 Read contents of the extra collected static tracepoint marker
32567 information. The annex part of the generic @samp{qXfer} packet must
32568 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
32571 This packet is not probed by default; the remote stub must request it,
32572 by supplying an appropriate @samp{qSupported} response
32573 (@pxref{qSupported}).
32575 @item qXfer:siginfo:read::@var{offset},@var{length}
32576 @anchor{qXfer siginfo read}
32577 Read contents of the extra signal information on the target
32578 system. The annex part of the generic @samp{qXfer} packet must be
32579 empty (@pxref{qXfer read}).
32581 This packet is not probed by default; the remote stub must request it,
32582 by supplying an appropriate @samp{qSupported} response
32583 (@pxref{qSupported}).
32585 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
32586 @anchor{qXfer spu read}
32587 Read contents of an @code{spufs} file on the target system. The
32588 annex specifies which file to read; it must be of the form
32589 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32590 in the target process, and @var{name} identifes the @code{spufs} file
32591 in that context to be accessed.
32593 This packet is not probed by default; the remote stub must request it,
32594 by supplying an appropriate @samp{qSupported} response
32595 (@pxref{qSupported}).
32597 @item qXfer:threads:read::@var{offset},@var{length}
32598 @anchor{qXfer threads read}
32599 Access the list of threads on target. @xref{Thread List Format}. The
32600 annex part of the generic @samp{qXfer} packet must be empty
32601 (@pxref{qXfer read}).
32603 This packet is not probed by default; the remote stub must request it,
32604 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32606 @item qXfer:osdata:read::@var{offset},@var{length}
32607 @anchor{qXfer osdata read}
32608 Access the target's @dfn{operating system information}.
32609 @xref{Operating System Information}.
32616 Data @var{data} (@pxref{Binary Data}) has been read from the
32617 target. There may be more data at a higher address (although
32618 it is permitted to return @samp{m} even for the last valid
32619 block of data, as long as at least one byte of data was read).
32620 @var{data} may have fewer bytes than the @var{length} in the
32624 Data @var{data} (@pxref{Binary Data}) has been read from the target.
32625 There is no more data to be read. @var{data} may have fewer bytes
32626 than the @var{length} in the request.
32629 The @var{offset} in the request is at the end of the data.
32630 There is no more data to be read.
32633 The request was malformed, or @var{annex} was invalid.
32636 The offset was invalid, or there was an error encountered reading the data.
32637 @var{nn} is a hex-encoded @code{errno} value.
32640 An empty reply indicates the @var{object} string was not recognized by
32641 the stub, or that the object does not support reading.
32644 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
32645 @cindex write data into object, remote request
32646 @anchor{qXfer write}
32647 Write uninterpreted bytes into the target's special data area
32648 identified by the keyword @var{object}, starting at @var{offset} bytes
32649 into the data. @var{data}@dots{} is the binary-encoded data
32650 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
32651 is specific to @var{object}; it can supply additional details about what data
32654 Here are the specific requests of this form defined so far. All
32655 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
32656 formats, listed below.
32659 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
32660 @anchor{qXfer siginfo write}
32661 Write @var{data} to the extra signal information on the target system.
32662 The annex part of the generic @samp{qXfer} packet must be
32663 empty (@pxref{qXfer write}).
32665 This packet is not probed by default; the remote stub must request it,
32666 by supplying an appropriate @samp{qSupported} response
32667 (@pxref{qSupported}).
32669 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
32670 @anchor{qXfer spu write}
32671 Write @var{data} to an @code{spufs} file on the target system. The
32672 annex specifies which file to write; it must be of the form
32673 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32674 in the target process, and @var{name} identifes the @code{spufs} file
32675 in that context to be accessed.
32677 This packet is not probed by default; the remote stub must request it,
32678 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32684 @var{nn} (hex encoded) is the number of bytes written.
32685 This may be fewer bytes than supplied in the request.
32688 The request was malformed, or @var{annex} was invalid.
32691 The offset was invalid, or there was an error encountered writing the data.
32692 @var{nn} is a hex-encoded @code{errno} value.
32695 An empty reply indicates the @var{object} string was not
32696 recognized by the stub, or that the object does not support writing.
32699 @item qXfer:@var{object}:@var{operation}:@dots{}
32700 Requests of this form may be added in the future. When a stub does
32701 not recognize the @var{object} keyword, or its support for
32702 @var{object} does not recognize the @var{operation} keyword, the stub
32703 must respond with an empty packet.
32705 @item qAttached:@var{pid}
32706 @cindex query attached, remote request
32707 @cindex @samp{qAttached} packet
32708 Return an indication of whether the remote server attached to an
32709 existing process or created a new process. When the multiprocess
32710 protocol extensions are supported (@pxref{multiprocess extensions}),
32711 @var{pid} is an integer in hexadecimal format identifying the target
32712 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
32713 the query packet will be simplified as @samp{qAttached}.
32715 This query is used, for example, to know whether the remote process
32716 should be detached or killed when a @value{GDBN} session is ended with
32717 the @code{quit} command.
32722 The remote server attached to an existing process.
32724 The remote server created a new process.
32726 A badly formed request or an error was encountered.
32731 @node Architecture-Specific Protocol Details
32732 @section Architecture-Specific Protocol Details
32734 This section describes how the remote protocol is applied to specific
32735 target architectures. Also see @ref{Standard Target Features}, for
32736 details of XML target descriptions for each architecture.
32740 @subsubsection Breakpoint Kinds
32742 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
32747 16-bit Thumb mode breakpoint.
32750 32-bit Thumb mode (Thumb-2) breakpoint.
32753 32-bit ARM mode breakpoint.
32759 @subsubsection Register Packet Format
32761 The following @code{g}/@code{G} packets have previously been defined.
32762 In the below, some thirty-two bit registers are transferred as
32763 sixty-four bits. Those registers should be zero/sign extended (which?)
32764 to fill the space allocated. Register bytes are transferred in target
32765 byte order. The two nibbles within a register byte are transferred
32766 most-significant - least-significant.
32772 All registers are transferred as thirty-two bit quantities in the order:
32773 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
32774 registers; fsr; fir; fp.
32778 All registers are transferred as sixty-four bit quantities (including
32779 thirty-two bit registers such as @code{sr}). The ordering is the same
32784 @node Tracepoint Packets
32785 @section Tracepoint Packets
32786 @cindex tracepoint packets
32787 @cindex packets, tracepoint
32789 Here we describe the packets @value{GDBN} uses to implement
32790 tracepoints (@pxref{Tracepoints}).
32794 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
32795 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
32796 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
32797 the tracepoint is disabled. @var{step} is the tracepoint's step
32798 count, and @var{pass} is its pass count. If an @samp{F} is present,
32799 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
32800 the number of bytes that the target should copy elsewhere to make room
32801 for the tracepoint. If an @samp{X} is present, it introduces a
32802 tracepoint condition, which consists of a hexadecimal length, followed
32803 by a comma and hex-encoded bytes, in a manner similar to action
32804 encodings as described below. If the trailing @samp{-} is present,
32805 further @samp{QTDP} packets will follow to specify this tracepoint's
32811 The packet was understood and carried out.
32813 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
32815 The packet was not recognized.
32818 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
32819 Define actions to be taken when a tracepoint is hit. @var{n} and
32820 @var{addr} must be the same as in the initial @samp{QTDP} packet for
32821 this tracepoint. This packet may only be sent immediately after
32822 another @samp{QTDP} packet that ended with a @samp{-}. If the
32823 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
32824 specifying more actions for this tracepoint.
32826 In the series of action packets for a given tracepoint, at most one
32827 can have an @samp{S} before its first @var{action}. If such a packet
32828 is sent, it and the following packets define ``while-stepping''
32829 actions. Any prior packets define ordinary actions --- that is, those
32830 taken when the tracepoint is first hit. If no action packet has an
32831 @samp{S}, then all the packets in the series specify ordinary
32832 tracepoint actions.
32834 The @samp{@var{action}@dots{}} portion of the packet is a series of
32835 actions, concatenated without separators. Each action has one of the
32841 Collect the registers whose bits are set in @var{mask}. @var{mask} is
32842 a hexadecimal number whose @var{i}'th bit is set if register number
32843 @var{i} should be collected. (The least significant bit is numbered
32844 zero.) Note that @var{mask} may be any number of digits long; it may
32845 not fit in a 32-bit word.
32847 @item M @var{basereg},@var{offset},@var{len}
32848 Collect @var{len} bytes of memory starting at the address in register
32849 number @var{basereg}, plus @var{offset}. If @var{basereg} is
32850 @samp{-1}, then the range has a fixed address: @var{offset} is the
32851 address of the lowest byte to collect. The @var{basereg},
32852 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
32853 values (the @samp{-1} value for @var{basereg} is a special case).
32855 @item X @var{len},@var{expr}
32856 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
32857 it directs. @var{expr} is an agent expression, as described in
32858 @ref{Agent Expressions}. Each byte of the expression is encoded as a
32859 two-digit hex number in the packet; @var{len} is the number of bytes
32860 in the expression (and thus one-half the number of hex digits in the
32865 Any number of actions may be packed together in a single @samp{QTDP}
32866 packet, as long as the packet does not exceed the maximum packet
32867 length (400 bytes, for many stubs). There may be only one @samp{R}
32868 action per tracepoint, and it must precede any @samp{M} or @samp{X}
32869 actions. Any registers referred to by @samp{M} and @samp{X} actions
32870 must be collected by a preceding @samp{R} action. (The
32871 ``while-stepping'' actions are treated as if they were attached to a
32872 separate tracepoint, as far as these restrictions are concerned.)
32877 The packet was understood and carried out.
32879 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
32881 The packet was not recognized.
32884 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
32885 @cindex @samp{QTDPsrc} packet
32886 Specify a source string of tracepoint @var{n} at address @var{addr}.
32887 This is useful to get accurate reproduction of the tracepoints
32888 originally downloaded at the beginning of the trace run. @var{type}
32889 is the name of the tracepoint part, such as @samp{cond} for the
32890 tracepoint's conditional expression (see below for a list of types), while
32891 @var{bytes} is the string, encoded in hexadecimal.
32893 @var{start} is the offset of the @var{bytes} within the overall source
32894 string, while @var{slen} is the total length of the source string.
32895 This is intended for handling source strings that are longer than will
32896 fit in a single packet.
32897 @c Add detailed example when this info is moved into a dedicated
32898 @c tracepoint descriptions section.
32900 The available string types are @samp{at} for the location,
32901 @samp{cond} for the conditional, and @samp{cmd} for an action command.
32902 @value{GDBN} sends a separate packet for each command in the action
32903 list, in the same order in which the commands are stored in the list.
32905 The target does not need to do anything with source strings except
32906 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
32909 Although this packet is optional, and @value{GDBN} will only send it
32910 if the target replies with @samp{TracepointSource} @xref{General
32911 Query Packets}, it makes both disconnected tracing and trace files
32912 much easier to use. Otherwise the user must be careful that the
32913 tracepoints in effect while looking at trace frames are identical to
32914 the ones in effect during the trace run; even a small discrepancy
32915 could cause @samp{tdump} not to work, or a particular trace frame not
32918 @item QTDV:@var{n}:@var{value}
32919 @cindex define trace state variable, remote request
32920 @cindex @samp{QTDV} packet
32921 Create a new trace state variable, number @var{n}, with an initial
32922 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
32923 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
32924 the option of not using this packet for initial values of zero; the
32925 target should simply create the trace state variables as they are
32926 mentioned in expressions.
32928 @item QTFrame:@var{n}
32929 Select the @var{n}'th tracepoint frame from the buffer, and use the
32930 register and memory contents recorded there to answer subsequent
32931 request packets from @value{GDBN}.
32933 A successful reply from the stub indicates that the stub has found the
32934 requested frame. The response is a series of parts, concatenated
32935 without separators, describing the frame we selected. Each part has
32936 one of the following forms:
32940 The selected frame is number @var{n} in the trace frame buffer;
32941 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
32942 was no frame matching the criteria in the request packet.
32945 The selected trace frame records a hit of tracepoint number @var{t};
32946 @var{t} is a hexadecimal number.
32950 @item QTFrame:pc:@var{addr}
32951 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32952 currently selected frame whose PC is @var{addr};
32953 @var{addr} is a hexadecimal number.
32955 @item QTFrame:tdp:@var{t}
32956 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32957 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
32958 is a hexadecimal number.
32960 @item QTFrame:range:@var{start}:@var{end}
32961 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32962 currently selected frame whose PC is between @var{start} (inclusive)
32963 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
32966 @item QTFrame:outside:@var{start}:@var{end}
32967 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
32968 frame @emph{outside} the given range of addresses (exclusive).
32971 Begin the tracepoint experiment. Begin collecting data from
32972 tracepoint hits in the trace frame buffer. This packet supports the
32973 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
32974 instruction reply packet}).
32977 End the tracepoint experiment. Stop collecting trace frames.
32980 Clear the table of tracepoints, and empty the trace frame buffer.
32982 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
32983 Establish the given ranges of memory as ``transparent''. The stub
32984 will answer requests for these ranges from memory's current contents,
32985 if they were not collected as part of the tracepoint hit.
32987 @value{GDBN} uses this to mark read-only regions of memory, like those
32988 containing program code. Since these areas never change, they should
32989 still have the same contents they did when the tracepoint was hit, so
32990 there's no reason for the stub to refuse to provide their contents.
32992 @item QTDisconnected:@var{value}
32993 Set the choice to what to do with the tracing run when @value{GDBN}
32994 disconnects from the target. A @var{value} of 1 directs the target to
32995 continue the tracing run, while 0 tells the target to stop tracing if
32996 @value{GDBN} is no longer in the picture.
32999 Ask the stub if there is a trace experiment running right now.
33001 The reply has the form:
33005 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
33006 @var{running} is a single digit @code{1} if the trace is presently
33007 running, or @code{0} if not. It is followed by semicolon-separated
33008 optional fields that an agent may use to report additional status.
33012 If the trace is not running, the agent may report any of several
33013 explanations as one of the optional fields:
33018 No trace has been run yet.
33021 The trace was stopped by a user-originated stop command.
33024 The trace stopped because the trace buffer filled up.
33026 @item tdisconnected:0
33027 The trace stopped because @value{GDBN} disconnected from the target.
33029 @item tpasscount:@var{tpnum}
33030 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
33032 @item terror:@var{text}:@var{tpnum}
33033 The trace stopped because tracepoint @var{tpnum} had an error. The
33034 string @var{text} is available to describe the nature of the error
33035 (for instance, a divide by zero in the condition expression).
33036 @var{text} is hex encoded.
33039 The trace stopped for some other reason.
33043 Additional optional fields supply statistical and other information.
33044 Although not required, they are extremely useful for users monitoring
33045 the progress of a trace run. If a trace has stopped, and these
33046 numbers are reported, they must reflect the state of the just-stopped
33051 @item tframes:@var{n}
33052 The number of trace frames in the buffer.
33054 @item tcreated:@var{n}
33055 The total number of trace frames created during the run. This may
33056 be larger than the trace frame count, if the buffer is circular.
33058 @item tsize:@var{n}
33059 The total size of the trace buffer, in bytes.
33061 @item tfree:@var{n}
33062 The number of bytes still unused in the buffer.
33064 @item circular:@var{n}
33065 The value of the circular trace buffer flag. @code{1} means that the
33066 trace buffer is circular and old trace frames will be discarded if
33067 necessary to make room, @code{0} means that the trace buffer is linear
33070 @item disconn:@var{n}
33071 The value of the disconnected tracing flag. @code{1} means that
33072 tracing will continue after @value{GDBN} disconnects, @code{0} means
33073 that the trace run will stop.
33077 @item qTV:@var{var}
33078 @cindex trace state variable value, remote request
33079 @cindex @samp{qTV} packet
33080 Ask the stub for the value of the trace state variable number @var{var}.
33085 The value of the variable is @var{value}. This will be the current
33086 value of the variable if the user is examining a running target, or a
33087 saved value if the variable was collected in the trace frame that the
33088 user is looking at. Note that multiple requests may result in
33089 different reply values, such as when requesting values while the
33090 program is running.
33093 The value of the variable is unknown. This would occur, for example,
33094 if the user is examining a trace frame in which the requested variable
33100 These packets request data about tracepoints that are being used by
33101 the target. @value{GDBN} sends @code{qTfP} to get the first piece
33102 of data, and multiple @code{qTsP} to get additional pieces. Replies
33103 to these packets generally take the form of the @code{QTDP} packets
33104 that define tracepoints. (FIXME add detailed syntax)
33108 These packets request data about trace state variables that are on the
33109 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
33110 and multiple @code{qTsV} to get additional variables. Replies to
33111 these packets follow the syntax of the @code{QTDV} packets that define
33112 trace state variables.
33116 These packets request data about static tracepoint markers that exist
33117 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
33118 first piece of data, and multiple @code{qTsSTM} to get additional
33119 pieces. Replies to these packets take the following form:
33123 @item m @var{address}:@var{id}:@var{extra}
33125 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
33126 a comma-separated list of markers
33128 (lower case letter @samp{L}) denotes end of list.
33130 An error occurred. @var{nn} are hex digits.
33132 An empty reply indicates that the request is not supported by the
33136 @var{address} is encoded in hex.
33137 @var{id} and @var{extra} are strings encoded in hex.
33139 In response to each query, the target will reply with a list of one or
33140 more markers, separated by commas. @value{GDBN} will respond to each
33141 reply with a request for more markers (using the @samp{qs} form of the
33142 query), until the target responds with @samp{l} (lower-case ell, for
33145 @item qTSTMat:@var{address}
33146 This packets requests data about static tracepoint markers in the
33147 target program at @var{address}. Replies to this packet follow the
33148 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
33149 tracepoint markers.
33151 @item QTSave:@var{filename}
33152 This packet directs the target to save trace data to the file name
33153 @var{filename} in the target's filesystem. @var{filename} is encoded
33154 as a hex string; the interpretation of the file name (relative vs
33155 absolute, wild cards, etc) is up to the target.
33157 @item qTBuffer:@var{offset},@var{len}
33158 Return up to @var{len} bytes of the current contents of trace buffer,
33159 starting at @var{offset}. The trace buffer is treated as if it were
33160 a contiguous collection of traceframes, as per the trace file format.
33161 The reply consists as many hex-encoded bytes as the target can deliver
33162 in a packet; it is not an error to return fewer than were asked for.
33163 A reply consisting of just @code{l} indicates that no bytes are
33166 @item QTBuffer:circular:@var{value}
33167 This packet directs the target to use a circular trace buffer if
33168 @var{value} is 1, or a linear buffer if the value is 0.
33172 @subsection Relocate instruction reply packet
33173 When installing fast tracepoints in memory, the target may need to
33174 relocate the instruction currently at the tracepoint address to a
33175 different address in memory. For most instructions, a simple copy is
33176 enough, but, for example, call instructions that implicitly push the
33177 return address on the stack, and relative branches or other
33178 PC-relative instructions require offset adjustment, so that the effect
33179 of executing the instruction at a different address is the same as if
33180 it had executed in the original location.
33182 In response to several of the tracepoint packets, the target may also
33183 respond with a number of intermediate @samp{qRelocInsn} request
33184 packets before the final result packet, to have @value{GDBN} handle
33185 this relocation operation. If a packet supports this mechanism, its
33186 documentation will explicitly say so. See for example the above
33187 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
33188 format of the request is:
33191 @item qRelocInsn:@var{from};@var{to}
33193 This requests @value{GDBN} to copy instruction at address @var{from}
33194 to address @var{to}, possibly adjusted so that executing the
33195 instruction at @var{to} has the same effect as executing it at
33196 @var{from}. @value{GDBN} writes the adjusted instruction to target
33197 memory starting at @var{to}.
33202 @item qRelocInsn:@var{adjusted_size}
33203 Informs the stub the relocation is complete. @var{adjusted_size} is
33204 the length in bytes of resulting relocated instruction sequence.
33206 A badly formed request was detected, or an error was encountered while
33207 relocating the instruction.
33210 @node Host I/O Packets
33211 @section Host I/O Packets
33212 @cindex Host I/O, remote protocol
33213 @cindex file transfer, remote protocol
33215 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
33216 operations on the far side of a remote link. For example, Host I/O is
33217 used to upload and download files to a remote target with its own
33218 filesystem. Host I/O uses the same constant values and data structure
33219 layout as the target-initiated File-I/O protocol. However, the
33220 Host I/O packets are structured differently. The target-initiated
33221 protocol relies on target memory to store parameters and buffers.
33222 Host I/O requests are initiated by @value{GDBN}, and the
33223 target's memory is not involved. @xref{File-I/O Remote Protocol
33224 Extension}, for more details on the target-initiated protocol.
33226 The Host I/O request packets all encode a single operation along with
33227 its arguments. They have this format:
33231 @item vFile:@var{operation}: @var{parameter}@dots{}
33232 @var{operation} is the name of the particular request; the target
33233 should compare the entire packet name up to the second colon when checking
33234 for a supported operation. The format of @var{parameter} depends on
33235 the operation. Numbers are always passed in hexadecimal. Negative
33236 numbers have an explicit minus sign (i.e.@: two's complement is not
33237 used). Strings (e.g.@: filenames) are encoded as a series of
33238 hexadecimal bytes. The last argument to a system call may be a
33239 buffer of escaped binary data (@pxref{Binary Data}).
33243 The valid responses to Host I/O packets are:
33247 @item F @var{result} [, @var{errno}] [; @var{attachment}]
33248 @var{result} is the integer value returned by this operation, usually
33249 non-negative for success and -1 for errors. If an error has occured,
33250 @var{errno} will be included in the result. @var{errno} will have a
33251 value defined by the File-I/O protocol (@pxref{Errno Values}). For
33252 operations which return data, @var{attachment} supplies the data as a
33253 binary buffer. Binary buffers in response packets are escaped in the
33254 normal way (@pxref{Binary Data}). See the individual packet
33255 documentation for the interpretation of @var{result} and
33259 An empty response indicates that this operation is not recognized.
33263 These are the supported Host I/O operations:
33266 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
33267 Open a file at @var{pathname} and return a file descriptor for it, or
33268 return -1 if an error occurs. @var{pathname} is a string,
33269 @var{flags} is an integer indicating a mask of open flags
33270 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
33271 of mode bits to use if the file is created (@pxref{mode_t Values}).
33272 @xref{open}, for details of the open flags and mode values.
33274 @item vFile:close: @var{fd}
33275 Close the open file corresponding to @var{fd} and return 0, or
33276 -1 if an error occurs.
33278 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
33279 Read data from the open file corresponding to @var{fd}. Up to
33280 @var{count} bytes will be read from the file, starting at @var{offset}
33281 relative to the start of the file. The target may read fewer bytes;
33282 common reasons include packet size limits and an end-of-file
33283 condition. The number of bytes read is returned. Zero should only be
33284 returned for a successful read at the end of the file, or if
33285 @var{count} was zero.
33287 The data read should be returned as a binary attachment on success.
33288 If zero bytes were read, the response should include an empty binary
33289 attachment (i.e.@: a trailing semicolon). The return value is the
33290 number of target bytes read; the binary attachment may be longer if
33291 some characters were escaped.
33293 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
33294 Write @var{data} (a binary buffer) to the open file corresponding
33295 to @var{fd}. Start the write at @var{offset} from the start of the
33296 file. Unlike many @code{write} system calls, there is no
33297 separate @var{count} argument; the length of @var{data} in the
33298 packet is used. @samp{vFile:write} returns the number of bytes written,
33299 which may be shorter than the length of @var{data}, or -1 if an
33302 @item vFile:unlink: @var{pathname}
33303 Delete the file at @var{pathname} on the target. Return 0,
33304 or -1 if an error occurs. @var{pathname} is a string.
33309 @section Interrupts
33310 @cindex interrupts (remote protocol)
33312 When a program on the remote target is running, @value{GDBN} may
33313 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
33314 a @code{BREAK} followed by @code{g},
33315 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
33317 The precise meaning of @code{BREAK} is defined by the transport
33318 mechanism and may, in fact, be undefined. @value{GDBN} does not
33319 currently define a @code{BREAK} mechanism for any of the network
33320 interfaces except for TCP, in which case @value{GDBN} sends the
33321 @code{telnet} BREAK sequence.
33323 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
33324 transport mechanisms. It is represented by sending the single byte
33325 @code{0x03} without any of the usual packet overhead described in
33326 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
33327 transmitted as part of a packet, it is considered to be packet data
33328 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
33329 (@pxref{X packet}), used for binary downloads, may include an unescaped
33330 @code{0x03} as part of its packet.
33332 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
33333 When Linux kernel receives this sequence from serial port,
33334 it stops execution and connects to gdb.
33336 Stubs are not required to recognize these interrupt mechanisms and the
33337 precise meaning associated with receipt of the interrupt is
33338 implementation defined. If the target supports debugging of multiple
33339 threads and/or processes, it should attempt to interrupt all
33340 currently-executing threads and processes.
33341 If the stub is successful at interrupting the
33342 running program, it should send one of the stop
33343 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
33344 of successfully stopping the program in all-stop mode, and a stop reply
33345 for each stopped thread in non-stop mode.
33346 Interrupts received while the
33347 program is stopped are discarded.
33349 @node Notification Packets
33350 @section Notification Packets
33351 @cindex notification packets
33352 @cindex packets, notification
33354 The @value{GDBN} remote serial protocol includes @dfn{notifications},
33355 packets that require no acknowledgment. Both the GDB and the stub
33356 may send notifications (although the only notifications defined at
33357 present are sent by the stub). Notifications carry information
33358 without incurring the round-trip latency of an acknowledgment, and so
33359 are useful for low-impact communications where occasional packet loss
33362 A notification packet has the form @samp{% @var{data} #
33363 @var{checksum}}, where @var{data} is the content of the notification,
33364 and @var{checksum} is a checksum of @var{data}, computed and formatted
33365 as for ordinary @value{GDBN} packets. A notification's @var{data}
33366 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
33367 receiving a notification, the recipient sends no @samp{+} or @samp{-}
33368 to acknowledge the notification's receipt or to report its corruption.
33370 Every notification's @var{data} begins with a name, which contains no
33371 colon characters, followed by a colon character.
33373 Recipients should silently ignore corrupted notifications and
33374 notifications they do not understand. Recipients should restart
33375 timeout periods on receipt of a well-formed notification, whether or
33376 not they understand it.
33378 Senders should only send the notifications described here when this
33379 protocol description specifies that they are permitted. In the
33380 future, we may extend the protocol to permit existing notifications in
33381 new contexts; this rule helps older senders avoid confusing newer
33384 (Older versions of @value{GDBN} ignore bytes received until they see
33385 the @samp{$} byte that begins an ordinary packet, so new stubs may
33386 transmit notifications without fear of confusing older clients. There
33387 are no notifications defined for @value{GDBN} to send at the moment, but we
33388 assume that most older stubs would ignore them, as well.)
33390 The following notification packets from the stub to @value{GDBN} are
33394 @item Stop: @var{reply}
33395 Report an asynchronous stop event in non-stop mode.
33396 The @var{reply} has the form of a stop reply, as
33397 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
33398 for information on how these notifications are acknowledged by
33402 @node Remote Non-Stop
33403 @section Remote Protocol Support for Non-Stop Mode
33405 @value{GDBN}'s remote protocol supports non-stop debugging of
33406 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
33407 supports non-stop mode, it should report that to @value{GDBN} by including
33408 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
33410 @value{GDBN} typically sends a @samp{QNonStop} packet only when
33411 establishing a new connection with the stub. Entering non-stop mode
33412 does not alter the state of any currently-running threads, but targets
33413 must stop all threads in any already-attached processes when entering
33414 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
33415 probe the target state after a mode change.
33417 In non-stop mode, when an attached process encounters an event that
33418 would otherwise be reported with a stop reply, it uses the
33419 asynchronous notification mechanism (@pxref{Notification Packets}) to
33420 inform @value{GDBN}. In contrast to all-stop mode, where all threads
33421 in all processes are stopped when a stop reply is sent, in non-stop
33422 mode only the thread reporting the stop event is stopped. That is,
33423 when reporting a @samp{S} or @samp{T} response to indicate completion
33424 of a step operation, hitting a breakpoint, or a fault, only the
33425 affected thread is stopped; any other still-running threads continue
33426 to run. When reporting a @samp{W} or @samp{X} response, all running
33427 threads belonging to other attached processes continue to run.
33429 Only one stop reply notification at a time may be pending; if
33430 additional stop events occur before @value{GDBN} has acknowledged the
33431 previous notification, they must be queued by the stub for later
33432 synchronous transmission in response to @samp{vStopped} packets from
33433 @value{GDBN}. Because the notification mechanism is unreliable,
33434 the stub is permitted to resend a stop reply notification
33435 if it believes @value{GDBN} may not have received it. @value{GDBN}
33436 ignores additional stop reply notifications received before it has
33437 finished processing a previous notification and the stub has completed
33438 sending any queued stop events.
33440 Otherwise, @value{GDBN} must be prepared to receive a stop reply
33441 notification at any time. Specifically, they may appear when
33442 @value{GDBN} is not otherwise reading input from the stub, or when
33443 @value{GDBN} is expecting to read a normal synchronous response or a
33444 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
33445 Notification packets are distinct from any other communication from
33446 the stub so there is no ambiguity.
33448 After receiving a stop reply notification, @value{GDBN} shall
33449 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
33450 as a regular, synchronous request to the stub. Such acknowledgment
33451 is not required to happen immediately, as @value{GDBN} is permitted to
33452 send other, unrelated packets to the stub first, which the stub should
33455 Upon receiving a @samp{vStopped} packet, if the stub has other queued
33456 stop events to report to @value{GDBN}, it shall respond by sending a
33457 normal stop reply response. @value{GDBN} shall then send another
33458 @samp{vStopped} packet to solicit further responses; again, it is
33459 permitted to send other, unrelated packets as well which the stub
33460 should process normally.
33462 If the stub receives a @samp{vStopped} packet and there are no
33463 additional stop events to report, the stub shall return an @samp{OK}
33464 response. At this point, if further stop events occur, the stub shall
33465 send a new stop reply notification, @value{GDBN} shall accept the
33466 notification, and the process shall be repeated.
33468 In non-stop mode, the target shall respond to the @samp{?} packet as
33469 follows. First, any incomplete stop reply notification/@samp{vStopped}
33470 sequence in progress is abandoned. The target must begin a new
33471 sequence reporting stop events for all stopped threads, whether or not
33472 it has previously reported those events to @value{GDBN}. The first
33473 stop reply is sent as a synchronous reply to the @samp{?} packet, and
33474 subsequent stop replies are sent as responses to @samp{vStopped} packets
33475 using the mechanism described above. The target must not send
33476 asynchronous stop reply notifications until the sequence is complete.
33477 If all threads are running when the target receives the @samp{?} packet,
33478 or if the target is not attached to any process, it shall respond
33481 @node Packet Acknowledgment
33482 @section Packet Acknowledgment
33484 @cindex acknowledgment, for @value{GDBN} remote
33485 @cindex packet acknowledgment, for @value{GDBN} remote
33486 By default, when either the host or the target machine receives a packet,
33487 the first response expected is an acknowledgment: either @samp{+} (to indicate
33488 the package was received correctly) or @samp{-} (to request retransmission).
33489 This mechanism allows the @value{GDBN} remote protocol to operate over
33490 unreliable transport mechanisms, such as a serial line.
33492 In cases where the transport mechanism is itself reliable (such as a pipe or
33493 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
33494 It may be desirable to disable them in that case to reduce communication
33495 overhead, or for other reasons. This can be accomplished by means of the
33496 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
33498 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
33499 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
33500 and response format still includes the normal checksum, as described in
33501 @ref{Overview}, but the checksum may be ignored by the receiver.
33503 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
33504 no-acknowledgment mode, it should report that to @value{GDBN}
33505 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
33506 @pxref{qSupported}.
33507 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
33508 disabled via the @code{set remote noack-packet off} command
33509 (@pxref{Remote Configuration}),
33510 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
33511 Only then may the stub actually turn off packet acknowledgments.
33512 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
33513 response, which can be safely ignored by the stub.
33515 Note that @code{set remote noack-packet} command only affects negotiation
33516 between @value{GDBN} and the stub when subsequent connections are made;
33517 it does not affect the protocol acknowledgment state for any current
33519 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
33520 new connection is established,
33521 there is also no protocol request to re-enable the acknowledgments
33522 for the current connection, once disabled.
33527 Example sequence of a target being re-started. Notice how the restart
33528 does not get any direct output:
33533 @emph{target restarts}
33536 <- @code{T001:1234123412341234}
33540 Example sequence of a target being stepped by a single instruction:
33543 -> @code{G1445@dots{}}
33548 <- @code{T001:1234123412341234}
33552 <- @code{1455@dots{}}
33556 @node File-I/O Remote Protocol Extension
33557 @section File-I/O Remote Protocol Extension
33558 @cindex File-I/O remote protocol extension
33561 * File-I/O Overview::
33562 * Protocol Basics::
33563 * The F Request Packet::
33564 * The F Reply Packet::
33565 * The Ctrl-C Message::
33567 * List of Supported Calls::
33568 * Protocol-specific Representation of Datatypes::
33570 * File-I/O Examples::
33573 @node File-I/O Overview
33574 @subsection File-I/O Overview
33575 @cindex file-i/o overview
33577 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
33578 target to use the host's file system and console I/O to perform various
33579 system calls. System calls on the target system are translated into a
33580 remote protocol packet to the host system, which then performs the needed
33581 actions and returns a response packet to the target system.
33582 This simulates file system operations even on targets that lack file systems.
33584 The protocol is defined to be independent of both the host and target systems.
33585 It uses its own internal representation of datatypes and values. Both
33586 @value{GDBN} and the target's @value{GDBN} stub are responsible for
33587 translating the system-dependent value representations into the internal
33588 protocol representations when data is transmitted.
33590 The communication is synchronous. A system call is possible only when
33591 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
33592 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
33593 the target is stopped to allow deterministic access to the target's
33594 memory. Therefore File-I/O is not interruptible by target signals. On
33595 the other hand, it is possible to interrupt File-I/O by a user interrupt
33596 (@samp{Ctrl-C}) within @value{GDBN}.
33598 The target's request to perform a host system call does not finish
33599 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
33600 after finishing the system call, the target returns to continuing the
33601 previous activity (continue, step). No additional continue or step
33602 request from @value{GDBN} is required.
33605 (@value{GDBP}) continue
33606 <- target requests 'system call X'
33607 target is stopped, @value{GDBN} executes system call
33608 -> @value{GDBN} returns result
33609 ... target continues, @value{GDBN} returns to wait for the target
33610 <- target hits breakpoint and sends a Txx packet
33613 The protocol only supports I/O on the console and to regular files on
33614 the host file system. Character or block special devices, pipes,
33615 named pipes, sockets or any other communication method on the host
33616 system are not supported by this protocol.
33618 File I/O is not supported in non-stop mode.
33620 @node Protocol Basics
33621 @subsection Protocol Basics
33622 @cindex protocol basics, file-i/o
33624 The File-I/O protocol uses the @code{F} packet as the request as well
33625 as reply packet. Since a File-I/O system call can only occur when
33626 @value{GDBN} is waiting for a response from the continuing or stepping target,
33627 the File-I/O request is a reply that @value{GDBN} has to expect as a result
33628 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
33629 This @code{F} packet contains all information needed to allow @value{GDBN}
33630 to call the appropriate host system call:
33634 A unique identifier for the requested system call.
33637 All parameters to the system call. Pointers are given as addresses
33638 in the target memory address space. Pointers to strings are given as
33639 pointer/length pair. Numerical values are given as they are.
33640 Numerical control flags are given in a protocol-specific representation.
33644 At this point, @value{GDBN} has to perform the following actions.
33648 If the parameters include pointer values to data needed as input to a
33649 system call, @value{GDBN} requests this data from the target with a
33650 standard @code{m} packet request. This additional communication has to be
33651 expected by the target implementation and is handled as any other @code{m}
33655 @value{GDBN} translates all value from protocol representation to host
33656 representation as needed. Datatypes are coerced into the host types.
33659 @value{GDBN} calls the system call.
33662 It then coerces datatypes back to protocol representation.
33665 If the system call is expected to return data in buffer space specified
33666 by pointer parameters to the call, the data is transmitted to the
33667 target using a @code{M} or @code{X} packet. This packet has to be expected
33668 by the target implementation and is handled as any other @code{M} or @code{X}
33673 Eventually @value{GDBN} replies with another @code{F} packet which contains all
33674 necessary information for the target to continue. This at least contains
33681 @code{errno}, if has been changed by the system call.
33688 After having done the needed type and value coercion, the target continues
33689 the latest continue or step action.
33691 @node The F Request Packet
33692 @subsection The @code{F} Request Packet
33693 @cindex file-i/o request packet
33694 @cindex @code{F} request packet
33696 The @code{F} request packet has the following format:
33699 @item F@var{call-id},@var{parameter@dots{}}
33701 @var{call-id} is the identifier to indicate the host system call to be called.
33702 This is just the name of the function.
33704 @var{parameter@dots{}} are the parameters to the system call.
33705 Parameters are hexadecimal integer values, either the actual values in case
33706 of scalar datatypes, pointers to target buffer space in case of compound
33707 datatypes and unspecified memory areas, or pointer/length pairs in case
33708 of string parameters. These are appended to the @var{call-id} as a
33709 comma-delimited list. All values are transmitted in ASCII
33710 string representation, pointer/length pairs separated by a slash.
33716 @node The F Reply Packet
33717 @subsection The @code{F} Reply Packet
33718 @cindex file-i/o reply packet
33719 @cindex @code{F} reply packet
33721 The @code{F} reply packet has the following format:
33725 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
33727 @var{retcode} is the return code of the system call as hexadecimal value.
33729 @var{errno} is the @code{errno} set by the call, in protocol-specific
33731 This parameter can be omitted if the call was successful.
33733 @var{Ctrl-C flag} is only sent if the user requested a break. In this
33734 case, @var{errno} must be sent as well, even if the call was successful.
33735 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
33742 or, if the call was interrupted before the host call has been performed:
33749 assuming 4 is the protocol-specific representation of @code{EINTR}.
33754 @node The Ctrl-C Message
33755 @subsection The @samp{Ctrl-C} Message
33756 @cindex ctrl-c message, in file-i/o protocol
33758 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
33759 reply packet (@pxref{The F Reply Packet}),
33760 the target should behave as if it had
33761 gotten a break message. The meaning for the target is ``system call
33762 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
33763 (as with a break message) and return to @value{GDBN} with a @code{T02}
33766 It's important for the target to know in which
33767 state the system call was interrupted. There are two possible cases:
33771 The system call hasn't been performed on the host yet.
33774 The system call on the host has been finished.
33778 These two states can be distinguished by the target by the value of the
33779 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
33780 call hasn't been performed. This is equivalent to the @code{EINTR} handling
33781 on POSIX systems. In any other case, the target may presume that the
33782 system call has been finished --- successfully or not --- and should behave
33783 as if the break message arrived right after the system call.
33785 @value{GDBN} must behave reliably. If the system call has not been called
33786 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
33787 @code{errno} in the packet. If the system call on the host has been finished
33788 before the user requests a break, the full action must be finished by
33789 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
33790 The @code{F} packet may only be sent when either nothing has happened
33791 or the full action has been completed.
33794 @subsection Console I/O
33795 @cindex console i/o as part of file-i/o
33797 By default and if not explicitly closed by the target system, the file
33798 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
33799 on the @value{GDBN} console is handled as any other file output operation
33800 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
33801 by @value{GDBN} so that after the target read request from file descriptor
33802 0 all following typing is buffered until either one of the following
33807 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
33809 system call is treated as finished.
33812 The user presses @key{RET}. This is treated as end of input with a trailing
33816 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
33817 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
33821 If the user has typed more characters than fit in the buffer given to
33822 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
33823 either another @code{read(0, @dots{})} is requested by the target, or debugging
33824 is stopped at the user's request.
33827 @node List of Supported Calls
33828 @subsection List of Supported Calls
33829 @cindex list of supported file-i/o calls
33846 @unnumberedsubsubsec open
33847 @cindex open, file-i/o system call
33852 int open(const char *pathname, int flags);
33853 int open(const char *pathname, int flags, mode_t mode);
33857 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
33860 @var{flags} is the bitwise @code{OR} of the following values:
33864 If the file does not exist it will be created. The host
33865 rules apply as far as file ownership and time stamps
33869 When used with @code{O_CREAT}, if the file already exists it is
33870 an error and open() fails.
33873 If the file already exists and the open mode allows
33874 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
33875 truncated to zero length.
33878 The file is opened in append mode.
33881 The file is opened for reading only.
33884 The file is opened for writing only.
33887 The file is opened for reading and writing.
33891 Other bits are silently ignored.
33895 @var{mode} is the bitwise @code{OR} of the following values:
33899 User has read permission.
33902 User has write permission.
33905 Group has read permission.
33908 Group has write permission.
33911 Others have read permission.
33914 Others have write permission.
33918 Other bits are silently ignored.
33921 @item Return value:
33922 @code{open} returns the new file descriptor or -1 if an error
33929 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
33932 @var{pathname} refers to a directory.
33935 The requested access is not allowed.
33938 @var{pathname} was too long.
33941 A directory component in @var{pathname} does not exist.
33944 @var{pathname} refers to a device, pipe, named pipe or socket.
33947 @var{pathname} refers to a file on a read-only filesystem and
33948 write access was requested.
33951 @var{pathname} is an invalid pointer value.
33954 No space on device to create the file.
33957 The process already has the maximum number of files open.
33960 The limit on the total number of files open on the system
33964 The call was interrupted by the user.
33970 @unnumberedsubsubsec close
33971 @cindex close, file-i/o system call
33980 @samp{Fclose,@var{fd}}
33982 @item Return value:
33983 @code{close} returns zero on success, or -1 if an error occurred.
33989 @var{fd} isn't a valid open file descriptor.
33992 The call was interrupted by the user.
33998 @unnumberedsubsubsec read
33999 @cindex read, file-i/o system call
34004 int read(int fd, void *buf, unsigned int count);
34008 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
34010 @item Return value:
34011 On success, the number of bytes read is returned.
34012 Zero indicates end of file. If count is zero, read
34013 returns zero as well. On error, -1 is returned.
34019 @var{fd} is not a valid file descriptor or is not open for
34023 @var{bufptr} is an invalid pointer value.
34026 The call was interrupted by the user.
34032 @unnumberedsubsubsec write
34033 @cindex write, file-i/o system call
34038 int write(int fd, const void *buf, unsigned int count);
34042 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
34044 @item Return value:
34045 On success, the number of bytes written are returned.
34046 Zero indicates nothing was written. On error, -1
34053 @var{fd} is not a valid file descriptor or is not open for
34057 @var{bufptr} is an invalid pointer value.
34060 An attempt was made to write a file that exceeds the
34061 host-specific maximum file size allowed.
34064 No space on device to write the data.
34067 The call was interrupted by the user.
34073 @unnumberedsubsubsec lseek
34074 @cindex lseek, file-i/o system call
34079 long lseek (int fd, long offset, int flag);
34083 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
34085 @var{flag} is one of:
34089 The offset is set to @var{offset} bytes.
34092 The offset is set to its current location plus @var{offset}
34096 The offset is set to the size of the file plus @var{offset}
34100 @item Return value:
34101 On success, the resulting unsigned offset in bytes from
34102 the beginning of the file is returned. Otherwise, a
34103 value of -1 is returned.
34109 @var{fd} is not a valid open file descriptor.
34112 @var{fd} is associated with the @value{GDBN} console.
34115 @var{flag} is not a proper value.
34118 The call was interrupted by the user.
34124 @unnumberedsubsubsec rename
34125 @cindex rename, file-i/o system call
34130 int rename(const char *oldpath, const char *newpath);
34134 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
34136 @item Return value:
34137 On success, zero is returned. On error, -1 is returned.
34143 @var{newpath} is an existing directory, but @var{oldpath} is not a
34147 @var{newpath} is a non-empty directory.
34150 @var{oldpath} or @var{newpath} is a directory that is in use by some
34154 An attempt was made to make a directory a subdirectory
34158 A component used as a directory in @var{oldpath} or new
34159 path is not a directory. Or @var{oldpath} is a directory
34160 and @var{newpath} exists but is not a directory.
34163 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
34166 No access to the file or the path of the file.
34170 @var{oldpath} or @var{newpath} was too long.
34173 A directory component in @var{oldpath} or @var{newpath} does not exist.
34176 The file is on a read-only filesystem.
34179 The device containing the file has no room for the new
34183 The call was interrupted by the user.
34189 @unnumberedsubsubsec unlink
34190 @cindex unlink, file-i/o system call
34195 int unlink(const char *pathname);
34199 @samp{Funlink,@var{pathnameptr}/@var{len}}
34201 @item Return value:
34202 On success, zero is returned. On error, -1 is returned.
34208 No access to the file or the path of the file.
34211 The system does not allow unlinking of directories.
34214 The file @var{pathname} cannot be unlinked because it's
34215 being used by another process.
34218 @var{pathnameptr} is an invalid pointer value.
34221 @var{pathname} was too long.
34224 A directory component in @var{pathname} does not exist.
34227 A component of the path is not a directory.
34230 The file is on a read-only filesystem.
34233 The call was interrupted by the user.
34239 @unnumberedsubsubsec stat/fstat
34240 @cindex fstat, file-i/o system call
34241 @cindex stat, file-i/o system call
34246 int stat(const char *pathname, struct stat *buf);
34247 int fstat(int fd, struct stat *buf);
34251 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
34252 @samp{Ffstat,@var{fd},@var{bufptr}}
34254 @item Return value:
34255 On success, zero is returned. On error, -1 is returned.
34261 @var{fd} is not a valid open file.
34264 A directory component in @var{pathname} does not exist or the
34265 path is an empty string.
34268 A component of the path is not a directory.
34271 @var{pathnameptr} is an invalid pointer value.
34274 No access to the file or the path of the file.
34277 @var{pathname} was too long.
34280 The call was interrupted by the user.
34286 @unnumberedsubsubsec gettimeofday
34287 @cindex gettimeofday, file-i/o system call
34292 int gettimeofday(struct timeval *tv, void *tz);
34296 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
34298 @item Return value:
34299 On success, 0 is returned, -1 otherwise.
34305 @var{tz} is a non-NULL pointer.
34308 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
34314 @unnumberedsubsubsec isatty
34315 @cindex isatty, file-i/o system call
34320 int isatty(int fd);
34324 @samp{Fisatty,@var{fd}}
34326 @item Return value:
34327 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
34333 The call was interrupted by the user.
34338 Note that the @code{isatty} call is treated as a special case: it returns
34339 1 to the target if the file descriptor is attached
34340 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
34341 would require implementing @code{ioctl} and would be more complex than
34346 @unnumberedsubsubsec system
34347 @cindex system, file-i/o system call
34352 int system(const char *command);
34356 @samp{Fsystem,@var{commandptr}/@var{len}}
34358 @item Return value:
34359 If @var{len} is zero, the return value indicates whether a shell is
34360 available. A zero return value indicates a shell is not available.
34361 For non-zero @var{len}, the value returned is -1 on error and the
34362 return status of the command otherwise. Only the exit status of the
34363 command is returned, which is extracted from the host's @code{system}
34364 return value by calling @code{WEXITSTATUS(retval)}. In case
34365 @file{/bin/sh} could not be executed, 127 is returned.
34371 The call was interrupted by the user.
34376 @value{GDBN} takes over the full task of calling the necessary host calls
34377 to perform the @code{system} call. The return value of @code{system} on
34378 the host is simplified before it's returned
34379 to the target. Any termination signal information from the child process
34380 is discarded, and the return value consists
34381 entirely of the exit status of the called command.
34383 Due to security concerns, the @code{system} call is by default refused
34384 by @value{GDBN}. The user has to allow this call explicitly with the
34385 @code{set remote system-call-allowed 1} command.
34388 @item set remote system-call-allowed
34389 @kindex set remote system-call-allowed
34390 Control whether to allow the @code{system} calls in the File I/O
34391 protocol for the remote target. The default is zero (disabled).
34393 @item show remote system-call-allowed
34394 @kindex show remote system-call-allowed
34395 Show whether the @code{system} calls are allowed in the File I/O
34399 @node Protocol-specific Representation of Datatypes
34400 @subsection Protocol-specific Representation of Datatypes
34401 @cindex protocol-specific representation of datatypes, in file-i/o protocol
34404 * Integral Datatypes::
34406 * Memory Transfer::
34411 @node Integral Datatypes
34412 @unnumberedsubsubsec Integral Datatypes
34413 @cindex integral datatypes, in file-i/o protocol
34415 The integral datatypes used in the system calls are @code{int},
34416 @code{unsigned int}, @code{long}, @code{unsigned long},
34417 @code{mode_t}, and @code{time_t}.
34419 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
34420 implemented as 32 bit values in this protocol.
34422 @code{long} and @code{unsigned long} are implemented as 64 bit types.
34424 @xref{Limits}, for corresponding MIN and MAX values (similar to those
34425 in @file{limits.h}) to allow range checking on host and target.
34427 @code{time_t} datatypes are defined as seconds since the Epoch.
34429 All integral datatypes transferred as part of a memory read or write of a
34430 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
34433 @node Pointer Values
34434 @unnumberedsubsubsec Pointer Values
34435 @cindex pointer values, in file-i/o protocol
34437 Pointers to target data are transmitted as they are. An exception
34438 is made for pointers to buffers for which the length isn't
34439 transmitted as part of the function call, namely strings. Strings
34440 are transmitted as a pointer/length pair, both as hex values, e.g.@:
34447 which is a pointer to data of length 18 bytes at position 0x1aaf.
34448 The length is defined as the full string length in bytes, including
34449 the trailing null byte. For example, the string @code{"hello world"}
34450 at address 0x123456 is transmitted as
34456 @node Memory Transfer
34457 @unnumberedsubsubsec Memory Transfer
34458 @cindex memory transfer, in file-i/o protocol
34460 Structured data which is transferred using a memory read or write (for
34461 example, a @code{struct stat}) is expected to be in a protocol-specific format
34462 with all scalar multibyte datatypes being big endian. Translation to
34463 this representation needs to be done both by the target before the @code{F}
34464 packet is sent, and by @value{GDBN} before
34465 it transfers memory to the target. Transferred pointers to structured
34466 data should point to the already-coerced data at any time.
34470 @unnumberedsubsubsec struct stat
34471 @cindex struct stat, in file-i/o protocol
34473 The buffer of type @code{struct stat} used by the target and @value{GDBN}
34474 is defined as follows:
34478 unsigned int st_dev; /* device */
34479 unsigned int st_ino; /* inode */
34480 mode_t st_mode; /* protection */
34481 unsigned int st_nlink; /* number of hard links */
34482 unsigned int st_uid; /* user ID of owner */
34483 unsigned int st_gid; /* group ID of owner */
34484 unsigned int st_rdev; /* device type (if inode device) */
34485 unsigned long st_size; /* total size, in bytes */
34486 unsigned long st_blksize; /* blocksize for filesystem I/O */
34487 unsigned long st_blocks; /* number of blocks allocated */
34488 time_t st_atime; /* time of last access */
34489 time_t st_mtime; /* time of last modification */
34490 time_t st_ctime; /* time of last change */
34494 The integral datatypes conform to the definitions given in the
34495 appropriate section (see @ref{Integral Datatypes}, for details) so this
34496 structure is of size 64 bytes.
34498 The values of several fields have a restricted meaning and/or
34504 A value of 0 represents a file, 1 the console.
34507 No valid meaning for the target. Transmitted unchanged.
34510 Valid mode bits are described in @ref{Constants}. Any other
34511 bits have currently no meaning for the target.
34516 No valid meaning for the target. Transmitted unchanged.
34521 These values have a host and file system dependent
34522 accuracy. Especially on Windows hosts, the file system may not
34523 support exact timing values.
34526 The target gets a @code{struct stat} of the above representation and is
34527 responsible for coercing it to the target representation before
34530 Note that due to size differences between the host, target, and protocol
34531 representations of @code{struct stat} members, these members could eventually
34532 get truncated on the target.
34534 @node struct timeval
34535 @unnumberedsubsubsec struct timeval
34536 @cindex struct timeval, in file-i/o protocol
34538 The buffer of type @code{struct timeval} used by the File-I/O protocol
34539 is defined as follows:
34543 time_t tv_sec; /* second */
34544 long tv_usec; /* microsecond */
34548 The integral datatypes conform to the definitions given in the
34549 appropriate section (see @ref{Integral Datatypes}, for details) so this
34550 structure is of size 8 bytes.
34553 @subsection Constants
34554 @cindex constants, in file-i/o protocol
34556 The following values are used for the constants inside of the
34557 protocol. @value{GDBN} and target are responsible for translating these
34558 values before and after the call as needed.
34569 @unnumberedsubsubsec Open Flags
34570 @cindex open flags, in file-i/o protocol
34572 All values are given in hexadecimal representation.
34584 @node mode_t Values
34585 @unnumberedsubsubsec mode_t Values
34586 @cindex mode_t values, in file-i/o protocol
34588 All values are given in octal representation.
34605 @unnumberedsubsubsec Errno Values
34606 @cindex errno values, in file-i/o protocol
34608 All values are given in decimal representation.
34633 @code{EUNKNOWN} is used as a fallback error value if a host system returns
34634 any error value not in the list of supported error numbers.
34637 @unnumberedsubsubsec Lseek Flags
34638 @cindex lseek flags, in file-i/o protocol
34647 @unnumberedsubsubsec Limits
34648 @cindex limits, in file-i/o protocol
34650 All values are given in decimal representation.
34653 INT_MIN -2147483648
34655 UINT_MAX 4294967295
34656 LONG_MIN -9223372036854775808
34657 LONG_MAX 9223372036854775807
34658 ULONG_MAX 18446744073709551615
34661 @node File-I/O Examples
34662 @subsection File-I/O Examples
34663 @cindex file-i/o examples
34665 Example sequence of a write call, file descriptor 3, buffer is at target
34666 address 0x1234, 6 bytes should be written:
34669 <- @code{Fwrite,3,1234,6}
34670 @emph{request memory read from target}
34673 @emph{return "6 bytes written"}
34677 Example sequence of a read call, file descriptor 3, buffer is at target
34678 address 0x1234, 6 bytes should be read:
34681 <- @code{Fread,3,1234,6}
34682 @emph{request memory write to target}
34683 -> @code{X1234,6:XXXXXX}
34684 @emph{return "6 bytes read"}
34688 Example sequence of a read call, call fails on the host due to invalid
34689 file descriptor (@code{EBADF}):
34692 <- @code{Fread,3,1234,6}
34696 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
34700 <- @code{Fread,3,1234,6}
34705 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
34709 <- @code{Fread,3,1234,6}
34710 -> @code{X1234,6:XXXXXX}
34714 @node Library List Format
34715 @section Library List Format
34716 @cindex library list format, remote protocol
34718 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
34719 same process as your application to manage libraries. In this case,
34720 @value{GDBN} can use the loader's symbol table and normal memory
34721 operations to maintain a list of shared libraries. On other
34722 platforms, the operating system manages loaded libraries.
34723 @value{GDBN} can not retrieve the list of currently loaded libraries
34724 through memory operations, so it uses the @samp{qXfer:libraries:read}
34725 packet (@pxref{qXfer library list read}) instead. The remote stub
34726 queries the target's operating system and reports which libraries
34729 The @samp{qXfer:libraries:read} packet returns an XML document which
34730 lists loaded libraries and their offsets. Each library has an
34731 associated name and one or more segment or section base addresses,
34732 which report where the library was loaded in memory.
34734 For the common case of libraries that are fully linked binaries, the
34735 library should have a list of segments. If the target supports
34736 dynamic linking of a relocatable object file, its library XML element
34737 should instead include a list of allocated sections. The segment or
34738 section bases are start addresses, not relocation offsets; they do not
34739 depend on the library's link-time base addresses.
34741 @value{GDBN} must be linked with the Expat library to support XML
34742 library lists. @xref{Expat}.
34744 A simple memory map, with one loaded library relocated by a single
34745 offset, looks like this:
34749 <library name="/lib/libc.so.6">
34750 <segment address="0x10000000"/>
34755 Another simple memory map, with one loaded library with three
34756 allocated sections (.text, .data, .bss), looks like this:
34760 <library name="sharedlib.o">
34761 <section address="0x10000000"/>
34762 <section address="0x20000000"/>
34763 <section address="0x30000000"/>
34768 The format of a library list is described by this DTD:
34771 <!-- library-list: Root element with versioning -->
34772 <!ELEMENT library-list (library)*>
34773 <!ATTLIST library-list version CDATA #FIXED "1.0">
34774 <!ELEMENT library (segment*, section*)>
34775 <!ATTLIST library name CDATA #REQUIRED>
34776 <!ELEMENT segment EMPTY>
34777 <!ATTLIST segment address CDATA #REQUIRED>
34778 <!ELEMENT section EMPTY>
34779 <!ATTLIST section address CDATA #REQUIRED>
34782 In addition, segments and section descriptors cannot be mixed within a
34783 single library element, and you must supply at least one segment or
34784 section for each library.
34786 @node Memory Map Format
34787 @section Memory Map Format
34788 @cindex memory map format
34790 To be able to write into flash memory, @value{GDBN} needs to obtain a
34791 memory map from the target. This section describes the format of the
34794 The memory map is obtained using the @samp{qXfer:memory-map:read}
34795 (@pxref{qXfer memory map read}) packet and is an XML document that
34796 lists memory regions.
34798 @value{GDBN} must be linked with the Expat library to support XML
34799 memory maps. @xref{Expat}.
34801 The top-level structure of the document is shown below:
34804 <?xml version="1.0"?>
34805 <!DOCTYPE memory-map
34806 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
34807 "http://sourceware.org/gdb/gdb-memory-map.dtd">
34813 Each region can be either:
34818 A region of RAM starting at @var{addr} and extending for @var{length}
34822 <memory type="ram" start="@var{addr}" length="@var{length}"/>
34827 A region of read-only memory:
34830 <memory type="rom" start="@var{addr}" length="@var{length}"/>
34835 A region of flash memory, with erasure blocks @var{blocksize}
34839 <memory type="flash" start="@var{addr}" length="@var{length}">
34840 <property name="blocksize">@var{blocksize}</property>
34846 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
34847 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
34848 packets to write to addresses in such ranges.
34850 The formal DTD for memory map format is given below:
34853 <!-- ................................................... -->
34854 <!-- Memory Map XML DTD ................................ -->
34855 <!-- File: memory-map.dtd .............................. -->
34856 <!-- .................................... .............. -->
34857 <!-- memory-map.dtd -->
34858 <!-- memory-map: Root element with versioning -->
34859 <!ELEMENT memory-map (memory | property)>
34860 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
34861 <!ELEMENT memory (property)>
34862 <!-- memory: Specifies a memory region,
34863 and its type, or device. -->
34864 <!ATTLIST memory type CDATA #REQUIRED
34865 start CDATA #REQUIRED
34866 length CDATA #REQUIRED
34867 device CDATA #IMPLIED>
34868 <!-- property: Generic attribute tag -->
34869 <!ELEMENT property (#PCDATA | property)*>
34870 <!ATTLIST property name CDATA #REQUIRED>
34873 @node Thread List Format
34874 @section Thread List Format
34875 @cindex thread list format
34877 To efficiently update the list of threads and their attributes,
34878 @value{GDBN} issues the @samp{qXfer:threads:read} packet
34879 (@pxref{qXfer threads read}) and obtains the XML document with
34880 the following structure:
34883 <?xml version="1.0"?>
34885 <thread id="id" core="0">
34886 ... description ...
34891 Each @samp{thread} element must have the @samp{id} attribute that
34892 identifies the thread (@pxref{thread-id syntax}). The
34893 @samp{core} attribute, if present, specifies which processor core
34894 the thread was last executing on. The content of the of @samp{thread}
34895 element is interpreted as human-readable auxilliary information.
34897 @include agentexpr.texi
34899 @node Trace File Format
34900 @appendix Trace File Format
34901 @cindex trace file format
34903 The trace file comes in three parts: a header, a textual description
34904 section, and a trace frame section with binary data.
34906 The header has the form @code{\x7fTRACE0\n}. The first byte is
34907 @code{0x7f} so as to indicate that the file contains binary data,
34908 while the @code{0} is a version number that may have different values
34911 The description section consists of multiple lines of @sc{ascii} text
34912 separated by newline characters (@code{0xa}). The lines may include a
34913 variety of optional descriptive or context-setting information, such
34914 as tracepoint definitions or register set size. @value{GDBN} will
34915 ignore any line that it does not recognize. An empty line marks the end
34918 @c FIXME add some specific types of data
34920 The trace frame section consists of a number of consecutive frames.
34921 Each frame begins with a two-byte tracepoint number, followed by a
34922 four-byte size giving the amount of data in the frame. The data in
34923 the frame consists of a number of blocks, each introduced by a
34924 character indicating its type (at least register, memory, and trace
34925 state variable). The data in this section is raw binary, not a
34926 hexadecimal or other encoding; its endianness matches the target's
34929 @c FIXME bi-arch may require endianness/arch info in description section
34932 @item R @var{bytes}
34933 Register block. The number and ordering of bytes matches that of a
34934 @code{g} packet in the remote protocol. Note that these are the
34935 actual bytes, in target order and @value{GDBN} register order, not a
34936 hexadecimal encoding.
34938 @item M @var{address} @var{length} @var{bytes}...
34939 Memory block. This is a contiguous block of memory, at the 8-byte
34940 address @var{address}, with a 2-byte length @var{length}, followed by
34941 @var{length} bytes.
34943 @item V @var{number} @var{value}
34944 Trace state variable block. This records the 8-byte signed value
34945 @var{value} of trace state variable numbered @var{number}.
34949 Future enhancements of the trace file format may include additional types
34952 @node Target Descriptions
34953 @appendix Target Descriptions
34954 @cindex target descriptions
34956 @strong{Warning:} target descriptions are still under active development,
34957 and the contents and format may change between @value{GDBN} releases.
34958 The format is expected to stabilize in the future.
34960 One of the challenges of using @value{GDBN} to debug embedded systems
34961 is that there are so many minor variants of each processor
34962 architecture in use. It is common practice for vendors to start with
34963 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
34964 and then make changes to adapt it to a particular market niche. Some
34965 architectures have hundreds of variants, available from dozens of
34966 vendors. This leads to a number of problems:
34970 With so many different customized processors, it is difficult for
34971 the @value{GDBN} maintainers to keep up with the changes.
34973 Since individual variants may have short lifetimes or limited
34974 audiences, it may not be worthwhile to carry information about every
34975 variant in the @value{GDBN} source tree.
34977 When @value{GDBN} does support the architecture of the embedded system
34978 at hand, the task of finding the correct architecture name to give the
34979 @command{set architecture} command can be error-prone.
34982 To address these problems, the @value{GDBN} remote protocol allows a
34983 target system to not only identify itself to @value{GDBN}, but to
34984 actually describe its own features. This lets @value{GDBN} support
34985 processor variants it has never seen before --- to the extent that the
34986 descriptions are accurate, and that @value{GDBN} understands them.
34988 @value{GDBN} must be linked with the Expat library to support XML
34989 target descriptions. @xref{Expat}.
34992 * Retrieving Descriptions:: How descriptions are fetched from a target.
34993 * Target Description Format:: The contents of a target description.
34994 * Predefined Target Types:: Standard types available for target
34996 * Standard Target Features:: Features @value{GDBN} knows about.
34999 @node Retrieving Descriptions
35000 @section Retrieving Descriptions
35002 Target descriptions can be read from the target automatically, or
35003 specified by the user manually. The default behavior is to read the
35004 description from the target. @value{GDBN} retrieves it via the remote
35005 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
35006 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
35007 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
35008 XML document, of the form described in @ref{Target Description
35011 Alternatively, you can specify a file to read for the target description.
35012 If a file is set, the target will not be queried. The commands to
35013 specify a file are:
35016 @cindex set tdesc filename
35017 @item set tdesc filename @var{path}
35018 Read the target description from @var{path}.
35020 @cindex unset tdesc filename
35021 @item unset tdesc filename
35022 Do not read the XML target description from a file. @value{GDBN}
35023 will use the description supplied by the current target.
35025 @cindex show tdesc filename
35026 @item show tdesc filename
35027 Show the filename to read for a target description, if any.
35031 @node Target Description Format
35032 @section Target Description Format
35033 @cindex target descriptions, XML format
35035 A target description annex is an @uref{http://www.w3.org/XML/, XML}
35036 document which complies with the Document Type Definition provided in
35037 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
35038 means you can use generally available tools like @command{xmllint} to
35039 check that your feature descriptions are well-formed and valid.
35040 However, to help people unfamiliar with XML write descriptions for
35041 their targets, we also describe the grammar here.
35043 Target descriptions can identify the architecture of the remote target
35044 and (for some architectures) provide information about custom register
35045 sets. They can also identify the OS ABI of the remote target.
35046 @value{GDBN} can use this information to autoconfigure for your
35047 target, or to warn you if you connect to an unsupported target.
35049 Here is a simple target description:
35052 <target version="1.0">
35053 <architecture>i386:x86-64</architecture>
35058 This minimal description only says that the target uses
35059 the x86-64 architecture.
35061 A target description has the following overall form, with [ ] marking
35062 optional elements and @dots{} marking repeatable elements. The elements
35063 are explained further below.
35066 <?xml version="1.0"?>
35067 <!DOCTYPE target SYSTEM "gdb-target.dtd">
35068 <target version="1.0">
35069 @r{[}@var{architecture}@r{]}
35070 @r{[}@var{osabi}@r{]}
35071 @r{[}@var{compatible}@r{]}
35072 @r{[}@var{feature}@dots{}@r{]}
35077 The description is generally insensitive to whitespace and line
35078 breaks, under the usual common-sense rules. The XML version
35079 declaration and document type declaration can generally be omitted
35080 (@value{GDBN} does not require them), but specifying them may be
35081 useful for XML validation tools. The @samp{version} attribute for
35082 @samp{<target>} may also be omitted, but we recommend
35083 including it; if future versions of @value{GDBN} use an incompatible
35084 revision of @file{gdb-target.dtd}, they will detect and report
35085 the version mismatch.
35087 @subsection Inclusion
35088 @cindex target descriptions, inclusion
35091 @cindex <xi:include>
35094 It can sometimes be valuable to split a target description up into
35095 several different annexes, either for organizational purposes, or to
35096 share files between different possible target descriptions. You can
35097 divide a description into multiple files by replacing any element of
35098 the target description with an inclusion directive of the form:
35101 <xi:include href="@var{document}"/>
35105 When @value{GDBN} encounters an element of this form, it will retrieve
35106 the named XML @var{document}, and replace the inclusion directive with
35107 the contents of that document. If the current description was read
35108 using @samp{qXfer}, then so will be the included document;
35109 @var{document} will be interpreted as the name of an annex. If the
35110 current description was read from a file, @value{GDBN} will look for
35111 @var{document} as a file in the same directory where it found the
35112 original description.
35114 @subsection Architecture
35115 @cindex <architecture>
35117 An @samp{<architecture>} element has this form:
35120 <architecture>@var{arch}</architecture>
35123 @var{arch} is one of the architectures from the set accepted by
35124 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35127 @cindex @code{<osabi>}
35129 This optional field was introduced in @value{GDBN} version 7.0.
35130 Previous versions of @value{GDBN} ignore it.
35132 An @samp{<osabi>} element has this form:
35135 <osabi>@var{abi-name}</osabi>
35138 @var{abi-name} is an OS ABI name from the same selection accepted by
35139 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
35141 @subsection Compatible Architecture
35142 @cindex @code{<compatible>}
35144 This optional field was introduced in @value{GDBN} version 7.0.
35145 Previous versions of @value{GDBN} ignore it.
35147 A @samp{<compatible>} element has this form:
35150 <compatible>@var{arch}</compatible>
35153 @var{arch} is one of the architectures from the set accepted by
35154 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35156 A @samp{<compatible>} element is used to specify that the target
35157 is able to run binaries in some other than the main target architecture
35158 given by the @samp{<architecture>} element. For example, on the
35159 Cell Broadband Engine, the main architecture is @code{powerpc:common}
35160 or @code{powerpc:common64}, but the system is able to run binaries
35161 in the @code{spu} architecture as well. The way to describe this
35162 capability with @samp{<compatible>} is as follows:
35165 <architecture>powerpc:common</architecture>
35166 <compatible>spu</compatible>
35169 @subsection Features
35172 Each @samp{<feature>} describes some logical portion of the target
35173 system. Features are currently used to describe available CPU
35174 registers and the types of their contents. A @samp{<feature>} element
35178 <feature name="@var{name}">
35179 @r{[}@var{type}@dots{}@r{]}
35185 Each feature's name should be unique within the description. The name
35186 of a feature does not matter unless @value{GDBN} has some special
35187 knowledge of the contents of that feature; if it does, the feature
35188 should have its standard name. @xref{Standard Target Features}.
35192 Any register's value is a collection of bits which @value{GDBN} must
35193 interpret. The default interpretation is a two's complement integer,
35194 but other types can be requested by name in the register description.
35195 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
35196 Target Types}), and the description can define additional composite types.
35198 Each type element must have an @samp{id} attribute, which gives
35199 a unique (within the containing @samp{<feature>}) name to the type.
35200 Types must be defined before they are used.
35203 Some targets offer vector registers, which can be treated as arrays
35204 of scalar elements. These types are written as @samp{<vector>} elements,
35205 specifying the array element type, @var{type}, and the number of elements,
35209 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
35213 If a register's value is usefully viewed in multiple ways, define it
35214 with a union type containing the useful representations. The
35215 @samp{<union>} element contains one or more @samp{<field>} elements,
35216 each of which has a @var{name} and a @var{type}:
35219 <union id="@var{id}">
35220 <field name="@var{name}" type="@var{type}"/>
35226 If a register's value is composed from several separate values, define
35227 it with a structure type. There are two forms of the @samp{<struct>}
35228 element; a @samp{<struct>} element must either contain only bitfields
35229 or contain no bitfields. If the structure contains only bitfields,
35230 its total size in bytes must be specified, each bitfield must have an
35231 explicit start and end, and bitfields are automatically assigned an
35232 integer type. The field's @var{start} should be less than or
35233 equal to its @var{end}, and zero represents the least significant bit.
35236 <struct id="@var{id}" size="@var{size}">
35237 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35242 If the structure contains no bitfields, then each field has an
35243 explicit type, and no implicit padding is added.
35246 <struct id="@var{id}">
35247 <field name="@var{name}" type="@var{type}"/>
35253 If a register's value is a series of single-bit flags, define it with
35254 a flags type. The @samp{<flags>} element has an explicit @var{size}
35255 and contains one or more @samp{<field>} elements. Each field has a
35256 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
35260 <flags id="@var{id}" size="@var{size}">
35261 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35266 @subsection Registers
35269 Each register is represented as an element with this form:
35272 <reg name="@var{name}"
35273 bitsize="@var{size}"
35274 @r{[}regnum="@var{num}"@r{]}
35275 @r{[}save-restore="@var{save-restore}"@r{]}
35276 @r{[}type="@var{type}"@r{]}
35277 @r{[}group="@var{group}"@r{]}/>
35281 The components are as follows:
35286 The register's name; it must be unique within the target description.
35289 The register's size, in bits.
35292 The register's number. If omitted, a register's number is one greater
35293 than that of the previous register (either in the current feature or in
35294 a preceeding feature); the first register in the target description
35295 defaults to zero. This register number is used to read or write
35296 the register; e.g.@: it is used in the remote @code{p} and @code{P}
35297 packets, and registers appear in the @code{g} and @code{G} packets
35298 in order of increasing register number.
35301 Whether the register should be preserved across inferior function
35302 calls; this must be either @code{yes} or @code{no}. The default is
35303 @code{yes}, which is appropriate for most registers except for
35304 some system control registers; this is not related to the target's
35308 The type of the register. @var{type} may be a predefined type, a type
35309 defined in the current feature, or one of the special types @code{int}
35310 and @code{float}. @code{int} is an integer type of the correct size
35311 for @var{bitsize}, and @code{float} is a floating point type (in the
35312 architecture's normal floating point format) of the correct size for
35313 @var{bitsize}. The default is @code{int}.
35316 The register group to which this register belongs. @var{group} must
35317 be either @code{general}, @code{float}, or @code{vector}. If no
35318 @var{group} is specified, @value{GDBN} will not display the register
35319 in @code{info registers}.
35323 @node Predefined Target Types
35324 @section Predefined Target Types
35325 @cindex target descriptions, predefined types
35327 Type definitions in the self-description can build up composite types
35328 from basic building blocks, but can not define fundamental types. Instead,
35329 standard identifiers are provided by @value{GDBN} for the fundamental
35330 types. The currently supported types are:
35339 Signed integer types holding the specified number of bits.
35346 Unsigned integer types holding the specified number of bits.
35350 Pointers to unspecified code and data. The program counter and
35351 any dedicated return address register may be marked as code
35352 pointers; printing a code pointer converts it into a symbolic
35353 address. The stack pointer and any dedicated address registers
35354 may be marked as data pointers.
35357 Single precision IEEE floating point.
35360 Double precision IEEE floating point.
35363 The 12-byte extended precision format used by ARM FPA registers.
35366 The 10-byte extended precision format used by x87 registers.
35369 32bit @sc{eflags} register used by x86.
35372 32bit @sc{mxcsr} register used by x86.
35376 @node Standard Target Features
35377 @section Standard Target Features
35378 @cindex target descriptions, standard features
35380 A target description must contain either no registers or all the
35381 target's registers. If the description contains no registers, then
35382 @value{GDBN} will assume a default register layout, selected based on
35383 the architecture. If the description contains any registers, the
35384 default layout will not be used; the standard registers must be
35385 described in the target description, in such a way that @value{GDBN}
35386 can recognize them.
35388 This is accomplished by giving specific names to feature elements
35389 which contain standard registers. @value{GDBN} will look for features
35390 with those names and verify that they contain the expected registers;
35391 if any known feature is missing required registers, or if any required
35392 feature is missing, @value{GDBN} will reject the target
35393 description. You can add additional registers to any of the
35394 standard features --- @value{GDBN} will display them just as if
35395 they were added to an unrecognized feature.
35397 This section lists the known features and their expected contents.
35398 Sample XML documents for these features are included in the
35399 @value{GDBN} source tree, in the directory @file{gdb/features}.
35401 Names recognized by @value{GDBN} should include the name of the
35402 company or organization which selected the name, and the overall
35403 architecture to which the feature applies; so e.g.@: the feature
35404 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
35406 The names of registers are not case sensitive for the purpose
35407 of recognizing standard features, but @value{GDBN} will only display
35408 registers using the capitalization used in the description.
35415 * PowerPC Features::
35420 @subsection ARM Features
35421 @cindex target descriptions, ARM features
35423 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
35424 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
35425 @samp{lr}, @samp{pc}, and @samp{cpsr}.
35427 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
35428 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
35430 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
35431 it should contain at least registers @samp{wR0} through @samp{wR15} and
35432 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
35433 @samp{wCSSF}, and @samp{wCASF} registers are optional.
35435 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
35436 should contain at least registers @samp{d0} through @samp{d15}. If
35437 they are present, @samp{d16} through @samp{d31} should also be included.
35438 @value{GDBN} will synthesize the single-precision registers from
35439 halves of the double-precision registers.
35441 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
35442 need to contain registers; it instructs @value{GDBN} to display the
35443 VFP double-precision registers as vectors and to synthesize the
35444 quad-precision registers from pairs of double-precision registers.
35445 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
35446 be present and include 32 double-precision registers.
35448 @node i386 Features
35449 @subsection i386 Features
35450 @cindex target descriptions, i386 features
35452 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
35453 targets. It should describe the following registers:
35457 @samp{eax} through @samp{edi} plus @samp{eip} for i386
35459 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
35461 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
35462 @samp{fs}, @samp{gs}
35464 @samp{st0} through @samp{st7}
35466 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
35467 @samp{foseg}, @samp{fooff} and @samp{fop}
35470 The register sets may be different, depending on the target.
35472 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
35473 describe registers:
35477 @samp{xmm0} through @samp{xmm7} for i386
35479 @samp{xmm0} through @samp{xmm15} for amd64
35484 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
35485 @samp{org.gnu.gdb.i386.sse} feature. It should
35486 describe the upper 128 bits of @sc{ymm} registers:
35490 @samp{ymm0h} through @samp{ymm7h} for i386
35492 @samp{ymm0h} through @samp{ymm15h} for amd64
35496 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
35497 describe a single register, @samp{orig_eax}.
35499 @node MIPS Features
35500 @subsection MIPS Features
35501 @cindex target descriptions, MIPS features
35503 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
35504 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
35505 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
35508 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
35509 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
35510 registers. They may be 32-bit or 64-bit depending on the target.
35512 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
35513 it may be optional in a future version of @value{GDBN}. It should
35514 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
35515 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
35517 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
35518 contain a single register, @samp{restart}, which is used by the
35519 Linux kernel to control restartable syscalls.
35521 @node M68K Features
35522 @subsection M68K Features
35523 @cindex target descriptions, M68K features
35526 @item @samp{org.gnu.gdb.m68k.core}
35527 @itemx @samp{org.gnu.gdb.coldfire.core}
35528 @itemx @samp{org.gnu.gdb.fido.core}
35529 One of those features must be always present.
35530 The feature that is present determines which flavor of m68k is
35531 used. The feature that is present should contain registers
35532 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
35533 @samp{sp}, @samp{ps} and @samp{pc}.
35535 @item @samp{org.gnu.gdb.coldfire.fp}
35536 This feature is optional. If present, it should contain registers
35537 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
35541 @node PowerPC Features
35542 @subsection PowerPC Features
35543 @cindex target descriptions, PowerPC features
35545 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
35546 targets. It should contain registers @samp{r0} through @samp{r31},
35547 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
35548 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
35550 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
35551 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
35553 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
35554 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
35557 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
35558 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
35559 will combine these registers with the floating point registers
35560 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
35561 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
35562 through @samp{vs63}, the set of vector registers for POWER7.
35564 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
35565 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
35566 @samp{spefscr}. SPE targets should provide 32-bit registers in
35567 @samp{org.gnu.gdb.power.core} and provide the upper halves in
35568 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
35569 these to present registers @samp{ev0} through @samp{ev31} to the
35572 @node Operating System Information
35573 @appendix Operating System Information
35574 @cindex operating system information
35580 Users of @value{GDBN} often wish to obtain information about the state of
35581 the operating system running on the target---for example the list of
35582 processes, or the list of open files. This section describes the
35583 mechanism that makes it possible. This mechanism is similar to the
35584 target features mechanism (@pxref{Target Descriptions}), but focuses
35585 on a different aspect of target.
35587 Operating system information is retrived from the target via the
35588 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
35589 read}). The object name in the request should be @samp{osdata}, and
35590 the @var{annex} identifies the data to be fetched.
35593 @appendixsection Process list
35594 @cindex operating system information, process list
35596 When requesting the process list, the @var{annex} field in the
35597 @samp{qXfer} request should be @samp{processes}. The returned data is
35598 an XML document. The formal syntax of this document is defined in
35599 @file{gdb/features/osdata.dtd}.
35601 An example document is:
35604 <?xml version="1.0"?>
35605 <!DOCTYPE target SYSTEM "osdata.dtd">
35606 <osdata type="processes">
35608 <column name="pid">1</column>
35609 <column name="user">root</column>
35610 <column name="command">/sbin/init</column>
35611 <column name="cores">1,2,3</column>
35616 Each item should include a column whose name is @samp{pid}. The value
35617 of that column should identify the process on the target. The
35618 @samp{user} and @samp{command} columns are optional, and will be
35619 displayed by @value{GDBN}. The @samp{cores} column, if present,
35620 should contain a comma-separated list of cores that this process
35621 is running on. Target may provide additional columns,
35622 which @value{GDBN} currently ignores.
35626 @node GNU Free Documentation License
35627 @appendix GNU Free Documentation License
35636 % I think something like @colophon should be in texinfo. In the
35638 \long\def\colophon{\hbox to0pt{}\vfill
35639 \centerline{The body of this manual is set in}
35640 \centerline{\fontname\tenrm,}
35641 \centerline{with headings in {\bf\fontname\tenbf}}
35642 \centerline{and examples in {\tt\fontname\tentt}.}
35643 \centerline{{\it\fontname\tenit\/},}
35644 \centerline{{\bf\fontname\tenbf}, and}
35645 \centerline{{\sl\fontname\tensl\/}}
35646 \centerline{are used for emphasis.}\vfill}
35648 % Blame: doc@cygnus.com, 1991.